WorldWideScience

Sample records for brazed plate heat

  1. Investigation of Brazed Plate Heat Exchangers With Variable Chevron Angles

    OpenAIRE

    S. Muthuraman

    2013-01-01

    - Experiments to measure the condensation heat transfer coefficient and the pressure drop in brazed plate heat exchangers (BPHEs) were performed with the refrigerants R410A and R22. Brazed plate heat exchangers with different chevron angles of 45°, 35°, and 20° were used. Varying the mass flux, the condensation temperature, and the vapor quality of the refrigerant, we measured the condensation heat transfer coefficient and the pressure drops. Both the heat transfer coefficient and the pressur...

  2. Investigation of Brazed Plate Heat Exchangers With Variable Chevron Angles

    Directory of Open Access Journals (Sweden)

    S. Muthuraman

    2013-08-01

    Full Text Available - Experiments to measure the condensation heat transfer coefficient and the pressure drop in brazed plate heat exchangers (BPHEs were performed with the refrigerants R410A and R22. Brazed plate heat exchangers with different chevron angles of 45°, 35°, and 20° were used. Varying the mass flux, the condensation temperature, and the vapor quality of the refrigerant, we measured the condensation heat transfer coefficient and the pressure drops. Both the heat transfer coefficient and the pressure drop increased proportionally with the mass flux and the vapor quality and inversely with the condensation temperature and the chevron angle.

  3. The characteristics of brazed plate heat exchangers with different chevron angles

    OpenAIRE

    M. Amala Justus Selvam; Senthil Kumar P.; S. Muthuraman

    2009-01-01

    Experiments to measure the condensation heat transfer coefficient and the pressure drop in brazed plate heat exchangers (BPHEs) were performed with the refrigerants R410A and R22. Brazed plate heat exchangers with different chevron angles of 45_, 35_, and 20_ were used. Varying the mass flux, the condensation temperature, and the vapor quality of the refrigerant, we measured the condensation heat transfer coefficient and the pressure drops. Both the heat transfer coefficient and the pressure ...

  4. Oil Circulation Effects on Evaporation Heat Transfer in Brazed Plate Heat Exchanger using R134A

    OpenAIRE

    Jang, Jaekyoo; Chang, Youngsoo; Kang, Byungha

    2012-01-01

    Experimental study was performed for oil circulation effects on evaporation heat transfer in the brazed type plate heat exchangers using R134A. In this study, distribution device was installed to ensure uniform flow distribution in the refrigerant flow passage, which enhances heat transfer performance of plate type heat exchanger. Tests were conducted for three evaporation temperature; 33℃, 37℃, and 41℃ and several oil circulation conditions. The nominal conditions of refrigerant are as follo...

  5. Brazing with plated alloys

    International Nuclear Information System (INIS)

    The use of braze alloy preforms on complex geometry components is at times a very difficult task requiring extensive handling of the parts or even tack welding of the preform to ensure that it is held in place. One method of overcoming these difficulties is the use of plated braze alloys (i.e., filler metals) applied directly to the braze region. Plating helps to avoid the potential for contamination resulting from handling and also ensures that the braze alloy is located properly. Examples are discussed in which an electroplated silver-copper alloy is used as an alternative to the BAg8 preforms and electroless nickel is used as a replacement for an amorphous Ni-P braze alloy foil. A toroidal cooling plate with helical flow channels was fabricated from oxygen-free high conductivity (OFHC) and brazed using the electroplated silver-copper alloy. The silver-copper braze alloy was applied to the copper substrate in a laminated fashion of alternating layers of silver and copper, which in combination approximated the eutectic composition (72% Ag-28% Cu by weight). Examination of the brazed assemblies indicated that in both cases the advantages of using plated braze alloys are numerous. These advantages include decreased labor, improved cleanliness and exactness of braze alloy placement. The primary disadvantage was an increased tendency for solidification defects presumably resulting from contaminants in the plating baths. This last observation is presently being examined in greater detail. The end results is that the assemblies brazed with the plated alloys were acceptable for the intended application and that the use of plating facilitated the successful assembly of these components

  6. Brazing open cell reticulated copper foam to stainless steel tubing with vacuum furnace brazed gold/indium alloy plating

    Science.gov (United States)

    Howard, Stanley R.; Korinko, Paul S.

    2008-05-27

    A method of fabricating a heat exchanger includes brush electroplating plated layers for a brazing alloy onto a stainless steel tube in thin layers, over a nickel strike having a 1.3 .mu.m thickness. The resultant Au-18 In composition may be applied as a first layer of indium, 1.47 .mu.m thick, and a second layer of gold, 2.54 .mu.m thick. The order of plating helps control brazing erosion. Excessive amounts of brazing material are avoided by controlling the electroplating process. The reticulated copper foam rings are interference fit to the stainless steel tube, and in contact with the plated layers. The copper foam rings, the plated layers for brazing alloy, and the stainless steel tube are heated and cooled in a vacuum furnace at controlled rates, forming a bond of the copper foam rings to the stainless steel tube that improves heat transfer between the tube and the copper foam.

  7. Condensation heat transfer and pressure drop of R-134a saturated vapour inside a brazed compact plate fin heat exchanger with serrated fin

    Science.gov (United States)

    Ramana Murthy, K. V.; Ranganayakulu, C.; Ashok Babu, T. P.

    2016-05-01

    This paper presents the experimental heat transfer coefficient and pressure drop measured during R-134a saturated vapour condensation inside a small brazed compact plate fin heat exchanger with serrated fin surface. The effects of saturation temperature (pressure), refrigerant mass flux, refrigerant heat flux, effect of fin surface characteristics and fluid properties are investigated. The average condensation heat transfer coefficients and frictional pressure drops were determined experimentally for refrigerant R-134a at five different saturated temperatures (34, 38, 40, 42 and 44 °C). A transition point between gravity controlled and forced convection condensation has been found for a refrigerant mass flux around 22 kg/m2s. In the forced convection condensation region, the heat transfer coefficients show a three times increase and 1.5 times increase in frictional pressure drop for a doubling of the refrigerant mass flux. The heat transfer coefficients show weak sensitivity to saturation temperature (Pressure) and great sensitivity to refrigerant mass flux and fluid properties. The frictional pressure drop shows a linear dependence on the kinetic energy per unit volume of the refrigerant flow. Correlations are provided for the measured heat transfer coefficients and frictional pressure drops.

  8. New plates for different types of plate heat exchangers

    OpenAIRE

    Fernandes, Carla S.; Dias, Ricardo P.; João M. Maia

    2008-01-01

    The first patent for a plate heat exchanger was granted in 1878 to Albretch Dracke, a German inventor. The commercial embodiment of these equipments has become available in 1923. However, the plate heat exchanger development race began in the 1930’s and these gasketed plate and frame heat exchangers were mainly used as pasteurizers (e.g. for milk and beer). Industrial plate heat exchangers were introduced in the 1950’s and initially they were converted dairy models. Brazed plate heat exchange...

  9. Brazing

    International Nuclear Information System (INIS)

    This report is a compilation of published literature on high temperature brazing covering the period 1973-1978. The references are listed alphabetically with regard to the base material or combination of base materials to be brazed. Trade names are treated as base materials. The report contains approximately 1500 references, of which 300 are to patents

  10. Induction Brazing

    DEFF Research Database (Denmark)

    Henningsen, Poul

    Induction brazing is a fast and appropriate method for industrial joining of complex geometries and metal combinations. In all types of brazing processes it is important to heat the joint interface of the two materials to the same, high temperature. If one of the specimens is warmer than the other...... the work piece materials has large influence on the heating time and temperature distribution in induction heating. In order to ensure high and uniform temperature distribution near the interface of a joint between dissimilar materials the precise coil geometry and position is of great importance. The...... present report presents a combined numerical and experimental method for determination of appropriate/optimiged coil geometry and position in induction brazing tube-to-plate joints of different ratios between tube and plate thickness and different combinations of the materials stainless steel, brass and...

  11. Novel high chromium containing braze filler metals for heat exchanger applications

    Energy Technology Data Exchange (ETDEWEB)

    Rangaswamy, S.; Fortuna, D. [Sulzer Metco, Troy (United States)

    2007-07-01

    A new family of boron-free, high chromium containing braze filler metal compositions were developed (Amdry 105, Amdry 108, Amdry 805). Filler metal properties including metallurgical phases, melting range, flow, corrosion resistance and high temperature oxidation resistance are reported. Additionally, the technical and economical advantages of using these new filler metals in fabricating flat plate type of heat exchangers and metallic catalytic converters is discussed. (orig.)

  12. Microstructure and Mechanical Properties of Plasma Arc Brazed AISI 304L Stainless Steel and Galvanized Steel Plates

    Science.gov (United States)

    Jin, Yajuan; Li, Ruifeng; Yu, Zhishui; Wang, Yu

    2016-04-01

    Plasma arc brazing is used to join the AISI 304L stainless steel and galvanized steel plate butt joints with the CuSi3Mn1 filler wire. The effect of parameters on weld surface appearance, interfacial microstructure, and composition distribution in the joint was studied. The microhardness and mechanical tests were conducted to determine the mechanical properties of the welded specimens. The results indicated that good appearance, bead shape, and sufficient metallurgical bonding could be obtained when the brazing process was performed with a wire feeding speed of 0.8 m/min, plasma gas flow rate of 3.0 l/min, welding current of 100 A, and welding speed of 27 cm/min. During plasma arc brazing process, the top corner of the stainless steel and galvanized steel plate were heated and melted, and the melted quantity of stainless steel was much more than that of the galvanized steel due to the thermal conductivity coefficient difference between the dissimilar materials. The microhardness test results shows that the microhardness value gradually increased from the side of the galvanized steel to the stainless steel in the joint, and it is good for improving the mechanical properties of joint. The tensile strength was a little higher than that of the brazing filler, and the fracture position of weld joint was at the base metal of galvanized steel plate.

  13. Effect of Heat Treatment on High Temperature Stress Rupture Strength of Brazing Seam for Nickel-base Superalloy

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In order to enhance the high-temperature stress rupture strength of brazing seam by heat treatment, it was diffusion treated, then solution heat treated, and finally aging treated. The microstructure of brazing seam especially morphology of phase and boride was observed and the strength of brazing seam was measured in this process. The results show that heat treatment can enhance high-temperature stress rupture strength by improving the microstructure of brazing seam. The strength of brazing seam after solution heat treatment decreases in comparison with that only after diffusion treatment while aging treatment after solution heat treatment increases the strength of brazing seam.

  14. Simulation on Thermal Integrity of the Fin/Tube Brazed Joint of Heat Exchangers

    Institute of Scientific and Technical Information of China (English)

    Yiyu QIAN; Feng GAO; Fengjiang WANG; Hui ZHAO

    2003-01-01

    In the applications of heat exchangers, the fin efficiency of heat transfer is the key issue. Thermal distribution withinthe brazed joints in heat exchanger under loading conditions is investigated in this paper. Simulated results showedthat the therma

  15. Reversible brazing process

    Science.gov (United States)

    Pierce, Jim D.; Stephens, John J.; Walker, Charles A.

    1999-01-01

    A method of reversibly brazing surfaces together. An interface is affixed to each surface. The interfaces can be affixed by processes such as mechanical joining, welding, or brazing. The two interfaces are then brazed together using a brazing process that does not defeat the surface to interface joint. Interfaces of materials such as Ni-200 can be affixed to metallic surfaces by welding or by brazing with a first braze alloy. The Ni-200 interfaces can then be brazed together using a second braze alloy. The second braze alloy can be chosen so that it minimally alters the properties of the interfaces to allow multiple braze, heat and disassemble, rebraze cycles.

  16. Development and heat load experiments of graphite brazed to stainless steel for the first wall structure of FER

    International Nuclear Information System (INIS)

    A guard limiter concept with graphite brazed to a stainless steel base plate has been proposed in FER. The bonding of graphite and stainless steel was successfully done by vacuum brazing with an interlayer material of Mo or Cu. Mechanical strengths were measured by tensile and shear tests. Fatigue test up to approximately 107 cycles were done. Heat load experiments were performed with electron beam equipment. Brazed materials with a Mo interlayer were subjected to a heat load up to 60 MJ/m2 (6 kJ/cm2). No complete failures were observed in every condition, but cracks were generated by heat loads greater than 40 MJ/m2 (4 kJ/cm2). The failures were generated in graphite near to the interface. Mechanical strength and thermal shock resistance were improved by the change from 1 to 3 mm in thickness of Mo interlayer. Residual stresses due to brazing and cool-down were analyzed with an FEM code, and the results were compared with strain measurements on the test specimen. A comparison study on interlayer materials is continuing, and heat load cycle tests are now underway for 10 MJ/m2 (1 kJ/cm2), which is a target value based on the FER design. (orig.)

  17. Effect of holding time on vacuum brazing for a stainless steel plate-fin structure

    International Nuclear Information System (INIS)

    This paper presents a vacuum brazing of 304 stainless steel plate-fin structures with nickel-based BNi-2 filler metal. The effect of brazing holding time on tensile strength and microstructure has been investigated, aiming to obtain the optimal brazing holding time. The microstructure in brazing joint consists of diffusion-affected zone (DAZ), interface reaction zone (IRZ), isothermally solidified zone (ISZ) and athermally solidified zone (ASZ). The structure in the fillet is composed of solid solution, nickel silicon, nickel boron compound and a mixture with nickel silicon and nickel boron. The tensile strength increases along with the increase of holding time, but decreases when the holding time is over 25 min. A maximum tensile strength of 65.1 MPa is obtained with 25 min holding time. Too short holding time will make boron diffuse insufficiently and generate a great deal of brittle boride components, and too long holding time will make the base metal dissolve into the filler metal excessively and creates more corrosion voids.

  18. Plate heat exchanger

    International Nuclear Information System (INIS)

    In a plate heat exchanger required to handle corrosive, toxic or radioactive fluids, wherein each plate has a peripheral recess or like formation adapted for receiving an elastomeric gasket, the plates are welded together in pairs by the method comprising the steps of inserting into the gasket recess of a first plate of said pair a metal packing piece and welding the second place (e.g. by a laser or electron beam weld running along the base of the recess) superimposing a second plate on to the first in contact with the packing piece and welding the second plate to the packing piece (e.g. by a laser or electron beam weld). The packing piece may be of hollow or solid cross section and is preferably of the same material (e.g. titanium or stainless steel) as the plates. In use a service fluid in heat exchange with the said corrosive etc. fluid is confined by peripheral and normally elastomeric gaskets. (author)

  19. The Integration of Vacuum Brazing into Heat Treatment - A Progressive Combined Process

    Institute of Scientific and Technical Information of China (English)

    Ingo Reinkensmeier; Henkjan Buursen

    2004-01-01

    The continuous constructive challenge to improve the functionality and efficiency of components always results in higher demands on production engineering, against the background of the generally increasing cost pressure. In many cases, you will just succeed in producing competitive and innovative products by combining and coupling of different procedures to an independent (hybrid) technology. The use of hybrid procedures for metal joining and heat treatment of metallic materials finds more and more industrial fields of application. Modern vacuum lines with integrated pressurized gas quenching are considered high-performance and flexible means of production for brazing and heat treatment tasks as well in the turbine industry as in the mould making and tool manufacturing industry. In doing so, the heat treatment is coupled with the brazing cycle in a combined process so that the brazing temperatures and soak times are adapted to the necessary temperatures and times for solution heat treatment and austeniting. This user-oriented article describes on the one hand examples of brazing of turbine components, but above all the practical experience from the plastics processing industry, where the requirement for a high-efficient cooling of injection moulding dies gains more and more importance.The combined procedure "Vacuum Brazing and Hardening" offers plenty of possibilities to produce mould inserts with an efficient tempering system in an economic way.

  20. Plate heat exchanger

    International Nuclear Information System (INIS)

    The plate exchanger described includes a series of individual modules joined together, communicating in pairs to delimit two flow circuits separated by two fluids mutually exchanging calories. Each module includes at least one flat frame around a central cavity, at least two apertures made in the frame respectively for the inlet and oulet of the fluids crossing the cavity and at least one opening in the frame for the fluids to pass to a neighbouring module. The frames of the modules form a stack plane upon plane and are isolated by a thin leak-tight sheet parallel to the plane of the frames and separating the fluid substances in two superimposed frames. The heat transfer between these fluids occurs through this thin sheet from one module to the next in the stack

  1. Thermoelastic bending of locally heated composite plate

    OpenAIRE

    Жидик, Уляна

    2013-01-01

    The dynamic behavior of composite plates to rapid heating is investigated. A closed form solutions are presented for simply supported rectangular cross-ply and angle-ply laminated plates. Numerical results are finally presented and discussed.

  2. Lighting system with heat distribution face plate

    Energy Technology Data Exchange (ETDEWEB)

    Arik, Mehmet; Weaver, Stanton Earl; Stecher, Thomas Elliot; Kuenzler, Glenn Howard; Wolfe, Jr., Charles Franklin; Li, Ri

    2013-09-10

    Lighting systems having a light source and a thermal management system are provided. The thermal management system includes synthetic jet devices, a heat sink and a heat distribution face plate. The synthetic jet devices are arranged in parallel to one and other and are configured to actively cool the lighting system. The heat distribution face plate is configured to radially transfer heat from the light source into the ambient air.

  3. A Review on Heat Transfer Improvent of Plate Heat Exchanger

    OpenAIRE

    Abhishek Nandan; Gurpreet Singh Sokhal

    2015-01-01

    Plate heat exchanger has found a wide range of application in various industries like food industries, chemical industries, power plants etc. It reduces the wastage of energy and improves the overall efficiency of the system. Hence, it must be designed to obtain the maximum heat transfer possible. This paper is presented in order to study the various theories and results given over the improvement of heat transfer performance in a plate heat exchanger. However, there is still a la...

  4. Induction brazing of complex joints

    DEFF Research Database (Denmark)

    Henningsen, Poul; Zhang, Wenqi; Bay, Niels

    2003-01-01

    Induction brazing is a fast and appropriate method for industrial joining of complex geometries and metal combinations. In all types of brazing processes it is important to heat the joint interface of the two materials to the same, high temperature. If one of the specimens is warmer than the other......, or if the hottest area is located outside the joint interface, a number of defects may appear: the braze metal may flow away from the joint, the flux may burn off, poor binding of the braze metal may appear or the braze metal may be overheated. Joint geometry as well as electro-magnetic properties of...... the work piece materials has large influence on the heating time and temperature distribution in induction heating. In order to ensure high and uniform temperature distribution near the interface of a joint between dissimilar materials the precise coil geometry and position is of great importance. The...

  5. Response to high heat fluxes and metallurgical examination of a brazed carbon-fiber-composite/refractory-metal divertor mock-up

    International Nuclear Information System (INIS)

    As a feasibility-study an actively cooled divertor mock-up has been subjected to high heat flux loading in electron beam simulation. The divertor design concept is based on a carbon-fiber-composite material (Aerolor 05) brazed onto a TZM/Mo41Re heat sink. The plasma facing carbon armor is divided in seven tiles to allow variable loading parameters - and repeated destructive tests. The mock-up has survived high heat flux loading up to about 12 MW/m2 surface heat flux in steady-state conditions. One armor tile showed no change in the thermal response even after 500 s at ∝14 MW/m2. To estimate the general thermal response of the mock-up design, numerical methods were applied. The predicted behavior was confirmed by the experimental results. The loading experiments were followed by a detailed metallurgical investigation of the loaded sample regions and the braze joints. The typical damages after high heat flux testing and cycling were failure (i.e. detachment) in the Zr brazed carbon/TZM joint, and failure in the CuPd bonded TZM/TZM joint due to an excess of the melting temperature of the brazes. The microstructural changes in the braze regions and the recrystallization behavior of the refractory alloys are discussed. Only in one case the loaded surface of the carbon armor shows considerable erosion, caused by a partial detachment along a braze joint and thus loss of the good thermal contact during the last applied loading shots. The thermal analyses and high heat flux performance of the Aerolor-05 armored mock-up are compared to the thermal response of a previously tested mock-up of corresponding geometry with armor tiles of isotropic graphite. (orig.)

  6. Gasketed plate type heat exchanger design software

    OpenAIRE

    Gebremariam, Aklilu

    2016-01-01

    The purpose of this thesis was to make the design of gasketed plate type heat exchangers easier, simple, and accurate by reducing human error. Properly designed heat exchangers can provide more benefits and better safety in wide range of applications. Since the design of heat exchangers is so complicated and involves several steps, computer-aided design has come to be widely used. In this design, along with the knowledge of heat exchangers, the Visual Studio 2013 Professional and the programm...

  7. Decontamination of Primary Heat Exchanger Heat Transfer Plate in HANARO

    International Nuclear Information System (INIS)

    In HANARO, a multi-purpose research reactor, a 30 MWth open-tank-in-pool type, a plate type primary heat exchanger transfers the reactor core residual heat absorbed by a primary coolant to a secondary coolant. There was a leakage in the gasket of the no. one heat exchanger after about five years of normal operation. The leaking heat transfer plate pack was replaced with a new one and decontaminated. This paper describes the method of decontaminating the radioactivity of the no. 1 heat exchanger used plate pack and the results. A chemical treatment method was applied to the decontamination. This treatment method consists of cleaning the used plate with a hydro jet after properly depositing it in a scale agent

  8. A Review on Heat Transfer Improvent of Plate Heat Exchanger

    Directory of Open Access Journals (Sweden)

    Abhishek Nandan

    2015-03-01

    Full Text Available Plate heat exchanger has found a wide range of application in various industries like food industries, chemical industries, power plants etc. It reduces the wastage of energy and improves the overall efficiency of the system. Hence, it must be designed to obtain the maximum heat transfer possible. This paper is presented in order to study the various theories and results given over the improvement of heat transfer performance in a plate heat exchanger. However, there is still a lack in data and generalized equations for the calculation of different parameters in the heat exchanger. It requires more attention to find out various possible correlations and generalized solutions for the performance improvement of plate heat exchanger.

  9. Development of a brazing process for the production of water- cooled bipolar plates made of chromium-coated metal foils for PEM fuel cells

    Science.gov (United States)

    Mueller, M.; Hoehlich, D.; Scharf, I.; Lampke, T.; Hollaender, U.; Maier, H. J.

    2016-03-01

    Beside lithium batteries, PEM fuel cells are the most promising strategy as a power source to achieve the targets for introducing and increasing the usage of electric vehicles. Due to limited space and weight problems, water cooled, metallic bipolar plates in a fuel cell metal stack are preferred in motor vehicles. These plates are stamped metal sheets with a complex structure, interconnected media-tight. To meet the multiple tasks and requirements in use, complex and expensive combinations of materials are currently in use (carbon fiber composites, graphite, gold-plated nickel, stainless and acid resistant steel). The production of such plates is expensive as it is connected with considerable effort or the usage of precious metals. As an alternative, metalloid nitrides (CrN, VN, W2N, etc.) show a high chemical resistance, hardness and a good conductivity. So this material category meets the basic requirements of a top layer. However, the standard methods for their production (PVD, CVD) are expensive and have a slow deposition rate and a lower layer thicknesses. Because of these limitations, a full functionality over the life cycle of a bipolar plate is not guaranteed. The contribution shows the development and quantification of an alternative production process for bipolar plates. The expectation is to get significant advantages from the combination of chromium electrodeposition and thermochemical treatment to form chromium nitrides. Both processes are well researched and suitable for series production. The thermochemical treatment of the chromium layer also enables a process-integrated brazing.

  10. Vacuum Brazing of Accelerator Components

    Science.gov (United States)

    Singh, Rajvir; Pant, K. K.; Lal, Shankar; Yadav, D. P.; Garg, S. R.; Raghuvanshi, V. K.; Mundra, G.

    2012-11-01

    Commonly used materials for accelerator components are those which are vacuum compatible and thermally conductive. Stainless steel, aluminum and copper are common among them. Stainless steel is a poor heat conductor and not very common in use where good thermal conductivity is required. Aluminum and copper and their alloys meet the above requirements and are frequently used for the above purpose. The accelerator components made of aluminum and its alloys using welding process have become a common practice now a days. It is mandatory to use copper and its other grades in RF devices required for accelerators. Beam line and Front End components of the accelerators are fabricated from stainless steel and OFHC copper. Fabrication of components made of copper using welding process is very difficult and in most of the cases it is impossible. Fabrication and joining in such cases is possible using brazing process especially under vacuum and inert gas atmosphere. Several accelerator components have been vacuum brazed for Indus projects at Raja Ramanna Centre for Advanced Technology (RRCAT), Indore using vacuum brazing facility available at RRCAT, Indore. This paper presents details regarding development of the above mentioned high value and strategic components/assemblies. It will include basics required for vacuum brazing, details of vacuum brazing facility, joint design, fixturing of the jobs, selection of filler alloys, optimization of brazing parameters so as to obtain high quality brazed joints, brief description of vacuum brazed accelerator components etc.

  11. Vacuum Brazing of Accelerator Components

    International Nuclear Information System (INIS)

    Commonly used materials for accelerator components are those which are vacuum compatible and thermally conductive. Stainless steel, aluminum and copper are common among them. Stainless steel is a poor heat conductor and not very common in use where good thermal conductivity is required. Aluminum and copper and their alloys meet the above requirements and are frequently used for the above purpose. The accelerator components made of aluminum and its alloys using welding process have become a common practice now a days. It is mandatory to use copper and its other grades in RF devices required for accelerators. Beam line and Front End components of the accelerators are fabricated from stainless steel and OFHC copper. Fabrication of components made of copper using welding process is very difficult and in most of the cases it is impossible. Fabrication and joining in such cases is possible using brazing process especially under vacuum and inert gas atmosphere. Several accelerator components have been vacuum brazed for Indus projects at Raja Ramanna Centre for Advanced Technology (RRCAT), Indore using vacuum brazing facility available at RRCAT, Indore. This paper presents details regarding development of the above mentioned high value and strategic components/assemblies. It will include basics required for vacuum brazing, details of vacuum brazing facility, joint design, fixturing of the jobs, selection of filler alloys, optimization of brazing parameters so as to obtain high quality brazed joints, brief description of vacuum brazed accelerator components etc.

  12. Vibration isolation of dimple plate heat exchangers / Pieter Vergeer

    OpenAIRE

    Vergeer, Pieter

    2012-01-01

    Dimple plate heat exchangers are a new type of welded compact plate heat exchangers. The dimple plates increase the turbulence of the fluid flowing over the plate, increasing the efficiency of the heat exchanger without increasing pressure drop over the heat exchanger. The compact design of the heat exchanger makes it possible to install the heat exchanger at the top of condenser columns, reducing the footprint area of the column by replacing standard shell and tube condense...

  13. Development of vacuum brazing furnace

    International Nuclear Information System (INIS)

    In joining of components where welding process is not possible brazing processes are employed. Value added components, high quality RF systems, UHV components of high energy accelerators, carbide tools etc. are produced using different types of brazing methods. Furnace brazing under vacuum atmosphere is the most popular and well accepted method for production of the above mentioned components and systems. For carrying out vacuum brazing successfully it is essential to have a vacuum brazing furnace with latest features of modern vacuum brazing technology. A vacuum brazing furnace has been developed and installed for carrying out brazing of components of copper, stainless steel and components made of dissimilar metals/materials. The above furnace has been designed to accommodate jobs of 700mm diameter x 2000mm long sizes with job weight of 500kgs up to a maximum temperature of 1250 degC at a vacuum of 5 x 10-5 Torr. Oil diffusion pumping system with a combination of rotary and mechanical booster pump have been employed for obtaining vacuum. Molybdenum heating elements, radiation shield of molybdenum and Stainless Steel Grade 304 have been used. The above furnace is computer controlled with manual over ride facility. PLC and Pentium PC are integrated together to maneuver steps of operation and safety interlocks of the system. Closed loop water supply provides cooling to the system. The installation of the above system is in final stage of completion and it will be ready for use in next few months time. This paper presents insights of design and fabrication of a modern vacuum brazing furnace and its sub-system. (author)

  14. Simulation based analysis of laser beam brazing

    Science.gov (United States)

    Dobler, Michael; Wiethop, Philipp; Schmid, Daniel; Schmidt, Michael

    2016-03-01

    Laser beam brazing is a well-established joining technology in car body manufacturing with main applications in the joining of divided tailgates and the joining of roof and side panels. A key advantage of laser brazed joints is the seam's visual quality which satisfies highest requirements. However, the laser beam brazing process is very complex and process dynamics are only partially understood. In order to gain deeper knowledge of the laser beam brazing process, to determine optimal process parameters and to test process variants, a transient three-dimensional simulation model of laser beam brazing is developed. This model takes into account energy input, heat transfer as well as fluid and wetting dynamics that lead to the formation of the brazing seam. A validation of the simulation model is performed by metallographic analysis and thermocouple measurements for different parameter sets of the brazing process. These results show that the multi-physical simulation model not only can be used to gain insight into the laser brazing process but also offers the possibility of process optimization in industrial applications. The model's capabilities in determining optimal process parameters are exemplarily shown for the laser power. Small deviations in the energy input can affect the brazing results significantly. Therefore, the simulation model is used to analyze the effect of the lateral laser beam position on the energy input and the resulting brazing seam.

  15. Diffusion barriers in modified air brazes

    Science.gov (United States)

    Weil, Kenneth Scott; Hardy, John S; Kim, Jin Yong; Choi, Jung-Pyung

    2013-04-23

    A method for joining two ceramic parts, or a ceramic part and a metal part, and the joint formed thereby. The method provides two or more parts, a braze consisting of a mixture of copper oxide and silver, a diffusion barrier, and then heats the braze for a time and at a temperature sufficient to form the braze into a bond holding the two or more parts together. The diffusion barrier is an oxidizable metal that forms either a homogeneous component of the braze, a heterogeneous component of the braze, a separate layer bordering the braze, or combinations thereof. The oxidizable metal is selected from the group Al, Mg, Cr, Si, Ni, Co, Mn, Ti, Zr, Hf, Pt, Pd, Au, lanthanides, and combinations thereof.

  16. Solar heat mirrors produced by ion plating

    International Nuclear Information System (INIS)

    Transparent conducting oxide films have been produced by the reactive ion plating of indium onto glass and plastic substrates at room temperature. The electrical properties of these films were sufficient, with high values of electrical mobility and carrier density, to give a sharp plasma reflectance edge in the near infra-red. These properties are ideally suited for the production of visibly transmitting, infra-red reflecting surfaces needed for heat mirror applications. Optimum properties are achieved with careful control of the gas mixture and amount of substrate bias acquired by the substrate from the radio frequency used for the discharge. Satisfactory films could be made starting from evaporation or planar magnetron sputtering sources. (author)

  17. PENGARUH TEBAL ISOLASI TERMAL TERHADAP EFEKTIVITAS PLATE HEAT EXCHANGER

    OpenAIRE

    Ekadewi Anggraini Handoyo

    2000-01-01

    In a heat exchanger, there is heat transferred either from the surrounding or to the surrounding, which is not expected. A thermal insulator is used to reduce this heat transfer. The effectiveness of a heat exchanger will increase if the heat loss to surrounding can be reduced. Theoretically, the thicker the insulator the smaller the heat loss in a plate heat exchanger. A research is carried on to study the effect of an insulator thickness on heat exchanger effectiveness. The insulators used ...

  18. Experimental investigation of heat transfer and effectiveness in corrugated plate heat exchangers having different chevron angles

    Science.gov (United States)

    Kılıç, Bayram; İpek, Osman

    2016-06-01

    In this study, heat transfer rate and effectiveness of corrugated plate heat exchangers having different chevron angles were investigated experimentally. Chevron angles of plate heat exchangers are β = 30° and β = 60°. For this purpose, experimentally heating system used plate heat exchanger was designed and constructed. Thermodynamic analysis of corrugated plate heat exchangers having different chevron angles were carried out. The heat transfer rate and effectiveness values are calculated. The experimental results are shown that heat transfer rate and effectiveness values for β = 60° is higher than that of the other. Obtained experimental results were graphically presented.

  19. Performance of tubes-and plate fins heat exchangers

    International Nuclear Information System (INIS)

    By means of a two-dimensional analysis performance, and using local heat transfer coefficients, the plate fin temperature distribution, the air bulk temperature along the stream path and the fin efficiency can be obtained, for several Reynolds numbers and fin materials. Herein are also presented the average heat transfer coefficients for isothermal plate fins, referring to heat exchangers with central-tube and rear-tube row and to two-row tubes heat exchangers configurations. It is possible to obtain the real tax or the real area of heat transfer, using the average hea transfer coefficients for isothermal plate fins and the fin efficiency. (Author)

  20. Performance Investigation of Plate Type Heat Exchanger (A Case Study

    Directory of Open Access Journals (Sweden)

    Simarpreet Singh

    2014-04-01

    Full Text Available Heat exchanger is a thermodynamic system which is most commonly used in the process industry for exchanging heat energy between the fluids. flowing in the same or opposite direction. It is desired that effectiveness of heat exchanger should remain as large as possible. Heat exchanger's performance may be improved by the addition of fins or corrugations. These investigations include design of plate type heat exchanger, heat transfer enhancement, flow phenomenon and cleanliness factor. In process plants, this type of heat exchange is generally used for recovering heat content of exhaust steam. However, with the flow of fluid for a long period, fouling occurs on the plate surface. Therefore, it is required to investigate the effect of fouling, wherever the heat exchanger is installed. An extensive experimental investigation has been carried out under clean and dirty condition of the said plate type heat exchanger. Heat transfer and flow data were collected in experiment. From collected data heat transfer rate, overall heat transfer coefficient, fouling factor and cleanliness factor were evaluated. Based upon the cleanliness factor data, next date of cleanliness for plate type heat exchanger was predicted. It is felt that the outcome of the present research work may be quite useful for efficient operation of plate type heat exchanger installed in Process plants.

  1. Development of brazing technique for a 1.6 cell BNL/SLAC/UCLA type photocathode guns by hydrogen brazing

    International Nuclear Information System (INIS)

    Two prototypes of a 1.6 cell BNL/SLAC/UCLA type RF photocathode gun, a precision machined RF structure capable of supporting gradients in excess of 80 MV/m, have been successfully brazed and leak rates of 10-10 mbar l/s have been achieved. Brazing, is carried out in two steps in a hydrogen furnace, it involves joining of two RF cavities, 6 cylindrical ports, one rectangular waveguide and one seal plate. The cavities and waveguide are made of copper and the ports and seal plate are of stainless steel. Fixtures were designed and fabricated indigenously to maintain the required assembly tolerances during brazing. This was important for brazing of ports, two of which are brazed to one cavity at an angle of 22.50 at diametrically opposite locations, and the remaining four are brazed to the other cavity in mutually perpendicular orientations. All joints were brazed using copper-silver eutectic (72-28) alloy in foil and wire forms. This paper discusses the brazing requirement, design of fixtures, and the procedure adopted for brazing of the photocathode gun. The paper also discusses results of the tests carried out to qualify the brazed joints. (author)

  2. Performance Investigation of Plate Type Heat Exchanger (A Case Study)

    OpenAIRE

    Simarpreet Singh; Sanjeev Jakhar

    2014-01-01

    Heat exchanger is a thermodynamic system which is most commonly used in the process industry for exchanging heat energy between the fluids. flowing in the same or opposite direction. It is desired that effectiveness of heat exchanger should remain as large as possible. Heat exchanger's performance may be improved by the addition of fins or corrugations. These investigations include design of plate type heat exchanger, heat transfer enhancement, flow phenomenon and cleanliness ...

  3. The effect of plate heat exchanger’s geometry on heat transfer

    OpenAIRE

    Oana GIURGIU; Angela PLEŞA; Dan OPRUŢA

    2014-01-01

    The study presents further Computational Fluid Dynamics (CFD) numerical analysis for two models of plate heat exchangers. Comparatively was studied the influence of geometric characteristics of plates on the intensification process of heat exchange. For this purpose, it was examined the distribution of velocity and temperatures fields on active plate height. Heat transfer characteristics were analysed through the variation of mass flow on the primary heat agent.

  4. Braze Process Optimization Involving Conventional Metal/Ceramic Brazing with 50Au-50Cu Alloy

    Energy Technology Data Exchange (ETDEWEB)

    MALIZIA JR.,LOUIS A.; MEREDITH,KEITH W.; APPEL,DANIEL B.; MONROE,SAUNDRA L.; BURCHETT,STEVEN N.; STEPHENS JR.,JOHN J.

    1999-12-15

    Numerous process variables can influence the robustness of conventional metal/ceramic brazing processes. Experience with brazing of hermetic vacuum components has identified the following parameters as influencing the outcome of hydrogen furnace brazed Kovar{trademark} to metallized alumina braze joints: (a) Mo-Mn metallization thickness, sinter fire temperature and porosity (b) Nil plate purity, thickness, and sinter firing conditions (c) peak process temperature, time above liquidus and (d) braze alloy washer thickness. ASTM F19 tensile buttons are being used to investigate the above parameters. The F19 geometry permits determination of both joint hermeticity and tensile strength. This presentation will focus on important lessons learned from the tensile button study: (A) the position of the Kovar{trademark} interlayer can influence the joint tensile strength achieved--namely, off-center interlayers can lead to residual stress development in the ceramic and degrade tensile strength values. Finite element analysis has been used to demonstrate the expected magnitude in strength degradation as a function of misalignment. (B) Time above liquidus (TAL) and peak temperature can influence the strength and alloying level of the resulting braze joint. Excessive TAL or peak temperatures can lead to overbraze conditions where all of the Ni plate is dissolved. (C) Metallize sinter fire processes can influence the morphology and strength obtained from the braze joints.

  5. Brazing of inconel 600 and SUS304 stainless steel with used of rapidly solidified nickel-base brazing foil

    Energy Technology Data Exchange (ETDEWEB)

    Miyazawa, Yasuyuki; Ariga, Tadashi (Tokai Univ., Tokyo (Japan))

    1992-05-01

    In this study, the clad material which have been brazed with the nickel-base heat resistant alloy; Inconel 600 on AISI304 stainless steel has been produced by the brazing using three types of nickel-base brazing foils. The three types of nickel-base brazing foils are 7Cr(4.5Si-7.0Cr-3.0B-3.0Fe-Ni bal.), 5Cr(4.5Si-5.0Cr-3.0B-3.0Fe-Ni bal.) and 10Cr(4.5Si-10.0Cr-3.0B-3.0Fe-Ni bal.). Brazing was done in an electrical resistant furnace in an argon gas atmosphere. The brazing temperatures employed in this study were 1050, 1100, 1150, 1200 and 1250degC and the brazing times were 10, 30, 60 and 120 min for all types of brazing foils. The property of the joint was estimated by the mechanical properties, microstructures and distributions of the elements which were investigated by SEM and EPMA. The brazed joint was obtained for all of brazing conditions in this study. The shear strength of the specimen increased with increasing brazing time except at 1050degC. At 1050degC, the shear strength of the specimen was not influenced by brazing time. In this case, the break of the specimen during the shear test occurred in the brazed layer. At 1250degC, the value of 450 MPa was obtained as the maximum shear strength in this study; the break of the specimen occurred in the base metal. The shear strength of the specimen increased with increasing brazing temperature. The shear strength of the specimen increased with increasing chromium content in the brazing foil to 7 mass%. (J.P.N.).

  6. Brazing of inconel 600 and SUS304 stainless steel with used of rapidly solidified nickel-base brazing foil

    International Nuclear Information System (INIS)

    In this study, the clad material which have been brazed with the nickel-base heat resistant alloy; Inconel 600 on AISI304 stainless steel has been produced by the brazing using three types of nickel-base brazing foils. The three types of nickel-base brazing foils are 7Cr(4.5Si-7.0Cr-3.0B-3.0Fe-Ni bal.), 5Cr(4.5Si-5.0Cr-3.0B-3.0Fe-Ni bal.) and 10Cr(4.5Si-10.0Cr-3.0B-3.0Fe-Ni bal.). Brazing was done in an electrical resistant furnace in an argon gas atmosphere. The brazing temperatures employed in this study were 1050, 1100, 1150, 1200 and 1250degC and the brazing times were 10, 30, 60 and 120 min for all types of brazing foils. The property of the joint was estimated by the mechanical properties, microstructures and distributions of the elements which were investigated by SEM and EPMA. The brazed joint was obtained for all of brazing conditions in this study. The shear strength of the specimen increased with increasing brazing time except at 1050degC. At 1050degC, the shear strength of the specimen was not influenced by brazing time. In this case, the break of the specimen during the shear test occurred in the brazed layer. At 1250degC, the value of 450 MPa was obtained as the maximum shear strength in this study; the break of the specimen occurred in the base metal. The shear strength of the specimen increased with increasing brazing temperature. The shear strength of the specimen increased with increasing chromium content in the brazing foil to 7 mass%. (J.P.N.)

  7. Numerical Methods for Plate Forming by Line Heating

    DEFF Research Database (Denmark)

    Clausen, Henrik Bisgaard

    2000-01-01

    Line heating is the process of forming originally flat plates into a desired shape by means of heat treatment. Parameter studies are carried out on a finite element model to provide knowledge of how the process behaves with varying heating conditions. For verification purposes, experiments are...... carried out; one set of experiments investigates the actual heat flux distribution from a gas torch and another verifies the validty of the FE calculations. Finally, a method to predict the heating pattern is described....

  8. Heat treatment of heavy section low alloy steel plates

    International Nuclear Information System (INIS)

    Heavy section low alloy steel plates are used for nuclear reactor and direct oil desulfurizing reactor pressure vessels, etc. High integrity is, therefore, required of these steel plates. The factors which affect the internal soundness and notch toughness of heavy section low alloy steel plates are discussed in relation to heat treatment after rolling. Precipitation behavior of aluminum nitride in A533B steel plates during heat treatment after rolling is described with respect to the austenite grain size and notch toughness of the plate after final rolling. Cooling down to 4000C before normalizing is recommended to obtain good notch toughness. Selection of temperature and time for dehydrogenation at the ferrite region is discussed and it is shown that the optimum temperature for dehydrogenation must be determined by taking microsegregation in the plate into consideration. (author)

  9. Simulation Studies on A Cross Flow Plate Fin Heat Exchanger

    Directory of Open Access Journals (Sweden)

    M. Thirumarimurugan

    2008-01-01

    Full Text Available Compact heat exchangers which were initially developed for the aerospace industries in the1940s have been considerably improved in the past few years. The main reasons for the goodperformance of compact heat exchangers are their special design which includes turbulent which inturn use high heat transfer coefficient and resists fouling, and maximum temperature driving forcebetween the hot and cold fluids. Numerous types use special enhancement techniques to achieve therequired heat transfer in smaller plot areas and, in many cases, less initial investment. One such type ofcompact heat exchanger is the Plate-fin heat exchanger. The complexity of compact heat exchangerdesign equations results from the exchangers unique ability to transfer heat between multiple processstreams and a wide array of possible flow configurations. This paper presents the performanceevaluation of cross flow plate fin heat exchanger with several different Gas-Liquid systems.Experimental results such as exchanger effectiveness, overall heat transfer coefficients were calculatedfor the flow systems of Cross flow Heat Exchangers. A steady state model for the outlet temperature ofboth the cold and hot fluid and overall heat transfer coefficient of a plate-fin cross flow heat exchangerwas developed and simulated using MATLAB, which was verified with the experiments conducted.

  10. Experimental performance studies of a plate heat exchanger

    OpenAIRE

    Plath, Darren R.

    1996-01-01

    A plate and frame heat exchanger experimental test stand was developed. Using this test stand a performance analysis was conducted. The analysis consisted of evaluating the performance of the heat exchanger at varying flow rates and inlet temperatures, to develop an effectiveness-NTU and Log Mean Temperature Difference relationships, under steady state operation. The measured heat rates were compared to the heat rates provided by the manufacturer and good/bad agreement was found. Standard ope...

  11. Experimental Analysis of Heat Transfer Behavior inside Heat Pipe Integrated with Cooling Plates

    OpenAIRE

    Chen-Ching Ting; Chien-Chih Chen

    2011-01-01

    This work used experimental methods to study heat transfer behavior inside a heat pipe and found that heat transfer behavior inside the heat pipe was changed due to its integration with cooling plates. This change caused the heat pipe to have copper-like heat transfer behavior. Experimental performances first built a CPU simulator with maximum heat power 300 W in accordance with the ASTM standard as heat source and measured temperature distribution by using infrared thermography and thermocou...

  12. A concept of PWR using plate and shell heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Freire, Luciano Ondir; Andrade, Delvonei Alves de, E-mail: luciano.ondir@gmail.com, E-mail: delvonei@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    In previous work it was verified the physical possibility of using plate and shell heat exchangers for steam generation in a PWR for merchant ships. This work studies the possibility of using GESMEX commercial of the shelf plate and shell heat exchanger of series XPS. It was found it is feasible for this type of heat exchanger to meet operational and accidental requirements for steam generation in PWR. Additionally, it is proposed an arrangement of such heat exchangers inside the reactor pressure vessel. Such arrangement may avoid ANSI/ANS51.1 nuclear class I requirements on those heat exchangers because they are contained in the reactor coolant pressure barrier and play no role in accidental scenarios. Additionally, those plates work under compression, preventing the risk of rupture. Being considered non-nuclear safety, having a modular architecture and working under compression may turn such architectural choice a must to meet safety objectives with improved economics. (author)

  13. A concept of PWR using plate and shell heat exchangers

    International Nuclear Information System (INIS)

    In previous work it was verified the physical possibility of using plate and shell heat exchangers for steam generation in a PWR for merchant ships. This work studies the possibility of using GESMEX commercial of the shelf plate and shell heat exchanger of series XPS. It was found it is feasible for this type of heat exchanger to meet operational and accidental requirements for steam generation in PWR. Additionally, it is proposed an arrangement of such heat exchangers inside the reactor pressure vessel. Such arrangement may avoid ANSI/ANS51.1 nuclear class I requirements on those heat exchangers because they are contained in the reactor coolant pressure barrier and play no role in accidental scenarios. Additionally, those plates work under compression, preventing the risk of rupture. Being considered non-nuclear safety, having a modular architecture and working under compression may turn such architectural choice a must to meet safety objectives with improved economics. (author)

  14. Analysis of sweeping heat loads on divertor plate materials

    International Nuclear Information System (INIS)

    The heat flux on the divertor plate of a fusion reactor is probably one of the most limiting constraints on its lifetime. The current heat flux profile on the outer divertor plate of a device like ITER is highly peaked with narrow profile. The peak heat flux can be as high as 30--40 MW/m2 with full width at half maximum (FWHM) is in the order of a few centimeters. Sweeping the separatrix along the divertor plate is one of the options proposed to reduce the thermomechanical effects of this highly peaked narrow profile distribution. The effectiveness of the sweeping process is investigated parametrically for various design values. The optimum sweeping parameters of a particular heat load will depend on the design of the divertor plate as well as on the profile of such a heat load. In general, moving a highly peaked heat load results in substantial reduction of the thermomechanical effects on the divertor plate. 3 refs., 8 figs

  15. Flat plate electrohydrodynamic heat pipe experiments

    Energy Technology Data Exchange (ETDEWEB)

    Loehrke, R.I.; Sebits, D.R.

    1975-07-01

    Performance capabilities of electrohydrodynamic (EHD) flat heat pipes were investigated using Freon 113 and Freon 11 as working fluids. All of the pipes employed straight rod electrodes to form axial liquid flow channels and tranverse grooves for capillary surface wetting. Results show: (1) the EHD pipe will prime under load; (2) voltage controlled conductance can be achieved by varying the active area of the evaporator; and (3) the average evaporator conductances measured in these experiments were consistent with those obtained in other experiments with heat pipes of similar surface geometry using the same or similar working fluids.

  16. External heating of a flat plate in a convective flow

    OpenAIRE

    Treviño, César; Liñán Martínez, Amable

    1984-01-01

    The steady-state and íransient processes of the exteinal heating of a flat píate under a convective flow is studied in thís paper, with inclusión of the axial heat conduction tíirough the píate. The balance equations reduce to a single integro-differential equation with only one parameter, a, denoting the ratio of the ability of the píate tocarry heat inthestreamwisedirectionto the abilityof the gas tocarry heat outof the píate. The two Iímits of a good conducting plate ([alpha]-»[infinite]) ...

  17. Short cycle brazing of an alumina dispersion strengthened copper alloy

    International Nuclear Information System (INIS)

    An alumina dispersion strengthened copper alloy (with 0.07 wt, % alumina) has been proposed for several specialized applications in fusion reactors, such as the stabilizer in superconducting magnets and the structural material for divertors and limiters. In this research, brazed joints of the alumina dispersion strengthened copper alloy were developed using resistance heating brazing. The BCuP-3 brazing alloy was chosen based upon its low activation characteristics. Brazing was conducted using a GLEEBLE 1500 system with which time, temperature, and stress were precisely controlled. Butt-brazed joints with different brazing times were evaluated based on tensile and bending fatigue properties. Results from these tests reveal that the optimum braze time is approximately 1 minute at 8000C with a holding stress of 0.5 MPa. Metallography examinations were conducted on both the as brazed structure and the fracture surfaces. In the former, a transition layer (about 10 μm tick) was formed between the braze metal and the base alloy. Microhardness measurements across the braze did not show any hardening or softening effect due to the brazing process. Metallography of the fractured tensile and fatigue samples showed that cracks always penetrated through the interface between the transition layer and the braze metal. Semiquantitative energy dispersive x-ray spectroscopy (EDS) analysis was also performed across the joint. Profiles of P and Ag showed that P diffused very quickly into base metal along grain boundaries. A strong Al peak (associated with the detection of Al2O3) was found that corresponded with the transition layer. The presence of the alumina particles in the transition zone restricts the grain growth process in this region, resulting in relatively fine grain size

  18. The quality evaluation of the end-plate welds and brazed joints for CANDU nuclear fuel by an ultrasonic imaging method

    International Nuclear Information System (INIS)

    This paper describes a method for the quality evaluation of spot welds and brazed joints by analysing ultrasonic images (C-scan). A present, the quality control for these joints is made by destructive methods. The authors present the most frequent types of flaw met in their investigations. They have attempted to obtain a dependence of torsion moment, measured by a destructive method against the polar inertia moment, obtained from parameters measured on ultrasound images. The ultrasonic images were analysed off-line using a dedicated software. (author)

  19. Active Metal Brazing and Characterization of Brazed Joints in Titanium to Carbon-Carbon Composites

    Science.gov (United States)

    Singh, M.; Shpargel, T. P.; Morscher, G. N.; Asthana, R.

    2006-01-01

    The Ti-metal/C-C composite joints were formed by reactive brazing with three commercial brazes, namely, Cu-ABA, TiCuNi, and TiCuSiI. The joint microstructures were examined using optical microscopy and scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS). The results of the microstructure analysis indicate solute redistribution across the joint and possible metallurgical bond formation via interdiffusion, which led to good wetting and spreading. A tube-on-plate tensile test was used to evaluate joint strength of Ti-tube/ C-C composite joints. The load-carrying ability was greatest for the Cu-ABA braze joint structures. This system appeared to have the best braze spreading which resulted in a larger braze/C-C composite bonded area compared to the other two braze materials. Also, joint loadcarrying ability was found to be higher for joint structures where the fiber tows in the outer ply of the C-C composite were aligned perpendicular to the tube axis when compared to the case where fiber tows were aligned parallel to the tube axis.

  20. Deformation of ductile braze layer in a joint element under cyclic thermal loads

    International Nuclear Information System (INIS)

    The structural lifetime of a brazed joint is affected by the plastic behavior of ductile filler metal. In this work, elastoplastic analysis is performed on a CFC/Cu/TZM bonded joint for different thermal loading cases. The evolution of strains in the braze layer during the brazing process is analyzed. It is shown that the temperature dependence of the flow curves exerts considerable influence on the deformation behavior of the filler metal interlayer. The deformation characteristics of the braze layer under thermal cycling are investigated. The effect of thermal gradient on the plastic deformation of the braze is discussed. The fatigue lifetime of the copper braze layer is estimated. High heat flux (HHF) cycling tests are conducted on a CFC/Cu/TZM brazed joint in an electron beam facility. The microstructure of the deformed copper braze is presented. The flow morphologies and corresponding slip mechanisms are discussed. (orig.)

  1. HEATED PLATE TEMPERATURE MEASUREMENT USING ELECTRONIC SPECKLE PATTERN INTERFEROMERY

    OpenAIRE

    Said Rachafi; Salah Darfi

    2013-01-01

    In this work, we present an original technique for heated plate temperature measurement using electronic speckle pattern interferometry (ESPI). A Fourier Transform Method algorithm is proposed to analyze fringe patterns in order to extract the phase from which one can get the unknown temperature.

  2. Heat transport in the Hadean mantle: From heat pipes to plates

    Science.gov (United States)

    Kankanamge, Duminda G. J.; Moore, William B.

    2016-04-01

    Plate tectonics is a unique feature of Earth, and it plays a dominant role in transporting Earth's internally generated heat. It also governs the nature, shape, and the motion of the surface of Earth. The initiation of plate tectonics on Earth has been difficult to establish observationally, and modeling of the plate breaking process has not consistently accounted for the nature of the preplate tectonic Earth. We have performed numerical simulations of heat transport in the preplate tectonic Earth to understand the transition to plate tectonic behavior. This period of time is dominated by volcanic heat transport called the heat pipe mode of planetary cooling. These simulations of Earth's mantle include heat transport by melting and melt segregation (volcanism), Newtonian temperature-dependent viscosity, and internal heating. We show that when heat pipes are active, the lithosphere thickens and lithospheric isotherms are kept flat by the solidus. Both of these effects act to suppress plate tectonics. As volcanism wanes, conduction begins to control lithospheric thickness, and large slopes arise at the base of the lithosphere. This produces large lithospheric stress and focuses it on the thinner regions of the lithosphere resulting in plate breaking events.

  3. Film boiling characteristics of potassium droplets on heated plate

    International Nuclear Information System (INIS)

    For providing background information on the possible vapor explosion in the event of a core disruptive accident of LMFBRs, an experiment was conducted on the film boiling characteristics of liquid metal potassium in association with the Leidenfrost phenomenon. In a steel container filled with Ar gas, K droplets were put on a joule-heated plate of 316-SS or Ta. The behaviors of droplet were observed by a camera and a color VTR through viewports. The experimental conditions were the Ar pressure 1 bar, the initial K temperature 350 -- 7600C, and the plate temperature 900 -- 1,2500C for 316-SS and 1,100 -- 1,6000C for Ta. Stable film boiling known as Leidenfrost phenomenon was observed for a high temperature condition of the plate, whereas an instantaneous break-up of droplet with extensive vaporization occurred for a low temperature. The heat transfer characteristics of film and transition boiling regions were obtaind by estimating the heat flux from the volumetric reducing rate of droplet due to vaporization. The results in the film boiling region showed an appreciably good agreement with the prediction based on Bromley's expression combined with the theory of Baumeister et al. The minimum film boiling temperature and heat flux were found to be about 1,3000C and 15 W/cm2, respectively, for a droplet size of 0.15 cm3. (author)

  4. Dissimilar joint characteristics of SiC and WC-Co alloy by laser brazing

    Science.gov (United States)

    Nagatsuka, K.; Sechi, Y.; Nakata, K.

    2012-08-01

    SiC and WC-Co alloys were joined by laser brazing with an active braze metal. The braze metal based on eutectic Ag-Cu alloy with additional Ti as an active element ranging from 0 to 2.8 mass% was sandwiched by the SiC block and WC-Co alloy plate. The brazing was carried out by selective laser beam irradiation on the WC-Co alloy plate. The content of Ti in the braze metal was required to exceed 0.6 mass% in order to form a brazed joint with a measurable shear strength. The shear strength increased with increasing Ti content up to 2.3 mass%Ti and decreased with a higher content.

  5. Brazing molybdenum and tungsten for high temperature service

    International Nuclear Information System (INIS)

    Investigations were conducted to develop vacuum brazes for molybdenum and tungsten which can be used in seal joint applications up to 1870 K (1597 C, 2907 F). Joints were attempted in molybdenum, tungsten and tungsten--molybdenum. The braze materials included: Ti--10Cr powder, Ti--30V wire, Ti--65V wire, V wire, Ni electroplate, MoB--50MoC powder mixture, V--50Mo powder mixture, Mo--15MoB2 powder mixture and Mo--49V--15MoB2 powder mixture. Braze temperature ranged from 1900 K (1627 C, 2961 F) to 2530 K, (2257 C, 4095 F), and leak-tight joints were made with all braze materials except Ti--10Cr. After heat treatments up to 1870 K (1597 C, 2907 F) Kirkendall voiding was found to cause leakage of some of the joints made with only substitutional alloying elements. However, adding base metal powders to the braze or narrowing the root opening eliminated this problem. Kirkendall voiding was not a problem when interstitial elements were a major ingredient in the braze material. Shear testing of Ti--65V, V, MoB--50MoC and V--50Mo brazed molybdenum at 1670 K (1397 C, 2547 F) indicated strengths equal to or better than the base metal. Ti--65V, V--50Mo and MoB--50MoC brazed joints were exposed to basalt at 1670 K (1397 C, 2547 F) for 3 h without developing leaks

  6. Effect of Localized Heating on Three-Dimensional Flat-Plate Oscillating Heat Pipe

    OpenAIRE

    Ma, H. B.; Thompson, S.M.

    2010-01-01

    An experimental investigation was conducted, both thermally and visually, on a three-dimensional flat-plate oscillating heat pipe (3D FP-OHP) to characterize its performance under localized heat fluxes while operating in the bottom heating mode and charged with acetone at a filling ratio of 0.73. The cooling area was held constant and three heating areas of 20.16 cm2, 11.29 cm2, and 1.00 cm2 were investigated, respectively. It was found that as the heating area was reduced and higher heat flu...

  7. New developments in compact plate-fin heat exchangers

    International Nuclear Information System (INIS)

    The extension of compact plate-fin heat exchanger capabilities in order to accommodate the performance requirements of regeneratively cooled hypersonic ramjet engines, laser weapons, aircraft engine infrared suppressors, and large high-efficiency gas turbine cycles is described. Attention is given to cooling fluid flow path geometry and heat exchanger fabrication techniques, such novel materials as alumina and silicon carbide, and space and weight constraints imposed on designs by airborne application. It is shown that operating temperatures, pressures and area densities have been significantly increased

  8. Transfer coefficients for plate fin and elliptical tube heat exchangers

    International Nuclear Information System (INIS)

    In order to determine transfer coefficients for plate fin and elliptical tube exchangers, mass transfer experiments have been performed using the naphthalene sublimation technique. By means of the heat-mass transfer analogy, the results can be converted to heat transfer results. The transfer coefficients were compared with those for circular tube exchangers and the comparison revealed no major differences. This is a positive outcome, since the use of elliptical tubes may reduce substantially the pressure drop, without affecting the transfer characteristics.(Author)

  9. Plate type heat exchanger for Reaktor TRIGA PUSPATI

    International Nuclear Information System (INIS)

    The PUSPATI TRIGA reactor (RTP) reached its first criticality status on 28 June 1982 with an installed capacity of 1 MW. After 26 years in operation, the ageing process has set in and many systems in the reactor need maintenance and replacement. Among these systems, the more critical one is the heat exchanger system. Currently, the shell and tube type heat exchanger is being used. It has been observed that the performance of the heat exchanger has dropped significantly over the years. Visual inspections indicate that the tubes are corroded or even to the extent of being totally blocked. With this in mind and also with the setting up of the new Nuclear Power Division, whose mission includes upgrading the present reactor to 3 MW, the heat exchanger system is essential and a critical component. Literature indicates that the use of plate type exchangers are more efficient than the current shell and tube type. This paper will look into the engineering and safety aspects of using the plate type heat exchanger to the current TRIGA PUSPATI reactor. (Author)

  10. Boiling heat transfer of refrigerant R-21 in upward flow in plate-fin heat exchanger

    Science.gov (United States)

    Kuznetsov, V. V.; Shamirzaev, A. S.

    2015-11-01

    The article presents the results of experimental investigation of boiling heat transfer of refrigerant R-21 in upward flow in a vertical plate-fin heat exchanger with transverse size of the channels that is smaller than the capillary constant. The heat transfer coefficients obtained in ranges of small mass velocities and low heat fluxes, which are typical of the industry, have been poorly studied yet. The characteristic patterns of the upward liquid-vapor flow in the heat exchanger channels and the regions of their existence are detected. The obtained data show a weak dependence of heat transfer coefficient on equilibrium vapor quality, mass flow rate, and heat flux density and do not correspond to calculations by the known heat transfer models. A possible reason for this behavior is a decisive influence of evaporation of thin liquid films on the heat transfer at low heat flux.

  11. Hybrid heat recovery - flat plate Stirling engine system

    International Nuclear Information System (INIS)

    In this paper, the possibility of process condensate heat recovery for boiler water preheating as well as for combined heat and power production for chosen process in textile industry has been investigated. The garment industry requires low pressure process steam or hot water for which production expensive fossil fuel should be used. Fuel usage can be reduced by various energy conservation methods. During the process a great quantity of hot condensate or waste hot water is rejected in the sewage system. To reduce heat wastes and improve technological process this condensate could be returned to the boiler for feed water preheating. When 60% condensate is returned to the steam generator about 8 % natural gas is saved. The rest of the condensate should be used for driving low temperature flat plate Stirling motor the advantage of the flat plate Stirling engine is ability to work at low temperatures. This engine produces electrical energy which can put in motion an electrogenerator in the same plant. While Stirling engine can be used electrical power and economical effect could be much greater using such a hybrid system the process waste heat is not only converted into useful work but at the same time thermal pollution is greatly diminished. (Author)

  12. A numerical analysis on the heat transfer and pressure drop characteristics of welding type plate heat exchangers

    International Nuclear Information System (INIS)

    Numerical analysis was carried out to examine the heat transfer and pressure drop characteristics of plate heat exchangers for absorption application using computational Fluid Dynamics(CFD) technique. A commercial CFD software package, FLUENT was used to predict the characteristics of heat transfer, pressure drop and flow distribution within plate heat exchangers. In this paper, a welded plate heat exchanger with the plate of chevron embossing type was numerically analyzed by controlling mass flow rate, solution concentration, and inlet temperatures. The working fluid is H2O/LiBr solution with the LiBr concentration of 50∼60% in mass. The numerical simulation show reasonably good agreement with the experimental results. Also, the numerical results show that plate of the chevron shape gives better results than plate of the elliptical shape from the view points of heat transfer and pressure drop. These results provide a guideline to apply the welded PHE for the solution heat exchanger of absorption systems

  13. Study of plate-fin heat exchanger and cold plate for the active thermal control system of Space Station

    Science.gov (United States)

    Chyu, MING-C.

    1992-01-01

    Plate-fin heat exchangers will be employed in the Active Thermal Control System of Space Station Freedom. During ground testing of prototypic heat exchangers, certain anomalous behaviors have been observed. Diagnosis has been conducted to determine the cause of the observed behaviors, including a scrutiny of temperature, pressure, and flow rate test data, and verification calculations based on such data and more data collected during the ambient and thermal/vacuum tests participated by the author. The test data of a plate-fin cold plate have been also analyzed. Recommendation was made with regard to further tests providing more useful information of the cold plate performance.

  14. Soldering and brazing safety guide: A handbook on space practice for those involved in soldering and brazing

    Science.gov (United States)

    This manual provides those involved in welding and brazing with effective safety procedures for use in performance of their jobs. Hazards exist in four types of general soldering and brazing processes: (1) cleaning; (2) application of flux; (3) application of heat and filler metal; and (4) residue cleaning. Most hazards during those operations can be avoided by using care, proper ventilation, protective clothing and equipment. Specific process hazards for various methods of brazing and soldering are treated. Methods to check ventilation are presented as well as a check of personal hygiene and good maintenance practices are stressed. Several emergency first aid treatments are described.

  15. Flow and heat transfer of ferrofluids over a flat plate with uniform heat flux

    Science.gov (United States)

    Khan, W. A.; Khan, Z. H.; Haq, R. U.

    2015-04-01

    The present work is dedicated to analyze the flow and heat transport of ferrofluids along a flat plate subjected to uniform heat flux and slip velocity. A magnetic field is applied in the transverse direction to the plate. Moreover, three different kinds of magnetic nanoparticles (Fe3O4, CoFe2O4, Mn-ZnFe2O4 are incorporated within the base fluid. We have considered two different kinds of base fluids (kerosene and water) having poor thermal conductivity as compared to solid magnetic nanoparticles. Self-similar solutions are obtained and are compared with the available data for special cases. A simulation is performed for each ferrofluid mixture by considering the dominant effects of slip and uniform heat flux. It is found that the present results are in an excellent agreement with the existing literature. The variation of skin friction and heat transfer is also performed at the surface of the plate and then the better heat transfer and of each mixture is analyzed. Kerosene-based magnetite Fe3O4 provides the higher heat transfer rate at the wall as compared to the kerosene-based cobalt ferrite and Mn-Zn ferrite. It is also concluded that the primary effect of the magnetic field is to accelerate the dimensionless velocity and to reduce the dimensionless surface temperature as compared to the hydrodynamic case, thereby increasing the skin friction and the heat transfer rate of ferrofluids.

  16. Development of optimum process parameters and a study of the effects of surface roughness on brazing of copper

    International Nuclear Information System (INIS)

    Highlights: • New brazing process parameters corresponding to the greatest shear strength have been developed. • An effective interaction of brazing filler metal (BFM) and base metal was observed at the interface for the sample brazed at 650 °C/5 min. • The possibility of formation of hard intermetallic compounds of Cu, Sn, and P have been justified in view of high-strength braze joint. • The surface roughness with an average Ra value of around 0.20 μm was found to be the most appropriate for brazing of copper conducted at the specified process parameters. - Abstract: Brazing experiments on commercially-pure copper plates, using brazing filler metal (MBF-2005), are conducted at temperatures in the range of 650–750 °C for time-durations in the range of 5–15 min. Shear tests for braze-joints involved use of a universal testing machine. Based on the shear-test results, a new brazing cycle has been developed that corresponds to the greatest shear strength of the braze-joint. The brazing cycle has been performed under a controlled dry-argon atmosphere in a tube furnace. Microscopic observations were made by use of both optical and electron microscopes; whereas surface roughness measurements were made by using a TR100 Surface Roughness Tester. It is found that successful brazing and good wetting can be achieved by the least voids by using an average surface roughness (Ra value) for the base material

  17. Investigation of a wire plate micro heat pipe array

    Energy Technology Data Exchange (ETDEWEB)

    Launay, Stephane; Sartre, Valerie; Lallemand, Monique [CETHIL, UMR CNRS 5008, INSA, 20, av. A. Einstein, 69621 Cedex, Villeurbanne (France); Mantelli, Marcia B.H.; Paiva, Kleber Vieira de [Mechanical Engineering Department, Federal University of Santa Catarina UFSC, P.O. Box 476, 88040-900, SC, Florianopolis (Brazil)

    2004-05-01

    In the present work, experimental and theoretical investigations have been conducted on a copper/water wire plate micro heat pipe (MHP). The experimental results show that its effective thermal conductivity is improved by a factor 1.3 as compared to the empty MHP array. A numerical model is used to predict the fluid distribution along the MHP axis, the temperature field and the maximum heat flux corresponding to the MHP capillary limit. The 1D, steady-state hydrodynamic model is based on the conservation equations for the liquid and vapour phases. The wall temperatures are calculated from the thermal resistance network of the wall and the liquid film. A good agreement between the theoretical and experimental data is achieved. The effect of various parameters - contact angle, fluid type, corner angle, fill charge - is theoretically investigated. (authors)

  18. Experimental and theoretical analysis of the local condensation heat transfer in a plate heat exchanger

    International Nuclear Information System (INIS)

    Plate heat exchanger (PHE) are today widely used in industrial heat transfer applications due to their good thermal performance, modest space requirement, easy accessibility to all areas and their lower capital and operating costs as compared to shell-and-tube heat exchangers. Although authoritative models for the design of PHE used as condensers are missing, the number of applications where a PHE is operating as a condenser increases. On the way to a reliable model based on physical approaches for the prediction of heat transfer and pressure drop during the condensation process inside a PHE, the flow and heat interactions as well as their dependence on the geometrical parameters of the corrugated plates and the operating conditions must be studied in detail. In this work the stepwise procedure for the fundamental construction of such a model is described. An experimental setup was built to analyze the characteristics of the two-phase-flow in PHE. A single gap, consisting of two transparent corrugated plates, was tested with a two-phase flow of air/water and also with boiling refrigerant R365mfc. Flow pattern maps were constructed for plates with corrugation angles of 27 and 63 degrees relative to the direction of flow. Investigations of the local heat transfer coefficients and the pressure drop were done with the same plates. The measurement of the local heat transfer coefficients was carried out by the use of the 'Temperature Oscillation InfraRed Thermography' (TOIRT) method. Based on these results three main flow patterns are defined: film flow, bubbly flow and slug flow. For each of the three flow patterns an own model for the heat transfer and pressure drop mechanism are developed and the heat transfer coefficient and the friction factor is calculated with different equations depending on the actual steam quality, mass flow and geometrical parameters by means of a flow pattern map. The theory of the flow pattern based prediction models is proved with own

  19. Experimental and theoretical analysis of the local condensation heat transfer in a plate heat exchanger

    Science.gov (United States)

    Grabenstein, V.; Kabelac, S.

    2012-11-01

    Plate heat exchanger (PHE) are today widely used in industrial heat transfer applications due to their good thermal performance, modest space requirement, easy accessibility to all areas and their lower capital and operating costs as compared to shell-and-tube heat exchangers. Although authoritative models for the design of PHE used as condensers are missing, the number of applications where a PHE is operating as a condenser increases. On the way to a reliable model based on physical approaches for the prediction of heat transfer and pressure drop during the condensation process inside a PHE, the flow and heat interactions as well as their dependence on the geometrical parameters of the corrugated plates and the operating conditions must be studied in detail. In this work the stepwise procedure for the fundamental construction of such a model is described. An experimental setup was built to analyze the characteristics of the two-phase-flow in PHE. A single gap, consisting of two transparent corrugated plates, was tested with a two-phase flow of air/water and also with boiling refrigerant R365mfc. Flow pattern maps were constructed for plates with corrugation angles of 27 and 63 degrees relative to the direction of flow. Investigations of the local heat transfer coefficients and the pressure drop were done with the same plates. The measurement of the local heat transfer coefficients was carried out by the use of the "Temperature Oscillation InfraRed Thermography" (TOIRT) method. Based on these results three main flow patterns are defined: film flow, bubbly flow and slug flow. For each of the three flow patterns an own model for the heat transfer and pressure drop mechanism are developed and the heat transfer coefficient and the friction factor is calculated with different equations depending on the actual steam quality, mass flow and geometrical parameters by means of a flow pattern map. The theory of the flow pattern based prediction models is proved with own

  20. Experimental study and analysis of a novel multi-media plate heat exchanger

    Institute of Scientific and Technical Information of China (English)

    SONG JiWei; WANG Fei; CHENG Lin

    2012-01-01

    The experimental study and analysis of a novel multi-media plate heat exchanger were performed in this paper.This novel multi-media plate heat exchanger was self-developed during the process of the investigation and design of the alpha magnetic spectrometer (AMS) thermal system.The plate of this kind of novel plate heat exchanger is formed by discontinuous structure wave consisting of convex sphere and concave sphere,its heat transfer performance is better than that of the BRI chevron plate heat exchanger,and its resistance characteristics are superior to those of the nornally used 60-degree plate heat exchanger.Furthermore,the mechanism analysis of heat transfer enhancement shows that the spherical wave structure can reduce the local field synergy angle,so as to improve the field synergy degree of velocity vector and temperature gradient vector.

  1. Flow boiling heat transfer of ammonia/water mixture in a plate heat exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Taboas, Francisco [Universidad de Cordoba, Campus de Rabanales, Edificio Leonardo da Vinci, 14014 Cordoba (Spain); Valles, Manel; Bourouis, Mahmoud; Coronas, Alberto [CREVER - Universitat Rovira i Virgili, Av. Paisos Catalans No. 26, 43007 Tarragona (Spain)

    2010-06-15

    The objective of this work is to contribute to the development of plate heat exchangers as desorbers for ammonia/water absorption refrigeration machines driven by waste heat or solar energy. In this study, saturated flow boiling heat transfer and the associated frictional pressure drop of ammonia/water mixture flowing in a vertical plate heat exchanger is experimentally investigated. Experimental data is presented to show the effects of heat flux between 20 and 50 kW m{sup -2}, mass flux between 70 and 140 kg m{sup -2} s{sup -1}, mean vapour quality from 0.0 to 0.22 and pressure between 7 and 15 bar, for ammonia concentration between 0.42 and 0.62. The results show that for the selected operating conditions, the boiling heat transfer coefficient is highly dependent on the mass flux, whereas the influence of heat flux and pressure are negligible mainly at higher vapour qualities. The pressure drop increases with increasing mass flux and quality. However, the pressure drop is independent of the imposed heat flux. (author)

  2. Microstructural characteristics of WC-Co and tool steel brazed joint

    Energy Technology Data Exchange (ETDEWEB)

    Young-Sub, K.; Sook-Hwan, K. [Reliability Assessment Team, Research Institute of Industrial Science and Technology, Pohang (Korea)

    2001-07-01

    The current study used Ni base alloys, which reveals the excellent high temperature properties, as filler metals for brazing of WC-Co and tool steel to get the solid joint strength. The strength and the microstructures of brazed joints for different filler metals were examined. The optimum brazing condition and heat treatment condition were obtained through precipitation reaction and microstructural characteristics at the joints. (orig.)

  3. FLOW RESISTANCE AND HEAT TRANSFER CHARACTERISTICS OF A NEW-TYPE PLATE HEAT EXCHANGER

    Institute of Scientific and Technical Information of China (English)

    LUAN Zhi-jian; ZHANG Guan-min; TIAN Mao-cheng; FAN Ming-xiu

    2008-01-01

    A new-type corrugation Plate Heat Exchanger (PHE) was designed. Results from both numerical simulations and experiments showed that the flow resistance of the working fluid in this new corrugation PHE, compared with the traditional chevron-type one, was decreased by more than 50%, and corresponding heat transfer performance was decreased by about 25%. The flow field of the working fluid in the corrugation PHE was transformed and hence performance difference in both flow resistance and heat transfer was generated. Such a novel plate, consisting of longitudinal and transverse corrugations, can effectively avoid the problem of flow path blockage, which will help to extend the application of PHEs to the situation with unclean working fluids.

  4. Enhanced corrosion protection by microstructural control of aluminium brazing sheet

    NARCIS (Netherlands)

    Norouzi Afshar, F.

    2013-01-01

    Aluminium brazing sheet is a sandwich material made out of two aluminium alloys (AA4xxx/AA3xxx) and is widely used in automotive heat exchangers. One of the main performance criteria for heat exchanger units is the lifetime of the product. The lifetime of the heat exchanger units is determined by th

  5. Laser brazing with filler wire for galvanized steel sheets

    Institute of Scientific and Technical Information of China (English)

    Feng Xiaosong; Li Liqun; Chen Yanbin; Zhou Shanbao

    2005-01-01

    The process properties and interface behavior of CO2 laser brazing with automatic wire feed for galvanized steel sheets were investigated , in which the brazing filler metal was CuSi3 and no flux was used. As to the appearance quality of the brazing seams, the roles of the processing parameters, such as brazing speed, wire feeding rate, inclination and feeding direction of the wire, laser power, spot diameter and heating position, were assessed. The further investigation indicates that the behavior of the active elements Si, Mn and Zn are significantly influenced by energy input. At the interface, the microstructure of the base metal was composed of columnar crystals and the acicalar α solid solution was found on the filler metal side.

  6. Properties of steel plate reinforced concrete bearing wall subjected to high heat

    International Nuclear Information System (INIS)

    Steel plate used to face SC structures heats quickly in rapid increased atmosphere temperature. Such heating could crack concrete components or buckle steel plate. We conducted heating tests with an SC structure model and found that if the temperature rises 300degC from room temperature, the SC structure cracks concrete components but does not buckle steel plate. The result shows the integrity of SC structures. (author)

  7. Estimation of pressure drop in gasket plate heat exchangers

    Directory of Open Access Journals (Sweden)

    Neagu Anisoara Arleziana

    2016-06-01

    Full Text Available In this paper, we present comparatively different methods of pressure drop calculation in the gasket plate heat exchangers (PHEs, using correlations recommended in literature on industrial data collected from a vegetable oil refinery. The goal of this study was to compare the results obtained with these correlations, in order to choose one or two for practical purpose of pumping power calculations. We concluded that pressure drop values calculated with Mulley relationship and Buonopane & Troupe correlation were close and also Bond’s equation gave results pretty close to these but the pressure drop is slightly underestimated. Kumar correlation gave results far from all the others and its application will lead to oversize. In conclusion, for further calculations we will chose either the Mulley relationship or the Buonopane & Troupe correlation.

  8. The experiment progress of bracket brazing to SSMIC for the ITER ELM prototype coil

    International Nuclear Information System (INIS)

    Highlights: • In this study, the experimental research of brackets brazing to stainless steel jacketed, Mineral Insulated Conductor (SSMIC) of the first Edge Localized Modes (ELMs) prototype coil for ITER has been made. • The technology for controlling the fluidity of silver-based brazing alloy is developed to meet the bracket brazing. • Brazing experiments to find the reason for cracks are carried out and the improved brazing technologies to restrain the cracks in the Inconel 625 jacket with silver-based alloy are developed. - Abstract: The first Edge Localized Modes (ELMs) prototype coil for International Thermonuclear Experimental Reactor (ITER) has been manufactured in the Institute of Plasma Physics, CAS (ASIPP) at 2014. The all 19 brackets need to braze to the stainless steel jacketed, Mineral Insulated Conductor (SSMIC) for transporting the nuclear heating in the brackets to the water-cooled SSMIC. Silver-based alloy is the only candidate brazing filler for the bracket brazing due to the limitation from melting point temperature and strength. In this paper, firstly, the experimental study for controlling the fluidity of silver-based brazing alloy is developed. And then, the brazing experiment of prototype bracket is introduced to develop the brazing process and some cracks in the Inconel 625 jackets surface appeared unexpectedly. The microstructures and tensile performance study of the cracked Inconel 625 jacket were made to explore the reason for cracks and the improved brazing technologies to suppress the cracks are developed. Finally, the bracket brazing experiment for the first ELM prototype coil is carried out, In spite of this, some cracks also appear in the Inconel 625 jackets

  9. Brazing zone structure at active brazing of alumina ceramics

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    @@ Nowadays one of the most effective methods of joining of oxide ceramics with other elements of construction is active brazing based on using of active metals (Ti, Zr), which increase reactivity of brazing alloy relative to ceramic element of a joining.

  10. Advances in brazing science, technology and applications

    CERN Document Server

    2013-01-01

    Brazing processes offer enhanced control, adaptability and cost-efficiency in the joining of materials. Unsurprisingly, this has lead to great interest and investment in the area. Drawing on important research in the field, Advances in brazing provides a clear guide to the principles, materials, methods and key applications of brazing. Part one introduces the fundamentals of brazing, including molten metal wetting processes, strength and margins of safety of brazed joints, and modeling of associated physical phenomena. Part two goes on to consider specific materials, such as super alloys, filler metals for high temperature brazing, diamonds and cubic boron nitride, and varied ceramics and intermetallics. The brazing of carbon-carbon (C/C) composites to metals is also explored before applications of brazing and brazed materials are discussed in part three. Brazing of cutting materials, use of coating techniques, and metal-nonmetal brazing for electrical, packaging and structural applications are reviewed, alon...

  11. A Novel Heat Pipe Plate for Passive Thermal Control of Fuel Cells Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR project aims to develop a lightweight, highly thermally and electrically conductive heat pipe plate for passive removal of the heat from the individual...

  12. Preliminary Process Design of ITER ELM Coil Bracket Brazing

    Science.gov (United States)

    LI, Xiangbin; SHI, Yi

    2015-03-01

    With the technical requirement of the International Thermonuclear Experimental Reactor (ITER) project, the manufacture and assembly technology of the mid Edge Localized Modes (ELM) coil was developed by the Institute of Plasma Physics, Chinese Academy of Science (ASIPP). As the gap between the bracket and the Stainless Steel jacketed and Mineral Insulated Conductor (SSMIC) can be larger than 0.5 mm instead of 0.01 mm to 0.1 mm as in normal industrial cases, the process of mid ELM coil bracket brazing to the SSMICT becomes quiet challenging, from a technical viewpoint. This paper described the preliminary design of ELM coil bracket brazing to the SSMIC process, the optimal bracket brazing curve and the thermal simulation of the bracket furnace brazing method developed by ANSYS. BAg-6 foil (Bag50Cu34Zn16) plus BAg-1a paste (Bag45CuZnCd) solders were chosen as the brazing filler. By testing an SSMICT prototype, it is shown that the average gap between the bracket and the SSMIC could be controlled to 0.2-0.3 mm, and that there were few voids in the brazing surface. The results also verified that the preliminary design had a favorable heat conducting performance in the bracket.

  13. A preliminary study of cladding steel with NiTi by microwave-assisted brazing

    International Nuclear Information System (INIS)

    Nickel titanium (NiTi) plate of 1.2 mm thickness was successfully clad on AISI 316L stainless steel substrate by a microwave-assisted brazing process. Brazing was conducted in a multimode microwave oven in air using a copper-based brazing material in tape form. The brazing material was melted in a few minutes by microwave-induced plasma initiated by conducting wires surrounding the brazing assembly. Metallographic study by scanning-electron microscopy (SEM) and compositional analysis by energy-dispersive spectroscopy (EDS) of the brazed joint revealed metallurgical bonding formed via inter-diffusion between the brazing filler and the adjacent materials. A shear bonding strength in the range of 100-150 MPa was recorded in shear tests of the brazed joint. SEM and X-ray diffractometry (XRD) analysis for the surface of as-received NiTi plate and NiTi cladding showed similar microstructure and phase composition. Nanoindentation tests also indicated that the superelastic properties of NiTi were essentially retained. The cavitation erosion resistance of the NiTi cladding was essentially the same as that of as-received NiTi plate, and higher than that obtained in laser or TIG (tungsten-inert gas) surfacing. The high resistance could be attributed to avoidance of dilution and defect formation in the NiTi clad since the cladding did not undergo melting and solidification in the brazing process. Electrochemical tests also recorded similar corrosion resistance in both as-received NiTi and NiTi cladding. Thus, the present study indicates that microwave-assisted brazing is a simple, economical, and feasible process for cladding NiTi on 316L stainless steel for enhancing cavitation erosion resistance

  14. A preliminary study of cladding steel with NiTi by microwave-assisted brazing

    Energy Technology Data Exchange (ETDEWEB)

    Chiu, K.Y. [Department of Applied Physics, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China); Cheng, F.T. [Department of Applied Physics, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China)]. E-mail: apaftche@polyu.edu.hk; Man, H.C. [Department of Industrial and Systems Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China)

    2005-10-25

    Nickel titanium (NiTi) plate of 1.2 mm thickness was successfully clad on AISI 316L stainless steel substrate by a microwave-assisted brazing process. Brazing was conducted in a multimode microwave oven in air using a copper-based brazing material in tape form. The brazing material was melted in a few minutes by microwave-induced plasma initiated by conducting wires surrounding the brazing assembly. Metallographic study by scanning-electron microscopy (SEM) and compositional analysis by energy-dispersive spectroscopy (EDS) of the brazed joint revealed metallurgical bonding formed via inter-diffusion between the brazing filler and the adjacent materials. A shear bonding strength in the range of 100-150 MPa was recorded in shear tests of the brazed joint. SEM and X-ray diffractometry (XRD) analysis for the surface of as-received NiTi plate and NiTi cladding showed similar microstructure and phase composition. Nanoindentation tests also indicated that the superelastic properties of NiTi were essentially retained. The cavitation erosion resistance of the NiTi cladding was essentially the same as that of as-received NiTi plate, and higher than that obtained in laser or TIG (tungsten-inert gas) surfacing. The high resistance could be attributed to avoidance of dilution and defect formation in the NiTi clad since the cladding did not undergo melting and solidification in the brazing process. Electrochemical tests also recorded similar corrosion resistance in both as-received NiTi and NiTi cladding. Thus, the present study indicates that microwave-assisted brazing is a simple, economical, and feasible process for cladding NiTi on 316L stainless steel for enhancing cavitation erosion resistance.

  15. Prediction of deformations of steel plate by artificial neural network in forming process with induction heating

    International Nuclear Information System (INIS)

    To control a heat source easily in the forming process of steel plate with heating, the electro-magnetic induction process has been used as a substitute of the flame heating process. However, only few studies have analyzed the deformation of a workpiece in the induction heating process by using a mathematical model. This is mainly due to the difficulty of modeling the heat flux from the inductor traveling on the conductive plate during the induction process. In this study, the heat flux distribution over a steel plate during the induction process is first analyzed by a numerical method with the assumption that the process is in a quasi-stationary state around the inductor and also that the heat flux itself greatly depends on the temperature of the workpiece. With the heat flux, heat flow and thermo-mechanical analyses on the plate to obtain deformations during the heating process are then performed with a commercial FEM program for 34 combinations of heating parameters. An artificial neural network is proposed to build a simplified relationship between deformations and heating parameters that can be easily utilized to predict deformations of steel plate with a wide range of heating parameters in the heating process. After its architecture is optimized, the artificial neural network is trained with the deformations obtained from the FEM analyses as outputs and the related heating parameters as inputs. The predicted outputs from the neural network are compared with those of the experiments and the numerical results. They are in good agreement

  16. Evaporation Heat Transfer of Ammonia and Pressure Drop of Warm Water for Plate Type Evaporator

    Science.gov (United States)

    Kushibe, Mitsuteru; Lkegami, Yasuyuki; Monde, Masanori; Uehara, Haruo

    The performance test of three types of plate type evaporators for spring thermal energy conversion and ocean thermal energy conversion carried out. Ammonia is utilized as working fluid and warm water is utilized as heat source. An empirical correlation is proposed in order to predict the mean evaporation heat transfer coefficient of ammonia and heat transfer coefficient of warm water for plate type evaporators. The mean heat transfer coefficient and friction factor of warm water were compared with other researches.

  17. Heat Conduction in a Functionally Graded Plate Subjected to Finite Cooling/Heating Rates: An Asymptotic Solution

    Directory of Open Access Journals (Sweden)

    Zhihe Jin

    2011-12-01

    Full Text Available This work investigates transient heat conduction in a functionally graded plate (FGM plate subjected to gradual cooling/heating at its boundaries. The thermal properties of the FGM are assumed to be continuous and piecewise differentiable functions of the coordinate in the plate thickness direction. A linear ramp function describes the cooling/heating rates at the plate boundaries. A multi-layered material model and Laplace transform are employed to obtain the transformed temperatures at the interfaces between the layers. An asymptotic analysis and an integration technique are then used to obtain a closed form asymptotic solution of the temperature field in the FGM plate for short times. The thermal stress intensity factor (TSIF for an edge crack in the FGM plate calculated based on the asymptotic temperature solution shows that the asymptotic solution can capture the peak TSIFs under the finite cooling rate conditions.

  18. How braze flaws affect the thermal-hydraulic performance of the Tore Supra Phase-III outboard pump limiter. A case study of the effects of nonuniform thermal resistance on the peak heat flux to the coolant for tubes with one-sided heating

    International Nuclear Information System (INIS)

    The phase-III Outboard Pump Limiter is a heat sink made of pyrolytic graphite armor brazed to water-cooled copper tubes. Around the inner wall of the tube wall, some of the water can be in the subcooled boiling regime. The central issue analyzed here is how the heat flow in the tube changes when the thermal resistance along the heated portion of the tube is redistributed. Cracks or braze flaws in the joint between the tile and tube cause this redistribution. Severe cracks or flaws reduce the power-handling capability of this assembly because the local peak heat fluxes increase and, for a given critical heat flux (CHF), the safety margin decreases. There were some surprises. The increase in local peak heat flux for the most common type of flaw encountered in the fabrication of this limiter was negligible up to a flaw size of nearly 50%. The examples presented are intended as a case study that illuminates the more general problem of how correlations for heat transfer and for CHF developed for uniform circumferential heating are applied to a case of one-sided heating. 17 refs., 19 figs., 1 tab

  19. Plate heat exchanger - inertia flywheel performance in loss of flow transient

    Energy Technology Data Exchange (ETDEWEB)

    Abou-El-Maaty, Talal; Abd-El-Hady, Amr [Atomic Energy Authority, Cairo (Egypt). Reactors Dept.

    2009-04-15

    One of the most versatile types of heat exchangers used is the plate heat exchanger. It has principal advantages over other heat exchangers in that plates can be added and/or removed easily in order to change the area available for heat transfer and therefore its overall performance. The cooling systems of Egypt's second research reactor (ETRR 2) use this type of heat exchanger for cooling purposes in its primary core cooling and pool cooling systems. In addition to the change in the number of heat exchanger cooling channels, the effect of changing the amount of mass flow rate on the heat exchanger performance is an important issues in this study. The inertia flywheel mounted on the primary core cooling system pump with the plate heat exchanger plays an important role in the case of loss of flow transients. The PARET code is used to simulate the effect of loss of flow transients on the reactor core. Hence, the core outlet temperature with the pump-flywheel flow coast down is fed into the plate heat exchanger model developed to estimate the total energy transferred to the cooling tower, the primary side heat exchanger temperature variation, the transmitted heat exchanger power, and the heat exchanger effectiveness. In addition, the pressure drop in both, the primary side and secondary side of the plate heat exchanger is calculated in all simulated transients because their values have limits beyond which the heat exchanger is useless. (orig.)

  20. Liquid cooled plate heat exchanger for battery cooling of an electric vehicle (EV)

    Science.gov (United States)

    Rahman, M. M.; Rahman, H. Y.; Mahlia, T. M. I.; Sheng, J. L. Y.

    2016-03-01

    A liquid cooled plate heat exchanger was designed to improve the battery life of an electric vehicle which suffers from premature aging or degradation due to the heat generation during discharging and charging period. Computational fluid dynamics (CFD) was used as a tool to analyse the temperature distribution when a constant surface heat flux was set at the bottom surface of the battery. Several initial and boundary conditions were set based on the past studies on the plate heat exchanger in the simulation software. The design of the plate heat exchanger was based on the Nissan Leaf battery pack to analyse the temperature patterns. Water at different mass flow rates was used as heat transfer fluid. The analysis revealed the designed plate heat exchanger could maintain the surface temperature within the range of 20 to 40°C which is within the safe operating temperature of the battery.

  1. Charge distribution in a 5 kW heat pump using propane as working fluid : Part II: Modelling of liquid hold-up

    OpenAIRE

    Samoteeva, Oxana; Fernando, Primal; Palm, Björn; Lundqvist, Per

    2001-01-01

    A theoretical model for prediction of the amount of refrigerant in condenser and evaporator of a 5kW capacity heat pump is developed. Condenser and evaporator of the experimental test rig are SWEP Brazed Plate Heat Exchangers (BPHE). Plate heat exchangers are widely used in refrigeration and heat pump applications today. However, the mechanisms of boiling and condensation in BPHE represent a difficult issue, for which only few models are developed and presented in published literature. The mo...

  2. NUMERICAL STUDY ON FLOW DISTRIBUTION IN PLATE-FIN HEAT EXCHANGERS

    Institute of Scientific and Technical Information of China (English)

    张哲; 厉彦忠

    2003-01-01

    Objective To investigate the flow distribution in plate-fin heat exchangers and optimize the design of header configuration for plate-fin heat exchangers. Methods A mathematical model of header was proposed. The effects of the header configuration on the flow distribution in plate-fin heat exchangers were investigated by CFD. The second header configuration with a two-stage-distributing structure was brought forward to improve the performance of flow distribution. Results It is found that the flow maldistribution is very serious in the direction of header length for the conventional header used in industry. The numerical predictions indicate that the improved header configurations can effectively improve the performance of flow distribution in plate-fin heat exchangers. Conclusion The numerical simulation confirms that CFD should be a suitable tool for predicting the flow distribution. The method has a wide variety of applications in the design of plate-fin heat exchangers.

  3. Brazing technology of Ti alloy/stainless steel dissimilar metal joint at system integrated modular advanced reactor

    International Nuclear Information System (INIS)

    For the technoldogy development of brazing Ti alloy to stainless steel joints used at SMART, the status of brazing technology development, brazing processes, and the brazing technology of Ti alloy and stainless steel are reviewed. Because fusion welding process cannot be applied due to the formation of intermetallic compounds in the weld metal, brazing joint was selected at the design. The joint part is assembled with a thread composed with male part of Ti alloy tube and female part of stainless tube. The gap in the thread will be filled with brazing filler metal. However, brittle Ti-Fe intermetallic compounds are formed at the surface of stainless steel through the diffusion of Ti at the melt. Brazing conditions should be set-up to reduce the formation of intermetallic compounds. For that, 3 kinds of Ag filler metals were selected as the candidates and heating will be done with induction and electric furnaces. Through measuring of joint strength according to the control of pre- and post-braze treatment, heating rate and heating time, optimal brazing method will be fixed. To qualify the brazing procedure and performance and to check defects in final product, the inspection plan will be established according to the req2wuirements of AWS and ASME

  4. The effect of heat generation in inclined slats on the natural convective heat transfer from an isothermal heated vertical plate

    International Nuclear Information System (INIS)

    Natural convective heat transfer from a wide heated vertical isothermal plate with adiabatic surfaces above and below the heated surface has been considered. There are a series of equally spaced vertical thin, flat surfaces (termed 'slats') near the heated surface, these surfaces being, in general, inclined to the heated surface. There is, in general, a uniform heat generation in the slats. The slats are pivoted about their centre-point and thus as their angle is changed, the distance of the tip of the slat from the plate changes. The situation considered is an approximate model of a window with a vertical blind, the particular case where the window is hotter than the room air being considered. The heat generation in the slats in this situation is the result of solar radiation passing through the window and falling on and being absorbed by the slats of the blind. The flow has been assumed to be laminar and steady. Fluid properties have been assumed constant except for the density change with temperature that gives rise to the buoyancy forces. The governing equations have been written in dimensionless form and the resulting dimensionless equations have been solved using a commercial finite-element package. The solution has the following parameters: (1) the Rayleigh number (2) the Prandtl number (3) the dimensionless heat generation rate in the slats per unit frontal area (4) the dimensionless distance of the slat center point (the pivot point) from the surface (5) the dimensionless slat size (6) the dimensionless slat spacing (7) the angle of inclination of the slats. Because of the application that motivated the study, results have only been obtained for a Prandtl number of 0.7. The effect of the other dimensionless variables on the mean dimensionless heat transfer rate from the heated vertical surface has been examined. (author)

  5. Soil profile method for soil thermal diffusivity, conductivity and heat flux:Comparison to soil heat flux plates

    Science.gov (United States)

    Diffusive heat flux at the soil surface is commonly determined as a mean value over a time period using heat flux plates buried at some depth (e.g., 5 to 8 cm) below the surface with a correction to surface flux based on the change in heat storage during the corresponding time period in the soil lay...

  6. Transient conjugated mixed-convective heat transfer in a vertical plate channel with one wall heated discretely

    Science.gov (United States)

    Tsay, Y. L.

    This study presents a numerical solution of the unsteady conjugated mixed-convection heat transfer in a vertical plate channel with one wall suddenly subjected to either isoflux or isothermal discrete heat sources. The effects of the dimensionless heat source length H1, the dimensionless spacing between heat sources H2, the dimensionless channel length L, the dimensionless heated-plate thickness Bl, the wall-to-fluid conductivity ratio K and the ratio of Grashof number to Reynolds number Gr/Re on the interface heat flux, Nusselt number and bulk fluid temperature are discussed in detail. Results show that the discrete heating can cause the heat transfer direction conversely from the fluid to the heated plate during the transient period, which is more significant for the cases with larger L and H2. For the system with isoflux discrete heat sources, the time required to reach the steady-state is shorter for larger H2. While the trend is reverse for system with isothermal discrete heat sources. Additionally, a higher ratio of the input energy is axially conducted through the plate wall from heated sections to unheated regions for a larger H2 and Bl or smaller L.

  7. Transient conjugated mixed-convective heat transfer in a vertical plate channel with one wall heated discretely

    Energy Technology Data Exchange (ETDEWEB)

    Tsay, Y.L. [Dept. of Aeronautical Engineering National Huwei Institute of Technology Huwei, Yuenlin (Taiwan)

    1999-10-01

    This study presents a numerical solution of the unsteady conjugated mixed-convection heat transfer in a vertical plate channel with one wall suddenly subjected to either isoflux or isothermal discrete heat sources. The effects of the dimensionless heat source length H{sub 1}, the dimensionless spacing between heat sources H{sub 2}, the dimensionless channel length L, the dimensionless heated-plate thickness B{sub l}, the wall-to-fluid conductivity ratio K and the ratio of Grashof number to Reynolds number Gr/Re on the interface heat flux, Nusselt number and bulk fluid temperature are discussed in detail. Results show that the discrete heating can cause the heat transfer direction conversely from the fluid to the heated plate during the transient period, which is more significant for the cases with larger L and H{sub 2}. For the system with isoflux discrete heat sources, the time required to reach the steady-state is shorter for larger H{sub 2}. While the trend is reverse for system with isothermal discrete heat sources. Additionally, a higher ratio of the input energy is axially conducted through the plate wall from heated sections to unheated regions for a larger H{sub 2} and B{sub l} or smaller L. (orig.)

  8. Analysis of Heat Transfer Behaviour of the Conduction Cold Plate System

    Institute of Scientific and Technical Information of China (English)

    YangChun-xin; DangChao-Bin

    1995-01-01

    The heat-transfer behaviour of the conduction cold plate system used for avionics is investigated in this paper.The steady-state temperature profile for the cold plate is derived and the relationship between the coolant mass flowrate,the heat load and the highest cold plate temperature is established.A model is proposed to describe the transient thermal rosponse of the cold plate under thermal shock condition.The analytic solution of the transient heat transfer within the cold plate is provided.The results of this paper agree with those of the finite element method and can be used for the structural design and performance evaluation of cold plate system.

  9. Mixed convection flow over a vertical plate with localized heating (cooling), magnetic field and suction (injection)

    OpenAIRE

    Chamkha, AJ; Takhar, HS; G. Nath

    2004-01-01

    An analysis is carried out to study the effects of localized heating (cooling), suction (injection), buoyancy forces and magnetic field for the mixed convection flow on a heated vertical plate. The localized heating or cooling introduces a finite discontinuity in the mathematical formulation of the problem and increases its complexity. In order to overcome this difficulty, a non-uniform distribution of wall temperature is taken at finite sections of the plate. The nonlinear coupled parabolic ...

  10. Modeling, Designing, Fabricating, and Testing of Channel Panel Flat Plate Heat Pipes

    OpenAIRE

    Harris, James R

    2008-01-01

    Flat plate heat pipes are very efficient passive two-phase heat transport devices. Their high e'ciency and low mass are desirable in the aerospace and electronics industries. The highly competitive nature of the thermal management industry results in little awareness of the capabilities of at plate heat pipes, which has resulted in only a few applications of the technology. In the year 2000 a research and development project sponsored by Space Dynamics Laboratory was launched to investigate b...

  11. Efficiency of insulation passive system of solar heating with transforming flat plate reflector of radiation and accumulator of heat

    International Nuclear Information System (INIS)

    Key words: solar radiation, window, reflector of radiation, short-term accumulator of heat, solar heating, insulation passive system, thermal efficiency, heating building. Subjects of research: insulation passive system of solar heating with short-term accumulators of heat, combining the function of collector of solar radiation and hingedly transformed flat plate reflector for additional illumination of heating building and without them. Purpose of work: determination of real possibility of insulation passive system of solar heating with transformed flat plate reflectors of radiation and short-term accumulators of heat and on this basis development of scientific dates for experimental designing and construction of them for natural condition of Uzbekistan. Methods of research: thermal-technical calculation and experiment under natural conditions. The results obtained and their novelty: offered calculation expressions for determining of optimal inclination angle to horizon and coefficient of reflection of direct solar radiation of flat plate reflector with back reflection layer; developed and offered method of calculation of using efficiency of transformed flat plate reflectors of radiation for additional illumination of heating building in the daytime and decreasing of heat losses through window insulation passive systems of solar heating at night; optimized of specific heat of short-time accumulators of heat in insulation passive systems of solar heating; determined real thermal efficiency and replacement coefficient of thermal load to heating of proposed system by the example of operational testing this systems under conditions of Karshi City. Practical value: the results of performed investigations allow to develop the scientific basic dates on designing and marketing on climate conditions in the south of The Republic of Uzbekistan insulation passive systems of solar heating with flat plate reflectors and short-time accumulators of heat, providing to save the

  12. Heat transfer in flow past a continuously moving semi-infinite flat plate in transverse magnetic field with heat flux

    Digital Repository Service at National Institute of Oceanography (India)

    Murty, T.V.R.

    Thermal boundary layer on a continuously moving semi-infinite flat plate in the presence of transverse magnetic field with heat flux has been examined. Similarity solutions have been derived and the resulting equations are integrated numerically...

  13. Performance of a shell-and-tube heat exchanger with spiral baffle plates

    International Nuclear Information System (INIS)

    In a conventional shell-and-tube heat exchanger, fluid contacts with tubes flowing up and down in a shell, therefore there is a defect in the heat transfer with tubes due to the stagnation portions. Fins are attached to the tubes in order to increase heat transfer efficiency, but there exists a limit. Therefore, it is necessary to improve heat exchanger performance by changing the fluid flow in the shell. In this study, a highly efficient shell-and-tube heat exchanger with spiral baffle plates is simulated three-dimensionally using a commercial thermal-fluid analysis code, CFX4.2. In this type of heat exchanger, fluid contacts with tubes flowing rotationally in the shell. It could improve heat exchanger performance considerably because stagnation portions in the shell could be removed. It is proved that the shell-and-tube heat exchanger with spiral baffle plates is superior to the conventional heat exchanger in terms of heat transfer

  14. Plate Fin Heat Exchanger Model with Axial Conduction and Variable Properties

    CERN Document Server

    Hansen, B J; Klebaner, A; 10.1063/1.4706971

    2012-01-01

    Future superconducting radio frequency (SRF) cavities, as part of Project X at Fermilab, will be cooled to superfluid helium temperatures by a cryogenic distribution system supplying cold supercritical helium. To reduce vapor fraction during the final Joule-Thomson (J-T) expansion into the superfluid helium cooling bath, counter-flow, plate-fin heat exchangers will be utilized. Due to their compact size and ease of fabrication, plate-fin heat exchangers are an effective option. However, the design of compact and high-effectiveness cryogenic heat exchangers operating at liquid helium temperatures requires consideration of axial heat conduction along the direction of flow, in addition to variable fluid properties. Here we present a numerical model that includes the effects of axial conduction and variable properties for a plate fin heat exchanger. The model is used to guide design decisions on heat exchanger material choice and geometry. In addition, the J-T expansion process is modeled with the heat exchanger ...

  15. Turbulent Heat Transfer from a Flat Plate Placed Downstream of a Fence

    Directory of Open Access Journals (Sweden)

    A. K. Darmeesh

    2015-10-01

    Full Text Available This paper presents an experimental study of the heat transfer and flow friction for turbulent flows of air over a heated flat plate mounted downstream of a fence. A rectangular brass plate is attached to a heating unit and fixed inside the test section of a subsonic wind tunnel. A number of non-metallic fences with different heights are used separately to promote turbulence over the plate. A series of experiments are conducted to examine the following parameters: fence height to plate length ratio (H/L, the distance between the fence and plate relative to plate length (S/L and the Reynolds number, which is calculated based on the stream wise length of the plate (1.5×105 ≤ ReL≤ 4.5×105 . The first set of the results, which is obtained for the case of the flat plate without a fence, satisfied with other published results. The results in the cases of the plate placed downstream of a fence revealed that the Nusselt number and friction factor are critically dependent on the fence height and the distance between the fence and the plate. A maximum Nusselt number enhancement ratio of 1.7 was achieved corresponding to a friction factor ratio of 2.5. New correlation was obtained for the thermal efficiency (η based on the Nusselt number enhancement ratio and friction factor ratio at different arrangements of the considered parameters.

  16. Heat transfer processes in parallel-plate heat exchangers of thermoacoustic devices – numerical and experimental approaches

    OpenAIRE

    Artur J. Jaworski; Piccolo, Antonio

    2012-01-01

    This paper addresses the issues of heat transfer in oscillatory flow conditions, which are typically found in thermoacoustic devices. The analysis presented concerns processes taking place in the individual "channels" of the parallel-plate heat exchangers (HX), and is a mixture of experimental and numerical approaches. In the experimental part, the paper describes the design of experimental apparatus to study the thermal-fluid processes controlling heat transfer in thermoacoustic heat exchang...

  17. Vacuum Brazing of Beryllium Copper Components for the National Ignition Facility

    International Nuclear Information System (INIS)

    A process for vacuum brazing beryllium copper anode assemblies was required for the Plasma Electrode Pockels Cell System, or PEPC, a component for the National Ignition Facility (NIF). Initial problems with the joint design and wettability of the beryllium copper drove some minor design changes. Brazing was facilitated by plating the joint surface of the beryllium copper rod with silver 0.0006 inch thick. Individual air sampling during processing and swipe tests of the furnace interior after brazing revealed no traceable levels of beryllium

  18. Three-Dimensional Numerical Simulation of Plate Forming by Line Heating

    DEFF Research Database (Denmark)

    Clausen, Henrik Bisgaard

    Line Heating is the process of forming (steel) plates into shape by means of localised heating often along a line. Though any focussed heat source will do, the inexpensive and widely available oxyacettylene gas torch is commonly applied in ship production.Over the years, many researchers have add...

  19. Detailed analysis for the cooling performance enhancement of a heat source under a thick plate

    International Nuclear Information System (INIS)

    Highlights: • Attachment of a heat source to a thick plate is examined. • It is shown that the thick plate improves cooling performance. • Improvement of cooling performance is indicated by reducing the peak temperature. • It is proved that there is an optimal thickness of the thick plate. • Optimization is carried out based on numerical work via SIMPLEC algorithm. - Abstract: Maintaining the peak temperature of a heat source under an allowable level has always been a major concern for engineers engaged in the design of cooling systems for electronic equipment. The primary goal of this paper is to examine the advantages and/or disadvantages of placing a conductive thick plate as a heat transfer interface between a heat source and a cold flowing fluid. In such arrangement, the heat source is cooled under the thick plate instead of being cooled in direct contact with the cooling fluid. It is demonstrated that the thick plate can significantly improve the heat transfer between the heat source and the cooling fluid by way of conducting the heat current in an optimal manner. The two most attractive advantages of this method are that no additional pumping power and no extra heat transfer surface area, that is quite different from fins (extended surfaces). Unlike related archival papers in the literature, the present paper allows open spaces toward optimization. The objective is to minimize the maximum temperature, the ‘hot spot’. Detailed analytical expressions are presented and a numerical analysis is carried out on the conservation equations based on the SIMPLEC algorithm. It is categorically proved that there exists an optimal thickness of the thick plate, which minimizes the peak temperature. Also, it is shown that the efficiency of the optimized plate on minimizing the target peak temperature depends upon the Reynolds number of the fluid flow and the material thermal conductivity

  20. Joining of beryllium by braze welding technique: preliminary results

    Energy Technology Data Exchange (ETDEWEB)

    Banaim, P.; Abramov, E. [Ben-Gurion Univ. of the Negev, Beersheba (Israel); Zalkind, S.; Eden, S.

    1998-01-01

    Within the framework of some applications, there is a need to join beryllium parts to each other. Gas Tungsten Arc Braze Welds were made in beryllium using 0.3 mm commercially Aluminum (1100) shim preplaced at the joint. The welds exhibited a tendency to form microcracks in the Fusion Zone and Heat Affected Zone. All the microcracks were backfilled with Aluminum. (author)

  1. Role of plate-driven mantle flow in distribution of the global heat flow

    Institute of Scientific and Technical Information of China (English)

    叶正仁; 安镇文

    1999-01-01

    Heat flow in the Earth, from its hot interior to its relatively cool exterior, is the primary energy flow responsible for the dynamic nature of our planet. The motion of the plates excites a forced convective motion in the mantle, and this plate-driven mantle flow will strongly modulate the temperature field in the mantle because of the relatively high Peeler number of the mantle dynamic system. Here the role of the plate-driven mantle flow in the observed global heat flow is examined. The result reveals that the main feature of the distribution of the observed heat flow at the surface of the Earth matches well with the prediction and nearly one half of the average heat flow can be attributed to the thermal effect of the plate-driven mantle flow.

  2. Hydrogen embrittlement of welded joints for the heat-treatable XABO 960 steel heavy plates

    OpenAIRE

    M. Opiela

    2010-01-01

    Purpose: In the paper, influence of hydrogen on mechanical properties of welded joints from heat-treatable structural XABO 960 steel plates was investigated.Design/methodology/approach: The heat treatment of welded plate specimens was performed, and then the specimens were charged with hydrogen electrolytically generated from 1 N H2SO4 solution. The following studies were carried out: static tensile test, hardness investigations, macroscopic metallographic investigations as well as investigat...

  3. Experimental study of a water-mist jet issuing normal to a heated flat plate

    OpenAIRE

    Vouros Andreas; Vouros Alexandros; Panidis Thrassos

    2016-01-01

    A parametric experimental study on the development of a round jet spray impacting a smooth, heated, flat plate has been accomplished. The main objective of this effort was to provide information characterizing the flow structure of a developing mist jet, issuing vertically towards an upward facing, horizontal heated plate, by means of simultaneous droplet size and velocity measurements. Phase Doppler Anemometry was used, providing also information on liquid...

  4. Experimental heat transfer on the windward surface of a perforated flat plate

    Energy Technology Data Exchange (ETDEWEB)

    Dorignac, E.; Vullierme, J.J.; Broussely, M.; Foulon, C.; Mokkadem, M. [Laboratoire d' Etudes Thermiques, UMR CNRS 6608, Ecole Nationale Superieure de Mecanique et d' Aerotechnique, 1, Av. Clement Ader BP 40109, 86961 Futuroscope Chasseneuil cedex (France)

    2005-09-01

    Two techniques are described in this paper to determine convective transfer on a multi-perforated plate; the perforations diameter can be small or large (from 1 millimeter to 1 centimeter). This study reports on heat transfer due to the air flow before it goes through the perforations. These perforations are perpendicular to the wall. For a large range of perforations spacings, an empirical relation is proposed for heat exchange at the windward surface of a perforated flat plate. (authors)

  5. Numerical analysis of non-isothermal Newtonian flows in plate heat exchangers

    OpenAIRE

    Carla S. Fernandes; Dias, Ricardo P.; Nóbrega, João M.; Maia, João M.; Wadekar, Vishwas V.

    2005-01-01

    Plate heat exchangers (pHE's) are widely used in chemical, pharmaceutical, biochemical processing, food, and dairy industries, offering this type of equipments several advantages like the low space requirement, high efficiency, easy cleaning and maintenance, low fouling tendency and high flexibility (Reppich, 1999). Heat transfer in a PRE is strongly dependent on geometrical properties of the chevron plates, namely on corrugation angle, area enlargement factor and channel aspect r...

  6. Numerical simulation of heat transfer and fluid dynamics phenomena present in flat plate solar collectors

    OpenAIRE

    Karahasanoglu, Anil

    2013-01-01

    The objective of this work is to study the heat transfer and fluid dynamics phenomena which take place in flat plate solar collectors. The resolution of the steady and unsteady conduction in 1D and 2D domains including composite materials, Smith Hutton problem, Navier-Stokes equations and energy equation are carried out by means of numerical methods. The acquired knowledge in heat transfer and fluid flow is then applied to flat plate solar collectors. A numerical model is created to simulate ...

  7. An experimental observation of the effect of flow direction for evaporation heat transfer in plate heat exchanger

    International Nuclear Information System (INIS)

    This study provides an Infrared Thermal Image observation on the evaporation heat transfer of refrigerant R-410A in plate heat exchanger with various flow arrangement and exit superheat conditions. An experimental method was derived for estimating the superheat region area of two-phase refrigerant evaporation in plate heat exchanger. The experimental results show that the superheat region area for parallel flow is much larger than that for counter flow as that estimated by Yang et al. [9]. There is an early superheated region at the central part of the plate heat exchanger for parallel flow arrangement. This effect is not significant for counter flow arrangement. The Yang et al. [9] method under estimated the superheat area approximately 40%–53% at various flow rates and degree of exit superheat. Even though the flow inside a plate heat exchanger is extremely turbulent because of the chevron flow passages, the assumption of uniform temperature distribution in the cross section normal to the bulk flow direction will cause significant uncertainties for estimating the superheat area for refrigerant evaporating in a plate heat exchanger

  8. A reassessment of the heat transport by variable viscosity convection with plates and lids

    International Nuclear Information System (INIS)

    The heat transport by a viscous fluid with temperature dependent viscosity has been studied numerically. As opposed to previous models, the top surface of the fluid clearly defines a tectonic plate with horizontally uniform velocity and subduction. Past studies failed to incorporate plates, the heat transport is as efficient as Rayleigh-Benard convection with constant viscosity; there is a strong buffering between internal temperature and heat loss. Past studies of parameterized convection which incorporated parameters indicative of strong buffering between internal temperature and total heat output still provide the most physically plausible representation of the Earth's thermal evolution

  9. Structure and stresses in high dimension brazed joints of cermets and steel

    Directory of Open Access Journals (Sweden)

    J. Nowacki

    2012-02-01

    Full Text Available Purpose: of this paper is description of stresses in brazing joints of different physical and mechanical properties and evaluation of microstructure and mechanical properties of large dimensional vacuum brazed joints of WC–Co (ISO K05, Fe-TiC sinter plates (Ferro–Titanit Nicro 128 and precipitation hardened stainless steel of 14-5 PH (X5CrNiMoCuNb14-5 using copper as the brazing filler metal.Design/methodology/approach: Microscopic examinations with the use of scanning electron microscope were performed to establish microstructure of the joint. Shear strength Rt and tensile strength Rm of the joints have been defined.Findings: It have been state, that the basic factors decreasing strength of the joint, which can occur during vacuum brazing of the WC-Co, Fe-TiC sinters - Cu brazing filler metal - 14-5 PH steel joints are diffusive processes leading to exchange of the cermets and brazing filler metal elements. They can have an unfavourable influence on ductility and quality of the joint..Research limitations/implications: Results of numerical calculations of three-dimensional models of cermets and steel brazed joints stresses are presented. Particular attention was paid to stresses occurring in joints of large brazing surfaces. It was shown that joints microstructure and mechanical properties depend on chemical composition filler and parent materials, diffusion process during brazing, leading of the cermets and filler metal components replacement as well as joint gap thickness. The thickness of the joints and parent materials have an essential influence on the value of the local stress.Practical implications: As a result of conducted experiments criteria for generating high dimension coatings of cermets plates brazed to steel. The PM Fe-TiC and PM WC - Co composite plates vacuum-brazed to steel as cutting coatings have been worked out and applied in industry.Originality/value: An original value of the paper is to prove the tendency of

  10. Shell-and-Tube or Plate Heat Exchangers

    OpenAIRE

    Kuzma-Kichta, Y; Savelyev, P; Lodvikov, K

    2008-01-01

    The calculations of heat and hydraulic characteristics and influence of apparatus with intensifiers size analysis to heat exchanger potential of equipment were made onto the basis of known experimental data recommendations. Calculations data were received in a range of parameters, that are typical for a heat and water supply systems. It was obtain, that in studied range of Reynolds’s number, the most better heat transfer coefficient value is for the tubes with dimpled interface...

  11. Simulation Studies on A Cross Flow Plate Fin Heat Exchanger

    OpenAIRE

    M. Thirumarimurugan; T Kannadasan; E. Ramasamy

    2008-01-01

    Compact heat exchangers which were initially developed for the aerospace industries in the1940s have been considerably improved in the past few years. The main reasons for the goodperformance of compact heat exchangers are their special design which includes turbulent which inturn use high heat transfer coefficient and resists fouling, and maximum temperature driving forcebetween the hot and cold fluids. Numerous types use special enhancement techniques to achieve therequired heat transfer in...

  12. Experimental study of a water-mist jet issuing normal to a heated flat plate

    Directory of Open Access Journals (Sweden)

    Vouros Andreas

    2016-01-01

    Full Text Available A parametric experimental study on the development of a round jet spray impacting a smooth, heated, flat plate has been accomplished. The main objective of this effort was to provide information characterizing the flow structure of a developing mist jet, issuing vertically towards an upward facing, horizontal heated plate, by means of simultaneous droplet size and velocity measurements. Phase Doppler Anemometry was used, providing also information on liquid volume flux. The fine spray of small atomized droplets (0.5-5.0 μm, was generated using a medical nebulizer. Two low Reynolds number jets (Re=2952, 3773 issuing from a cylindrical pipe have been tested. The distance between the jets’ exit and the plate was 50 cm. A stainless steel non-magnetic flat plate of dimensions 1000x500x12mm3 was used as target wall. Constant heat flux boundary conditions were established during measurements. Results indicate that the heat flux from the plate is influencing the evolution of the spray jet, diminishing its velocity and turbulence. Average droplet sizes are affected little by the heat flux, although for the non-heated sprays, droplet sizes increase at locations very close to the plate. A significant effect on droplet volume flow rate is also reported.

  13. Performance Evaluation of Plate-Fin-And Tube Heat Exchanger with Wavy Fins- A Review

    OpenAIRE

    Sandip S. Kale; V.W.Bhatkar

    2014-01-01

    The plate fin-and-tube heat exchangers are widely used in variety of industrial applications, particularly in the heating, air-conditioning and refrigeration, HVAC industries. In most cases the working fluid is liquid on the tube side exchanging heat with a gas, usually air. It is seen that the performance of heat exchangers can be greatly increased with the use of unconventionally shaped flow passages such as plain, perforated offset strip, louvered, wavy, vortex generator an...

  14. Ultrasonic inspection of the brazed joint and explosive welds used to repair the PFR evaporators

    International Nuclear Information System (INIS)

    A small number of in-service failures associated with the steam-tube to tube-plate welds of the PFR evaporators led to the decision to protect the welds by sleeving. The philosophy was to insert a sleeve through the tube-plate and into the steam tube, thus bridging the existing weld. The top portion of the sleeve was to be explosively welded to the zone adjacent to the top face of the tube-plate and the lower portion brazed into the steam tube. This paper deals with the development and use of ultrasonics to test both the brazed and explosively welded joints

  15. Feasibility study on development of plate-type heat exchanger for BWR plants

    International Nuclear Information System (INIS)

    In order to apply plate-type heat exchanger to RCW, TCW and FPC system in BWR plants, heat test and seismic test of RCW system heat exchanger sample were carried out. The results of these tests showed new design plate-type heat exchanger satisfied the fixed pressure resistance and seismic resistance and keep the function. The evaluation method of seismic design was constructed and confirmed by the results of tests. As anti-adhesion measure of marine organism, an ozone-water circulation method, chemical-feed method and combination of circulation of hot water and air bubbling are useful in place of the chlorine feeding method. Application of the plate-type heat exchanger to BWR plant is confirmed by these investigations. The basic principles, structure, characteristics, application limit and reliability are stated. (S.Y.)

  16. Natural Convection Heat Transfer From a Hot Rectangular and a Square Corrugated Plate to a Cold Flat Plate

    Institute of Scientific and Technical Information of China (English)

    M.A.R.Akhanda

    2000-01-01

    Experimental study of natural convection heat transfer across air layers bounded by a lower hot rectangular and a square corrugated plates to an upper cold flat plate has been carried out.The surroundings of this space are adiabatic.The effect of the angle of inclination,the aspect ratio,the temperature potential and the Rayleigh number on average heat transfer coefficients are investigated within a range of 0°≤θ≤75°,2.33≤A≤6.33,10°≤ΔT≤35°,and 3.29×104≤RaL≤2.29×106,The developed correlation predicts well the experimental data within an error of ±15%.

  17. Open Channel Natural Convection Heat Transfer on a Vertical Finned Plate

    Energy Technology Data Exchange (ETDEWEB)

    Park, Joo Hyun; Heo, Jeong Hwan; Chung, Bum Jin [Kyung Hee Univ., Yongin (Korea, Republic of)

    2013-10-15

    The natural convection heat transfer of vertical plate fin was investigated experimentally. Heat transfer systems were replaced by mass-transfer systems, based on the analogy concept. The experimental results lie within the predictions of the existing heat transfer correlations of plate-fin for the natural convections. An overlapped thermal boundary layers caused increasing heat transfer, and an overlapped momentum boundary layers caused decreasing heat transfer. As the fin height increases, heat transfer was enhanced due to increased inflow from the open side of the fin spacing. When fin spacing and fin height are large, heat transfer was unaffected by the fin spacing and fin height. Passive cooling by natural convection becomes more and more important for the nuclear systems as the station black out really happened at the Fukushima NPPs. In the RCCS (Reactor Cavity Cooling System) of a VHTR (Very High Temperature Reactor), natural convection cooling through duct system is adopted. In response to the stack failure event, extra cooling capacity adopting the fin array has to be investigated. The finned plate increases the surface area and the heat transfer increases. However, the plate of fin arrays may increase the pressure drop and the heat transfer decreases. Therefore, in order to enhance the passive cooling with fin arrays, the parameters for the fin arrays should be optimized. According to Welling and Wooldridge, a natural convection on vertical plate fin is function of Gr, Pr, L, t, S, and H. The present work investigated the natural convection heat transfer of a vertical finned plate with varying the fin height and the fin spacing. In order achieve high Rayleigh numbers, an electroplating system was employed and the mass transfer rates were measured using a copper sulfate electroplating system based on the analogy concept.

  18. CFD SIMULATION OF THE HEAT TRANSFER PROCESS IN A CHEVRON PLATE HEAT EXCHANGER USING THE SST TURBULENCE MODEL

    Directory of Open Access Journals (Sweden)

    Jan Skočilas

    2015-08-01

    Full Text Available This paper deals with a computational fluid dynamics (CFD simulation of the heat transfer process during turbulent hot water flow between two chevron plates in a plate heat exchanger. A three-dimensional model with the simplified geometry of two cross-corrugated channels provided by chevron plates, taking into account the inlet and outlet ports, has been designed for the numerical study. The numerical model was based on the shear-stress transport (SST k-! model. The basic characteristics of the heat exchanger, as values of heat transfer coefficient and pressure drop, have been investigated. A comparative analysis of analytical calculation results, based on experimental data obtained from literature, and of the results obtained by numerical simulation, has been carried out. The coefficients and the exponents in the design equations for the considered plates have been arranged by using simulation results. The influence on the main flow parameters of the corrugation inclination angle relative to the flow direction has been taken into account. An analysis of the temperature distribution across the plates has been carried out, and it has shown the presence of zones with higher heat losses and low fluid flow intensity.

  19. Thermal Stresses in an Anisotropic Thin Plate Subjected to Moving Plane Heat Sources

    Directory of Open Access Journals (Sweden)

    Malak Naji

    2014-04-01

    Full Text Available The aim of this study is to numerically simulate the plane moving heat source through anisotropic mild steal thin plate. Heat conduction problems in anisotropic material, where the thermal conductivity varies with direction and involving a moving heat source have several industrial applications, such like metal cutting, flame or laser hardening of metals, welding and others. The parabolic heat conduction model is used for the prediction of the temperature history. The temperature distribution inside the plate is determined from the solution of heat equation. Thus, the heat equation is solved numerically using finite deference method and the temperature distributions are determined. The thermal stresses in this case are, also, investigated and computed numerically. It is found that the thermal conductivity ratio affect in both temperature and thermal stresses distributions, in additional to the speed and heat source intensity.

  20. Forced convection heat transfer correlation for finned plates in a duct

    International Nuclear Information System (INIS)

    Forced convection heat transfer experiments were conducted for plate-fin in a duct using various fin spacing, fin height, duct width, Reynolds number for Prandtl numbers 2,014. Based upon analogy concept, mass transfer rate were measured instead of heat transfer rates. The heat transfer rates were enhanced with the increase of fin height and decrease of fin spacing as they increase the heat transfer area. Meanwhile, heat transfer rates were impaired with the increase of the duct width as the bypass flows increased to tip clearance region. Forced convection heat transfer correlations were developed for laminar and turbulent flow conditions and for narrow and wide ducts. The work draws attention to the tip clearance on the heat transfer of the finned plate in a duct. (author)

  1. Characteristic of Local Boiling Heat Transfer of Ammonia / Water Binary Mixture on the Plate Type Evaporator

    Science.gov (United States)

    Okamoto, Akio; Arima, Hirofumi; Kim, Jeong-Hun; Akiyama, Hirokuni; Ikegami, Yasuyuki; Monde, Masanori

    Ocean thermal energy conversion (OTEC) and discharged thermal energy conversion (DTEC) are expected to be the next generation energy production systems. Both systems use a plate type evaporator, and ammonia or ammonia/water mixture as a working fluid. It is important to clarify heat transfer characteristic for designing efficient power generation systems. Measurements of local boiling heat transfer coefficients and visualization were performed for ammonia /water mixture (z = 0.9) on a vertical flat plate heat exchanger in a range of mass flux (7.5 - 15 kg/m2s), heat flux (15 - 23 kW/m2), and pressure (0.7 - 0.9 MPa). The result shows that in the case of ammonia /water mixture, the local heat transfer coefficients increase with an increase of vapor quality and mass flux, and decrease with an increase of heat flux, and the influence of the flow pattern on the local heat transfer coefficient is observed.

  2. Atomistic-Continuum Hybrid Simulation of Heat Transfer between Argon Flow and Copper Plates

    CERN Document Server

    Mao, Yijin; Chen, C L

    2016-01-01

    A simulation work aiming to study heat transfer coefficient between argon fluid flow and copper plate is carried out based on atomistic-continuum hybrid method. Navier-Stokes equations for continuum domain are solved through the Pressure Implicit with Splitting of Operators (PISO) algorithm, and the atom evolution in molecular domain is solved through the Verlet algorithm. The solver is validated by solving Couette flow and heat conduction problems. With both momentum and energy coupling method applied, simulations on convection of argon flows between two parallel plates are performed. The top plate is kept as a constant velocity and has higher temperature, while the lower one, which is modeled with FCC copper lattices, is also fixed but has lower temperature. It is found that, heat transfer between argon fluid flow and copper plate in this situation is much higher than that at macroscopic when the flow is fully developed.

  3. Free convection gas flow near a vertical porous plate with heat sources/sinks

    Energy Technology Data Exchange (ETDEWEB)

    Toki, C.J. [Technological Educational Inst. of Ionian Islands, Zakynthos (Greece). Dept. of Ecology and Environment

    2009-11-15

    In this work, we study the two dimensional free-convection boundary-layer gas flow of a viscous and incompressible fluid near a moving porous, infinite and vertical plate (or wall) in the presence of heat sources/sinks. Exact solution of this problem is found with the help of Laplace transform technique. Analytical expressions of this solution for velocity, temperature, skin-friction, and rate of heat transfer have been developed. The corresponding expressions for nonporous plate are discussed. The derived results are also discussed in details with the help of graphs for vertical air flows, in order to observe the effects of various governing parameters, such as the heat source/sink parameter. Furthermore, a comparison between the results obtained for porous plate and nonporous plate is illustrated in these graphs. (orig.)

  4. Influence of Chimney Flow Pattern on Natural Convection Heat Transfer of Open Channel Finned Plates

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Seung-Hyun; Chung, Bum-Jin [Kyung Hee University, Yongin (Korea, Republic of)

    2015-05-15

    The enhancement of the efficiency and effectiveness of the passive cooling system, have long been the topic of those studies. In this study, we investigated the heat transfer enhancement of finned plates, especially the chimney effect appeared in finned plates. The fin not only enlarges the heat transfer area but also draws fresh fluid from the open side of the channel composed of the base plate and fins, which further enhances the cooling capability of finned plate – a chimney flow pattern. This study aims at investigating the influence of the chimney flow pattern on the natural convection heat transfer of the finned plate. To analyze the phenomenological study, both experimental and numerical analyses were performed. Numerical analysis was performed for the natural convection heat transfer of a finned plate in an open channel. In order to investigate the influence of the chimney flow pattern the heat transfer, several fin height were simulated and compared. The temperature profiles varied drastically depending on the values of the Prandtl number. As the Prandtl number increases, the thermal boundary layer reduces.

  5. Influence of Chimney Flow Pattern on Natural Convection Heat Transfer of Open Channel Finned Plates

    International Nuclear Information System (INIS)

    The enhancement of the efficiency and effectiveness of the passive cooling system, have long been the topic of those studies. In this study, we investigated the heat transfer enhancement of finned plates, especially the chimney effect appeared in finned plates. The fin not only enlarges the heat transfer area but also draws fresh fluid from the open side of the channel composed of the base plate and fins, which further enhances the cooling capability of finned plate – a chimney flow pattern. This study aims at investigating the influence of the chimney flow pattern on the natural convection heat transfer of the finned plate. To analyze the phenomenological study, both experimental and numerical analyses were performed. Numerical analysis was performed for the natural convection heat transfer of a finned plate in an open channel. In order to investigate the influence of the chimney flow pattern the heat transfer, several fin height were simulated and compared. The temperature profiles varied drastically depending on the values of the Prandtl number. As the Prandtl number increases, the thermal boundary layer reduces

  6. Natural convection in water along a vertical plate with constant surface heat flux

    International Nuclear Information System (INIS)

    An experimental investigation of natural convection in water along a vertical plate with constant surface heat flux is described. The results show the effects of the variation of the physical properties on heat transfert especially in the transition regime. In this regime, all the exprimental datas are correlated by a single law which includes the variation of viscosity and the critical Rayleigh number

  7. Internal (Annular) and Compressible External (Flat Plate) Turbulent Flow Heat Transfer Correlations.

    Energy Technology Data Exchange (ETDEWEB)

    Dechant, Lawrence [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Smith, Justin [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2016-01-01

    Here we provide a discussion regarding the applicability of a family of traditional heat transfer correlation based models for several (unit level) heat transfer problems associated with flight heat transfer estimates and internal flow heat transfer associated with an experimental simulation design (Dobranich 2014). Variability between semi-empirical free-flight models suggests relative differences for heat transfer coefficients on the order of 10%, while the internal annular flow behavior is larger with differences on the order of 20%. We emphasize that these expressions are strictly valid only for the geometries they have been derived for e.g. the fully developed annular flow or simple external flow problems. Though, the application of flat plate skin friction estimate to cylindrical bodies is a traditional procedure to estimate skin friction and heat transfer, an over-prediction bias is often observed using these approximations for missile type bodies. As a correction for this over-estimate trend, we discuss a simple scaling reduction factor for flat plate turbulent skin friction and heat transfer solutions (correlations) applied to blunt bodies of revolution at zero angle of attack. The method estimates the ratio between axisymmetric and 2-d stagnation point heat transfer skin friction and Stanton number solution expressions for sub-turbulent Reynolds numbers %3C1x10 4 . This factor is assumed to also directly influence the flat plate results applied to the cylindrical portion of the flow and the flat plate correlations are modified by

  8. Vacuum brazing of metals (1961)

    International Nuclear Information System (INIS)

    We have studied brazing in vacuum aiming its application for the making of containers and apparatus meant for high vacuum (p -8 torr). We first define the wettability of a brazing alloy on a metal and we remind the influence of the various parameters which act on this wettability (nature of the solid, of the liquid, geometrical and physicochemical state of the surface, metallurgical reactions occurring at the interface, temperature, time). We give then the results of the tests carried out in order to determine the conditions of wettability in vacuum of some brazing alloys on metals which can be used for the above mentioned apparatus (stainless steel, aluminium, bronze, titanium, zirconium, kovar, nickel, copper). (author)

  9. Effect of Liquid/Vapour Maldistribution on the Performance of Plate Heat Exchanger Evaporators

    DEFF Research Database (Denmark)

    Jensen, Jonas Kjær; Kærn, Martin Ryhl; Ommen, Torben Schmidt;

    2015-01-01

    Plate heat exchangers are often applied as evaporators in industrial refrigeration and heat pump systems. In the design and modelling of such heat exchangers the flow and liquid/vapour distribution is often assumed to be ideal. However, maldistribution may occur and will cause each channel to...... behave differently due to the variation of the mass flux and vapour quality. To evaluate the effect of maldistribution on the performance of plate heat exchangers, a numerical model is developed in which the mass, momentum and energy balances are applied individually to each channel, including suitable...... correlations for heat transfer and pressure drop. The flow distribution on both the refrigerant and secondary side is determined based on equal pressure drop while the liquid/vapour distribution is imposed to the model. Results show that maldistribution may cause up to a 25 % reduction of the overall heat...

  10. An innovative plate heat exchanger of enhanced compactness

    International Nuclear Information System (INIS)

    In the framework of CEA R&D program to develop the Advanced Sodium Technological Reactor for Industrial Demonstration (ASTRID), the present work aims to demonstrate the industrial interest of an innovative compact heat exchanger technology. In fact, one of the main innovations of the ASTRID reactor could be the use of a Brayton Gas-power conversion system, in order to avoid the energetic sodium–water interaction that might occur if a traditional Rankine cycle was used. The present work aims to study the thermal-hydraulic performance of the innovative compact heat exchanger concept. Hence, thanks to a trustful numerical model, friction factor and heat transfer correlations are obtained. Then, a global compactness comparison strategy is proposed, taking into account design constraints. Finally, it is demonstrated that the innovative heat exchanger concept is more compact then other already industrial technologies of interest, showing that is can be considered to warrant serious consideration for future ASTRID design as well as for any industrial application that needs very compact heat exchanger technologies. - Highlights: • We propose a new innovative compact heat exchanger technology. • We provide thermal-hydraulic correlations for designers. • We provide a comparison strategy with existing technologies. • We demonstrate the industrial interest of the innovative concept

  11. Hydrogen embrittlement of welded joints for the heat-treatable XABO 960 steel heavy plates

    Directory of Open Access Journals (Sweden)

    M. Opiela

    2010-01-01

    Full Text Available Purpose: In the paper, influence of hydrogen on mechanical properties of welded joints from heat-treatable structural XABO 960 steel plates was investigated.Design/methodology/approach: The heat treatment of welded plate specimens was performed, and then the specimens were charged with hydrogen electrolytically generated from 1 N H2SO4 solution. The following studies were carried out: static tensile test, hardness investigations, macroscopic metallographic investigations as well as investigations with the use of a scanning microscope.Findings: Hydrogen embrittlement of welded joints from XABO 960 steel plates was revealed by a distinct decrease of ductility and a slight decrease of strength. On the basis of metallographic investigations, it was found that in a fracture region there are fine pores created by the presence of hydrogen and its displacement due to formed stresses and plastic deformation. It was shown that welded joints are susceptible to hydrogen cracking in the heat affected zone and in the fusion zone.Research limitations/implications: TEM investigations on structure of the steel were predicted.Practical implications: The obtained results can be used for searching the appropriate way of improving the hydrogen embrittlement resistance of welded joints of the heat-treatable structural XABO 960 steel plates.Originality/value: The hydrogen embrittlement of welded joints of the heat-treatable XABO 960 steel plates was investigated.

  12. Velocity Boundary Layer Analysis of a Flat Plate Heat Exchanger in Laminar Flow: A Case Study

    Directory of Open Access Journals (Sweden)

    M. Mirdrikvand

    2012-01-01

    Full Text Available In this article, a behavioral analysis of velocity boundary layer in a flat plate heat exchanger in laminar flow condition through CFD simulation using FLUENT software is done. The main objective of this study is to determine the velocity vectors between the flat plates of the heat exchanger. In addition, wake occurrence, differences of velocity at different surfaces between plates, angles of velocity vectors and the effect of wake phenomenon on the shear stresses exerted on the plates are discussed in detail. The study graphically illustrates results based on fluid’s behavior by a 3D and 2D simulation with air and water as cold and hot streams that affect plate’s situation and its hydro dynamical operations. Consequently, some important design features regarding wake point occurrence and pressure loss are investigated. In addition, eddy current and reverse flows in the wake area and the angles of the velocity vectors are described.

  13. Study of No Corrosion Aluminum Fluxes on Brazing Aluminum Heat Exchanger%钎焊铝制热交换器用无腐蚀铝钎剂的研究

    Institute of Scientific and Technical Information of China (English)

    刘宏江; 曾燕; 蔡志红; 蔡沛沛; 贺军四; 胡泽宇; 李世婕; 黄烨

    2014-01-01

    Based on the AlF3 -KF eutectic compound fluxes, under the circumstances of not changing the non-corrosive nature, by adding additives, the eutectic compound fluxes are modified. By adding inorganic additives, the abilities of removing the oxide film and solderability are improved;And through adding organic additives, the settling property in water is improved, the purpose of efficient use in brazing aluminum heat exchanger is achieved.%以AlF3-KF共晶化合物钎剂为基础,在不改变其无腐蚀性质的情况下,通过添加助剂,对其进行改性。添加无机助剂,提高了钎剂的去膜能力和助焊性;添加有机助剂,提高了钎剂在水中的抗沉降性能,从而达到能高效应用于钎焊铝制热交换器的目的。

  14. Radiation Effects on the Flow and Heat Transfer over a Moving Plate in a Parallel Stream

    Institute of Scientific and Technical Information of China (English)

    Anuar Ishak

    2009-01-01

    Effects of thermal radiation on the steady laminar boundary layer flow over a moving plate in a moving fluid is investigated. Under certain conditions,the present problem reduces to the classical Blasius and Sakiadis problems.It is found that dual solutions exist when the plate and the fluid move in the opposite directions.Moreover,the existence of thermal radiation is to reduce the heat transfer rate at the surface.

  15. Numerical study of natural convection heat transfer from an isothermal thin plate.

    OpenAIRE

    Jaramillo Ibarra, Julian Ernesto; Oliva Llena, Asensio; Pérez Segarra, Carlos David; Soria Guerrero, Manel

    2009-01-01

    In this work detailed numerical simulations of natural convection heat transfer around an isothermal thin plate with different inclinations are carried out. The numerical approach is based on the finite volume technique for the study of air movement around the plate and its surroundings using symmetry-preserving formulation. To solve turbulence, Direct Numerical Simulation (DNS) or Large Eddy Simulation (LES) are selected. After verification of the numerical solutions and comparison of ...

  16. Interaction of radiation and free convection on a heated vertical plate - Experiment and analysis

    Science.gov (United States)

    Webb, B. W.

    1990-01-01

    An experimental and analytical study has been conducted in order to explore the interaction between laminar free convective and radiative transport from an isolated vertical plate with isoflux heating. The analysis focuses on buoyancy-driven free convection from this vertical plate which is coupled to radiation through the thermal boundary condition. Model predictions are compared with both experimental results and the analysis conducted by Cess (1964), in order to illustrate those areas where the perturbation technique deviated from the present solution.

  17. Diffusion bonding and brazing of high purity copper for linear collider accelerator structures

    Science.gov (United States)

    Elmer, J. W.; Klingmann, J.; van Bibber, K.

    2001-05-01

    Diffusion bonding and brazing of high purity copper were investigated to develop procedures for joining precision machined copper components for the Next Linear Collider (NLC). Diffusion bonds were made over a range of temperatures from 400 °C to 1000 °C, under two different loading conditions [3.45 kPa (0.5 psi) and 3.45 MPa (500 psi)], and on two different diamond machined surface finishes. Brazes were made using pure silver, pure gold, and gold-nickel alloys, and different heating rates produced by both radiation and induction heating. Braze materials were applied by both physical vapor deposition (PVD) and conventional braze alloy shims. Results of the diffusion bonding experiments showed that bond strengths very near that of the copper base metal could be made at bonding temperatures of 700 °C or higher at 3.45 MPa bonding pressure. At lower temperatures, only partial strength diffusion bonds could be made. At low bonding pressures (3.45 kPa), full strength bonds were made at temperatures of 800 °C and higher, while no bonding (zero strength) was observed at temperatures of 700 °C and lower. Observations of the fracture surfaces of the diffusion bonded samples showed the effects of surface finish on the bonding mechanism. These observations clearly indicate that bonding began by point asperity contact, and flatter surfaces resulted in a higher percentage of bonded area under similar bonding conditions. Results of the brazing experiments indicated that pure silver worked very well for brazing under both conventional and high heating rate scenarios. Similarly, pure silver brazed well for both the PVD layers and the braze alloy shims. The gold and gold-containing brazes had problems, mainly due to the high diffusivity of gold in copper. These problems led to the necessity of overdriving the temperature to ensure melting, the presence of porosity in the joint, and very wide braze joints. Based on the overall findings of this study, a two-step joining method

  18. Validated TRNSYS model for forced circulation solar water heating systems with flat plate and heat pipe evacuated tube collectors

    OpenAIRE

    MC CORMACK, SARAH

    2011-01-01

    PUBLISHED This paper presents a validated TRNSYS model for forced circulation solar water heating systems used in temperate climates. The systems consist of two flat plate collectors (FPC) and a heat pipe evacuated tube collector (ETC) as well as identical auxiliary components. The systems were fitted with an automated unit that controlled the immersion heaters and hot water demand profile to mimic hot water usage in a typical European domestic dwelling. The main component of the TRNSYS mo...

  19. Validated TRNSYS Model for Forced Circulation Solar Water Heating Systems with Flat Plate and Heat Pipe Evacuated Tube Collectors

    OpenAIRE

    Ayompe, Lacour; Duffy, Aidan; MCCORMACK, SARAH; Conlon, Michael

    2011-01-01

    This paper presents a validated TRNSYS model for forced circulation solar water heating systems used in temperate climates. The systems consist of two flat plate collectors (FPC) and a heat pipe evacuated tube collector (ETC) as well as identical auxiliary components. The systems were fitted with an automated unit that controlled the immersion heaters and hot water demand profile to mimic hot water usage in a typical European domestic dwelling. The main component of the TRNSYS model was the T...

  20. The influence analysis of addition number of plate to heat exchanger performance of TRIGA 2000 reactor

    International Nuclear Information System (INIS)

    In order to reduce the existing bubble in the core of Bandung TRIGA 2000 reactor during its operation above 1000 kW, was done by increasing the effectivity of the heat exchanger (HE). One of the methods for increasing this effectivity is done by adding the number of plate to heat exchanger. To get an appropriate number of plate to be added on achieving its requirement, the analysis to know how the comparison of its performance on variation of addition the number of plate, is needed. The analysis was done by using the NTU-Effectivity method. The variables which influence its effectivity was obtained from the operational experiences since of the year 2000 until 2005. Besides that, it was assumed that the properties of working fluid had not much changed on its temperature and its pressure and small fouling deposit on the plate of HE. The results show that generally the addition of the number of plate would increase the effectivity of the heat exchanger. But for the low flow rate of the primary(600 gpm) and the high flow rate of the secondary(6000 gpm), a little bit of increasing effectivity was obtained for the addition the number of plate, and the effectivity had been reached to above 98%. (author)

  1. Investigation of CaCO3 fouling in plate heat exchangers

    Science.gov (United States)

    Li, Wei; Zhou, Kan; Manglik, Raj M.; Li, Guan-Qiu; Bergles, Arthur E.

    2016-01-01

    An experimental investigation, coupled with theoretical modeling of CaCO3 fouling in plate-and-frame type heat exchangers (PHEs) have been conducted. Four different plates, made of SS-304, are used in two different surface patterns (chevron and zig-zag) of varying corrugation severity (waviness depth and pitch) and area enhancement. They were further characterized in clean, non-fouled convection by their measured heat transfer coefficients and friction factors in the Reynolds number range of 600-6000. The flow-fouling experiments delineate the effects of temperature and plate-surface geometry on growth rates and stabilization of fouling resistance, along with the anti-fouling behavior of plates coated with a hydrophobic PTFE (Teflon) film. Moreover, the microscopic structure of fouling deposits is mapped in a scanning-electron microscope. Corrugated plates with the largest height-to-pitch ratio and hydraulic diameter are found to have the lowest fouling growth rate and resistance; Teflon-film coating of plate surface is also found to mitigate fouling relative to the performance of bare stainless steel plates. Finally, a semi-empirical fouling model, based on the Prandtl-Taylor analogy, has been devised to describe the experimental data and provide a predictive tool.

  2. Numerical Methods for Plate Forming by Line Heating

    DEFF Research Database (Denmark)

    Clausen, Henrik Bisgaard

    2000-01-01

    Few researchers have addressed so far the topic Line Heating in the search for better control of the process. Various methods to help understanding the mechanics have been used, including beam analysis approximation, equivalent force calculation and three-dimensional finite element analysis. I co...

  3. An analytical investigation of transient effects on rewetting of heated thin flat plates

    Science.gov (United States)

    Platt, J. A.

    1993-01-01

    The rewetting of a hot surface is a problem of prime importance in the microgravity application of heat pipe technology, where rewetting controls the time before operations can be re-established following depriming of a heat pipe. Rewetting is also important in the nuclear industry (in predicting behavior during loss-of-coolant accidents), as well as in the chemical and petrochemical industries. Recently Chan and Zhang have presented a closed-form solution for the determination of the rewetting speed of a liquid film flowing over a finite (but long) hot plate subject to uniform heating. Unfortunately, their physically unreasonable initial conditions preclude a meaningful analysis of start-up transient behavior. A new nondimensionalization and closed-form solution for an infinitely-long, uniformly-heated plate is presented. Realistic initial conditions (step change in temperature across the wetting front) and boundary conditions (no spatial temperature gradients infinitely far from the wetting front) are employed. The effects of parametric variation on the resulting simpler closed-form solution are presented and compared with the predictions of a 'quasi-steady' model. The time to reach steady-state rewetting is found to be a strong function of the initial dry-region plate temperature. For heated plates it is found that in most cases the effect of the transient response terms cannot be neglected, even for large times.

  4. Nocturnal cooling : Study of heat transfer from a flat-plate solar collector

    OpenAIRE

    Johansson, Helena

    2008-01-01

    This thesis investigates the possibility of using an unglazed flat-plate solar collector as a cooling radiator. The solar collector will be connected to the condenser of a heat pump and used as cooler during nighttime. Daytime the solar collector will be connected to the evaporator of the heat pump and used as heat source. The two widely differing fields of application make special demands on the solar collector. The task is given by the heat pump manufacturer Thermia and the main objective i...

  5. The influence of flow maldistribution on the performance of inhomogeneous parallel plate heat exhangers

    DEFF Research Database (Denmark)

    Nielsen, Kaspar Kirstein; Engelbrecht, Kurt; Bahl, Christian R.H.

    2013-01-01

    The heat transfer performance of inhomogeneous parallel plate heat exchangers in transient operation is investigated using an established model. A performance parameter, denoted the Nusselt-scaling factor, is used as benchmark and calculated using a well-established single blow technique. A sample...... of 50 random stacks having equal average channel thicknesses with 20 channels each are used to provide a statistical base. The standard deviation of the stacks is varied as are the flow rate (Reynolds number) and the thermal conductivity of the solid heat exchanger material. It is found that the heat...

  6. Heat transfer and thermodynamic performance of a parabolic trough receiver with centrally placed perforated plate inserts

    International Nuclear Information System (INIS)

    Highlights: • Heat transfer enhancement of a parabolic trough receiver with perforated plate inserts is studied. • Effect of insert geometrical parameters on receiver thermal performance is investigated. • Correlations for Nusselt number and friction factor performance are derived and presented. • Performance evaluation using enhancement factors and collector modified thermal efficiency was demonstrated. • Thermodynamic performance is investigated using the entropy generation minimization method. - Abstract: In this paper, a numerical investigation of thermal and thermodynamic performance of a receiver for a parabolic trough solar collector with perforated plate inserts is presented. The analysis was carried out for different perforated plate geometrical parameters including dimensionless plate orientation angle, the dimensionless plate spacing, and the dimensionless plate diameter. The Reynolds number varies in the range 1.02 × 104 ⩽ Re ⩽ 7.38 × 105 depending on the heat transfer fluid temperature. The fluid temperatures used are 400 K, 500 K, 600 K and 650 K. The porosity of the plate was fixed at 0.65. The study shows that, for a given value of insert orientation, insert spacing and insert size, there is a range of Reynolds numbers for which the thermal performance of the receiver improves with the use of perforated plate inserts. In this range, the modified thermal efficiency increases between 1.2% and 8%. The thermodynamic performance of the receiver due to inclusion of perforated plate inserts is shown to improve for flow rates lower than 0.01205 m3/s. Receiver temperature gradients are shown to reduce with the use of inserts. Correlations for Nusselt number and friction factor were also derived and presented

  7. Microstructure and characteristics of high dimension brazed joints of cermets and steel

    Directory of Open Access Journals (Sweden)

    J. Nowacki

    2009-12-01

    Full Text Available Purpose: In the article a state of the question concerning stresses in brazing joints of different physical and mechanical properties was appraised as well as possibility of their decrease due to use of different techniques from technological experiments to numerical methods. Evaluation of microstructure and mechanical properties of large dimensional vacuum brazed joints of WC – Co and Ferro Titanit Nicro 128 sinters and precipitation hardened stainless steel of 14 –5 PH (X5CrNiMoCuNb14-5 using copper and silver – copper as the brazing filler metal.Design/methodology/approach: Microscopic examinations with the use of scanning electron microscope (SEM were performed to establish microstructure and diffusion influences on creation of intermetallic phases in the joint. Shear strength Rt and tensile strength Rm of the joints have been defined. It have been state, that the basic factors decreasing quality of the joint, which can occur during vacuum brazing of the WC - Co ISO K05 sinter – Cu or Ag - Cu brazing filler metal – 14 -5 PH steel joints are diffusive processes leading to exchange of the cermets and brazing filler metal elements and creation of intermetallic in the joint. It can have an unfavourable influence on ductility and quality of the joint.Findings: Results of numerical calculations of two-dimensional models of brazed joints for different sizes of surfaces brazed at a constant width of solder gap are presented. Particular attention was paid to stresses occurring in joints of large brazing surfaces.Results of the investigate proved that joints microstructure and mechanical properties depend on filler and parent materials, diffusion process during brazing, leading to exchange of the cermets components and filler metal as well as joint geometry (mainly gap thickness.Practical implications: The results have been applied in surfaces are used in large dimension spinning nozzles of a die for polyethylene granulation, in that

  8. New Configurations of Micro Plate-Fin Heat Sink to Reduce Coolant Pumping Power

    DEFF Research Database (Denmark)

    Kolaei, Alireza Rezania; Rosendahl, Lasse

    2012-01-01

    The thermal resistance of heat exchangers has a strong influence on the electric power produced by a thermoelectric generator (TEG). In this work, a real TEG device is applied to three configurations of micro plate-fin heat sink. The distance between certain microchannels is varied to find the...... optimum heat sink configuration. The particular focus of this study is to reduce the coolant mass flow rate by considering the thermal resistances of the heat sinks and, thereby, to reduce the coolant pumping power in the system. The threedimensional governing equations for the fluid flow and the heat...... transfer are solved using the finite-volume method for a wide range of pressure drop laminar flows along the heat sink. The temperature and the mass flow rate distribution in the heat sink are discussed. The results, which are in good agreement with previous computational studies, show that using suggested...

  9. Performance Evaluation of Plate-Fin-And Tube Heat Exchanger with Wavy Fins- A Review

    Directory of Open Access Journals (Sweden)

    Sandip S. Kale

    2014-09-01

    Full Text Available The plate fin-and-tube heat exchangers are widely used in variety of industrial applications, particularly in the heating, air-conditioning and refrigeration, HVAC industries. In most cases the working fluid is liquid on the tube side exchanging heat with a gas, usually air. It is seen that the performance of heat exchangers can be greatly increased with the use of unconventionally shaped flow passages such as plain, perforated offset strip, louvered, wavy, vortex generator and pin. The current study is focused on wavy-fin. The wavy surface can lengthen the path of airflow and cause better airflow mixing. In order to design better heat exchangers and come up with efficient designs, a thorough understanding of the flow of air in these channels is required. Hence this study focuses on the heat transfer and friction characteristics of the air side for wavy fin and tube heat exchanger.

  10. On the pressure drop in Plate Heat Exchangers used as desorbers in absorption chillers

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Hernando, N.; de Vega, M. [Energy System Engineering (ISE), Departamento de Ingenieria Termica y de Fluidos, Universidad Carlos III de Madrid, Avda. Universidad, 30, 28911 Leganes, Madrid (Spain); Almendros-Ibanez, J.A. [Escuela de Ingenieros Industriales de Albacete, Departamento de Mecanica Aplicada e Ingenieria de Proyectos, Universidad de Castilla La Mancha, Campus Universitario s/n, 02071 Albacete (Spain); Renewable Energy Research Institute, c/de la Investigacion s/n, 02071 Albacete (Spain); Ruiz, G. [Energy Efficiency and Renewables Department, Tecnicas Reunidas S.A., C/Arapiles No. 13, 10a, 28015 Madrid (Spain)

    2011-02-15

    The influence of the pressure drop in Plate Heat Exchangers (PHE) in the boiling temperature of LiBr-H{sub 2}O and NH{sub 3}-H{sub 2}O solutions is studied. For the NH{sub 3}-H{sub 2}O solution, the pressure drop-temperature saturation relationship estates that high pressure drops can be allowed in the solution with negligible changes in the saturation temperature, and in the PHE performance. Besides, in the case of the LiBr-H{sub 2}O solution, as the working pressure is usually very low, the analysis of the pressure drop must be taken as a main limiting parameter for the use of Plate Heat Exchangers as vapour generators. In this case, the pressure drop may considerably change the boiling temperature of the solution entering the heat exchanger and therefore a higher heating fluid temperature may be required. A guideline to design these systems is proposed. (author)

  11. Plate heat exchanger performance in a nuclear safety-related service water application

    International Nuclear Information System (INIS)

    In the mid-1980's the Tennessee Valley Authority installed plate heat exchangers in the safety-related service water system at the Sequoyah Nuclear Plant. These heat exchangers are compact, they can be assembled in place, they require less flow than more conventional heat exchangers, and they are easily cleaned. However, equations to predict thermal performance are not readily available in the open literature. An analytical model was developed to predict performance of the heat exchangers at off-design conditions and to trend thermal performance. Periodic surveillance tests have been performed and the fouling resistance has been calculated based on these tests and the analytical model. Biological fouling of the plates on the raw water side was determined to be greater than expected due to inadequate biocide treatment of the system

  12. Optimization in plate-fin safety structure of heat exchanger using genetic and Monte Carlo algorithm

    International Nuclear Information System (INIS)

    A safety structure of plate-fin heat exchanger is designed for special applications to prevent fluid leakage from adjacent channel walls. A fractional volume of a cavity layer between two channels is filled with high thermal conductive column-shape metal. Genetic algorithm is used for optimization of column distributions to achieve the maximum heat transfer performance, and its output is better than the simple direct optimization. To optimize with uncertain fluid condition, a direct genetic algorithm method, two improved genetic algorithm methods and a specific type of Monte Carlo algorithm method are applied in searching suitable solution. The optimized structure can provide a new feasible and safety plate-fin heat exchanger, and its results obtained by using genetic algorithm and Monte Carlo algorithm can provide some guidelines for optimal designs of heat exchangers

  13. On the pressure drop in Plate Heat Exchangers used as desorbers in absorption chillers

    International Nuclear Information System (INIS)

    The influence of the pressure drop in Plate Heat Exchangers (PHE) in the boiling temperature of LiBr-H2O and NH3-H2O solutions is studied. For the NH3-H2O solution, the pressure drop-temperature saturation relationship estates that high pressure drops can be allowed in the solution with negligible changes in the saturation temperature, and in the PHE performance. Besides, in the case of the LiBr-H2O solution, as the working pressure is usually very low, the analysis of the pressure drop must be taken as a main limiting parameter for the use of Plate Heat Exchangers as vapour generators. In this case, the pressure drop may considerably change the boiling temperature of the solution entering the heat exchanger and therefore a higher heating fluid temperature may be required. A guideline to design these systems is proposed.

  14. Upper and lower bounds for the heat flux in a gas between parallel plates

    International Nuclear Information System (INIS)

    Waldmann's result for heat transfer through a monatomic gas between parallel plates is the starting point for the derivation of upper and lower bounds for the heat flux as a function of Knudsen number. In order to obtain numerical results, one transport-relaxation eigenfunction and its eigenvalue are determined approximately, and a simple model for the interfacial kernel of the kinetic boundary condition for the distribution function is used. (orig.)

  15. Studi Eksperimen Analisa Performa Compact Heat Exchanger Circular Tubes Continuous Plate Fin Untuk Pemanfaatan Waste Energy

    OpenAIRE

    Rachmadi Gewa Saputra; Ary Bachtiar Khrisna Putra

    2014-01-01

    Harga minyak dunia cenderung mengalami peningkatan dalam beberapa tahun terakhir sehingga manusia berfikir untuk memanfaatkan setiap penggunaan minyak bumi. Dengan berkembangnya teknologi saat ini waste energy yang berupa gas hasil pembakaran pada engine dapat dimanfaatkan menjadi bentuk energi lain menggunakan heat recovery system. Pada tugas akhir ini dilakukan desain sebuah heat exchanger tipe circular tubes continuous plate fin dengan susunan tube aligned yang digunakan untuk menyerap was...

  16. CFD analysis of the plate heat exchanger - Mathematical modelling of mass and heat transfer in serial connection with tubular heat exchanger

    Science.gov (United States)

    Bojko, Marian; Kocich, Radim

    2016-06-01

    Application of numerical simulations based on the CFD calculation when the mass and heat transfer between the fluid flows is essential component of thermal calculation. In this article the mathematical model of the heat exchanger is defined, which is subsequently applied to the plate heat exchanger, which is connected in series with the other heat exchanger (tubular heat exchanger). The present contribution deals with the possibility to use the waste heat of the flue gas produced by small micro turbine. Inlet boundary conditions to the mathematical model of the plate heat exchanger are obtained from the results of numerical simulation of the tubular heat exchanger. Required parameters such for example inlet temperature was evaluated from temperature field, which was subsequently imported to the inlet boundary condition to the simulation of plate heat exchanger. From the results of 3D numerical simulations are evaluated basic flow variables including the evaluation of dimensionless parameters such as Colburn j-factor and friction ft factor. Numerical simulation is realized by software ANSYS Fluent15.0.

  17. Numerical Model on Frost Height of Round Plate Fin Used for Outdoor Heat Exchanger of Mobile Electric Heat Pumps

    OpenAIRE

    Lee, Moo-Yeon

    2012-01-01

    The objective of this study is to provide the numerical model for prediction of the frost growth of the round plate fin for the purpose of using it as a round plate fin-tube heat exchanger (evaporator) under frosting conditions. In this study, numerical model was considering the frost density change with time, and it showed better agreement with experimental data of Sahin (1994) than that of the Kim model (2004) and the Jonse and Parker model (1975). This is because the prediction on the fros...

  18. Numerical Evaluation of Flow and Heat Transfer in Plate-Pin Fin Heat Sinks with Various Pin Cross-Sections

    OpenAIRE

    Zhou, Feng; Catton, Ivan

    2011-01-01

    A numerical investigation of the thermal and hydraulic performance of twenty different plate-pin fin heat sinks with various shapes of pin cross-section (square, circular, elliptic, NACA profile and dropform) and different ratios of pin widths to plate fin spacing (0.3, 0.4, 0.5 and 0.6) was performed. Finite Volume Method based CFD software, Ansys CFX, was used as the 3-D Reynolds-averaged Navier-Stokes Solver. A k-ω based Shear-Stress-Transport model was used to predict the turbulent flow a...

  19. Optimal design of plate-fin heat exchangers by a Bees Algorithm

    International Nuclear Information System (INIS)

    In this study, the application of Bees Algorithm (BA) in the optimum design of a cross flow plate-fin heat exchanger with offset strip fin is investigated. First, heat exchanger is optimized and designed according to the effectiveness optimization. Then, an analysis based on the second law of thermodynamics and minimizations of entropy generation units is performed. Specific heat duty, space restriction and permitted pressure drop are considered as the constraints for maximizing the effectiveness and minimizing the entropy generation units. Hot and cold flow length of the heat exchangers, number of fin layers, fin frequency, fin height, fin strip length and fin thickness are introduced as optimization variables. The effectiveness and accuracy of the suggested algorithm are compared with literature. The results have shown that BA can find optimum configuration with higher accuracy in comparison with Genetic Algorithm (GA), Particle Swarm Optimization (PSO), Imperialist Competitive Algorithm (ICA) and preliminary design. - Highlights: •We analyzed a plate-fin heat exchanger with offset strip fins. •This is the first application of a Bees Algorithm for plate-fin heat exchanger design. •Preliminarily design and effectiveness of PFHE was improved by minimizing the entropy generation units. •The results show the superiority of this method over GA, PSO and ICA and preliminary design

  20. Flow field and thermal characteristics induced by a rotationally oscillating heated flat plate

    Science.gov (United States)

    Koffi, Moise

    The objective of this dissertation is the study the flow and heat transfer in the vicinity of a rectangular flat heated plate of subject to rotational oscillations. Of interest is the effect of the flow field on the thermal characteristics of the plate's surface. A constant heat flux is applied to both sides while the plate is rotated about a fixed edge at a frequency of 2 rad/s in an infinite domain at atmospheric pressure. A computational simulation of the flow with FLUENT reveals a hooked-shape vortex tube around the free edges of the plate, which is confirmed by the flow visualization with smoke particles. During the flapping cycle, vortices form and grow progressively on one face while they shed from the opposite, until they are completely detached from both surfaces at stroke reversal. A data acquisition system uses a numerical computing and programming software (MATLAB) to track the surface temperature recorded by J- type thermocouples at desired locations on the plate. Both experimental and computational results agree with local surface temperature profiles characterized by a transient unsteady periodic variation followed by a steady periodic phase. These characteristics are symmetrical about the median plane of the plate, which is normal to its axis of rotation. The cooling rate of the surface, proportional to the frequency of rotation, depends on the angular position of the plate and the spatial location on the plate's surface. However, the highest heat transfer coefficient is recorded at free edges, especially in the corners swept by strong tip vortices shedding in two orthogonal directions. Conclusions of the present study are used to explain the role of ear flapping in the metabolic heat regulation of large mammals such as elephants. Flow visualization and surface temperature measurements of full size rigid and flexible elephant ear-shape models were carried out. Results indicate improved interaction between the shedding vortex and the model's boundary

  1. MHD Stagnation Flow of a Newtonian Fluid towards a Uniformly Heated and Moving Vertical Plate

    Directory of Open Access Journals (Sweden)

    Mehmet Şirin Demir

    2016-01-01

    Full Text Available Stagnation flow of an electrically conducting incompressible viscous fluid towards a moving vertical plate in the presence of a constant magnetic field is investigated. By using the appropriate transformations for the velocity components and temperature, the partial differential equations governing flow and heat transfer are reduced to a set of nonlinear ordinary differential equations. These equations are solved approximately using a numerical technique for the following two problems: (i two-dimensional stagnation-point flow on a moving vertical plate, (ii axisymmetric stagnation-point flow on a moving vertical plate. The effects of non-dimensional parameters on the velocity components, wall shear stresses, temperature and heat transfer are examined carefully.

  2. Enhanced microwave absorbing properties and heat resistance of carbonyl iron by electroless plating Co

    Science.gov (United States)

    Wang, Hongyu; Zhu, Dongmei; Zhou, Wancheng; Luo, Fa

    2015-11-01

    Co coated carbonyl iron particles (Co (CI)) are fabricated through electroless plating method, and the electromagnetic microwave absorbing properties are investigated in the frequencies during 8.2-12.4 GHz. The complex permittivity of CI particles after electroless plating Co is higher than that of raw CI particles due to improvment of the polarization process. Furthermore, according to the XRD and TG results, the Co layer can enhance the heat resistance of CI particles. The bandwidth below -10 dB can reach 3.9 GHz for the Co(CI) absorbent. The results indicate that the electroless plating Co not only enhances the absorbing properties but also improves the heat resistance of CI.

  3. Investigation of defect characteristics and heat transfer in step heating thermography of metal plates repaired with composite patches

    Science.gov (United States)

    Daryabor, P.; Safizadeh, M. S.

    2016-05-01

    Nowadays, composite patches are widely used in different industries to repair damaged metal structures. Inspection of such repaired structures is always considered as a challenging task. Different thermography methods such as step heating are commonly used to inspect repaired structures. Some parameters such as defect features or heating procedure play major roles in defect detection. In this work, in order to investigate such effects, step heating thermography of an aluminum plate repaired with a composite patch is modeled and tested. The main goal of this study is to evaluate the effects of defect type (delamination and disbond), size and depth on the detection ability of the test. Moreover, regarding the heat transfer process obtained from the simulation, the appropriate heating procedure for inspecting the repaired metal structures is determined. To validate the simulation outputs, experimental results corresponding to the temperature variations are compared with those predicted from the simulation.

  4. Thermal deformation in a thin circular plate due to a partially distributed heat supply

    Indian Academy of Sciences (India)

    N L Khobragade; K C Deshmukh

    2005-08-01

    In this paper, we develop an integral transform to determine temperature distribution in a thin circular plate, subjected to a partially distributed and axisymmetric heat supply on the curved surface, and study the thermal deformation. The results, obtained in series form in terms of Bessel’s functions, are illustrated numerically.

  5. MHD Boundary Layer Slip Flow and Heat Transfer over a Flat Plate

    Institute of Scientific and Technical Information of China (English)

    Krishnendu Bhattacharyya; Swati Mukhopadhyay; G.C.Layek

    2011-01-01

    An analysis of magnetohydrodynamic (MHD) boundary layer flow and heat transfer over a flat plate with slip condition at the boundary is presented. A complete self-similar set of equations are obtained from the governing equations using similarity transformations and are solved by a shooting method. In the boundary slip condition no local similarity occurs. Velocity and temperature distributions within the boundary layer are presented. Our analysis reveals that the increase of magnetic and slip parameters reduce the boundary layer thickness and also enhance the heat transfer from the plate.%@@ An analysis of magnetohydrodynamic (MHD) boundary layer flow and heat transfer over a flat plate with slip condition at the boundary is presented.A complete self-similar set of equations are obtained from the governing equations using similarity transformations and are solved by a shooting method.In the boundary slip condition no local similarity occurs.Velocity and temperature distributions within the boundary layer are presented.Our analysis reveals that the increase of magnetic and slip parameters reduce the boundary layer thickness and also enhance the heat transfer from the plate.

  6. Filler alloys for brazing in power industries

    International Nuclear Information System (INIS)

    The problem is discussed of using nickel-based high-temperature brazing solders in nuclear power engineering. Different types of brazing solders are compared with regard to brazing and mechanical properties and oxidation resistance. The advantages of nickel-based brazing solders include their melting temperature which is higher by 150 to 200 degC than the melting temperatures of common solders. The effects of different additions on melting temperature are discussed. It is advisable to use the above brazing solders under hydrogen reduction atmosphere at a temperature of -40 down to -75 degC or at a pressure of 10-3 down to 10-4 Pa. Currently manufactured nickel-based brazing solders may be used at a temperature of up to 1150 degC. (J.B.)

  7. Analytical Thermal and Cost Optimization of Micro-Structured Plate-Fin Heat Sink

    DEFF Research Database (Denmark)

    Rezaniakolaei, Alireza; Rosendahl, Lasse

    Microchannel heat sinks have been widely used in the field of thermo-fluids due to the rapid growth in technological applications which require high rates of heat transfer in relatively small spaces and volumes. In this work, a micro plate-fin heat sink is optimized parametrically, to minimize the...... thermal resistance and to maximize the cost performance of the heat sink. The width and the height of the microchannels, and the fin thickness are analytically optimized at a wide range of pumping power. Using an effective numeric test, the generated equations also discuss the optimum parameters at three...... sizes of the substrate plat of the heat sink. Results show that, at any pumping power there are specific values of the channel width and fin thickness which produce minimum thermal resistance in the heat sink. The results also illustrate that, a larger channel width and a smaller fin thickness lead to a...

  8. Flow and heat transfer characteristics on a moving flat plate in a parallel stream with constant surface heat flux

    Energy Technology Data Exchange (ETDEWEB)

    Ishak, Anuar; Nazar, Roslinda [Universiti Kebangsaan Malaysia, School of Mathematical Sciences, Selangor (Malaysia); Pop, Ioan [University of Cluj, Faculty of Mathematics, CP 253, Cluj (Romania)

    2009-03-15

    This paper considers the extended classical Blasius and Sakiadis equations, by considering a uniform free stream parallel to a fixed or moving flat plate, which has more practical significance. It is assumed that the plate is subjected to a constant heat flux, and moves in the same or opposite direction to the free stream. The resulting system of nonlinear ordinary differential equations is solved numerically using a finite-difference method. Numerical results are obtained for the skin friction coefficient and the local Nusselt number as well as the velocity and temperature profiles for some values of the governing parameters, namely the velocity ratio parameter and the Prandtl number. The results indicate that dual solutions exist when the plate and the free stream move in the opposite directions. (orig.)

  9. The thermal state of the Arabian plate derived from heat flow measurements in Oman and Yemen

    Science.gov (United States)

    Rolandone, Frederique; Lucazeau, Francis; Leroy, Sylvie; Mareschal, Jean-Claude; Jorand, Rachel; Goutorbe, Bruno; Bouquerel, Hélène

    2013-04-01

    The dynamics of the Afar plume and the rifting of the Red Sea and the Gulf of Aden affect the present-day thermal regime of the Arabian plate. However, the Arabian plate is a Precambrian shield covered on its eastern part by a Phanerozoic platform and its thermal regime, before the plume and rifting activities, should be similar to that of other Precambrian shields with a thick and stable lithosphere. The first heat flow measurements in the shield, in Saudi Arabia, yielded low values (35-44 mW/m2), similar to the typical shields values. Recent heat flow measurements in Jordan indicate higher values (56-66 mW/m2). As part of the YOCMAL project (YOung Conjugate MArgins Laboratory), we have conducted heat flow measurements in southern and northern Oman to obtain 10 new heat flux values in the eastern Arabian plate. We also derived 20 heat flux values in Yemen and Oman by processing thermal data from oil exploration wells. The surface heat flux in these different locations is uniformly low (45 mW/m2). The heat production in samples from the Dhofar and Socotra Precambrian basement is also low (0.7 µW/m3). Differences in heat flow between the eastern (60 mW/m2) and the western (45 mW/m2) parts of Arabia reflect differences in crustal heat production as well as a higher mantle heat flux in the west. We have calculated a steady state geotherm for the Arabian platform that intersects the isentropic temperature profile at a depth of about 150 km, consistent with the seismic observations. Seismic tomography studies of the mantle beneath Arabia also show this east-west contrast. Seismic studies have shown that the lithosphere is rather thin, 100 km or less below the shield and 150 km below the platform. The lithospheric thickness for the Arabian plate is 150 km, and the progressive thinning near the Red Sea, caused by the thermal erosion of the plume material, is too recent to be detected at the surface. The Afar plume mostly affects the base of the Arabian lithosphere along

  10. Brazing of 14-5 PH steel and WC-Co sinterson considerable dimension surfaces

    Directory of Open Access Journals (Sweden)

    J. Nowacki

    2007-03-01

    Full Text Available Purpose: of this paper is study of structure properties of considerable surfaces vacuum brazed joints of WC-Co sinters and precipitation hardened stainless steel of 14-5 PH using copper and silver-copper as the brazing filler metal.Design/methodology/approach: the joints are used in large dimension spinning nozzles of a die for polyethylene granulation, in that considerable strength and ductility of the joints are required. Structure and mechanical properties of joints have been described. Shear strength Rt and tensile strength Rm of the joints have been defined.Findings: to have been state, that the basic factors decreasing quality of the joint, which can occur during vacuum brazing of the WC-Co ISO K05 sinter – Cu or Ag-Cu brazing filler metal – 14-5 PH steel joints are diffusive processes leading to exchange of elements of cermets and the brazing filler metal and creation of intermetalics in the joint. It can have an unfavourable influence on ductility of sinters and quality of joint. As a result of brazing tests the influence of means and parameters of the brazing on quality of a joint was determined.Research limitations/implications: as a result of the experiments scheme of the joint structure WC-Co ISO K05 sinter – Cu brazing filler metal – 14-5 PH steel joint and WC-Co ISO K05 sinter – Cu brazing filler metal – 14-5 PH have been described.Practical implications: as a result of conducted experiments a production of spinning nozzle of a die for polyethylene granulation with a vacuum-brazed with a WC-Co ISO K05 sinters plates cutting surface of large surfaces on precipitation hardened stainless steel 14-5 PH have been worked out and industrial applied.Originality/value: the basic factors decreasing quality of the joint, which can occur while vacuum brazing of stainless steels and cermets have been determined.

  11. Eddy current heating of irregularly shaped plates by slow ramped fields

    International Nuclear Information System (INIS)

    Eddy current heating of thin conducting plates of various shapes by a perpendicular field is studied, assuming that the magnetic field created by the eddy currents is negligible in comparison with the external field. The method is to introduce the stream function of the eddy currents, which is shown to satisfy Poisson's equation, and then employ a pair of complementary variational principles (i.e., a minimum principle and a maximum principle), the extrema of which equal the eddy current heating. Two such complementary principles give not only an estimate of the eddy current heating, but a bound on the error of the estimate as well

  12. Study of Dynamic Buckling of FG Plate Due to Heat Flux Pulse

    Directory of Open Access Journals (Sweden)

    Czechowski L.

    2015-02-01

    Full Text Available The paper deals with a FEM analysis of dynamic buckling of functionally graded clamped plates under heat flux loading with huge power. The materials of structures as well as their properties are varying in each layer across the plate thickness formulated by the power law distribution. The heat flux was applied evenly to the whole ceramic surface. The analysis was developed in the ANSYS 14.5 software. The duration of the heat flux loading equal to a period of natural fundamental flexural vibrations of given structures was taken into consideration. To implement large deflections of structures, the Green-Lagrange nonlinear-displacement equations and the incremental Newton-Raphson algorithm were applied. An evaluation of the dynamic response of structures was carried out on basis of the Budiansky-Hutchinson criterion. The studies were conducted for different volume fraction distributions and different shapes of the heat flux loading. The computation results of the heat flux versus maximal plate deflection are shown and discussed.

  13. A Numerical Study on Laminar Free Convection between Vertical Flat Plates with Symmetric Heating

    Directory of Open Access Journals (Sweden)

    Ameer A. Jadoaa

    2012-06-01

    Full Text Available The development of free convection in a viscous fluid between heated plates is investigated. The basic governing continuity, momentum, and energy equations are solved numerically by finite difference method. Results are obtained for the variations of Nusselt number, velocity, temperature, and pressure throughout the flow field assuming the fluid to enter the channel with ambient temperature and a flat velocity profile. The flow and heat-transfer characteristics of the channel are studied and a development height established. Heating plate condition is (C.W.T and C.H.F. An correlation equation has been deduced for the average Nusselt number as a function of Rayligt number. A comparison is made between the results of this theoretical investigation and theoretical work of (Bodoia, J.R 1962[1].

  14. Unsteady Hydromagnetic Flow of Radiating Fluid Past a Convectively Heated Vertical Plate with the Navier Slip

    Directory of Open Access Journals (Sweden)

    O. D. Makinde

    2014-01-01

    Full Text Available This paper investigates the unsteady hydromagnetic-free convection of an incompressible electrical conducting Boussinesq’s radiating fluid past a moving vertical plate in an optically thin environment with the Navier slip, viscous dissipation, and Ohmic and Newtonian heating. The nonlinear partial differential equations governing the transient problem are obtained and tackled numerically using a semidiscretization finite difference method coupled with Runge-Kutta Fehlberg integration technique. Numerical data for the local skin friction coefficient and the Nusselt number have been tabulated for various values of parametric conditions. Graphical results for the fluid velocity, temperature, skin friction, and the Nusselt number are presented and discussed. The results indicate that the skin friction coefficient decreases while the heat transfer rate at the plate surface increases as the slip parameter and Newtonian heating increase.

  15. HYSYS Automation and Its Application on Evaluation of Plate Heat Exchanger

    Institute of Scientific and Technical Information of China (English)

    Dai Yuqiang; Liu Wenwei; Wang Shaomin; Hu Dapeng

    2008-01-01

    When simulating or designing plate heat exchangers for multicomponent mixtures, most de-signers are often perplexed with the question on how to choose or estimate the physical property param-eters and hope to have a reliable database that could be adopted. The commercial codes HYSYS supply the physical property package on over 1500 pure substances and over 16 000 binary coefficients for them.This work has briefly presented an efficient communication interface based on the Microsoft Component Object Model (COM) between inner plate heat exchanger simulation codes and the HYSYS package. The application of a custom-made HYSYS-COM interface has shown high efficiency, such as significant re-duction of time needed for evaluating each process stream's properties. This automation method can be conveniently extended to further optimization study for any specific operation device such as heat transfers,columns, and other facilities.

  16. Natural COnvective Heat and Mass Transfer on a Vertical Heated Plate for Water Flow Containing Metal Corrosion Particles

    Institute of Scientific and Technical Information of China (English)

    Pei-xueJiang; Ze-peiRen; 等

    1992-01-01

    Corrosion products of structural materials when contained in water usually are in two states:soluble state and colloidal particles with dimeter about 10-3-10-1um,Deposits of such corrosion products on tube surfaces under high pressure will jeopardize the operating economy of power plant equipment and even esult in accidents.A numerical study is reported in this paper of the natural convective heat and mass transfer on a vertical heated plate subject to the flrst or mixed kind of boundary conditions for high-pressure water(P=17MPa) containing metal corrosion products with consideration of varialbe thermophysical properties.

  17. Natural convection in an asymmetrically heated vertical channel with an adiabatic auxiliary plate

    International Nuclear Information System (INIS)

    The effect of an auxiliary plate on natural convection in an asymmetrically heated channel is studied numerically in laminar regime. The computational procedure is made by solving the unsteady two dimensional Navier-Stokes and energy equations. This nonlinear system is integrated by a finite volume approach and then solved in time using the projection method, allowing the decoupling pressure from velocity. More than hundred simulations are performed to determine the best positions of the auxiliary plate that enhance the induced mass flow and the heat transfer rate for modified Rayleigh numbers ranging from Ram = 102 to Ram = 105. Contour maps are plotted and then used to precise the enhancement rates of the mass flow and the heat transfer for any position of the auxiliary plate in the channel. The numerical results (velocity, pressure and temperature fields) provide detailed information about the evolution of the flow structure according to the geometry considered in this study. In addition, they permit to explain why the mass flow rate and Nusselt number are enhanced for certain positions of the auxiliary plate and are on the contrary deteriorated for others. (authors)

  18. Enhanced microwave absorbing properties and heat resistance of carbonyl iron by electroless plating Co

    International Nuclear Information System (INIS)

    Co coated carbonyl iron particles (Co (CI)) are fabricated through electroless plating method, and the electromagnetic microwave absorbing properties are investigated in the frequencies during 8.2–12.4 GHz. The complex permittivity of CI particles after electroless plating Co is higher than that of raw CI particles due to improvment of the polarization process. Furthermore, according to the XRD and TG results, the Co layer can enhance the heat resistance of CI particles. The bandwidth below −10 dB can reach 3.9 GHz for the Co(CI) absorbent. The results indicate that the electroless plating Co not only enhances the absorbing properties but also improves the heat resistance of CI. - Highlights: • The Co-coated carbonyl iron Co(CI) particles were prepared by electroless plating. • The electromagnetic wave absorbing properties of Co(CI) particles were studied. • The heat treatment on the absorbing property of Co(CI) particles was studied. • The Co(CI) particles have good absorbing property when compared with CI

  19. Enhanced microwave absorbing properties and heat resistance of carbonyl iron by electroless plating Co

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hongyu, E-mail: wanghongyu07010310@163.com; Zhu, Dongmei; Zhou, Wancheng; Luo, Fa

    2015-11-01

    Co coated carbonyl iron particles (Co (CI)) are fabricated through electroless plating method, and the electromagnetic microwave absorbing properties are investigated in the frequencies during 8.2–12.4 GHz. The complex permittivity of CI particles after electroless plating Co is higher than that of raw CI particles due to improvment of the polarization process. Furthermore, according to the XRD and TG results, the Co layer can enhance the heat resistance of CI particles. The bandwidth below −10 dB can reach 3.9 GHz for the Co(CI) absorbent. The results indicate that the electroless plating Co not only enhances the absorbing properties but also improves the heat resistance of CI. - Highlights: • The Co-coated carbonyl iron Co(CI) particles were prepared by electroless plating. • The electromagnetic wave absorbing properties of Co(CI) particles were studied. • The heat treatment on the absorbing property of Co(CI) particles was studied. • The Co(CI) particles have good absorbing property when compared with CI.

  20. Comparison of shell-and-tube with plate heat exchangers for the use in low-temperature organic Rankine cycles

    International Nuclear Information System (INIS)

    Highlights: • Binary cycles for low-temperature heat sources are investigated. • Shell-and-tube and plate heat exchangers are modeled. • System optimization of the cycle variables and heat exchanger geometry. • ORCs with plate heat exchangers obtain in most cases higher efficiencies. - Abstract: Organic Rankine cycles (ORCs) can be used for electricity production from low-temperature heat sources. These ORCs are often designed based on experience, but this experience will not always lead to the most optimal configuration. The ultimate goal is to design ORCs by performing a system optimization. In such an optimization, the configuration of the components and the cycle parameters (temperatures, pressures, mass flow rate) are optimized together to obtain the optimal configuration of power plant and components. In this paper, the configuration of plate heat exchangers or shell-and-tube heat exchangers is optimized together with the cycle configuration. In this way every heat exchanger has the optimum allocation of heat exchanger surface, pressure drop and pinch-point-temperature difference for the given boundary conditions. ORCs with plate heat exchangers perform mostly better than ORCs with shell-and-tube heat exchangers, but one disadvantage of plate heat exchangers is that the geometry of both sides is the same, which can result in an inefficient heat exchanger. It is also shown that especially the cooling-fluid inlet temperature and mass flow have a strong influence on the performance of the power plant

  1. Joining and Testing Composite Plates to Ti Tubes

    Science.gov (United States)

    Morscher, Gregory N.; Singh, Mrityunjay; Shpargei, Tarah; Asthana, Rajiv

    2005-01-01

    The joining of metal tubes to composite plates is required for heat-rejection components in several space applications. Currently a number of different braze compositions are being evaluated as to their effectiveness. Such tube-plate configurations cannot be represented by traditional methods of testing, e.g., lap joints. The joined region is not between two flat surfaces, but rather between a flat surface and a curved surface. Therefore, several tests have been employed to ascertain the effectiveness of the different braze approaches in tension that are both simple and representative of the actual system and relatively straightforward in analysis. The results of these "tube-tests" will be discussed for the three different braze compositions, Cu-ABA, Ti-Cu-Sil, and Ti-Cu-Ni. In addition, fracture analysis of the failed joints was performed and offers insights into the cause of joint failure and the distinctions which need to be made between the "strength" of a joint versus the "load carrying ability" of a joint.

  2. Air-side Particulate Fouling of Microchannel Heat Exchangers: Experimental Comparison of Air-Side Pressure Drop and Heat Transfer with Plate-Fin Heat Exchanger

    OpenAIRE

    Bell, Ian; Groll, Eckhard

    2011-01-01

    In this study, the air-side pressure drop and heat transfer performance of plate-fin and microchannel coils were tested under clean and fouled conditions. The heat exchangers were tested with two different types of dust, ASHRAE Standard Dust and Arizona Road Test Dust. The ASHRAE Standard Dust was found to have a very significant impact on the pressure drop of the microchannel heat exchanger, increasing the air-side pressure drop of the microchannel heat exchanger over 200% for a dust injec...

  3. Plate fin heat exchanger model with axial conduction and variable properites

    Science.gov (United States)

    Hansen, Benjamin Jacob; White, Michael Joseph; Klebaner, Arkadiy

    2012-06-01

    Future superconduction radio frequency (SRF) cavities, as part of Project X at Fermilab,will be cooled to superfluid helium temperatures by a cryogenic distribution system supplying cold supercritical helium. To reduce vapor fraction during the final Joule Thomson (J-T) expansion into the superfluid helium cooling bath, counter-flow, plate-fin heat exchanger are an effective option. However, at liquid helium temperatures requires consideration of axial heat conduction along the direction of flow, in addition to variable fluid properties. Here we present a numberical model that includes the effects of axial guide design decisions on heat exhanger material choice and geometry. In addition, the J-T expansion process is modeled with the heat exchanger to analyze the effect of heat load and cryogenic supply parameters.

  4. On applicability of plate and shell heat exchangers for steam generation in naval PWR

    Energy Technology Data Exchange (ETDEWEB)

    Freire, Luciano Ondir, E-mail: luciano.ondir@gmail.com; Andrade, Delvonei Alves de, E-mail: delvonei@ipen.br

    2014-12-15

    Highlights: • Given emissions restrictions, nuclear propulsion may be an alternative. • Plate and shell heat exchangers (PSHE) are a mature technology on market. • PSHE are compact and could be used as steam generators. • Preliminary calculations to obtain a PWR for a large container ship are performed. • Results suggest PSHE improve overall compactness and cost. - Abstract: The pressure on reduction of gas emissions is going to raise the price of fossil fuels and an alternative to fossil fuels is nuclear energy. Naval reactors have some differences from stationary PWR because they have limitations on volume and weight, requiring compact solutions. On the other hand, a source of problems in naval reactors across history is the steam generation function. In order to reduce nuclear containment footprint, it is desirable to employ integral designs, which, however, poses complications and design constraints for recirculation type steam generators, being interesting to employ once through steam generators, whose historic at Babcock and Wilcox is better than recirculation steam generators. Plate and shell heat exchangers are a mature technology made available by many suppliers which allows heat exchange at high temperature and pressure. This work investigates the feasibility of the use of an array of welded plate heat exchangers of a material approved by ASME for pressure barrier (Ti-3Al-2.5V) in a hypothetical naval reactor. It was found it is feasible from thermal-hydraulic point of view and presents advantages over other steam generator designs.

  5. On applicability of plate and shell heat exchangers for steam generation in naval PWR

    International Nuclear Information System (INIS)

    Highlights: • Given emissions restrictions, nuclear propulsion may be an alternative. • Plate and shell heat exchangers (PSHE) are a mature technology on market. • PSHE are compact and could be used as steam generators. • Preliminary calculations to obtain a PWR for a large container ship are performed. • Results suggest PSHE improve overall compactness and cost. - Abstract: The pressure on reduction of gas emissions is going to raise the price of fossil fuels and an alternative to fossil fuels is nuclear energy. Naval reactors have some differences from stationary PWR because they have limitations on volume and weight, requiring compact solutions. On the other hand, a source of problems in naval reactors across history is the steam generation function. In order to reduce nuclear containment footprint, it is desirable to employ integral designs, which, however, poses complications and design constraints for recirculation type steam generators, being interesting to employ once through steam generators, whose historic at Babcock and Wilcox is better than recirculation steam generators. Plate and shell heat exchangers are a mature technology made available by many suppliers which allows heat exchange at high temperature and pressure. This work investigates the feasibility of the use of an array of welded plate heat exchangers of a material approved by ASME for pressure barrier (Ti-3Al-2.5V) in a hypothetical naval reactor. It was found it is feasible from thermal-hydraulic point of view and presents advantages over other steam generator designs

  6. Natural convection heat transfer of nanofluids along a vertical plate embedded in porous medium

    Science.gov (United States)

    Uddin, Ziya; Harmand, Souad

    2013-02-01

    The unsteady natural convection heat transfer of nanofluid along a vertical plate embedded in porous medium is investigated. The Darcy-Forchheimer model is used to formulate the problem. Thermal conductivity and viscosity models based on a wide range of experimental data of nanofluids and incorporating the velocity-slip effect of the nanoparticle with respect to the base fluid, i.e., Brownian diffusion is used. The effective thermal conductivity of nanofluid in porous media is calculated using copper powder as porous media. The nonlinear governing equations are solved using an unconditionally stable implicit finite difference scheme. In this study, six different types of nanofluids have been compared with respect to the heat transfer enhancement, and the effects of particle concentration, particle size, temperature of the plate, and porosity of the medium on the heat transfer enhancement and skin friction coefficient have been studied in detail. It is found that heat transfer rate increases with the increase in particle concentration up to an optimal level, but on the further increase in particle concentration, the heat transfer rate decreases. For a particular value of particle concentration, small-sized particles enhance the heat transfer rates. On the other hand, skin friction coefficients always increase with the increase in particle concentration and decrease in nanoparticle size.

  7. Strength of vacuum brazed joints for repair; Haallfasthet hos reparationer utfoerda med vakuumloedning

    Energy Technology Data Exchange (ETDEWEB)

    Berglin, Leif [Siemens Industrial Turbomachinery AB, Finspaang (Sweden)

    2005-04-01

    Strength data are missing for braze joints. Repaired components cannot fully make use of the strength of the braze, and lifetime will be underestimated. The goal of the project was to generate material data to be able to prolong the lifetime of the components. Two different material combinations were tested, 12% Chromium steel brazed with BNi-2, and a nickel base alloy, IN792 brazed with BNi-5. Tensile testing at room temperature and elevated temperature was performed in the project. Target group is purchasers and suppliers of repaired components. A tensile test specimen with butt joint was developed in the project. The used test specimen worked well for the 12% Chromium steel. The results from testing show that proof stress and tensile strength are strongly depending on the joint gap, particularly at room temperature. High strength, close to base material strength, was achieved with joint gaps smaller than 50{mu}m. For wider joint gaps, strength was lower. Strength was approximately 25% of base material strength for joint gaps over 100{mu}m. The results can be explained by changes in microstructure. Joint gaps wider than 50{mu}m showed evidence of two-phase structure. At 500 deg C, the results also showed a connection between joint gap, microstructure and strength. The generated strength data can be used for calculations of lifetime for repaired components. Two different process errors were discovered in the manufacturing process of the brazed IN792 test specimens. The generated material data are therefor erroneous. The reason for this was two manufacturing errors. The tack welding was done with too high heat input. The surfaces of the joint gap became oxidised and the oxide hindered wetting of the braze. The second reason was that the brazing was done without the prescribed hold time at maximum temperature. The melting of the braze was therefor not completed when cooling started. As a result, the strength of the IN792 specimens was low at both temperatures.

  8. Study on cold metal transfer welding–brazing of titanium to copper

    International Nuclear Information System (INIS)

    Highlights: • Cold metal transfer welding–brazing of titanium to copper was performed. • Increasing wire feed speed or groove angle will get satisfied Ti/Cu joint. • Increasing wire feed speed or groove angle will increase tensile load. • Ti/Cu CMT butt joint has dual characteristics of fusion welding and brazing. - Abstract: 3 mm Pure titanium TA2 was joined to 3 mm pure copper T2 by Cold Metal Transfer (CMT) welding–brazing process in the form of butt joint with a 1.2 mm diameter ERCuNiAl copper wire. The welding–brazing joint between Ti and Cu base metals is composed of Cu–Cu welding joint and Cu–Ti brazing joint. Cu–Cu welding joint can be formed between the Cu weld metal and the Cu groove surface, and the Cu–Ti brazing interface can be formed between Cu weld metal and Ti groove surface. The microstructure and the intermetallic compounds distribution were observed and analyzed in details. Interfacial reaction layers of brazing joint were composed of Ti2Cu, TiCu and AlCu2Ti. Furthermore, crystallization behavior of welding joint and bonding mechanism of brazing interfacial reaction were also discussed. The effects of wire feed speed and groove angle on the joint features and mechanical properties of the joints were investigated. Three different fracture modes were observed: at the Cu interface, the Ti interface, and the Cu heat affected zone (HAZ). The joints fractured at the Cu HAZ had higher tensile load than the others. The lower tensile load fractured at the Cu interface or Ti interface was attributed to the weaker bonding degree at the Cu interface or Ti interface

  9. METHODS FOR BRAZING UNUSUAL METAL COMBINATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Bertossa, Robert C.

    1963-10-15

    A method for vacuum pressure braze cladding is described. Application of the method to Mo-OFHC Cu-type 316L stainlcss steel, Ta cladding on OFHC Cu, Nb with Ni, Ti and Zr on steels, and pure Be brazing to austenitic stalnless steel are discussed. The advantages of vacuumpressure bonding are also discussed. (P.C.H.)

  10. Local heat transfer from a hot plate to a water jet

    Energy Technology Data Exchange (ETDEWEB)

    Robidou, H.; Auracher, H. [TU Berlin, Institut fuer Energietechnik, Berlin (Germany); Gardin, P.; Lebouche, M.; Bogdanic, L.

    2003-11-01

    Jet impingement boiling is very efficient in cooling of hot surfaces as a part of the impinging liquid evaporates. Because of its importance to many cooling procedures, investigations on basic mechanisms of jet impingement boiling heat transfer are needed. Until now, most of the experimental studies, carried out under steady-state conditions, used a heat flux controlled system and were limited by the critical heat flux (CHF). The present study focuses on steady-state experiments along the entire boiling curve for hot plate temperatures of up to 700 C. A test section has been built up simulating a hot plate. It is divided into 8 independently heated modules of 10 mm length to enable local heat transfer measurements. By means of temperature controlled systems for each module local steady-state experiments in the whole range between single phase heat transfer and film boiling are possible. By solving the two dimensional inverse heat conduction problem, the local heat flux and the corresponding wall temperature on the surface of each module can be computed. The measurements show important differences between boiling curves measured at the stagnation line and those obtained in the parallel flow region. At the stagnation line, the transition boiling regime is characterised by very high heat fluxes, extended to large wall superheats. Inversely, boiling curves in the parallel flow region are very near to classical ones obtained for forced convection boiling. The analysis of temperature fluctuations measured at a depth of 0.8 mm from the boiling surface enables some conclusions on the boiling mechanism in the different boiling regimes. (orig.)

  11. General-Purpose Heat Source Safety Verification Test program: Edge-on flyer plate tests

    International Nuclear Information System (INIS)

    The radioisotope thermoelectric generator (RTG) that will supply power for the Galileo and Ulysses space missions contains 18 General-Purpose Heat Source (GPHS) modules. The GPHS modules provide power by transmitting the heat of 238Pu α-decay to an array of thermoelectric elements. Each module contains four 238PuO2-fueled clads and generates 250 W(t). Because the possibility of a launch vehicle explosion always exists, and because such an explosion could generate a field of high-energy fragments, the fueled clads within each GPHS module must survive fragment impact. The edge-on flyer plate tests were included in the Safety Verification Test series to provide information on the module/clad response to the impact of high-energy plate fragments. The test results indicate that the edge-on impact of a 3.2-mm-thick, aluminum-alloy (2219-T87) plate traveling at 915 m/s causes the complete release of fuel from capsules contained within a bare GPHS module, and that the threshold velocity sufficient to cause the breach of a bare, simulant-fueled clad impacted by a 3.5-mm-thick, aluminum-alloy (5052-T0) plate is approximately 140 m/s

  12. A Compendium of Brazed Microstructures For Fission Power Systems Applications

    Science.gov (United States)

    Locci, Ivan E.; Bowman, Cheryl L.

    2012-01-01

    NASA has been supporting design studies and technology development for fission-based power systems that could provide power to an outpost on the Moon, Mars, or an asteroid. Technology development efforts have included fabrication and evaluation of components used in a Stirling engine power conversion system. This investigation is part of the development of several braze joints crucial for the heat exchanger transfer path from a hot-side heat exchanger to a Stirling engine heat acceptor. Dissimilar metal joints are required to impart both mechanical strength and thermal path integrity for a heater head of interest. Preliminary design work for the heat exchanger involved joints between low carbon stainless steel to Inconel 718, where the 316L stainless steel would contain flowing liquid metal NaK while Inconel 718, a stronger alloy, would be used as structural reinforcement. This paper addressed the long-term microstructural stability of various braze alloys used to join 316L stainless steel heater head to the high conductivity oxygen-free copper acceptor to ensure the endurance of the critical metallic components of this sophisticated heat exchanger. The bonding of the 316L stainless steel heater head material to a copper heat acceptor is required to increase the heat-transfer surface area in contact with flowing He, which is the Stirling engine working fluid.

  13. UNSTEADY FREE CONVECTIVE FLOW PAST A MOVING VERTICAL POROUS PLATE WITH NEWTONIAN HEATING

    Directory of Open Access Journals (Sweden)

    SANKAR KUMAR GUCHHAIT

    2012-07-01

    Full Text Available The unsteady free convective flow past a vertical porous plate with Newtonian heating has been studied. The governing equations have been solved numerically by Crank-Nicolson implicit finite-difference scheme. The variations of velocity and fluid temperature are presented graphically. It is found that the fluid velocity decreases with an increase in Prandtl number. Both the fluid velocity and the fluid temperature increase with an increase in suction parameter. An increase in Grashof number leads to rise in the fluid velocity. Further, it is observed that the shear stress and the rate of heat transfer at the plate increase with an increase in either Prandtlnumber or suction parameter or time.

  14. Group method analysis of two-dimensional plate in heat flux

    OpenAIRE

    Abd-el-malek, Mina B.; Fayez H. Michael; El-Mansi, Samy M. A.

    2003-01-01

    The group transformation theoretic approach is applied to present an analytic study of the temperature distribution in a triangular plate, Ω, placed in the field of heat flux, along one boundary, in a form of polynomial functions of any degree “n.” The Laplace's equation has been reduced to second-order linear ordinary differential equation with an appropriate boundary conditions. Exact solution has been obtained for general shape of Ω and different boundary conditions.

  15. Numerical Study of Heat Transfer Due to Twinjets Impingement onto an Isothermal Moving Plate

    OpenAIRE

    Başaran, Anıl; Selimefendigil, Fatih

    2013-01-01

    In this study, heat transfer from a moving isothermal hot plate due to double impinging vertical slot jets was investigated for a laminar flow. The rectangular geometry consists of a confining adiabatic wall placed parallel to the moving impingement. The jets are located symmetrically at mid point of upper wall. Water and Al2O3 nanoparticles mixture with different volumetric fraction was used as working medium. In considered jet impingement problem, the effects of the jet exit Reynolds number...

  16. Laminar film condensation heat transfer on a vertical, non-isothermal, semi-infinite plate

    CERN Document Server

    Shu, Jian-Jun

    2014-01-01

    This paper gives similarity transformations for laminar film condensation on a vertical flat plate with variable temperature distribution and finds analytical solutions for arbitrary Prandtl numbers and condensation rates. The work contrasts with Sparrow and Gregg's assertion that wall temperature variation does not permit similarity solutions. To resolve the long debatable issue regarding heat transfer of non-isothermal case, some useful formulas are obtained, including significant correlations for varying Prandtl numbers. Results are compared with the available experimental data.

  17. Heat Transfer on Steady MHD rotating flow through porous medium in a parallel plate channel

    OpenAIRE

    Dr. G. Prabhakara Rao,; M. Naga Sasikala

    2015-01-01

    We discussed the combined effects of radiative heat transfer and a transverse magnetic field on steady rotating flow of an electrically conducting optically thin fluid through a porous medium in a parallel plate channel and non-uniform temperatures at the walls. The analytical solutions are obtained from coupled nonlinear partial differential equations for the problem. The computational results are discussed quantitatively with the aid of the dimensionless parameters entering in t...

  18. Heat Transfer on Steady MHD rotating flow through porous medium in a parallel plate channel

    Directory of Open Access Journals (Sweden)

    Dr. G. Prabhakara Rao,

    2015-04-01

    Full Text Available We discussed the combined effects of radiative heat transfer and a transverse magnetic field on steady rotating flow of an electrically conducting optically thin fluid through a porous medium in a parallel plate channel and non-uniform temperatures at the walls. The analytical solutions are obtained from coupled nonlinear partial differential equations for the problem. The computational results are discussed quantitatively with the aid of the dimensionless parameters entering in the solution.

  19. High-Power Laser Cutting of Steel Plates: Heat Affected Zone Analysis

    OpenAIRE

    Imed Miraoui; Mohamed Boujelbene; Mouna Zaied

    2016-01-01

    The thermal effect of CO2 high-power laser cutting on cut surface of steel plates is investigated. The effect of the input laser cutting parameters on the melted zone depth (MZ), the heat affected zone depth (HAZ), and the microhardness beneath the cut surface is analyzed. A mathematical model is developed to relate the output process parameters to the input laser cutting parameters. Three input process parameters such as laser beam diameter, cutting speed, and laser power are investigated. M...

  20. Heat transfer for flow of a third-grade fluid between two porous plates

    Energy Technology Data Exchange (ETDEWEB)

    Hayat, Tasawar [Quaid-i-Azam Univ., Islamabad (Pakistan). Dept. of Mathematics; King Saud Univ., Riyadh (Saudi Arabia). Dept. of Mathematics; Naz, Rahila [Quaid-i-Azam Univ., Islamabad (Pakistan). Dept. of Mathematics; Sajid, Muhammad [PINSTECH, Islamabad (Pakistan). Theoretical Plasma Physics Div.

    2010-10-15

    This article concentrates on the analytic solution for the heat transfer analysis of a third-grade fluid between two porous plates. The nonlinear problem for velocity profile is solved by employing the homotopy analysis method (HAM). Using the velocity profile, the energy equation with dissipation effects is solved for the series solution. The present solution demonstrates the dependency of the viscoelastic parameters. The obtained results are also sketched and discussed. (orig.)

  1. Development of flat-plate solar collectors for the heating and cooling of buildings: Executive summary

    Science.gov (United States)

    1978-01-01

    An efficient, low cost, flat-plate solar collector was developed. Computer aided mathematical models of the heat process in the collector were used in defining absorber panel configuration; determining insulation thickness; and in selecting the number, spacing, and material of the covers. Prototypes were built and performance tested. Data from simulated operation of the collector are compared with predicted loads from a number of locations to determine the degree of solar utilization.

  2. Analytic Approximations for the Flows and Heat Transfer in Microchannels between Two Parallel Plates

    OpenAIRE

    A. El-Nahhas

    2012-01-01

    We consider the nonlinear problem for the flow of Newtonian fluid in a microchannel between two parallel plates with the effects of velocity slip, viscous dissipation, and temperature jump at the wall. This problem is modelled by both the Navier-Stokes equation and energy equation with two thermal boundary conditions related to the two cases: the constant wall temperature (CWT) and the constant heat flux (CHF). The homotopy analysis method is applied via a polynomial exponential basis to obta...

  3. Heat Transfer Analysis of a Flat-plate Solar Collector Running a Solid Adsorption Refrigerator

    Directory of Open Access Journals (Sweden)

    S. Thiao

    2014-05-01

    Full Text Available Adsorption solar cooling appears to have prospect in the tropical countries. The present study is a theoretical investigation of the performance of a solar adsorption refrigerator using a flat-plate solar collector. The values of glass cover and absorber plate temperatures obtained from numerical solutions of heat balance equations are used to predict the solar coefficient of performance of the solar refrigerator. The simulation technique takes into account the variations of ambient temperature and solar radiation along the day. The effects of optical parameters of the glass cover such as absorption and transmission coefficients on glass cover and absorber plate temperatures and consequently on the coefficient of performance are analyzed. As a result, it is found that the absorber plate temperature is less to the absorption coefficient than the cover glass temperature. Also the thermal radiation exchange has more effect on the cover glass temperature. The higher values of COP are obtained between 11 and 13 h during the morning when the temperatures of the absorber plate and the ambient temperatures increase. Moreover the COP increases with the coefficient of transmission of the glass cover but the main parameter acting on the variations of the COP remains the temperature of the evaporator.

  4. A form of MHD universal equations of unsteady incompressible fluid flow with variable elctroconductivity on heated moving plate

    Directory of Open Access Journals (Sweden)

    Boričić Zoran

    2005-01-01

    Full Text Available This paper deals with laminar, unsteady flow of viscous, incompressible and electro conductive fluid caused by variable motion of flat plate. Fluid electro conductivity is variable. Velocity of the plate is time function. Plate moves in its own plane and in "still" fluid. Present external magnetic filed is perpendicular to the plate. Plate temperature is a function of longitudinal coordinate and time. Viscous dissipation, Joule heat, Hole and polarization effects are neglected. For obtaining of universal equations system general similarity method is used as well as impulse and energy equation of described problem.

  5. PLATE

    DEFF Research Database (Denmark)

    Kling, Joyce; Hjulmand, Lise-Lotte

    2008-01-01

    Project in Language Assessment for Teaching in English (PLATE) language professionals from CBS’s Language Center observe teachers and provide feedback using evaluation criteria from the Common European Framework for Reference (CEFR) supplemented by some additional criteria which take the LSP nature of......Copenhagen Business School (CBS) finds itself needing to address the issue of English-medium instruction for its increasing number of foreign exchange and full degree students. With internationalisation as a main pillar of the institution’s agenda, there are concerns whether the teaching faculty......’s level of English is sufficient for the increasing number of courses offered in English each semester. This paper addresses these concerns and describes a pilot project initiated in 2003 at CBS to gauge the overall English language proficiency of those teaching content courses in English. Through the...

  6. Thermal performance of plate-fin heat exchanger using passive techniques: vortex-generator and nanofluid

    Science.gov (United States)

    Khoshvaght-Aliabadi, Morteza

    2016-04-01

    This experimental study investigates the effects of vortex-generator (VG) and Cu/water nanofluid flow on performance of plate-fin heat exchangers. The Cu/water nanofluids are produced by using a one-step method, namely electro-exploded wire technique, with four nanoparticles weight fractions (i.e. 0.1, 0.2, 0.3, and 0.4 %). Required properties of nanofluids are systematically measured, and empirical correlations are developed. A highly precise test loop is fabricated to obtain accurate results of the heat transfer and pressure drop characteristics. Experiments are conducted for nanofluids flow inside the plain and VG channels. Based on the experimental results, utilizing the VG channel instead of the plain channel enhances the heat transfer rate, remarkably. Also, the results show that the VG channel is more effective than the nanofluid on the performance of plate-fin heat exchangers. It is observed that the combination of the two heat transfer enhancement techniques has a noticeably high thermal-hydraulic performance, about 1.67. Finally, correlations are developed to predict Nusselt number and friction factor of nanofluids flow inside the VG channel.

  7. Natural Convection Heat and Mass Transfer Flow with Hall Current, Rotation, Radiation and Heat Absorption Past an Accelerated Moving Vertical Plate with Ramped Temperature

    Directory of Open Access Journals (Sweden)

    Gauri Shanker Seth

    2015-01-01

    Full Text Available An investigation of unsteady hydromagnetic natural convection heat and mass trans fer flow with Hall current of a viscous, incompressible, electrically conducting, heat absorbing and optically thin radiating fluid past an accelerated moving vertical plate through fluid saturated porous medium in a rotating environment is carried out when temperature of the plate has a temporarily ramped profile. The exact solutions of momentum, energy and concentration equations are obtained in closed form by Laplace transform technique. The expressions of skin friction, Nusselt number and Sherwood number are also derived. For both ramped temperature and isothermal plates, Hall current tends to accelerate primary and secondary fluid velocities whereas heat absorption and radiation have reverse effect on it. Rotation tends to retard primary fluid velocity whereas it has a reverse effect on secondary fluid velocity. Heat absorption and radiation have tendency to enhance rate of heat transfer at the plate.

  8. Local heat transfer coefficients during the evaporation of 1,1,1,2-tetrafluoroethane (R-134a in a plate heat exchanger

    Directory of Open Access Journals (Sweden)

    EMILA ŽIVKOVIĆ

    2009-04-01

    Full Text Available The evaporation heat transfer coefficient of the refrigerant R-134a in a vertical plate heat exchanger was investigated experimentally. The area of the plate was divided into several segments along the vertical axis. For each of the segments, the local value of the heat transfer coefficient was calculated and presented as a function of the mean vapor quality in the segment. Owing to the thermocouples installed along the plate surface, it was possible to determine the temperature distribution and vapor quality profile inside the plate. The influences of the mass flux, heat flux, pressure of system and the flow configuration on the heat transfer coefficient were also taken into account and a comparison with literature data was performed.

  9. Tensile Creep Properties of the 50Au-50Cu Braze Alloy

    International Nuclear Information System (INIS)

    The 50Au-50CU (wt.%) alloy is a solid-solution strengthened braze alloy used extensively in conventional, hermetic metal/ceramic brazing applications where low vapor pressure is a requirement. Typical metal/ceramic base materials would be KovarTM alloy and metallized and Ni-plated 94% alumina ceramic. The elevated temperature mechanical properties are important for permitting FEA evaluation of residual stresses in metal/ceramic brazes given specific geometries and braze cooldown profiles. For material with an atomic composition of 76.084 at.% CL 23.916 Au (i.e., on the Cu-rich side of Cu3Au) that was annealed for 2 hr. at 750 ampersand deg;C and water quenched a Garofalo sinh equation was found to adequately characterize the minimum strain rate data over the temperature mnge 450-850 ampersand deg;C. At lower temperatures (250 arid 350 ampersand deg;C), a conventional power law equation was found to characterize the data. For samples held long periods of time at 375 ampersand deg;C (96 hrs.) and slowly cooled to room temperature, a slight strengthening reaction was observed: with the stress necessary to reach the same strain rate increasing by about 15% above the baseline annealed and quenched data. X-ray diffiction indicates that the 96 hr at 375 ampersand deg;C + slow cool condition does indeed order. The microhardness of the ordered samples indicates a value of 94.5 VHN, compared to 93.7 VHN for the baseline annealed and quenched (disordered FCC) samples. From a brazing perspective, the relative sluggishness of this ordering reaction does not appear to pose a problem for braze joints cooled at reasonable rates following brazing

  10. Theoretical and experimental investigation of plate screen mesh heat pipe solar collector

    International Nuclear Information System (INIS)

    Highlights: • Experimental and computer simulation are performed for wicked heat pipe solar collectors. • Outdoor tests are conducted to compare its performance at different period of the year. • Modest improvement of the collector is achievement by adding fins to the condenser region. • Mesh number of heat pipe porous structure is an important factor in collector design. • Water slightly outperform methanol for such design and operating conditions. - Abstract: Heat pipes are efficient heat transfer devices for solar hot water heating systems. However, the effective downward transfer of solar energy in an integrated heat pipe system provides increased design and implementation options. There is a lack of literature about flat plate wicked assisted heat pipe solar collector, especially with the presence of finned water-cooled condenser wicked heat pipes for solar energy applications. In this paper the consequence of incorporating fins arrays into the condenser region of screen mesh heat pipe solar collector is investigated. An experimental and a transient theoretical model are conducted to compare the performances of solar heating system at different period of the year. A good agreement is shown between the model and the experiment. Two working fluids are investigated (water and methanol) and results reveal that water slightly outperforms methanol with a collector instantaneous efficiency of nearly 60%. That modest improvement is achieved by adding fins to the condenser region of the heat pipes. Results show that the collector efficiency increase as the number of fins increases (upon certain number) and reveal that the mesh number is an important factor which affect the overall collector efficiency. An optimal heat pipe mesh number of 100 meshes/in. with two layers appears to be favorable in such collectors for their design and operating conditions

  11. Experimental study on Transient Natural Convection in a Cube Enclosure with an Isolated Vertical Cyclically Heated Plate

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The low frequency cyclical transient natural convection in a cube enclosure with an internal isolated vertical heated plate was investigated experimentally.A computer-aided experimental system was designed to generate the cyclical heating power input and also used for data reduction.The effects of the cyclic heating power input amplitude(from 0 to 8 W) and frequency(form 1/5400s-1 to 1/600s-1) as well as the per-cycle time-average power input(from 8 to 24 W)on the transient and time-average Nusselt number were parametrically studied.It was found that for such cyclical transient natural convection with low frequency,the plate heating power input amplitude and frequency have little effects on the time-average Nusselt number as long as the cyclical time-average heating power input remains the same,although the transient Nusselt number may be significantly affected.Therefore,the modified Grashof number based on the plate average heat flux can be used to characterize the time-average heat transfer process.The plate time-average Nusselt number is about 15% less than the infinite-space Nusselt number,The location of the isolated plate in enclosure does not appreciably influence the time-average heat transfer characteristics of the plate.

  12. Laser hybrid brazing of oxide ceramics for high temperature gas sensing applications in (V)HTRS

    International Nuclear Information System (INIS)

    It has been shown that the use of halogen lamps to assist laser brazing reduces total energy and joining time. For parts with specific geometries not suitable for a rotation process, an assistive heating with halogen lamps might be even more beneficial, to alleviate temperature gradients and transients. Forsterite-based ceramics are highly suitable as a joining partner for ZrO2, especially in a laser brazing process based on volume heating. By adding Fe2O3 to the raw powder mixture, the absorptivity of the forsterite ceramic can be tuned with an optimum at 0.1 wt.% Fe, reducing the necessary laser energy input even more. (orig.)

  13. Influence of Tip Clearance on Forced Convection Heat Transfer of a Finned Plate in a Duct

    International Nuclear Information System (INIS)

    Optimizations are required for a proper enhancement of cooling capability. An important phenomenological consideration is to be reveals for a finned plate in a duct. Due to the high friction near the fin region and low friction near the wall region, the forced flow tends to bypass from fin region to wall region. The bypass flow increases the net flow and enhances the heat transfer for a moderate tip clearance which is defined by the distance from the tip of the fin and the wall. Meanwhile for a large tip clearance, most of the flow bypasses and does not contribute the heat transfer and impairs the heat transfer. This study is a preliminary numerical study on the influence of the tip clearance on the heat transfer of the finned plate in a duct. The study aimed at supporting an experimental research exploring the phenomena for a very small tip clearance. Thus material properties and test conditions were chosen to meet the experimental conditions. It investigated the phenomena at Pr of 2,014 and ReS of 58.3. In order to investigate the small tip clearance phenomena, a simple numerical scheme was developed using a commercial CFD code. A case with the same experimental condition was tested using the numerical scheme and the error was about 12%. The results show the clear evidence of the flow bypass from the fin region to wall region, which impair the heat removal capacity of the finned plate in a duct. The study has the relevance with the reactor cavity cooling system performance enhancement activities in the VHTR. The numerical scheme will be tested for narrower and wider tip clearances and find an optimal tip clearance

  14. Influence of Tip Clearance on Forced Convection Heat Transfer of a Finned Plate in a Duct

    Energy Technology Data Exchange (ETDEWEB)

    Park, Haekyun; Chung, Bumjin [Kyung Hee Univ., Yongin (Korea, Republic of)

    2014-05-15

    Optimizations are required for a proper enhancement of cooling capability. An important phenomenological consideration is to be reveals for a finned plate in a duct. Due to the high friction near the fin region and low friction near the wall region, the forced flow tends to bypass from fin region to wall region. The bypass flow increases the net flow and enhances the heat transfer for a moderate tip clearance which is defined by the distance from the tip of the fin and the wall. Meanwhile for a large tip clearance, most of the flow bypasses and does not contribute the heat transfer and impairs the heat transfer. This study is a preliminary numerical study on the influence of the tip clearance on the heat transfer of the finned plate in a duct. The study aimed at supporting an experimental research exploring the phenomena for a very small tip clearance. Thus material properties and test conditions were chosen to meet the experimental conditions. It investigated the phenomena at Pr of 2,014 and ReS of 58.3. In order to investigate the small tip clearance phenomena, a simple numerical scheme was developed using a commercial CFD code. A case with the same experimental condition was tested using the numerical scheme and the error was about 12%. The results show the clear evidence of the flow bypass from the fin region to wall region, which impair the heat removal capacity of the finned plate in a duct. The study has the relevance with the reactor cavity cooling system performance enhancement activities in the VHTR. The numerical scheme will be tested for narrower and wider tip clearances and find an optimal tip clearance.

  15. A corrosion study on vacuum brazed joints of LINAC

    International Nuclear Information System (INIS)

    A 10 MeV, S-band electron linac has been developed at RRCAT for industrial applications. At present, the in-house fabricated accelerating structure, is under continuous operation and has been tested at beam power more than 4.2 kW. The accelerating structure of electron linac comprises RF couplers, buncher section and regular section. The accelerating structure is made of OFE copper and is fabricated by vacuum brazing of cavities and coupler components using BVAg-8 and Palcusil-5 as braze filler metals (BFM). During accelerator operation, RF power is dissipated on cavities surface and the resultant heat is removed by circulating low conductivity water (LCW) in cooling jackets built around the accelerating structure whose inner part is maintained under vacuum. Corrosion characteristics of OFE copper brazed joints in LCW environment is of utmost importance towards development of reliable industrial linac. Therefore, a study has been undertaken to investigate corrosion possibilities in the cooling circuit which can limit the life of accelerating structures

  16. Experimental study and calculation of boiling heat transfer on steel plates during runout table operation

    International Nuclear Information System (INIS)

    Within a hot strip steel mill, red hot steel is hot rolled into a long continuous slab that is led onto what is called the runout table. Temperatures of the steel at the beginning of this table are around 900 oC. Above and below the runout table are banks of water jets, sprays or water curtains that rapidly cool the steel slab. The heat transfer process itself may be considered one of the most complicated in the industrial world. The cooling process that occurs on the runout table is crucial and governs the final mechanical properties and flatness of a steel strip. However, very limited data of industrial conditions has been available and that which is available is poorly understood. To study heat transfer during runout table cooling, an industrial scale pilot runout table facility was constructed at the University of British Columbia (UBC). This paper describes the experimental details, data acquisition and data handling techniques for steel plates during water jet impingement cooling by one circular water jet from industrial headers. The effect of cooling water temperature and initial steel plate temperature as well as varying water jet diameters on heat transfer was systematically investigated. A two-dimensional finite element scheme based inverse heat conduction model was developed to calculate surface heat transfer coefficients along the impinging surface. Heat flux curves at the stagnation area were obtained for selected tests. A quantitative relationship between adjustable processing parameters and heat transfer coefficients along the impinging surface during runout table operation is discussed. The results of the study were used to upgrade an extensive process model developed at UBC. The model ties in the cooling rate and hence two dimensional temperature gradients to the resulting microstructure and final mechanical properties of the steel. This process model is widely used by major steel industries in Canada and the United States. (author)

  17. Theory and modeling of active brazing.

    Energy Technology Data Exchange (ETDEWEB)

    van Swol, Frank B.; Miller, James Edward; Lechman, Jeremy B.; Givler, Richard C.

    2013-09-01

    Active brazes have been used for many years to produce bonds between metal and ceramic objects. By including a relatively small of a reactive additive to the braze one seeks to improve the wetting and spreading behavior of the braze. The additive modifies the substrate, either by a chemical surface reaction or possibly by alloying. By its nature, the joining process with active brazes is a complex nonequilibrium non-steady state process that couples chemical reaction, reactant and product diffusion to the rheology and wetting behavior of the braze. Most of the these subprocesses are taking place in the interfacial region, most are difficult to access by experiment. To improve the control over the brazing process, one requires a better understanding of the melting of the active braze, rate of the chemical reaction, reactant and product diffusion rates, nonequilibrium composition-dependent surface tension as well as the viscosity. This report identifies ways in which modeling and theory can assist in improving our understanding.

  18. Heat Transfer with Flow and Phase Change in an Evaporator of Miniature Flat Plate Capillary Pumped Loop

    Institute of Scientific and Technical Information of China (English)

    Zhongmin WAN; Wei LIU; Zhaoqing ZHENG; A. Nakayama

    2007-01-01

    An overall two-dimensional numerical model of the miniature flat plate capillary pumped loop (CPL) evaporator is developed to describe the liquid and vapor flow, heat transfer and phase change in the porous wick structure,liquid flow and heat transfer in the compensation cavity and heat transfer in the vapor grooves and metallic wall.The entire evaporator is solved with SIMPLE algorithm as a conjugate problem. The effect of heat conduction of metallic side wall on the performance of miniature flat plate CPL evaporator is analyzed, and side wall effect heat transfer limit is introduced to estimate the performance of evaporator. The shape and location of vapor-liquid interface inside the wick are calculated and the influences of applied heat flux, liquid subcooling, wick material and metallic wall material on the evaporator performance are investigated in detail. The numerical results obtained are useful for the miniature flat plate evaporator performance optimization and design of CPL.

  19. Ultrasonic inspection of tube to tube plate welds

    International Nuclear Information System (INIS)

    To monitor the deterioration of a weld between a tube and tube plate which has been repaired by a repair sleeve inside the tube and brazed at one end to the tube, ultrasound from a crystal at the end of a rod is launched, in the form of Lamb-type waves, into the tube through the braze and allowed to travel along the tube to the weld and be reflected back along the tube. The technique may also be used for the type of heat exchanger in which, during construction, the tubes are welded to the tube plate via external sleeves in which case the ultrasound is used in a similar manner to inspect the sleeve/tube plate weld. an electromagnetic transducer may be used to generate the ultrasound. The ultrasonic head comprising the crystal and an acoustic baffle is mounted on a Perspex (RTM) rod which may be rotated by a stepping motor. Echo signals from the region of deterioration may be isolated by use of a time gate in the receiver. The device primarily detects circumferentially orientated cracks, and may be used in heat exchangers in nuclear power plants. (author)

  20. Development of flat-plate solar collectors for the heating and cooling of buildings

    Science.gov (United States)

    Ramsey, J. W.; Borzoni, J. T.; Holland, T. H.

    1975-01-01

    The relevant design parameters in the fabrication of a solar collector for heating liquids were examined. The objective was to design, fabricate, and test a low-cost, flat-plate solar collector with high collection efficiency, high durability, and requiring little maintenance. Computer-aided math models of the heat transfer processes in the collector assisted in the design. The preferred physical design parameters were determined from a heat transfer standpoint and the absorber panel configuration, the surface treatment of the absorber panel, the type and thickness of insulation, and the number, spacing and material of the covers were defined. Variations of this configuration were identified, prototypes built, and performance tests performed using a solar simulator. Simulated operation of the baseline collector configuration was combined with insolation data for a number of locations and compared with a predicted load to determine the degree of solar utilization.

  1. Effect of controlling parameters on heat transfer during spray impingement cooling of steel plate

    Directory of Open Access Journals (Sweden)

    Purna C. Mishra

    2013-09-01

    Full Text Available The heat transfer characteristics of air-water spray impingement cooling of stationary steel plate was experimentally investigated. Experiments were conducted on an electrically heated flat stationary steel plate of dimension 120 mm x 120 mm x 4 mm. The controlling parameters taken during the experiments were airwater pressures, water flow rate, nozzle tip to target distance and mass impingement density. The effects of the controlling parameters on the cooling rates were critically examined during spray impingement cooling. Air assisted DM water was used as the quenchant media in the work. The cooling rates were calculated from the time dependent temperature profiles were recorded by NI-cRIO DAS at the desired locations of the bottom surface of the plate embedded with K-type thermocouples. By using MS-EXCEL the effects of these cooling rate parameters were analysed The results obtained in the study confirmed the higher efficiency of the spray cooling system and the cooling strategy was found advantageous over the conventional cooling methods in the present steel industries

  2. Adsorption kinetics and isotherms of zeolite coatings directly crystallized on fibrous plates for heat pump applications

    International Nuclear Information System (INIS)

    Zeolite A coatings were grown on porous fibrous metal plates by using the substrate heating synthesis method. The coatings prepared were characterized by X-ray diffraction (XRD) and laser microscopy. Kinetic measurements were performed to determine the rates of adsorption of these materials while their adsorption isotherms were obtained by thermogravimetry (TG). The overall adsorption kinetics varied with the different samples investigated. The zeolite A coating grown on a copper fibrous support generally exhibited superior overall adsorption kinetics compared to a zeolite X coating with close mass, prepared previously on a stainless steel flat plate. The coating thickness as well as the support properties affected the performances of the samples. The inclusion of an additional polymer layer exhibited adverse impact on the kinetics especially after relatively high normalized loadings. The adsorption isotherms obtained for the zeolite coatings on fibrous supports were quite typical for zeolite A while the addition of polymer changed the isotherm type. -- Highlights: • Thick zeolite A coatings were grown on fibrous metal plates. • Use of fibrous supports improved heat transfer quality. • Coating thickness influenced adsorption kinetics notably. • Inclusion of an additional polymer layer changed kinetics and isotherm type

  3. Direct metal brazing to cermet feedthroughs

    International Nuclear Information System (INIS)

    An improved method for brazing metallic components to a cermet surface in an alumina substrate eliminates the prior art metallized layer over the cermet via and adjoining alumina surfaces. Instead, a nickel layer is applied over the cermet surface only and metallic components are brazed directly to this nickel coated cermet surface. As a result, heretofore unachievable tensile strength joints are produced. In addition, cermet vias with their brazed metal components can be spaced more closely in the alumina substrate because of the elimination of the prior art metallized alumina surfaces

  4. Analysis and repair of cracking in partition plate of RHR heat exchanger at Brunsbuettel nuclear power station

    International Nuclear Information System (INIS)

    According to Germany's pressure vessel code, the residual heat removal (RHR) heat exchangers of System TH installed at Brunsbuettel nuclear power station must be subjected to an internal examination every 4 years. This inspection was carried out for heat exchanger TH35 B101 on October 21, 1994. In the course of the examination, the sealing strips at the channel cover were found to be slightly deformed. Replacement of the sealing strips required removal not only of these strips but also of another strip which holds the sealing strips in place and is bolted to the channel partition plate. After all of the strips had been removed, a crack was discovered at the weld joining the partition plate to the channel shell. The metallographic and fractographic examinations as well as the mathematical root-cause analyses showed that the fracture was caused by alternating bending stresses. At the top of the partition plate, a maximum stress intensity of 932 MPa was found in the region of the incipient crack. A new adequately sized partition plate with a wall thickness of 20 mm was installed to support the old plate, which is only required in the future to serve as a leak-tight barrier. The new partition plate is held in place by eccentric-head bolts at the tubesheet and metal strips at the channel cover. This concept enabled the partition plates in the TH heat exchangers to be quickly repaired and restored the full functional capability of these heat exchangers. (orig.)

  5. NUMERICAL AND EXPERIMENTAL INVESTIGATION OF HEAT TRANSFER OF ZnO/WATER NANOFLUID IN THE CONCENTRIC TUBE AND PLATE HEAT EXCHANGERS

    OpenAIRE

    Mohammad Reza Talaie; Masoud Haghshenas Fard; Somaye Nasr

    2011-01-01

    The plate and concentric tube heat exchangers are tested by using the water-water and nanofluid-water streams. The ZnO/Water (0.5%v/v) nanofluid has been used as the hot stream. The heat transfer rate omitted of hot stream and overall heat transfer coefficients in both heat exchangers are measured as a function of hot and cold streams mass flow rates. The experimental results show that the heat transfer rate and heat transfer coefficients of the nanofluid in both of the heat exchangers is hig...

  6. Thermal stresses induced by a point heat source in a circular plate by quasi-static approach

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The present paper deals with the determination of quasi-static thermal stresses due to an instantaneous point heat source of strength g_(pi) situated at certain circle along the radial direction of the circular plate and releasing its heat spontaneously at time t=τ.A circular plate is considered having arbitrary initial temperature and subjected to time dependent heat flux at the fixed circular boundary of r=b.The governing heat conduction equation is solved by using the integral transform method,and res...

  7. A comparison of micro-structured flat-plate and cross-cut heat sinks for thermoelectric generation application

    DEFF Research Database (Denmark)

    Rezania, Alireza; Rosendahl, L. A.

    2015-01-01

    Heat sink configuration has strong impact on net power output from thermoelectric generators (TEGs). A weak cooling strategy can even cause negative net power output from the thermoelectric device. However, the net power output can be significantly improved by optimal design of the heat sink. In...... this study, a micro-structured plate-fin heat sink is compared to a modified design of cross-cut heat sink applied to TEGs over a range of temperatures and thermal conductivities. The particular focus of this study is to explore the net power output from the TEG module. The three-dimensional governing......-fin heat sink is higher, while the TEG with cross-cut heat sink has higher maximum net power output at high flow inlet velocity. The maximum net power output is equal in the TEGs with plate-fin heat sink and cross-cut heat sink....

  8. Influence of technological conditions during vacuum brazing on the aggressive behaviour of nickel brazing filler metal

    International Nuclear Information System (INIS)

    The effect of brazing temperature 1080, 1120 and 11900C and dwell at those temperatures in the range 1, 5, 30 and 180 min. as well as additional annealing at 10500C/120 min. on the degree of erosion and diffusion of 5 types of alloyed steels and also on the character of brazing alloy structure formation with the use of five Ni-based high temperature brazing alloys. On the basis of attained results of experimental investigation the general optimum conditions of vacuum brazing are determined. (orig.)

  9. Numerical investigation on a novel shell-and-tube heat exchanger with plate baffles and experimental validation

    International Nuclear Information System (INIS)

    Highlights: • A novel shell-and-tube heat exchanger with plate baffles is proposed. • Heat transfer and pressure drop of computational calculations are studied. • Experimental method is carried out to verify the modeling approach. • Path lines, temperature field and pressure field are analyzed. - Abstract: A novel shell-and-tube heat exchanger with new plate baffles is proposed. It is numerically investigated in comparison with a shell-and-tube heat exchanger with rod baffles. Commercial softwares FLUENT 6.3 and GAMBIT 2.3 are adopted for modeling and computational calculations. The modeling approach is verified with experimental approach. The shell-side results of heat transfer, flow performance, and comprehensive performance are analyzed. The Nusselt number for the plate baffles heat exchanger is around 128–139% of that for the rod baffles heat exchanger. The pressure drop for the novel one is about 139–147% of that for the rod baffles heat exchanger. Overall, the novel plate baffles heat exchanger illustrates evidently higher comprehensive performance (115–122%) than the rod baffles one. The temperature field, pressure field, and path lines are analyzed to demonstrate the advantage of the novel shell-and-tube heat exchanger

  10. Natural Convection Flow along an Isothermal Vertical Flat Plate with Temperature Dependent Viscosity and Heat Generation

    Directory of Open Access Journals (Sweden)

    Md. Mamun Molla

    2014-01-01

    Full Text Available The purpose of this study is to investigate the natural convection laminar flow along an isothermal vertical flat plate immersed in a fluid with viscosity which is the exponential function of fluid temperature in presence of internal heat generation. The governing boundary layer equations are transformed into a nondimensional form and the resulting nonlinear system of partial differential equations is reduced to a convenient form which are solved numerically using an efficient marching order implicit finite difference method with double sweep technique. Numerical results are presented in terms of the velocity and temperature distribution of the fluid as well as the heat transfer characteristics, namely, the wall shear stress and the local and average rate of heat transfer in terms of the local skin-friction coefficient, the local and average Nusselt number for a wide range of the viscosity-variation parameter, heat generation parameter, and the Rayleigh number. Increasing viscosity variation parameter and Rayleigh number lead to increasing the local and average Nusselt number and decreasing the wall shear stress. Wall shear stress and the rate of heat transfer decreased due to the increase of heat generation.

  11. Numerical simulation of side heating for controlling angular distortion in multipass MMAW butt welded plates

    Indian Academy of Sciences (India)

    Adinath V Damale; Keshav N Nandurkar

    2015-04-01

    Distortion is a severe problem in weld products.It depends on various process parameters like plate thickness, current, voltage, type of weld joint and restraints put on. If distortion is not properly dealt during welding then the product may become useless from geometric accuracy point of view. In the present study, a 3-D coupled transient thermal analysis model with auxiliary side heating (parallel heating) is developed to control angular distortion. During analysis, parallel heating flames are placed at several locations from weld line in cross direction. A user defined subroutine is used to apply transient heat source and side heating flames. Element birth and death technique is used to simulate the filler material deposition. One side multipass 'V' butt weld configuration is used for this study. A series of observational tests are done with a special experimental fixture using Manual Metal Arc Welding (MMAW) to validate the proposed FEA model. It is found that the angular distortion has decreased from 2 mm to 0.4 mm with change in side heating distance from 50 to 90 mm from the weld line.

  12. Ohmic Heating and Viscous Dissipation Effects over a Vertical Plate in the Presence of Porous Medium

    Directory of Open Access Journals (Sweden)

    LOGANATHAN PARASURAM

    2016-01-01

    Full Text Available An analysis is performed to investigate the ohmic heating and viscous dissipation effects on an unsteady natural convective flow over an impulsively started vertical plate in the presence of porous medium with radiation and chemical reaction. Numerical solutions for the governing boundary layer equations are presented by finite difference scheme of the Crank Nicolson type. The influence of various parameters on the velocity, the temperature, the concentration, the skin friction, the Nusselt number and the Sherwood number are discussed. It is observed that velocity and temperature increases with increasing values of permeability and increasing values of Eckert number, whereas it decreases with increasing values of magnetic parameter. An increase in ohmic heating and viscous heating increases the velocity boundary layer. An increase in ohmic heating decreases the temperature. An increase in magnetic field reduces the temperature profile. The velocity profile is highly influenced by the increasing values of permeability. It is observed that permeability has strong effect on velocity. An enhancement in ohmic heating increases the shear stress, decreases the rate of heat transfer and induces the rate of mass transfer.

  13. Mathematical modeling and control of plate fin and tube heat exchangers

    International Nuclear Information System (INIS)

    Highlights: • A method for numerical modeling of plate fin and tube heat exchangers was proposed. • A numerical model of an automobile radiator was developed. • Numerical models of the radiator were compared with an exact analytical model. • A model-based control system of water outlet temperature was built and tested. • A digital proportional–integral–derivative controller of heat exchanger was tested. - Abstract: The aim of the study is to develop a new method for numerical modeling of tubular cross-flow heat exchangers. Using the method proposed in the paper, a numerical model of a car radiator was developed and implemented in a digital control system of the radiator. To evaluate the accuracy of the numerical method proposed in the paper, the numerical model of the car radiator was compared with an analytic model. The proposed method based on a finite volume method and integral averaging of gas temperature across a tube row is appropriate for modeling of plate fin and tube heat exchangers, especially for exchangers in which substantial gas temperature differences in one tube row occur. The target of control is to regulate the number of fan revolutions per minute so that the water temperature at the heat exchanger outlet is equal to a set value. Two control techniques were developed. The first is based on the numerical model of the heat exchanger developed in the paper while the second is a digital proportional–integral–derivative control. The first control method is very stable. The digital proportional–integral–derivative controller becomes unstable when the water volume flow rate varies considerably. The developed techniques were implemented in digital control system of the water exit temperature in a plate fin and tube heat exchanger. The measured exit temperature of the water was very close to the set value of the temperature if the first method was used. The experiments show that the proportional–integral–derivative controller

  14. Comparative design evaluation of plate fin heat exchanger and coiled finned tube heat exchanger for helium liquefier in the temperature range of 300-80 K

    International Nuclear Information System (INIS)

    Present indigenous helium liquefaction system at RRCAT uses the cross-counter flow coiled-finned tube heat exchangers developed completely from Indian resources. These coiled-finned tube heat exchangers are mainly suitable up to medium capacity helium liquefiers. For large capacity helium liquefier, plate fin heat exchangers are more suitable options. This paper presents the comparative evaluation of the design of both types of heat exchangers in the temperature range of 300-80 K for helium liquefier. (author)

  15. Numerical estimation of heat transfer characteristics for two-row plate-finned tube heat exchangers with experimental data

    Science.gov (United States)

    Chen, Han-Taw; Lu, Chih-Han; Huang, Yao-Sheng; Liu, Kuo-Chi

    2016-05-01

    This study applies a three-dimensional computational fluid dynamics commercial software in conjunction with various flow models to estimate the heat transfer and fluid flow characteristics of the two-row plate-finned tube heat exchanger in staggered arrangement. The effect of air speed and fin spacing on the results obtained is investigated. Temperature and velocity distributions of air between the two fins and heat transfer coefficient on the fins are determined using the laminar flow and RNG k-ɛ turbulence models. More accurate results can be obtained, if the heat transfer coefficient obtained is close to the inverse results and matches existing correlations. Furthermore, the fin temperature measured at the selected locations also coincides with the experimental temperature data. The results obtained using the RNG k-ɛ turbulence model are more accurate than those using the laminar flow model. An interesting finding is the number of grid points may also need to change with fin spacing and air speed.

  16. Radiative heat conductances between dielectric and metallic parallel plates with nanoscale gaps

    Science.gov (United States)

    Song, Bai; Thompson, Dakotah; Fiorino, Anthony; Ganjeh, Yashar; Reddy, Pramod; Meyhofer, Edgar

    2016-06-01

    Recent experiments have demonstrated that radiative heat transfer between objects separated by nanometre-scale gaps considerably exceeds the predictions of far-field radiation theories. Exploiting this near-field enhancement is of great interest for emerging technologies such as near-field thermophotovoltaics and nano-lithography because of the expected increases in efficiency, power conversion or resolution in these applications. Past measurements, however, were performed using tip-plate or sphere-plate configurations and failed to realize the orders of magnitude increases in radiative heat currents predicted from near-field radiative heat transfer theory. Here, we report 100- to 1,000-fold enhancements (at room temperature) in the radiative conductance between parallel-planar surfaces at gap sizes below 100 nm, in agreement with the predictions of near-field theories. Our measurements were performed in vacuum gaps between prototypical materials (SiO2–SiO2, Au–Au, SiO2–Au and Au–Si) using two microdevices and a custom-built nanopositioning platform, which allows precise control over a broad range of gap sizes (from <100 nm to 10 μm). Our experimental set-up will enable systematic studies of a variety of near-field-based thermal phenomena, with important implications for thermophotovoltaic applications, that have been predicted but have defied experimental verification.

  17. Heat transfer and pressure drop of a gasket-sealed plate heat exchanger depending on operating conditions across hot and cold sides

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Joon [Kookmin University, Seoul (Korea, Republic of); Kim, Hyouck Ju [Korea Institute of Energy Research, Daejeon (Korea, Republic of)

    2016-05-15

    In a gas engine based cogeneration system, heat may be recovered from two parts: Jacket water and exhaust gas. The heat from the jacket water is often recovered using a plate-type heat exchanger, and is used for room heating and/or hot water supply applications. Depending on the operating conditions of an engine and heat recovery system, there may be an imbalance in the flow rate and supply pressure between the engine side and the heat-recovery side of the heat exchanger. This imbalance causes deformation of the plate, which affects heat transfer and pressure drop characteristics. In the present study, the heat transfer and pressure drop inside a heat exchanger were investigated under varying hot-side and cold-side operating conditions. Thermal efficiency of the plate heat exchanger decreases up to 30% with an operating engine load of 50%. A correction factor for the pressure drop correlation is proposed to account for the deformation caused by an imbalance between the two sides of a heat exchanger.

  18. Investigation of heat transfer and fluid flow in transitional regime inside a channel with staggered plates heated by radiation for PV/T system

    International Nuclear Information System (INIS)

    This study investigates experimentally and theoretically the effects of operating and configuration parameters on convection heat transfer process and fluid flow characteristics for air flowing in transitional regimes through parallel plate channels with staggered plates segments heated by radiant heat flux. This configuration is to be utilized in air heater solar collectors and/or in a combined photovoltaic and air heater solar collector systems (PV/T). The operating parameters tested were Reynolds number (Re) values ranging from 2580 to 4650 with a combination of incident radiation heat flux (qinc) values of 400, 700, and 1000 W/m2, respectively. The experimental results show that the local Nusselt number (Nux) is not unique function of the axial distance, in addition, a linear relationship between Re and apparent friction factor (f) was observed. Moreover, the model results show that combination of Re values in the laminar flow regime with proper selection of both plate's length and thickness can lead to enhancement in the heat transfer from the plate segments to the air stream. This is due to self-oscillatory flow mixer in wake zone behind each plate segment. Consequently, this will lead to avoid the need of more pumping power for the case of the flow falling within the transitional regime in the channel. - Highlights: • The local heat transfer coefficient is not unique function in the axial distance. • A linear relationship between Reynolds number and apparent friction factor is observed for Re > 3500. • The plate thickness is the dominant parameter affects both values of the heat transfer and friction factor. • Shorter plates' length, at any plate thickness, leads to periodic boundary layers interruption mechanisms

  19. Computational heat transfer analysis and combined ANN–GA optimization of hollow cylindrical pin fin on a vertical base plate

    Indian Academy of Sciences (India)

    C Balachandar; S Arunkumar; M Venkatesan

    2015-09-01

    In the devices like laptops, microprocessors, the electric circuits generate heat while performing work which necessitates the use of fins. In the present work, the heat transfer characteristics of hollow cylindrical pin fin array on a vertical rectangular base plate is studied using commercial CFD code ANSYS FLUENT© . The hollow cylindrical pin fins are arranged inline. The heat transfer augmentation is studied for different parameters such as inner radius, outer radius, height of the fins and number of pin fins. The base plate is supplied with a constant heat flux in the range of 20–500W. The base plate dimensions are kept constant. The base plate temperature is predicted using Artificial Neural Network (ANN) by training the network based on the results of numerical simulation. The trained ANN is used to analyse the fin in terms of enhanced heat transfer and weight reduction when compared to solid pin fin. Optimization of the hollow cylindrical pin fin parameters to obtain maximum heat transfer from the base plate is carried out using Genetic Algorithm (GA) applied on the trained neural network. The analysis using the numerical simulation and neural network shows that the hollow fins provide an increased heat transfer and a weight reduction of about 90% when compared to solid cylindrical pin fins.

  20. Real-time simulation of thermal stresses and creep in plates subjected to transient heat input

    DEFF Research Database (Denmark)

    Hattel, Jesper Henri; Jacobsen, Torben Krogsdal; Hansen, P.N.

    1997-01-01

    This paper presents a novel numerical technique for solving the temperature and stress fields in a plate subjected to arbitrarily varying transient boundary conditions (transient temperature and heat-flux variations) on a surface. The numerical method is based on the control-volume finite-difference......-two-dimensional. Both plane stress and plane strain conditions are considered as extreme cases. It is shown that, by using the developed numerical technique, very fast real-time simulations can be performed. The method has proved its applicability in e.g. high-pressure die-casting, and applications to this industrial...

  1. The influence of heat treatment by annealing on clad plates residual stresses

    Directory of Open Access Journals (Sweden)

    B. Mateša

    2011-10-01

    Full Text Available The influence of applied clad procedure as well as heat treatment by annealing (650 °C/2h on level and nature of residual stresses was researched. Three clad procedures are used i.e. hot rolling, submerged arc welding (SAW with strip electrode and explosion welding. The relaxed deformation measurement on clad plate surfaces was performed by applying centre-hole drilling method using special measuring electrical resistance strain gauges (rosettes. After performed measuring, size and nature of residual stresses were determined using analytical method. Depending of residual stresses on depth of drilled blind-hole is studied.

  2. Heat Transfer Characteristics of Dropwise Condensation of Steam on Vertical Polymer Coated Plates

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The plasma polymerization method and dynamic ion-beam mixed implantation method were employed to coat ultra-thin polymer films on copper plates. Experiments indicated that steady dropwise condensation of steam at atmospheric pressure occurred. The condensation heat transfer coefficients increased by approximately 3 and 5-7 times for the polytrimethylvinylsilane film and polytetrafluoroethylene film respectively, compared with the value for film condensation under the same experimental conditions. The temperatures on the condensing surface and inside the test block were found to be rapidly and randomly fluctuated. The properties of the coated films and advantages of the methods used in this investigation were discussed briefly.

  3. Magnetohydrodynamic Boundary Layer Slip Flow and Heat Transfer of Power Law Fluid over a Flat Plate

    Directory of Open Access Journals (Sweden)

    Jacob Hirschhorn

    2016-01-01

    Full Text Available In this paper, we consider the magnetohydrodynamic (MHD boundary layer flow and heat transfer of power law fluid over a flat plate with slip boundary conditions. We use a similarity transformation to convert the governing nonlinear partial differential equations into a system of ordinary differential equations and solve the resulting system numerically using MATLAB’s boundary value solver, bvp4c, and the shooting method. We present velocity and temperature profiles within the boundary layer and demonstrate the effect of changing the magnetic parameter, Prandtl number, and slip parameters.

  4. Solution of the two- dimensional heat equation for a rectangular plate

    Directory of Open Access Journals (Sweden)

    Nurcan BAYKUŞ SAVAŞANERİL

    2015-11-01

    Full Text Available Laplace equation is a fundamental equation of applied mathematics. Important phenomena in engineering and physics, such as steady-state temperature distribution, electrostatic potential and fluid flow, are modeled by means of this equation. The Laplace equation which satisfies boundary values is known as the Dirichlet problem. The solutions to the Dirichlet problem form one of the most celebrated topics in the area of applied mathematics. In this study, a novel method is presented for the solution of two-dimensional heat equation for a rectangular plate. In this alternative method, the solution function of the problem is based on the Green function, and therefore on elliptic functions.

  5. Natural convection of nanofluids over a convectively heated vertical plate embedded in a porous medium

    International Nuclear Information System (INIS)

    In this paper, the natural convective flow of nanofluids over a convectively heated vertical plate in a saturated Darcy porous medium is studied numerically. The governing equations are transformed into a set of ordinary differential equations by using appropriate similarity variables, and they are numerically solved using the fourth-order Runge-Kutta method associated with the Gauss-Newton method. The effects of parametric variation of the Brownian motion parameter (Nb), thermophoresis parameter (Nt) and the convective heating parameter (Nc) on the boundary layer profiles are investigated. Furthermore, the variation of the reduced Nusselt number and reduced Sherwood number, as important parameters of heat and mass transfer, as a function of the Brownian motion, thermophoresis and convective heating parameters is discussed in detail. The results show that the thickness of the concentration profiles is much lower than the temperature and velocity profiles. For low values of the convective heating parameter (Nc), as the Brownian motion parameter increases, the non-dimensional wall temperature increases. However, for high values of Nc, the effect of the Brownian motion parameter on the non-dimensional wall temperature is not significant. As the Brownian motion parameter increases, the reduced Sherwood number increases and the reduced Nusselt number decreases. (author)

  6. Natural convection of nanofluids over a convectively heated vertical plate embedded in a porous medium

    Energy Technology Data Exchange (ETDEWEB)

    Ghalambaz, M.; Noghrehabadi, A.; Ghanbarzadeh, A., E-mail: m.ghalambaz@gmail.com, E-mail: ghanbarzadeh.a@scu.ac.ir [Department of Mechanical Engineering, Shahid Chamran University of Ahvaz, Ahvaz (Iran, Islamic Republic of)

    2014-04-15

    In this paper, the natural convective flow of nanofluids over a convectively heated vertical plate in a saturated Darcy porous medium is studied numerically. The governing equations are transformed into a set of ordinary differential equations by using appropriate similarity variables, and they are numerically solved using the fourth-order Runge-Kutta method associated with the Gauss-Newton method. The effects of parametric variation of the Brownian motion parameter (Nb), thermophoresis parameter (Nt) and the convective heating parameter (Nc) on the boundary layer profiles are investigated. Furthermore, the variation of the reduced Nusselt number and reduced Sherwood number, as important parameters of heat and mass transfer, as a function of the Brownian motion, thermophoresis and convective heating parameters is discussed in detail. The results show that the thickness of the concentration profiles is much lower than the temperature and velocity profiles. For low values of the convective heating parameter (Nc), as the Brownian motion parameter increases, the non-dimensional wall temperature increases. However, for high values of Nc, the effect of the Brownian motion parameter on the non-dimensional wall temperature is not significant. As the Brownian motion parameter increases, the reduced Sherwood number increases and the reduced Nusselt number decreases. (author)

  7. Enhance heat transfer in the channel with V-shaped wavy lower plate using liquid nanofluids

    Directory of Open Access Journals (Sweden)

    Azher M. Abed

    2015-03-01

    Full Text Available The heat transfer and flow characteristics in corrugated with V-shape lower plate using nanofluids are numerically studied. The computations are performed on uniform heat flux over a range of Reynolds number (Re 8000–20,000. The governing equations are numerically solved in the domain by a finite volume method (FVM using the k–ε standard turbulent model. Studies are carried out for different types of nanoparticles Al2O3,CuO, SiO2 and ZnO with different volume fractions in the range of 0–4%. Three different types of base fluid (water, glycerin, ethylene glycol are also examined. Results indicated that the average Nusselt number for nanofluids is greater than that of the base liquid. The SiO2 nanofluid yields the best heat transfer enhancement among all other type of nanofluids. Heat transfer enhancement increase with increases the volumetric concentration, but it is accompanied by increasing pressure drop values. Moreover, the average Nusselt number increases with an increase in Reynolds number and volume concentration. The SiO2–glycerin nanofluid has the highest Nusselt number compared with other base fluids. The present study shows that these V-shaped wavy channels have advantages by using nanofluids and thus serve as promising candidates for incorporation into efficient heat transfer devices.

  8. Pre-qualification of brazed plasma facing components of divertor target elements for ITER like tokamak application

    Energy Technology Data Exchange (ETDEWEB)

    Singh, K.P., E-mail: kpsingh@ipr.res.in [Institute for Plasma Research, Bhat, Gandhinagar, Gujarat (India); Pandya, Santosh P.; Khirwadkar, S.S.; Patel, Alpesh; Patil, Y.; Buch, J.J.U.; Khan, M.S.; Tripathi, Sudhir; Pandya, Shwetang; Govindrajan, J. [Institute for Plasma Research, Bhat, Gandhinagar, Gujarat (India); Jaman, P.M.; Rathore, Devendra; Rangaraj, L.; Divakar, C. [Materials Science Division, National Aerospace Laboratories, CSIR, Bangalore, Karnataka (India)

    2011-10-15

    Qualification of tungsten (W) and graphite (C) based brazed plasma facing components (PFCs) is an important R and D area in fusion research. Pre-qualification tests for brazed joints between W-CuCrZr and C-CuCrZr using NDT (IR thermography and ultrasonic test) and thermal fatigue test are attempted. Mockups having good quality brazed joints of W and C based PFCs were identified using NDT. Subsequently, thermal fatigue test was performed on the identified mockups. All brazed tiles of W based PFC mockups could withstand thermal fatigue test, however, few tiles of C based PFC mockup were found detached. Thermal analyses of mockups are performed using finite element analysis (ANSYS) software to simulate the thermal hydraulic condition with 10 MW/m{sup 2} uniform heat flux. Details about experimental and computational work are presented here.

  9. Interfacial reaction product and mechanical properties of the electron beam brazed K465 Ni-based superalloy joints

    Institute of Scientific and Technical Information of China (English)

    Wang Gang; Zhang Binggang; He Jingshan; Feng Jicai; Wu Yingjie

    2008-01-01

    Ni-based superalloy K465 is brazed with BNi-2 filler metal by vacuum electron beam brazing (VEBB). In process of VEBB, effects of processing primary parameters on shear strength of joints are investigated. Microstructure of the brazed joint with BNi-2 filler metal is studied by means of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The results show that the structure of brazed seam consists of a large amount of Ni-based γ solid solution, Ni3Al (γ′), Ni3B, WB, CrB, and a small quantity of WC, NbC. The maximum shear strength of the joint is 398 MPa when the beam current of welding is 2.6 mA, heating time is 480 s and focused current is 1 800 mA.

  10. Experimental and numerical contribution to heat transfer enhancement in compact plate heat exchangers

    International Nuclear Information System (INIS)

    In the framework of CEA R and D program to develop an industrial prototype of Sodium cooled Fast Reactor, the present thesis aimed to propose an innovative compact heat exchanger technology. In order to increase the global compactness the basic idea of this work is to design a channel were the fluid flow is as much three-dimensional as possible. In particular the channel can be thought as the result of the superposition of two undulated channels in phase opposition. To numerically provide a physically-consistent model, a new non-linear eddy viscosity named Anisotropic Shear Stress Transport (ASST) model has been developed and implemented into the available solver ANSYS FLUENT. To validate the numerical model, two experimental sections have been used to acquire an extensive aerodynamic database, whereas, to validate the thermal modeling approach, the VHEGAS facility has been built. Once having validated the ASST model, correlations for friction factor and Nusselt number for various geometries could be obtained. Finally, it has been shown that the innovative channel is the most compact one among the most important existing industrial compact heat exchanger technologies. (author)

  11. The influence of distance between heat sources in hybrid welded plate on fusion zone geometry

    Directory of Open Access Journals (Sweden)

    W. Piekarska

    2011-04-01

    Full Text Available Results of numerical analysis into temperature field in hybrid laser-arc welding process with motion of liquid material taken intoaccount are presented in this study. On the basis of obtained results the influence of the distance between the arc foot point and the laserbeam focal point on the shape and size of fusion zone in hybrid butt welded plate. Temperature field was calculated on the basis ofsolution of transient heat transfer equation. The solution of Navier-Stokes equation allowed for simulation of fluid flow in the fusion zone.Fuzzy solidification front was assumed in calculations with linear approximation of solid fraction in solid-liquid region where liquidmaterial flow through porous medium is taken into consideration. Numerical solution algorithms were developed for three-dimensionalproblem. Established numerical model of hybrid welding process takes into account different electric arc and laser beam heat sourcespower distributions.

  12. Analytical and Numerical Solutions of Vapor Flow in a Flat Plate Heat Pipe

    Directory of Open Access Journals (Sweden)

    Mohsen GOODARZI

    2012-03-01

    Full Text Available In this paper, the optimal homotopy analysis method (OHAM and differential transform method (DTM were applied to solve the problem of 2D vapor flow in flat plate heat pipes. The governing partial differential equations for this problem were reduced to a non-linear ordinary differential equation, and then non-dimensional velocity profiles and axial pressure distributions along the entire length of the heat pipe were obtained using homotopy analysis, differential transform, and numerical fourth-order Runge-Kutta methods. The reliability of the two analytical methods was examined by comparing the analytical results with numerical ones. A brief discussion about the advantages of the two applied analytical methods relative to each other is presented. Furthermore, the effects of the Reynolds number and the ratio of condenser to evaporator lengths on the flow variables were discussed.Graphical abstract

  13. Design of plate directional heat transmission structure based on layered thermal metamaterials

    International Nuclear Information System (INIS)

    Invisibility cloaks based on transformation optics are often closed structures; however, such a structure limits the kinds of objects that can be placed in the cloak. In this work, we adopt a transformation thermodynamics approach to design an “open cloak”, called a plate directional heat transmission structure, which is capable of guiding heat fluxes to the flank region of the metamaterial device. The most fascinating and unique feature of the device is that the lower surface can remain at a lower temperature compared with the SiO2 aerogel thermal insulation material. Our results are expected to markedly enhance capabilities in thermal protection, thermal-energy utilization, and domains beyond. In addition to the theoretical analysis, the present design is demonstrated in numerical simulations based on finite element calculations

  14. Armor plate protection for the Doublet III vacuum vessel for neutral beam heating

    International Nuclear Information System (INIS)

    The design of vacuum vessel armor plate for neutral beam systems presents a number of challenges to the engineer. Heat fluxes of several hundred watts/cm2 must be handled on a routine basis during normal plasma operations, and a factor of ten increase in these fluxes can occur during plasma disruptions. At the present time, a graphite tile system appears to be the best candidate for such a situation. Heat fluxes in excess of 4 kW/cm2 can be routinely sustained and the material sputtered or evaporated from the surface has a low atomic number. The system proposed for Doublet III will provide valuable data for the designers of future fusion reactors and will also provide proof-of-principle demonstrations for such machines as TFTR and JET

  15. Design of plate directional heat transmission structure based on layered thermal metamaterials

    Energy Technology Data Exchange (ETDEWEB)

    Sun, L. K.; Yu, Z. F.; Huang, J., E-mail: slk-0-1999@163.com [China Aerodynamics Research and Development Center, Mianyang 621000 (China)

    2016-02-15

    Invisibility cloaks based on transformation optics are often closed structures; however, such a structure limits the kinds of objects that can be placed in the cloak. In this work, we adopt a transformation thermodynamics approach to design an “open cloak”, called a plate directional heat transmission structure, which is capable of guiding heat fluxes to the flank region of the metamaterial device. The most fascinating and unique feature of the device is that the lower surface can remain at a lower temperature compared with the SiO{sub 2} aerogel thermal insulation material. Our results are expected to markedly enhance capabilities in thermal protection, thermal-energy utilization, and domains beyond. In addition to the theoretical analysis, the present design is demonstrated in numerical simulations based on finite element calculations.

  16. Design of plate directional heat transmission structure based on layered thermal metamaterials

    Directory of Open Access Journals (Sweden)

    L. K. Sun

    2016-02-01

    Full Text Available Invisibility cloaks based on transformation optics are often closed structures; however, such a structure limits the kinds of objects that can be placed in the cloak. In this work, we adopt a transformation thermodynamics approach to design an “open cloak”, called a plate directional heat transmission structure, which is capable of guiding heat fluxes to the flank region of the metamaterial device. The most fascinating and unique feature of the device is that the lower surface can remain at a lower temperature compared with the SiO2 aerogel thermal insulation material. Our results are expected to markedly enhance capabilities in thermal protection, thermal-energy utilization, and domains beyond. In addition to the theoretical analysis, the present design is demonstrated in numerical simulations based on finite element calculations.

  17. DRY/WET PERFORMANCE OF A PLATE-FIN AIR COOLED HEAT EXCHANGER WITH CONTINUOUS CORRUGATED FINS

    Science.gov (United States)

    The report describes work to (1) determine experimentally the performance and operating characteristics of a plate-fin heat exchanger during dry/wet or 'deluge' operation and (2) continue developing the deluge heat/mass transfer model. This work supports the improvement of power ...

  18. Thermal-Hydraulic Analysis of Heated Plate under Asymmetrical Cooling Conditions

    International Nuclear Information System (INIS)

    The cooling of a vertical heated plate by two thin channels is encountered in different applications such as MTR research reactors. The analytical solution of the governing equation of such case is usually used provided that symmetrical of the cooling channels is assumed. Under asymmetrical cooling conditions the analytical solution is impossible and the numerical solution becomes the only way. This problem is our case study in which the finite difference method is used to convert the steady state governing equation into a number of algebraic equations which are solved by Gauss Jordan’s method. The coolant flow distribution through the channels is determined based on an equal overall pressure drop in the two channels. The axial power distribution through the plate is considered cosine shape. Therefore, a simple one-dimensional steady state computer FORTRAN program named NSCHP is built to deal with the asymmetrical cooling conditions encountered in MTR research reactors resulting from fuel manufacturing uncertainties. This program has the capability to calculate the axial and radial temperature distribution in the plate, the coolant axial temperature, the flow distribution, the coolant velocity, and the channel pressure drop. The introduced program is verified by comparing its results with the RELAP5 mode 3.3 where a good agreement was found. With respect to the channel blockage or manufacturing uncertainties, the results show that an inadvertent decrease in channel cross section up to 82.5% of the nominal channel do not violate the approved maximum cladding temperature.

  19. Temperature, lithosphere-asthenosphere boundary, and heat flux beneath the Antarctic Plate inferred from seismic velocities

    Science.gov (United States)

    An, Meijian; Wiens, Douglas A.; Zhao, Yue; Feng, Mei; Nyblade, Andrew; Kanao, Masaki; Li, Yuansheng; Maggi, Alessia; Lévêque, Jean-Jacques

    2015-12-01

    We estimate the upper mantle temperature of the Antarctic Plate based on the thermoelastic properties of mantle minerals and S velocities using a new 3-D shear velocity model, AN1-S. Crustal temperatures and surface heat fluxes are then calculated from the upper mantle temperature assuming steady state thermal conduction. The temperature at the top of the asthenosphere beneath the oceanic region and West Antarctica is higher than the dry mantle solidus, indicating the presence of melt. From the temperature values, we generate depth maps of the lithosphere-asthenosphere boundary and the Curie temperature isotherm. The maps show that East Antarctica has a thick lithosphere similar to that of other stable cratons, with the thickest lithosphere (~250 km) between Domes A and C. The thin crust and lithosphere beneath West Antarctica are similar to those of modern subduction-related rift systems in East Asia. A cold region beneath the Antarctic Peninsula is similar in spatial extent to that of a flat-subducted slab beneath the southern Andes, indicating a possible remnant of the Phoenix Plate, which was subducted prior to 10 Ma. The oceanic lithosphere generally thickens with increasing age, and the age-thickness correlation depends on the spreading rate of the ridge that formed the lithosphere. Significant flattening of the age-thickness curves is not observed for the mature oceanic lithosphere of the Antarctic Plate.

  20. Effects of Different Braze Materials and Composite Substrates on Composite/Ti Joints

    Science.gov (United States)

    Morscher, Gregory N.; Singh, Mrityunjay; Asthana, Rajiv; Shpargel, Tarah

    2007-01-01

    An ever increasing number of applications require robust joining technologies of dissimilar materials. In this study, three types of ceramic composites (C-C, C-SiC, and SiC-SiC) were vacuum brazed to commercially pure Ti using the Cusil-ABA (63 Ag - 35.5 Cu - 1.75 Ti) active metal braze alloy. The study also compared composite specimens as-fabricated and after surface grinding/polishing. A butt-strap tensile shear strength test was used to evaluate the joined structures at room temperature, 270 and 500 C. The elevated temperatures represent possible use temperatures for some heat rejection type applications. Joint strength will be discussed in light of braze wetting and spreading properties, composite properties, and test temperature.

  1. Nondestructive test of brazed cooling tubes of prototype bolometer camera housing using active infrared thermography.

    Science.gov (United States)

    Tahiliani, Kumudni; Pandya, Santosh P; Pandya, Shwetang; Jha, Ratneshwar; Govindarajan, J

    2011-01-01

    The active infrared thermography technique is used for assessing the brazing quality of an actively cooled bolometer camera housing developed for steady state superconducting tokamak. The housing is a circular pipe, which has circular tubes vacuum brazed on the periphery. A unique method was adopted to monitor the temperature distribution on the internal surface of the pipe. A stainless steel mirror was placed inside the pipe and the reflected IR radiations were viewed using an IR camera. The heat stimulus was given by passing hot water through the tubes and the temperature distribution was monitored during the transient phase. The thermographs showed a significant nonuniformity in the brazing with a contact area of around 51%. The thermography results were compared with the x-ray radiographs and a good match between the two was observed. Benefits of thermography over x-ray radiography testing are emphasized. PMID:21280850

  2. Experimental Study on Heat Transfer and Pressure Drop Characteristics of Four Types of Plate Fin-and-Tube Heat Exchanger Surfaces

    Institute of Scientific and Technical Information of China (English)

    1994-01-01

    In this paper,air side heat transfer and pressure drop characteristics of twelve three-row plate fin-and-tube heat exchanger cores of four types of fin configurations have been experimentally investigated .The heat transfer and friction factor correlations for the twelve cores are provided in a wide range of Reynolds number.It is found that in the range of Reynolds number tested.the Nusselt number of the slotted fin surface is the largest and that of the plain plate fin is the lowest while the Nusselt numbers of two types of wavy fins are somewhere in between.

  3. Forced convection on a heated horizontal flat plate with finite thermal conductivity in a non-Darcian porous medium

    Energy Technology Data Exchange (ETDEWEB)

    Luna, N. [Direccion de Operacion Petrolera, Direccion General de Exploracion y Explotacion de Hidrocarburos, Secretaria de Energia, 03100 Mexico DF (Mexico); Mendez, F. [Facultad de Ingenieria, UNAM, 04510 Mexico DF (Mexico)

    2005-07-01

    The steady-state analysis of conjugated heat transfer process for the hydrodynamically developed forced convection flow on a heated flat plate embedded in a porous medium is studied. The governing equations for the fluid-saturated porous medium are solved analytically using the integral boundary layer approximation. This integral solution is coupled to the energy equation for the flat plate, where the longitudinal heat conduction effects are taken into account. The resulting equations are then reduced to an integro-differential equation which is solved by regular perturbation techniques and numerical methods. The analytical and numerical predictions for the temperature profile of the plate and appropriate local and average Nusselt numbers are plotted for finite values of the conduction parameter, {alpha}, which represents the presence of the longitudinal heat conduction effects. (authors)

  4. Influence of brazing parameters and alloy composition on interface morphology of brazed diamond

    International Nuclear Information System (INIS)

    Active brazing is an effective technique for joining diamond or cBN grit to metallic substrates. This technique is currently used to manufacture superabrasive, high-performance tools. The investigation of interface reactions between diamond and active brazing alloys plays an important role in understanding and improving the brazing process and the resultant tool performance. Focused ion beam (FIB) milling enabled the high resolution investigation of these extremely difficult to prepare metal-diamond joints. The interfacial nanostructure is characterized by the formation of two layers of TiC with different morphologies. First a cuboidal layer forms directly on the diamond and reaches a thickness of approximately 70 nm. Then a second layer with columnar TiC crystals grows on the first layer into the brazing filler metal by a diffusion-controlled process. The combined thickness of both TiC layers varies between 50 nm and 600 nm depending on the brazing temperature and holding time

  5. A risk based performance evaluation of plate-and-frame heat exchangers

    Science.gov (United States)

    Rehman Khan, Jameel Ur; Zubair, Syed

    2002-11-01

    Plate-and-frame heat exchangers (PHEs) operating in process industries are fouled to a greater or lesser extent depending on surface temperature, surface condition, material of construction, fluid velocity, flow geometry and fluid composition. This fouling phenomenon is time-dependent and will result in a decrease in the overall heat transfer coefficient and increase in the pressure drop of the PHE. Once the overall heat transfer coefficient decreases to a minimum acceptable level, cleaning of the equipment becomes necessary to restore the performance. In this paper, we present a simple probabilistic approach to characterize various fouling models that are commonly encountered in many industries. These random fouling growth models are then used to investigate the impact on risk based thermal effectiveness, overall heat transfer coefficient and the hot- and cold-fluid outlet temperatures of a PHE. All the results are presented in a generalized form in order to demonstrate the generality of the risk-based procedure discussed in this paper.

  6. Turbulent Heat Transfer of a Finned Plate in a Duct as Tip Clearance Changes

    International Nuclear Information System (INIS)

    Fins are employed to enhance the cooling performance of a system. There are a number of studies relevant to geometry of fins. Meanwhile, the studies relevant to tip clearance, have not performed enough, which is the distance between the tips of the fins and the wall. We investigated the optimal tip clearance, which maximizes the heat transfers by experimental and numerical analyses with wider range of ReDh than the previous studies. Turbulent heat transfers of a finned plate were measured. For an extended range of tip clearance and ReDh than other studies. A joint experimental and numerical analyses was performed to measure heat transfers. Mass transfer experiments using electroplating system was used and FLUENT 6.3.26 was used for the calculation. For the narrow tip clearances below 5 mm, were investigated by numerical method only. The bypass flow to the tip clearance region contributes to heat transfer area at the tip clearance region and does not contributes that of the fin region. Thus, the optimal tip clearance was founded and it exists vicinity of 0.2 mm

  7. Turbulent Heat Transfer of a Finned Plate in a Duct as Tip Clearance Changes

    Energy Technology Data Exchange (ETDEWEB)

    Park, Hae-Kyun; Chung, Bum-Jin [Kyung Hee University, Yongin (Korea, Republic of)

    2015-05-15

    Fins are employed to enhance the cooling performance of a system. There are a number of studies relevant to geometry of fins. Meanwhile, the studies relevant to tip clearance, have not performed enough, which is the distance between the tips of the fins and the wall. We investigated the optimal tip clearance, which maximizes the heat transfers by experimental and numerical analyses with wider range of Re{sub Dh} than the previous studies. Turbulent heat transfers of a finned plate were measured. For an extended range of tip clearance and Re{sub Dh} than other studies. A joint experimental and numerical analyses was performed to measure heat transfers. Mass transfer experiments using electroplating system was used and FLUENT 6.3.26 was used for the calculation. For the narrow tip clearances below 5 mm, were investigated by numerical method only. The bypass flow to the tip clearance region contributes to heat transfer area at the tip clearance region and does not contributes that of the fin region. Thus, the optimal tip clearance was founded and it exists vicinity of 0.2 mm.

  8. High-Power Laser Cutting of Steel Plates: Heat Affected Zone Analysis

    Directory of Open Access Journals (Sweden)

    Imed Miraoui

    2016-01-01

    Full Text Available The thermal effect of CO2 high-power laser cutting on cut surface of steel plates is investigated. The effect of the input laser cutting parameters on the melted zone depth (MZ, the heat affected zone depth (HAZ, and the microhardness beneath the cut surface is analyzed. A mathematical model is developed to relate the output process parameters to the input laser cutting parameters. Three input process parameters such as laser beam diameter, cutting speed, and laser power are investigated. Mathematical models for the melted zone and the heat affected zone depth are developed by using design of experiment approach (DOE. The results indicate that the input laser cutting parameters have major effect on melted zone, heat affected zone, and microhardness beneath cut surface. The MZ depth, the HAZ depth, and the microhardness beneath cut surface increase as laser power increases, but they decrease with increasing cutting speed. Laser beam diameter has a negligible effect on HAZ depth but it has a remarkable effect on MZ depth and HAZ microhardness. The melted zone depth and the heat affected zone depth can be reduced by increasing laser cutting speed and decreasing laser power and laser beam diameter.

  9. Investigating the effect of non-similar fins in thermoeconomic optimization of plate fin heat exchanger

    International Nuclear Information System (INIS)

    Thermoeconomic optimization of plate fin heat exchanger with similar (SF) and different (DF) or non-similar fin in each side is presented in this work. For this purpose, both heat exchanger effectiveness and total annual cost (TAC) are optimized simultaneously using multi-objective particle swarm optimization algorithm. The above procedure is performed for various mass flow rates in each side. The optimum results reveal that no thermoeconomic improvement is observed in the case of same mass flow rate in each side while both effectiveness and TAC are improved in the case of different mass flow rate. For example, effectiveness and TAC are improved 0.95% and 10.17% respectively, for the DF compared with SF. In fact, the fin configuration should be selected more compact in a side with lower mass flow rate compared with the other side in the thermoeconomic viewpoint. Furthermore, for the thermodynamic optimization viewpoint both SF and DF have the same optimum result while for the economic (or thermoeconomic) optimization viewpoint, the significant decrease in TAC is accessible in the case of DF compared with SF. - Highlights: • Thermoeconomic modeling of compact heat exchanger. • Selection of fin and heat exchanger geometries as nine decision variables. • Applying MOPSO algorithm for multi objective optimization. • Considering the similar and different fin specification in each side. • Investigation of optimum design parameters for various mass flow rates

  10. Forced Convective Heat Transfer in a Plate Channel Filled with Solid Particles

    Institute of Scientific and Technical Information of China (English)

    Pei-XueJiang; Ze-PeiRen; 等

    1996-01-01

    A numerical study of fluid flow and convective heat transfer in a plate channel filled with solid(metallic)perticles is presented in this paper,The study uses the thermal equilibrium model and a newly developed numerical model which does not assume idealized local thermal equilibrium between the solid particles and the fluid.The numerical simulation results are compared with the experimental data in reference[2].The paper investigates the effects of the assumption of local thermal equilibrium versus non-thermal equilibrium,the thermal conductivity of the solid particles and the particle diameter on convective heat transfer.For the conditions studied.the convective heat transfer and the temperature filed assuming local thermal equilibrium are much different from that for the non-thermal equilibrium assumption when the difference between the solid and fluid thermal conductivities is large,The relative values of the thermal conductivities of the solid particles and the fluid also have a profound effect on the temperature distribution in the channel.The pressure drop decreases as the particle diameter increases and the convective heat transfer coefficient may decrease of increase as the particle diameter increasws depending on the values of ε,λs,λf,λd,αu,ρu.

  11. Fabrication of a tantalum neutral source heat exchanger

    International Nuclear Information System (INIS)

    The fabrication and testing of the Neutral Source Heat Exchanger (NSHE), a device required for a plutonium isotope separation pilot plant are described. The unit is a circular water-cooled tantalum plate which will have plutonium cast onto it. After the plutonium is cast and machined to final shape, the assembly will serve as a sputtering substrate for the separation process. The cooling water flow path is unique (adjacent logarithmic spirals terminating 180 degress apart) and created several fabrication and testing challenges. A photograph of the lower plate, showing the water channel geometry and brazing filler material, is shown

  12. Design of a braze alloy for fast epitaxial brazing of superalloys

    Science.gov (United States)

    Piegert, S.; Laux, B.; Rösier, J.

    2012-07-01

    For the repair of directionally solidified turbine components made of nickel-based superalloys, a new high-temperature brazing method has been developed. Utilising heterogeneous nucleation on the crack surface, the microstructure of the base material can be reproduced, i.e. single crystallinity can be maintained. In contrast to commonly used eutectic braze alloys, such as nickel-boron or nickel-silicon systems, the process is not diffusion controlled but works with a consolute binary base system. The currently applied epitaxial brazing methods rely on isothermal solidification diffusing the melting point depressants into the base material until their concentration is reduced so that the liquid braze solidifies. Contrary, the identified Ni-Mn consolute system enables a temperature driven epitaxial solidification resulting in substantially reduced process duration. The development of the braze alloys was assisted using the CALPHAD software Thermo-Calc. The solidification behaviour was estimated by kinetic calculations with realistic boundary conditions. Finally, the complete system, including braze alloy as well as substrate material, was modelled by means of DICTRA. Subsequently, the thermodynamic properties of the braze alloys were experimentally analysed by DSC measurements. For brazing experiments 300 μm wide parallel gaps were used. Complete epitaxial solidification, i.e. the absence of high-angle grain boundaries, could be achieved within brazing times being up to two orders of magnitude shorter compared to diffusion brazing processes. Theoretically and experimentally evaluated process windows reveal similar shapes. However, a distinct shift has to be stated which can be ascribed to the limited accuracy of the underlying thermodynamic databases.

  13. Design of a braze alloy for fast epitaxial brazing of superalloys

    International Nuclear Information System (INIS)

    For the repair of directionally solidified turbine components made of nickel-based superalloys, a new high-temperature brazing method has been developed. Utilising heterogeneous nucleation on the crack surface, the microstructure of the base material can be reproduced, i.e. single crystallinity can be maintained. In contrast to commonly used eutectic braze alloys, such as nickel-boron or nickel-silicon systems, the process is not diffusion controlled but works with a consolute binary base system. The currently applied epitaxial brazing methods rely on isothermal solidification diffusing the melting point depressants into the base material until their concentration is reduced so that the liquid braze solidifies. Contrary, the identified Ni-Mn consolute system enables a temperature driven epitaxial solidification resulting in substantially reduced process duration. The development of the braze alloys was assisted using the CALPHAD software Thermo-Calc. The solidification behaviour was estimated by kinetic calculations with realistic boundary conditions. Finally, the complete system, including braze alloy as well as substrate material, was modelled by means of DICTRA. Subsequently, the thermodynamic properties of the braze alloys were experimentally analysed by DSC measurements. For brazing experiments 300 μm wide parallel gaps were used. Complete epitaxial solidification, i.e. the absence of high-angle grain boundaries, could be achieved within brazing times being up to two orders of magnitude shorter compared to diffusion brazing processes. Theoretically and experimentally evaluated process windows reveal similar shapes. However, a distinct shift has to be stated which can be ascribed to the limited accuracy of the underlying thermodynamic databases.

  14. A Magneto-convection Over a Semi -infinite Porous Plate with Heat Generation

    Directory of Open Access Journals (Sweden)

    T. Raja

    2013-01-01

    Full Text Available Convective flow through porous media is a branch of research undergoing rapid growth in fluid mechanics and heat transfer. This is quite natural because of its important applications in environmental, geophysical and energy related engineering problems. Prominent applications are the utilization of geothermal energy, the control of pollutant spread in ground water, the design of nuclear reactors, solar power collectors and the heat transfer associated with the deep storage of nuclear waste. The study of heat generation in moving fluids is important in problems dealing with chemical reactions and those concerned with dissociating fluids. Heat generation effects may alter the temperature distribution and this in turn can affect the particle deposition rate in nuclear reactors, electronic chips and semi conductor wafers. Although exact modeling of internal heat generation is quite difficult, some simple mathematical models can be used to express its general behaviour for most physical situations. The objective of this work is to investigate the effects of internal heat generation on an unsteady two-dimensional magnetohydrodynamic free convection flow of a viscous, incompressible fluid free convection flow past a semi-infinite vertical porous plate embedded in a porous medium, in the presence of variable suction. The equations of continuity, linear momentum and energy, which govern the flow field, are transformed to a system of ordinary differential equations by perturbation technique. The resulting equations are solved analytically to obtain the solutions for the velocity and temperature fields. The behavior of the velocity, temperature, skin-friction and Nusselt number have been discussed for variations in the physical parameters.

  15. Inline Array Jet Impingement Cooling Using Al2O3 / Water Nanofluid In A Plate Finned Electronic Heat Sink

    Directory of Open Access Journals (Sweden)

    R. Reji Kumar

    2016-07-01

    Full Text Available - Jet impingement cooling is a technique used for cooling the electronic systems. In this work, heat transfer and pressure drop characteristics of deionized water and Al2O3/water nanofluid in an electronic heat sink having aluminium plate fins and provision for jet impingement cooling have been studied. A novel heat sink contains two rows of plate fins of size 29mm x 24mm x 0.56mm. A thin plate having 110 holes of diameter 2.5 mm is used to produce number of jets. The plate is kept inside the heat sink in such a way that H/dn is 5.2 mm and adjacent jet spacing is 2mm. The overall dimension of the heat sink is 60x60x 65 mm. For this work we prepared a Al2O3/water nanofluid by dispersing specified quantity of nanoparticles in to deionized water by using a ultrasonic bath. Experiments were conducted under constant heat flux condition and the volume flow rate of the fluid was in the range of 1.315 to 2.778. It is found from the results that the nanofluid removes heat better than water in the jet impingement cooling with very low rise in pressure drop.

  16. Scanning Kelvin probe force microscopy as a means of predicting the electrochemical characteristics of the surface of a modified AA4xxx/AA3xxx (Al alloys) brazing sheet

    International Nuclear Information System (INIS)

    Highlights: ► Macro- and micro-electrochemical surface properties of an aluminium brazing sheet were investigated. ► Electrochemical surface properties before and after brazing were studied and compared. ► Scanning Kelvin probe force microscopy and potentiodynamic polarization measurements were performed. ► The electrochemical responses were correlated to the pre- and post-brazing treatment microstructure. -- Abstract: Macro- and micro-electrochemical properties of clad and core surfaces of a modified AA4xxx/AA3xxx brazing sheet material, before and after brazing, have been evaluated and compared. By scanning Kelvin probe force microscopy (SKPFM), the Volta potential distribution over the brazed and non-brazed clad surfaces was measured. The changes in the Volta potential maps were correlated to the macro-electrochemical responses of the surfaces and the microstructural features that evolve as a result of brazing. By performing potentiodynamic polarization experiments and microscopic analysis of the corroded surfaces and cross sections, the suitability of SKPFM analysis for corrosion performance prediction of the aluminium brazing sheet material in a sea water acidified accelerated test (SWAAT) environment was confirmed. Considering the purity of Si phase in the structures of both brazed and non-brazed material, it is suggested that Si can be applied as a reliable local reference in both structures to compare the changes in Volta potential differences as the result of different heat treatments of aluminium brazing sheet. Increasing the copper content of the re-solidified clad material as a result of brazing treatment was found to increase the Volta potential of the matrix which in turn reduces the cathodic protection power of the re-solidified clad material towards the core material

  17. Magnetohydrodynamic Free Convention Flow of a Heat Generating Fluid past a Semi-Infinite Vertical Porous Plate with Variable Suction

    Directory of Open Access Journals (Sweden)

    Nicholas Mutua

    2013-06-01

    Full Text Available In this paper, a magnetohydrodynamic convection flow of an electrically conducting heat generating fluid past a semi-infinite vertical porous plate with variable suction is considered. The fluid flow is unsteady and a variable magnetic field is transversely applied to the plate. Evaluation of velocity gradients, temperature gradients and concentration gradients across the plate is done. Observations and discussions of the effects of various parameters on flow variables are done. The non-dimensional parameters observed and discussed are Hall parameter, M; Magnetic number, M2; Eckert number, Ec; Rotational parameter, Er; Suction parameter, S and Injection parameter, w. The velocity profiles, temperature profiles and concentration profiles are presented graphically for both convectional heating and free convectional cooling of the plate. The skin friction and rate of heat transfer values are obtained and presented in tables. For free convectional heating and cooling of the plate, the Grashof number is taken as constants -5 and 5 respectively. Prandtl number is 0.71 which corresponds to air. The variation of the parameters mentioned above is noted to increase or decrease or had no effect on the skin friction, mass transfer, rate of heat transfer, the velocity profiles, concentration profiles and temperature profiles. 

  18. Current practices for ultrasonic and radiographic examination of tubes, tube plates and tube-plate welds of tube bundles in heat exchangers. Chapter 3

    International Nuclear Information System (INIS)

    The chapter describes the ultrasonic and radiographic inspection procedures that are applied to heat exchanger tube bundles. The inspection process starts with the ultrasonic examination of the tubes and tube plates during manufacture, followed by radiography of the tube-to-tube-plate welds during fabrication of the tube bundle. Ultrasonic methods are explained for welds which are amenable to this type of inspection. For the in-service inspection of tube bundles the chapter relates the authors' experiences on the ultrasonic inspection of tubes and tube plates in the Prototype Fast Breeder Reactor at Dounreay. At the end of the chapter some comments are made about future ultrasonic and radiographic developments for tube bundles. (author)

  19. Modeling the dynamic operation of a small fin plate heat exchanger – parametric analysis

    Directory of Open Access Journals (Sweden)

    Motyliński Konrad

    2015-09-01

    Full Text Available Given its high efficiency, low emissions and multiple fuelling options, the solid oxide fuel cells (SOFC offer a promising alternative for stationary power generators, especially while engaged in micro-combined heat and power (μ-CHP units. Despite the fact that the fuel cells are a key component in such power systems, other auxiliaries of the system can play a critical role and therefore require a significant attention. Since SOFC uses a ceramic material as an electrolyte, the high operating temperature (typically of the order of 700–900 °C is required to achieve sufficient performance. For that reason both the fuel and the oxidant have to be preheated before entering the SOFC stack. Hot gases exiting the fuel cell stack transport substantial amount of energy which has to be partly recovered for preheating streams entering the stack and for heating purposes. Effective thermal integration of the μ-CHP can be achieved only when proper technical measures are used. The ability of efficiently preheating the streams of oxidant and fuel relies on heat exchangers which are present in all possible configurations of power system with solid oxide fuel cells. In this work a compact, fin plate heat exchanger operating in the high temperature regime was under consideration. Dynamic model was proposed for investigation of its performance under the transitional states of the fuel cell system. Heat exchanger was simulated using commercial modeling software. The model includes key geometrical and functional parameters. The working conditions of the power unit with SOFC vary due to the several factors, such as load changes, heating and cooling procedures of the stack and others. These issues affect parameters of the incoming streams to the heat exchanger. The mathematical model of the heat exchanger is based on a set of equations which are simultaneously solved in the iterative process. It enables to define conditions in the outlets of both the hot and the

  20. Modeling the dynamic operation of a small fin plate heat exchanger - parametric analysis

    Science.gov (United States)

    Motyliński, Konrad; Kupecki, Jakub

    2015-09-01

    Given its high efficiency, low emissions and multiple fuelling options, the solid oxide fuel cells (SOFC) offer a promising alternative for stationary power generators, especially while engaged in micro-combined heat and power (μ-CHP) units. Despite the fact that the fuel cells are a key component in such power systems, other auxiliaries of the system can play a critical role and therefore require a significant attention. Since SOFC uses a ceramic material as an electrolyte, the high operating temperature (typically of the order of 700-900 °C) is required to achieve sufficient performance. For that reason both the fuel and the oxidant have to be preheated before entering the SOFC stack. Hot gases exiting the fuel cell stack transport substantial amount of energy which has to be partly recovered for preheating streams entering the stack and for heating purposes. Effective thermal integration of the μ-CHP can be achieved only when proper technical measures are used. The ability of efficiently preheating the streams of oxidant and fuel relies on heat exchangers which are present in all possible configurations of power system with solid oxide fuel cells. In this work a compact, fin plate heat exchanger operating in the high temperature regime was under consideration. Dynamic model was proposed for investigation of its performance under the transitional states of the fuel cell system. Heat exchanger was simulated using commercial modeling software. The model includes key geometrical and functional parameters. The working conditions of the power unit with SOFC vary due to the several factors, such as load changes, heating and cooling procedures of the stack and others. These issues affect parameters of the incoming streams to the heat exchanger. The mathematical model of the heat exchanger is based on a set of equations which are simultaneously solved in the iterative process. It enables to define conditions in the outlets of both the hot and the cold sides

  1. Free Convective Fluctuating MHD Flow through Porous Media Past a Vertical Porous Plate with Variable Temperature and Heat Source

    Directory of Open Access Journals (Sweden)

    A. K. Acharya

    2014-01-01

    Full Text Available Free convective magnetohydrodynamics (MHD flow of a viscous incompressible and electrically conducting fluid past a hot vertical porous plate embedded in a porous medium in the presence of heat source has been studied in this paper. The temperature of the plate varies both in space and time. The main objective of this paper is to study the effect of porosity of the medium coupled with the variation of plate temperature with regard to space and in time. The effect of pertinent parameters characterizing the flow has been presented through the graphs. It is important to record that the presence of porous media has no significant contribution to the flow characteristics and viscous dissipation compensates for the heating and cooling of the plate due to convective current.

  2. Numerical model of a thermoelectric generator with compact plate-fin heat exchanger for high temperature PEM fuel cell exhaust heat recovery

    DEFF Research Database (Denmark)

    Xin, Gao; Andreasen, Søren Juhl; Chen, Min;

    2012-01-01

    plate-fin heat exchangers is adopted. Then the model is validated against experimental data and the main variables are identified by means of a sensitivity analysis. Finally, the system configuration is optimized for recovering heat from the exhaust gas. The results exhibit the crucial importance of the......This paper presents a numerical model of an exhaust heat recovery system for a high temperature polymer electrolyte membrane fuel cell (HTPEMFC) stack. The system is designed as thermoelectric generators (TEGs) sandwiched in the walls of a compact plate-fin heat exchanger. Its model is based on a...... model accuracy and the optimization on system configuration. Future studies will concentrate on heat exchanger structures....

  3. Numerical Study Of The Heat Transfer Phenomenon Of A Rectangular Plate Including Void, Notch Using Finite Difference Technique

    Science.gov (United States)

    Deb Nath, S. K.; Peyada, N. K.

    2015-12-01

    In the present study, we have developed a code using Matlab software for solving a rectangular aluminum plate having void, notch, at different boundary conditions discretizing a two dimensional (2D) heat conduction equation by the finite difference technique. We have solved a 2D mixed boundary heat conduction problem analytically using Fourier integrals (Deb Nath et al., 2006; 2007; 2007; Deb Nath and Ahmed, 2008; Deb Nath, 2008; Deb Nath and Afsar, 2009; Deb Nath and Ahmed, 2009; 2009; Deb Nath et al., 2010; Deb Nath, 2013) and the same problem is also solved using the present code developed by the finite difference technique (Ahmed et al., 2005; Deb Nath, 2002; Deb Nath et al., 2008; Ahmed and Deb Nath, 2009; Deb Nath et al., 2011; Mohiuddin et al., 2012). To verify the soundness of the present heat conduction code results using the finite difference method, the distribution of temperature at some sections of a 2D heated plate obtained by the analytical method is compared with those of the plate obtained by the present finite difference method. Interpolation technique is used as an example when the boundary of the plate does not pass through the discretized grid points of the plate. Sometimes hot and cold fluids are passed through rectangular channels in industries and many types of technical equipment. The distribution of temperature of plates including notches, slots with different temperature boundary conditions are studied. Transient heat transfer in several pure metallic plates is also studied to find out the required time to reach equilibrium temperature. So, this study will help find design parameters of such structures.

  4. Numerical Study Of The Heat Transfer Phenomenon Of A Rectangular Plate Including Void, Notch Using Finite Difference Technique

    Directory of Open Access Journals (Sweden)

    Deb Nath S.K.

    2015-12-01

    Full Text Available In the present study, we have developed a code using Matlab software for solving a rectangular aluminum plate having void, notch, at different boundary conditions discretizing a two dimensional (2D heat conduction equation by the finite difference technique. We have solved a 2D mixed boundary heat conduction problem analytically using Fourier integrals (Deb Nath et al., 2006; 2007; 2007; Deb Nath and Ahmed, 2008; Deb Nath, 2008; Deb Nath and Afsar, 2009; Deb Nath and Ahmed, 2009; 2009; Deb Nath et al., 2010; Deb Nath, 2013 and the same problem is also solved using the present code developed by the finite difference technique (Ahmed et al., 2005; Deb Nath, 2002; Deb Nath et al., 2008; Ahmed and Deb Nath, 2009; Deb Nath et al., 2011; Mohiuddin et al., 2012. To verify the soundness of the present heat conduction code results using the finite difference method, the distribution of temperature at some sections of a 2D heated plate obtained by the analytical method is compared with those of the plate obtained by the present finite difference method. Interpolation technique is used as an example when the boundary of the plate does not pass through the discretized grid points of the plate. Sometimes hot and cold fluids are passed through rectangular channels in industries and many types of technical equipment. The distribution of temperature of plates including notches, slots with different temperature boundary conditions are studied. Transient heat transfer in several pure metallic plates is also studied to find out the required time to reach equilibrium temperature. So, this study will help find design parameters of such structures.

  5. Vacuum brazing of TiAl48Cr2Nb2 casting alloys based on TiAl (γ intermetallic compound

    Directory of Open Access Journals (Sweden)

    Z. Mirski

    2010-01-01

    Full Text Available A growing interest in modern engineering materials characterised by increasingly better operational parameters combined with a necessity to obtain joints of such materials representing good operation properties create important research and technological problems of today. These issues include also titanium joints or joints of titanium alloys based on intermetallic compounds. Brazing is one of the basic and sometimes even the only available welding method used for joining the aforesaid materials in production of various systems, heat exchangers and, in case of titanium alloys based on intermetallic compounds, turbine elements and space shuttle plating etc. This article presents the basic physical and chemical properties as well as the brazability of alloys based on intermetallic compounds. The work also describes the principle and mechanisms of diffusion-brazed joint formation as well as reveals the results of metallographic and strength tests involving diffusion-welded joints of TiAl48Cr3Nb2 casting alloy based on TiAl (γ phase with the use of sandwich-type layers of silver-based parent metal (grade B- Ag72Cu-780 (AG 401 and copper (grade CF032A. Structural examination was performed by means of light microscopy, scanning electron microscope (SEM and energy dispersion spectrometer (EDS. Furthermore, the article reveals the results of shear strength tests involving the aforementioned joints.

  6. Heat transfer in a low latitude flat-plate solar collector

    Directory of Open Access Journals (Sweden)

    Oko C.O.C.

    2012-01-01

    Full Text Available Study of rate of heat transfer in a flat-plate solar collector is the main subject of this paper. Measurements of collector and working fluid temperatures were carried out for one year covering the harmattan and rainy seasons in Port Harcourt, Nigeria, which is situated at the latitude of 4.858oN and longitude of 8.372oE. Energy balance equations for heat exchanger were employed to develop a mathematical model which relates the working fluid temperature with the vital collector geometric and physical design parameters. The exit fluid temperature was used to compute the rate of heat transfer to the working fluid and the efficiency of the transfer. The optimum fluid temperatures obtained for the harmattan, rainy and yearly (or combined seasons were: 317.4, 314.9 and 316.2 [K], respectively. The corresponding insolation utilized were: 83.23, 76.61 and 79.92 [W/m2], respectively, with the corresponding mean collector efficiency of 0.190, 0.205 and 0.197 [-], respectively. The working fluid flowrate, the collector length and the range of time that gave rise to maximum results were: 0.0093 [kg/s], 2.0 [m] and 12PM - 13.00PM, respectively. There was good agreement between the computed and the measured working fluid temperatures. The results obtained are useful for the optimal design of the solar collector and its operations.

  7. A screening method for the optimal selection of plate heat exchanger configurations

    Directory of Open Access Journals (Sweden)

    Pinto J.M.

    2002-01-01

    Full Text Available An optimization method for determining the best configuration(s of gasketed plate heat exchangers is presented. The objective is to select the configuration(s with the minimum heat transfer area that still satisfies constraints on the number of channels, the pressure drop of both fluids, the channel flow velocities and the exchanger thermal effectiveness. The configuration of the exchanger is defined by six parameters, which are as follows: the number of channels, the numbers of passes on each side, the fluid locations, the feed positions and the type of flow in the channels. The resulting configuration optimization problem is formulated as the minimization of the exchanger heat transfer area and a screening procedure is proposed for its solution. In this procedure, subsets of constraints are successively applied to eliminate infeasible and nonoptimal solutions. Examples show that the optimization method is able to successfully determine a set of optimal configurations with a minimum number of exchanger evaluations. Approximately 5 % of the pressure drop and channel velocity calculations and 1 % of the thermal simulations are required for the solution.

  8. Effect of Mg Content on the Microstructure and Toughness of Heat-Affected Zone of Steel Plate after High Heat Input Welding

    Science.gov (United States)

    Xu, Long-Yun; Yang, Jian; Wang, Rui-Zhi; Wang, Yu-Nan; Wang, Wan-Lin

    2016-07-01

    The effect of Mg content on the microstructure and toughness of the heat-affected zone (HAZ) of steel plates after high heat input welding was investigated by means of welding thermal simulation test and in situ observation through high-temperature laser scanning confocal microscopy. It was found that with the increase of Mg content in the steel, the former austenite grain sizes were greatly decreased and the mainly microstructural constituents in HAZ were changed from the brittle constituents of Widmanstätten ferrite, ferrite side plate and upper bainite to the ductile constituents of intragranular acicular ferrite and polygonal ferrite. The proportion of grain boundary ferrite was decreased greatly with the further addition of Mg from 27 to 99 ppm. As a result, the HAZ toughness after welding with heat input of 400 kJ cm-1 is increased with increasing Mg content in the steel plate.

  9. Analysis technology in the thick plate free drop impact, heat and thermal stress of the cask for radioactive material transport

    International Nuclear Information System (INIS)

    In this study, The regulatory condition and analysis condition is analyzed for thick plate free drop, heat and thermal stress analysis to develop the safety assessment technology. Analysis is performed with finite element method which is one of the many analysis methods of the shipping cask. ANSYS, LS-DYNA3D and ABAQUS is suitable for thick plate free drop, heat and thermal stress analysis of the shipping cask. For the analysis model, the KSC-4 that is the shipping cask to transport spent nuclear fuel is investigated. The results of both LS-DYNA3D and ABAQUS for thick plate free drop and the results of ANSYS, LS-DYNA3D and ABAQUS for heat and thermal stress analysis is completely corresponded. And the integrity of the shipping cask is verified. Using this study, the reliable safety assessment technology is supplied to the staff. The efficient and reliable regulatory tasks is performed using the standard safety assessment technology

  10. Analysis technology in the thick plate free drop impact, heat and thermal stress of the cask for radioactive material transport

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Dew Hey [Korea Institute of Nuclear and Safety, Taejon (Korea, Republic of); Lee, Young Shin; Ryu, Chung Hyun; Kim, Hyun Su; Choi, Kyung Joo; Choi, Young Jin; Lee, Jae Hyung; Na, Jae Yun; Kim, Seong Jong [Chungnam National Univ., Taejon (Korea, Republic of)

    2002-03-15

    In this study, The regulatory condition and analysis condition is analyzed for thick plate free drop, heat and thermal stress analysis to develop the safety assessment technology. Analysis is performed with finite element method which is one of the many analysis methods of the shipping cask. ANSYS, LS-DYNA3D and ABAQUS is suitable for thick plate free drop, heat and thermal stress analysis of the shipping cask. For the analysis model, the KSC-4 that is the shipping cask to transport spent nuclear fuel is investigated. The results of both LS-DYNA3D and ABAQUS for thick plate free drop and the results of ANSYS, LS-DYNA3D and ABAQUS for heat and thermal stress analysis is completely corresponded. And the integrity of the shipping cask is verified. Using this study, the reliable safety assessment technology is supplied to the staff. The efficient and reliable regulatory tasks is performed using the standard safety assessment technology.

  11. Critical heat flux analysis on change of plate temperature and cooling water flow rate for rectangular narrow gap with bilateral-heated cases

    International Nuclear Information System (INIS)

    Boiling heat transfer phenomena on rectangular narrow gap was related to the safety of nuclear reactors. Research done in order to study the safety of nuclear reactors in particular relating to boiling heat transfer and useful on the improvement of next-generation reactor designs. The research focused on calculation of the heat flux during the cooling process in rectangular narrow gap size 1.0 mm. with initial temperatures 200°C. 400°C, and 600°C, also the flow rates of cooling water 0,1 liters/second. 0,2 liters/second. and 0,3 liters/second. Experiments carried out by injecting water at a certain flow rate with the water temperature 85°C. Transient temperature measurement data recorded by the data acquisition system. Transient temperature measurement data is used to calculate the flux of heat gain is then used to obtain the heat transfer coefficient. This research aimed to obtain the correlation between critical heat flux and heat transfer coefficient to changes in temperatures and water flow rates for bilaterally-heated cases on rectangular narrow gap. The results obtained for a constant cooling water flow rate, critical heat flux will increase when hot plate temperature also increased. While on a constant hot plate temperature, coefficient heat transfer will increase when cooling water flow rate also increased. Thus it can be said that the cooling water flow rate and temperature of the hot plate has a significant effect on the critical heat flux and heat transfer coefficient resulted in quenching process of vertical rectangular narrow gap with double-heated cases. (author)

  12. A comparison of micro-structured flat-plate and cross-cut heat sinks for thermoelectric generation application

    International Nuclear Information System (INIS)

    Highlights: • Plate-fin and cross-cut heat sinks (PFHS, CCHS) are compared for TEG application. • The three-dimensional governing equations for flow and thermoelectrics are solved. • Power generation, pumping power and optimal thermoelectric net power are studied. • Overall net power in the TEG with PFHS is slightly superior to that with CCHS. • Results are in a good agreement with the previous computational studies. - Abstract: Heat sink configuration has strong impact on net power output from thermoelectric generators (TEGs). A weak cooling strategy can even cause negative net power output from the thermoelectric device. However, the net power output can be significantly improved by optimal design of the heat sink. In this study, a micro-structured plate-fin heat sink is compared to a modified design of cross-cut heat sink applied to TEGs over a range of temperatures and thermal conductivities. The particular focus of this study is to explore the net power output from the TEG module. The three-dimensional governing equations for the flow and heat transfer are solved using computational fluid dynamics (CFD) in conjunction with the thermoelectric characteristics of the TEG over a wide range of flow inlet velocities. The results show that at small flow inlet velocity, the maximum net power output in TEG with plate-fin heat sink is higher, while the TEG with cross-cut heat sink has higher maximum net power output at high flow inlet velocity. The maximum net power output is equal in the TEGs with plate-fin heat sink and cross-cut heat sink

  13. Characteristics of dissimilar laser-brazed joints of isotropic graphite to WC–Co alloy

    International Nuclear Information System (INIS)

    Highlights: ► Ti was required in the filler metal for brazing graphite to WC–Co alloy. ► The shear strength of the joint increased with Ti content up to 1.7 mass%. ► Ti concentrated at the interface of graphite/filler metal. ► TiC was formed at the interface of graphite/filler metal. - Abstract: The effect of Ti serving as an activator in a eutectic Ag–Cu alloy filler metal in dissimilar laser-brazed joints of isotropic graphite and a WC–Co alloy on the joint strength and the interface structure of the joint is investigated in this study. To evaluate the joint characteristics, the Ti content in the filler metal was increased from 0 to 2.8 mass%. The laser brazing was carried out by irradiating a laser beam selectively on the WC–Co alloy plate in Ar atmosphere. The threshold content of Ti required to join isotropic graphite to WC–Co alloy was 0.4 mass%. The shear strength at the brazed joint increased rapidly with increasing Ti content up to 1.7 mass%, and a higher Ti content was found to be likely to saturate the shear strength to a constant value of about 14 MPa. The isotropic graphite blocks also fractured at this content. The concentration of Ti observed at the interface between isotropic graphite and the filler metal indicates the formation of an intermetallic layer of TiC.

  14. MHD forced convective laminar boundary layer flow from a convectively heated moving vertical plate with radiation and transpiration effect.

    Science.gov (United States)

    Uddin, Md Jashim; Khan, Waqar A; Ismail, A I Md

    2013-01-01

    A two-dimensional steady forced convective flow of a Newtonian fluid past a convectively heated permeable vertically moving plate in the presence of a variable magnetic field and radiation effect has been investigated numerically. The plate moves either in assisting or opposing direction to the free stream. The plate and free stream velocities are considered to be proportional to x(m) whilst the magnetic field and mass transfer velocity are taken to be proportional to x((m-1)/2) where x is the distance along the plate from the leading edge of the plate. Instead of using existing similarity transformations, we use a linear group of transformations to transform the governing equations into similarity equations with relevant boundary conditions. Numerical solutions of the similarity equations are presented to show the effects of the controlling parameters on the dimensionless velocity, temperature and concentration profiles as well as on the friction factor, rate of heat and mass transfer. It is found that the rate of heat transfer elevates with the mass transfer velocity, convective heat transfer, Prandtl number, velocity ratio and the magnetic field parameters. It is also found that the rate of mass transfer enhances with the mass transfer velocity, velocity ratio, power law index and the Schmidt number, whilst it suppresses with the magnetic field parameter. Our results are compared with the results existing in the open literature. The comparisons are satisfactory. PMID:23741295

  15. MHD forced convective laminar boundary layer flow from a convectively heated moving vertical plate with radiation and transpiration effect.

    Directory of Open Access Journals (Sweden)

    Md Jashim Uddin

    Full Text Available A two-dimensional steady forced convective flow of a Newtonian fluid past a convectively heated permeable vertically moving plate in the presence of a variable magnetic field and radiation effect has been investigated numerically. The plate moves either in assisting or opposing direction to the free stream. The plate and free stream velocities are considered to be proportional to x(m whilst the magnetic field and mass transfer velocity are taken to be proportional to x((m-1/2 where x is the distance along the plate from the leading edge of the plate. Instead of using existing similarity transformations, we use a linear group of transformations to transform the governing equations into similarity equations with relevant boundary conditions. Numerical solutions of the similarity equations are presented to show the effects of the controlling parameters on the dimensionless velocity, temperature and concentration profiles as well as on the friction factor, rate of heat and mass transfer. It is found that the rate of heat transfer elevates with the mass transfer velocity, convective heat transfer, Prandtl number, velocity ratio and the magnetic field parameters. It is also found that the rate of mass transfer enhances with the mass transfer velocity, velocity ratio, power law index and the Schmidt number, whilst it suppresses with the magnetic field parameter. Our results are compared with the results existing in the open literature. The comparisons are satisfactory.

  16. Heat transfer between two parallel porous plates for Couette flow under pressure gradient and Hall current

    Indian Academy of Sciences (India)

    Hazem A Attia; W Abbas; Mostafa A M Abdeen; Ahmed A M Said

    2015-02-01

    The aim of the present paper is to study the unsteady magneto-hydrodynamic viscous Couette flow with heat transfer in a Darcy porous medium between two infinite parallel porous plates considering Hall effect, and temperature dependent physical properties under constant pressure gradient. The parallel plates are assumed to be porous and subjected to a uniform suction from above and injection from below while the fluid is flowing through a porous medium that is assumed to obey Darcy’s law. A numerical solution for the governing nonlinear partial differential equations coupled with set of momentum equations and the energy equation including the viscous and Joule dissipations is adopted. The effect of the porosity of the medium, the Hall current and the temperature dependent viscosity and thermal conductivity on both the velocity and temperature distributions are investigated. It is found that the porosity numberMhas a marked effect on decreasing the velocity distribution (owing to a simultaneous increase in Darcy porous drag). Also the temperature T is decreased considerably with increasing porosity number.With increasing Hall current parameter m, the velocity component u (x-direction) is considerably increased, whereas velocity component w (z-direction) is reduced. Temperatures are decreased in the early stages of flow but effectively increased in the steady state with increasing m.

  17. Effects of transverse magnetic field on a rotating micropolar fluid between parallel plates with heat transfer

    Science.gov (United States)

    Mehmood, Rashid; Nadeem, S.; Masood, S.

    2016-03-01

    Hydromagnetic flow of a micropolar fluid between two horizontal parallel plates in a rotating system has been investigated. The governing partial differential equations for momentum, energy and micro-rotation are presented and transformed into ordinary differential equations by means of similarity transformations. The solutions for velocity, temperature and micro-rotation profiles are expressed through graphs against various emerging physical parameters such as coupling parameter, viscosity parameter, Hartman number, Reynold number, rotation parameter, porosity parameter and peclet number using optimal homotopy analysis method (OHAM). Local skin friction co-efficient and local heat fluxes are computed analytically using OHAM as well as numerically through mid-point integration scheme and they are found to be in excellent agreement. It has been observed that local skin friction is higher for the case of strong concentration compare to the case of weak concentration. Moreover, influence of strong and weak concentration on Nusselt number is also examined.

  18. Dynamic characteristics of heat exchanger tubes vibrating in a tube support plate inactive mode

    International Nuclear Information System (INIS)

    Tubes in shell-and-tube heat exchangers, including nuclear plant steam generators, derive their support from longitudinally positioned tube support plates (TSPs). Typically there is a clearance between the tube and TSP hole. Depending on design and fabrication tolerances, the tube may or may not contact all of the TSPs. Noncontact results in an inactive TSP which can lead to detrimental flow induced tube vibrations under certain conditions dependent on the resulting tube-TSP interaction dynamics and the fluid excitation forces. The purpose of this study is to investigate the tube-TSP interaction dynamics. Results of an experimental study of damping and natural frequency as functions of tube-TSP diametral clearance and TSP thickness are reported. Calculated values of damping ratio and frequency of a tube vibrating within an inactive TSP are also presented together with a comparison of calculated and experimetnal quantities

  19. High temperature brazing of diamond tools

    Institute of Scientific and Technical Information of China (English)

    YAO Zheng-jun; SU Hong-hua; FU Yu-can; XU Hong-jun

    2005-01-01

    A new brazing technique of diamond was developed. Using this new technique optimum chemical and metallurgical bonding between the diamond grits and the carbon steel can be achieved without any thermal damages to diamond grits. The results of microanalysis and X-ray diffraction analysis reveal that a carbide layer exists between the diamond and the matrix, which consists of Cr3C2, Cr7C3 and Cr23C6. Performance tests show that the brazed diamond core-drill has excellent machining performance. In comparison with traditional electroplated diamond core-drill, the brazed diamond core-drill manufactured using the new developed technique has much higher machining efficiency and much longer operating life.

  20. Dry/wet performance of a plate-fin air-cooled heat exchanger with continuous corrugated fins

    International Nuclear Information System (INIS)

    The performance and operating characteristics of a plate-fin heat exchanger in dry/wet or deluge operations was experimentally determined. Development of the deluge heat/mass transfer model continued. The experiments were conducted in a specially-designed wind tunnel at the PNL. Air that was first heated and humidified to specified conditions was circulated at a controlled rate through a 2 ft x 6 ft heat exchanger module. The heat exchanger used in the tests was a wavy surface, plate fin on tube configuration. Hot water was circulated through the tubes at high flow rates to maintain an essentially isothermal condition on the tube side. Deionized water sprayed on the top of the vertically oriented plate fins was collected at the bottom of the core and recirculated. Instrumentation was provided for measurement of flow rates and thermodynamic conditions in the air, in the core circulation water, and in the deluge water. Measurements of the air side pressure drop and heat rejection rate were made as a function of air flow rate, air inlet temperature and humidity, deluge water flow rate, and the core inclination from the vertical. An overall heat transfer coefficient and an effective deluge film convective coefficient was determined. The deluge model, for predicting heat transfer from a wet finned heat exchanger was further developed and refined, and a major extension of the model was formulated that permits simultaneous calculation of both the heat transfer and evaporation rates from the wetted surface. The experiments showed an increase in the heat rejection rate due to wetting, accompanied by a proportional increase in the air side pressure drop. For operation at the same air side pressure drop, the enhancement ratio Q/sub w//Q/sub d/ varied between 2 and 5 for the conditions tested. Thus, the potential enhancement of heat transfer due to wetting can be substantial

  1. Dry/wet performance of a plate-fin air-cooled heat exchanger with continuous corrugated fins

    Energy Technology Data Exchange (ETDEWEB)

    Hauser, S.G.; Kreid, D.K.; Johnson, B.M.

    1981-01-01

    The performance and operating characteristics of a plate-fin heat exchanger in dry/wet or deluge operations was experimentally determined. Development of the deluge heat/mass transfer model continued. The experiments were conducted in a specially-designed wind tunnel at the PNL. Air that was first heated and humidified to specified conditions was circulated at a controlled rate through a 2 ft x 6 ft heat exchanger module. The heat exchanger used in the tests was a wavy surface, plate fin on tube configuration. Hot water was circulated through the tubes at high flow rates to maintain an essentially isothermal condition on the tube side. Deionized water sprayed on the top of the vertically oriented plate fins was collected at the bottom of the core and recirculated. Instrumentation was provided for measurement of flow rates and thermodynamic conditions in the air, in the core circulation water, and in the deluge water. Measurements of the air side pressure drop and heat rejection rate were made as a function of air flow rate, air inlet temperature and humidity, deluge water flow rate, and the core inclination from the vertical. An overall heat transfer coefficient and an effective deluge film convective coefficient was determined. The deluge model, for predicting heat transfer from a wet finned heat exchanger was further developed and refined, and a major extension of the model was formulated that permits simultaneous calculation of both the heat transfer and evaporation rates from the wetted surface. The experiments showed an increase in the heat rejection rate due to wetting, accompanied by a proportional increase in the air side pressure drop. For operation at the same air side pressure drop, the enhancement ratio Q/sub w//Q/sub d/ varied between 2 and 5 for the conditions tested. Thus, the potential enhancement of heat transfer due to wetting can be substantial.

  2. Assessing braze quality in the actively cooled Tore Supra Phase III outboard pump limiter

    International Nuclear Information System (INIS)

    The quality of brazing of pyrolytic graphite armor brazed to copper tubes in Tore Supra's Phase III Outboard Pump Limiter was assessed through pre-service qualification testing of individual copper/tile assemblies. The evaluation used non-destructive, hot water transient heating tests performed in the high-temperature, high-pressure flow loop at Sandia's Plasma Materials Test Facility. Surface temperatures of tiles were monitored with an infrared camera as water at 120 degrees C at about 2.07 MPa (300 psi) passed through a tube assembly initially at 30 degrees C. For tiles with braze voids or cracks, the surface temperatures tagged behind those of adjacent well-bonded tiles. Temperature tags were correlated with flaw sizes observed during repairs based upon a detailed 2-D heat transfer analyses. open-quotes Badclose quotes tiles, i.e., temperature tags of 10-20 degrees C depending upon tile's size, were easy to detect and, when removed, revealed braze voids of roughly 50% of the joint area. Eleven of the 14 tubes were rebrazed after bad tiles were detected and removed. Three tubes were rebrazed twice

  3. Enhancement of Heat Transfer in a Liquid Metal Flow past a Thermally Conducting and Oscillating Infinite Flat Plate

    Directory of Open Access Journals (Sweden)

    Puvaneswari Puvaneswari

    2016-01-01

    Full Text Available The effect of conjugation on the enhancement of heat transfer in a liquid metal flow past a thermally conducting and sinusoidally oscillating infinite flat plate, when a constant temperature gradient is superimposed on the fluid, is investigated. The plate is made up of the materials compatible with the liquid metals used and is considered to be of finite thickness. Analytical solutions for the velocity and the temperature of the fluid and the solid are obtained. The effects of thermal conductivity and the thickness of the plate on the total time averaged heat flux transported and the thermal boundary layer thickness are investigated in detail. It is found that the effects of wall thickness and wall thermal conductivity on the heat flux transported depend on their effects on the transverse temperature gradient at any frequency. The optimum value of wall thickness at which the net heat flux transported attains the maximum value, for each fluid and for each wall material under consideration, is reported. A maximum increase of 46.14 % in the heat flux transported can be achieved by optimizing the wall thickness. A maximum convective heat flux of 1.87 × 108W/m2 is achieved using Na with AISI 316 wall. All the results obtained have been compared with the experimental and analytical results reported in the literature and are found to be in good agreement. It is believed that the new insights gained will be of significant use while designing liquid metal heat transfer systems.

  4. Structural Characterization and Mechanical Properties of As-plated and Heat Treated Electroless Ni-B-P Alloy Coatings

    Directory of Open Access Journals (Sweden)

    P. G. Venkatakrishnan

    2014-05-01

    Full Text Available The Ni-B-P alloy coatings were made autocatalytically (electroless using an alkaline plating bath with nickel chloride hexahydrate (NiCl2.6H2O as the source of nickel ions, sodium borohydride (NaBH4 and sodium hypophosphite (NaH2PO2 as reducing agents and source of boron and phosphorous ions, respectively. The effects of bath concentrations on the plating rate, composition of coating, surface morphology, structural features and microhardness have been studied by varying NaBH4 concentration in the plating bath from 0.2 to 0.8 g/l while keeping NaH2PO2 concentration constant (12 g/l. The plating rate and boron content of the electroless Ni-B-P ternary alloy coatings increased with increasing NaBH4 concentration in the plating bath. The scanning electron microscopic images revealed that the morphology of the coating changed from corn cob structure to coarse cauliflower structure with increasing borohydride concentration in the plating bath. Broadening of X-ray diffraction peak is observed, as the borohydride concentration is increased in the plating bath, which is attributed to the large reduction in the crystallite size of the Ni-B-P alloy coatings. The microhardness values of the coating increased with increasing borohydride concentration in the plating bath. The as-plated Ni-B-P alloy coating containing higher boron content (3.2 wt% shows higher hardness of 700 HV compared to other Ni-B-P alloy coatings. The XRD patterns of heat treated Ni-B-P alloy coatings (500 °C show Ni3B intermetallic peaks along with Ni peaks. The presence of Ni3B intermetallic compound significantly increases the microhardness values of the heat treated Ni-B-P alloy coatings.

  5. Silicon high vacuum brazing study and microstructural analysis of the joint formation; Estudo da brasagem de silicio em alto vacuo e analise microestructural da juncao

    Energy Technology Data Exchange (ETDEWEB)

    Santana, E.C.A. [Universidade Estadual Paulista - UNESP, Campus de Guaratingueta, SP (Brazil); Francisco, F.R.; Bagnato, O.R. [Laboratorio Nacional de Luz Sincrotron - LNLS, Campinas, SP (Brazil)], e-mail: erika.santana@lnls.br

    2010-07-01

    On the project of Synchrotron Light Source, silicon-crystal are often used as monochromator and mirrors, to reflect the electrons beam. Silicon is known as a very fragile material, and its optical elements must be designed carefully. Usually, it is bonded in a cooling support made by copper. Thermal contact between the crystal plate and cooling support is made of In-Ga liquid alloy. Due to the difficult of this bonding, brazing tests are being taken with Fe-Ni alloy, in order to improve the silicon mirrors application and performance. Wet ability tests were performed between the silicon plate and commercial fillers. A brazing test was made of silicon and Al12Si, as filler, with Fe-Ni, as base material. Results of microstructure analysis indicated that the braze of a silicon plate is quite promissory. (author)

  6. Experimental evaluation of an Internal Heat Exchanger in a CO2 subcritical refrigeration cycle with gas-cooler

    OpenAIRE

    Llopis Doménech, Rodrigo; Sanz Kock, Carlos; Cabello López, Ramón; Sánchez García-Vacas, Daniel; Torrella Alcaraz, Enrique

    2015-01-01

    We present the experimental evaluation of an internal heat exchanger or suction-line/liquid-line heat exchanger in a CO2 subcritical refrigeration plant with gas-cooler. The plant, driven by a 1.5kW CO2 semi hermetic compressor, uses brazed plate heat exchangers as condenser, evaporator and internal heat exchanger, an air finned tube gas-cooler and an electronic expansion valves. The evaluation (77 steady- states) covers evaporating temperatures from -40 to -25 oC and condensing temperatures ...

  7. Hydro-Magnetic Convection Heat Transfer in a Micropolar Fluid over a Vertical Plate

    Directory of Open Access Journals (Sweden)

    M. Ferdows

    2013-01-01

    Full Text Available The combined effect of Hall current, Ohmic heating and suction/injection on the hydro-magnetic free convective heat transfer in a micropolar boundary layer flow past a vertical plate is analyzed. The fluid is assumed to be viscous, incompressible and electrically conducting with a strong magnetic field. Using the modified Ohm’s law and the Bossinesq approximation the governing equations of the problem are transformed into a system of non-linear ordinary differential equations by introducing a suitable similarity transformation. The resulting boundary value problem is solved numerically by Nachtsheim-Swigert shooting technique with a sixth order Runge- Kutta iteration scheme. The results are obtained to study the effects of the governing parameters, suction/injection parameter , magnetic parameter , Hall current parameter , material parameter , microrotational parameter , the Prandtl number and the Brinkman number( on the transport behaviors of the fluid. That is a parametric study is performed to illustrate the influence of these parameters on the velocity and temperature distribution as well as the local skin-friction and the local Nusselt number. Furthermore, the numerical solutions obtained in this study are compared with the existing results in the literature for some special values of and the results are found to be in a good agreement.

  8. The influence of heat treatment on microstructure and crack resistance of boron microalloyed steel plates

    Directory of Open Access Journals (Sweden)

    M. Opiela

    2010-11-01

    Full Text Available crack resistance of C-Mn constructional steels with microaddition of boron assigned to be used in production of high strength steel plates.Design/methodology/approach: Metallographic observations, heat treatment, hardness measurements, impact strength examinations, fractographic analyses of fracture surfaces of test pieces have been performed.Findings: Dispersive particles of interstitial phases formed on dislocations during the plastic deformation, limiting grain growth of austenite, create the possibility to obtain metallurgical products with fine-grained microstructure giving them high strength and guaranteed crack resistance, also at low temperature.Research limitations/implications: Further research of microstructure in transmission electron microscope as well as complementary impact resistance tests at the temperature lower than -60°C are foreseen to be performed.Practical implications: Obtained results of examinations, especially detailed fractographic analysis of fracture surfaces of test pieces together with chemical composition analysis of revealed non-metallic inclusions and precipitations of secondary phases will make contribution to better understanding of cracking mechanisms in the group of high-strength steels.Originality/value: Performed research revealed that investigated steels present high crack resistance also at low temperature. It can be achieved through proper selection of chemical composition and adequate conditions of heat treatment and plastic working. The presence of microadditions of transition metals deriving from IVb and Vb group of periodic classification of the elements with high chemical affinity to nitrogen and carbon allows producing rolled products with high exploitation properties.

  9. Numerical Study Of The Heat Transfer Phenomenon Of A Rectangular Plate Including Void, Notch Using Finite Difference Technique

    OpenAIRE

    Deb Nath S.K.; Peyada N.K.

    2015-01-01

    In the present study, we have developed a code using Matlab software for solving a rectangular aluminum plate having void, notch, at different boundary conditions discretizing a two dimensional (2D) heat conduction equation by the finite difference technique. We have solved a 2D mixed boundary heat conduction problem analytically using Fourier integrals (Deb Nath et al., 2006; 2007; 2007; Deb Nath and Ahmed, 2008; Deb Nath, 2008; Deb Nath and Afsar, 2009; Deb Nath and Ahmed, 2009; 2009; Deb N...

  10. DNS of heat transfer in transitional, accelerated boundary layer flow over a flat plate affected by free-stream fluctuations

    International Nuclear Information System (INIS)

    Direct numerical simulations (DNS) of flow over and heat transfer from a flat plate affected by free-stream fluctuations were performed. A contoured upper wall was employed to generate a favourable streamwise pressure gradient along a large portion of the flat plate. The free-stream fluctuations originated from a separate LES of isotropic turbulence in a box. In the laminar portions of the accelerating boundary layer flow the formation of streaks was observed to induce an increase in heat transfer by the exchange of hot fluid near the surface of the plate and cold fluid from the free-stream. In the regions where the streamwise pressure gradient was only mildly favourable, intermittent turbulent spots were detected which relaminarised downstream as the streamwise pressure gradient became stronger. The relaminarisation of the turbulent spots was reflected by a slight decrease in the friction coefficient, which converged to its laminar value in the region where the streamwise pressure gradient was strongest.

  11. Study of the thermal performance of external and internal finned plate-heat exchangers for nuclear steam generator application

    International Nuclear Information System (INIS)

    The present study points out two main categories of steam generators for nuclear plants with PWR reactor, on one side of the Babcok and Wilcox type, and on the other side of the Westinghouse type. The present study examines, from a recent patent, the possibility to add internal and external fins in the steam generator exchangers of PWR reactors. The finned-plate heat exchanger is first described. The thermal characteristics of a finned-plate and of an exchanger including these plates are tested. The theoretical study and the experiment are both presented. The study deals more particularly with the evaluation of the global heat exchange coefficient that the internal fins allow to improve. The experiment has been carried out for different flow rates and at different temperatures

  12. New similarity solution of boundary layer flow along a continuously moving convectively heated horizontal plate by deductive group method

    OpenAIRE

    Uddin Mohammed Jashim; Khan Waqar Ahamed; Ismail Ahmad Izani; Hamad M.A.A.

    2015-01-01

    A mathematical model is presented and analyzed for steady two-dimensional non-isothermal laminar free convective boundary layer flow along a convectively heated moving horizontal plate. New similarity transformations are developed using one parameter deductive group transformations and hence the governing transport equations are reduced to a system of coupled, nonlinear ordinary differential equations with associated boundary conditions. The reduced equatio...

  13. 46 CFR 57.06-1 - Production test plate requirements.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Production test plate requirements. 57.06-1 Section 57.06-1 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING WELDING AND BRAZING Production Tests § 57.06-1 Production test plate requirements. (a) Production test plates shall be provided for Class I, Class I-L, Class...

  14. Brazing of photocathode RF gun structures in Hydrogen atmosphere: Process qualification, effect of brazing on RF properties and vacuum compatibility

    International Nuclear Information System (INIS)

    In this paper, we report on the development of a brazing process for an ultra-high vacuum (UHV) compatible photocathode RF gun structure developed at our Centre. The choice of brazing alloy and its form, brazing clearance between parts to be joined and the brazing cycle adopted have been qualified through metallographic examination of identical joints on an OFE copper prototype that was cut open after brazing. The quality of brazed joint not only affects the UHV compatibility of the gun, but also influences the RF parameters finally achieved. A 2-D electromagnetic code, SUPERFISH, was used to predict the variation in RF parameters before and after brazing considering actual brazing clearances provided between the parts to be joined. Results obtained from low power RF measurements on the brazed gun structure confirm the integrity of the brazed joints and show good agreement with those predicted by electromagnetic simulations. The brazed gun structure has been leak-tested and pumped down to a vacuum level limited by the vacuum compatibility of the flange-fittings employed in the setup.

  15. Brazing of photocathode RF gun structures in Hydrogen atmosphere: Process qualification, effect of brazing on RF properties and vacuum compatibility

    Science.gov (United States)

    Kak, Ajay; Kulshreshtha, P.; Lal, Shankar; Kaul, Rakesh; Ganesh, P.; Pant, K. K.; Abhinandan, Lala

    2012-11-01

    In this paper, we report on the development of a brazing process for an ultra-high vacuum (UHV) compatible photocathode RF gun structure developed at our Centre. The choice of brazing alloy and its form, brazing clearance between parts to be joined and the brazing cycle adopted have been qualified through metallographic examination of identical joints on an OFE copper prototype that was cut open after brazing. The quality of brazed joint not only affects the UHV compatibility of the gun, but also influences the RF parameters finally achieved. A 2-D electromagnetic code, SUPERFISH, was used to predict the variation in RF parameters before and after brazing considering actual brazing clearances provided between the parts to be joined. Results obtained from low power RF measurements on the brazed gun structure confirm the integrity of the brazed joints and show good agreement with those predicted by electromagnetic simulations. The brazed gun structure has been leak-tested and pumped down to a vacuum level limited by the vacuum compatibility of the flange-fittings employed in the setup.

  16. Characteristic of local boiling heat transfer of ammonia and ammonia / water binary mixture on the plate type evaporator

    Science.gov (United States)

    Okamoto, Akio; Arima, Hirofumi; Ikegami, Yasuyuki

    2011-08-01

    Power generation using small temperature difference such as ocean thermal energy conversion (OTEC) and discharged thermal energy conversion (DTEC) is expected to be the countermeasures against global warming problem. As ammonia and ammonia/water are used in evaporators for OTEC and DTEC as working fluids, the research of their local boiling heat transfer is important for improvement of the power generation efficiency. Measurements of local boiling heat transfer coefficients were performed for ammonia /water mixture ( z = 0.9-1) on a vertical flat plate heat exchanger in a range of mass flux (7.5-15 kg/m2 s), heat flux (15-23 kW/m2), and pressure (0.7-0.9 MPa). The result shows that in the case of ammonia /water mixture, the local heat transfer coefficients increase with an increase of mass flux and composition of ammonia, and decrease with an increase of heat flux.

  17. Residual Stress in Brazing of Submicron Al2O3 to WC-Co

    Science.gov (United States)

    Grunder, T.; Piquerez, A.; Bach, M.; Mille, P.

    2016-07-01

    This study evaluated the residual stresses induced by brazing and grinding submicron Al2O3, using different methods. Energy dispersive x-ray spectrometry analysis (EDX) of 72Ag-Cu filler and filler/WC-Co interface showed evidence of atomic diffusion and possible formation of titanium oxide layers between the joint and the bonding materials. An analytical model supported by the finite element method (FEM) based on strain determination due to the difference in variation of thermal expansion was used to assess the stress distribution at the coupling interface and in bulk materials. The model took into account the evolution of the Young's modulus and of the thermal expansion with temperature. The model could be used to follow strain and stress evolutions of the bonded materials during the cooling cycle. The maximum stress rose above -300 MPa at the center of the 100 × 100 × 3 mm ceramic plates. The residual stresses on the external surface of ceramic were investigated by x-ray diffraction (XRD) and indentation fracture method (IFM). After brazing and grinding the plate, the principal stresses were 128.1 and 94.9 MPa, and the shear stress was -20.1 MPa. Microscopic examination revealed grain pull-out promoted by the global residual stresses induced by the brazing and grinding processes. The surface stresses evaluated by the different methods were reasonably correlated.

  18. Residual Stress in Brazing of Submicron Al2O3 to WC-Co

    Science.gov (United States)

    Grunder, T.; Piquerez, A.; Bach, M.; Mille, P.

    2016-06-01

    This study evaluated the residual stresses induced by brazing and grinding submicron Al2O3, using different methods. Energy dispersive x-ray spectrometry analysis (EDX) of 72Ag-Cu filler and filler/WC-Co interface showed evidence of atomic diffusion and possible formation of titanium oxide layers between the joint and the bonding materials. An analytical model supported by the finite element method (FEM) based on strain determination due to the difference in variation of thermal expansion was used to assess the stress distribution at the coupling interface and in bulk materials. The model took into account the evolution of the Young's modulus and of the thermal expansion with temperature. The model could be used to follow strain and stress evolutions of the bonded materials during the cooling cycle. The maximum stress rose above -300 MPa at the center of the 100 × 100 × 3 mm ceramic plates. The residual stresses on the external surface of ceramic were investigated by x-ray diffraction (XRD) and indentation fracture method (IFM). After brazing and grinding the plate, the principal stresses were 128.1 and 94.9 MPa, and the shear stress was -20.1 MPa. Microscopic examination revealed grain pull-out promoted by the global residual stresses induced by the brazing and grinding processes. The surface stresses evaluated by the different methods were reasonably correlated.

  19. MHD Heat and Mass Transfer of Chemical Reaction Fluid Flow over a Moving Vertical Plate in Presence of Heat Source with Convective Surface Boundary Condition

    Directory of Open Access Journals (Sweden)

    B. R. Rout

    2013-01-01

    Full Text Available This paper aims to investigate the influence of chemical reaction and the combined effects of internal heat generation and a convective boundary condition on the laminar boundary layer MHD heat and mass transfer flow over a moving vertical flat plate. The lower surface of the plate is in contact with a hot fluid while the stream of cold fluid flows over the upper surface with heat source and chemical reaction. The basic equations governing the flow, heat transfer, and concentration are reduced to a set of ordinary differential equations by using appropriate transformation for variables and solved numerically by Runge-Kutta fourth-order integration scheme in association with shooting method. The effects of physical parameters on the velocity, temperature, and concentration profiles are illustrated graphically. A table recording the values of skin friction, heat transfer, and mass transfer at the plate is also presented. The discussion focuses on the physical interpretation of the results as well as their comparison with previous studies which shows good agreement as a special case of the problem.

  20. Thermal performance of perforated plate matrix heat exchangers with effects from outer wall and flow channel geometry

    Science.gov (United States)

    Sunil Kumar, S.; Ratna Raju, L.; Nandi, T. K.

    2015-12-01

    The performance of high effectiveness (high NTU) perforated plate matrix heat exchangers (MHEs) is dependent on the geometry of the flow channels, as well as the longitudinal heat conduction through the outer walls. The effect of the above factors on the performance of MHEs is investigated in this paper numerically. The results obtained with the present model are validated with our own experimental results as well as those in the literature. The results show a strong influence of longitudinal heat conduction through the outer wall on the performance of MHEs. A parametric study has been carried out to arrive at the optimum flow channel geometry under given operating conditions.

  1. Active vacuum brazing of CNT films to metal substrates for superior electron field emission performance

    International Nuclear Information System (INIS)

    The joining of macroscopic films of vertically aligned multiwalled carbon nanotubes (CNTs) to titanium substrates is demonstrated by active vacuum brazing at 820 °C with a Ag–Cu–Ti alloy and at 880 °C with a Cu–Sn–Ti–Zr alloy. The brazing methodology was elaborated in order to enable the production of highly electrically and thermally conductive CNT/metal substrate contacts. The interfacial electrical resistances of the joints were measured to be as low as 0.35 Ω. The improved interfacial transport properties in the brazed films lead to superior electron field-emission properties when compared to the as-grown films. An emission current of 150 μA was drawn from the brazed nanotubes at an applied electric field of 0.6 V μm−1. The improvement in electron field-emission is mainly attributed to the reduction of the contact resistance between the nanotubes and the substrate. The joints have high re-melting temperatures up to the solidus temperatures of the alloys; far greater than what is achievable with standard solders, thus expanding the application potential of CNT films to high-current and high-power applications where substantial frictional or resistive heating is expected. (paper)

  2. Local distribution of wall static pressure and heat transfer on a smooth flat plate impinged by a slot air jet

    Science.gov (United States)

    Adimurthy, M.; Katti, Vadiraj V.

    2016-06-01

    Local distribution of wall static pressure and heat transfer on a smooth flat plate impinged by a normal slot air jet is experimental investigated. Present study focuses on the influence of jet-to-plate spacing (Z/D h ) (0.5-10) and Reynolds number (2500-20,000) on the fluid flow and heat transfer distribution. A single slot jet with an aspect ratio (l/b) of about 22 is chosen for the current study. Infrared Thermal Imaging technique is used to capture the temperature data on the target surface. Local heat transfer coefficients are estimated from the thermal images using `SMART VIEW' software. Wall static pressure measurement is carried out for the specified range of Re and Z/D h . Wall static pressure coefficients are seen to be independent of Re in the range between 5000 and 15,000 for a given Z/D h . Nu values are higher at the stagnation point for all Z/D h and Re investigated. For lower Z/D h and higher Re, secondary peaks are observed in the heat transfer distributions. This may be attributed to fluid translating from laminar to turbulent flow on the target plate. Heat transfer characteristics are explained based on the simplified flow assumptions and the pressure data obtained using Differential pressure transducer and static pressure probe. Semi-empirical correlation for the Nusselt number in the stagnation region is proposed.

  3. Heat transfer and flow analysis of nanofluid flow between parallel plates in presence of variable magnetic field using HPM

    International Nuclear Information System (INIS)

    In this study, effect of variable magnetic field on nanofluid flow and heat transfer analysis between two parallel disks is investigated. By using the appropriate transformation for the velocity, temperature and concentration, the basic equations governing the flow, heat and mass transfer were reduced to a set of ordinary differential equations. These equations subjected to the associated boundary conditions were solved analytically using Homotopy perturbation method. The analytical investigation is carried out for different governing parameters namely: squeeze number, suction parameter, Hartmann number, Brownian motion parameter, thermophrotic parameter and Lewis number. Results show that Nusselt number has direct relationship with Brownian motion parameter and thermophrotic parameter but it is a decreasing function of squeeze number, suction parameter, Hartmann number and Lewis number. - Highlights: • Heat and mass transfer of nanofluids between parallel plates investigated. • A variable magnetic field is applied on the plates. • Governing equations are solved analytically. • Effects of physical parameters are discussed on the Nusselt number

  4. Heat transfer and flow analysis of nanofluid flow between parallel plates in presence of variable magnetic field using HPM

    Energy Technology Data Exchange (ETDEWEB)

    Hatami, M., E-mail: m.hatami@tue.nl [Esfarayen University of Technology, Mechanical Engineering Department, Esfarayen, North Khorasan (Iran, Islamic Republic of); Jing, Dengwei; Song, Dongxing [International Research Center for Renewable Energy, State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi' an 710049 (China); Sheikholeslami, M.; Ganji, D.D. [Department of Mechanical Engineering, Babol University of Technology, Babol (Iran, Islamic Republic of)

    2015-12-15

    In this study, effect of variable magnetic field on nanofluid flow and heat transfer analysis between two parallel disks is investigated. By using the appropriate transformation for the velocity, temperature and concentration, the basic equations governing the flow, heat and mass transfer were reduced to a set of ordinary differential equations. These equations subjected to the associated boundary conditions were solved analytically using Homotopy perturbation method. The analytical investigation is carried out for different governing parameters namely: squeeze number, suction parameter, Hartmann number, Brownian motion parameter, thermophrotic parameter and Lewis number. Results show that Nusselt number has direct relationship with Brownian motion parameter and thermophrotic parameter but it is a decreasing function of squeeze number, suction parameter, Hartmann number and Lewis number. - Highlights: • Heat and mass transfer of nanofluids between parallel plates investigated. • A variable magnetic field is applied on the plates. • Governing equations are solved analytically. • Effects of physical parameters are discussed on the Nusselt number.

  5. A combined electron probe micro analysis and scanning Kelvin probe force microscopy study of a modified AA4xxx/AA3xxx aluminium brazing sheet

    International Nuclear Information System (INIS)

    Highlights: • SKPFM and FE-EPMA for a modified aluminium brazing sheet were performed. • Cross-sectional electrochemical properties of the material were measured. • Cross-sectional variation of microstructural chemistry was investigated. • The electrochemical responses were correlated to the microstructural features. • A solution for corrosion protection enhancement of the material was proposed. -- Abstract: The electrochemical and microstructural properties of the clad and core from a modified AA3xxx/AA4xxx brazing sheet were investigated before and after brazing. For this, scanning Kelvin probe force microscopy (SKPFM) and field emission electron probe micro analysis (FE-EPMA) were used. The Volta potential difference (VPD) was measured as a function of depth for the brazed and non-brazed sheets. This was correlated with the cross-sectional variation of chemistry and microstructure that result from brazing. Furthermore, potentiodynamic polarization experiments and subsequent microscopic analysis of the corroded samples were used to explore the corrosion mechanism of the modified brazed sheet. The investigation revealed that the major consequences of brazing for the microstructure are: an increase in the Si content of the matrix in the heat affected zone (HAZ); a non-uniform distribution of Cu in the HAZ; an accumulation of Cu in Al–Si eutectics and around the grain boundaries, including α-Al(Mn,Fe)Si and Al2Cu intermetallics; the presence of some continuous grain boundaries in both the clad and core of the sheet; and the non-uniform precipitation of intermetallics at Al–Si eutectic phases. The impact of these microstructural changes on the corrosion behaviour of the brazed sheet was: to increase the VPD of the re-solidified clad matrix; to introduce localized corrosion susceptibility on the brazed clad and core structures; and to reduce the cathodic protection power of the re-solidified clad material. As a result of the correlation between

  6. Denaturation Kinetics of Whey Protein Isolate Solutions and Fouling Mass Distribution in a Plate Heat Exchanger

    Directory of Open Access Journals (Sweden)

    Marwa Khaldi

    2015-01-01

    Full Text Available Few investigations have attempted to connect the mechanism of dairy fouling to the chemical reaction of denaturation (unfolding and aggregation occurring in the bulk. The objective of this study is to contribute to this aspect in order to propose innovative controls to limit fouling deposit formation. Experimental investigations have been carried out to observe the relationship between the deposit mass distribution generated in plate heat exchangers (PHE by a whey protein isolate (WPI mainly composed of β-lactoglobulin (β-Lg and the ratio between the unfolding and aggregation rate constants. Experiments using a PHE were carried out at a pilot scale to identify the deposit distribution of a model fouling solution with different calcium contents. In parallel, laboratory experiments were performed to determine the unfolding/aggregation rate constants. Data analysis showed that (i β-Lg denaturation is highly dependent on the calcium content, (ii for each fouling solution, irrespective of the imposed temperature profile, the deposit mass in each channel and the ratio between the unfolding and aggregation rate constants seem to be well correlated. This study demonstrates that both the knowledge of the thermal profile and the β-Lg denaturation rate constants are required in order to predict accurately the deposit distribution along the PHE.

  7. Influence of laser energy input mode on joint interface characteristics in laser brazing with Cu-base filler metal

    Institute of Scientific and Technical Information of China (English)

    LI Li-qun; FENG Xiao-song; CHEN Yan-bin

    2008-01-01

    The flange butt joints of 1 mm-thick galvanized steel sheets were brazed with CuSi3 as filler metal at different laser heating modes. The microstructures and element distributions of joint interface were investigated by SEM and EDS. The results show that there is no obvious interface layer with the circular individual beam heating and lamellar Fe-Si intermetallic compound layer is found with dual-beam laser spot heating. With the irradiation of rectangular laser spot, the joint interface layer is also formed. The layer thickness is larger than that of dual-beam brazing and the layer shape is fiat so that intermetallic compounds trend to grow into cellular crystals. Moreover, the interface layer shape also depends on its position in the joint. Under the high heat input, dendritic or granular intermetallic compounds dispersively distribute in brazing seam adjacent to the interface, which is caused by the melting or dissolving of the base metal. According to the results, the brazing quality can be controlled by laser heating mode and processing parameters.

  8. Heat transfer in the flow of a cold, axisymmetric vertical liquid jet against a hot, horizontal plate

    CERN Document Server

    Shu, Jian-Jun

    2014-01-01

    The paper considers heat transfer characteristics of thin film flow over a hot horizontal flat plate resulting from a cold vertical jet of liquid falling onto the surface. A numerical solution of high accuracy is obtained for large Reynolds numbers using the modified Keller box method. For the flat plate, solutions for axisymmetric jets are obtained. In a parallel approximation theory an advanced polynomial approximation for the velocity and temperature distribution is employed and results are good agreement with those obtained using a simple Pohlhausen polynomial and the numerical solutions.

  9. Effects of rotation and heat source on MHD free convective flow on vertically upwards heated plate with gravity modulation in slip flow region

    International Nuclear Information System (INIS)

    In the present paper we studied free convective unsteady flow of a viscous incompressible and rotating fluid in a porous medium past an infinite vertical plate with constant heat source and gravity modulation to the flow region. Expressions for velocity, temperature and concentration distribution are obtained by using perturbation technique. Also the expressions for the skin-friction coefficient, rate of heat transfer and Sherwood number are derived. The effects of Prandtl Number (Pr), Grashof number (Gr), modified Grashof number (Gc), frequency of oscillation, rotation parameter (E), heat source parameter (S*), gravity modulation parameter (α) and permeability parameter (K0) are analyzed and studied through graphs. It is found that primary velocity of fluid decreases with increase of rotation parameter whereas secondary velocity is increased near to the wall, and rate of heat transfer decreases with increase of heat source parameter. (author)

  10. Unsteady Hydromagnetic Flow of a Heat Absorbing Dusty Fluid Past a Permeable Vertical Plate with Ramped Temperature

    Directory of Open Access Journals (Sweden)

    m Das

    2014-01-01

    Full Text Available The unsteady flow and heat transfer of a viscous incompressible, electrically conducting dusty fluid past vertical plate under the influence of a transverse magnetic field is studied with a view to examine the combined effects of suction, heat absorption and ramped wall temperature. The temperature of the wall is assumed to have a temporarily ramped profile which goes on increasing up to a certain time limit and then becomes constant. To investigate the effect of rampedness in wall temperature, the solution for the flow past an isothermal wall is also obtained. The governing partial differential equations are solved using Laplace transformation technique in which the inversion is obtained numerically using Matlab. To validate the results of numerical inversion a comparison between the numerical and analytical values of fluid and particle temperatures and Nusselt number is also presented. The effects of pertinent flow parameters affecting the flow and heat transfer are investigated with the help of graphs and tables. It is found that the increase in suction, heat absorption and particle concentration contribute in thinning the thermal and momentum boundary layers and the velocity and temperature for both the fluid and particle phases are higher in the case of a flow past an isothermal plate than that of a flow past a plate with ramped temperature.

  11. Modeling and computation of heat exchanges in the configuration of an impinging jet on a hot plate

    International Nuclear Information System (INIS)

    The knowledge of the metal temperature history is essential, especially when strip leave the rolling mill, to get adequate final mechanical properties of steel. Some experiments have yet been carried out on the heat transfer associated with the impingement of a planar (1*9 mm2) subcooled (5-16 K) water jet on a heated plate. Complete boiling curves were then obtained at different locations from the stagnation point and it was observed a phenomenon of 'shoulder of flux' in the transition boiling region near the impingement point. The aim of this work is to compute the heat flux transferred between a very hot plate and a subcooled liquid under a planar impinging jet to obtain the transient temperature distribution in the plate. To achieve this goal, a physical modelling of the phenomenon of 'shoulder of flux' has been carried out. This modelling is based on the assumption that the apparition of periodic bubble oscillations at the wall surface is due to the hydrodynamic fragmentation by the jet. The relation derived from this modelling is validated against experimental results from the literature obtained for a wide range of jet velocity, subcooling and jet diameter. This model is implemented in the new multiphase flow solver developed by EDF 'SATURNE polyphasique'. Numerical results are then compared to experimental heat fluxes obtained on previous experiments. (authors)

  12. Advantages of reduced heat input during ChopArc-welding and brazing for coated and combined metals for light weight vehicles; Vorteile des waermearmen ChopArc-Schweissens und - Loetens bei beschichteten und artverschiedenen Blechen fuer Leichtfahrzeuge

    Energy Technology Data Exchange (ETDEWEB)

    Dorn, L.; Goecke, S.F. [Inst. fuer Werkzeugmaschinen und Fabrikbetrieb, TU-Berlin (Germany)

    2001-07-01

    In conventional MAG-short-arc-welding the arc burns after ignition non-defined with continuously energy input until the next short circuit. Thereby, stochastically process fluctuations are caused by the non controlled melting of the electrode tip. In the recently developed ChopArc process, after a defined extinguishing a non arcing phase follows without any energy input until the next short circuiting on the controlled melting of the electrode tip. Hence, with the ChopArc it is possible to realize a sticky melt for thin sheet, root pass and out-of-position welding, as well as a low melt viscosity for sufficient capillary effect in MAG-brazing. (orig.) [German] Beim herkoemmlichen MAG-Kurzlichtbogen-Schweissen brennt der Lichtbogen nach seiner Zuendung bis zum naechsten Kurzschluss undefiniert mit einem kontinuierlichen Energieeintrag weiter. Aus dem dabei unkontrollierten Aufschmelzen der Elektrodenspitze resultieren stochastische Prozessschwankungen. Dagegen folgt beim neuen ChopArc-Verfahren einem gesteuerten Aufschmelzen des Elektrodendrahtes in der Brennphase mit definierter Abschaltung des Lichtbogens eine Unterbrechungsphase ohne Energieeintrag bis zum naechsten Kurzschlusseintritt. Mit dem ChopArc ist es nun moeglich, sowohl eine zaehe Schmelze fuer Duennblech-, Wurzel- oder Zwangslagenschweissen, als auch eine niedrige Schmelzbadviskositaet fuer eine gute Kapillarwirkung des Lotes beim MAG-Loeten zu erzielen. (orig.)

  13. Application of planar laser-induced fluorescence measurement techniques to study the heat transfer characteristics of parallel-plate heat exchangers in thermoacoustic devices

    International Nuclear Information System (INIS)

    This paper describes the development of an experimental arrangement and the application of acetone-based planar laser-induced fluorescence (PLIF) measurement techniques to study the unsteady characteristics of heat transfer processes in the parallel-plate heat exchangers of thermoacoustic devices. The experimental rig is a quarter-wavelength acoustic resonator where a standing wave imposes oscillatory flow conditions. Two mock-up heat exchangers, 'hot' and 'cold', have their fins kept at constant temperatures by electrical heating and water cooling, respectively. A purpose-designed acetone tracer seeding mechanism is used for PLIF temperature measurement. Acetone concentration is optimized from the viewpoint of PLIF signal intensity. Two-dimensional temperature distributions in the gas surrounding the heat exchanger plates, as a function of phase angle in the acoustic cycle, are obtained. Local and global (instantaneous and cycle-averaged) heat flux values on the fin surface are estimated and used to obtain the dependence of the space-cycle averaged Nusselt versus Reynolds number. Measurement uncertainties are discussed

  14. Rapid Fabrication of Flat Plate Cavity Phosphor Thermography Test Models for Shuttle Return-to-Flight Aero-Heating

    Science.gov (United States)

    Buck, Gregory M.; Powers, Michael A.; Nevins, Stephen C.; Griffith, Mark S.; Wainwright, Gary A.

    2006-01-01

    Methods, materials and equipment are documented for fabricating flat plate test models at NASA Langley Research Center for Shuttle return-to-flight aeroheating experiments simulating open and closed cavity interactions in Langley s hypersonic 20-Inch Mach 6 air wind tunnel. Approximately 96 silica ceramic flat plate cavity phosphor thermography test models have been fabricated using these methods. On one model, an additional slot is machined through the back of the plate and into the cavity and vented into an evacuated plenum chamber to simulate a further opening in the cavity. After sintering ceramic to 2150 F, and mounting support hardware, a ceramic-based two-color thermographic phosphor coating is applied for global temperature and heat transfer measurements, with fiducial markings for image registration.

  15. Synthesis and characterization of Ni-Mo filler brazing alloy for Mo-W joining for microwave tube technology

    Directory of Open Access Journals (Sweden)

    Frank Ferrer Sene

    2013-04-01

    Full Text Available A brazing process based on Ni-Mo alloy was developed to join porous tungsten cathode bottom and dense molybdenum cathode body for microwave tubes manufacture. The Ni-Mo alloy was obtained by mixing and milling powders in the eutectic composition, and applied on the surface of the components. The brazing was made at 1400 °C by using induction heating in hydrogen for 5 minutes. Alumina surfaces were coated with the binder and analyzed by Energy Dispersive X-rays Fluorescence. The brazed samples were analyzed by Scanning Electron Microscopy coupled to Energy Dispersive Spectroscopy. Stress-strain tests were performed to determine the mechanical behavior of the joining. The quality of the brazing was evaluated by assuring the presence of a "meniscus" formed by the Ni-Mo alloy on the border of the tungsten and molybdenum joint, the absence of microstructural defects in the interface between the tungsten and molybdenum alloys, and the adhesion of the brazed components.

  16. A New Vacuum Brazing Route for Niobium-316L Stainless Steel Transition Joints for Superconducting RF Cavities

    Science.gov (United States)

    Kumar, Abhay; Ganesh, P.; Kaul, R.; Bhatnagar, V. K.; Yedle, K.; Ram Sankar, P.; Sindal, B. K.; Kumar, K. V. A. N. P. S.; Singh, M. K.; Rai, S. K.; Bose, A.; Veerbhadraiah, T.; Ramteke, S.; Sridhar, R.; Mundra, G.; Joshi, S. C.; Kukreja, L. M.

    2015-02-01

    The paper describes a new approach for vacuum brazing of niobium-316L stainless steel transition joints for application in superconducting radiofrequency cavities. The study exploited good wettability of titanium-activated silver-base brazing alloy (CuSil-ABA®), along with nickel as a diffusion barrier, to suppress brittle Fe-Nb intermetallic formation, which is well reported during the established vacuum brazing practice using pure copper filler. The brazed specimens displayed no brittle intermetallic layers on any of its interfaces, but instead carried well-distributed intermetallic particles in the ductile matrix. The transition joints displayed room temperature tensile and shear strengths of 122-143 MPa and 80-113 MPa, respectively. The joints not only exhibited required hermeticity (helium leak rate ultra-high vacuum but also withstood twelve hour degassing heat treatment at 873 K (suppresses Q-disease in niobium cavities), without any noticeable degradation in the microstructure and the hermeticity. The joints retained their leak tightness even after undergoing ten thermal cycles between the room temperature and the liquid nitrogen temperature, thereby establishing their ability to withstand service-induced low cycle fatigue conditions. The study proposes a new lower temperature brazing route to form niobium-316L stainless steel transition joints, with improved microstructural characteristics and acceptable hermeticity and mechanical properties.

  17. Properties of active-brazed HPSN-steel joints

    Energy Technology Data Exchange (ETDEWEB)

    Wippel, V. [Technische Univ., Graz (Austria). Abt. fuer Werkstoffe und Schweisstechnik; Holzner, G. [Technische Univ., Graz (Austria). Abt. fuer Werkstoffe und Schweisstechnik; Cerjak, H. [Technische Univ., Graz (Austria). Abt. fuer Werkstoffe und Schweisstechnik

    1995-12-31

    In this paper, the creation of very strong HPSN-ceramic compounds with HPSN and steel by active-brazing is described. The brazin-partners are hot-pressed silicon-nitride (HPSN) and the metallic part is the martensite steel X23 CrNi17. As active-braze commercially available silver and silver-copper brazes were used. (orig./MM)

  18. Brazing of sensors for high-temperature steam instrumentation systems

    International Nuclear Information System (INIS)

    Procedures are developed for brazing a ceramic-to-metal seal and for laser welding of sensor subassemblies into tube walls, induction brazing thermocouples through a tube wall, and furnace brazing triaxial cables, thermocouples, and a vent tube to a guide tube study three-dimensional phenomena in the upper plenum and core of a pressurized water reactor during the reflood stage of a loss-of-coolant accident. 8 refs

  19. Unsteady MHD convection and mass transfer flow of micropolar fluids past a vertical permeable moving plate with heat absorption

    International Nuclear Information System (INIS)

    By the use of the theory of micropolar fluids due to Eringen, perturbation method is presented to study an unsteady MHD convection and mass transfer flow of micropolar fluids past a vertical permeable moving plate with heat absorption. The plate moves with a constant velocity in the direction of fluid flow, while the free stream velocity follows an exponentially increasing or decreasing small perturbation law. Approximate solutions of the coupled nonlinear governing equations are obtained for different values of microrotation and magnetic parameters. Numerical calculations are carried out for the various parameters entering into the problem. The results of velocity, angular velocity, temperature and concentration profiles have been presented graphically for various values of the material parameters. The results indicate that the micropolar fluids display a reduction in drag as well as heat transfer rate when compared with Newtonian fluids. (author)

  20. MHD Free Convective Boundary Layer Flow of a Nanofluid past a Flat Vertical Plate with Newtonian Heating Boundary Condition

    OpenAIRE

    Uddin, Mohammed J.; Khan, Waqar A.; Ahmed I Ismail

    2012-01-01

    Steady two dimensional MHD laminar free convective boundary layer flows of an electrically conducting Newtonian nanofluid over a solid stationary vertical plate in a quiescent fluid taking into account the Newtonian heating boundary condition is investigated numerically. A magnetic field can be used to control the motion of an electrically conducting fluid in micro/nano scale systems used for transportation of fluid. The transport equations along with the boundary conditions are first convert...

  1. Experimental Study of Inducing Compressive Stress by Anti-welding Heating Treatment in a Thin Plate Weldment with Variant Temperatures

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Significant compressive stress may be induced in thin plate weldment by anti-welding heating treatment (AWHT)with a temperature difference above 350℃, and an interesting phenomenon of obvious residual stress reduction on non-treated surface was discovered. The method of AWHT has no great effect on the mechanical properties including hardness, strength and toughness of the metal material. The results in the paper prompt a possibility application in shipbuilding industry.

  2. Ultrasonic testing of the depth of penetration of electron beam welds on heat exchanger tubes to tube plate assemblies

    International Nuclear Information System (INIS)

    A focused beam ultrasonic testing method is described, which controls weld penetration and more precisely welded zone depth. This technique has been applied to the control of electron beam welds of tube to plate assemblies on heat exchangers; electron beam welding, interesting from economical and technical points of view, induces irregularities in weld penetration. Used as a quality control method, it allows to precisely record some welding parameters (penetration depth, compactness defects, root shape...)

  3. Unsteady Free Convection Flow past a Vertical Plate with Heat and Mass Fluxes in the Presence of Thermal Radiation

    Directory of Open Access Journals (Sweden)

    S. Das

    2015-01-01

    Full Text Available The problem of unsteady free convection flow past an infinite vertical plate with heat and mass fluxes in the presence of thermal radiation is studied. The dimensionless coupled linear partial differential equations governing the flow are solved by employing the Laplace transform technique. Exact solutions have been obtained for the fluid velocity, temperature and mass concentration for the cases of both uniform heat flux (UHF and uniform wall temperature (UWT. The numerical results for the fluid velocity, temperature and mass concentration are presented graphically for various pertinent flow parameters and discussed in detail.

  4. High heat load test of CFC divertor target plate with screw tube for JT-60 superconducting modification

    International Nuclear Information System (INIS)

    A flat carbon fiber composite (CFC) tile mock-up with screw tubes, which have helical fins like a nut, was fabricated aiming at further improvement of the heat removal performance of the cost-effectively manufactured divert or target for JT-60SC (modified JT-60 as a superconducting coil tokamak). The heat removal performance of the mock-up was successfully demonstrated on the JAERI Electron Beam Irradiation Stand. The estimated heat transfer coefficient of the screw tube at the non-boiling region was roughly three times higher than that of the smooth tube. This corresponds to 1.5 times that of the swirl tube. A heat cycle test of 10 MW/m2 showed that the mock-up with the screw tubes could withstand for 1400-cycles. These results indicate that the divertor target plate with the flat CFC tile and the screw tube can be a promising candidate for the JT-60SC divertor target

  5. Study the Micropolar Fluid Flow near the Stagnation on a Vertical Plate with Prescribed Wall Heat Flux

    Directory of Open Access Journals (Sweden)

    Gitima Patowary

    2011-11-01

    Full Text Available This paper investigates the influence of the material parameter, buoyancy parameter and Prandtl number on the skin friction coefficient and the heat transfer rate at the surface on a steady, two dimensional flow of an incompressible micropolar fluid near the stagnation point on a vertical plate with prescribed surface heat flux in presence of a magnetic filed. The free stream velocity and the surface heat flux are assumed to be proportional to the distance from the stagnation point. Similarly transformation is employed to transform the governing partial differential equations to a set of ordinary differential equations. The effects of the material parameter, buoyancy parameter and Prandtl number on the skin friction coefficient and the heat transfer rate at the surface are discussed and the corresponding velocity, temperature and microrotation profiles are shown graphically. Both assisting and opposing flows are considered and it is found that dual solutions exist for both cases

  6. Near-field radiative heat transfer between two parallel SiO2 plates with and without microcavities

    International Nuclear Information System (INIS)

    Near-to-far-field radiative heat transfer between two macroscopic SiO2 plates—with and without microcavities—was observed using a highly precise and accurate optical gap-measurement method. The experiments, conducted near 300 K, measured heat transfer as a function of gap separation from 1.0 μm to 50 μm and also as a function of temperature differences between 4.1 and 19.5 K. The gap-dependent heat flux was in excellent agreement with theoretical predictions. Furthermore, the effects of microcavities on the plate surfaces were clearly observed and significant enhancement of near-field radiative heat transfer was confirmed between gold-coated microcavities with narrow vacuum separation

  7. Irreversibility analysis for optimization design of plate fin heat exchangers using a multi-objective cuckoo search algorithm

    International Nuclear Information System (INIS)

    Highlights: • The first application of IMOCS for plate-fin heat exchanger design. • Irreversibility degrees of heat transfer and fluid friction are minimized. • Trade-off of efficiency, total cost and pumping power is achieved. • Both EGM and EDM methods have been compared in the optimization of PFHE. • This study has superiority over other single-objective optimization design. - Abstract: This paper introduces and applies an improved multi-objective cuckoo search (IMOCS) algorithm, a novel met-heuristic optimization algorithm based on cuckoo breeding behavior, for the multi-objective optimization design of plate-fin heat exchangers (PFHEs). A modified irreversibility degree of the PFHE is separated into heat transfer and fluid friction irreversibility degrees which are adopted as two initial objective functions to be minimized simultaneously for narrowing the search scope of the design. The maximization efficiency, minimization of pumping power, and total annual cost are considered final objective functions. Results obtained from a two dimensional normalized Pareto-optimal frontier clearly demonstrate the trade-off between heat transfer and fluid friction irreversibility. Moreover, a three dimensional Pareto-optimal frontier reveals a relationship between efficiency, total annual cost, and pumping power in the PFHE design. Three examples presented here further demonstrate that the presented method is able to obtain optimum solutions with higher accuracy, lower irreversibility, and fewer iterations as compared to the previous methods and single-objective design approaches

  8. Efficiently-cooled plasmonic amorphous silicon solar cells integrated with a nano-coated heat-pipe plate

    Science.gov (United States)

    Zhang, Yinan; Du, Yanping; Shum, Clifford; Cai, Boyuan; Le, Nam Cao Hoai; Chen, Xi; Duck, Benjamin; Fell, Christopher; Zhu, Yonggang; Gu, Min

    2016-04-01

    Solar photovoltaics (PV) are emerging as a major alternative energy source. The cost of PV electricity depends on the efficiency of conversion of light to electricity. Despite of steady growth in the efficiency for several decades, little has been achieved to reduce the impact of real-world operating temperatures on this efficiency. Here we demonstrate a highly efficient cooling solution to the recently emerging high performance plasmonic solar cell technology by integrating an advanced nano-coated heat-pipe plate. This thermal cooling technology, efficient for both summer and winter time, demonstrates the heat transportation capability up to ten times higher than those of the metal plate and the conventional wickless heat-pipe plates. The reduction in temperature rise of the plasmonic solar cells operating under one sun condition can be as high as 46%, leading to an approximate 56% recovery in efficiency, which dramatically increases the energy yield of the plasmonic solar cells. This newly-developed, thermally-managed plasmonic solar cell device significantly extends the application scope of PV for highly efficient solar energy conversion.

  9. Efficiently-cooled plasmonic amorphous silicon solar cells integrated with a nano-coated heat-pipe plate.

    Science.gov (United States)

    Zhang, Yinan; Du, Yanping; Shum, Clifford; Cai, Boyuan; Le, Nam Cao Hoai; Chen, Xi; Duck, Benjamin; Fell, Christopher; Zhu, Yonggang; Gu, Min

    2016-01-01

    Solar photovoltaics (PV) are emerging as a major alternative energy source. The cost of PV electricity depends on the efficiency of conversion of light to electricity. Despite of steady growth in the efficiency for several decades, little has been achieved to reduce the impact of real-world operating temperatures on this efficiency. Here we demonstrate a highly efficient cooling solution to the recently emerging high performance plasmonic solar cell technology by integrating an advanced nano-coated heat-pipe plate. This thermal cooling technology, efficient for both summer and winter time, demonstrates the heat transportation capability up to ten times higher than those of the metal plate and the conventional wickless heat-pipe plates. The reduction in temperature rise of the plasmonic solar cells operating under one sun condition can be as high as 46%, leading to an approximate 56% recovery in efficiency, which dramatically increases the energy yield of the plasmonic solar cells. This newly-developed, thermally-managed plasmonic solar cell device significantly extends the application scope of PV for highly efficient solar energy conversion. PMID:27113558

  10. Enhancement of shell side forced convective heat transfer on the shell-tube type heat exchanger using thin plate-type supports

    International Nuclear Information System (INIS)

    The shell side heat transfer and pressure drop to water flowing counter were experimentally investigated on the basis of the overall heat transfer coefficient. The investigation was intended to identify ways to get higher performance for the cooler in a BWR nuclear power plant. The following three conclusions were reached in the study. (1) From estimated performance of the heat exchanger using the overall heat transfer coefficient based on the outside area of the tube K0, performance of this heat exchanger was enhanced 92% as compared with the measured performance of the conventional segmental heat exchanger. Assuming that the fouling factor is Rf = 8.6 x 10-2 m2K/kW, the former was enhanced about 23%. (2) The tube side pressure drop ΔPt = 20 kPa and the shell side pressure drop ΔPs = 70 kPa were obtained, and they were within the allowable value ΔPa = 80 kPa. The shell side pressure drop of the standard spacer could be decreased 20% as compared with that of the low pressure drop spacer. (3) The enhancement constant of heat transfer of the low pressure drop spacer with thin plate-type supports was about 1.2 times as large as that of the standard spacer. The heat exchanger with the low pressure drop spacer was about 1.6 times more compact than that using the standard spacer. (author)

  11. MHD free convective boundary layer flow of a nanofluid past a flat vertical plate with Newtonian heating boundary condition.

    Science.gov (United States)

    Uddin, Mohammed J; Khan, Waqar A; Ismail, Ahmed I

    2012-01-01

    Steady two dimensional MHD laminar free convective boundary layer flows of an electrically conducting Newtonian nanofluid over a solid stationary vertical plate in a quiescent fluid taking into account the Newtonian heating boundary condition is investigated numerically. A magnetic field can be used to control the motion of an electrically conducting fluid in micro/nano scale systems used for transportation of fluid. The transport equations along with the boundary conditions are first converted into dimensionless form and then using linear group of transformations, the similarity governing equations are developed. The transformed equations are solved numerically using the Runge-Kutta-Fehlberg fourth-fifth order method with shooting technique. The effects of different controlling parameters, namely, Lewis number, Prandtl number, buoyancy ratio, thermophoresis, Brownian motion, magnetic field and Newtonian heating on the flow and heat transfer are investigated. The numerical results for the dimensionless axial velocity, temperature and nanoparticle volume fraction as well as the reduced Nusselt and Sherwood number have been presented graphically and discussed. It is found that the rate of heat and mass transfer increase as Newtonian heating parameter increases. The dimensionless velocity and temperature distributions increase with the increase of Newtonian heating parameter. The results of the reduced heat transfer rate is compared for convective heating boundary condition and found an excellent agreement. PMID:23166688

  12. MHD free convective boundary layer flow of a nanofluid past a flat vertical plate with Newtonian heating boundary condition.

    Directory of Open Access Journals (Sweden)

    Mohammed J Uddin

    Full Text Available Steady two dimensional MHD laminar free convective boundary layer flows of an electrically conducting Newtonian nanofluid over a solid stationary vertical plate in a quiescent fluid taking into account the Newtonian heating boundary condition is investigated numerically. A magnetic field can be used to control the motion of an electrically conducting fluid in micro/nano scale systems used for transportation of fluid. The transport equations along with the boundary conditions are first converted into dimensionless form and then using linear group of transformations, the similarity governing equations are developed. The transformed equations are solved numerically using the Runge-Kutta-Fehlberg fourth-fifth order method with shooting technique. The effects of different controlling parameters, namely, Lewis number, Prandtl number, buoyancy ratio, thermophoresis, Brownian motion, magnetic field and Newtonian heating on the flow and heat transfer are investigated. The numerical results for the dimensionless axial velocity, temperature and nanoparticle volume fraction as well as the reduced Nusselt and Sherwood number have been presented graphically and discussed. It is found that the rate of heat and mass transfer increase as Newtonian heating parameter increases. The dimensionless velocity and temperature distributions increase with the increase of Newtonian heating parameter. The results of the reduced heat transfer rate is compared for convective heating boundary condition and found an excellent agreement.

  13. Chapter 11. Heat Exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Rafferty, Kevin D.; Culver, Gene

    1998-01-01

    Most geothermal fluids, because of their elevated temperature, contain a variety of dissolved chemicals. These chemicals are frequently corrosive toward standard materials of construction. As a result, it is advisable in most cases to isolate the geothermal fluid from the process to which heat is being transferred. The task of heat transfer from the geothermal fluid to a closed process loop is most often handled by a plate heat exchanger. The two most common types used in geothermal applications are: bolted and brazed. For smaller systems, in geothermal resource areas of a specific character, downhole heat exchangers (DHEs) provide a unique means of heat extraction. These devices eliminate the requirement for physical removal of fluid from the well. For this reason, DHE-based systems avoid entirely the environmental and practical problems associated with fluid disposal. Shell and tube heat exchangers play only a minor role in low-temperature, direct-use systems. These units have been in common use in industrial applications for many years and, as a result, are well understood. For these reasons, shell and tube heat exchangers will not be covered in this chapter.

  14. Performance of the coupling of the flat plate collector and a heat pump system associated with a vertical heat exchanger for heating of the two types of greenhouses system

    International Nuclear Information System (INIS)

    Highlights: • Two greenhouses coupled with a heat pump system and a flat plate collector associated with a vertical heat exchanger have been simulated. • A control function in the level of heat pump was examined. • Temporal evolution of the temperature and the energy for 48 h operation in January have been evaluated. • The system gives good results in all operating states. - Abstract: The renewable energy resources appear to be the most effective solution to energy increasing demand. In particular the consumption of energy in greenhouses in Tunisia country has gained an increasing interest. The objective of this work is the heating of the two types of greenhouses (with surface area 100 m2) by using the different installations. The heat pump (water/air) system is coupled with a flat plate collector (with surface area 2 m2) and a vertical heat exchanger in order to obtain a comfortable climate in the winter in the greenhouses. The system is subdivides into three parts; (i) the conversion of the solar energy on the thermal energy in the level of the flat plate collector; (ii) increasing this energy at the level of the heat pumps system; (iii) heating the greenhouses by using this abundant and universal source of energy. Here, we present a mathematical description of the heat pump as well as the numerical results of the simulation of the system, such as the coefficient of performance, the outlet temperature in the level of the flat plate collector and in the heat pump system, the temperature and the energy indoor the greenhouse, finally a good results are obtained comparing with others similar results in research area

  15. Three-dimensional analysis and numerical optimization of combined natural convection and radiation heat loss in solar cavity receiver with plate fins insert

    International Nuclear Information System (INIS)

    Highlights: • The use of plate fins to suppress combined heat loss in the cavity receiver is presented. • 3D numerical model with non-Boussinesq steady-state combined heat transfer is presented. • The geometric parameters considered were optimized. • Natural convection heat loss reduced by 20% and radiation heat loss by 5%. • The overall thermal efficiency of the cavity receiver is also presented. - Abstract: The numerical study and optimization of combined laminar natural convection and surface radiation heat transfer in solar cavity receiver with plate fins is presented in this paper. Minimizing heat loss in cavity receivers is seen as an effective way to enhance the thermal performance and the use of plate fins has been proposed as a low cost means to minimize heat loss. Firstly, the influence of operating temperature, emissivity of the surface, orientation and the geometric parameters on the total heat loss from the receiver was investigated. It was observed that convective heat loss is largely affected by the angle of inclination of the receiver, the presence of fins and the number of fins in the receiver. As for the radiation heat loss it was observed that it is mainly influenced by the properties of the cavity receiver surface. The radiation heat loss was found to be constant at all the angles of the receiver. Significant reduction in natural convection heat loss from the cavity receiver was accomplished by using the plate fins whereas radiation heat loss was marginally reduced by about 5%. Secondly, the optimization was conducted to obtain the optimal fin geometry and lastly, the overall thermal efficiency of the receiver was presented at different operating temperatures. The overall cavity efficiency marginally increased by approximately 2% with the insertion of fin plates although the convective heat loss was suppressed by about 20%. This is due to the fact that radiation heat loss dominates at high operating temperatures compared to convective

  16. Heating produced by therapeutic ultrasound in the presence of a metal plate in the femur of canine cadavers

    Directory of Open Access Journals (Sweden)

    A.O. Andrades

    2014-10-01

    Full Text Available The present study aimed to assess the heat generated by a therapeutic ultrasound (TUS in a metal bone plate and adjacent structures after fixation to the femur of canine cadavers. Ten pairs of hind limbs were used, and they were equally distributed between groups that were subjected to 1- and 3-MHz frequencies, with each frequency testing 1- and 2-W/cm² intensities. The right hind limb was defined as the control group (absence of the metal plate, and the left hind limb was the test group (presence of the metal plate. Therefore, the control groups (CG were denominated CGI, using TUS with 1-MHz frequency and 1-W/cm² intensity; CGII, using 1-MHz frequency and 2-W/cm² intensity; CGIII, using 3-MHz frequency and 1-W/cm² intensity; and CGIV, using 3-MHz frequency and 2-W/cm² intensity. For each control group, its respective test group (TG was denominated TGI, TGII, TGIII and TGIV. The TUS was applied to the lateral aspect of the thigh using the continuous mode and a 3.5-cm² transducer in a 6.25-cm² area for 2 minutes. Sensors were coupled to digital thermometers that measured the temperature in different sites before (t0 and after (t1 of the TUS application. The temperatures in t1 were higher in all tested groups. The intramuscular temperature was significantly higher (P<0.05 in the groups used to test the 3-MHz frequency in the presence of the metal plate. The therapeutic ultrasound in the continuous mode using frequencies of 1 and 3 MHz and intensities of 1 and 2 W/cm2 for 2 minutes caused heating of the metal plate and adjacent structures after fixation to the femur of canine cadavers.

  17. Study on alumina-alumina brazing for application in vacuum chambers of proton synchrotron

    International Nuclear Information System (INIS)

    The paper describes an experimental study to standardize vacuum brazing process to obtain satisfactory high purity alumina brazed joints for application in rapid cycle proton synchrotron machine. Two different brazing routes, adopted for making alumina-alumina brazed joints, included (i) multi-step Mo-Mn metallization and brazing with BVAg-8 alloy and (ii) advanced single-step active brazing with CuSil-ABA alloy. Brazed alumina specimens, prepared by both the routes, yielded ultra high vacuum compatible, helium leak tight and bakeable joints. Active-brazed specimens exhibited satisfactory strength values in tensile and four-point bend tests. Metallized-brazed specimens, although exhibited relatively lower tensile strength than the targeted value, displayed satisfactory flexural strength in four-point bend test. The results of the study demonstrated that active brazing is the simple and cost effective alternative to conventional metallization route for producing satisfactory brazed joints for application in rapid cycle proton synchrotron machine. (author)

  18. Numerical analysis of fin-tube plate heat exchanger by using CFD technique

    OpenAIRE

    Ahmed F. Khudheyer; Mahmoud Sh. Mahmoud

    2011-01-01

    Three-dimensional CFD simulations are carried out to investigate heat transfer and fluid flow characteristics of a two-row plain fin-and-tube heat exchanger using Open FOAM, an open-source CFD code. Heat transfer and pressure drop characteristics of the heat exchanger are investigated for Reynolds numbers ranging from 330 to 7000. Model geometry is created, meshed, calculated, and post-processed using open source software. Fluid flow and heat transfer are simulated and results compared using ...

  19. Characteristics of dissimilar laser-brazed joints of isotropic graphite to WC-Co alloy

    Energy Technology Data Exchange (ETDEWEB)

    Nagatsuka, Kimiaki, E-mail: nagatuka@jwri.osaka-u.ac.jp [Graduate School of Engineering, Osaka University, Joining and Welding Research Institute, 11-1, Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Sechi, Yoshihisa, E-mail: sechi@kagoshima-it.go.jp [Kagoshima Prefectural Institute of Industrial Technology, 1445-1 Oda, Hayato-cho, Kirishima, Kagoshima 899-5105 (Japan); Miyamoto, Yoshinari, E-mail: y_miyamoto@toyotanso.co.jp [Toyo Tanso Co., Ltd., 5-7-12 Takeshima, Nishiyodgawa-ku, Osaka 555-0011 (Japan); Nakata, Kazuhiro, E-mail: nakata@jwri.osaka-u.ac.jp [Joining and Welding Research Institute, Osaka University, 11-1, Mihogaoka, Ibaraki, Osaka 567-0047 (Japan)

    2012-04-25

    Highlights: Black-Right-Pointing-Pointer Ti was required in the filler metal for brazing graphite to WC-Co alloy. Black-Right-Pointing-Pointer The shear strength of the joint increased with Ti content up to 1.7 mass%. Black-Right-Pointing-Pointer Ti concentrated at the interface of graphite/filler metal. Black-Right-Pointing-Pointer TiC was formed at the interface of graphite/filler metal. - Abstract: The effect of Ti serving as an activator in a eutectic Ag-Cu alloy filler metal in dissimilar laser-brazed joints of isotropic graphite and a WC-Co alloy on the joint strength and the interface structure of the joint is investigated in this study. To evaluate the joint characteristics, the Ti content in the filler metal was increased from 0 to 2.8 mass%. The laser brazing was carried out by irradiating a laser beam selectively on the WC-Co alloy plate in Ar atmosphere. The threshold content of Ti required to join isotropic graphite to WC-Co alloy was 0.4 mass%. The shear strength at the brazed joint increased rapidly with increasing Ti content up to 1.7 mass%, and a higher Ti content was found to be likely to saturate the shear strength to a constant value of about 14 MPa. The isotropic graphite blocks also fractured at this content. The concentration of Ti observed at the interface between isotropic graphite and the filler metal indicates the formation of an intermetallic layer of TiC.

  20. Heat transfer in smooth tubes, between parallel plates, along a semi-infinite plate, in annular spaces and along tube bundles for exponential distribution of the heat flux in forced, laminar or turbulent flow

    International Nuclear Information System (INIS)

    By introducing an additional parameter F0, the processes known hitherto for calculating heat transfer are extended to the heat flux distributions following an exponential law qw = exp(mx) which give a heat transfer coefficient, independent of position for laminar and turbulent flow with a linear pressure drop. For laminar flow along a semi-infinite plate, the heat flux distribution in accordance with the law qw = xm leads to the Nusselt number, regardless of the position. Nu is then determined by the thickness of the thermal boundary layer. For the annular space, the equations for explicit calculation of the temperature field will be given, as well as the Nusselt number in laminar flow and constant heat flux. In turbulent flow, the laws of distribution of eddy diffusivity for momentum in a tube, established by H. Reichardt, adapted for the annular space and the tube bundle, give the velocity field and the coefficient of friction and thus permit solution of the heat transfer equations. The results of the numerical calculation are given in the tables and diagrams for an extended range of the various parameters and compared with the experimental results. A simple process to determine the lower limit of the thermal entry length will be described. (author)

  1. Mechanical and microstructural behavior of brazed aluminum / stainless steel mixed joints

    Science.gov (United States)

    Fedorov, V.; Weis, S.; Wagner, G.

    2016-03-01

    There is a requirement to combine different materials such as aluminum and stainless steel in industrial applications like automotive heat exchangers. Brazing offers the possibility to reduce the joining temperature in comparison to welding due to the lower liquidus temperature of the fillers. In the present work, the mechanical and microstructural behavior of aluminum / stainless steel mixed joints is investigated. The specimens are produced by induction brazing using an AlSi10filler and a non-corrosive flux. To evaluate the mechanical properties of the joints, tensile tests at elevated temperatures are carried out. Additionally, long-term thermal exposure experiments are done in order to investigate the changes in the microstructure.

  2. Cause and countermeasure for heat up of HTTR core support plate at power rise tests

    International Nuclear Information System (INIS)

    HTTR has carried out many kinds of tests as power rise tests in which reactor power rises step by step after attained the first criticality. In the tests, temperature of a core support plate reached higher than expected at each power level, the temperature was expected to be higher than the maximum working temperature at 100% power level. Therefore, tests under the high temperature test operation mode, in which the core flow rate was different, were carried out to predict the temperature at 100% power precisely, and investigate the cause of the temperature rise. From the investigation, it was clear that the cause was gap flow in the core support structure. Furthermore, it was estimated that the temperature of the core support plate rose locally due to change in gap width between the core support plate and a seal plate due to change in core pressure drop. The maximum working temperature of the core support plate was revised. The integrity of core support plate under the revised maximum working temperature condition was confirmed by stress analyses. (author)

  3. Direct Numerical Simulation of Transitional and Turbulent Flow Over a Heated Flat Plate Using Finite-Difference Schemes

    Science.gov (United States)

    Madavan, Nateri K.

    1995-01-01

    The work in this report was conducted at NASA Ames Research Center during the period from August 1993 to January 1995 deals with the direct numerical simulation of transitional and turbulent flow at low Mach numbers using high-order-accurate finite-difference techniques. A computation of transition to turbulence of the spatially-evolving boundary layer on a heated flat plate in the presence of relatively high freestream turbulence was performed. The geometry and flow conditions were chosen to match earlier experiments. The development of the momentum and thermal boundary layers was documented. Velocity and temperature profiles, as well as distributions of skin friction, surface heat transfer rate, Reynolds shear stress, and turbulent heat flux were shown to compare well with experiment. The numerical method used here can be applied to complex geometries in a straightforward manner.

  4. The effect of ambient air condition on heat transfer of hot steel plate cooled by an impinging water jet

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Pil Jong; Choi, Hae Won [Research Institute of Industrial Science and Technology, Pohang (Korea, Republic of); Lee, Sung Hong [Busan National Univ., Busan (Korea, Republic of)

    2003-05-01

    It has been observed that the cooling capacity of an impinging water jet is affected by the seasonal conditions in large-scale steel manufacturing processes. To confirm this phenomenon, cooling experiments utilizing a hot steel plate cooled by a laminar jet were conducted for two initial ambient air temperatures (10 .deg. C and 40 .deg. C) in a closed chamber, performing an inverse heat conduction method for quantitative comparison. This study reveals that the cooling capacity at an air temperature of 10 .deg. C is lower than the hear extracted at 40 .deg. C. The amount of total extracted heat at 10 .deg. C is 15% less than at 40 .deg. C. These results indicate the quantity of water vapor, absorbed until saturation, affects the mechanism of boiling heat transfer.

  5. Reactive Boride Brazing on Low-Alloy Automotive Grade Steel

    Science.gov (United States)

    Palanisamy, B.; Upadhyaya, A.

    2011-11-01

    Brazing is a widely used process to improve the performance of steels used in automotive applications. The substrate material is often exposed to harsh conditions in these applications and may affect the service life of the component. Reactive boride brazing aims to improve the mechanical properties of the substrate material by forming a ceramic-metal composite coating in a single-step process in situ. In this study, sintered Ancor 4300 low-alloy steel is used as the substrate with chromium-rich braze and chromium-lean braze materials. The mechanical properties of the brazed samples were studied in detail using microindentation hardness measurements and the transverse rupture test. The results indicate that the brazed superlayer has a 10 times higher hardness. There was a significant improvement in the transverse rupture strength of the steel brazed with the chromium-rich boride as compared to the pure substrate material. In an effort to reduce processing time, green compacts of the substrate were also directly brazed and yielded favorable results.

  6. Failure Assessment Diagram for Brazed 304 Stainless Steel Joints

    Science.gov (United States)

    Flom, Yory

    2011-01-01

    Interaction equations were proposed earlier to predict failure in Albemet 162 brazed joints. Present study demonstrates that the same interaction equations can be used for lower bound estimate of the failure criterion in 304 stainless steel joints brazed with silver-based filler metals as well as for construction of the Failure Assessment Diagrams (FAD).

  7. Copper phosphorus brazing for copper tubing. Dohaikan no rindo rozuke

    Energy Technology Data Exchange (ETDEWEB)

    Kanai, A. (Industrial Research Institute of Kanagawa Prefecture, Kanagawa (Japan))

    1993-04-01

    This paper explains copper phosphorus torch brazing for copper tubing used in construction facilities as the main object of discussion. Copper phosphorus brazing requires no flux in brazing copper with copper and copper with bronze because of self-fluxing action of phosphorus. Jointing steel tubing with copper tubing is impossible. Brazing is possible even at temperatures below the liquid-phase line where good beads can be obtained. It allows larger tolerance for clearance than soldering and silver brazing. In the working process, the final clean surface turns to bright copper while producing flux, Cu3P, slag and gas P2O5. According to void prediction based on the relation of clearance between a copper tube and a joint with capillary rising height, a brazed joint without a defect can be obtained if the nominal diameter is 32A or less. Six kinds of copper phosphorus brazing fillers are specified in JIS, the best filler being BCuP-3. The suitable temperature for brazing is in high temperature zones of about 800[degree]C, but a work is performed preferably while watching fillet being formed at about 700[degree]C. The minimum required penetration depth should be twice as much as the steel tube wall thickness, while the minimum bonding area should be quadruple as much. 10 figs., 1 tab.

  8. Mechanisms of stabilization and blowoff of a premixed flame downstream of a heat-conducting perforated plate

    KAUST Repository

    Kedia, Kushal S.

    2012-03-01

    The objective of this work is to investigate the flame stabilization mechanism and the conditions leading to the blowoff of a laminar premixed flame anchored downstream of a heat-conducting perforated-plate/multi-hole burner, with overall nearly adiabatic conditions. We use unsteady, fully resolved, two-dimensional simulations with detailed chemical kinetics and species transport for methane-air combustion. Results show a bell-shaped flame stabilizing above the burner plate hole, with a U-shaped section anchored between neighboring holes. The base of the positively curved U-shaped section of the flame is positioned near the stagnation point, at a location where the flame displacement speed is equal to the flow speed. This location is determined by the combined effect of heat loss and flame stretch on the flame displacement speed. As the mass flow rate of the reactants is increased, the flame displacement speed at this location varies non-monotonically. As the inlet velocity is increased, the recirculation zone grows slowly, the flame moves downstream, and the heat loss to the burner decreases, strengthening the flame and increasing its displacement speed. As the inlet velocity is raised, the stagnation point moves downstream, and the flame length grows to accommodate the reactants mass flow. Concomitantly, the radius of curvature of the flame base decreases until it reaches an almost constant value, comparable to the flame thickness. While the heat loss decreases, the higher flame curvature dominates thereby reducing the displacement speed of the flame base. For a stable flame, the gradient of the flame base displacement speed normal to the flame is higher than the gradient of the flow speed along the same direction, leading to dynamic stability. As inlet velocity is raised further, the former decreases while the latter increases until the stability condition is violated, leading to blowoff. The flame speed during blow off is determined by the feedback between the

  9. Mechanical characterization and modeling of brazed tungsten and Cu–Cr–Zr alloy using stress relief interlayers

    International Nuclear Information System (INIS)

    A rapidly solidified foil-type Ti–Zr based amorphous filler with a melting temperature of 850 °C was used to braze tungsten to Cu–Cr–Zr alloy for water cooled divertors and plasma facing components application. Brazed joints of dissimilar materials suffer from a mismatch in coefficients of thermal expansion. In order to release the residual stress caused by the mismatch, brazed joints of tungsten and Cu–Cr–Zr alloy using different interlayers were studied. The shear strength tests of brazed W/Cu joints show that the average strength of the joint with a W70Cu30 composite plate interlayer reached 119.8 MPa, and the average strength of the joint with oxygen free high conductivity copper (OFHC Cu)/Mo multi-interlayers reached 140.8 MPa, while the joint without interlayer was only 16.6 MPa. Finite element method (FEM) has been performed to investigate the stress distribution and effect of stress relief interlayers. FEM results show that the maximum von Mises stress occurs in the tungsten/filler interface and that the filler suffers the peak residual stresses and becomes the weakest zone. And the use of OFHC Cu/Mo multi-interlayers can reduce the residual stress significantly, which agrees with the mechanical experiment data

  10. Heat Treating of Heavy Truck Plate Spring%重型汽车钢板弹簧的热处理

    Institute of Scientific and Technical Information of China (English)

    武明亮; 范铁岁; 宋桂军

    2013-01-01

    研究了代替52 CrMnBA钢用于重型汽车少片钢板弹簧的50 CrV钢的热处理工艺。研究结果表明,50 CrV钢板弹簧用PAG水溶性淬火介质淬火可明显提高淬透性和硬度均匀性;弹簧总成的疲劳寿命大于12万次,符合技术要求。道路试验表明,采用50 CrV钢制造的重型汽车少片钢板弹簧性能完全满足使用要求,且成本明显降低。%The heat treating process of leaf-minimum plate spring of 50CrV steel instead of 52CrMnBA steel for heavy truck was investigared .The results reveal that the hardenability and hardness uniformity of 50 CrV steel plate spring may be significantly increased by quenching in a PAG aqueous solution , and that the fatigue life of plate spring assembly is as long as over 120 000 cycles , conforming with the technical requirement .Furthermore , the road test shows that the 50 CrV steel leaf-minimum plate spring for heavy truck has satisfactory performance , and is more low in production cost .

  11. Experimental study of an ammonia-water bubble absorber using a plate heat exchanger for absorption refrigeration machines

    International Nuclear Information System (INIS)

    The development of absorption chillers activated by renewable heat sources has increased due mainly to the increase in primary energy consumption that causes problems such as greenhouse gases and air pollution among others. These machines, which could be a good substitute for compression systems, could be used in the residential and food sectors which require a great variety of refrigeration conditions. Nevertheless, the low efficiency of these machines makes it necessary to enhance heat and mass transfer processes in the critical components, mainly the absorber, in order to reduce their large size. This study used ammonia-water as the working fluid to look at how absorption takes place in a plate heat exchanger operating under typical conditions of absorption chillers, driven by low temperature heat sources. Experiments were carried out using a corrugated plate heat exchanger model NB51, with three channels, where ammonia vapor was injected in bubble mode into the solution in the central channel. The results achieved for the absorption flux were in the range of 0.0025-0.0063 kg m-2 s-1, the solution heat transfer coefficient varied between 2.7 and 5.4 kW m-2 K-1, the absorber thermal load from 0.5 to 1.3 kW. In addition, the effect of the absorber operating conditions on the most significant efficiency parameters was analyzed. The increase in pressure, solution and cooling flow rates positively affect the absorber performance, on the other hand an increase in the concentration, cooling, and solution temperature negatively affects the absorber performance

  12. Influence of Variable Permeability and Radiation Absorption on Heat and Mass Transfer in MHD Micropolar Flow over a Vertical Moving Porous Plate

    OpenAIRE

    Harish Babu, D.; P.V. Satya Narayana

    2013-01-01

    An analysis of unsteady free convection with heat and mass transfer flow for a micropolar fluid through a porous medium with a variable permeability bounded by a semi-infinite vertical plate in the presence of heat generation, thermal radiation, first-order chemical reaction, and the radiation absorption is reported. The plate is assumed to move with a constant velocity in the direction of fluid flow. A uniform magnetic field acts perpendicular to the porous surface which absorbs micropolar f...

  13. Thermal and hydraulic analysis of 3-stream multi fluid (He/He/N2) plate fin heat exchanger for helium plant

    International Nuclear Information System (INIS)

    One of the key components of helium refrigerator/liquefier (HRL) plant is heat exchangers working at cryogenic temperature. For some cases, heat exchangers with effectiveness less than 90% can be a reason for failure of helium plant to produce liquid helium. To achieve such high effectiveness, it is necessary to use plate fin heat exchangers, which provides very high heat transfer surface area per unit volume. For the heat exchangers of HRL, high effectiveness, compact volume and low pressure drop are main optimizing parameters. The first heat exchanger whose temperature range is ∼310 K to ∼90 K is analysed with plate-fin type heat exchanger. This heat exchanger is a part of indigenous development work of HRL of ∼2 kW cooling capacity at 4.5 Kat IPR. Liquid nitrogen (LN2) is used to cool incoming hot He gas around ∼80 K. The detailed thermal and hydraulic analysis is discussed in this paper. (author)

  14. Experimental and numerical analyses on a plate heat exchanger with phase change for waste heat recovery at off-design conditions

    Science.gov (United States)

    Cipollone, Roberto; Bianchi, Giuseppe; Di Battista, Davide; Fatigati, Fabio

    2015-11-01

    This paper analyzes the performances of an evaporator for small scale waste heat recovery applications based on bottoming Organic Rankine Cycles with net output power in the range 2-5 kW. The heat recovery steam generator is a plate heat exchanger with oil as hot stream and an organic fluid on the cold side. An experimental characterization of the heat exchanger was carried out at different operating points measuring temperatures, pressures and flow rates on both sides. The measurement data further allowed to validate a numerical model of the evaporator whereas heat transfer coefficients were evaluated comparing several literature correlations, especially for the phase-change of the organic fluid. With reference to a waste heat recovery application in industrial compressed air systems, multiple off-design conditions were simulated considering the effects of oil mass flow rate and temperature on the superheating of the organic fluid, a key parameter to ensure a proper operation of the expansion machine, thus of the energy recovery process.

  15. CFD Analysis of Plate Fin Tube Heat Exchanger for Various Fin Inclinations

    OpenAIRE

    Subodh Bahirat,; P. V. Joshi

    2014-01-01

    ANSYS Fluent software is used for three dimensional CFD simulations to investigate heat transfer and fluid flow characteristics of six different fin angles with plain fin tube heat exchangers. The numerical simulation of the fin tube heat exchanger was performed by using a three dimensional numerical computation technique. Geometry of model is created and meshed by using ANSYS Workbench software. To solve the equation for the fluid flow and heat transfer analysis ANSYS FLUENT ...

  16. Joining Characteristics of Intermediate Heat Exchanger Candidate Materials in Very High Temperature Reactor(VHTR)

    International Nuclear Information System (INIS)

    Worldwide studies have shown an increasing need for energy with the use of all energy sources, ranging from renewable sources through nuclear power, gas, to a limited extent oil and finally to the most prolific fossil fuel, coal. Although this increased need for generation capacity can met with different fuel sources, maybe the main fuel worldwide for next generation is hydrogen. The very high temperature reactor(VHTR) can produce hydrogen from only heat and water by using thermochemical iodine-sulfur(I-S) process or from heat, water, and natural gas by applying the steam reformer technology to core outlet temperatures greater than about 950 .deg. C. An intermediate heat exchanger(IHX) is the component in which the heat from the primary circuit helium is transferred to the secondary circuit helium(about 950 .deg. at 1000psi), thus keeping the secondary circuit free of radioactive contamination. The IHX will be located with a pressure vessel within the reactor containment that will be attached to the reactor pressure vessel by the cross-vessel. Therefore, an intermediate heat exchanger(IHX) especially is a key component in a VHTR. The Status of the IHX design will probably be a compact, counter-flow heat exchanger design consisting of metallic plate construction with small channels etched into each plate and assembled into a module. This heat exchanger design is refereed to as a 'printed circuit heat exchanger'. Printed circuit type heat exchanger are constructed from flat metal plates into which fluid flow channels are chemically milled. The milled plates are stacked and diffusion bonded together. In this study, the effects of the brazing temperature and homogenizing time for brazed specimens on the joint and base material microstructures, elemental distribution within the microstructures and the resulting joint tensile strength and micro hardness of Ni-based superalloy such as Haynes 230 were investigated

  17. Experimental and analytical studies of high heat flux components for fusion experimental reactor

    International Nuclear Information System (INIS)

    In this report, the experimental and analytical results concerning the development of plasma facing components of ITER are described. With respect to developing high heat removal structures for the divertor plates, an externally-finned swirl tube was developed based on the results of critical heat flux (CHF) experiments on various tube structures. As the result, the burnout heat flux, which also indicates incident CHF, of 41 ± 1 MW/m2 was achieved in the externally-finned swirl tube. The applicability of existing CHF correlations based on uniform heating conditions was evaluated by comparing the CHF experimental data with the smooth and the externally-finned tubes under one-sided heating condition. As the results, experimentally determined CHF data for straight tube show good agreement, for the externally-finned tube, no existing correlations are available for prediction of the CHF. With respect to the evaluation of the bonds between carbon-based material and heat sink metal, results of brazing tests were compared with the analytical results by three dimensional model with temperature-dependent thermal and mechanical properties. Analytical results showed that residual stresses from brazing can be estimated by the analytical three directional stress values instead of the equivalent stress value applied. In the analytical study on the separatrix sweeping for effectively reducing surface heat fluxes on the divertor plate, thermal response of the divertor plate has been analyzed under ITER relevant heat flux conditions and has been tested. As the result, it has been demonstrated that application of the sweeping technique is very effective for improvement in the power handling capability of the divertor plate and that the divertor mock-up has withstood a large number of additional cyclic heat loads. (J.P.N.) 62 refs

  18. Near-Field Radiative Heat Transfer Between Metasurfaces: A Full-Wave Study Based on 2D Grooved Metal Plates

    CERN Document Server

    Dai, Jin; Bozhevolnyi, Sergey I; Yan, Min

    2016-01-01

    Metamaterials possess artificial bulk and surface electromagnetic states. Tamed dispersion properties of surface waves allow one to achieve controllable super-Planckian radiative heat transfer (RHT) process between two closely spaced objects. We numerically demonstrate enhanced RHT between two 2D grooved metal plates by a full-wave scattering approach. The enhancement originates from both transverse magnetic spoof surface plasmon polaritons and a series of transverse electric bonding- and anti-bonding waveguide modes at surfaces. The RHT spectrum is frequency-selective, and highly geometrically tailorable. Our simulation also reveals thermally excited non-resonant surface waves in constituent materials can play a prevailing role for RHT at an extremely small separation between two plates, rendering metamaterial modes insignificant for the energy transfer process.

  19. Boundary Layer Flow and Heat Transfer with Variable Fluid Properties on a Moving Flat Plate in a Parallel Free Stream

    Directory of Open Access Journals (Sweden)

    Norfifah Bachok

    2012-01-01

    Full Text Available The steady boundary layer flow and heat transfer of a viscous fluid on a moving flat plate in a parallel free stream with variable fluid properties are studied. Two special cases, namely, constant fluid properties and variable fluid viscosity, are considered. The transformed boundary layer equations are solved numerically by a finite-difference scheme known as Keller-box method. Numerical results for the flow and the thermal fields for both cases are obtained for various values of the free stream parameter and the Prandtl number. It is found that dual solutions exist for both cases when the fluid and the plate move in the opposite directions. Moreover, fluid with constant properties shows drag reduction characteristics compared to fluid with variable viscosity.

  20. The evaluation of the temperature characteristic of Bandung TRIGA 2000 reactor heat exchanger for several plate number variations by using CFD computer code

    International Nuclear Information System (INIS)

    The attached heat exchanger of Bandung TRIGA 2000 reactor is plate type with configuration single pass (one-pass/one-pass plate and frame heat exchanger). Initially this heat exchanger could support the operation of Bandung TRIGA 2000 reactor at the power of zero kW safely and continuously. However at the moment, the reactor can only be operated at low powers, due to the temperature increase of primary cooling water released from reactor tank, or the temperature increased of primary cooling water entered to the heat exchanger has came near ridge cream operation of the reactor Le. 49°C. It was due to the decrease of heat transfer effectivity from the heat exchanger, where cooling process or retrieval of heat from primary cooling water by secondary cooling water in heat exchanger did not proceed at maximum condition, so that the temperature difference between the inflow of cooling water and water outflow from heat exchanger was small. To reduce the primary cooling water temperature, technically can be done by adding number of heat exchanger plates, with aim to add heat transfer surface area in heat exchanger, so that would more amount of temperature removed from primary cooling water to secondary cooling water. At this study the characteristic of heat exchanger of Bandung TRIGA 2000 reactor at addition of number of plates and coolant flow rate was analyzed. The optimum configuration based on plates number applied and usage of primary pump and secondary pump in operating Bandung TRIGA 2000 reactor safely and continuously was also determined. (author)

  1. Brazing of aluminium assemblies under nitrogen convection in a charge furnace; Brasage d'assemblages en aluminium sous convection d'azote dans un four a charge

    Energy Technology Data Exchange (ETDEWEB)

    Faure, D.; Perez, G. [BMI Fours Industriels, 38 - Saint Quentin Fallavier (France)

    2006-03-15

    The research of a weight saving has led to the use of aluminium in the automotive industry, which has been innovation instigator for a lot of industries. The brazing under vacuum of aluminium, even if it presents a lot of advantages, is inadequate to the mass production because it is too difficult for the quality of the preliminary assembly to the brazing. It is rather reserved to the advance technology industries such as the aeronautics or the power electronics. A lot of aluminium heat exchangers are mass manufactured and brazed by the Nocolok process. (O.M.)

  2. Development of the heat sink structure of a beam dump for the proton accelerator

    International Nuclear Information System (INIS)

    The beam dump is the essential component for the good beam quality and the reliable performance of the proton accelerator. The beam dump for a 20 MeV and 20 mA proton accelerator was designed and manufactured in this study. The high heats deposited, and the large amount of radioactivity produced in beam dump should be reduced by the proper heat sink structure. The heat source by the proton beam of 20 MeV and 20 mA was calculated. The radioactivity assessments of the beam dump were carried out for the economic shielding design with safety. The radioactivity by the protons and secondary neutrons in designed beam dump were calculated in this sturdy. The effective engineering design for the beam dump cooling was performed, considering the mitigation methods of the deposited heats with small angle, the power densities with the stopping ranges in the materials and the heat distributions in the beam dump. The heat sink structure of the beam dump was designed to meet the accelerator characteristics by placing two plates of 30 cm by 60 cm at an angle of 12 degree. The highest temperatures of the graphite, copper, and copper faced by cooling water were designed to be 223 degree, 146 degree, and 85 degree, respectively when the velocity of cooling water was 3 m/s. The heat sink structure was manufactured by the brazing graphite tiles to a copper plate with the filler alloy of Ti-Cu-Ag. The brazing procedure was developed. The tensile stress of the graphite was less than 75% of a maximum tensile stress during the accelerator operation based on the analysis. The safety analyses for the commissioning of the accelerator operation were also performed. The specimens from the brazed parts of beam dump structure were made to identify manufacturing problems. The soundness of the heat sink structure of the beam dump was confirmed by the fatigue tests of the brazed specimens of the graphite-copper tile components with the repetitive heating and cooling. The heat sink structure developed

  3. Transient conjugate free convection from a vertical flat plate in a porous medium subjected to a sudden change in surface heat flux

    CERN Document Server

    Shu, Jian-Jun

    2015-01-01

    The paper presents a theoretical study using the Karman-Pohlhausen method for describing the transient heat exchange between the boundary-layer free convection and a vertical flat plate embedded in a porous medium. The unsteady behavior is developed after the generation of an impulsive heat flux step at the right-hand side of the plate. Two cases are considered according to whether the plate has a finite thickness or no thickness. The time and space evolution of the interface temperature is evidenced.

  4. Study of Boundary Layer Convective Heat Transfer with Low Pressure Gradient Over a Flat Plate Via He's Homotopy Perturbation Method

    International Nuclear Information System (INIS)

    The boundary layer convective heat transfer equations with low pressure gradient over a flat plate are solved using Homotopy Perturbation Method, which is one of the semi-exact methods. The nonlinear equations of momentum and energy solved simultaneously via Homotopy Perturbation Method are in good agreement with results obtained from numerical methods. Using this method, a general equation in terms of Pr number and pressure gradient (λ) is derived which can be used to investigate velocity and temperature profiles in the boundary layer.

  5. Application of He's homotopy perturbation method to boundary layer flow and convection heat transfer over a flat plate

    Science.gov (United States)

    Esmaeilpour, M.; Ganji, D. D.

    2007-12-01

    In this Letter, the problem of forced convection over a horizontal flat plate is presented and the homotopy perturbation method (HPM) is employed to compute an approximation to the solution of the system of nonlinear differential equations governing on the problem. It has been attempted to show the capabilities and wide-range applications of the homotopy perturbation method in comparison with the previous ones in solving heat transfer problems. The obtained solutions, in comparison with the exact solutions admit a remarkable accuracy. A clear conclusion can be drawn from the numerical results that the HPM provides highly accurate numerical solutions for nonlinear differential equations.

  6. Brazing of 14-5 PH steel and Fe - TiC composite using AWS BNi2 filler metal

    Directory of Open Access Journals (Sweden)

    J. Nowacki

    2007-01-01

    Full Text Available Purpose: Purpose of this paper is description of influence of the parameters of the 14-5 PH steel and cermets - PMFe-TiC composite plates brazing using nickel based brazing filler metal BNi2 structure and properties of joints.Design/methodology/approach: Brazing was done in vacuum according to a special thermal cycle programme.Metallographic, X Ray analysis, microanalysis, hardness and tensile strength, as well quality investigations ofproduced joints have been done.Findings: It was shown that The joint has a eutectic multilayer structure with a zone of intermetallic compoundsin the steel – soldier and soldier – PM Fe-TiC composite - Ferro – Titanit plates boundary. Intermetalliccompounds zone differ clearly on account of a chemical composition, microstructure, and hardness from abrazing filler metal matrix.Research limitations/implications: It was shown that the diffusive zone from the PM Fe-TiC composite side isrich in titanium, molybdenum and iron, in the joint axis there is a zone rich in silicon, and in a boundary fillermetal – steel rich in iron and nickel. In the rich in nickel and iron filler metal matrix, there are intermetallicphases rich in chromium, which consist several percent of nickel, iron and molybdenum. The diffusive zonesare characterized by hardness higher than the filler metal matrix.Practical implications: As a result of conducted experiments a production of spinning nozzle of a die forpolyethylene granulation with a vacuum-brazed with a PM Fe-TiC composite plates cutting surface have beenworked out and applied in industry.Originality/value: An original value of the paper is to prove the propensity of concentration gradients ofalloying components and intermetallic phases creation.

  7. Preliminary design review package on air flat plate collector for solar heating and cooling system

    Science.gov (United States)

    1977-01-01

    Guidelines to be used in the development and fabrication of a prototype air flat plate collector subsystem containing 320 square feet (10-4 ft x 8 ft panels) of collector area are presented. Topics discussed include: (1) verification plan; (2) thermal analysis; (3) safety hazard analysis; (4) drawing list; (5) special handling, installation and maintenance tools; (6) structural analysis; and (7) selected drawings.

  8. Free Convection Flow and Heat Transfer of Tangent Hyperbolic past a Vertical Porous Plate with Partial Slip

    Directory of Open Access Journals (Sweden)

    V. Ramachandra Prasad

    2016-01-01

    Full Text Available This article presents the nonlinear free convection boundary layer flow and heat transfer of an incompressible Tangent Hyperbolic non-Newtonian fluid from a vertical porous plate with velocity slip and thermal jump effects. The transformed conservation equations are solved numerically subject to physically appropriate boundary conditions using a second-order accurate implicit finite-difference Keller Box technique. The numerical code is validated with previous studies. The influence of a number of emerging non-dimensional parameters, namely the Weissenberg number (We, the power law index (n, Velocity slip (Sf, Thermal jump (ST, Prandtl number (Pr and dimensionless tangential coordinate ( on velocity and temperature evolution in the boundary layer regime are examined in detail. Furthermore, the effects of these parameters on surface heat transfer rate and local skin friction are also investigated. Validation with earlier Newtonian studies is presented and excellent correlation achieved. It is found that velocity, skin friction and heat transfer rate (Nusselt number is increased with increasing Weissenberg number (We, whereas the temperature is decreased. Increasing power law index (n enhances velocity and heat transfer rate but decreases temperature and skin friction. An increase in Thermal jump (ST is observed to decrease velocity, temperature, local skin friction and Nusselt number. Increasing Velocity slip (Sf is observed to increase velocity and heat transfer rate but decreases temperature and local skin friction. An increasing Prandtl number, (Pr, is found to decrease both velocity and temperature. The study is relevant to chemical materials processing applications.

  9. Vacuum brazing of OFE Copper-316L stainless steel transition joints without electroplating stainless steel part for application in particle accelerators

    International Nuclear Information System (INIS)

    Brazed transition Joints between OFE copper and type 316L austenitic stainless steel (SS) find extensive applications in particle accelerators all over the world. In contrast to excellent wettability of OFE copper, austenitic SS is well known for its poor wettability for BVAg-8 (72Ag/28Cu; melting point: 1052 K) braze filler metal (BFM). High surface wettability is believed to be necessary to drag molten BFM into the capillary gap between mating metallic surfaces. Therefore, the widely accepted practice for vacuum brazing of such transition joints involves electroplating of SS parts with nickel or copper to enhance its wettability. A recently concluded in-house study, involving Nb to Ni-plated 316L SS brazing, has demonstrated that satisfactory ingress of BFM into a capillary joint between two dissimilar metals is possible if the poor wettability of one of the mating surfaces is compensated by good wettability of its counterpart. In the light of these observations, the present study was undertaken to explicitly evaluate the requirement of electroplating the SS part for establishment of sound OFE copper-316L SS brazed joints suitable for service in ultra-high vacuum (UHV) of particle accelerators

  10. Preparation of W/CuCrZr monoblock test mock-up using vacuum brazing technique

    International Nuclear Information System (INIS)

    Development of the joining for W/CuCrZr monoblock PFC test mock-up is an interest area in Fusion R and D. W/Cu bimetallic material has prepared using OFHC copper casting approach on the radial surface of W monoblock tile surface. The W/Cu bimetallic material has been joined with CuCrZr tube (heat sink) material with the vacuum brazing route. Vacuum brazing of W/Cu-CuCrZr has been performed @ 970 °C for 10 mins using NiCuMn-37 filler material under deep vacuum environment (10-6 mbar). Graphite fixtures were used for OFHC copper casting and vacuum brazing experiments. The joint integrity of W/Cu-CuCrZr monoblock mock-up on W/Cu and Cu-CuCrZr has been checked using ultrasonic immersion technique. Micro-structural examination and Spot-wise elemental analysis have been carried out using HR-SEM and EDAX. The results of the experimental work will be discussed in the paper. (author)

  11. Unsteady Hydromagnetic Natural Convection Flow past an Impulsively Moving Vertical Plate with Newtonian Heating in a Rotating System

    Directory of Open Access Journals (Sweden)

    Gauri Shanker Seth

    2015-01-01

    Full Text Available An investigation of unsteady hydromagnetic natural convection flow of a viscous, incompressible, electrically conducting and heat absorbing fluid past an impulsively moving vertical plate with Newtonian heating embedded in a porous medium in a rotating system is carried out. The governing partial differential equations are first subjected to Laplace transformation and then inverted numerically using INVLAP routine of Matlab. The governing partial differential equations are also solved numerically by Crank-Nicolson implicit finite difference scheme and a comparison has been provided between the two solutions. The numerical solution for fluid velocity and fluid temperature are depicted graphically whereas the numerical values of skin friction and Nusselt number are presented in tabular form for various values of pertinent flow parameters. Present solution in special case is compared with previously obtained solution and is found to be in excellent agreement.

  12. Natural convection flow of a nano-fluid over a vertical plate with uniform surface heat flux

    Energy Technology Data Exchange (ETDEWEB)

    Khan, W.A. [Department of Engineering Sciences, National University of Sciences and Technology, Karachi 75350 (Pakistan); Aziz, A. [Department of Mechanical Engineering, School of Engineering and Applied Science, Gonzaga University, Spokane, WA 99258 (United States)

    2011-07-15

    Natural convective flow of a nano-fluid over a vertical plate with a constant surface heat flux is investigated numerically, following a similarity analysis of the transport equations. The transport model employed includes the effect of Brownian motion and thermophoresis. The analysis shows that velocity, temperature and concentration profiles in the respective boundary layers depend, besides the Prandtl and Lewis numbers, on three additional dimensionless parameters, namely a Brownian motion parameter Nb, a thermophoresis parameter Nt, a buoyancy ratio parameter Nr. In addition to the study of these parameters on the boundary layer flow characteristics (velocity, temperature, nano-particle concentration, skin friction, and heat transfer), correlations for the Nusselt and Sherwood numbers have been developed based on a regression analysis of the data. These correlations predict the numerical results with a maximum error of 5.5% for the reduced Nusselt number and 3.2% for the reduced Sherwood number. (authors)

  13. Turbulent combined-convection boundary layer with aiding flows along a heated vertical flat plate at higher freestream velocity

    Science.gov (United States)

    Abedina, Mohammad Zoynal; Islam, Mohammed Moinul; Hanif, Md. Abu; Alam, Md. Jahangir

    2016-07-01

    A numerical investigation is performed in the turbulent combined-convection boundary layer with aiding flows in air along a heated vertical flat plate at a higher freestream velocity (Reδ0 = 600) by time-developing direct numerical simulation (DNS). At higher freestream velocity, the transition from laminar to turbulent delays for aiding flows and relatively a lower and higher heat transfer rates are observed, respectively, in the laminar and turbulent region compared to that of lower freestream velocity. The wall shear stresses are higher in the laminar region compared to that in the turbulent region, and at higher freestream velocity, the wall shear stress in the transition region shows a higher peak value. The intensity of velocity and temperature fluctuations for aiding flows with higher freestream velocity become appreciably lower than that for lower freestream velocity due to the laminarization of the boundary layer.

  14. 46 CFR 57.06-2 - Production test plate interval of testing.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Production test plate interval of testing. 57.06-2 Section 57.06-2 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING WELDING AND BRAZING Production Tests § 57.06-2 Production test plate interval of testing. (a) At least one set of production test plates shall be...

  15. CFD Analysis of Plate Fin Tube Heat Exchanger for Various Fin Inclinations

    Directory of Open Access Journals (Sweden)

    Subodh Bahirat,

    2014-08-01

    Full Text Available ANSYS Fluent software is used for three dimensional CFD simulations to investigate heat transfer and fluid flow characteristics of six different fin angles with plain fin tube heat exchangers. The numerical simulation of the fin tube heat exchanger was performed by using a three dimensional numerical computation technique. Geometry of model is created and meshed by using ANSYS Workbench software. To solve the equation for the fluid flow and heat transfer analysis ANSYS FLUENT was used in the fin-tube heat exchanger. The fluid flow and heat transfer are simulated and result compared for both laminar and turbulent flow models k-epsilon and SST k-omega, with steady state solvers to calculate heat transfer, flow velocity and temperature fields of variable inclined fin angles (Ɵ = 00 ,100 , 200 , 300 , 400 ,500 . Model is validate by comparing the simulated value of velocity, temperature and colburn factor with experimental and numerical results investigated by WANG [1] and GHORI KIRAR [10]. Reasonable agreement is found between the simulations and other results, and the ANSYS Fluent software is sufficient for simulating the flow fields in tube fin heat exchanger.

  16. Analysis of Cooling and Heating of Water with Flat-plate Solar Radiators

    OpenAIRE

    Balen, Igor; Soldo, Vladimir; Kennedy, David

    2003-01-01

    Extensive analysis of flat-plate radiative panels operation using average hourly weather data for a maritime climate region was performed. The panels are integrated in the space ventilation system with air-cooling by means of a cold-water coil. Their primary function is to prepare sufficient quantity of cold water, integrating radiative and convective cooling, that is collected in the cold-water tank during the nighttime operation. That cold water is used for cooling of the air during daytime...

  17. Evaluation of target-plate heat flux for a possible snowflake divertor in CFETR using SOLPS

    Energy Technology Data Exchange (ETDEWEB)

    Mao, S.F., E-mail: sfmao@ustc.edu.cn [School of Nuclear Science and Technology, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); Guo, Y.; Peng, X.B.; Luo, Z.P. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Xiao, B.J.; Song, Y.T. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); School of Nuclear Science and Technology, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); Yao, D.M.; Zhu, S.Z. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Ye, M.Y., E-mail: yemy@ustc.edu.cn [School of Nuclear Science and Technology, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China)

    2015-08-15

    China Fusion Engineering Test Reactor (CFETR) is proposed as a good complement to ITER for demonstration of fusion energy. CFETR is based on both physics and some technologies of ITER. The main goals of CFETR are fusion power P{sub f} = 50–200 MW, duty cycle time ⩾0.3–0.5, and a tritium breeding ratio ∼1.2. To explore a more effective way to manage heat exhaust in a future fusion reactor, which will have higher heating power (auxiliary heating power plus 20% of the fusion power) than ITER, a snowflake divertor (SFD) is an optional choice considered for CFETR. In this paper, the preliminary design of a SFD for CFETR is presented, including the divertor magnetic configuration and geometry. A numerical simulation is then performed to evaluate the heat flux onto the divertor targets by using SOLPS.

  18. Convective Heat Transfer Enhancement of a Rectangular Flat Plate by an Impinging Jet in Cross Flow

    Institute of Scientific and Technical Information of China (English)

    李国能; 郑友取; 胡桂林; 张治国

    2014-01-01

    Experiments were carried out to study the heat transfer performance of an impinging jet in a cross flow. Several parameters including the jet-to-cross-flow mass ratio (X=2%-8%), the Reynolds number (Red=1434-5735) and the jet diameter (d=2-4 mm) were explored. The heat transfer enhancement factor was found to increase with the jet-to-cross-flow mass ratio and the Reynolds number, but decrease with the jet diameter when other parameters maintain fixed. The presence of a cross flow was observed to degrade the heat transfer performance in respect to the effect of impinging jet to the target surface only. In addition, an impinging jet was confirmed to be capable of en-hancing the heat transfer process in considerable amplitude even though the jet was not designed to impinge on the target surface.

  19. Numerical Study of Thermal and Flow Characteristics of Plate-Fin Heat Sink with Longitudinal Vortex Generator Installed on the Ground

    Directory of Open Access Journals (Sweden)

    Yen-Tso Chang

    2014-01-01

    Full Text Available This study applied the commercial software ANSYS CFD (FLUENT, for simulating the transient flow field and investigating the influence of each parameter of longitudinal vortex generators (LVGs on the thermal flux of a plate-fin heat sink. Vortex generator was set in front of plate-fin heat sink and under the channel, which was in common-flow-down (CFD and common-flow-up (CFU conditions, which have the result of vortex generator of delta winglet pair (DWP. In this study the parameters were varied, such as the minimum transverse distance between winglet pair, the attack angle of the vortex generator, fins number, the fin height, and the distance between the vortex generator and plate-fin. The coolant fluid flew into the fin-to-fin channel and pushed the vortex from different geometry toward the bottom. This phenomenon took off the heat from the plate to enhance the heat transfer. The numerical results indicated that the LVGs located close to the plate-fin heat sink are zero with the attack angle being 30°, presenting optimal overall conditions.

  20. Technical production problems in the rolling and welding of pipes in tube plates of heat exchangers

    International Nuclear Information System (INIS)

    One of the chief problems of apparatus construction is the sealing of different pressure chambers from one another. Methods for fixing pipes in tube plates are presented. The non-positive sealing connection by rolling processes is now being increasingly replaced by a variety of welding processes, in step with new developments taking place in welding technology. Using a number of examples, some of which are taken from nuclear technology, welding procedures, demands placed on the seam, quality assurance, planning and surveillance, control measures and destructive testing are described. (orig./IHOE)

  1. Comparison of brazed joints made with BNi-1 and BNi-7 nickel-base brazing alloys

    Directory of Open Access Journals (Sweden)

    Zorc, Borut

    2000-04-01

    Full Text Available Kinetics of the processes are different with different types of brazing alloys. Precipitation processes in the parent metal close to the brazing gap are of great importance. They control the mechanical properties of the joint area when the brittle eutectic has disappeared from the gap. A comparative study of brazed joints on austenitic stainless alloys made with BNi-7 (Ni-P type and BNi-1 (Ni-Si-B type brazing alloys was made. Brazing alloys containing phosphorus behave in a different manner to those containing boron.

    Las aleaciones de níquel se producen mediante tres sistemas de aleación: Ni-P, Ni-Si y Ni-B. Durante las reacciones metalúrgicas con el metal de base, la eutéctica frágil en la separación soldada puede transformarse en la solución dúctil-sólida con todas aleaciones. La cinética del proceso varía según el tipo de aleación. Los procesos de precipitación en el metal de base cerca de la separación soldada son de mucha importancia, ya que controlan las propiedades mecánicas de la área de unión después de desaparecer la eutéctica frágil de la separación. Se ha hecho un análisis comparativo de uniones soldadas en aleaciones austeníticas inoxidables realizadas con aleaciones BNi-7 (tipo Ni-P y BNi-1 (tipo Ni-Si-B. Las aleaciones que contienen fósforo se comportan de una manera diferente, tanto con el cambio de la eutéctica a la solución sólida, como con los procesos de precipitación en el metal de base cerca de la unión soldada.

  2. Boundry Layer Flow and Heat Transfer along an Infinite Porous Hot Horizontal Continuous Moving Plate By Means Of the Natural Transformation Method

    OpenAIRE

    Surendra Kumar Agarwal; Anuj Kumar Jhankal

    2016-01-01

    An analysis is made for the two-dimensional laminar boundary layer flow of a viscous, incompressible fluid,along an infinite porous hot horizontal continuous moving plate. The governing system of partial differential equations was transformed into ordinary differential equations before being solve by Natural transformation. The effects of various physical parameters, such as Eckert number Ec , Prandtlnumber Pr , plate velocity α and heat source/sink parameter Sare present...

  3. Improved Assembly for Gas Shielding During Welding or Brazing

    Science.gov (United States)

    Gradl, Paul; Baker, Kevin; Weeks, Jack

    2009-01-01

    An improved assembly for inert-gas shielding of a metallic joint is designed to be useable during any of a variety of both laser-based and traditional welding and brazing processes. The basic purpose of this assembly or of a typical prior related assembly is to channel the flow of a chemically inert gas to a joint to prevent environmental contamination of the joint during the welding or brazing process and, if required, to accelerate cooling upon completion of the process.

  4. Comparative performance of rippled fin plate fin and tube heat exchangers

    International Nuclear Information System (INIS)

    Continuous rippled fins are preferred to interrupted fins in applications where fouling by fibrous matter or insects is a problem. The performance characteristic of three rippled fin heat exchangers have been measured in a thermal wind tunnel. The results of these measurements are reported and comparisons are made wtih published data on similar surfaces. The performance evaluation criteria used as the basis for the comparisons were those recommened by Shah (1978). The tested rippled fin surfaces were found to have a higher performance than a similar surface reported in Kay and London (1984). The heat transfer enhancement was found to be dependent upon the profile of the fin

  5. Experimental Research on Flow Maldistribution in Plate-Fin Heat Exchangers

    Institute of Scientific and Technical Information of China (English)

    张哲; 厉彦忠; 许箐

    2004-01-01

    The flow maldistribution and the effect of different inlet configuration on the flow distribution in platefin heat exchangers were studied experimentally. It is found that the flow maldistribution is serious because of the defects of inlet configurations, while the inlet configuration and Reynolds number are the main factors affecting the flow distribution. The improved inlet configurations, which are the header with a two-stage distributing configuration and the guide vane with a fluid complementary cavity were proposed and tested in this paper. The experimental results show that the improved inlet configurations can effectively improve the performance of flow distribution in heat exchangers.

  6. Corrosion Behavior of Aluminum-Steel Weld-Brazing Joint

    Science.gov (United States)

    Shi, Yu; Li, Jie; Zhang, Gang; Huang, Jiankang; Gu, Yufen

    2016-05-01

    Dissimilar metals of 1060 aluminum and galvanized steel were joined with a lap joint by pulsed double-electrode gas metal arc weld brazing with aluminum-magnesium and aluminum-silicon filler metals. The corrosion behavior of the weld joints was investigated with immersion corrosion and electrochemical corrosion tests, and the corrosion morphology of the joints was analyzed with scanning electron microscopy (SEM). Galvanic corrosion was found to occur when the samples were immersed in corrosive media, and the corrosion rate of joints was increased with increased heat input of the workpiece. Comparison of the corrosion properties of weld joints with different filler wires indicated that the corrosion rate of weld joints with aluminum-silicon filler wire was larger than that of weld joints with aluminum-magnesium filler wire. Results also showed that the zinc-rich zone of weld joints was prone to corrosion. The corrosion behavior of zinc-rich zone was analyzed with SEM equipped with an energy-dispersive x-ray spectroscopy analysis system based on the test results.

  7. Corrosion Behavior of Aluminum-Steel Weld-Brazing Joint

    Science.gov (United States)

    Shi, Yu; Li, Jie; Zhang, Gang; Huang, Jiankang; Gu, Yufen

    2016-03-01

    Dissimilar metals of 1060 aluminum and galvanized steel were joined with a lap joint by pulsed double-electrode gas metal arc weld brazing with aluminum-magnesium and aluminum-silicon filler metals. The corrosion behavior of the weld joints was investigated with immersion corrosion and electrochemical corrosion tests, and the corrosion morphology of the joints was analyzed with scanning electron microscopy (SEM). Galvanic corrosion was found to occur when the samples were immersed in corrosive media, and the corrosion rate of joints was increased with increased heat input of the workpiece. Comparison of the corrosion properties of weld joints with different filler wires indicated that the corrosion rate of weld joints with aluminum-silicon filler wire was larger than that of weld joints with aluminum-magnesium filler wire. Results also showed that the zinc-rich zone of weld joints was prone to corrosion. The corrosion behavior of zinc-rich zone was analyzed with SEM equipped with an energy-dispersive x-ray spectroscopy analysis system based on the test results.

  8. Effects of adding injection–compression to rapid heat cycle molding on the structure of a light guide plate

    International Nuclear Information System (INIS)

    This study investigates the effects of adding injection–compression to rapid heat cycle molding (RHCM) (rapid heat cycle injection–compression molding (RICM)) on the physical quality and optical anisotropy of a molded light guide plate (LGP). Transcription ratio of microstructure, uniformity of part thickness and birefringence were experimentally evaluated on a 7 inch LGP of nominal thickness of 1.12 mm (including a microstructure array of 30 µm diameter and 14 µm height). The designed mold was equipped with rapid heating and compressing facilities and a microstructured nickel stamper was fabricated by UV LIGA process. In addition, to investigate the efficacy of RICM, experiments involving conventional injection molding (CIM), ICM, and RHCM were conducted in parallel with RICM using the same mold. RHCM and RICM yielded excellent transcription ratios for the microstructure, while CIM and RICM provided high thickness uniformity and low birefringence. Thus, RICM obtains high transcription ratio of microstructure, uniform thickness and low birefringence. (paper)

  9. Seismic heating signatures in the Japan Trench subduction plate-boundary fault zone: evidence from a preliminary rock magnetic `geothermometer'

    Science.gov (United States)

    Yang, Tao; Dekkers, Mark J.; Zhang, Bo

    2016-04-01

    Frictional heating during earthquake rupture reveals important information on earthquake mechanisms and energy dissipation. The amount of annealing varies widely and is, as yet, poorly constrained. Here we use magnetic susceptibility versus temperature measurements during cycling to increasingly elevated temperatures to constrain the maximum temperature a slip zone has experienced. The case study comprises sheared clay cored from the Japan Trench subduction plate-boundary fault zone (décollement), which accommodated the large slip of the 2011 Mw 9.0 Tohoku-oki earthquake. The décollement was cored during the Integrated Ocean Drilling Program (IODP) Expedition 343, the Japan Trench Fast Drilling Project (JFAST). Heating signatures with estimated maximum temperatures ranging from ˜300 to over 500 °C are determined close to the multiple slip surfaces within the décollement. Since it is impossible to tie a specific slip surface to a certain earthquake, thermal evidence for the cumulative effect of several earthquakes is unveiled. This as yet preliminary rock magnetic `geothermometer' would be a useful tool to detect seismic heating along faults that experienced medium temperature rise, a range which is difficult to assess with other approaches.

  10. Finite Difference Analysis of Radiative Free Convection Flow Past an Impulsively Started Vertical Plate with Variable Heat and Mass Flux

    Directory of Open Access Journals (Sweden)

    V. Ramachandra Prasad

    2011-01-01

    Full Text Available A numerical solution of the unsteady radiative free convection flow of an incompressible viscous fluid past an impulsively started vertical plate with variable heat and mass flux is presented here. This type of problem finds application in many technological and engineering fields such as rocket propulsion systems, spacecraft re-entry aerothermodynamics, cosmical flight aerodynamics, plasma physics, glass production and furnace engineering. The fluid is gray, absorbing-emitting but non-scattering medium and the Rosseland approximation is used to describe the radiative heat flux in the energy equation. The governing non-linear, coupled equations are solved using an implicit finite difference scheme. Numerical results for the velocity, temperature, concentration, the local and average skinfriction, the Nusselt and Sherwood number are shown graphically, for different values of Prandtl number, Schmidt number, thermal Grashof number, mass Grashof number, radiation parameter, heat flux exponent and the mass flux exponent. It is observed that, when the radiation parameter increases, the velocity and temperature decrease in the boundary layer. The local and average skin-friction increases with the increase in radiation parameter. For increasing values of radiation parameter the local as well as average Nusselt number increases.

  11. Hydromagnetic Mixed Convective Nanofluid Slip Flow past an Inclined Stretching Plate in the Presence of Internal Heat Absorption and Suction

    Directory of Open Access Journals (Sweden)

    S. P. Anjali Devi

    2016-01-01

    Full Text Available The steady two-dimensional mixed convective boundary layer flow of nanofluid over an inclined stretching plate with the effects of magnetic field, slip boundary conditions, suction and internal heat absorption have been investigated numerically. Two different types of nanoparticles, namely copper and alumina with water as the base fluid are considered. Similarity transformations are employed to transform the governing nonlinear partial differential equations into coupled non-linear ordinary differential equations. The influence of pertinent parameters such as magnetic interaction parameter, angle of inclination, volume fraction, suction parameter, velocity slip parameter, thermal jump parameter, heat absorption parameter, mixed convection parameter and Prandtl number on the flow and heat transfer characteristics are discussed. A representative set of results are displayed graphically to illustrate the issue of governing parameters on the dimensionless velocity and temperature. Numerical values of skin friction coefficient and the Nusselt number are shown in tabular form. A comparative study between the previously published work and the present results in a limiting sense reveals excellent agreement between them.

  12. Numerical Solution of Unsteady Hydromagnetic Natural Convection Flow of Heat Absorbing Fluid past an Impulsively Moving Vertical Plate with Ramped Temperature

    Directory of Open Access Journals (Sweden)

    Gauri Shanker Seth

    2013-03-01

    Full Text Available A numerical investigation of unsteady hydromagnetic natural convection flow of a viscous, incompressible, electrically conducting and heat absorbing fluid past an impulsively moving vertical plate with ramped temperature embedded a porous medium in the presence of thermal diffusion is carried out. The governing equations are solved numerically by Crank-Nicolson implicit finite difference scheme. The numerical solution for fluid velocity and fluid temperature are depicted graphically whereas the numerical values of skin friction and Nusselt number are presented in tabular form for various values of pertinent flow parameters. Natural convection flow near a ramped temperature plate is also compared with the flow near an isothermal plate.

  13. Magnetohydrodynamics effect on three-dimensional viscous incompressible flow between two horizontal parallel porous plates and heat transfer with periodic injection/suction

    Directory of Open Access Journals (Sweden)

    R. C. Chaudhary

    2004-11-01

    Full Text Available We investigate the hydromagnetic effect on viscous incompressible flow between two horizontal parallel porous flat plates with transverse sinusoidal injection of the fluid at the stationary plate and its corresponding removal by periodic suction through the plate in uniform motion. The flow becomes three dimensional due to this injection/suction velocity. Approximate solutions are obtained for the flow field, the pressure, the skin-friction, the temperature field, and the rate of heat transfer. The dependence of solution on M (Hartmann number and λ (injection/suction is investigated by the graphs and tables.

  14. Preparation of High-Density Uranium-Silicide U3Sl2-Uss: Effects of Preirradiation Heat Treatment on As-Cast Ingot Fuel Plates

    International Nuclear Information System (INIS)

    Heat treatment experiments upon U3Si2-Uss ingot have been camed out to obtain free uranium particle size improvement which is required to enhance the U-Al inter-diffusion reaction in the fuel plate meat. . Heat treatment experiments upon fuel plates containing dispersion of U3Si2-Uss in Al matrix have also been carried out to study the effect of temperature and treatment duration on the extent of inter-diffusion reaction between free uranium particle and aluminium matrix in the fuel plate meat. Both the experiments indicate that a drastic size improvement has occurred with the U3Si2 as well as free uranium particles upon heat treatment at controlled temperature between the U3Si2 peritectic and peritectoid temperatures and that the inter-diffusion reaction between free uranium and Al matrix occurs quite significantly at temperatures higher than that ordinarily used in the fabrication procedure

  15. Brazing of Stainless Steel to Yttria-Stabilized Zirconia Using Gold-Based Brazes for Solid Oxide Fuel Cell Applications

    Science.gov (United States)

    Singh, M.; Shpargel, T. P.; Asthana, R.

    2007-01-01

    Two gold-base active metal brazes (gold-ABA and gold-ABA-V) were evaluated for oxidation resistance to 850 C, and used to join yttria-stabilized zirconia (YSZ) to a corrosion-resistant ferritic stainless steel for possible use in solid oxide fuel cells. Thermogravimetric analysis and optical microscopy and scanning electron microscopy coupled with energy-dispersive spectroscopy were used to evaluate the braze oxidation behavior, and microstructure and composition of the YSZ/braze/steel joints. Both gold-ABA and gold-ABA-V exhibited nearly linear oxidation kinetics at 850 C, with gold-ABA-V showing faster oxidation than gold-ABA. Both brazes produced metallurgically sound YSZ/steel joints due to chemical interactions of Ti and V with the YSZ and steel substrates.

  16. Heat transfer analysis in a second grade fluid over and oscillating vertical plate using fractional Caputo-Fabrizio derivatives

    Science.gov (United States)

    Shah, Nehad Ali; Khan, Ilyas

    2016-07-01

    This paper presents a Caputo-Fabrizio fractional derivatives approach to the thermal analysis of a second grade fluid over an infinite oscillating vertical flat plate. Together with an oscillating boundary motion, the heat transfer is caused by the buoyancy force induced by temperature differences between the plate and the fluid. Closed form solutions of the fluid velocity and temperature are obtained by means of the Laplace transform. The solutions of ordinary second grade and Newtonian fluids corresponding to time derivatives of integer and fractional orders are obtained as particular cases of the present solutions. Numerical computations and graphical illustrations are used in order to study the effects of the Caputo-Fabrizio time-fractional parameter α, the material parameter α _2 , and the Prandtl and Grashof numbers on the velocity field. A comparison for time derivative of integer order versus fractional order is shown graphically for both Newtonian and second grade fluids. It is found that fractional fluids (second grade and Newtonian) have highest velocities. This shows that the fractional parameter enhances the fluid flow.

  17. Heat transport in turbulent Rayleigh-Benard convection: Effect of finite top- and bottom-plate conductivity

    CERN Document Server

    Brown, E; Funfschilling, D; Ahlers, G; Brown, Eric; Nikolaenko, Alexei; Funfschilling, Denis; Ahlers, Guenter

    2005-01-01

    We describe three apparatus, known as the large, medium, and small apparatus, used for high-precision measurements of the Nusselt number N as a function of the Rayleigh number R for cylindrical samples of fluid and present results illustrating the influence of the finite conductivity of the top and bottom plates on the heat transport in the fluid. We used water samples at a mean temperature of 40 degrees C (Prandtl number sigma = 4.4). The samples in the large apparatus had a diameter D of 49.69 cm and heights L = 116.33, 74.42, 50.61, and 16.52 cm. For the medium apparatus we had D = 24.81 cm, and L = 90.20 and 24.76 cm. The small apparatus contained a sample with D = 9.21 cm, and L = 9.52 cm. For each aspect ratio Gamma = D/L the data covered a range of a little over a decade of R. The maximum R = 10^12 with Nusselt numbers N = 600 was reached for Gamma = 0.43. Measurements were made with both Aluminum and Copper top and bottom plates of nominally identical size and shape. For the large and medium apparatus...

  18. Chemically Reacting Hydromagnetic Unsteady Flow of a Radiating Fluid Past a Vertical Plate with Constant Heat Flux

    Science.gov (United States)

    Makinde, Oluwole Daniel

    2012-05-01

    The combined effects of thermal radiation absorption and magnetic field on an unsteady chemically reacting convective flow past an impulsively started vertical plate is studied in the presence of a constant wall heat flux. Boundary layer equations are derived and the resulting approximate nonlinear partial differential equations are solved numerically using a semi-discretization finite difference technique. A parametric study of all parameters involved is conducted, and a representative set of numerical results for the velocity, temperature, and concentration profiles as well as the skin-friction parameter and Sherwood number are illustrated graphically to show typical trends of the solutions. Further validation with previous works is carried out and an excellent agreement is achieved.

  19. Effect of Heat Input During Disk Laser Bead-On-Plate Welding of Thermomechanically Rolled Steel on Penetration Characteristics and Porosity Formation in the Weld Metal

    OpenAIRE

    Lisiecki A.

    2016-01-01

    The paper presents a detailed analysis of the influence of heat input during laser bead-on-plate welding of 5.0 mm thick plates of S700MC steel by modern Disk laser on the mechanism of steel penetration, shape and depth of penetration, and also on tendency to weld porosity formation. Based on the investigations performed in a wide range of laser welding parameters the relationship between laser power and welding speed, thus heat input, required for full penetration was determined. Additionall...

  20. Effect of Heat Input During Disk Laser Bead-On-Plate Welding of Thermomechanically Rolled Steel on Penetration Characteristics and Porosity Formation in the Weld Metal

    Directory of Open Access Journals (Sweden)

    Lisiecki A.

    2016-03-01

    Full Text Available The paper presents a detailed analysis of the influence of heat input during laser bead-on-plate welding of 5.0 mm thick plates of S700MC steel by modern Disk laser on the mechanism of steel penetration, shape and depth of penetration, and also on tendency to weld porosity formation. Based on the investigations performed in a wide range of laser welding parameters the relationship between laser power and welding speed, thus heat input, required for full penetration was determined. Additionally the relationship between the laser welding parameters and weld quality was determined.

  1. Coeficientes de transferencia de calor experimental para el enfriamiento de licor en intercambiadores de placas//Experimental heat transfer coefficients for the liquor cooling in plate heat exchanger

    Directory of Open Access Journals (Sweden)

    Enrique Torres‐Tamayo

    2014-01-01

    Full Text Available La pérdida de eficiencia del proceso de enfriamiento del licor amoniacal, mediante el uso de intercambiadores de calor de placas, está asociada a imprecisiones en la estimación de los coeficientes de transferencia de calor y la acumulación de incrustaciones en la superficie de intercambio. El objetivo de la investigación es determinar los coeficientes de transferencia de calor y la influencia de lasincrustaciones en la pérdida de eficiencia de la instalación. Mediante un procedimiento iterativo se estableció la ecuación del número de Nusselt y su relación con el número de Reynolds y Prandtl. Se utilizó un diseño experimental multifactorial. Los resultados predicen el conocimiento de los coeficientespara el cálculo del número de Nusselt en ambos fluidos. Los valores de los coeficientes del licor amoniacal son inferiores, ello se debe a la presencia de componentes gaseosos. La ecuación obtenida muestra correspondencia con el modelo de Buonapane, el error comparativo es del 3,55 %.Palabras claves: intercambiador de calor de placas, coeficientes de transferencia de calor, eficiencia térmica.______________________________________________________________________________AbstractThe loss of efficiency of the ammonia liquor cooling process, by means of the plate heat exchanger, is associated to the incorrect estimate of the heat transfer coefficients and the accumulation of inlays in the exchange surface. The objective of the investigation is to determine the transfer coefficients and the influence of the inlays in the efficiency loss of the installation. By means of an iterative procedure was obtained the Nusselt number equation and the relationship with the Reynolds and Prandtl number, for it was used it a design experimental multifactorial. The results predict the knowledge of the coefficients forthe calculation of the Nusselt number for both fluids. The ammonia liquor coefficients values are inferior, due to the presence of gassy

  2. Numerical analysis of steady state and transient analysis of high temperature ceramic plate-fin heat exchanger

    International Nuclear Information System (INIS)

    Highlights: • Rip saw fin design is considered to be the best because it has thin fins and has higher heat transfer coefficient. • Minimum principal stress and maximum safety factor are obtained for the inverted bolt fin design. • Maximum principal stress and minimum safety factor are obtained for triangular fin design. • Thermal stress has significant impact than mechanical stress. • High principal stress is found at the startup and shutdown stage. - Abstract: In this study three-dimensional model of ceramic plate-fin high temperature heat exchanger with different fin designs and arrangements is analyzed numerically using ANSYS FLUENT and ANSYS structural module. The ability of ceramics to withstand high temperature and corrosion makes silicon carbide (SiC) suitable candidate material to be used in high temperature heat exchanger. The operating temperature of heat exchanger is 950 °C and the operating pressure is 1.5 MPa. The working fluids are helium, sulfur trioxide, sulfur dioxide, oxygen and the water vapor. Fluid flow and heat transfer analysis are carried out for steady and transient state in FLUENT. The obtained thermal and pressure load for the steady and transient state from ANSYS FLUENT are imported to ANSYS structural module to obtain the principal stress and the factor of safety. Different arrangements of rectangular fins, triangular fins, inverted bolt fins and ripsaw fins are studied. From the results it is found that the minimum stress and the maximum safety factor are obtained for inverted bolt fins. The triangular fins have the maximum principal stress and minimum factor of safety. However, the fluid flow and heat transfer analysis show inverted bolt fins and triangular fins produce higher pressure drop and friction factor. The steady state maximum principal stress is 10.08 MPa, 9.90 MPa and 11.43 MPa for straight, staggered and top and bottom ripsaw fin arrangement. The corresponding safety factors are 21.80, 21.95 and 19

  3. Heat and fluid flow properties of circular impinging jet with a low nozzle to plate spacing. Improvement by nothched nozzle; Nozzle heibankan kyori ga chiisai baai no enkei shototsu funryu no ryudo dennetsu tokusei. Kirikaki nozzle ni yoru kaizen kojo

    Energy Technology Data Exchange (ETDEWEB)

    Shakouchih, T. [Mie University, Mie (Japan). Faculty of Engineering; Matsumoto, A.; Watanabe, A.

    2000-10-25

    It is well known that as decreasing the nozzle to plate spacing considerably the heat transfer coefficient of circular impinging jet, which impinges to the plate normally, increases remarkably. At that time, the flow resistance of nozzle-plate system also increases rapidly. In this study, in order to reduce the flow resistance and to enhance the heat transfer coefficient of the circular impinging jet with a considerably low nozzle to plate spacing, a special nozzle with notches is proposed, and considerable improvement of the flow and heat transfer properties are shown. The mechanism of enhancement of the heat transfer properties is also discussed. (author)

  4. Mixed convective MHD flow of a micropolar fluid with ohmic heating, radiation and viscous dissipation over a chemically reacting porous plate subjected to a constant heat flux and concentration gradient

    OpenAIRE

    Kumar Hitesh

    2014-01-01

    In the present paper analysis of a chemically reacting mixed convection MHD micropolar flow, heat and mass transfer in porous medium with the effects of ohmic heating, radiation and viscous dissipation past an infinite vertical plate which is subjected to a constant heat flux and the concentration gradient. The non-linear coupled partial differential equations are solved numerically using an implicit finite difference scheme known as Keller-box method. The ...

  5. Mathematical Model for Fluid Flow and Heat Transfer Processes in Plate Exchanger

    Directory of Open Access Journals (Sweden)

    Cvete B. Dimitrieska

    2015-11-01

    Full Text Available Within the analytical solution of the system of equations which solve fluid flow and heat transfer processes, the elliptical and parabolic differential equations based on initial and boundary conditions is usually unfamiliar in a closed form. Numerical solution of equation system is necessarily obtained by discretization of equations. When system of equations relate to estimation of two dimensional stationary problems, the applicable method for estimation in basic two – dimensional form is recommended.

  6. Monolithic Model of Induction Heating of Thin Conductive Plate with Respecting Thermoelasticity

    Czech Academy of Sciences Publication Activity Database

    Doležel, Ivo; Kropík, P.; Ulrych, B.

    Warsaw: Polish Society of Applied Electromagnetics, 2011, s. 59-61. ISBN 83-88131-99-0. [PSAE (PTZE) SYMPOSIUM APPLIED ELECTROMAGNETISM IN MODERN TECHNOLOGIES AND INFORMATICS /21./. Lubliniec (PL), 05.06.2011-08.06.2011] R&D Projects: GA ČR(CZ) GAP102/11/0498; GA ČR GA102/09/1305 Institutional research plan: CEZ:AV0Z20570509 Keywords : induction heating * ferromagnetic disk * electric vector T-potential Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering http://www.ptze.pl/nowa/index.php?idz_do=strony%20informacyjne&id=119

  7. MHD flow and heat transfer in a rarefied gas in a rotating parallel plate channel

    International Nuclear Information System (INIS)

    An exact analysis of MHD flow of a rarefied gas in a rotating plane channel is presented for the velocity field, induced magnetic field and temperature field. Axial and transverse components of the velocity field, induced magnetic field and the function affecting the temperature field are shown on graphs. The numerical values of the axial and transverse skin-friction components, axial and transverse components of the mass flux and the function affecting the rate of heat transfer are entered in Tables. The results are discussed. (Auth.)

  8. Characterisation of Ga-coated and Ga-brazed aluminium

    Energy Technology Data Exchange (ETDEWEB)

    Ferchaud, E. [Universite de Nantes, Polytech' Nantes, Laboratoire Genie des Materiaux et Procedes Associes, Rue Christian Pauc, 44306 Nantes Cedex 3 (France); Christien, F., E-mail: frederic.christien@univ-nantes.fr [Universite de Nantes, Polytech' Nantes, Laboratoire Genie des Materiaux et Procedes Associes, Rue Christian Pauc, 44306 Nantes Cedex 3 (France); Barnier, V. [Ecole Nationale Superieure des Mines, MPI, CNRS UMR5146, Centre SMS, 158 Cours Fauriel, 42023 Saint Etienne (France); Paillard, P. [Universite de Nantes, Polytech' Nantes, Laboratoire Genie des Materiaux et Procedes Associes, Rue Christian Pauc, 44306 Nantes Cedex 3 (France)

    2012-05-15

    This work is devoted to the brazing of aluminium using liquid gallium. Gallium was deposited on aluminium samples at {approx} 50 Degree-Sign C using a liquid gallium 'polishing' technique. Brazing was undertaken for 30 min at 500 Degree-Sign C in air. EDS (Energy Dispersive X-ray Spectroscopy) and AES (Auger Electron Spectroscopy) characterisation of Ga-coated samples has shown that the Ga surface layer thickness is of ten (or a few tens of) nanometres. Furthermore, aluminium oxide layer (Al{sub 2}O{sub 3}) was shown to be 'descaled' during Ga deposition, which ensures good conditions for further brazing. Cross-section examination of Ga-coated samples shows that liquid gallium penetrates into the aluminium grain boundaries during deposition. The thickness of the grain boundary gallium film was measured using an original EDS technique and is found to be of a few tens of nanometres. The depth of gallium grain boundary penetration is about 300 {mu}m at the deposition temperature. The fracture stress of the brazed joints was measured from tensile tests and was determined to be 33 MPa. Cross-section examination of brazed joints shows that gallium has fully dissolved into the bulk and that the joint is really autogenous. - Highlights: Black-Right-Pointing-Pointer Aluminium can be brazed using liquid gallium deposited by a 'polishing' technique. Black-Right-Pointing-Pointer The aluminium oxide layer is 'descaled' during liquid Ga 'polishing' deposition. Black-Right-Pointing-Pointer EDS can be used for determination of surface and grain boundary Ga film thickness. Black-Right-Pointing-Pointer The surface and grain boundary Ga film thickness is of a few tens of nm. Black-Right-Pointing-Pointer Surface and grain boundary gallium dissolves in the bulk during brazing.

  9. Numerical Study of Solidification in a Plate Heat Exchange Device with a Zigzag Configuration Containing Multiple Phase-Change-Materials

    Directory of Open Access Journals (Sweden)

    Peilun Wang

    2016-05-01

    Full Text Available Latent heat thermal energy storage (TES plays an important role in the advocation of TES in contrast to sensible energy storage because of the large storage energy densities per unit mass/volume possible at a nearly constant thermal energy. In the current study, a heat exchange device with a zigzag configuration containing multiple phase-change-materials (m-PCMs was considered, and an experimental system was built to validate the model for a single PCM. A two-dimensional numerical model was developed using the ANSYS Fluent 14.0 software program. The energy fractions method was put forward to calculate the average Ste number and the influence of Re and Ste numbers on the discharge process were studied. The influence of phase change temperature among m-PCMs on the solidification process has also been studied. A new boundary condition was defined to determine the combined effect of the Re and Ste numbers on the discharging process. The modelling results show that for a given input power, the Ste (or Re number has a significant impact on the discharging process; however, the period value of inlet velocity has almost no impact on it. Besides, the zigzag plate with m-PCMs has a good impact on the temperature shock as “filter action” in the discharging process.

  10. A Study on the Low Temperature Brittleness by Cyclic Cooling-Heating of Low Carbon Hot Rolled Steel Plate

    International Nuclear Information System (INIS)

    The ductile-brittle transition phenomenon of low carbon steel has been investigated using the standard Charpy V-notch specimen. Dry ice and acetone were used as refrigerants. Notched specimens were cut from the hot rolled plate produced at POSCO for the Olsen impact test. The effect of cyclic cooling and heating of 0.14% carbon steel on the embrittlement was extensively examined. The ductile-brittle transition temperature was found to be approximately-30 .deg. C. The transition temperature was gradually increased as the number of cooling-heating cycles increased. On a typical V-notch fracture surface it was found that the ductile fracture surface showed a thick and fibrous structure, while the brittle fracture surface a small and light grain with irregular disposition. As expected, the transition temperature was also increased as the carbon content of steel increased. Compared with the case of 0.14% carbon steel, the transition temperature of 0.17% carbon steel was found to be increased about 12 .deg. C

  11. Study on MHD Free Convection Heat and Mass Transfer Flow past a Vertical Plate in the Presence of Hall Current

    Directory of Open Access Journals (Sweden)

    M. S. Hossain

    2014-12-01

    Full Text Available A two-dimensional MHD free convection heat and mass transfer flow of viscous, incompressible and electrically conducting fluid past a vertical flat plate embedded in porous medium in the presence of hall current under the influence of uniform magnetic field applied normal to the flow is studied analytically. In this research work, we make the governing equations dimensionless by usual non-dimensional variables and we obtained a set of ordinary differential equations. Then these obtained ordinary differential equations are solved analytically by using perturbation technique. The expressions for velocity field, temperature distribution, concentration field, skin friction, the rate of heat transfer and the rate of mass transfer are derived. Finally the results are discussed in detailed with the help of graphs and tables to observe the effect of different parameters like Magnetic parameter (M, radiation parameter (F, Grashof number (Gr, modified Grashof number (Gm, Prandtl number (Pr, permeability parameter (k, Eckert number (Ec and the chemical reaction parameter (Kc.

  12. Studies of plate bending for practical use by computer aided line-heating system; FEM wo oyoshita senjo kanetsu jidoka no jitsuyoka kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Ishiyama, M.; Tango, Y.; Nakamura, Y. [Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan)

    1998-06-01

    This paper describes studies for practical use of an automated line heating system applied with FEM. Line heating is indispensable to process curved outer plates of a ship hull, but it is difficult to learn. Automation applied with FEM is conceived. Line heating, which is a combination of heat conduction and thermal elasto-plastic phenomena, is replaced by elasticity calculation using the inherent strain as the base to make calculation possible at a practical speed. An intended shape is transformed into a flat plane by using a simulation of elastic large transformation to derive inherent strain distribution necessary for bending processing as well as the initial flat plane shape. On the other hand, transformations of each one of the heating line are combined to approximate the inherent strain distribution which provides the intended curved surface. This combination of the heating lines constitutes the heating method. A calculation method for a heating plan applied with a continuously moving heating method with high efficiency was examined for practical application. Quantitative discussion was given on factors which provide transformation and variation of elements including the residual stress, and a verification test incorporating the results therefrom was performed. It was verified that bending processing with practically sufficient accuracy is possible from results of verification tests on bowl-shaped numerically curved surfaces and outer plates on actual ships. 8 refs., 19 figs., 1 tab.

  13. The Finite Element Method Solution of an Unsteady MHD Free Convection Flow Past an Infinite Vertical Plate with Constant Suction and Heat Absorption

    OpenAIRE

    A Sri Sailam

    2014-01-01

    The study of unsteady hydro magnetic free convective flow of viscous incompressible and electrically conducting fluids past an infinite vertical porous plate in the presence of constant suction and heat absorbing sinks has been made. Appropriate solutions have been derived for the velocity and temperature fields, skin friction and rate of heat transfer using Galerkin finite element method. It is observed that increase in magnetic field strength decreases the velocity of the fl...

  14. Lie Group Method for Studying the Heat Generation Effect on Freeconvection Laminar Boundary-layer Flow Over a Vertical Flat Plate

    OpenAIRE

    Abd-el-Malek, MB; Badran, NA; Hassan, HS; Abbas, HH

    2015-01-01

    The nonlinear equations of heat and mass transfer in two-dimensional free-convection, laminar, boundary layer flow of a viscous incompressible fluid over a vertical plate with thermophoresis and heat generation effect have been considered. We apply Lie-group method for determining symmetry reductions of partial differential equations. Liegroup method starts out with a general infinitesimal group of transformations under which the given partial differential equations are inva...

  15. Quality evaluations of the fuel bundle welds and brazed joints by acoustic microscopy

    International Nuclear Information System (INIS)

    For more than 20 years, the quality control of the end-cap, end-plates welds and of the brazed appendage joints is made by destructive methods (metallographic examinations or mechanical tests) on specimens sampled from production. Having a very limited statistics, these destructive methods are useful only to indicate 'trends' of the production quality, not for detecting infrequent single defect events. It is recognized that nondestructive examination techniques are required to achieve sufficient evidence of the production quality, at a statistically significant sampling rate. For this reason, the INR-Ultraacoustics R and D Lab has develop a family of equipments for high resolution ultrasonic imaging, at performances close to the Acoustic Microscopy domain. The paper make a presentation of the examination methods and of the experimental results obtained on characteristic welds and brazed joints samples. Detailed off-line evaluations of the C-scan and B-scan ultrasonic images are made and comparative analyses with metallography are performed. Also, in the case of end-cap welds, numerical stress analysis are made, in order to establish the influence of flaws on the weld strength. (author)

  16. Method of temperature rising velocity and threshold control of electron beam brazing

    Institute of Scientific and Technical Information of China (English)

    Xuedong Wang; Shun Yao

    2005-01-01

    In order to accommodate electron beam to the brazing of the joints with various curve shapes and the brazing of thermo sensitive materials, the method of electron beam scanning and brazing temperature control was developed, in which electron beam was controlled to scan according to predefined scanning track, and the actual temperature rising velocity of the brazed seam was limited in an allowed scope by detecting the brazed seam temperature, calculating the temperature rising velocity and adjusting the beam current during the brazing process; in addition, through the setting of the highest allowed temperature, the actual temperature of the brazed seam could be controlled not exceeding the threshold set value, and these two methods could be employed alone or jointly. It is shown that high precision temperature control in electron beam brazing could be realized and the productivity be increased by the proposed method.

  17. Experimental study on DNB heat flux of plate-type fuel in pressurized condition

    International Nuclear Information System (INIS)

    Experimental study was carried out in order to determine the DNB correlation for the safety analysis of the JMTR low enrichment fuel core. Since it is essential to examine applicability and safety margin of the correlation for the safety analysis, DNB heat fluxes were measured with the test section of rectangular flow channel simulating JMTR fuel element subchannel in the pressure range of 1 ∼ 13 kg/cm2 abs and the velocity range of 0 ∼ 4.4 m/s. Reviewing existed DNB correlations based on the experimental data, Sudo correlations scheme was selected for the JMTR safety analysis with minor modification for the high flow rate region. Comparing the correlations scheme with experimental data, allowable limit of the minimum DNBR was determined to be 1.5. (author)

  18. Magnetohydrodynamic Fully Developed Combined Convection Flow between Vertical Plates Heated Asymmetrically

    International Nuclear Information System (INIS)

    Magnetohydrodynamic (MHD) fully developed flow of a viscous incompressible electrically conducting fluid in a vertical channel during combined convection, with asymmetric heating of the wall, under the influence of a constant pressure gradient and in the presence of an uniform transverse magnetic field, is studied. Exact solution of the governing equation is obtained in a closed form. The solution in a dimensionless form contains two pertinent flow parameters, viz. M (the Hartmann number) and Gr (the Grashof number). The limiting cases of a MHD forced and free convection are analysed, what has not been done earlier in the literature. The occurrence of flow reversal indicates that there arises a flow reversal at the cold wall when rT=1 while, for rT<1, no flow reversal is possible in the absence of magnetic forces. (author)

  19. Entropy analysis for the Couette flow of non-Newtonian fluids between asymmetrically heated parallel plates: effect of applied pressure gradient

    International Nuclear Information System (INIS)

    The current study discusses the irreversibility analysis for the Couette flow of non-Newtonian fluids between two asymmetrically heated parallel plates for two different flow configurations viz., under the application of a weak pressure gradient and for a relatively strong pressure gradient. The plates are kept at different constant temperatures, while the effect of viscous dissipation is included in the analysis. The study explores the combined consequences of the rheological effect of the fluids, the movement of the upper plate, and the magnitude of the externally applied pressure gradient on the irreversibility generation rate of the system as manifested by the variation of the volumetric entropy generation number, irreversibility distribution ratio, and the Bejan number. Intricate interplay between the effects of fluid friction and heat transfer in dictating the irreversibility of the system is highlighted for different degrees of asymmetrical wall heating and upper-plate velocity. The study further shows that, for a given degree of asymmetrical wall heating, the irreversibility generation rate alters with the alteration in the rheological behaviour of the fluid. (paper)

  20. Effects of Rare Earths on Properties of Ti-Zr-Cu-Ni Base Brazing Filler Alloys

    Institute of Scientific and Technical Information of China (English)

    Ma Tianjun; Kang Hui; Wu Yongqin; Qu Ping

    2004-01-01

    The effects of the addition of rare earths on the properties of Ti-Zr-Cu-Ni base brazing filler alloys and the mechanical microstructure and properties were studied for the brazed-joints in the vacuum brazing of TC4 by comparing synthetical properties of two kinds of filler metals.The results indicate that the filler metals added with rare earths have lower melting point, better wettability and higher mechanical properties in the brazing joints.

  1. The effect of heater orientation on the critical heat flux in a saturated pool boiling with honeycomb porous plate on nanoparticle deposited surface

    International Nuclear Information System (INIS)

    One of the main concerns in In-Vessel Retention (IVR) for a severe accident is to guarantee the sufficient cooling performance in order to avoid melt-through of pressure vessel. Under a severe accident condition, the vessel is submerged in water, and then boiling is occurred. The heat removal is limited by critical heat flux (CHF) at the outer surface of the reactor vessel. Therefore, in order to enhance the capability of the IVR in the severe accident of the light-water reactors, methods to increase the CHF should be considered. Various surface modifications of the boiling surface, e.g., integrated surface structures, such as channels and micro-pin fins, and the coating of a micro-porous layer using sintered metal powders and nanoparticle deposition onto the heat transfer surface, have been proven to effectively enhance the CHF in saturated pool boiling. In particular, the critical heat flux by the attachment of a honeycomb-structured porous plate on a flat heated surface facing upward increases more than approximately twice compared to that of a plain surface under saturated pool boiling condition (Mori and Okuyama (2009)). This is attributed to the honeycomb porous plate which provides automatic liquid supply due to capillary action and the reduction of the vapor escape flow resistance due to the separation of the liquid and vapor flow paths. Moreover, it is well-known that the CHF with nanoparticle deposited heated surface is greatly enhanced. However, the effect of the heated surface orientation on the CHF with honeycomb porous plate on nanoparticle deposited surface is not clarified yet. Therefore, we focus on the use of honeycomb porous plate and nanoparticle coated surface to improve the IVR capability in the severe management strategy implemented by light-water reactors. (author)

  2. High-temperature brazing of X5CrNi18 10 and NiCr20TiAl using the atmospherically plasma-sprayed L-Ni2 filler metal

    International Nuclear Information System (INIS)

    The hybrid-technological combination of the atmospheric plasma spraying for the application of a high-temperature filler metal followed by a brazing process was analyzed in terms of structure and mechanical properties of X5CrNi18 10 and NiCr20TiAl brazing joints. The thickness of the filler metal layer was minimized at <50μm by optimization of the atmospheric plasma spraying process. The brazing seam is hence partly free from brittle phases and yields a increased ultimate tensile strength of brazed and heat-treated joints at different temperatures (room temperature, 500degC and 700degC). Additional information concerning the mechanical properties of the brazing joints was derived from the results of the fractographic examinations of the fracture surfaces and from the characteristic strength values of the long-period creep tests. It was also attempted to apply the results of inductively brazed, cylindrical samples to complex (overlapping joints) and large-surface components produced under practical conditions in the vacuum furnace. (orig.)

  3. Numerical analysis of natural convection and radiation heat transfer from various shaped thin fin-arrays placed on a horizontal plate-a conjugate analysis

    International Nuclear Information System (INIS)

    Highlights: • Optimum fin shape is determined for natural convection and radiation heat transfer. • Fin array with the optimum shape has a much greater average heat transfer coefficient. • The most important factors affecting the heat transfer coefficient are determined. - Abstract: Steady state natural convection and radiation heat transfer from various shaped thin fin-arrays on a horizontal base plate has been numerically investigated. A conjugate analysis has been carried out in which the conservation equations of mass, momentum and energy for the fluid in the two fin enclosure are solved together with the heat conduction equation in the fin and the base plate. Heat transfer by radiation is also considered in analysis. The heat transfer coefficient has been determined for each of the fin array considered in the present study at the same base and the same total area. The results of the analysis show that there are some important geometrical factors affecting the design of fin arrays. Taking into consideration these factors, an optimum fin shape that yields the highest average heat transfer coefficient has been determined

  4. Study on vacuum brazing of high purity alumina for application in proton synchrotron

    International Nuclear Information System (INIS)

    Highlights: • Study compares Mo–Mn metallization and active brazing routes for joining alumina. • Targeted application: UHV chamber of proton synchrotron. • Both kinds of joints were UHV compatible with helium leak rate <1.1 × 10−10 mbar l/s. • Active brazed joints met tensile and flexural strength design requirement (>50 MPa). • Active brazing is a simpler and economical route for joining high purity alumina. - Abstract: The paper describes an experimental study to evaluate two different vacuum brazing processes to obtain high purity alumina (99.7%) joints suitable for application in rapid cycle proton synchrotron. Two different brazing routes, adopted for making alumina–alumina brazed joints, included (i) multi-step Mo–Mn metallization, followed by brazing with BVAg-8 alloy and (ii) advanced single-step active brazing with CuSil-ABA® alloy. Both the brazing routes yielded helium leak tight and ultra-high vacuum (pressure < 10−9 mbar) compatible joints. Active-brazed specimens exhibited tensile and mean flexural strengths of 62 and 110 MPa, respectively. Metallized-brazed specimens, although associated with relatively lower tensile strength (35 MPa) than the targeted value (>50 MPa), displayed higher mean flexural strength of 149 MPa. The results of the study demonstrated that active brazing is a simple and cost effective alternative to conventional multi-step metallization route for producing quality joints of high purity alumina for application in rapid cycle proton synchrotron machine

  5. The Finite Element Method Solution of an Unsteady MHD Free Convection Flow Past an Infinite Vertical Plate with Constant Suction and Heat Absorption

    Directory of Open Access Journals (Sweden)

    A Sri Sailam

    2014-04-01

    Full Text Available The study of unsteady hydro magnetic free convective flow of viscous incompressible and electrically conducting fluids past an infinite vertical porous plate in the presence of constant suction and heat absorbing sinks has been made. Appropriate solutions have been derived for the velocity and temperature fields, skin friction and rate of heat transfer using Galerkin finite element method. It is observed that increase in magnetic field strength decreases the velocity of the fluid. Also the skin friction and rate of heat transfer of the conducting fluid decrease with increase in magnetic field strength.

  6. Fast plasma shutdown by killer pellet injection in JT-60U with reduced heat flux on the divertor plate and avoiding runaway electron generation

    International Nuclear Information System (INIS)

    A killer pellet is an impurity pellet that is injected into a tokamak plasma in order to terminate a discharge without causing serious damage to the tokamak machine. In JT-60U neon ice pellets have been injected into OH and NB heated plasmas and fast plasma shutdowns have been demonstrated without large vertical displacement. The heat pulse on the divertor plate has been greatly reduced by killer pellet injections (KPI), but a low-power heat flux tail with a long time duration is observed. The total energy on the divertor plate increases with longer heat flux tail, so it has been reduced by shortening the tail. Runaway electron (RE) generation has been observed just after KPI and/or in the later phase of the plasma current quench. However, RE generation has been avoided when large magnetic perturbations are excited. These experimental results clearly show that KPI is a credible fast shutdown method avoiding large vertical displacement, reducing heat flux on the divertor plate, and avoiding (or minimizing) RE generation. (Author)

  7. Improved performance of top-emitting oxide-confined polyimide-planarized 980 nm VCSELs with copper-plated heat sinks

    International Nuclear Information System (INIS)

    Top-emitting, oxide-confined, copper-plated 980 nm vertical-cavity surface-emitting lasers (VCSELs) with improved performance were fabricated and characterized. Annular copper-plated heat sinks reduced the device's thermal resistance and increased the output optical power and the bias current density at which the output optical power saturates. Increasing the plated heat sink radii from 0 to 8 µm greater than the mesa diameter for VCSELs with 26 µm mesa diameter and 8 µm active area diameter reduced the measured thermal resistance by 65% and increased the bias current density at which the output optical power saturates by 62%, which increased the maximum output optical power achieved by 162%. VCSELs with active area diameter and heat sink overlap of 8 µm demonstrated ∼64% decrease in active region temperature at the maximum output optical power compared with devices with no heat sink overlap. A 29% improvement in the devices' modulation bandwidth was calculated due to reduced temperature and increased power. Devices with identical mesa diameters of 26 µm and different heat sink overlaps exhibited a threshold current density and a total series resistance of (1.25 ± 4%) kA cm-2 and ∼95 Ω, respectively. Simple VCSEL L-I and thermal models were used to simulate the VCSEL's L-I performance at elevated ambient temperatures. Good agreement between measured and simulated characteristics was obtained. Detailed protocols for critical fabrication steps are presented.

  8. Nonlinear radiation heat transfer effects in the natural convective boundary layer flow of nanofluid past a vertical plate: a numerical study.

    Directory of Open Access Journals (Sweden)

    Meraj Mustafa

    Full Text Available The problem of natural convective boundary layer flow of nanofluid past a vertical plate is discussed in the presence of nonlinear radiative heat flux. The effects of magnetic field, Joule heating and viscous dissipation are also taken into consideration. The governing partial differential equations are transformed into a system of coupled nonlinear ordinary differential equations via similarity transformations and then solved numerically using the Runge-Kutta fourth-fifth order method with shooting technique. The results reveal an existence of point of inflection for the temperature distribution for sufficiently large wall to ambient temperature ratio. Temperature and thermal boundary layer thickness increase as Brownian motion and thermophoretic effects intensify. Moreover temperature increases and heat transfer from the plate decreases with an increase in the radiation parameter.

  9. High-temperature brazing for reliable tungsten-CFC joints

    International Nuclear Information System (INIS)

    The joining of tungsten and carbon-based materials is demanding due to the incompatibility of their chemical and thermophysical properties. Direct joining is unfeasible by the reason of brittle tungsten carbide formation. High-temperature brazing has been investigated in order to find a suitable brazing filler metal (BFM) which successfully acts as an intermediary between the incompatible properties of the base materials. So far only low Cr-alloyed Cu-based BFMs provide the preferential combination of good wetting action on both materials, tolerable interface reactions, and a precipitation free braze joint. Attempts to implement a higher melting metal (e.g. Pd, Ti, Zr) as a BFM have failed up to now, because the formation of brittle precipitations and pores in the seam were inevitable. But the wide metallurgical complexity of this issue is regarded to offer further joining potential

  10. Direct brazing of ceramics, graphite, and refractory metals

    International Nuclear Information System (INIS)

    ORNL has been instrumental in the development of brazing filler metals for joining ceramics, graphite, and refractory metals for application at temperatures above 10000C. The philosophy and techniques employed in the development of these alloys are presented. A number of compositions are discussed that have been satisfactorily used to braze ceramics, graphite, and refractory metals without a prior surface treatment. One alloy, Ti--25 percent Cr--21 percent V, has wet and flowed on aluminum oxide and graphite. Further, it has been utilized in making brazes between different combinations of the three subject materials. The excellent flowability of this alloy and alloys from the Ti--Zr--Ge system is evidenced by the presence of filler metal in the minute pores of the graphite and ceramics

  11. A review of oxide, silicon nitride, and silicon carbide brazing

    International Nuclear Information System (INIS)

    There is growing interest in using ceramics for structural applications, many of which require the fabrication of components with complicated shapes. Normal ceramic processing methods restrict the shapes into which these materials can be produced, but ceramic joining technology can be used to overcome many of these limitations, and also offers the possibility for improving the reliability of ceramic components. One method of joining ceramics is by brazing. The metallic alloys used for bonding must wet and adhere to the ceramic surfaces without excessive reaction. Alumina, partially stabilized zirconia, and silicon nitride have high ionic character to their chemical bonds and are difficult to wet. Alloys for brazing these materials must be formulated to overcome this problem. Silicon carbide, which has some metallic characteristics, reacts excessively with many alloys, and forms joints of low mechanical strength. The brazing characteristics of these three types of ceramics, and residual stresses in ceramic-to-metal joints are briefly discussed

  12. Brazing and inertia welding of dissimilar metal tubing

    International Nuclear Information System (INIS)

    A movable pump limiter is currently being built for the Tore Supra tokamak in Cadarace, France. Part of the assembly has dispersion-strengthened Cu cooling tubes joined to an AISI 316L stainless steel transition sleeve. The steel sleeve is subsequently welded into a 315L manifold. This study was made to evaluate the feasibility of brazing or inertia welding the dissimilar metal, tubing-sleeve transition. An alumina-strengthened copper alloy (DSCu) was selected for the module cooling tubes. The 316L transition pieces varied in diameter from the same nominal size as the DSCu pieces when inertial welding, to a 12.7 mm (1/2 in.) O.D. to accommodate a lap joint when brazing. The wall thickness of the inertia welded 316L pieces was varied to determine the overlap effect on the weld quality. Ag-28Cu, Ag-27.6Cu-4.5Ti, Au-37Cu-3In, and Au-18Ni (wt%) filler metals were chosen for brazing and the braze microstructures and strengths were evaluated. The best wetting was achieved with the Au based filler metals. All of the brazed joints were hydrostatically pressure tested to 10.34 MPa (1500 psi) without a failure. In all cases, an excellent metallurgical bond with a relatively small cold worked region was produced. The inertia welded samples were also pressure and tensile tested under the same test conditions that were used to evaluate the brazed samples. The welds passed the 10.34 MPa hydrostatic pressure inspection and failed under a tensile load in the DSCu piece away form the weld interface. Brazing and inertia welding were successfully used to join DSCu to 316L. The Au-based filler metals produced the best brazes with joint strengths of 480 MPa. The inertia welds had slightly higher strengths, but both failed away from the joint in the DSCu tube. All of these samples passed a 10.34 MPa hydrostatic pressure test. These processes allow flexibility in designing and fabricating a dissimilar metal transition joint

  13. 用ObjectARX开发板翅式换热器参数化CAD系统%evelopment of CAD System for Plate-Fin Heat Exchanger with ObjectARX

    Institute of Scientific and Technical Information of China (English)

    邹群彩; 凌祥; 涂善东

    2001-01-01

    Based on the characteristics of plate-fin heat exchangers,a CAD system was developed with parametric technique and ObjectARX combined with programming language Visual C++,which has integrated the following two advantages-one is powerful image displaying and compiling functions under AutoCAD ambient,the other is object-oriented programming and high efficiency of Visual C++.Thus,the rapid innovation of plate-fin heat exchanger can be realized by this system in conjunction with heat calculation module and rapid pricing system of plate-fin heat exchanger formerly proposed by the authors.

  14. The Study Of The Impact Of Surface Preparation Methods Of Inconel 625 And 718 Nickel-Base Alloys On Wettability By BNi-2 And BNi-3 Brazing Filler Metals

    Directory of Open Access Journals (Sweden)

    Lankiewicz K.

    2015-06-01

    Full Text Available The article discusses the impact of surface preparation method of Inconel 625 and 718 nickel-base alloys in the form of sheets on wettability of the surface. The results of the investigations of surface preparation method (such as nicro-blasting, nickel plating, etching, degreasing, abrasive blasting with grit 120 and 220 and manually grinding with grit 120 and 240 on spreading of BNi-2 and BNi-3 brazing filler metals, widely used in the aerospace industry in high temperature vacuum brazing processes, are presented. Technological parameters of vacuum brazing process are shown. The macro- and microscopic analysis have shown that nicro-blasting does not bring any benefits of wettability of the alloys investigated.

  15. Heat transfer characteristics of a low-Reynolds two-dimensional air jet impinging on a buoyant boundary layer of vertical hot plate

    Energy Technology Data Exchange (ETDEWEB)

    Habibi, K.; Amiri, S.; Ashjaee, M. [Tehran Univ., Tehran (Iran, Islamic Republic of). Dept. of Mechanical Engineering, Laser Diagnostics Lab

    2009-07-01

    A study was conducted to investigate the flow properties and heat transfer behaviour of laminar and turbulent jet flows, with particular focus on the effect of impingement of a laminar slot jet on a vertical isothermal flat plate and the simultaneous interaction of the jet flow and natural buoyant regime. The thermal field was visualized using an experimental approach, while a Mach-Zehnder interferometer was used to obtain the local convective heat transfer coefficient. The planar jet was mounted parallel to the plate surface. The study took into account the variations of jet Reynolds numbers (Re) as well as the nozzle vertical distance from the leading edge of the plate. The jet strength was restricted to relatively low-Reynolds numbers in this study in order to observe the interaction between buoyancy driven flow and the impinging jet. It was concluded that low-speed jet flows could lead to mixed convection regimes. The jet path deviated as it interacted with buoyant flow. In such a flow, a minimum zone for heat transfer coefficient was followed by a peak in a position beyond the jet center. Reattachment occurred for larger Reynolds numbers. Therefore, in cases where heat transfer is a concern, a low-speed jet can enhance the effect above the impingement zone and reduce the effect at the bottom of the impingement zone. 9 refs., 1 tab., 10 figs.

  16. Microwave-assisted brazing of alumina ceramics for electron tube applications

    Indian Academy of Sciences (India)

    2016-04-01

    Alumina was joined with alumina using microwave-assisted and conventional brazing methods at 960$^{\\circ}$C for 15 min using TiCuSil (68.8Ag–26.7Cu–4.5Ti in wt.%) as the brazing alloy. The brazed joints were characterizedby X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, Vickers microhardness evaluation, brazing strength measurement and helium leak test. X-ray diffraction analysis confirmed the formationof Ti-based compounds at the substrate-filler alloy interfaces of the microwave and conventionally brazed joints. The elemental compositions at the joint cross-section were determined by energy dispersive X-ray analysis. Vickers microhardness measurement indicated reliable joint performance for the microwave-assisted brazed joints during actual application in an electron tube. Brazing strength measurement and helium leak test provided the evidence forgood alumina-alumina joint formation.

  17. Two-beam Laser Brazing of Thin Sheet Steel for Automotive Industry Using Cu-base Filler Material

    Science.gov (United States)

    Mittelstädt, C.; Seefeld, T.; Reitemeyer, D.; Vollertsen, F.

    This work shows the potential of two-beam laser brazing for joining both Zn-coated steel and 22MnB5. Brazing of Zn-coated steel sheets using Cu-Si filler wire is already state of the art in car manufacturing. New press-hardened steels like 22MnB5 are more and more used in automotive industry, offering high potential to save costs and improve structural properties (reduced weight / higher stiffness). However, for joining of these ultra-high strength steels investigations are mandatory. In this paper, a novel approach using a two-beam laser brazing process and Cu-base filler material is presented. The use of Cu-base filler material leads to a reduced heat input, compared to currently applied welding processes, which may result in benefits concerning distortion, post processing and tensile strength of the joint. Reliable processing at desired high speeds is attained by means of laser-preheating. High feed rates prevent significant diffusion of copper into the base material.

  18. Mixed convective MHD flow of a micropolar fluid with ohmic heating, radiation and viscous dissipation over a chemically reacting porous plate subjected to a constant heat flux and concentration gradient

    Directory of Open Access Journals (Sweden)

    Kumar Hitesh

    2014-01-01

    Full Text Available In the present paper analysis of a chemically reacting mixed convection MHD micropolar flow, heat and mass transfer in porous medium with the effects of ohmic heating, radiation and viscous dissipation past an infinite vertical plate which is subjected to a constant heat flux and the concentration gradient. The non-linear coupled partial differential equations are solved numerically using an implicit finite difference scheme known as Keller-box method. The results for concentration, transverse velocity, angular velocity and temperature are obtained and illustrated graphically to observe the effects of various parameters, and the numerical discussion is presented with physical interpretations.

  19. Effects of Hall Current on Hydromagnetic Natural Convection Flow of a Heat Absorbing Fluid past an Impulsively Moving Vertical Plate with Ramped Temperature

    Directory of Open Access Journals (Sweden)

    Gauri Shanker Seth

    2012-08-01

    Full Text Available Effects of Hall current on unsteady MHD natural convection flow of a viscous, incompressible, electrically conducting and heat absorbing fluid past an impulsively moving vertical plate with ramped wall temperature in a porous medium, in the presence of thermal diffusion, is studied. The exact solution of momentum and energy equations, under Boussinesq approximation, is obtained in closed form by Laplace transform technique for both ramped temperature and isothermal plates. Solution is also obtained in the case of unit Prandtl number for both ramped temperature and isothermal plates. The expressions for skin friction due to primary and secondary flows and Nusselt number for both ramped temperature and isothermal plates are also derived. Mathematical formulation of the problem, in non-dimensional form, contains six pertinent flow parameters viz. M^2 (magnetic parameter, m (Hall current parameter Gr (Grashof number, K1 (permeability parameter, Pr (Prandtl number and Phi (heat absorption coefficient. The numerical values of primary and secondary fluid velocities are displayed graphically versus boundary layer coordinate y for various values of m, Gr, K1, Phi and t while that of fluid temperature are presented in graphical form versus y for different values of Pr, Phi and t for both ramped temperature and isothermal plates. For both ramped temperature and isothermal plates, the numerical values of skin friction due to primary and secondary flows are presented in tabular form for various values of m, Gr, K1, Phi and t whereas that of Nusselt number are given in tables for different values of Pr, Phi and t.

  20. Field installed brazed thermocouple feedthroughs for high vacuum experiments

    Science.gov (United States)

    Anderson, P. M.; Messick, C.

    1983-12-01

    In order to reduce the occurrence of vacuum leaks and to increase the availability of the DIII vacuum vessel for experimental operation, effort was applied to developing a vacuum-tight brazed feedthrough system for sheathed thermocouples, stainless steel sheathed conductor cables and tubes for cooling fluids. This brazed technique is a replacement for elastomer O ring sealed feedthroughs that have proven vulnerable to leaks caused by thermal cycling, etc. To date, about 200 feedthroughs were used. Up to 91 were grouped on a single conflat flange mounted in a bulkhead connector configuration which facilitates installation and removal. Investigation was required to select a suitable braze alloy, flux and installation procedure. Braze alloy selection was challenging since the alloy was required to have: (1) melting temperature in excess of the 250 C (482 F) bakeout temperature; (2) no high vapor pressure elements; (3) good wetting properties when used in air with acceptable flux; and (4) good wettability to 300 series stainless steel and Inconel.

  1. Brazed boron-silicon carbide/aluminum structural panels

    Science.gov (United States)

    Arnold, W. E., Jr.; Bales, T. T.; Brooks, T. G.; Lawson, A. G.; Mitchell, P. D.; Royster, D. M.; Wiant, R.

    1978-01-01

    Fluxless brazing process minimizes degradation of mechanical properties composite material of silicon carbide coated boron fibers in an aluminum matrix. Process is being used to fabricate full-scale Boron-Silicon Carbide/Aluminum-Titanium honeycomb core panels for flight testing and ground testing.

  2. The influence of walls and upper tie plate slots on the flooding mechanism in fuel elements with and without heat transfer between steam and water

    International Nuclear Information System (INIS)

    The counter-current flow of steam and water was experimentally investigated for the upper part of a PWR fuel element. The actual geometrical shape of the nuclear equipment was simulated by various types of plates, in which bore holes and slots were arranged in different positions. The experiments were performed with and without an installed, unheated rod bundle below the plates. The water was injected at saturated and subcooled temperatures in order to observe the effects of heat transfer on counter-current flow. With increasing steam velocity the flooding occurs initially in the tie-plate area. If the rod bundle is installed in the flow duct, a part of the downwards flowing water is transported upwards from the region of the upper grid spacer to the plate. Heat transfer between the phases can cause in the counter-current flow region an instable transition from downward to near complete upward directed liquid flow. In comparison to experiments with saturated water injection, flooding occurs at larger steam velocities. Different flooding correlations, which are known from the literature, were compared with the experimental data to appraise their applicability to counter-current flow in the core of PWRs. (orig.)

  3. Divertor plate biasing effects on particle recycling and power loss distribution in TdeV during lower hybrid current drive and heating experiments

    International Nuclear Information System (INIS)

    Preliminary results concerning the influence of negative biasing of the divertor plates on particle recycling and on power loss distribution in single null discharges of TdeV during lower hybrid (LH) current drive and heating experiments are presented. The beneficial effects of negative biasing of the divertor plates, such as the ability to control power and particle fluxes in the SOL, remain effective in the presence of auxiliary heating and current drive. Up to 0.7 MW of auxiliary power were injected in these experiments. With a negative biasing of 150 V, and the ExB flow vector pointing towards the outer divertor chamber, a roughly 2 fold increase in the divertor pressure and the radiation from the divertor region is observed. ((orig.))

  4. 中国古青铜器表面富锡铜鎏镀及鎏焊的工艺探索第三部分——鎏焊%Technological study on amalgam coating and brazing of tin-rich copper on surface of bronze wares of ancient China——Part Ⅲ.Amalgam brazing

    Institute of Scientific and Technical Information of China (English)

    吴元康; 储荣邦

    2012-01-01

    Amalgam brazing is derived from amalgam coating. The definition, characteristics, application, and significance of amalgam brazing were expatiated. A process of amalgam brazing for producing combined bronze wares was developed. The compositions of brazing material and flux were given. The operations of pretreatment, mercury removal by heating, and post-treatment were described. The implementation of amalgam coating and brazing processes was introduced taking the Western Han Dynasty's bronze cowry container with tribute-paying figures excavated in Yunnan as an example. The method for distinguishing whether an antique bronze ware is produced by cast welding after lost-wax casting or by copper brazing with separated small cast parts was presented.%鎏焊是从鎏镀衍生而来的.阐述了鎏焊的定义、特点、应用和意义.设计了用于制作组合青铜器的鎏焊工艺,给出了焊料、焊剂配方,说明了前处理、加热驱汞及后处理的操作方法.以西汉云南纳贡场面青铜贮贝器为例,介绍了鎏镀与鎏焊工艺的具体实施过程.提出了鉴别古青铜器是由失蜡铸造后铸焊而成还是由分铸小件铜焊而成的方法.

  5. An analytical study of MHD heat and mass transfer oscillatory flow of a micropolar fluid over a vertical permeable plate in a porous medium

    OpenAIRE

    MODATHER, M.; RASHAD, A. M.; CHAMKHA, A. J.

    2009-01-01

    An analytical solution is presented for the problem of heat and mass transfer of an oscillatory 2-dimensional viscous, electrically conducting micropolar fluid over an infinite moving permeable plate in a saturated porous medium in the presence of a transverse magnetic field. Numerical solutions are given for the governing momentum, angular momentum, energy, and concentration equations. The effects of permeability and chemical reaction parameters are presented, graphically or in tabl...

  6. Combined Effect of Buoyancy Force and Navier Slip on MHD Flow of a Nanofluid over a Convectively Heated Vertical Porous Plate

    OpenAIRE

    Winifred Nduku Mutuku-Njane; Oluwole Daniel Makinde

    2013-01-01

    We examine the effect of magnetic field on boundary layer flow of an incompressible electrically conducting water-based nanofluids past a convectively heated vertical porous plate with Navier slip boundary condition. A suitable similarity transformation is employed to reduce the governing partial differential equations into nonlinear ordinary differential equations, which are solved numerically by employing fourth-order Runge-Kutta with a shooting technique. Three different water-based nanofl...

  7. Square Heating Applied to Shearography and Active Infrared Thermography Measurements Coupling: From Feasibility Test in Laboratory to Numerical Study of Pultruded CFRP Plates Glued on Concrete Specimen

    OpenAIRE

    THEROUX, Luc D.; Dumoulin, Jean; MALADAGUE, X

    2014-01-01

    This paper investigates thermography and shearography couplings, using feasibility trials and numerical simulations, for non-destructive control evaluations of bonding of carbon fiber-reinforced polymer plates glued over concrete structures. Those are well-known methods in non-destructive testing (NDT) applied to civil engineering, but in this context, they are seen as paired because they use the same excitation source: square-pulsed optical heating. Furthermore, because both methods are base...

  8. MHD Effects on Non-Newtonian Power-Law Fluid Past a Continuously Moving Porous Flat Plate with Heat Flux and Viscous Dissipation

    Science.gov (United States)

    Kishan, N.; Shashidar Reddy, B.

    2013-06-01

    The problem of a magneto-hydro dynamic flow and heat transfer to a non-Newtonian power-law fluid flow past a continuously moving flat porous plate in the presence of sucion/injection with heat flux by taking into consideration the viscous dissipation is analysed. The non-linear partial differential equations governing the flow and heat transfer are transformed into non-linear ordinary differential equations using appropriate transformations and then solved numerically by an implicit finite difference scheme. The solution is found to be dependent on various governing parameters including the magnetic field parameter M, power-law index n, suction/injection parameter ƒw, Prandtl number Pr and Eckert number Ec. A systematical study is carried out to illustrate the effects of these major parameters on the velocity profiles, temperature profile, skin friction coefficient and rate of heat transfer and the local Nusslet number.

  9. A coupled numerical model for tube-on-sheet flat-plate solar liquid collectors. Analysis and validation of the heat transfer mechanisms

    International Nuclear Information System (INIS)

    Highlights: • A novel 3D coupled model for flat-plate solar liquid collectors has been developed. • The predicted thermal efficiency is in agreement with the experimentally obtained. • The implemented solar load model accounts for high and low wavelength radiation. • Enhanced asymptotic Nusselt number for mixed convection inside risers is reported. • Irregular free convection in air gap is due to non-uniform absorber temperature. - Abstract: A 3D numerical model for flat-plate liquid solar collectors has been developed. This model is envisioned for predicting the efficiency curve of the collector, for which the different heat transfer mechanisms involved are simultaneously taken into account: solar radiation absorption, transmission and reflection; natural convection in the air cavity; heat conduction across the tube-absorber welded junction; mixed convection flow in the risers; and heat losses by convection and radiation to the ambient. To ensure the reliability of the model, the heat transfer results inside the risers and in the air cavity were contrasted with well-known experimental correlations available in the open literature. The thermal efficiency obtained with this numerical model is successfully validated against own experimental data. This heat transfer model is intended for evaluating the impact of different operating conditions and design features on the overall performance of solar collectors, reducing costs in prototype construction and experimentation

  10. Effects of internal heat generation, thermal radiation and buoyancy force on a boundary layer over a vertical plate with a convective surface boundary condition

    Directory of Open Access Journals (Sweden)

    Tasawar Hayat

    2011-09-01

    Full Text Available In this paper we analyse the effects of internal heat generation, thermal radiation and buoyancy force on the laminar boundary layer about a vertical plate in a uniform stream of fluid under a convective surface boundary condition. In the analysis, we assumed that the left surface of the plate is in contact with a hot fluid whilst a stream of cold fluid flows steadily over the right surface; the heat source decays exponentially outwards from the surface of the plate. The similarity variable method was applied to the steady state governing non-linear partial differential equations, which were transformed into a set of coupled non-linear ordinary differential equations and were solved numerically by applying a shooting iteration technique together with a sixth-order Runge–Kutta integration scheme for better accuracy. The effects of the Prandtl number, the local Biot number, the internal heat generation parameter, thermal radiation and the local Grashof number on the velocity and temperature profiles are illustrated and interpreted in physical terms. A comparison with previously published results on similar special cases showed excellent agreement.

  11. Effects of Thermal Radiation and Chemical Reaction on MHD Free Convection Flow past a Flat Plate with Heat Source and Convective Surface Boundary Condition

    Directory of Open Access Journals (Sweden)

    E.Hemalatha

    2015-09-01

    Full Text Available This paper analyzes the radiation and chemical reaction effects on MHD steady two-dimensional laminar viscous incompressible radiating boundary layer flow over a flat plate in the presence of internal heat generation and convective boundary condition. It is assumed that lower surface of the plate is in contact with a hot fluid while a stream of cold fluid flows steadily over the upper surface with a heat source that decays exponentially. The Rosseland approximation is used to describe radiative heat transfer as we consider optically thick fluids. The governing boundary layer equations are transformed into a system of ordinary differential equations using similarity transformations, which are then solved numerically by employing fourth order Runge-Kutta method along with shooting technique. The effects of various material parameters on the velocity, temperature and concentration as well as the skin friction coefficient, the Nusselt number, the Sherwood number and the plate surface temperature are illustrated and interpreted in physical terms. A comparison of present results with previously published results shows an excellent agreement.

  12. Modal Analysis of Flat Plate Structure in Aluminum Heating Plate Automatic Casting System%铝发热盘自动浇铸系统中平盘结构模态分析

    Institute of Scientific and Technical Information of China (English)

    弓满锋; 隋广洲; 梁炎锋

    2013-01-01

    The inherent frequency and vibration mode of a flat plate structure in the four working-stations aluminum heating plate automatic casting system were studied by modal analysis technology. The former-ten-steps inherent frequency and vibration modes of the structure were calculated by ANSYS 8. 0 finite element software. On the basis of the engineering practical application,the former-three-steps inherent frequency and vibration modes were especially analyzed,and the values were 211. 78,214. 86,225. 12 Hz re-spectively. The conclusion shows that the bending-deflection of rotating flat plate is serious if the quality of casting working-station is heavy,and the maximum deflection appears in the rim of the flat plate. It is harmful to the structure,such as decreasing the safety and lifetime or increasing the difficulties of casting and dismounting products by robot. It is sure that the following measures can be used to increase the flat plate stiffness,such as decreasing the flat plate diameter,retrofitting support device under the rim of flat plate and lightening the casting working-station quality.%  采用模态分析技术研究一种四工位铝发热盘自动浇铸系统中平盘结构的固有频率和振型,应用ANSYS 8.0有限元软件计算出该结构的前10阶固有频率和各阶频率所对应的振型.结合工程实际应用,重点分析了该结构前3阶固有频率,分别是211.78,214.86,225.12 Hz.结果表明:浇铸工位质量较大将导致平盘旋转时弯曲变形较大,且最大变形量出现在平盘轮缘位置.这对结构的安全性、寿命和机器人浇铸、拆装产品操作等都带来不利的影响.要提高平盘刚度,则应适当减小平盘直径、在平盘轮缘下加装支撑装置和减轻浇铸工位的质量.

  13. Microgalvanic Corrosion Behavior of Cu-Ag Active Braze Alloys Investigated with SKPFM

    Directory of Open Access Journals (Sweden)

    Armen Kvryan

    2016-04-01

    Full Text Available The nature of microgalvanic couple driven corrosion of brazed joints was investigated. 316L stainless steel samples were joined using Cu-Ag-Ti and Cu-Ag-In-Ti braze alloys. Phase and elemental composition across each braze and parent metal interface was characterized and scanning Kelvin probe force microscopy (SKPFM was used to map the Volta potential differences. Co-localization of SKPFM with Energy Dispersive Spectroscopy (EDS measurements enabled spatially resolved correlation of potential differences with composition and subsequent galvanic corrosion behavior. Following exposure to the aggressive solution, corrosion damage morphology was characterized to determine the mode of attack and likely initiation areas. When exposed to 0.6 M NaCl, corrosion occurred at the braze-316L interface preceded by preferential dissolution of the Cu-rich phase within the braze alloy. Braze corrosion was driven by galvanic couples between the braze alloys and stainless steel as well as between different phases within the braze microstructure. Microgalvanic corrosion between phases of the braze alloys was investigated via SKPFM to determine how corrosion of the brazed joints developed.

  14. Numerical analysis of flow and heat transfer behavior in fin-tube flat-plate solar collector

    Institute of Scientific and Technical Information of China (English)

    Namory Camara; LU Hui-lin

    2007-01-01

    Temperature distribution over the absorber plate of a parallel flow flat-plate solar collector is numerically analyzed. The governing differential equations with boundary conditions are solved numerically using fluent software. Effects of the inlet mass flux, inlet temperature and tube spacing on velocity and temperature distributions are discussed. Numerical results show that the distributions of velocity and temperature of fluid is unsymmetrical inside pipe.

  15. Brazing of AM-350 stainless steel LWBR fuel rod support grids (LWBR Development Program)

    Energy Technology Data Exchange (ETDEWEB)

    Ebejer, L.P.

    1979-02-01

    A brazing process has been developed wherein several hundred stamped AM-350 stainless steel sheet metal components, wire components and machined bar components were simultaneously joined together to fabricate about 400 grids of different sizes for the LWBR fuel rod support system. High temperature (2110F +- 20F) vacuum brazing was employed using Ni--Cr--Si braze alloy filler metal in the form of paste. Techniques employed in the assembly, braze alloy application and fixturing of grids to achieve adequate dimensional control are discussed in detail. The brazing thermal cycle as related to the complex metallurgical process of both AM-350 stainless steel and the Ni--Cr--Si braze alloy is also discussed.

  16. Active metal brazing of titanium to high-conductivity carbon-based sandwich structures

    International Nuclear Information System (INIS)

    Reactive brazing technology was developed and processing parameters were optimized for the bonding of titanium tubes, graphite foam, and high-conductivity carbon-carbon composite face sheets using the active braze Cusil-ABA paste and foils. The microstructure and composition of the joints, examined using scanning electron microscopy coupled with energy-dispersive spectroscopy, showed good bonding and braze penetration in all systems when braze paste was used. The hardness values of the brazed joints were consistent for the different specimen stacking configurations. Mechanical testing of Ti tube/foam/C-C composite structures both in tension and shear showed that failure always occurred in the foam material demonstrating that the brazed joint was sufficient for these types of sandwich structures

  17. Second law analysis for free convection in non-newtonian fluids over a horizontal plate embedded in a porous medium: (prescribed heat flux

    Directory of Open Access Journals (Sweden)

    W. A. Khan

    2012-09-01

    Full Text Available Second law characteristics of heat transfer and fluid flow due to free convection of non-Newtonian fluids over a horizontal plate with prescribed surface heat flux in a porous medium are analyzed. Velocity and temperature fields are obtained numerically using an implicit finite difference method under the similarity assumption and these results are used to compute the entropy generation rate Ns, irreversibility ratio φ and the Bejan number Be for both Newtonian and non-Newtonian fluids. The effects of power-law index n, heat flux variation parameter λ , and modified duty parameter, G on the dimensionless entropy generation rate Ns, and the Bejan number Be are investigated and presented graphically.

  18. Influence of Heat Shock Temperatures and Fast Freezing on Viability of Probiotic Sporeformers and the Issue of Spore Plate Count Versus True Numbers

    Directory of Open Access Journals (Sweden)

    Mojtaba Jafari

    2016-02-01

    Full Text Available Background and Objectives: The purpose of the present study was to investigate effects of various heat shock conditions and fast freezing and subsequent thawing on the viability and recovery of Bacillus coagulans and Bacillus subtilis as probiotic sporeformers, and also to compare spore plate and microscopic counts. Materials and Methods: After preparing the final suspensions of B. coagulans and Bacillus subtilis subsp. Natto spores, they were spread-plated before and after fast freezing treatment (-70°C for about 1 min. Heat shock treatments of the spores were carried out at 68oC for 15, 20, and 30 min as well as at 80oC for 10 and 15 min. Concentrations of the examined probiotic sporeformers were determined simultaneously by plate enumerations and microscopically determined counts. Student’s t-test and one-way analysis of variance (ANOVA of SPSS were used for statistical analysis of the data. Analysis of DoE results was carried out using Minitab. Results: The results presented here show that the highest recovery rates for B. coagulans (14.75 log CFU/mL and B. subtilis spores (14.80 log CFU/mL were under a heat shock condition of 68°C for 20 min in nutrient agar (p<0.05. In addition, the survival rates of B. coagulans and B. subtilis spores under the fast freezing and subsequent thawing condition were about 90% and 88%, respectively. Plate counts differed significantly from counts determined microscopically, with differences of almost 0.5 and 0.8 log for B. coagulans and B. subtilis spores, respectively (p<0.05. In addition, DoE results of the study revealed that both factors of spore count method and only freezing factor in fast freezing treatment have a significant effect on concentrations of the spores examined (p<0.05. Conclusions: Heat shock conditions, freezing and subsequent thawing circumstances, and plate counts or enumerations determined microscopically have significant influences on the viability of probiotic sporeformers and

  19. Silicon-micromachined microchannel plates

    CERN Document Server

    Beetz, C P; Steinbeck, J; Lemieux, B; Winn, D R

    2000-01-01

    Microchannel plates (MCP) fabricated from standard silicon wafer substrates using a novel silicon micromachining process, together with standard silicon photolithographic process steps, are described. The resulting SiMCP microchannels have dimensions of approx 0.5 to approx 25 mu m, with aspect ratios up to 300, and have the dimensional precision and absence of interstitial defects characteristic of photolithographic processing, compatible with positional matching to silicon electronics readouts. The open channel areal fraction and detection efficiency may exceed 90% on plates up to 300 mm in diameter. The resulting silicon substrates can be converted entirely to amorphous quartz (qMCP). The strip resistance and secondary emission are developed by controlled depositions of thin films, at temperatures up to 1200 deg. C, also compatible with high-temperature brazing, and can be essentially hydrogen, water and radionuclide-free. Novel secondary emitters and cesiated photocathodes can be high-temperature deposite...

  20. Active brazed diamond and cubic boron nitride interfacial nanostructure and application

    International Nuclear Information System (INIS)

    Active brazing is an effective technique for joining diamond or cBN grit onto metallic substrates. Current use of this technique is being made for super abrasive, high performance tools. The lecture will give an overview over different aspects such as (i) tool performance in selected applications, (ii) interfacial nanostructure between super abrasive grit and brazing alloys matrix, (iii) attempts to computer model such interface reactions and (iv) recent improvements of the abrasion resistance of the brazing alloy itself. Super abrasive tools with outstanding performance in applications such as grinding, honing or stone cutting can be manufactured by a single-layer of brazed diamond or cBN grit. A method to obtain regular grit patterns will be presented. Examples of prototype tools and their performance in different applications will be shown. The investigation of interface reactions between diamond and active brazing alloys plays an important role to further improve the brazing process and resulting tool performance. The interfacial nanostructure is characterised by a thin reaction layer of Ti with diamond and cBN, respectively. Results for Ag- and Cu-based brazing alloys will be presented and discussed in view of the influence of brazing process parameters and brazing alloy matrix. Computer modelling of the thermodynamics and kinetics of the interface reactions may allow optimising the process parameters. This requires reliable databases currently being built up. The potential of such methods in ceramic to metal joining will be described. The abrasion resistance of brazing alloys itself plays an important role for tool performance. A new method to achieve a dispersion of nano sized TiC precipitates in the alloy matrix by addition of an organic binder, decomposing during brazing will be presented. In an outlook further applications of brazed diamond grit, such as thermal management materials will be discussed. (author)