Determination of heat transfer coefficient for an interaction of sub-cooled gas and metal

International Nuclear Information System (INIS)

Sidek, Mohd Zaidi; Kamarudin, Muhammad Syahidan

2016-01-01

Heat transfer coefficient (HTC) for a hot metal surface and their surrounding is one of the need be defined parameter in hot forming process. This study has been conducted to determine the HTC for an interaction between sub-cooled gas sprayed on a hot metal surface. Both experiments and finite element have been adopted in this work. Initially, the designated experiment was conducted to obtain temperature history of spray cooling process. Then, an inverse method was adopted to calculate the HTC value before we validate in a finite element simulation model. The result shows that the heat transfer coefficient for interaction of subcooled gas and hot metal surface is 1000 W/m 2 K. (paper)

Coolant material effect on the heat transfer rates of the molten metal pool with solidification

International Nuclear Information System (INIS)

Cho, Jae Seon; Suh, Kune Y.; Chung, Chang Hyun; Park, Rae Joon; Kim, Sang Baik

1998-01-01

Experimental studies on heat transfer and solidification of the molten metal pool with overlying coolant with boiling were performed. The simulant molten pool material is tin (Sn) with the melting temperature of 232 degree C. Demineralized water and R113 are used as the working coolant. This work examines the crust formation and the heat transfer characteristics of the molten metal pool immersed in the boiling coolant. The Nusselt number and the Rayleigh number in the molten metal pool region of this study are compared between the water coolant case and the R113 coolant case. The experimental results for the water coolant are higher than those for R113. Also, the empirical relationship of the Nusselt number and the Rayleigh number is compared with the literature correlations measured from mercury. The present experimental results are higher than the literature correlations. It is believed that this discrepancy is caused by the effect of the heat loss to the environment on the natural convection heat transfer in the molten pool

The design of a heat transfer liquid metal MHD experiment for ALEX [Argonne Liquid-Metal Experiment

International Nuclear Information System (INIS)

Picologlou, B.F.; Reed, C.B.; Hua, T.Q.; Lavine, A.S.

1988-01-01

An experiment to study heat transfer in liquid metal MHD flow, under conditions relevant to coolant channels for tokamak first wall and high heat flux devices, is described. The experimental configuration is a rectangular duct in a transverse magnetic field, heated on one wall parallel to the field. The specific objective of the experiment is to resolve important issues related to the presence and heat transfer characteristics of wall jets and flow instabilities in MHD flows in rectangular duct with electrically conducting walls. Available analytical tools for MHD thermal hydraulics have been used in the design of the test article and its instrumentation. Proposed tests will cover a wide range of Peclet and Hartmann numbers and interaction parameters. 14 refs., 3 figs., 1 tab

A concentrated solar cavity absorber with direct heat transfer through recirculating metallic particles

Energy Technology Data Exchange (ETDEWEB)

Sarker, M. R. I., E-mail: islamrabiul@yahoo.com; Saha, Manabendra, E-mail: manabendra.saha@adelaide.edu.au, E-mail: manab04me@gmail.com; Beg, R. A. [Department of Mechanical Engineering, Rajshahi University of Engineering and Technology, Rajshahi-6204 (Bangladesh)

2016-07-12

A recirculating flow solar particle cavity absorber (receiver) is modeled to investigate the flow behavior and heat transfer characteristics of a novel developing concept. It features a continuous recirculating flow of non-reacting metallic particles (black silicon carbide) with air which are used as a thermal enhancement medium. The aim of the present study is to numerically investigate the thermal behavior and flow characteristics of the proposed concept. The proposed solar particle receiver is modeled using two phase discrete particle model (DPM), RNG k-flow model and discrete ordinate (DO) radiation model. Numerical analysis is carried out considering a solar receiver with only air and the mixture of non-reacting particles and air as a heat transfer as well as heat carrying medium. The parametric investigation is conducted considering the incident solar flux on the receiver aperture and changing air flow rate and recirculation rate inside the receiver. A stand-alone feature of the recirculating flow solar particle receiver concept is that the particles are directly exposed to concentrated solar radiation monotonously through recirculating flow inside the receiver and results in efficient irradiation absorption and convective heat transfer to air that help to achieve high temperature air and consequently increase in thermal efficiency. This paper presents, results from the developed concept and highlights its flow behavior and potential to enhance the heat transfer from metallic particles to air by maximizing heat carrying capacity of the heat transfer medium. The imposed milestones for the present system will be helpful to understand the radiation absorption mechanism of the particles in a recirculating flow based receiver, the thermal transport between the particles, the air and the cavity, and the fluid dynamics of the air and particle in the cavity.

Liquid metal MHD and heat transfer in a tokamak blanket slotted coolant channel

International Nuclear Information System (INIS)

Reed, C.B.; Hua, T.Q.; Black, D.B.; Kirillov, I.R.; Sidorenkov, S.I.; Shapiro, A.M.; Evtushenko, I.A.

1993-01-01

A liquid metal MHD (Magnetohydrodynamic)/heat transfer test was conducted at the ALEX (Argonne Liquid Metal Experiment) facility of ANL (Argonne National Laboratory), jointly between ANL and NIIEFA (Efremov Institute). The test section was a rectangular slotted channel geometry (meaning the channel has a high aspect ratio, in this case 10:1, and the long side is parallel to the applied magnetic field). Isothermal and heat transfer data were collected. A heat flux of ∼9 W/cm 2 was applied to the top horizontal surface (the long side) of the test section. Hartmann Numbers to 1050 (2 Tesla), interaction parameters to 9 x 10 3 , Peclet numbers of 10--200, based on the half-width of the small dimension (7mm), and velocities of 1--75 cm/sec. were achieved. The working fluid was NaK (sodium potassium eutectic). All four interior walls were bare, 300-series stainless steel, conducting walls

Liquid-Metal/Water Direct Contact Heat Exchange: Flow Visualization, Flow Stability, and Heat Transfer Using Real-Time X-Ray Imaging

International Nuclear Information System (INIS)

Abdulla, Sherif H.; Liu Xin; Anderson, Mark H.; Bonazza, Riccardo; Corradini, Michael L.; Cho, Dae; Page, Richard

2005-01-01

Advanced reactor system designs are being considered with liquid-metal cooling connected to a steam power cycle. In addition, current reactor safety systems are considering auxiliary cooling schemes that assure ex-vessel debris coolability utilizing direct water injection into molten material pools to achieve core quenching and eventual coolability. The phenomenon common in both applications is direct contact heat exchange. The current study focuses on detailed measurements of liquid-metal/water direct contact heat exchange that is directly applicable to improvements in effective heat transfer in devices that are being considered for both of these purposes.In this study, a test facility was designed at the University of Wisconsin-Madison to map the operating range of liquid-metal/water direct contact heat exchange. The test section (184-cm height, 45.75-cm width, and 10-cm depth) is a rectangular slice of a larger heat exchange device. This apparatus was used not only to provide measurements of integral thermal performance (i.e., volumetric heat transfer coefficient), but also local heat transfer coefficients in a bubbly flow regime with X-ray imaging based on measured parameters such as bubble formation time, bubble rise velocity, and bubble diameters.To determine these local heat transfer coefficients, a complete methodology of the X-ray radiography for two-phase flow measurement has been developed. With this methodology, a high-energy X-ray imaging system is optimized for our heat exchange experiments. With this real-time, large-area, high-energy X-ray imaging system, the two-phase flow was quantitatively visualized. An efficient image processing strategy was developed by combining several optimal digital image-processing algorithms into a software computational tool written in MATLAB called T-XIP. Time-dependent heat transfer-related variables such as bubble volumes and velocities, were determined. Finally, an error analysis associated with these measurements

Heat transfer enhancement in energy storage in spherical capsules filled with paraffin wax and metal beads

International Nuclear Information System (INIS)

Ettouney, Hisham; Alatiqi, Imad; Al-Sahali, Mohammad; Al-Hajirie, Khalida

2006-01-01

Energy storage is an attractive option to conserve limited energy resources, where more than 50% of the generated industrial energy is discarded in cooling water and stack gases. This study focuses on the evaluation of heat transfer enhancement in phase change energy storage units. The experiments are performed using spherical capsules filled with paraffin wax and metal beads. The experiments are conducted by inserting a single spherical capsule filled with wax and metal beads in a stream of hot/cold air. Experimental measurements include the temperature field within the spherical capsule and in the air stream. To determine the enhancement effects of the metal beads, the measured data is correlated against those for a spherical capsule filled with pure wax. Data analysis shows a reduction of 15% in the melting and solidification times upon increasing the number and diameter of the metal beads. This reduction is caused by a similar decrease in the thermal load of the sphere due to replacement of the wax by metal beads. The small size of the spherical capsule limits the enhancement effects; this is evident upon comparison of the heat transfer in a larger size, double pipe energy storage unit, where 2% of the wax volume is replaced with metal inserts, result in a three fold reduction in the melting/solidification time and a similar enhancement in the heat transfer rate

Heaters to simulate fuel pins for heat transfer tests in single-phase liquid-metal-flow

International Nuclear Information System (INIS)

Casal, V.; Graf, E.; Hartmann, W.

1976-09-01

The development of heaters for thermal simulation of the fuel elements of liquid metal cooled fast breeder reactors (SNR) is reported. Beginning with the experimental demands various heating methods are discussed for thermodynamic investigations of the heat transfer in liquid metals. Then a preferred heater rod is derived to simulate the fuel pins of a SNR. Finally it is reported on the fabrication and the operation practice. (orig.) [de

Heat transfer in intermediate heat exchanger under low flow rate conditions

International Nuclear Information System (INIS)

Mochizuki, H.

2008-01-01

The present paper describes the heat transfer in intermediate heat exchangers (IHXs) of liquid metal cooled fast reactors when flow rate is low such as a natural circulation condition. Although empirical correlations of heat transfer coefficients for IHX were derived using test data at the fast reactor 'Monju' and 'Joyo' and also at the 50 MW steam generator facility, the heat transfer coefficient was very low compared to the well known correlation for liquid metals proposed by Seban-Shimazaki. The heat conduction in IHX was discussed as a possible cause of the low Nusselt number. As a result, the heat conduction is not significant under the natural circulation condition, and the heat conduction term in the energy equation can be neglected in the one-dimensional plant dynamics calculation. (authors)

Development of natural convection heat transfer correlation for liquid metal with overlying boiling coolant

International Nuclear Information System (INIS)

Cho, Jae Seon; Suh, Kune Y.; Chung, Chang Hyun; Park, Rae Joon; Kim, Sang Baik

1999-01-01

Experimental study was performed to investigate the natural convection heat transfer characteristics and the crust formation of the molten metal pool concurrent with forced convective boiling of the overlying coolant. Tests were performed under the condition of the bottom surface heating in the test section and the forced convection of the coolant being injected onto the molten metal pool. The constant temperature and constant heater input power conditions were adopted for the bottom heating. Test results showed that the temperature distribution and crust layer thickness in the metal layer are appreciably affected by the heated bottom surface temperature of the test section, but not much by the coolant injection rate. The relationship between the Nu number and Ra number in the molten metal pool region is determined and compared with the correlations in the literature, and the experiment without coolant boiling. A new correlation on the relationship between the Nu number and Ra number in the molten metal pool with crust formation is developed from the experimental data

Effect of pressure on heat transfer coefficient at the metal/mold interface of A356 aluminum alloy

DEFF Research Database (Denmark)

Fardi Ilkhchy, A.; Jabbari, Masoud; Davami, P.

2012-01-01

The aim of this paper is to correlate interfacial heat transfer coefficient (IHTC) to applied external pressure, in which IHTC at the interface between A356 aluminum alloy and metallic mold during the solidification of casting under different pressures were obtained using the inverse heat...... conduction problem (IHCP) method. The method covers the expedient of comparing theoretical and experimental thermal histories. Temperature profiles obtained from thermocouples were used in a finite difference heat flow program to estimate the transient heat transfer coefficients. The new simple formula...... was presented for correlation between external pressure and heat transfer coefficient. Acceptable agreement with data in literature shows the accuracy of the proposed formula....

Gas-solid heat exchange in a fibrous metallic material measured by a heat regenerator technique

NARCIS (Netherlands)

Golombok, M.; Jariwala, H.; Shirvill, C.

1990-01-01

The convective heat transfer properties of a porous metallic fibre material used in gas surface combustion burners are studied. The important parameter governing the heat transfer between hot gas and metal fibre—the heat transfer coefficient—is measured using a non-steady-state method based on

Natural convection and boiling heat transfer of a liquid metal in a magnetic field

International Nuclear Information System (INIS)

Seki, Masahiro; Kawamura, Hiroshi

1983-02-01

A liquid metal is often assumed as a coolant and a breeding material of a Tokamak fusion reactor. However, many problems on the thermo-hydraulics of a liquid metal in a magnetic field are still remained to be studied. In the present report, natural convection and boiling of a liquid metal in a strong magnetic field are studied to examine a fundamental feasibility of a fusion reactor cooled by a liquid metal. In the experimental study of the natural convection, the circulation of a liquid metal was found to be surpressed even by a magnetic field parallel to the gravity. A numerical study has confirmed the conclusion drawn by the experiment. In the study of boiling heat transfer, stable boiling of a liquid metal has been found also in a strong magnetic field. The burnout heat flux hardly affected by the magnetic field. These indicate a fundamental feasibility of the liquid-metal cooling for a Tokamak fusion reactor. (author)

Turbulent heavy liquid metal heat transfer along a heated rod in an annular cavity

International Nuclear Information System (INIS)

Lefhalm, C.-H.; Tak, N.-I.; Piecha, H.; Stieglitz, R.

2004-01-01

Heavy liquid metals (HLM) are considered as coolant and spallation material in accelerator driven systems (ADS), because of their good molecular heat conductivity. This property leads to a separation of the spatial extension of thermal and viscous boundary layers. Commercially available computational fluid dynamic codes (CFD) assume an analogy of momentum and energy transfer, which is problematic for liquid metals flow. Therefore, benchmark experiments are required, in order to validate codes or modify existing models used therein. Within this article an experimental and numerical study of a thermally developing turbulent lead bismuth (PbBi) flow along a uniformly heated rod in a circular tube is presented. Local temperatures and velocity distributions are measured using thermocouples and Pitot tubes. The data are compared to simulation results computed with the CFX code package. The measured velocity profiles coincide nearly perfect with the simulation results. However, discrepancies up to 7% between the measured and computed temperatures appear. A minor part of the deviations can be explained by the imperfect experimental set-up. But, the measured shape of the thermal boundary is different to the calculated one, indicating the inadequateness of the presently used models describing the turbulent heat transport within the thermal boundary layer

A Heat Transfer Model for a Stratified Corium-Metal Pool in the Lower Plenum of a Nuclear Reactor

International Nuclear Information System (INIS)

Sohal, M.S.; Siefken, L.J.

1999-01-01

This preliminary design report describes a model for heat transfer in a corium-metal stratified pool. It was decided to make use of the existing COUPLE model. Currently available correlations for natural convection heat transfer in a pool with and without internal heat generation were obtained. The appropriate correlations will be incorporated in the existing COUPLE model. Heat conduction and solidification modeling will be done with existing algorithms in the COUPLE. Assessment of the new model will be done by simple energy conservation problems

Effect of diameter of metal nanowires on pool boiling heat transfer with FC-72

Science.gov (United States)

Kumar G., Udaya; S., Suresh; M. R., Thansekhar; Babu P., Dinesh

2017-11-01

Effect of varying diameter of metal nanowires on pool boiling heat transfer performance is presented in this study. Copper nanowires (CuNWs) of four different diameters (∼35 nm, ∼70 nm, ∼130 nm and ∼200 nm) were grown directly on copper specimen using template-based electrodeposition technique. Both critical heat flux (CHF) and boiling heat transfer coefficient (h) were found to be improved in surfaces with nanowires as compared to the bare copper surface. Moreover, both the parameters were found to increase with increasing diameter of the nanowires. The percentage increases observed in CHF for the samples with nanowires were 38.37%, 40.16%, 48.48% and 45.57% whereas the percentage increase in the heat transfer coefficient were 86.36%, 95.45%, 184.1% and 131.82% respectively as compared to the bare copper surface. Important reasons believed for this enhancement were improvement in micron scale cavity density and cavity size which arises as a result of the coagulation and grouping of nanowires during the drying process. In addition to this, superhydrophilic nature, capillary effect, and enhanced bubble dynamics parameters (bubble frequency, bubble departure diameter, and nucleation site density) were found to be the concurring mechanisms responsible for this enhancement in heat transfer performance. Qualitative bubble dynamics analysis was done for the surfaces involved and the visual observations are provided to support the results presented and discussed.

Nanoparticle enhanced ionic liquid heat transfer fluids

Science.gov (United States)

Fox, Elise B.; Visser, Ann E.; Bridges, Nicholas J.; Gray, Joshua R.; Garcia-Diaz, Brenda L.

2014-08-12

A heat transfer fluid created from nanoparticles that are dispersed into an ionic liquid is provided. Small volumes of nanoparticles are created from e.g., metals or metal oxides and/or alloys of such materials are dispersed into ionic liquids to create a heat transfer fluid. The nanoparticles can be dispersed directly into the ionic liquid during nanoparticle formation or the nanoparticles can be formed and then, in a subsequent step, dispersed into the ionic liquid using e.g., agitation.

Natural convection heat transfer from a horizontal cylinder in liquid sodium. Pt. 2. Generalized correlation for laminar natural convection heat transfer

International Nuclear Information System (INIS)

Hata, K.; Takeuchi, Y.

1999-01-01

For pt.I see ibid., vol.193, p.105-18, 1999. Rigorous numerical solution of natural convection heat transfer, from a horizontal cylinder with uniform surface heat flux or with uniform surface temperature, to liquid sodium was derived by solving the fundamental equations for laminar natural convection heat transfer without the boundary layer approximation. It was made clear that the local and average Nusselt numbers experimentally obtained and reported in part 1 of this paper were described well by the numerical solutions for uniform surface heat fluxes, but that those for uniform surface temperatures could not describe the angular distribution of the local Nusselt numbers and about 10% underpredicted the average Nusselt numbers. Generalized correlation for natural convection heat transfer from a horizontal cylinder with a uniform surface heat flux in liquid metals was presented based on the rigorous theoretical values for a wide range of Rayleigh numbers. It was confirmed that the correlation can describe the authors' and other workers' experimental data on horizontal cylinders in various kinds of liquid metals for a wide range of Rayleigh numbers. Another correlation for a horizontal cylinder with a uniform surface temperature in liquid metals, which may be applicable for special cases such as natural convection heat transfer in a sodium-to-sodium heat exchanger etc. was also presented based on the rigorous theoretical values for a wide range of Rayleigh numbers. These correlations can also describe the rigorous numerical solutions for non-metallic liquids and gases for the Prandtl numbers up to 10. (orig.)

Heat transfer between adsorbate and laser-heated hot electrons

International Nuclear Information System (INIS)

Ueba, H; Persson, B N J

2008-01-01

Strong short laser pulses can give rise to a strong increase in the electronic temperature at metal surfaces. Energy transfer from the hot electrons to adsorbed molecules may result in adsorbate reactions, e.g. desorption or diffusion. We point out the limitations of an often used equation to describe the heat transfer process in terms of a friction coupling. We propose a simple theory for the energy transfer between the adsorbate and hot electrons using a newly introduced heat transfer coefficient, which depends on the adsorbate temperature. We calculate the transient adsorbate temperature and the reaction yield for a Morse potential as a function of the laser fluency. The results are compared to those obtained using a conventional heat transfer equation with temperature-independent friction. It is found that our equation of energy (heat) transfer gives a significantly lower adsorbate peak temperature, which results in a large modification of the reaction yield. We also consider the heat transfer between different vibrational modes excited by hot electrons. This mode coupling provides indirect heating of the vibrational temperature in addition to the direct heating by hot electrons. The formula of heat transfer through linear mode-mode coupling of two harmonic oscillators is applied to the recent time-resolved study of carbon monoxide and atomic oxygen hopping on an ultrafast laser-heated Pt(111) surface. It is found that the maximum temperature of the frustrated translation mode can reach high temperatures for hopping, even when direct friction coupling to the hot electrons is not strong enough

Parametric investigation on transient boiling heat transfer of metal rod cooled rapidly in water pool

Energy Technology Data Exchange (ETDEWEB)

Lee, Chi Young [Department of Fire Protection Engineering, Pukyong National University, 45, Yongso-ro, Nam-gu, Busan 48513 (Korea, Republic of); Kim, Sunwoo, E-mail: swkim@alaska.edu [Mechanical Engineering Department, University of Alaska Fairbanks, P. O. Box 755905, Fairbanks, AK 99775-5905 (United States)

2017-03-15

Highlights: • Effects of liquid subcooling, surface coating, material property, and surface oxidation are examined. • Liquid subcooling affects remarkably the quenching phenomena. • Cr-coated surfaces for ATF might extend the quenching duration. • Solids with low heat capacity shorten the quenching duration. • Surface oxidation can affect strongly the film boiling heat transfer and MFB point. - Abstract: In this work, the effects of liquid subcooling, surface coating, material property, and surface oxidation on transient pool boiling heat transfer were investigated experimentally using the vertical metal rod and quenching method. The change in rod temperature was measured with time during quenching, and the visualization of boiling around the test specimen was performed using the high-speed video camera. As the test materials, the zircaloy (Zry), stainless steel (SS), niobium (Nb), and copper (Cu) were tested. In addition, the chromium-coated niobium (Cr-Nb) and chromium-coated stainless steel (Cr-SS) were prepared for accident tolerant fuel (ATF) application. Low liquid subcooling and Cr-coating shifted the quenching curve to the right, which indicates a prolongation of quenching duration. On the other hand, the material with small heat capacity and surface oxidation caused the quenching curve to move to the left. To examine the influence of the material property and surface oxidation on the film boiling heat transfer performance and minimum film boiling (MFB) point in more detail, the wall temperature and heat flux were calculated from the present transient temperature profile using the inverse heat transfer analysis, and then the curves of wall temperature and heat flux in the film boiling regime were obtained. In the present experimental conditions, the effect of material property on the film boiling heat transfer performance and MFB point seemed to be minor. On the other hand, based on the experimental results of the Cu test specimen, the surface

Heat transfer in heterogeneous propellant combustion systems

International Nuclear Information System (INIS)

Brewster, M.Q.

1992-01-01

This paper reports that heat transfer plays an important role in several critical areas of heterogeneous, solid-propellant combustion systems. These areas include heat feedback to the propellant surface, heat transfer between burning aluminum droplets and their surroundings, heat transfer to internal insulation systems, and heat transfer to aft-end equipment. Gas conduction dominates heat feedback to the propellant surface in conventional ammonium perchlorate (AP) composite propellants, although particle radiative feedback also plays a significant role in combustion of metalized propellants. Particle radiation plays a dominant role in heat transfer to internal insulation, compared with that of convection. However, conduction by impingement of burning aluminum particles, which has not been extensively studied, may also be significant. Radiative heat loss plays an important role in determining the burning rate of molten aluminum particles due to a highly luminous, oxide particle-laden, detached flame envelope. Radiation by aluminum oxide smoke particles also plays a dominant role in heat transfer from the exhaust plume to aft-end equipment. Uncertainties in aluminum oxide particle-size distribution and optical properties still make it difficult to predict radiative plume heat transfer accurately from first principles

Full-scale prototyping of the Hitachi dual-purpose metal cask and verification of its heat transfer characteristics

International Nuclear Information System (INIS)

Kumagai, N.; Ishida, N.; Ootsuka, M.; Kamoshida, M.; Hiranuma, T.; Doumori, S.; Hoshikawa, T.; Shimizu, M.; Kashiwakura, J.; Hayashi, M.

2004-01-01

Hitachi has been developing dual-purpose metal casks for transport and storage of spent nuclear fuels. The Hitachi cask, HDP69B can store 69 BWR fuel assemblies. The cask features are as follows. 1) The fuel basket is assembled mainly with plates of borated stainless steel. The plates are not welded, but cross-inserted into each other like the dividers in an egg carton. Since the borated stainless steel has relatively low heat conductivity, aluminum alloy plates are inserted along with some stainless steel plates to enhance heat removal ability. 2) Cured resin blocks are fitted into the inner shell of the cask for neutron shielding of the cask body. The resin blocks are surrounded by an aluminum casing which transfers heat of stored fuel from the inner shell to the outer shell of the cask. The block type shield structure eliminates the need for welding the heat transfer fins to the inner and outer shells. The weldless structures of the HDP69B lead to its enhanced manufacturability, but they complicate the heat transfer characteristics because there are gaps between such components as the aluminum casing and inner/outer shells. We carried out full-scale prototyping of the HDP69B and ran a heat transfer test using the prototype. The purposes of the heat transfer test were to check the heat removal ability of the HDP69B and to verify the safety analysis model for heat removal. Results of the heat transfer test and optimized analysis model for heat transfer characteristics of the HDP69B are the focus of this paper. The heat transfer test is summarized as follows. Sixty nine heaters simulating the shape and heat power of spent fuel assemblies were inserted into the fuel basket. After replacing the inner atmosphere with 0.1 MPa of helium, the heat transfer test was started. About 7 days were required to equilibrate the temperature distribution. The temperature at the center of the basket was 194 C. The results confirmed the HDP69B had sufficient heat removal ability. The

Study on interfacial heat transfer coefficient at metal/die interface during high pressure die casting process of AZ91D alloy

Directory of Open Access Journals (Sweden)

GUO Zhi-peng

2007-02-01

Full Text Available The high pressure die casting (HPDC process is one of the fastest growing and most efficient methods for the production of complex shape castings of magnesium and aluminum alloys in today’s manufacturing industry.In this study, a high pressure die casting experiment using AZ91D magnesium alloy was conducted, and the temperature profiles inside the die were Measured. By using a computer program based on solving the inverse heat problem, the metal/die interfacial heat transfer coefficient (IHTC was calculated and studied. The results show that the IHTC between the metal and die increases right after the liquid metal is brought into the cavity by the plunger,and decreases as the solidification process of the liquid metal proceeds until the liquid metal is completely solidified,when the IHTC tends to be stable. The interfacial heat transfer coefficient shows different characteristics under different casting wall thicknesses and varies with the change of solidification behavior.

Conjugate heat transfer analysis for in-vessel retention with external reactor vessel cooling

International Nuclear Information System (INIS)

Park, Jong-Woon; Bae, Jae-ho; Song, Hyuk-Jin

2016-01-01

Highlights: • A conjugate heat transfer analysis method is applied for in-vessel corium retention. • 3D heat diffusion has a formidable effect in alleviating focusing heat load from metallic layer. • The focusing heat load is decreased by about 2.5 times on the external surface. - Abstract: A conjugate heat transfer analysis method for the thermal integrity of a reactor vessel under external reactor vessel cooling conditions is developed to resolve light metal layer focusing effect issue for in-vessel retention. The method calculates steady-state three-dimensional temperature distribution of a reactor vessel using coupled conjugate heat transfer between in-vessel three-layered stratified corium (metallic pool, oxide pool and heavy metal and polar-angle dependent boiling heat transfer at the outer surface of a reactor vessel). The three-layer corium heat transfer model is utilizing lumped-parameter thermal-resistance circuit method. For the ex-vessel boiling boundary conditions, nucleate, transition and film boiling are considered. The thermal integrity of a reactor vessel is addressed in terms of heat flux at the outer-most nodes of the vessel and remaining thickness profile. The vessel three-dimensional heat conduction is validated against a commercial code. It is found that even though the internal heat flux from the metal layer goes far beyond critical heat flux (CHF) the heat flux from the outermost nodes of the vessel may be maintained below CHF due to massive vessel heat diffusion. The heat diffusion throughout the vessel is more pronounced for relatively low heat generation rate in an oxide pool. Parametric calculations are performed considering thermal conditions such as peak heat flux from a light metal layer, heat generation in an oxide pool and external boiling conditions. The major finding is that the most crucial factor for success of in-vessel retention is not the mass of the molten light metal above the oxide pool but the heat generation rate

Phase change heat transfer device for process heat applications

International Nuclear Information System (INIS)

Sabharwall, Piyush; Patterson, Mike; Utgikar, Vivek; Gunnerson, Fred

2010-01-01

The next generation nuclear plant (NGNP) will most likely produce electricity and process heat, with both being considered for hydrogen production. To capture nuclear process heat, and transport it to a distant industrial facility requires a high temperature system of heat exchangers, pumps and/or compressors. The heat transfer system is particularly challenging not only due to the elevated temperatures (up to ∼1300 K) and industrial scale power transport (≥50 MW), but also due to a potentially large separation distance between the nuclear and industrial plants (100+ m) dictated by safety and licensing mandates. The work reported here is the preliminary analysis of two-phase thermosyphon heat transfer performance with alkali metals. A thermosyphon is a thermal device for transporting heat from one point to another with quite extraordinary properties. In contrast to single-phased forced convective heat transfer via 'pumping a fluid', a thermosyphon (also called a wickless heat pipe) transfers heat through the vaporization/condensing process. The condensate is further returned to the hot source by gravity, i.e., without any requirement of pumps or compressors. With this mode of heat transfer, the thermosyphon has the capability to transport heat at high rates over appreciable distances, virtually isothermally and without any requirement for external pumping devices. Two-phase heat transfer by a thermosyphon has the advantage of high enthalpy transport that includes the sensible heat of the liquid, the latent heat of vaporization, and vapor superheat. In contrast, single-phase forced convection transports only the sensible heat of the fluid. Additionally, vapor-phase velocities within a thermosyphon are much greater than single-phase liquid velocities within a forced convective loop. Thermosyphon performance can be limited by the sonic limit (choking) of vapor flow and/or by condensate entrainment. Proper thermosyphon requires analysis of both.

Numerical study of metal foam heat sinks under uniform impinging flow

International Nuclear Information System (INIS)

Andreozzi, A; Bianco, N; Iasiello, M; Naso, V

2017-01-01

The ever-increasing demand for performance improvement and miniaturization of electronics has led to a significant generation of waste heat that must be dissipated to ensure a reliable device operation. The miniaturization of the components complicates this task. In fact, reducing the heat transfer area, at the same required heat rate, it is necessary to increase the heat flux, so that the materials operate in a temperature range suitable to its proper functioning. Traditional heat sinks are no longer capable of dissipating the generated heat and innovative approaches are needed to address the emerging thermal management challenges. Recently, heat transfer in open-cell metal foams under an impinging jet has received attention due to the considerable heat transfer potential of combining two cooling technologies: impinging jet and porous medium. This paper presents a numerical study on Finned Metal Foam (FMF) and Metal Foam (MF) heat sinks under impinging air jet cooling. The analysis is carried out by means of the commercial software COMSOL Multiphysics®. The purpose is to analyze the thermal performance of the metal foam heat sink, finned or not, varying its geometric parameters. Results are presented in terms of predicted dissipated heat rate, convective heat transfer coefficient and pressure losses. (paper)

Heat transfer

International Nuclear Information System (INIS)

Saad, M.A.

1985-01-01

Heat transfer takes place between material systems as a result of a temperature difference. The transmission process involves energy conversions governed by the first and second laws of thermodynamics. The heat transfer proceeds from a high-temperature region to a low-temperature region, and because of the finite thermal potential, there is an increase in entropy. Thermodynamics, however, is concerned with equilibrium states, which includes thermal equilibrium, irrespective of the time necessary to attain these equilibrium states. But heat transfer is a result of thermal nonequilibrium conditions, therefore, the laws of thermodynamics alone cannot describe completely the heat transfer process. In practice, most engineering problems are concerned with the rate of heat transfer rather than the quantity of heat being transferred. Resort then is directed to the particular laws governing the transfer of heat. There are three distinct modes of heat transfer: conduction, convection, and radiation. Although these modes are discussed separately, all three types may occur simultaneously

Numerical Analysis of Heat Transfer During Quenching Process

Science.gov (United States)

Madireddi, Sowjanya; Krishnan, Krishnan Nambudiripad; Reddy, Ammana Satyanarayana

2018-04-01

A numerical model is developed to simulate the immersion quenching process of metals. The time of quench plays an important role if the process involves a defined step quenching schedule to obtain the desired characteristics. Lumped heat capacity analysis used for this purpose requires the value of heat transfer coefficient, whose evaluation requires large experimental data. Experimentation on a sample work piece may not represent the actual component which may vary in dimension. A Fluid-Structure interaction technique with a coupled interface between the solid (metal) and liquid (quenchant) is used for the simulations. Initial times of quenching shows boiling heat transfer phenomenon with high values of heat transfer coefficients (5000-2.5 × 105 W/m2K). Shape of the work piece with equal dimension shows less influence on the cooling rate Non-uniformity in hardness at the sharp corners can be reduced by rounding off the edges. For a square piece of 20 mm thickness, with 3 mm fillet radius, this difference is reduced by 73 %. The model can be used for any metal-quenchant combination to obtain time-temperature data without the necessity of experimentation.

Validation of ANSYS CFX for gas and liquid metal flows with conjugate heat transfer within the European project THINS

Energy Technology Data Exchange (ETDEWEB)

Papukchiev, A., E-mail: angel.papukchiev@grs.de; Buchholz, S.

2017-02-15

Highlights: • ANSYS CFX is validated for gas and liquid metal flows. • L-STAR and TALL-3D experiments are simulated. • Complex flow and heat transfer phenomena are modelled. • Conjugate heat transfer has to be considered in CFD analyses. - Abstract: Within the FP7 European project THINS (Thermal Hydraulics of Innovative Nuclear Systems), numerical tools for the simulation of the thermal-hydraulics of next generation rector systems were developed, applied and validated for innovative coolants. The Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) gGmbH participated in THINS with activities related to the development and validation of computational fluid dynamics (CFD) and coupled System Thermal Hydraulics (STH) – CFD codes. High quality measurements from the L-STAR and TALL-3D experiments were used to assess the numerical results. Two-equation eddy viscosity and scale resolving turbulence models were used in the validation process of ANSYS CFX for gas and liquid metal flows with conjugate heat transfer. This paper provides a brief overview on the main results achieved at GRS within the project.

Thermochemistry of ionic liquid heat-transfer fluids

International Nuclear Information System (INIS)

Van Valkenburg, Michael E.; Vaughn, Robert L.; Williams, Margaret; Wilkes, John S.

2005-01-01

Large-scale solar energy collectors intended for electric power generation require a heat-transfer fluid with a set of properties not fully met by currently available commercial materials. Ionic liquids have thermophysical and chemical properties that may be suitable for heat transfer and short heat term storage in power plants using parabolic trough solar collectors. Ionic liquids are salts that are liquid at or near room temperature. Thermal properties important for heat transfer applications are melting point, boiling point, liquidus range, heat capacity, heat of fusion, vapor pressure, and thermal conductivity. Other properties needed to evaluate the usefulness of ionic liquids are density, viscosity and chemical compatibility with certain metals. Three ionic liquids were chosen for study based on their range of solvent properties. The solvent properties correlate with solubility of water in the ionic liquids. The thermal and chemical properties listed above were measured or compiled from the literature. Contamination of the ionic liquids by impurities such as water, halides, and metal ions often affect physical properties. The ionic liquids were analyzed for those impurities, and the impact of the contamination was evaluated by standard addition. The conclusion is that the ionic liquids have some very favorable thermal properties compared to targets established by the Department of Energy for solar collector applications

Laboratory simulation of heat exchange for liquids with Pr > 1: Heat transfer

Science.gov (United States)

Belyaev, I. A.; Zakharova, O. D.; Krasnoshchekova, T. E.; Sviridov, V. G.; Sukomel, L. A.

2016-02-01

Liquid metals are promising heat transfer agents in new-generation nuclear power plants, such as fast-neutron reactors and hybrid tokamaks—fusion neutron sources (FNSs). We have been investigating hydrodynamics and heat exchange of liquid metals for many years, trying to reproduce the conditions close to those in fast reactors and fusion neutron sources. In the latter case, the liquid metal flow takes place in a strong magnetic field and strong thermal loads resulting in development of thermogravitational convection in the flow. In this case, quite dangerous regimes of magnetohydrodynamic (MHD) heat exchange not known earlier may occur that, in combination with other long-known regimes, for example, the growth of hydraulic drag in a strong magnetic field, make the possibility of creating a reliable FNS cooling system with a liquid metal heat carrier problematic. There exists a reasonable alternative to liquid metals in FNS, molten salts, namely, the melt of lithium and beryllium fluorides (Flibe) and the melt of fluorides of alkali metals (Flinak). Molten salts, however, are poorly studied media, and their application requires detailed scientific substantiation. We analyze the modern state of the art of studies in this field. Our contribution is to answer the following question: whether above-mentioned extremely dangerous regimes of MHD heat exchange detected in liquid metals can exist in molten salts. Experiments and numerical simulation were performed in order to answer this question. The experimental test facility represents a water circuit, since water (or water with additions for increasing its electrical conduction) is a convenient medium for laboratory simulation of salt heat exchange in FNS conditions. Local heat transfer coefficients along the heated tube, three-dimensional (along the length and in the cross section, including the viscous sublayer) fields of averaged temperature and temperature pulsations are studied. The probe method for measurements in

Heat transfer coefficient for lead matrixing in disposal containers for used reactor fuel

International Nuclear Information System (INIS)

Mathew, P.M.; Taylor, M.; Krueger, P.A.

1985-02-01

In the Canadian Nuclear Fuel Waste Management Program, metal matrices with low melting points are being evaluated for their potential to provide support for the shell of disposal containers for used fuel, and to act as an additional barrier to the release of radionuclides. The metal matrix would be incorporated into the container by casting. To study the heat transfer processes during solidification, a steady-state technique was used, involving lead as the cast metal, to determine the overall heat transfer coefficient between the lead and some of the candidate container materials. The existence of an air gap between the cast lead and the container material appeared to control the overall heat transfer coefficient. The experimental observations indicated that the surface topography of the container material influences the heat transfer and that a smoother surface results in a greater heat transfer than a rough surface. The experimental results also showed an increasing heat transfer coefficient with increasing temperature difference across the container base plates; a model developed to base-plate bending can explain the observed results

Numerical simulation of the heat transfer at cooling a high-temperature metal cylinder by a flow of a gas-liquid medium

Science.gov (United States)

Makarov, S. S.; Lipanov, A. M.; Karpov, A. I.

2017-10-01

The numerical modeling results for the heat transfer during cooling a metal cylinder by a gas-liquid medium flow in an annular channel are presented. The results are obtained on the basis of the mathematical model of the conjugate heat transfer of the gas-liquid flow and the metal cylinder in a two-dimensional nonstationary formulation accounting for the axisymmetry of the cooling medium flow relative to the cylinder longitudinal axis. To solve the system of differential equations the control volume approach is used. The flow field parameters are calculated by the SIMPLE algorithm. To solve iteratively the systems of linear algebraic equations the Gauss-Seidel method with under-relaxation is used. The results of the numerical simulation are verified by comparing the results of the numerical simulation with the results of the field experiment. The calculation results for the heat transfer parameters at cooling the high-temperature metal cylinder by the gas-liquid flow are obtained with accounting for evaporation. The values of the rate of cooling the cylinder by the laminar flow of the cooling medium are determined. The temperature change intensity for the metal cylinder is analyzed depending on the initial velocity of the liquid flow and the time of the cooling process.

Heat transfer enhancement

International Nuclear Information System (INIS)

Hasatani, Masanobu; Itaya, Yoshinori

1985-01-01

In order to develop energy-saving techniques and new energy techniques, and also most advanced techniques by making industrial equipment with high performance, heat transfer performance frequently becomes an important problem. In addition, the improvement of conventional heat transfer techniques and the device of new heat transfer techniques are often required. It is most proper that chemical engineers engage in the research and development for enhancing heat transfer. The research and development for enhancing heat transfer are important to heighten heat exchange efficiency or to cool equipment for preventing overheat in high temperature heat transfer system. In this paper, the techniques of enhancing radiative heat transfer and the improvement of radiative heat transfer characteristics are reported. Radiative heat transfer is proportional to fourth power of absolute temperature, and it does not require any heat transfer medium, but efficient heat-radiation converters are necessary. As the techniques of enhancing radiative heat transfer, the increase of emission and absorption areas, the installation of emissive structures and the improvement of radiative characteristics are discussed. (Kako, I.)

Heat transfer in the thermal entrance region of a circular tube with axial heat conduction

International Nuclear Information System (INIS)

Zhang Changquan.

1985-01-01

This paper recounts the effects of axial heat conduction and convective boundary conditions on the heat transfer in the thermal entrance region of a circular tube under uniform flow, and the corresponding calculation is made. It will be profitable for the heat transfer studies on the pipe entrance region of low Prandtl number (liquid metal), or flow of low Peclet number. (author)

Cryogenic heat transfer

CERN Document Server

Barron, Randall F

2016-01-01

Cryogenic Heat Transfer, Second Edition continues to address specific heat transfer problems that occur in the cryogenic temperature range where there are distinct differences from conventional heat transfer problems. This updated version examines the use of computer-aided design in cryogenic engineering and emphasizes commonly used computer programs to address modern cryogenic heat transfer problems. It introduces additional topics in cryogenic heat transfer that include latent heat expressions; lumped-capacity transient heat transfer; thermal stresses; Laplace transform solutions; oscillating flow heat transfer, and computer-aided heat exchanger design. It also includes new examples and homework problems throughout the book, and provides ample references for further study.

Heat transfer

Indian Academy of Sciences (India)

First page Back Continue Last page Overview Graphics. Heat transfer. Heat conduction in solid slab. Convective heat transfer. Non-linear temperature. variation due to flow. HEAT FLUX AT SURFACE. conduction/diffusion.

Local heat transfer where heated rods touch in axially flowing water

International Nuclear Information System (INIS)

Kast, S.J.

1983-05-01

An anlaytic model is developed to predict the azimuthal width of a stablesteam blanket region near the line of contact between two heated rods cooled by axially flowing water at high pressure. The model is intended to aid analysis of reduced surface heat transfer capability for the abnormal configuration of nuclear fuel rods bowed into contact in the core of a pressurized water nuclear reactor. The analytic model predicts the azimuthal width of the steam blanket zone having reduced surface heat transfer as a function of rod average heat flux, subchannel coolant conditions and rod dimensions. The analytic model is developed from a heat balance between the heat generated in the wall of a heated empty tube and the heat transported away by transverse mixing and axial convection in the coolant subchannel. The model is developed for seveal geometries including heated rods in line contact, a heated rod touching a short insulating plane and a heated rod touching the inside of a metal guide tube

METAL CHIP HEATING PROCESS INVESTIGATION (Part I

Directory of Open Access Journals (Sweden)

O. M. Dyakonov

2007-01-01

Full Text Available The main calculation methods for heat- and mass transfer in porous heterogeneous medium have been considered. The paper gives an evaluation of the possibility to apply them for calculation of metal chip heating process. It has been shown that a description of transfer processes in a chip has its own specific character that is attributed to difference between thermal and physical properties of chip material and lubricant-coolant components on chip surfaces. It has been determined that the known expressions for effective heat transfer coefficients can be used as basic ones while approaching mutually penetrating continuums. A mathematical description of heat- and mass transfer in chip medium can be considered as a basis of mathematical modeling, numerical solution and parameter optimization of the mentioned processes.

A study of the flow boiling heat transfer in an annular heat exchanger with a mini gap

Directory of Open Access Journals (Sweden)

Musiał Tomasz

2017-01-01

Full Text Available In this paper the research on flow boiling heat transfer in an annular mini gap was discussed. A one- dimensional mathematical approach was proposed to describe stationary heat transfer in the gap. The mini gap 1 mm wide was created between a metal pipe with enhanced exterior surface and an external tempered glass pipe positioned along the same axis. The experimental test stand consists of several systems: the test loop in which distilled water circulates, the data and image acquisition system and the supply and control system. Known temperature distributions of the metal pipe with enhanced surface and of the working fluid helped to determine, from the Robin boundary condition, the local heat transfer coefficients at the fluid - heated surface contact. In the proposed mathematical model it is assumed that the cylindrical wall is a planar multilayer wall. The numerical results are presented on a chart as function of the heat transfer coefficient along the length of the mini gap.

Numerical study of turbulent heat transfer along a heated rod in an annular cavity

International Nuclear Information System (INIS)

Batta, A.; Class, A.; Daubner, M.; Gnieser, S.; Stieglitz, R.

2008-01-01

Fundamental knowledge on the turbulent convective heat transfer from a rod into liquid metal is of crucial importance for the design of advanced liquid metal operated nuclear systems since a single rod is the basic element of a fuel rod assembly. Therefore, a numerical investigation of the heated rod experiment at KALLA (KArlsruhe Liquid metal LAboratory) has been performed. This experiment investigates the turbulent heat transfer from a heated rod placed concentrically within in a cylindrical tube in a developing flow of a heavy liquid metal (HLM, here Pb 45 Bi 55 Eutectic) at reactor typical power levels and dimensions. It is set up with thermocouples (TCs), a traversable Pitot tube and three thermocouple rakes consisting of numerous thermocouples (TCs). The concentricity is ensured by means of mechanical spacers placed axially equidistant. This article concentrates on the numerical investigation of the impact of the experimental instrumentation on the developing flow pattern and temperature field. In particular, the influence of spacers which distort the velocity profile as well of a potential contact of the spacer with the heated rod changing the heat conduction regime are considered numerically in this paper using the STAR-CD code. The turbulent flow simulation assumes axis-symmetry and uses the SST turbulence model. The simulation results exhibit a flow pattern that is substantially altered by spacers. Hence, the flow can not be considered to be axis-symmetric. This in turn yields that the convective heat transfer from the heated rod towards the spacer region is reduced leading to a temperature rise in spacer region, which represents the maximum value in this domain. As a consequence the entire three-dimensional test section must be modelled in order to correctly represent the physics and to allow an adequate interpretation of the experimental data. (orig.)

Near-field radiative heat transfer between metasurfaces

DEFF Research Database (Denmark)

Dai, Jin; Dyakov, Sergey A.; Bozhevolnyi, Sergey I.

2016-01-01

Metamaterials possess artificial bulk and surface electromagnetic states. Tamed dispersion properties of surface waves allow one to achieve a controllable super-Planckian radiative heat transfer (RHT) process between two closely spaced objects. We numerically demonstrate enhanced RHT between two...... and highly geometrically tailorable. Our simulation also reveals thermally excited nonresonant surface waves in constituent metallic materials may play a prevailing role for RHT at an extremely small separation between two metal plates, rendering metamaterial modes insignificant for the energy-transfer...

Alkali Metal Heat Pipe Life Issues

International Nuclear Information System (INIS)

Reid, Robert S.

2004-01-01

One approach to fission power system design uses alkali metal heat pipes for the core primary heat-transfer system. Heat pipes may also be used as radiator elements or auxiliary thermal control elements. This synopsis characterizes long-life core heat pipes. References are included where information that is more detailed can be found. Specifics shown here are for demonstration purposes and do not necessarily reflect current Nasa Project Prometheus point designs. (author)

Measurement and modeling of interface heat transfer coefficients

International Nuclear Information System (INIS)

Rollett, A.D.; Lewis, H.D.; Dunn, P.S.

1985-01-01

The results of preliminary work on the modeling and measurement of the heat transfer coefficients of metal/mold interfaces is reported. The system investigated is the casting of uranium in graphite molds. The motivation for the work is primarily to improve the accuracy of process modeling of prototype mold designs at the Los Alamos Foundry. The evolution in design of a suitable mold for unidirectional solidification is described, illustrating the value of simulating mold designs prior to use. Experiment indicated a heat transfer coefficient of 2 kW/m 2 /K both with and without superheat. It was possible to distinguish between solidification due to the mold and that due to radiative heat loss. This permitted an experimental estimate of the emissivity, epsilon = 0.2, of the solidified metal

Continuum simulation of heat transfer and solidification behavior of AlSi10Mg in Direct Metal Laser Sintering Process

Science.gov (United States)

Ojha, Akash; Samantaray, Mihir; Nath Thatoi, Dhirendra; Sahoo, Seshadev

2018-03-01

Direct Metal Laser Sintering (DMLS) process is a laser based additive manufacturing process, which built complex structures from powder materials. Using high intensity laser beam, the process melts and fuse the powder particles makes dense structures. In this process, the laser beam in terms of heat flux strikes the powder bed and instantaneously melts and joins the powder particles. The partial solidification and temperature distribution on the powder bed endows a high cooling rate and rapid solidification which affects the microstructure of the build part. During the interaction of the laser beam with the powder bed, multiple modes of heat transfer takes place in this process, that make the process very complex. In the present research, a comprehensive heat transfer and solidification model of AlSi10Mg in direct metal laser sintering process has been developed on ANSYS 17.1.0 platform. The model helps to understand the flow phenomena, temperature distribution and densification mechanism on the powder bed. The numerical model takes into account the flow, heat transfer and solidification phenomena. Simulations were carried out for sintering of AlSi10Mg powders in the powder bed having dimension 3 mm × 1 mm × 0.08 mm. The solidification phenomena are incorporated by using enthalpy-porosity approach. The simulation results give the fundamental understanding of the densification of powder particles in DMLS process.

Natural convection heat transfer experiments of horizontal plates with fin arrays

Energy Technology Data Exchange (ETDEWEB)

Moon, Je Young; Chung, Bum Jin [Jeju National University 102 Jejudaehakno, Jeju (Korea, Republic of)

2012-10-15

Core melt in a severe accident condition, forms a molten pool in the reactor vessel lower head. The molten pool is divided by a metallic pool (top) and an oxide pool (bottom) by the density difference. The crust between the metallic layer and the oxide pool may be formed by solidification of the molten metallic materials. So the surface of the crust is formed irregularly. Experiments were performed to investigate the irregular crust as a preparatory study before an in-depth severe accident study. The natural convection heat transfer were investigated experimentally varying the height and spacing of fins, top plate of different kinds and the plate separation distance with/without the side walls. In order to simulate irregular crust surface condition, the finned plates was used. Using the analogy concept, heat transfer experiments were replaced by mass transfer experiments. A cupric acid.copper sulfate (H{sup 2S}O{sup 4-}CuSO{sup 4)} electroplating system was adopted as the mass transfer system and the electric currents were measured rather than the heat transfer rates.

Heat transfer analysis of parabolic trough solar receiver

International Nuclear Information System (INIS)

Padilla, Ricardo Vasquez; Demirkaya, Gokmen; Goswami, D. Yogi; Stefanakos, Elias; Rahman, Muhammad M.

2011-01-01

Highlights: → In this paper a detailed one dimensional numerical heat transfer analysis of a PTC is performed. → The receiver and envelope were divided into several segments and mass and energy balance were applied in each segment. → Improvements either in the heat transfer correlations or radiative heat transfer analysis are presented. → The proposed heat transfer model was validated with experimental data obtained from Sandia National Laboratory. → Our results showed a better agreement with experimental data compared to other models. -- Abstract: Solar Parabolic Trough Collectors (PTCs) are currently used for the production of electricity and applications with relatively higher temperatures. A heat transfer fluid circulates through a metal tube (receiver) with an external selective surface that absorbs solar radiation reflected from the mirror surfaces of the PTC. In order to reduce the heat losses, the receiver is covered by an envelope and the enclosure is usually kept under vacuum pressure. The heat transfer and optical analysis of the PTC is essential to optimize and understand its performance under different operating conditions. In this paper a detailed one dimensional numerical heat transfer analysis of a PTC is performed. The receiver and envelope were divided into several segments and mass and energy balance were applied in each segment. Improvements either in the heat transfer correlations or radiative heat transfer analysis are presented as well. The partial differential equations were discretized and the nonlinear algebraic equations were solved simultaneously. Finally, to validate the numerical results, the model was compared with experimental data obtained from Sandia National Laboratory (SNL) and other one dimensional heat transfer models. Our results showed a better agreement with experimental data compared to other models.

Convective heat transfer

CERN Document Server

Kakac, Sadik; Pramuanjaroenkij, Anchasa

2014-01-01

Intended for readers who have taken a basic heat transfer course and have a basic knowledge of thermodynamics, heat transfer, fluid mechanics, and differential equations, Convective Heat Transfer, Third Edition provides an overview of phenomenological convective heat transfer. This book combines applications of engineering with the basic concepts of convection. It offers a clear and balanced presentation of essential topics using both traditional and numerical methods. The text addresses emerging science and technology matters, and highlights biomedical applications and energy technologies. What’s New in the Third Edition: Includes updated chapters and two new chapters on heat transfer in microchannels and heat transfer with nanofluids Expands problem sets and introduces new correlations and solved examples Provides more coverage of numerical/computer methods The third edition details the new research areas of heat transfer in microchannels and the enhancement of convective heat transfer with nanofluids....

Heat transfer and mechanical interactions in fusion nuclear systems

International Nuclear Information System (INIS)

Nygren, R.E.

1984-01-01

This general review of design issues in heat transfer and mechanical interactions of the first wall, blanket and shield systems of tokamak and mirror fusion reactors begins with a brief introduction to fusion nuclear systems. The design issues are summarized in tables and the following examples are described to illustrate these concerns: the surface heating of limiters, heat transfer from solid breeders, MHD effects in liquid metal blankets, mechanical loads from electromagnetic transients and remote maintenance

Heat transfer: Pittsburgh 1987

International Nuclear Information System (INIS)

Lyczkowski, R.W.

1987-01-01

This book contains papers divided among the following sections: Process Heat Transfer; Thermal Hydraulics and Phase Change Phenomena; Analysis of Multicomponent Multiphase Flow and Heat Transfer; Heat Transfer in Advanced Reactors; General Heat Transfer in Solar Energy; Numerical Simulation of Multiphase Flow and Heat Transfer; High Temperature Heat Transfer; Heat Transfer Aspects of Severe Reactor Accidents; Hazardous Waste On-Site Disposal; and General Papers

Integrated conjugate heat transfer analysis method for in-vessel retention with external reactor vessel cooling - 15477

International Nuclear Information System (INIS)

Park, J.W.; Bae, J.H.; Seol, W.C.

2015-01-01

An integrated conjugate heat transfer analysis method for the thermal integrity of a reactor vessel under external reactor vessel cooling conditions is developed to resolve light metal layer focusing effect issue. The method calculates steady-state 3-dimensional temperature distribution of a reactor vessel using coupled conjugate heat transfer between in-vessel 3-layered stratified corium (metallic pool, oxide pool and heavy metal) and polar-angle dependent boiling heat transfer at the outer surface of a reactor vessel. The 3-layer corium heat transfer model is utilizing lumped-parameter thermal-resistance circuit method and ex-vessel boiling regimes are parametrically considered. The thermal integrity of a reactor vessel is addressed in terms of un-molten thickness profile. The vessel 3-dimensional heat conduction is validated against a commercial code. It is found that even though the internal heat flux from the metal layer goes far beyond critical heat flux (CHF) the heat flux from the outermost nodes of the vessel may be maintained below CHF due to massive vessel heat diffusion. The heat diffusion throughout the vessel is more pronounced for relatively low heat generation rate in an oxide pool. Parametric calculations are performed considering thermal conditions such as peak heat flux from a light metal layer, heat generation in an oxide pool and external boiling conditions. The major finding is that the most crucial factor for success of in-vessel retention is not the mass of the molten light metal above the oxide pool but the heat generation rate inside the oxide pool and the 3-dimensional vessel heat transfer provides a much larger minimum vessel wall thickness. (authors)

An analytical solution to the heat transfer problem in thick-walled hunt flow

International Nuclear Information System (INIS)

Bluck, Michael J; Wolfendale, Michael J

2017-01-01

Highlights: • Convective heat transfer in Hunt type flow of a liquid metal in a rectangular duct. • Analytical solution to the H1 constant peripheral temperature in a rectangular duct. • New H1 result demonstrating the enhancement of heat transfer due to flow distortion by the applied magnetic field. • Analytical solution to the H2 constant peripheral heat flux in a rectangular duct. • New H2 result demonstrating the reduction of heat transfer due to flow distortion by the applied magnetic field. • Results are important for validation of CFD in magnetohydrodynamics and for implementation of systems code approaches. - Abstract: The flow of a liquid metal in a rectangular duct, subject to a strong transverse magnetic field is of interest in a number of applications. An important application of such flows is in the context of coolants in fusion reactors, where heat is transferred to a lead-lithium eutectic. It is vital, therefore, that the heat transfer mechanisms are understood. Forced convection heat transfer is strongly dependent on the flow profile. In the hydrodynamic case, Nusselt numbers and the like, have long been well characterised in duct geometries. In the case of liquid metals in strong magnetic fields (magnetohydrodynamics), the flow profiles are very different and one can expect a concomitant effect on convective heat transfer. For fully developed laminar flows, the magnetohydrodynamic problem can be characterised in terms of two coupled partial differential equations. The problem of heat transfer for perfectly electrically insulating boundaries (Shercliff case) has been studied previously (Bluck et al., 2015). In this paper, we demonstrate corresponding analytical solutions for the case of conducting hartmann walls of arbitrary thickness. The flow is very different from the Shercliff case, exhibiting jets near the side walls and core flow suppression which have profound effects on heat transfer.

Standard Test Method for Measuring Heat Transfer Rate Using a Thin-Skin Calorimeter

CERN Document Server

American Society for Testing and Materials. Philadelphia

2005-01-01

1.1 This test method covers the design and use of a thin metallic calorimeter for measuring heat transfer rate (also called heat flux). Thermocouples are attached to the unexposed surface of the calorimeter. A one-dimensional heat flow analysis is used for calculating the heat transfer rate from the temperature measurements. Applications include aerodynamic heating, laser and radiation power measurements, and fire safety testing. 1.2 Advantages 1.2.1 Simplicity of ConstructionThe calorimeter may be constructed from a number of materials. The size and shape can often be made to match the actual application. Thermocouples may be attached to the metal by spot, electron beam, or laser welding. 1.2.2 Heat transfer rate distributions may be obtained if metals with low thermal conductivity, such as some stainless steels, are used. 1.2.3 The calorimeters can be fabricated with smooth surfaces, without insulators or plugs and the attendant temperature discontinuities, to provide more realistic flow conditions for ...

Heat transfer system

Science.gov (United States)

Not Available

1980-03-07

A heat transfer system for a nuclear reactor is described. Heat transfer is accomplished within a sealed vapor chamber which is substantially evacuated prior to use. A heat transfer medium, which is liquid at the design operating temperatures, transfers heat from tubes interposed in the reactor primary loop to spaced tubes connected to a steam line for power generation purposes. Heat transfer is accomplished by a two-phase liquid-vapor-liquid process as used in heat pipes. Condensible gases are removed from the vapor chamber through a vertical extension in open communication with the chamber interior.

CFD analysis on heat transfer in low Prandtl number fluid flows

Energy Technology Data Exchange (ETDEWEB)

Borgohain, A.; Maheshwari, N.K.; Vijayan, P.K.; Sinha, R.K., E-mail: bananta@barc.gov.in [Bhabha Atomic Research Centre, Reactor Engineering Div., Trombay, Mumbai (India)

2011-07-01

Use of Computational Fluid Dynamics (CFD) code is helpful for designing liquid metal cooled nuclear reactor systems. Before using any CFD code proper evaluation of the code is essential for simulation of heat transfer in liquid metal flow. In this paper, a review of the literature on the correlations for liquid metal heat transfer is carried out and a comparison with experimental results is performed. CFD analysis is carried out using PHOENICS-3.6 code on heat transfer in molten Lead Bismuth Eutectic (LBE) flowing through tube. Turbulent flow analyses are carried out for the evaluation of the CFD code. The CFD results are compared with the available correlations. Assessment of various turbulence models and correlations for turbulent Prandtl number in the tube geometry are carried out. From the analysis it is found that, the CFD prediction can be improved with modified turbulent Prandtl number in the turbulence models. (author)

Influence on Heat Transfer Coefficient of Heat Exchanger by Velocity and Heat Transfer Temperature Difference

Directory of Open Access Journals (Sweden)

WANG Fang

2017-04-01

Full Text Available Aimed to insufficient heat transfer of heat exchanger, research the influence on the heat transfer coefficient impacted by velocity and heat transfer temperature difference of tube heat exchanger. According to the different heat transfer temperature difference and gas velocity，the experimental data were divided into group. Using the control variable method，the above two factors were analyzed separately. K一△T and k一:fitting curve were clone to obtain empirical function. The entire heat exchanger is as the study object，using numerical simulation methods，porous media，k一￡model，second order upwind mode，and pressure一velocity coupling with SIMPLE algorithm，the entire heat exchanger temperature field and the heat transfer coefficient distribution were given. Finally the trend of the heat transfer coefficient effected by the above two factors was gotten.

MHD and heat transfer benchmark problems for liquid metal flow in rectangular ducts

International Nuclear Information System (INIS)

Sidorenkov, S.I.; Hua, T.Q.; Araseki, H.

1994-01-01

Liquid metal cooling systems of a self-cooled blanket in a tokamak reactor will likely include channels of rectangular cross section where liquid metal is circulated in the presence of strong magnetic fields. MHD pressure drop, velocity distribution and heat transfer characteristics are important issues in the engineering design considerations. Computer codes for the reliable solution of three-dimensional MHD flow problems are needed for fusion relevant conditions. Argonne National Laboratory and The Efremov Institute have jointly defined several benchmark problems for code validation. The problems, described in this paper, are based on two series of rectangular duct experiments conducted at ANL; one of the series is a joint ANL/Efremov experiment. The geometries consist of variation of aspect ratio and wall thickness (thus wall conductance ratio). The transverse magnetic fields are uniform and nonuniform in the axial direction

Heat-transfer in a partially-blocked sodium-cooled rod bundle

International Nuclear Information System (INIS)

Han, J.T.

1979-01-01

Heat transfer coefficients were experimentally determined for 31-rod sodium-cooled bundle with a 6-subchannel central blockage. The Nusselt number is presented as a function of the Peclet number for both the free flow region undisturbed by the blockage and the wake region immediately downstream of the blockage. Results are compared with the existing correlations for liquid metals. The heat transfer coefficient was generally higher in the unblocked free flow region than in the wake region. A leak at the blockage improved the heat transfer coefficient in the wake region

Basic heat transfer

CERN Document Server

Bacon, D H

2013-01-01

Basic Heat Transfer aims to help readers use a computer to solve heat transfer problems and to promote greater understanding by changing data values and observing the effects, which are necessary in design and optimization calculations.The book is concerned with applications including insulation and heating in buildings and pipes, temperature distributions in solids for steady state and transient conditions, the determination of surface heat transfer coefficients for convection in various situations, radiation heat transfer in grey body problems, the use of finned surfaces, and simple heat exc

Heat exchanger selection and design analyses for metal hydride heat pump systems

DEFF Research Database (Denmark)

Mazzucco, Andrea; Voskuilen, Tyler G.; Waters, Essene L.

2016-01-01

This study presents a design analysis for the development of highly efficient heat exchangers within stationary metal hydride heat pumps. The design constraints and selected performance criteria are applied to three representative heat exchangers. The proposed thermal model can be applied to select...... the most efficient heat exchanger design and provides outcomes generally valid in a pre-design stage. Heat transfer effectiveness is the principal performance parameter guiding the selection analysis, the results of which appear to be mildly (up to 13%) affected by the specific Nusselt correlation used....... The thermo-physical properties of the heat transfer medium and geometrical parameters are varied in the sensitivity analysis, suggesting that the length of independent tubes is the physical parameter that influences the performance of the heat exchangers the most. The practical operative regions for each...

Heat transfer of liquid-metal magnetohydrodynamic flow with internal heat generation

International Nuclear Information System (INIS)

Kumamaru, Hiroshige; Kurita, Kazuhisa; Kodama, Satoshi

2000-01-01

Numerical calculations on heat transfer of a magnetohydrodynamic (MHD) flow with internal heat generation in a rectangular channel have been performed for the cases of very-large Hartmann numbers, finite wall conductivities and small aspect ratio (i.e. small length ratios of the channel side perpendicular to the applied magnetic field and the side parallel to the field), simulating typical conditions for a fusion-reactor blanket. The Nusselt numbers of the MHD flow in rectangular channels with aspect ratios of 1/10 to 1/40 for Hartmann numbers of ∼5 x 10 5 become ∼10 times higher than those for the corresponding flow under no magnetic field. The Nusselt number becomes higher as the internal heat generation rate increases as far as the heat generation rates in a fusion reactor blanket are considered. (author)

The influence of the key limiting factors on the limitations of heat transfer in heat pipes with various working fluids

Directory of Open Access Journals (Sweden)

Melnyk R. S.

2017-04-01

Full Text Available Aluminium and copper heat pipes with grooved and metal fibrous capillary structure are high effective heat transfer devices. They are used in different cooling systems of electronic equipment like a LED modules, microprocessors, receive-transmit modules and so on. However thus heat pipes have heat transfer limitations. There are few types of this limitations: hydraulic limitation, boiling limitation, liquid entrainment by vapor flow and sonic limitation. There is necessity to know which one of these limitations is determinant for heat pipe due to design process. At a present article calculations of maximum heat transfer ability represented. All these calculations were made for LED cooling by using heat pipes with grooved and metal fibrous capillary structures. Pentane, acetone, isobutane and water were used as a coolants. It was shown that the main operation limit for axial grooved heat pipe, which determinate maximum heat transfer ability due to inclination angle for location of cooling zone higher than evaporation zone case, is entrainment limit for pentane and acetone coolants. Nevertheless, for isobutane coolant the main limitation is a boiling limit. However, for heat pipes with metal fibrous capillary structure the main limitation is a capillary limit. This limitation was a determinant for all calculated coolants: water, pentane and acetone. For high porosity range of capillary structure, capillary limit transfer to sonic limit for heat pipes with water, that means that the vapor velocity increases to sonic velocity and can't grow any more. Due to this, coolant cant in a needed quantity infill condensation zone and the last one drained. For heat pipes with acetone and pentane, capillary limit transfer to boiling limit. All calculations were made for vapor temperature equal to 50°C, and for porosity range from 30% to 90%.

Analysis of natural convection heat transfer with crust formation in the molten metal pool using CONV-2 and 3D computer codes

International Nuclear Information System (INIS)

Park, R. J.; Kang, K. H.; Kim, S. B.; Kim, H. D.; Choi, S. M.

1998-01-01

Analytical studies have been performed on natural convection heat transfer with crust formation in a molten metal pool to validate and evaluate experimental data using the CONV-2 and 3D computer codes. Two types of steady state tests, a low and high geometric aspect ratio case in the molten metal pool, were performed to investigate crust thickness as a function of boundary conditions. The CONV-2 and 3D computer codes were developed under the OECD/NEA RASPLAV project to simulate two- and three-dimensional natural convection heat transfer with crust formation, respectively. The Rayleigh-Benard flow patterns in the molten metal pool contribute to the temperature distribution, which affects non-uniform crust formation. The CONV-2D results on crust thickness are a little higher than the experimental data because of heat loss during the test. In comparison of the CONV-3D results with the CONV-2D results on crust thickness, the three-dimensional results are higher than the two-dimensional results, because of three dimensional natural convection flow and wall effect

Radiative heat transfer in the extreme near field.

Science.gov (United States)

Kim, Kyeongtae; Song, Bai; Fernández-Hurtado, Víctor; Lee, Woochul; Jeong, Wonho; Cui, Longji; Thompson, Dakotah; Feist, Johannes; Reid, M T Homer; García-Vidal, Francisco J; Cuevas, Juan Carlos; Meyhofer, Edgar; Reddy, Pramod

2015-12-17

Radiative transfer of energy at the nanometre length scale is of great importance to a variety of technologies including heat-assisted magnetic recording, near-field thermophotovoltaics and lithography. Although experimental advances have enabled elucidation of near-field radiative heat transfer in gaps as small as 20-30 nanometres (refs 4-6), quantitative analysis in the extreme near field (less than 10 nanometres) has been greatly limited by experimental challenges. Moreover, the results of pioneering measurements differed from theoretical predictions by orders of magnitude. Here we use custom-fabricated scanning probes with embedded thermocouples, in conjunction with new microdevices capable of periodic temperature modulation, to measure radiative heat transfer down to gaps as small as two nanometres. For our experiments we deposited suitably chosen metal or dielectric layers on the scanning probes and microdevices, enabling direct study of extreme near-field radiation between silica-silica, silicon nitride-silicon nitride and gold-gold surfaces to reveal marked, gap-size-dependent enhancements of radiative heat transfer. Furthermore, our state-of-the-art calculations of radiative heat transfer, performed within the theoretical framework of fluctuational electrodynamics, are in excellent agreement with our experimental results, providing unambiguous evidence that confirms the validity of this theory for modelling radiative heat transfer in gaps as small as a few nanometres. This work lays the foundations required for the rational design of novel technologies that leverage nanoscale radiative heat transfer.

''Heat Transfer at the Mold-Metal Interface in Permanent Mold Casting of Aluminum Alloys'' Final Project Report; FINAL

International Nuclear Information System (INIS)

Pehlke, R. D.; Cookson, John M.; Shouwei Hao; Prasad Krishna; Bilkey, Kevin T.

2001-01-01

This project on heat transfer coefficients in metal permanent mold casting has been conducted in three areas. They are the theoretical study at the University of Michigan, the experimental investigation of squeeze casting at CMI-Tech Center (Now Hayes-Lemmerz Technical Center) and the experimental investigation of low pressure permanent mold casting at Amcast Automotive

Production of molten UO2 pools by internal heating: apparatus and preliminary experimental heat transfer results

International Nuclear Information System (INIS)

Chasanov, M.G.; Gunther, W.H.; Baker, L. Jr.

1977-01-01

The capability for removal of heat from a pool of molten fuel under postaccident conditions is an important consideration in liquid-metal fast breeder reactor safety analysis. No experimental data for pool heat transfer from molten UO 2 under conditions simulating internal heat generation by fission product decay have been reported previously in the literature. An apparatus to provide such data was developed and used to investigate heat transfer from pools containing up to 7.5 kg of UO 2 ; the internal heat generation rates and pool depths attained cover most of the ranges of interest for postaccident heat removal analysis. It was also observed in these studies that the presence of simulated fission products corresponding to approximately 150,000 kW-day/kg burnup had no significant effect on the observed heat transfer

Experimental study of heat transfer in a transverse flow around the heat exchanger tubes bank by lead

International Nuclear Information System (INIS)

Berezin, A.N.; Grabezhnaya, V.A.; Mikheev, A.S.; Parfenov, A.S.

2014-01-01

The results of the work to determine the heat transfer coefficient in crossflow by lead of pipes are presented. The study was conducted at supercritical pressure in the water circuit. There was a significant inequality in the distribution of the heat flow in different rows of the bundle of heat exchange tubes of corridor location at crossflow their lead. The experimentally determined heat transfer coefficients from the lead differ substantially from those generally accepted recommendations for the calculation of heat transfer at cross flow of rod bundle by liquid metal. The experimental results are close to those obtained earlier on the model with cross flow of heat exchanger tubes bundle by lead alloy with bismuth [ru

Heat transfer enhancement by finned heat sinks with micro-structured roughness

International Nuclear Information System (INIS)

Ventola, L; Chiavazzo, E; Asinari, P; Calignano, F; Manfredi, D

2014-01-01

We investigated the benefits of micro-structured roughness on heat transfer performance of heat sinks, cooled by forced air. Heat sinks in aluminum alloy by direct metal laser sintering (DMLS) manufacturing technique were fabricated; values of the average surface roughness R a from 1 to 25 microns (standard milling leads to roughness around 1 micron) under turbulent regimes (Reynolds number based on heating edge from 3000 to 17000) have been explored. An enhancement of 50% in thermal performances with regards to standard manufacturing was observed. This may open the way for huge boost in the technology of electronic cooling by DMLS.

Heat Transfer Enhancement by Finned Heat Sinks with Micro-structured Roughness

Science.gov (United States)

Ventola, L.; Chiavazzo, E.; Calignano, F.; Manfredi, D.; Asinari, P.

2014-04-01

We investigated the benefits of micro-structured roughness on heat transfer performance of heat sinks, cooled by forced air. Heat sinks in aluminum alloy by direct metal laser sintering (DMLS) manufacturing technique were fabricated; values of the average surface roughness Ra from 1 to 25 microns (standard milling leads to roughness around 1 micron) under turbulent regimes (Reynolds number based on heating edge from 3000 to 17000) have been explored. An enhancement of 50% in thermal performances with regards to standard manufacturing was observed. This may open the way for huge boost in the technology of electronic cooling by DMLS.

Experimental study of nucleate pool boiling heat transfer of water on silicon oxide nanoparticle coated copper heating surface

International Nuclear Information System (INIS)

Das, Sudev; Kumar, D.S.; Bhaumik, Swapan

2016-01-01

Highlights: • EBPVD approach was employed for fabrication of well-ordered nanoparticle coated micro/nanostructure on metal surface. • Nucleate boiling heat transfer performance on nanoparticle coated micro/nanostructure surface was experimentally studied. • Stability of nanoparticle coated surface under boiling environment was systematically studied. • 58% enhancement of boiling heat transfer coefficient was found. • Present experimental results are validated with well known boiling correlations. - Abstract: Electron beam physical vapor deposition (EBPVD) coating approach was employed for fabrication of well-ordered of nanoparticle coated micronanostructures on metal surfaces. This paper reports the experimental study of augmentation of pool boiling heat transfer performance and stabilities of silicon oxide nanoparticle coated surfaces with water at atmospheric pressure. The surfaces were characterized with respect to dynamic contact angle, surface roughness, topography, and morphology. The results were found that there is a reduction of about 36% in the incipience superheat and 58% enhancement in heat transfer coefficient for silicon oxide coated surface over the untreated surface. This enhancement might be the reason of enhanced wettability, enhanced surface roughness and increased number of a small artificial cavity on a heating surface. The performance and stability of nanoparticle coated micro/nanostructure surfaces were examined and found that after three runs of experiment the heat transfer coefficient with heat flux almost remain constant.

Analysis of Heat Transfer

International Nuclear Information System (INIS)

2003-08-01

This book deals with analysis of heat transfer which includes nonlinear analysis examples, radiation heat transfer, analysis of heat transfer in ANSYS, verification of analysis result, analysis of heat transfer of transition with automatic time stepping and open control, analysis of heat transfer using arrangement of ANSYS, resistance of thermal contact, coupled field analysis such as of thermal-structural interaction, cases of coupled field analysis, and phase change.

Experimental heat transfer to supercritical carbon dioxide flowing upward vertical tube with highly conducting surroundings

International Nuclear Information System (INIS)

Son, Hyung M.; Suh, Kune Y.

2012-01-01

Highlights: ► Performed experiment for the upward SCO 2 flow surrounded by highly conducting metal. ► Selected dimensionless groups representing the property variations and buoyancy. ► Developed the heat transfer correlation for the mixed thermal boundary condition. ► Wrote a finite element heat transfer code to find the appropriate correlation. ► Coupled the 1D convection and 2D heat conduction via heat transfer coefficient. - Abstract: This paper presents heat transfer characteristics of supercritical carbon dioxide flow inside vertical circular pipe surrounded by highly conducting material, and develops an adequate tool to test the performance of available heat transfer correlations with. The possible situations are illustrated for the nuclear power plant to which the above-mentioned geometric configuration might be applicable. An experimental loop with vertical circular geometry is designed and constructed to test the upward flow in supercritical state when the axial heat transfer is enhanced by the surrounding metals, resulting in a wall boundary condition between the constant heat flux and temperature. The set of correlations and important findings are critically reviewed from extensive literature survey. Incorporating nondimensional groups resorting to past insights from the available literature, a convective heat transfer correlation is proposed. The optimization procedure is described which utilizes a random walk method along with the in-house finite element heat transfer code to determine the coefficients of the proposed heat transfer correlation. The proposed methodology can be applied to evaluation of heat transfer when the heat transfer coefficient data cannot directly be determined from the experiment.

Single-phase liquid jet impingement heat transfer

International Nuclear Information System (INIS)

Webb, B.W.; Ma, C.F.

1995-01-01

Impinging liquid jets have been demonstrated to be an effective means of providing high heat/mass transfer rates in industrial transport processes. When a liquid jet strikes a surface, thin hydrodynamic and thermal boundary layers from in the region directly beneath due to the jet deceleration and the resulting increase in pressure. The flow is then forced to accelerate in a direction parallel to the target surface in what is termed the wall jet or parallel flow zone. The thickness of the hydrodynamic and thermal boundary layers in the stagnation region may be of the order of tens of micrometers. Consequently, very high heat/mass transfer coefficients exist in the stagnation zone directly under the jet. Transport coefficients characteristic of parallel flow prevail in the wall jet region. The high heat transfer coefficients make liquid jet impingement an attractive cooling option where high heat fluxes are the norm. Some industrial applications include the thermal treatment of metals, cooling of internal combustion engines, and more recently, thermal control of high-heat-dissipation electronic devices. Both circular and planar liquid jets have attracted research attention. 180 refs., 35 figs., 11 tabs

Effect of crust increase on natural convection heat transfer in the molten metal pool

International Nuclear Information System (INIS)

Park, Rae Joon; Kim, Sang Baik; Kim, Hee Dong; Choi, Sang Min

1999-01-01

An experimental study has been performed on natural convection heat transfer with a rapid crust formation in the molten metal pool of a low Prandtl number fluid. Two types of steady state tests, a low and high geometric aspect ratio cases in the molten metal pool, were performed. The crust thickness by solidification was measured as a function of boundary surface temperatures. The experimental results on the relationship between the Nusselt number and Rayleigh number in the molten metal pool with a crust formation were compared with existing correlations. The experimental study has shown that the bottom surface temperature of the molten metal layer, in all experiments, is the major influential parameter in the crust formation, due to the natural convection flow. The Nusselt number of the case without a crust formation in the molten metal pool is greater than that of the case with the crust formation at the same Rayleigh number. The present experimental results on the relationship between the Nusselt number and Rayleigh number in the molten metal pool match well with Globe and Dropkin's correlation. From the experimental results, a new correlation between the Nusselt number and Rayleigh number in the molten metal pool with the crust formation was developed as Nu=0.0923 (Ra) 0.0923 (2 X 10 4 7 ). (author)

Radius ratio effects on natural heat transfer in concentric annulus

DEFF Research Database (Denmark)

Alipour, M.; Hosseini, R.; Kolaei, Alireza Rezania

2013-01-01

This paper studies natural convection heat transfer in vertical and electrically heated annulus. The metallic cylinders mounted concentrically in a parallel tube. Measurements are carried out for four input electric powers and three radius ratios with an apparatus immersed in stagnant air...

Heat Transfer Analysis of Localized Heat-Treatment for Grade 91 Steel

Science.gov (United States)

Walker, Jacob D.

Many of the projects utilizing Grade 91 steel are large in scale, therefore it is necessary to assemble on site. The assembly of the major pieces requires welding in the assembly; this drastically changes the superior mechanical properties of Grade 91 steel that it was specifically developed for. Therefore, because of the adverse effects of welding on the mechanical properties of Grade 91, it is necessary to do a localized post weld heat treatment. As with most metallic materials grade 91 steel requires a very specific heat treatment process. This process includes a specific temperature and duration at that temperature to achieve the heat treatment desired. Extensive research has been done to determine the proper temperatures and duration to provide the proper microstructure for the superior mechanical properties that are inherent to Grade 91 steel. The welded sections are typically large structures that require local heat treatments and cannot be placed in an oven. The locations of these structures vary from indoors in a controlled environment to outdoors with unpredictable environments. These environments can be controlled somewhat, however in large part the surrounding conditions are unchangeable. Therefore, there is a need to develop methods to accurately apply the surrounding conditions and geometries to a theoretical model in order to provide the proper requirements for the local heat treatment procedure. Within this requirement is the requirement to define unknowns used in the heat transfer equations so that accurate models can be produced and accurate results predicted. This study investigates experimentally and numerically the heat transfer and temperature fields of Grade 91 piping in a local heat treatment. The objective of this thesis research is to determine all of the needed heat transfer coefficients. The appropriate heat transfer coefficients are determined through the inverse heat conduction method utilizing a ceramic heat blanket. This will be done

Introduction to heat transfer

CERN Document Server

SUNDÉN, B

2012-01-01

Presenting the basic mechanisms for transfer of heat, Introduction to Heat Transfer gives a deeper and more comprehensive view than existing titles on the subject. Derivation and presentation of analytical and empirical methods are provided for calculation of heat transfer rates and temperature fields as well as pressure drop. The book covers thermal conduction, forced and natural laminar and turbulent convective heat transfer, thermal radiation including participating media, condensation, evaporation and heat exchangers.

The effect of a magnetic field on heat transfer in a slotted channel

International Nuclear Information System (INIS)

Evtushenko, I.A.; Hua, T.Q.; Kirillov, I.R.; Reed, Claude B.; Sidorenkov, S.S.

1995-01-01

The results of numerical and experimental studies of liquid metal heat transfer in slotted channels in a transverse magnetic field are presented. Test results showed an improvement in heat transfer in a straight channel at low and moderate interaction parameter N. The Nusselt number at small N (around 120) was up to twofold higher than in turbulent flow without a magnetic field, the Peclet number being equal. This effect of heat transfer enhancement is caused by the generation and development of large-scale velocity fluctuations close to the heated wall area. Qualitative and quantitative correlations between heat transfer and velocity fluctuation characteristics are presented. (orig.)

Heat transfer fluids containing nanoparticles

Science.gov (United States)

Singh, Dileep; Routbort, Jules; Routbort, A.J.; Yu, Wenhua; Timofeeva, Elena; Smith, David S.; France, David M.

2016-05-17

A nanofluid of a base heat transfer fluid and a plurality of ceramic nanoparticles suspended throughout the base heat transfer fluid applicable to commercial and industrial heat transfer applications. The nanofluid is stable, non-reactive and exhibits enhanced heat transfer properties relative to the base heat transfer fluid, with only minimal increases in pumping power required relative to the base heat transfer fluid. In a particular embodiment, the plurality of ceramic nanoparticles comprise silicon carbide and the base heat transfer fluid comprises water and water and ethylene glycol mixtures.

Molten pool-lower head integrity. Heat transfer models including advanced numerical simulations (DNS)

Energy Technology Data Exchange (ETDEWEB)

Seiler, J.M.; Bonnet, J.M.; Bernaz, L. [CEA Grenoble (France)

2001-07-01

Extensive studies have been performed to investigate the heat transfer within a molten corium pool (homogeneous, stratified and with miscibility gap): Synthesis of heat transfer correlations in molten pool (homogeneous and stratified), Focusing effect in stratified metal layer, DNS analysis of Rayleigh Benard instabilities at the top boundary; interpretation of the different convection regimes and exponents affecting the Rayleigh number in the heat transfer correlations, Molten pool model for corium presenting a miscibility gap. Condition for de-stratification. (authors)

Molten pool-lower head integrity. Heat transfer models including advanced numerical simulations (DNS)

International Nuclear Information System (INIS)

Seiler, J.M.; Bonnet, J.M.; Bernaz, L.

2001-01-01

Extensive studies have been performed to investigate the heat transfer within a molten corium pool (homogeneous, stratified and with miscibility gap): Synthesis of heat transfer correlations in molten pool (homogeneous and stratified), Focusing effect in stratified metal layer, DNS analysis of Rayleigh Benard instabilities at the top boundary; interpretation of the different convection regimes and exponents affecting the Rayleigh number in the heat transfer correlations, Molten pool model for corium presenting a miscibility gap. Condition for de-stratification. (authors)

Heat transfer direction dependence of heat transfer coefficients in annuli

Science.gov (United States)

Prinsloo, Francois P. A.; Dirker, Jaco; Meyer, Josua P.

2018-04-01

In this experimental study the heat transfer phenomena in concentric annuli in tube-in-tube heat exchangers at different annular Reynolds numbers, annular diameter ratios, and inlet fluid temperatures using water were considered. Turbulent flow with Reynolds numbers ranging from 15,000 to 45,000, based on the average bulk fluid temperature was tested at annular diameter ratios of 0.327, 0.386, 0.409 and 0.483 with hydraulic diameters of 17.00, 22.98, 20.20 and 26.18 mm respectively. Both heated and cooled annuli were investigated by conducting tests at a range of inlet temperatures between 10 °C to 30 °C for heating cases, and 30 °C to 50 °C for cooling cases. Of special interest was the direct measurement of local wall temperatures on the heat transfer surface, which is often difficult to obtain and evasive in data-sets. Continuous verification and re-evaluation of temperatures measurements were performed via in-situ calibration. It is shown that inlet fluid temperature and the heat transfer direction play significant roles on the magnitude of the heat transfer coefficient. A new adjusted Colburn j-factor definition is presented to describe the heating and cooling cases and is used to correlate the 894 test cases considered in this study.

Gravitationally Driven Wicking for Enhanced Condensation Heat Transfer.

Science.gov (United States)

Preston, Daniel J; Wilke, Kyle L; Lu, Zhengmao; Cruz, Samuel S; Zhao, Yajing; Becerra, Laura L; Wang, Evelyn N

2018-04-17

Vapor condensation is routinely used as an effective means of transferring heat or separating fluids. Filmwise condensation is prevalent in typical industrial-scale systems, where the condensed fluid forms a thin liquid film due to the high surface energy associated with many industrial materials. Conversely, dropwise condensation, where the condensate forms discrete liquid droplets which grow, coalesce, and shed, results in an improvement in heat transfer performance of an order of magnitude compared to filmwise condensation. However, current state-of-the-art dropwise technology relies on functional hydrophobic coatings, for example, long chain fatty acids or polymers, which are often not robust and therefore undesirable in industrial conditions. In addition, low surface tension fluid condensates, such as hydrocarbons, pose a unique challenge because common hydrophobic condenser coatings used to shed water (with a surface tension of 73 mN/m) often do not repel fluids with lower surface tensions (condensation heat transfer using gravitationally driven flow through a porous metal wick, which takes advantage of the condensate's affinity to wet the surface and also eliminates the need for condensate-phobic coatings. The condensate-filled wick has a lower thermal resistance than the fluid film observed during filmwise condensation, resulting in an improved heat transfer coefficient of up to an order of magnitude and comparable to that observed during dropwise condensation. The improved heat transfer realized by this design presents the opportunity for significant energy savings in natural gas processing, thermal management, heating and cooling, and power generation.

Bubble Departure from Metal-Graphite Composite Surfaces and Its Effects on Pool Boiling Heat Transfer

Science.gov (United States)

Chao, David F.; Sankovic, John M.; Motil, Brian J.; Yang, W-J.; Zhang, Nengli

2010-01-01

The formation and growth processes of a bubble in the vicinity of graphite micro-fiber tips on metal-graphite composite boiling surfaces and their effects on boiling behavior are investigated. It is discovered that a large number of micro bubbles are formed first at the micro scratches and cavities on the metal matrix in pool boiling. By virtue of the non-wetting property of graphite, once the growing micro bubbles touch the graphite tips, the micro bubbles are sucked by the tips and merged into larger micro bubbles sitting on the end of the tips. The micro bubbles grow rapidly and coalesce to form macro bubbles, each spanning several tips. The necking process of a detaching macro bubble is analyzed. It is revealed that a liquid jet is produced by sudden break-off of the bubble throat. The composite surfaces not only have higher temperatures in micro- and macrolayers but also make higher frequency of the bubble departure, which increase the average heat fluxes in both the bubble growth stage and in the bubble departure period. Based on these analyses, the enhancement mechanism of pool boiling heat transfer on composite surfaces is clearly revealed.

Near-field heat transfer between graphene/hBN multilayers

Science.gov (United States)

Zhao, Bo; Guizal, Brahim; Zhang, Zhuomin M.; Fan, Shanhui; Antezza, Mauro

2017-06-01

We study the radiative heat transfer between multilayer structures made by a periodic repetition of a graphene sheet and a hexagonal boron nitride (hBN) slab. Surface plasmons in a monolayer graphene can couple with hyperbolic phonon polaritons in a single hBN film to form hybrid polaritons that can assist photon tunneling. For periodic multilayer graphene/hBN structures, the stacked metallic/dielectric array can give rise to a further effective hyperbolic behavior, in addition to the intrinsic natural hyperbolic behavior of hBN. The effective hyperbolicity can enable more hyperbolic polaritons that enhance the photon tunneling and hence the near-field heat transfer. However, the hybrid polaritons on the surface, i.e., surface plasmon-phonon polaritons, dominate the near-field heat transfer between multilayer structures when the topmost layer is graphene. The effective hyperbolic regions can be well predicted by the effective medium theory (EMT), thought EMT fails to capture the hybrid surface polaritons and results in a heat transfer rate much lower compared to the exact calculation. The chemical potential of the graphene sheets can be tuned through electrical gating and results in an additional modulation of the heat transfer. We found that the near-field heat transfer between multilayer structures does not increase monotonously with the number of layers in the stack, which provides a way to control the heat transfer rate by the number of graphene layers in the multilayer structure. The results may benefit the applications of near-field energy harvesting and radiative cooling based on hybrid polaritons in two-dimensional materials.

Coupled heat transfer in high temperature transporting system with semitransparent/opaque material

International Nuclear Information System (INIS)

Du Shenghua; Xia Xinjin

2010-01-01

The heat transfer model of the aerodynamic heating coupled with radiative cooling was developed. The thermal protect system includes the higher heat flux region with high temperature semitransparent material, the heat transporting channel and the lower heat flux region with metal. The control volume method was combined with the Monte Carlo method to calculate the coupled heat transfer of the transporting system, and the thermal equilibrium equation for the transporting channel was solved simultaneously. The effect of the aeroheating flux radio, the area ratio of radiative surfaces, the convective heat transfer coefficient of the heat transporting channel on the radiative surface temperature and the fluid temperature in the heat transporting channel were analyzed. The effect of radiation and conduction in the semitransparent material was discussed. The result shows that to increase the convective heat transfer coefficient in heat flux channel can enhance the heat transporting ability of the system, but the main parameter to effect on the temperature of the heat transporting system is the area ratio of radiative surfaces. (authors)

Radiative heat transfer

CERN Document Server

Modest, Michael F

2013-01-01

The third edition of Radiative Heat Transfer describes the basic physics of radiation heat transfer. The book provides models, methodologies, and calculations essential in solving research problems in a variety of industries, including solar and nuclear energy, nanotechnology, biomedical, and environmental. Every chapter of Radiative Heat Transfer offers uncluttered nomenclature, numerous worked examples, and a large number of problems-many based on real world situations-making it ideal for classroom use as well as for self-study. The book's 24 chapters cover the four major areas in the field: surface properties; surface transport; properties of participating media; and transfer through participating media. Within each chapter, all analytical methods are developed in substantial detail, and a number of examples show how the developed relations may be applied to practical problems. It is an extensive solution manual for adopting instructors. Features: most complete text in the field of radiative heat transfer;...

Review of heat transfer problems associated with magnetically-confined fusion reactor concepts

International Nuclear Information System (INIS)

Hoffman, M.A.; Werner, R.W.; Carlson, G.A.; Cornish, D.N.

1976-01-01

Conceptual design studies of possible fusion reactor configurations have revealed a host of interesting and sometimes extremely difficult heat transfer problems. The general requirements imposed on the coolant system for heat removal of the thermonuclear power from the reactor are discussed. In particular, the constraints imposed by the fusion plasma, neutronics, structure and magnetic field environment are described with emphasis on those aspects which are unusual or unique to fusion reactors. Then the particular heat transfer characteristics of various possible coolants including lithium, flibe, boiling alkali metals, and helium are discussed in the context of these general fusion reactor requirements. Some specific areas where further experimental and/or theoretical work is necessary are listed for each coolant along with references to the pertinent research already accomplished. Specialized heat transfer problems of the plasma injection and removal systems are also described. Finally, the challenging heat transfer problems associated with the superconducting magnets are reviewed, and once again some of the key unsolved heat transfer problems are enumerated

Match properties of heat transfer and coupled heat and mass transfer processes in air-conditioning system

International Nuclear Information System (INIS)

Zhang Tao; Liu Xiaohua; Zhang Lun; Jiang Yi

2012-01-01

Highlights: ► Investigates match properties of heat or mass transfer processes in HVAC system. ► Losses are caused by limited transfer ability, flow and parameter mismatching. ► Condition of flow matching is the same heat capacity of the fluids. ► Parameter matching is only reached along the saturation line in air–water system. ► Analytical solutions of heat and mass transfer resistance are derived. - Abstract: Sensible heat exchangers and coupled heat and mass transfer devices between humid air and water/desiccant are commonly used devices in air-conditioning systems. This paper focuses on the match properties of sensible heat transfer processes and coupled heat and mass transfer processes in an effort to understand the reasons for performance limitations in order to optimize system performance. Limited heat transfer capability and flow mismatching resulted in heat resistance of the sensible heat transfer process. Losses occurred during the heat and mass transfer processes due to limited transfer capability, flow mismatching, and parameter mismatching. Flow matching was achieved when the heat capacities of the fluids were identical, and parameter matching could only be reached along the saturation line in air–water systems or the iso-concentration line in air–desiccant systems. Analytical solutions of heat transfer resistance and mass transfer resistance were then derived. The heat and mass transfer process close to the saturation line is recommended, and heating sprayed water resulted in better humidification performance than heating inlet air in the air humidifier.

Application of metal foam heat exchangers for a high-performance liquefied natural gas regasification system

International Nuclear Information System (INIS)

Kim, Dae Yeon; Sung, Tae Hong; Kim, Kyung Chun

2016-01-01

The intermediate fluid vaporizer has wide applications in the regasification of LNG (liquefied natural gas). The heat exchanger performance is one of the main contributors to the thermodynamic and cost effectiveness of the entire LNG regasification system. Within the paper, the authors discuss a new concept for a compact heat exchanger with a micro-cellular structure medium to minimize volume and mass and to increase thermal efficiency. Numerical calculations have been conducted to design a metal-foam filled plate heat exchanger and a shell-and-tube heat exchanger using published experimental correlations. The geometry of both heat exchangers was optimized using the conditions of thermolators in LNG regasification systems. The heat transfer and pressure drop performance was predicted to compare the heat exchangers. The results show that the metal-foam plate heat exchanger has the best performance at different channel heights and mass flow rates of fluid. In the optimized configurations, the metal-foam plate heat exchanger has a higher heat transfer rate and lower pressure drop than the shell-and-tube heat exchanger as the mass flow rate of natural gas is increased. - Highlights: • A metal foam heat exchanger is proposed for LNG regasification system. • Comparison was made with a shell and tube heat exchanger. • Heat transfer and pressure drop characteristics were estimated. • The geometry of both heat exchangers is optimized for thermolators. • It can be used as a compact and high performance thermolators.

Modeling of the heat transfer performance of plate-type dispersion nuclear fuel elements

Science.gov (United States)

Ding, Shurong; Huo, Yongzhong; Yan, XiaoQing

2009-08-01

Considering the mutual actions between fuel particles and the metal matrix, the three-dimensional finite element models are developed to simulate the heat transfer behaviors of dispersion nuclear fuel plates. The research results indicate that the temperatures of the fuel plate might rise more distinctly with considering the particle swelling and the degraded surface heat transfer coefficients with increasing burnup; the local heating phenomenon within the particles appears when their thermal conductivities are too low. With rise of the surface heat transfer coefficients, the temperatures within the fuel plate decrease; the temperatures of the fuel plate are sensitive to the variations of the heat transfer coefficients whose values are lower, but their effects are weakened and slight when the heat transfer coefficients increase and reach a certain extent. Increasing the heat generation rate leads to elevating the internal temperatures. The temperatures and the maximum temperature differences within the plate increase along with the particle volume fractions. The surface thermal flux goes up along with particle volume fractions and heat generation rates, but the effects of surface heat transfer coefficients are not evident.

Enhancement of heat transfer coefficient multi-metallic nanofluid with ANFIS modeling for thermophysical properties

Directory of Open Access Journals (Sweden)

Balla Hyder H.

2015-01-01

Full Text Available Cu and Zn-water nanofluid is a suspension of the Cu and Zn nanoparticles with the size 50 nm in the water base fluid for different volume fractions to enhance its Thermophysical properties. The determination and measuring the enhancement of Thermophysical properties depends on many limitations. Nanoparticles were suspended in a base fluid to prepare a nanofluid. A coated transient hot wire apparatus was calibrated after the building of the all systems. The vibro-viscometer was used to measure the dynamic viscosity. The measured dynamic viscosity and thermal conductivity with all parameters affected on the measurements such as base fluids thermal conductivity, volume factions, and the temperatures of the base fluid were used as input to the Artificial Neural Fuzzy inference system to modeling both dynamic viscosity and thermal conductivity of the nanofluids. Then, the ANFIS modeling equations were used to calculate the enhancement in heat transfer coefficient using CFD software. The heat transfer coefficient was determined for flowing flow in a circular pipe at constant heat flux. It was found that the thermal conductivity of the nanofluid was highly affected by the volume fraction of nanoparticles. A comparison of the thermal conductivity ratio for different volume fractions was undertaken. The heat transfer coefficient of nanofluid was found to be higher than its base fluid. Comparisons of convective heat transfer coefficients for Cu and Zn nanofluids with the other correlation for the nanofluids heat transfer enhancement are presented. Moreover, the flow demonstrates anomalous enhancement in heat transfer nanofluids.

Evaluation of heat transfer in acupuncture needles: convection and conduction approaches.

Science.gov (United States)

Tzou, Chieh-Han John; Yang, Tzyy-Yih; Chung, Ya-Chien

2015-04-01

Originating in ancient China, acupuncture using needles has been developed for thousands of years and has received attention for its reported medical remedies, such as pain relief and chronic disease treatment. Heat transfer through the needles, which might have effects on the biomechanism of acupuncture, providing a stimulus and regulating homeostasis, has never been studied. This article analyzes the significance of heat transfer through needles via convection and conduction, approached by means of computational analysis. The needle is a cylindrical body, and an axis symmetrical steady-state heat-transfer model that viscosity and static pressure was not applied. This article evaluates heat transfer via acupuncture needles by using five metal materials: silver, copper, brass, iron, and stainless steel. A silver needle of the type extensively applied in acupuncture can dissipate more than seven times as much heat as a stainless steel needle of the same type. Heat transfer through such a needle is significant, compared to natural body-energy consumption over a range of ambient temperatures. The mechanism by which heat flows in or out of the body through the needles may be crucial in the remedial efficacy of acupuncture. Copyright © 2015. Published by Elsevier B.V.

Experimental study on forced convection boiling heat transfer on molten alloy

International Nuclear Information System (INIS)

Nishimura, Satoshi; Ueda, Nobuyuki; Nishi, Yoshihisa; Furuya, Masahiro; Kinoshita, Izumi

1999-01-01

In order to clarify the characteristics of forced convection boiling heat transfer on molten metal, basic experiments have been carried out with subcooled water flowing on molten Wood's alloy pool surface. In these experiments, water flows horizontally in a rectangular duct. A cavity filled with Wood's alloy is present in a portion of the bottom of the duct. Wood's alloy is heated by a copper conductor at the bottom of the cavity. The experiments have been carried out with various velocities and subcoolings of water, and temperature of Wood's alloy. Boiling curves on the molten alloy surface were obtained and compared with that on a solid heat transfer surface. It is observed that the boiling curve on molten alloy is in a lower superheat region than the boiling curve on a solid surface. This indicates that the heat transfer performance of forced convection boiling on molten alloy is enhanced by increase of the heat transfer area, due to oscillation of the surface and fragmentation of molten alloy

Liquid metal heat exchanger for efficient heating of soils and geologic formations

Science.gov (United States)

DeVault, Robert C [Knoxville, TN; Wesolowski, David J [Kingston, TN

2010-02-23

Apparatus for efficient heating of subterranean earth includes a well-casing that has an inner wall and an outer wall. A heater is disposed within the inner wall and is operable within a preselected operating temperature range. A heat transfer metal is disposed within the outer wall and without the inner wall, and is characterized by a melting point temperature lower than the preselected operating temperature range and a boiling point temperature higher than the preselected operating temperature range.

Heat transfer with geometric shape of micro-fin tubes (I) - Condensing heat transfer

Energy Technology Data Exchange (ETDEWEB)

Kwak, K M; Chang, J S; Bai, C H; Chung, M [Yeungnam University, Kyungsan (Korea)

1999-11-01

To examine the enhancement mechanism of condensing heat transfer through microfin tube, the condensation experiments with refrigerant HCFC 22 are performed using 4 and 6 kinds of microfin tubes with outer diameter of 9.52 mm and 7.0 mm, respectively. Used microfin tubes have different shape and number of fins with each other. The main heat transfer enhancement mechanism is known to be the enlargement of heat transfer area and turbulence promotion. Together with these main factors, we can find other enhancement factors by the experimental data, which are the overflow of the refrigerant over the microfin and microfin arrangement. The overflow of the refrigerant over the microfin can be analyzed by the geometric shape of the microfin. microfin tubes having a shape which can give much overflow over the microfin show large condensing heat transfer coefficients. The effect of microfin arrangement is related to the heat transfer resistance of liquid film of refrigerant. The condensing heat transfer coefficients are high for the microfin tube with even distribution of liquid film. 17 refs., 14 figs., 3 tabs.

Measuring of heat transfer coefficient

DEFF Research Database (Denmark)

Henningsen, Poul; Lindegren, Maria

Subtask 3.4 Measuring of heat transfer coefficient Subtask 3.4.1 Design and setting up of tests to measure heat transfer coefficient Objective: Complementary testing methods together with the relevant experimental equipment are to be designed by the two partners involved in order to measure...... the heat transfer coefficient for a wide range of interface conditions in hot and warm forging processes. Subtask 3.4.2 Measurement of heat transfer coefficient The objective of subtask 3.4.2 is to determine heat transfer values for different interface conditions reflecting those typically operating in hot...

Capillary-Condenser-Pumped Heat-Transfer Loop

Science.gov (United States)

Silverstein, Calvin C.

1989-01-01

Heat being transferred supplies operating power. Capillary-condenser-pumped heat-transfer loop similar to heat pipe and to capillary-evaporator-pumped heat-transfer loop in that heat-transfer fluid pumped by evaporation and condensation of fluid at heat source and sink, respectively. Capillary condenser pump combined with capillary evaporator pump to form heat exchanger circulating heat-transfer fluids in both loops. Transport of heat more nearly isothermal. Thermal stress in loop reduced, and less external surface area needed in condenser section for rejection of heat to heat sink.

Magnetohydrodynamic flow and heat transfer around a heated cylinder of arbitrary conductivity

Science.gov (United States)

Tassone, A.; Nobili, M.; Caruso, G.

2017-11-01

The interaction of the liquid metal with the plasma confinement magnetic field constitutes a challenge for the design of fusion reactor blankets, due to the arise of MHD effects: increased pressure drops, heat transfer suppression, etc. To overcome these issues, a dielectric fluid can be employed as coolant for the breeding zone. A typical configuration involves pipes transverse to the liquid metal flow direction. This numerical study is conducted to assess the influence of pipe conductivity on the MHD flow and heat transfer. The CFD code ANSYS CFX was employed for this purpose. The fluid is assumed to be bounded by rectangular walls with non-uniform thickness and subject to a skewed magnetic field with the main component aligned with the cylinder axis. The simulations were restricted to Re = (20; 40) and M = (10; 50). Three different scenarios for the obstacle were considered: perfectly insulating, finite conductivity and perfectly conducting. The electrical conductivity was found to affect the channel pressure penalty due to the obstacle insertion only for M = 10 and just for the two limiting cases. A general increment of the heat transfer with M was found due to the tendency of the magnetic field to equalize the flow rate between the sub-channels individuated by the pipe. The best results were obtained with the insulating pipe, due to the reduced electromagnetic drag. The generation of counter-rotating vortices close to the lateral duct walls was observed for M = 50 and perfectly conducting pipe as a result of the modified currents distribution.

The determination of oxygen in metals using an impulse heating furnace with a simple transfer lock

International Nuclear Information System (INIS)

Dale, L.S.; de Jong, S.; Kelly, J.W.; Whittem, R.N.

1975-05-01

An impulse heating furnace has been constructed for the determination of low levels of oxygen down to 100 μg g -1 in metals. The furnace is equipped with a sample transfer lock which permits samples to be loaded into outgassed crucibles in a helium atmosphere. As a result, blank levels in the range 2 to 3 μg oxygen are obtained; the modification also results in shorter sample processing time. The apparatus is described, and its suitability for oxygen determinations at these levels has been verified by comparison of results obtained on reference and analysed materials. (author)

A pump/intermediate heat exchanger assembly for a liquid metal reactor

International Nuclear Information System (INIS)

Nathenson, R.D.; Alexion, C.C.; Sumpman, W.C.

1987-01-01

A heat exchanger and electromagnetic pump assembly is disclosed comprising a heat exchanger housing defining an annularly shaped cavity and supporting therein a plurality of heat transfer tubes. An electromagnetic pump disposed beneath the heat exchanger comprises a circular array of flow couplers. Each flow coupler comprises a pump duct receiving primary liquid metal and a generator duct receiving a pumped intermediate liquid metal. A first plenum chamber is in communication with the generator ducts of all the flow couplers and receives intermediate liquid metal from inlet duct. The generator ducts exit their flows of intermediate liquid metal to a second plenum chamber in communication with the heat exchanger annularly shaped cavity to permit the flow of the intermediate liquid metal therethrough. A third plenum chamber receives collectively the flows of the primary liquid metal from the tubes and directs the primary liquid metal to the pump ducts of the flow couplers. The annular magnetic field of the electromagnetic pump is produced by a circular array of electromagnets having hollow windings cooled by a flow of intermediate liquid metal via tubes and manifolds. The leads to the electromagnets pass through an annular space around the inlet duct. (author)

Radiation effects on heat transfer in heat exchangers, (2)

International Nuclear Information System (INIS)

Mori, Yasuo; Watanabe, Kenji; Taira, Tatsuji.

1980-01-01

In a high temperature gas-cooled reactor system, in which the working fluid exchanges heat at high temperature near 1000 deg C, the heat transfer acceleration by positively utilizing the radiation heat transfer between solid surfaces should be considered. This paper reports on the results of experiment and analysis for the effects of radiant heat on the heat transfer performance at elevated temperature by applying the heat transfer-accelerating method using radiators to the heat exchanger with tube bundle composed of two channels of heating and heated sides. As the test heat exchangers, a parallel counter flow exchanger and the cross flow exchanger simulating helical tubes were employed, and the results studied on the characteristics of each heat exchanger are described. The plates placed in parallel to flow in every space of the tube bundle arranged in a matrix were used as the heat transfer accelerator. The effects of acceleration with the plates were the increase of heat transmission from 12 to 24% and 12 to 38% in the parallel flow and cross flow heat exchangers, respectively. Also, it was clarified that the theoretical analysis, in which it was assumed that the region within pitch S and two radiator plates, with a heat-transferring tube placed at the center, is the minimum domain for calculation, and that the heat exchange by radiation occurs only between the domain and the adjacent domains, can estimate the heat transfer-accelerating effect and the temperature distribution in a heat exchanger with sufficient accuracy. (Wakatsuki, Y.)

Effect of fluid-to-structure heat transfer on the structural damage potential to a liquid-metal fast breeder reactor

International Nuclear Information System (INIS)

Hakim, S.J.; Abramson, P.B.

1979-01-01

Deterministic calculations simulating a hypothetical accident in a liquid-metal fast breeder reactor that leads to a hydrodynamic disassembly of the core have been carried out to estimate the system's damage potential due to the vapor-pressure-driven expansion of molten core material and its dependency on the heat transfer to the remaining structure. These calculations ignored the effect on the work potential of sodium left in the core during the disassembly. Results indicate that steel cladding in the upper axial blankets and fission gas plenum acts as a thermodynamic energy sink that could reduce the total thermodynamic work energy by between one and two orders of magnitude, provided little or no sodium is present in the core at the time of interaction. These results have been found to be insensitive to the rate of heat transferred from the molten fuel to the molten steel that comprises the molten core material

Conference on heat mass transfer and properties of liquid metals TF-2002

International Nuclear Information System (INIS)

Efanov, A.D.; Kozlov, F.A.

2003-01-01

Results of the conference TF-2002 devoted to the combined approach to problems of harnessing liquid metals as coolants for NPU are presented. The conference takes place in Obninsk, 29 - 31 October, 2002. Papers of the conference involve items on thermal hydraulics, mass transfer and safety of NPU with liquid metal coolants, structure, physical and chemical properties of liquid metal and liquid metal solutions, decommissioning of units and ecology, application of liquid metals divorced with NPU. Most of the papers of the conference are devoted to the investigation into lead and lead-bismuth coolants [ru

Thin film heat flux sensors for accurate transient and unidirectional heat transfer analysis

International Nuclear Information System (INIS)

Azerou, B; Garnier, B; Lahmar, J

2012-01-01

Heat flux measurement is needed in many heat transfer studies. For the best unbiased heat flux sensors (HFS), the heat flux is obtained using temperature measurements at different locations and also an inverse heat conduction method (function specification...) in order to calculate the heat flux. Systematic errors can come from the uncertainty in the wire thermocouples locations and from errors in the knowledge of distances between two consecutive wire thermocouples. The main idea in this work is to use thin film thermoresistances deposited on a flexible thin polymer substrate instead of wire thermocouples welded on metallic sample. The interest of using thin film thermoresistances instead of wire thermocouples is a lower disturbance due to the smaller thickness of the thin film sensors (typically less than 1μm) and a much better knowledge of the distances between the different thin film thermoresistances which are precisely defined in the mask used for the metallic thin film pattern fabrication. In this paper, we present the fabrication of the new heat flux sensor with thin film thermoresistances, the study of the effect of the self heating (due to Joule effect in thermoresistances) and the performances of this new HFS with the comparison with classical HFS using wire thermocouples. For this study, a symmetric experimental setup is used with metallic samples equipped with an etched foil heater and both classical and new HFS. For several heating conditions, it appears that a better accuracy is always obtained with the new HFS using thin film thermoresistances.

Numerical Simulations of Particle Deposition in Metal Foam Heat Exchangers

Science.gov (United States)

Sauret, Emilie; Saha, Suvash C.; Gu, Yuantong

2013-01-01

Australia is a high-potential country for geothermal power with reserves currently estimated in the tens of millions of petajoules, enough to power the nation for at least 1000 years at current usage. However, these resources are mainly located in isolated arid regions where water is scarce. Therefore, wet cooling systems for geothermal plants in Australia are the least attractive solution and thus air-cooled heat exchangers are preferred. In order to increase the efficiency of such heat exchangers, metal foams have been used. One issue raised by this solution is the fouling caused by dust deposition. In this case, the heat transfer characteristics of the metal foam heat exchanger can dramatically deteriorate. Exploring the particle deposition property in the metal foam exchanger becomes crucial. This paper is a numerical investigation aimed to address this issue. Two-dimensional (2D) numerical simulations of a standard one-row tube bundle wrapped with metal foam in cross-flow are performed and highlight preferential particle deposition areas.

Heat transfer from internally heated hemispherical pools

International Nuclear Information System (INIS)

Gabor, J.D.; Ellsion, P.G.; Cassulo, J.C.

1980-01-01

Experiments were conducted on heat transfer from internally heated ZnSO 4 -H 2 O pools to the walls of hemispherical containers. This experimental technique provides data for a heat transfer system that has to date been only theoretically treated. Three different sizes of copper hemispherical containers were used: 240, 280, 320 mm in diameter. The pool container served both as a heat transfer surface and as an electrode. The opposing electrode was a copper disk, 50 mm in diameter located at the top of the pool in the center. The top surface of the pool was open to the atmosphere

Performance investigations of liquid-metal heat pipes for space and terrestrial applications

International Nuclear Information System (INIS)

Kemme, J.E.; Keddy, E.S.; Phillips, J.R.

1978-01-01

The high heat transfer capacity of liquid-metal heat pipes is demonstrated in performance tests with mercury, potassium, sodium, and lithium working fluids and wick structures which serve to minimize liquid pressure losses and vapor/liquid interactions. Appropriate wicks for horizontal and vertical operation are described. It is shown that heat-transfer with these wicks is limited by vapor flow effects. Examples are given of particular effects associated with a long adiabatic section between evaporator and condenser and with a heat source of uniform temperature as opposed to a source of uniform power

Transient non-boiling heat transfer in a fuel rod bundle during accidental power excursions

International Nuclear Information System (INIS)

Bonaekdarzadeh, S.; Johannsen, K.; Ramm, H.

1977-01-01

The physical problem studied is the transient non-boiling heat transfer of a cylindrical fuel rod consisting of fuel, gap, and cladding to a steady, fully developed turbulent flow. The fuel pin is assumed to be located in the interior region of a subassembly with regular triangular or square arrangements. The turbulent velocity field as well as turbulent transport properties are specified as functions of the coordinates normal to the axial flow direction. The heat generation within the fuel may be specified as an arbitrary function of the three spatial coordinates and time. A digital computer program has been developed. On the basis of finite-difference techniques, to solve the governing partial differential equations with their associated subsidiary conditions. Results have been obtained for a series of exponential power transients of interest to safety of liquid-metal and water cooled nuclear reactors. The general physical features of transient convective heat transfer as explored by previous investigators have qualitatively been substantiated by the present analysis. Emphasis has been devoted to investigate the differences of heat-transfer (coefficient) results from multi-region analysis including a realistic fuel rod model and single-region analysis for the coolant region only. A comparison with the engineering relationships for turbulent liquid-metal cooling by Stein, which are an extension of the heat transfer coefficient concept to account for transient heat fluxes, clearly demonstrates that, at the parameters studied, Stein's approach tends to largely overestimate the convective heat transfer at early times

Heat transfer from two-side heated helical channels

International Nuclear Information System (INIS)

Shimonis, V.; Ragaishis, V.; Poshkas, P.

1995-01-01

Experimental results are presented on the heat transfer from two-side heated helical channels to gas (air) flows. The study covered six configurations and wide ranges of geometrical (D/h=5.5 to 84.2) and performance (Re=10 3 to 2*10 5 ) parameters. Under the influence of Re and of the channel curvature, the heat transfer from both the convex and the concave surfaces for two-side heating (q w1 ≅ q w2 ) is augmented by 20-30% over one-side heating. Improved relations to predict the critical values of Reynolds Re cr1 and Re cr2 are suggested. They enable more exact predictions of the heat transfer from convex surface in transient flows for one-side heating. The relation for annular channels is suggested for the turbulent heat transfer from the convex and concave surfaces of two-side heated helical channels. It can be adapted by introducing earlier expresions for one-side heated helical channels. (author). 6 refs., 2 tabs., 3 figs

Numerical simulation of the alloying process during impulse induction heating of the metal substrate

Science.gov (United States)

Popov, V. N.

2017-10-01

2D numerical modeling of the processes during the alloying of the substrate surface metal layer is carried out. Heating, phase transition, heat and mass transfer in the molten metal, solidification of the melt are considered with the aid the proposed mathematical model. Under study is the applicability of the high-frequency electromagnetic field impulse for metal heating and melting. The distribution of the electromagnetic energy in the metal is described by empirical formulas. According to the results of numerical experiments, the flow structure in the melt and distribution of the alloying substances is evaluated.

Convection heat transfer

CERN Document Server

Bejan, Adrian

2013-01-01

Written by an internationally recognized authority on heat transfer and thermodynamics, this second edition of Convection Heat Transfer contains new and updated problems and examples reflecting real-world research and applications, including heat exchanger design. Teaching not only structure but also technique, the book begins with the simplest problem solving method (scale analysis), and moves on to progressively more advanced and exact methods (integral method, self similarity, asymptotic behavior). A solutions manual is available for all problems and exercises.

Heat transfer 1990. Proceedings of the ninth international heat transfer conference

International Nuclear Information System (INIS)

Hetsroni, G.

1990-01-01

This book contains the proceedings of the Ninth International Heat Transfer Conference. Included in Volume 3 are the following chapters: Refrigerant vapor condensation on a horizontal tube bundle. Local heat transfer in a reflux condensation inside a closed two-phase thermosyphon and surface temperature by means of a pulsed photothermal effects

Numerical modeling of heat transfer during hydrogen absorption in thin double-layered annular ZrCo beds

Directory of Open Access Journals (Sweden)

Yehui Cui

2018-06-01

Full Text Available In this work a three-dimensional (3D hydrogen absorption model was proposed to study the heat transfer behavior in thin double-layered annular ZrCo beds. Numerical simulations were performed to investigate the effects of conversion layer thickness, thermal conductivity, cooling medium and its flow velocity on the efficiency of heat transfer. Results reveal that decreasing the layer thickness and improving the thermal conductivity enhance the ability of heat transfer. Compared with nitrogen and helium, water appears to be a better medium for cooling. In order to achieve the best efficiency of heat transfer, the flow velocity needs to be maximized. Keywords: Hydrogen storage, ZrCo metal hydride, Heat transfer, Three-dimensional simulation

The inaccuracy of heat transfer characteristics for non-insulated and insulated spherical containers neglecting the influence of heat radiation

International Nuclear Information System (INIS)

Wong, King-Leung; Salazar, Jose Luis Leon; Prasad, Leo; Chen, Wen-Lih

2011-01-01

In this investigation, the differences of heat transfer characteristics for insulated and non-insulated spherical containers between considering and neglecting the influence of heat radiation are studied by the simulations in some practical situations. It is found that the heat radiation effect cannot be ignored in conditions of low ambient convection heat coefficients (such ambient air) and high surface emissivities, especially for the non-insulated and thin insulated cases. In most practical situations when ambient temperature is different from surroundings temperature and the emissivity of insulation surface is different from that of metal wall surface, neglecting heat radiation will result in inaccurate insulation effect and heat transfer errors even with very thick insulation. However, the insulation effect considering heat radiation will only increase a very small amount after some dimensionless insulated thickness (such insulation thickness/radius ≥0.2 in this study), thus such dimensionless insulated thickness can be used as the optimum thickness in practical applications. Meanwhile, wrapping a material with low surface emissivity (such as aluminum foil) around the oxidized metal wall or insulation layer (always with high surface emissivity) can achieve very good insulated effect for the non-insulated or thin insulated containers.

Heat transfer across the interface between nanoscale solids and gas.

Science.gov (United States)

Cheng, Chun; Fan, Wen; Cao, Jinbo; Ryu, Sang-Gil; Ji, Jie; Grigoropoulos, Costas P; Wu, Junqiao

2011-12-27

When solid materials and devices scale down in size, heat transfer from the active region to the gas environment becomes increasingly significant. We show that the heat transfer coefficient across the solid-gas interface behaves very differently when the size of the solid is reduced to the nanoscale, such as that of a single nanowire. Unlike for macroscopic solids, the coefficient is strongly pressure dependent above ∼10 Torr, and at lower pressures it is much higher than predictions of the kinetic gas theory. The heat transfer coefficient was measured between a single, free-standing VO(2) nanowire and surrounding air using laser thermography, where the temperature distribution along the VO(2) nanowire was determined by imaging its domain structure of metal-insulator phase transition. The one-dimensional domain structure along the nanowire results from the balance between heat generation by the focused laser and heat dissipation to the substrate as well as to the surrounding gas, and thus serves as a nanoscale power-meter and thermometer. We quantified the heat loss rate across the nanowire-air interface, and found that it dominates over all other heat dissipation channels for small-diameter nanowires near ambient pressure. As the heat transfer across the solid-gas interface is nearly independent of the chemical identity of the solid, the results reveal a general scaling relationship for gaseous heat dissipation from nanostructures of all solid materials, which is applicable to nanoscale electronic and thermal devices exposed to gaseous environments.

Selection of Rational Heat Transfer Intensifiers in the Heat Exchanger

Directory of Open Access Journals (Sweden)

S. A. Burtsev

2016-01-01

Full Text Available The paper considers the applicability of different types of heat transfer intensifiers in the heat exchange equipment. A review of the experimental and numerical works devoted to the intensification of the dimpled surface, surfaces with pins and internally ribbed surface were presented and data on the thermal-hydraulic characteristics of these surfaces were given. We obtained variation of thermal-hydraulic efficiency criteria for 4 different objective functions and 15 options for the intensification of heat transfer. This makes it possible to evaluate the advantages of the various heat transfer intensifiers. These equations show influence of thermal and hydraulic characteristics of the heat transfer intensifiers (the values of the relative heat transfer and drag coefficients on the basic parameters of the shell-and-tube heat exchanger: the number and length of the tubes, the volume of the heat exchanger matrix, the coolant velocity in the heat exchanger matrix, coolant flow rate, power to pump coolant (or pressure drop, the amount of heat transferred, as well as the average logarithmic temperature difference. The paper gives an example to compare two promising heat transfer intensifiers in the tubes and shows that choosing the required efficiency criterion to search for optimal heat exchanger geometry is of importance. Analysis is performed to show that a dimpled surface will improve the effectiveness of the heat exchanger despite the relatively small value of the heat transfer intensification, while a significant increase in drag of other heat transfer enhancers negatively affects their thermalhydraulic efficiency. For example, when comparing the target functions of reducing the heat exchanger volume, the data suggest that application of dimpled surfaces in various fields of technology is possible. But there are also certain surfaces that can reduce the parameters of a heat exchanger. It is shown that further work development should be aimed at

Heat transfer in an asymmetrically heated duct, 2

International Nuclear Information System (INIS)

Satoh, Isao; Kurosaki, Yasuo

1986-01-01

The objective of this article is to study theoretically and experimentally the effects of nonuniform heating on turbulent heat transfer characteristics for flow in a horizontal rectangular duct ; a vertical side wall was uniformly heated, and the other wall were insulated. In our theoretical approach, the zero-equation model for turbulent eddy viscosity was employed. The effects of mesh size of finite difference on the calculation results were examined, and some refined compensation for wall temperatures and wall shear stresses by no use of fine mesh were proposed to reduce the calculation time. The heat transfer coefficients in thermally developing region for a nonuniformly heated duct obtained from numerical solutions are larger than the one for uniformly heated case. The buoyancy effects on heat transfer were evaluated. However, it was seen that the secondary flow due to buoyancy force was hardly expected to enhance heat transfer in a turbulent duct flow. Experiments were performed to measure the velocity and temperature profiles in a turbulent duct flow with a nonuniform heated wall. The experimental results were in good agreement with the theoretical ones. (author)

Experimental analysis for heat transfer of nanofluid with wire coil turbulators in a concentric tube heat exchanger

Science.gov (United States)

Akyürek, Eda Feyza; Geliş, Kadir; Şahin, Bayram; Manay, Eyüphan

2018-06-01

Nanofluids are a novel class of heat transfer suspensions of metallic or nonmetallic nanopowders with a size of less than 100 nm in base fluids and they can increase heat transfer potential of the base fluids in various applications. In the last decade, nanofluids have become an intensive research topic because of their improved thermal properties and possible heat transfer applications. For comparison, an experiment using water as the working fluid in the heat exchanger without wire coils was also performed. Turbulent forced convection heat transfer and pressure drop characteristics of Al2O3-water nanofluids in a concentric tube heat exchanger with and without wire coil turbulators were experimentally investigated in this research. Experiments effected particle volume concentrations of 0.4-0.8 to 1.2-1.6 vol% in the Reynolds number range from 4000 to 20,000. Two turbulators with the pitches of 25 mm and 39 mm were used. The average Nusselt number increased with increasing the Reynolds number and particle concentrations. Moreover, the pressure drop of the Al2O3-water nanofluid showed nearly equal to that of pure water at the same Reynolds number range. As a result, nanofluids with lower particle concentrations did not show an important influence on pressure drop change. Nonetheless, when the wire coils used in the heat exchanger, it increased pressure drop as well as the heat transfer coefficient.

Local Heat Transfer and CHF for Subcooled Flow Boiling - Annual Report 1993

International Nuclear Information System (INIS)

Boyd, Ronald D.

2000-01-01

Subcooled flow boiling in heated coolant channels is an important heat transfer enhancement technique in the development of fusion reactor components, where high heat fluxes must be accommodated. As energy fluxes increase in magnitude, additional emphasis must be devoted to enhancing techniques such as sub cooling and enhanced surfaces. In addition to subcooling, other high heat flux alternatives such as high velocity helium and liquid metal cooling have been considered as serious contenders. Each technique has its advantages and disadvantages [1], which must be weighed as to reliability and reduced cost of fusion reactor components. Previous studies [2] have set the stage for the present work, which will concentrate on fundamental thermal hydraulic issues associated with the h-international Thermonuclear Experimental Reactor (ITER) and the Engineering Design Activity (EDA). This proposed work is intended to increase our understanding of high heat flux removal alternatives as well as our present capabilities by: (1) including single-side heating effects in models for local predictions of heat transfer and critical heat flux; (2) inspection of the US, Japanese, and other possible data sources for single-side heating, with the aim of exploring possible correlations for both CHF and local heat transfer; and (3) assessing the viability of various high heat flux removal techniques. The latter task includes: (a) sub-cooled water flow boiling with enhancements such as twisted tapes, and hypervapotrons, (b) high velocity helium cooling, and (c) other potential techniques such as liquid metal cooling. This assessment will increase our understanding of: (1) hypervapotron heat transfer via fins, flow recirculation, and flow oscillation, and (2) swirl flow. This progress report contains selective examples of ongoing work. Section II contains an extended abstract, which is part of and evolving technical paper on single-side f heating. Section III describes additional details

Heat transfer--Orlando (Symposium), 1980

International Nuclear Information System (INIS)

Stein, R.P.

1980-01-01

This conference proceedings contains 36 papers of which 3 appear as abstracts. 23 papers are indexed separately. Topics covered include: thermodynamics of PWR and LMFBR Steam Generators; two-phase flow in parallel channels; geothermal heat transfer; natural circulation in complex geometries; heat transfer in non-Newtonian systems; and process heat transfer

Containment condensing heat transfer

International Nuclear Information System (INIS)

Gido, R.G.; Koestel, A.

1983-01-01

This report presents a mechanistic heat-transfer model that is valid for large scale containment heat sinks. The model development is based on the determination that the condensation is controlled by mass diffusion through the vapor-air boundary layer, and the application of the classic Reynolds' analogy to formulate expressions for the transfer of heat and mass based on hydrodynamic measurements of the momentum transfer. As a result, the analysis depends on the quantification of the shear stress (momentum transfer) at the interface between the condensate film and the vapor-air boundary layer. In addition, the currently used Tagami and Uchida test observations and their range of applicability are explained

Heat transfer enhancement for fin-tube heat exchanger using vortex generators

International Nuclear Information System (INIS)

Yoo, Seong Yeon; Park, Dong Seong; Chung, Min Ho; Lee, Sang Yun

2002-01-01

Vortex generators are fabricated on the fin surface of a fin-tube heat exchanger to augment the convective heat transfer. In addition to horseshoe vortices formed naturally around the tube of the fin-tube heat exchanger, longitudinal vortices are artificially created on the fin surface by vortex generators. The purpose of this study is to investigate the local heat transfer phenomena in the fin-tube heat exchangers with and without vortex generators, and to evaluate the effect of vortices on the heat transfer enhancement. Naphthalene sublimation technique is employed to measure local mass transfer coefficients, then analogy equation between heat and mass transfer is used to calculate heat transfer coefficients. Experiments are performed for the model of fin-circular tube heat exchangers with and without vortex generators, and of fin-flat tube heat exchangers with and without vortex generators. Average heat transfer coefficients of fin-flat tube heat exchanger without vortex generator are much lower than those of fin-circular tube heat exchanger. On the other hand, fin-flat tube heat exchanger with vortex generators has much higher heat transfer value than conventional fin-circular tube heat exchanger. At the same time, pressure losses for four types of heat exchanger is measured and compared

Radiation and combined heat transfer in channels

International Nuclear Information System (INIS)

Tamonis, M.

1986-01-01

This book presents numerical methods of calculation of radiative and combined heat transfer in channel flows of radiating as well as nonradiating media. Results obtained in calculations for flow conditions of combustion products from organic fuel products are given and methods used in determining the spectral optical properties of molecular gases are analyzed. The book presents applications of heat transfer in solving problems. Topic covered are as follows: optical properties of molecular gases; transfer equations for combined heat transfer; experimental technique; convective heat transfer in heated gas flows; radiative heat transfer in gaseous media; combined heat transfer; and radiative and combined heat transfer in applied problems

Generalized irreversible heat-engine experiencing a complex heat-transfer law

International Nuclear Information System (INIS)

Chen Lingen; Li Jun; Sun Fengrui

2008-01-01

The fundamental optimal relation between optimal power-output and efficiency of a generalized irreversible Carnot heat-engine is derived based on a generalized heat-transfer law, including a generalized convective heat-transfer law and a generalized radiative heat-transfer law, q ∝ (ΔT n ) m . The generalized irreversible Carnot-engine model incorporates several internal and external irreversibilities, such as heat resistance, bypass heat-leak, friction, turbulence and other undesirable irreversibility factors. The added irreversibilities, besides heat resistance, are characterized by a constant parameter and a constant coefficient. The effects of heat-transfer laws and various loss terms are analyzed. The results obtained corroborate those in the literature

Effect of thermodiffusion on the fluid flow, heat transfer, and solidification of molten metal alloys

Directory of Open Access Journals (Sweden)

E. Jafar-Salehi

2016-03-01

Full Text Available In this paper, a transient Finite Element (FE method has been employed to solve the transport equations to investigate the heat transfer and fluid flow and the effect of thermodiffusion on vertical solidification of a binary molten metal alloy, forming a rod. The binary system considered in this study is SnBi composed of 65% Sn and 35% Bi subjected to bottom cooling. It is found that the flow of molten metal at the boundary of the mushy region plays an important role in the shape and geometry of the zone. The presence of thermodiffusion shows considerable difference in the composition of the solidified rod, compared with the one without considering the effect of thermodiffusion. Thermodiffusion also causes a faster solidification and a more uniform concentration distribution. The results of this study may be extended to similar binary and multicomponent systems in which a temperature gradient exists and the Soret coefficient is large enough so as to affect the fluid flow and concentration of the species.

Numerical Simulation of Steady State Conduction Heat Transfer During the Solidification of Aluminum Casting in Green Sand Mould

Directory of Open Access Journals (Sweden)

Victor ANJO

2012-08-01

Full Text Available The solidification of molten metal during the casting process involves heat transfer from the molten metal to the mould, then to the atmosphere. The mechanical properties and grain size of metals are determined by the heat transfer process during solidification. The aim of this study is to numerically stimulate the steady conduction heat transfer during the solidification of aluminum in green sand mould using finite difference analysis 2D. The properties of materials used are industrial AI 50/60 AFS green sand mould, pure aluminum and MATLAB 7.0.1. for the numerical simulation. The method includes; the finite difference analysis of the heat conduction equation in steady (Laplace’s and transient states and using MATLAB to numerically stimulate the thermal flow and cooling curve. The results obtained are: the steady state thermal flow in 2D and transient state cooling curve of casting. The results obtain were consider relevant in the control of the grain size and mechanical properties of the casting.

Heat transfer study under supercritical pressure conditions

International Nuclear Information System (INIS)

Yamashita, Tohru; Yoshida, Suguru; Mori, Hideo; Morooka, Shinichi; Komita, Hideo; Nishida, Kouji

2003-01-01

Experiments were performed on heat transfer and pressure drop of a supercritical pressure fluid flowing upward in a uniformly heated vertical tube of a small diameter, using HCFC22 as a test fluid. Following results were obtained. (1) Characteristics of the heat transfer are similar to those for the tubes of large diameter. (2) The effect of tube diameter on the heat transfer was seen for a 'normal heat transfer, but not for a 'deteriorated' heat transfer. (3) The limit heat flux for the occurrence of deterioration in heat transfer becomes larger with smaller diameter tube. (4) The Watts and Chou correlation has the best prediction performance for the present data in the 'normal' heat transfer region. (5) Frictional pressure drop becomes smaller than that for an isothermal flow in the region near the pseudocritical point, and this reduction was more remarkable for the deteriorated' heat transfer. (author)

Control of the electrode metal transfer by means of the welding current pulse generator

Science.gov (United States)

Knyaz'kov, A.; Pustovykh, O.; Verevkin, A.; Terekhin, V.; Shachek, A.; Knyaz'kov, S.; Tyasto, A.

2016-04-01

The paper presents a generator of welding current pulses to transfer an electrode metal into the molten pool. A homogeneous artificial line is used to produce near rectangular pulses. The homogeneous artificial line provides the minimum heat input with in the pulse to transfer the electrode metal, and it significantly decreases the impact of disturbances affecting this transfer. The pulse frequency does not exceed 300 Hz, and the duration is 0.6 ÷ 0.9 ms.

Survey of studies on the flow and heat transfer of two-component, two-phase flow of liquid metal in magnetic field

International Nuclear Information System (INIS)

Kumamaru, Hiroshige

1980-01-01

Brief review of the studies on the flow and heat transfer of two-component, two-phase flow of liquid metal in magnetic field is presented. R.J. Thome measured the distribution of void rate, slip ratio and pressure loss for the two-phase flow of NaK-N 2 under vertical magnetic field. The void rate distribution became even and the slip ratio increased with the increasing magnetic field. The experimental results of pressure loss was compared with the calculation by an equation derived from the homogeneous flow model. R.G. Owen et al. made the analytical studies of the MHD friction loss of two phase flow. Michiyoshi et al. made experimental studies on the hydrodynamic local properties of Hg-Ar two-phase flow of slug region in a vertically ascending tube under magnetic field, and Kimi et al. also made studies on the heat transfer of Hg-Ar flow under magnetic field. Saito et al. measured the slip ratio and pressure loss of NaK-N 2 flow. As a whole, it can be said that the average void rate decreases, and its distribution becomes even under magnetic field. The slip ratio increases, and the friction loss factor becomes nearly one. It was hard to make clear the heat transfer characteristics. (Kato, T.)

Heat transfer analysis of ZnO-water nanofluid for nuclear application

International Nuclear Information System (INIS)

Pattanayak, Bikash; Mund, Abhishek; Jayakumar, J.S.; Chaudhuri, P.; Parashar, Kajal; Parashar, S.K.S.

2017-01-01

The thermal conductivity of traditional heat transfer fluids is inherently low. Metals or metal oxide in ultra-fine form have orders of magnitudes higher thermal conductivity of those of fluids. So it is a need to understand the fundamental behavior of the metals or metal oxides nanoparticles in base fluids. ZnO is a semiconductor but has a wide range of application. In this study the thermal conductivity and viscosity will be discussed in details with experimental and theoretical models. The application of ZnO based nanofluids will be very much useful in nuclear fusion

Charge transfer in gold--alkali-metal systems

International Nuclear Information System (INIS)

Watson, R.E.; Weinert, M.

1994-01-01

Based on conventional electronegativity arguments, gold--alkali-metal compounds are expected to be among the most ''ionic'' of metallic compounds. The concepts of ionicity and charge transfer are difficult to quantify. However, the changes in bonding in the 50/50 Au--alkali-metal systems between the elemental metals and the compounds are so severe that observations can readily be made concerning their character. The results, as obtained from self-consistent electronic-structure calculations, lead to the apparently odd observation that the electron density at the alkali-metal sites in the compound increases significantly and this involves high l componennts in the charge density. This increase, however, can be attributed to Au-like orbitals spatially overlapping the alkali-metal sites. In a chemical sense, it is reasonable to consider the alkali-metal transferring charge to these Au orbitals. While normally the difference in heats of formation between muffin-tin and full-potential calculations for transition-metal--transition-metal and transition-metal--main-group (e.g., Al) compounds having high site symmetry are small, for the gold--alkali-metal systems, the changes in bonding in the compounds cause differences of ∼0.5 eV/atom between the two classes of potential. Any serious estimate of the electronic structure in these systems must account for these aspherical bonding charges. The origin of the semiconducting behavior of the heavy-alkali-metal Au compounds is shown to arise from a combination of the Au-Au separations and the ionic character of the compounds; the light-alkali-metal Au compounds, with their smaller Au-Au separations, do not have a semiconducting gap. Core-level shifts and isomer shifts are also briefly discussed

Heat transfer in Rockwool modelling and method of measurement. Modelling radiative heat transfer in fibrous materials

Energy Technology Data Exchange (ETDEWEB)

Dyrboel, Susanne

1998-05-01

Fibrous materials are some of the most widely used materials for thermal insulation. In this project the focus of interest has been on fibrous materials for building application. Interest in improving the thermal properties of insulation materials is increasing as legislation is being tightened to reduce the overall energy consumption. A knowledge of the individual heat transfer mechanisms - whereby heat is transferred within a particular material is an essential tool to improve continuously the thermal properties of the material. Heat is transferred in fibrous materials by four different transfer mechanisms: conduction through air, conduction through fibres, thermal radiation and convection. In a particular temperature range the conduction through air can be regarded as a constant, and conduction through fibres is an insignificant part of the total heat transfer. Radiation, however, constitutes 25-40% of the total heat transfer in light fibrous materials. In Denmark and a number of other countries convection in fibrous materials is considered as non-existent when calculating heat transmission as well as when designing building structures. Two heat transfer mechanisms have been the focus of the current project: radiation heat transfer and convection. The radiation analysis serves to develop a model that can be used in further work to gain a wider knowledge of the way in which the morphology of the fibrous material, i.e. fibre diameter distribution, fibre orientation distribution etc., influences the radiation heat transfer under different conditions. The convection investigation serves to examine whether considering convection as non-existent is a fair assumption to use in present and future building structures. The assumption applied in practically is that convection makes a notable difference only in very thick insulation, at external temperatures below -20 deg. C, and at very low densities. For lager thickness dimensions the resulting heat transfer through the

Test facility for investigation of heat transfer of promising coolants for the nuclear power industry

Science.gov (United States)

Belyaev, I. A.; Sviridov, V. G.; Batenin, V. M.; Biryukov, D. A.; Nikitina, I. S.; Manchkha, S. P.; Pyatnitskaya, N. Yu.; Razuvanov, N. G.; Sviridov, E. V.

2017-11-01

The results are presented of experimental investigations into liquid metal heat transfer performed by the joint research group consisting of specialist in heat transfer and hydrodynamics from NIU MPEI and JIHT RAS. The program of experiments has been prepared considering the concept of development of the nuclear power industry in Russia. This concept calls for, in addition to extensive application of water-cooled, water-moderated (VVER-type) power reactors and BN-type sodium cooled fast reactors, development of the new generation of BREST-type reactors, fusion power reactors, and thermonuclear neutron sources. The basic coolants for these nuclear power installations will be heavy liquid metals, such as lead and lithium-lead alloy. The team of specialists from NRU MPEI and JIHT RAS commissioned a new RK-3 mercury MHD-test facility. The major components of this test facility are a unique electrical magnet constructed at Budker Nuclear Physics Institute and a pressurized liquid metal circuit. The test facility is designed for investigating upward and downward liquid metal flows in channels of various cross-sections in a transverse magnetic field. A probe procedure will be used for experimental investigation into heat transfer and hydrodynamics as well as for measuring temperature, velocity, and flow parameter fluctuations. It is generally adopted that liquid metals are the best coolants for the Tokamak reactors. However, alternative coolants should be sought for. As an alternative to liquid metal coolants, molten salts, such as fluorides of lithium and beryllium (so-called FLiBes) or fluorides of alkali metals (so-called FLiNaK) doped with uranium fluoride, can be used. That is why the team of specialists from NRU MPEI and JIHT RAS, in parallel with development of a mercury MHD test facility, is designing a test facility for simulating molten salt heat transfer and hydrodynamics. Since development of this test facility requires numerical predictions and verification

Stokes flow heat transfer in an annular, rotating heat exchanger

International Nuclear Information System (INIS)

Saatdjian, E.; Rodrigo, A.J.S.; Mota, J.P.B.

2011-01-01

The heat transfer rate into highly viscous, low thermal-conductivity fluids can be enhanced significantly by chaotic advection in three-dimensional flows dominated by viscous forces. The physical effect of chaotic advection is to render the cross-sectional temperature field uniform, thus increasing both the wall temperature gradient and the heat flux into the fluid. A method of analysis for one such flow-the flow in the eccentric, annular, rotating heat exchanger-and a procedure to determine the best heat transfer conditions, namely the optimal values of the eccentricity ratio and time-periodic rotating protocol, are discussed. It is shown that in continuous flows, such as the one under consideration, there exists an optimum frequency of the rotation protocol for which the heat transfer rate is a maximum. - Highlights: → The eccentric, annular, rotating heat exchanger is studied for periodic Stokes flow. → Counter-rotating the inner tube with a periodic velocity enhances the heat transfer. → The heat-transfer enhancement under such conditions is due to chaotic advection. → For a given axial flow rate there is a frequency that maximizes the heat transfer. → There is also an optimum value of the eccentricity ratio.

Heat transfer to a particle exposed to a rarefield ionized-gas flow

International Nuclear Information System (INIS)

Chen, X.; He, P.

1986-01-01

Analytical results are presented concerning the heat transfer to a spherical particle exposed to a high temperature, ionized- gas flow for the extreme case of free-molecule flow regime. It has been shown that the presence of relative velocity between the particle and the ionized gas reduces the floating potential on the particle, enhances the heat flux and causes appreciably non-uniform distribution of the local heat flux. Pronounced difference is found between metallic and non-metallic particles in the floating potential and the local heat flux distributions, in particular for the case with high gas-flow temperature. Relative contribution of atoms to the total heat flux is dominant for the case of low gas-flow temperature, while the heat flux is mainly caused by ions and electrons for the case of high gas-flow temperature

Investigations on post-dryout heat transfer in bilaterally heated annular channels

International Nuclear Information System (INIS)

Tian, W.X.; Qiu, S.Z.; Jia, D.N.

2006-01-01

Post-dryout heat transfer in bilaterally heated vertical narrow annular channels with 1.0, 1.5 and 2.0 mm gap size has been experimentally investigated with deionized water under the condition of pressure ranging from 1.38 to 5.9 MPa and low mass flow rate from 42.9 to 150.2 kg/m 2 s. The experimental data was compared with well known empirical correlations including Groeneveld, Mattson, etc., and none of them gave an ideal prediction. Theoretical investigations were also carried out on post-dryout heat transfer in annular channels. Based on analysis of heat exchange processes arising among the droplets, the vapor and two tube walls of annular channel, a non-equilibrium mechanistic heat transfer model was developed. Comparison indicated that the present model prediction showed a good agreement with our experimental data. Theoretical calculation result showed that the forced convective heat transfer between the heated wall and vapor dominate the overall heat transfer. The heat transfer caused by the droplets direct contact to the wall and the interfacial convection/evaporation of droplets in superheated vapors also had an indispensable contribution. The radiation heat transfer would be neglected because of its small contribution (less than 0.11%) to the total heat transfer

A literature survey on numerical heat transfer

Science.gov (United States)

Shih, T. M.

1982-12-01

Technical papers in the area of numerical heat transfer published from 1977 through 1981 are reviewed. The journals surveyed include: (1) ASME Journal of Heat Transfer, (2) International Journal of Heat and Mass Transfer, (3) AIAA Journal, (4) Numerical Heat Transfer, (5) Computers and Fluids, (6) International Journal for Numerical Methods in Engineering, (7) SIAM Journal of Numerical Analysis, and (8) Journal of Computational Physics. This survey excludes experimental work in heat transfer and numerical schemes that are not applied to equations governing heat transfer phenomena. The research work is categorized into the following areas: (A) conduction, (B) boundary-layer flows, (C) momentum and heat transfer in cavities, (D) turbulent flows, (E) convection around cylinders and spheres or within annuli, (F) numerical convective instability, (G) radiation, (H) combustion, (I) plumes, jets, and wakes, (J) heat transfer in porous media, (K) boiling, condensation, and two-phase flows, (L) developing and fully developed channel flows, (M) combined heat and mass transfer, (N) applications, (O) comparison and properties of numerical schemes, and (P) body-fitted coordinates and nonuniform grids.

Heat transfer bibliography: russian works

Energy Technology Data Exchange (ETDEWEB)

Luikov, A V

1965-02-01

This bibliography of recent Russian publications in heat transfer is divided into the following categories: (1) books; (2) general; (3) experimental methods; (4) analytical calculation methods; (5) thermodynamics; (6) transfer processes involving phase conversions; ((7) transfer processes involving chemical conversions; (8) transfer processes involving very high velocities; (9) drying processes; (10) thermal properties of various materials, heat transfer agents and their determination methods; (11) high temperature physics and magneto- hydrodynamics; and (12) transfer processes in technological apparatuses. (357 refs.)

Advances in heat transfer

CERN Document Server

Hartnett, James P; Cho, Young I; Greene, George A

2001-01-01

Heat transfer is the exchange of heat energy between a system and its surrounding environment, which results from a temperature difference and takes place by means of a process of thermal conduction, mechanical convection, or electromagnetic radiation. Advances in Heat Transfer is designed to fill the information gap between regularly scheduled journals and university-level textbooks by providing in-depth review articles over a broader scope than is allowable in either journals or texts.

Graphite curtain vacuum outgassing and heat transfer. Final report

International Nuclear Information System (INIS)

Fivel, H.J.; Lang, G.P.; Kipp, H.W.

1976-12-01

Thermal conductivity of a bundle of high conductivity graphite fibers (T-50) was measured as a function of temperature, density and fiber orientation at pressures of 10 -4 to 10 -5 torr. All 3 variables had a significant influence on thermal conductivity. The highest conductivity fiber bundle tested had a conductivity significantly less than dense, bulk nuclear grade graphite. The incorporation of heat pipes into a graphite spectral shaper will permit a 2-fold thicker shaper. Heat pipes not only increase the transport of heat within the spectral shaper but can increase heat transfer at the shaper-first wall interface and potentially serve as a means of attaching shaper modules to the first wall. A heat pipe using a liquid metal working fluid was fabricated and tested in magnetic fields of 1 and 2 Tesla. Liquid metal heat pipes can be used in a magnetic field of at least up to 2 Tesla. Much more work needs to be done to establish the capabilities for high performance heat pipes when used in magnetic fields. Four different types of graphite fibers were exposed in EBR-II to a neutron fluence of 3.5 x 10 21 cm -2 EFF at 470 0 C. Large axial shrinkages of 6.6 to 8.6% resulted

Heat transfer analysis of frictional heat dissipation during articulation of femoral implants.

Science.gov (United States)

Davidson, J A; Gir, S; Paul, J P

1988-12-01

Previous studies have shown the tendency for frictional heating to occur during articulation of total hip systems in vitro under simulated hip loading conditions. The magnitude of this heating is sufficient to accelerate wear, creep, and oxidation degradation of the UHMWPE bearing surface. It was shown that ceramic articulating systems generate less frictional heating than polished cobalt alloy against UHMWPE. This frictional heating is expected to occur primarily for younger, heavier, and more active patients. Thus, long-term performance of the articulating hip system in these patients may not be that predicted from current, body-temperature wear, creep, and degradation studies. Although the tendency to generate frictional heat has been observed only during in vitro simulated hip loading, a heat transfer analysis of this phenomenon is presented to evaluate the ability of the hip joint to dissipate such heating in vivo. Additional experiments were performed using controlled resistance heaters inside a cobalt femoral head to verify the calculated levels of frictional heat and to assess the heat dissipation under simulated in vivo conditions. The effect of blood perfusion on the effective thermal conductivity of the joint capsule is also discussed. The present study describes and analyzes the various heat dissipation mechanisms present both in vitro and in vivo during articulation of metal and ceramic hip systems. From these tests and analyses, it is concluded that frictional heating in the reconstructed hip cannot be effectively removed, and that degredative elevated temperature processes can be expected to occur in vivo to both the UHMWPE and adjacent tissue under extended periods of excessive patient activity. This is particularly true for metal cobalt alloy femoral heads articulating on UHMWPE versus ceramic heads which generate significantly lower levels of heat.

Heat transfer, condensation and fog formation in crossflow plastic heat exchangers

NARCIS (Netherlands)

Brouwers, H.J.H.

1996-01-01

In this paper heat transfer of air-water-vapour mixtures in plastic crossflow heat exchangers is studied theoretically and experimentally. First, a model for heat transfer without condensation is derived, resulting in a set of classical differential equations. Subsequently, heat transfer with wall

Boiling Heat Transfer to Halogenated Hydrocarbon Refrigerants

Science.gov (United States)

Yoshida, Suguru; Fujita, Yasunobu

The current state of knowledge on heat transfer to boiling refrigerants (halogenated hydrocarbons) in a pool and flowing inside a horizontal tube is reviewed with an emphasis on information relevant to the design of refrigerant evaporators, and some recommendations are made for future research. The review covers two-phase flow pattern, heat transfer characteristics, correlation of heat transfer coefficient, influence of oil, heat transfer augmentation, boiling from tube-bundle, influence of return bend, burnout heat flux, film boiling, dryout and post-dryout heat transfer.

Heat exchanger network retrofit optimization involving heat transfer enhancement

International Nuclear Information System (INIS)

Wang Yufei; Smith, Robin; Kim, Jin-Kuk

2012-01-01

Heat exchanger network retrofit plays an important role in energy saving in process industry. Many design methods for the retrofit of heat exchanger networks have been proposed during the last three decades. Conventional retrofit methods rely heavily on topology modifications which often result in a long retrofit duration and high initial costs. Moreover, the addition of extra surface area to the heat exchanger can prove difficult due to topology, safety and downtime constraints. Both of these problems can be avoided through the use of heat transfer enhancement in heat exchanger network retrofit. This paper presents a novel design approach to solve heat exchanger network retrofit problems based on heat transfer enhancement. An optimisation method based on simulated annealing has been developed to find the appropriate heat exchangers to be enhanced and to calculate the level of enhancement required. The physical insight of enhanced exchangers is also analysed. The new methodology allows several possible retrofit strategies using different retrofit methods be determined. Comparison of these retrofit strategies demonstrates that retrofit modification duration and payback time are reduced when heat transfer enhancement is utilised. Heat transfer enhancement can be also used as a substitute for increased heat exchanger network surface area to reduce retrofit investment costs.

Heat transfer enhancement for spent nuclear fuel assembly disposal packages using metallic void fillers: A prevention technique for solidification shrinkage-induced interfacial gaps

Energy Technology Data Exchange (ETDEWEB)

Park, Yongsoo, E-mail: yspark@alum.mit.edu; McKrell, Thomas J.; Driscoll, Michael J.

2017-06-15

This study considers replacing the externally accessible void spaces inside a disposal package containing a spent nuclear fuel assembly (SNFA) with high heat conducting metal to increase the effective thermal conductivity of the package and simplify the heat transfer mechanism inside the package by reducing it to a conduction dominant problem. The focus of the study is on preventing the gaps adjacent to the walls of the package components, produced by solidification shrinkage of poured liquid metal. We approached the problem by providing a temporary coating layer on the components to avoid direct build-up of thick metal oxides on their surface to promote metallic bonding at the interfaces under a non-inert environment. Laboratory scale experiments without SNFA were performed with Zn coated low carbon steel canisters and Zamak-3 void filler under two different filling temperature conditions – below and above the melting point of Zn (designated BMP and AMP respectively). Gap formation was successfully prevented in both cases while we confirmed an open gap in a control experiment, which used an uncoated canister. Minor growth of Al-Fe intermetallic phases was observed at the canister/filler interface of the sample produced under the BMP condition while their growth was significant and showed irregularly distributed morphology in the sample produced under the AMP condition, which has a potential to mitigate excessive residual stresses caused by shrinkage prevention. A procedure for the full-scale application was specified based on the results. - Highlights: •A void filling technique is introduced to enhance SNFA package heat transfer. •The technique is demonstrated via experiments using the Fe-Al-Zn system. •A procedure for the full scale application is proposed based on the results.

Heat transfer enhancement on nucleate boiling

International Nuclear Information System (INIS)

Zhuang, M.; Guibai, L.

1990-01-01

This paper reports on enhancement of nucleate boiling heat transfer with additives that was investigated experimentally. More than fifteen kinds of additives were chosen and tested. Eight kinds of effective additives which can enhance nucleate boiling heat transfer were selected. Experimental results showed that boiling heat transfer coefficient of water was increased by 1 to 5 times and that of R-113 was increased by 1 to 4 times when trace amount additives were put in the two boiling liquids. There exist optimum concentrations for the additives, respectively, which can enhance nucleate boiling heat transfer rate best. In order to analyze the mechanism of the enhancement of boiling heat transfer with additives, the surface tension and the bubble departure diameter were measured. The nucleation sites were investigated by use of high-speed photograph. Experimental results showed that nucleation sites increase with additive amount increasing and get maximum. Increasing nucleation sites is one of the most important reason why nucleate boiling heat transfer can be enhanced with additives

Heat transfer efficient thermal energy storage for steam generation

International Nuclear Information System (INIS)

Adinberg, R.; Zvegilsky, D.; Epstein, M.

2010-01-01

A novel reflux heat transfer storage (RHTS) concept for producing high-temperature superheated steam in the temperature range 350-400 deg. C was developed and tested. The thermal storage medium is a metallic substance, Zinc-Tin alloy, which serves as the phase change material (PCM). A high-temperature heat transfer fluid (HTF) is added to the storage medium in order to enhance heat exchange within the storage system, which comprises PCM units and the associated heat exchangers serving for charging and discharging the storage. The applied heat transfer mechanism is based on the HTF reflux created by a combined evaporation-condensation process. It was shown that a PCM with a fraction of 70 wt.% Zn in the alloy (Zn70Sn30) is optimal to attain a storage temperature of 370 deg. C, provided the heat source such as solar-produced steam or solar-heated synthetic oil has a temperature of about 400 deg. C (typical for the parabolic troughs technology). This PCM melts gradually between temperatures 200 and 370 deg. C preserving the latent heat of fusion, mainly of the Zn-component, that later, at the stage of heat discharge, will be available for producing steam. The thermal storage concept was experimentally studied using a lab scale apparatus that enabled investigating of storage materials (the PCM-HTF system) simultaneously with carrying out thermal performance measurements and observing heat transfer effects occurring in the system. The tests produced satisfactory results in terms of thermal stability and compatibility of the utilized storage materials, alloy Zn70Sn30 and the eutectic mixture of biphenyl and diphenyl oxide, up to a working temperature of 400 deg. C. Optional schemes for integrating the developed thermal storage into a solar thermal electric plant are discussed and evaluated considering a pilot scale solar plant with thermal power output of 12 MW. The storage should enable uninterrupted operation of solar thermal electric systems during additional hours

The experimental facility for investigation of MHD heat transfer in perspective coolants in nuclear energetics.

Science.gov (United States)

Batenin, B. M.; Belyaev, I. A.; Birukov, D. A.; Frick, P. G.; Nikitina, I. S.; Manchkha, S. P.; Pyatnitskaya, N. Yu; Razuvanov, N. G.; Sviridov, E. V.; Sviridov, V. G.

2017-11-01

Paper presents the current results of work conducted by a joint research group of MPEI-JIHT RAS for experimental study of liquid metals heat transfer. The team of specialists of MPEI-JIHT RAS put into operation a new mercury MHD facility RK-3. The main components of this stand are: a unique electromagnet, created by specialists of the Budker Institute of Nuclear Physics (BINP), and a sealed liquid-metal circuit. The facility will be explored lifting and standpipe flow of liquid metal in a transverse magnetic field in channels of different forms. For the experiments on the study of heat transfer and hydrodynamics of flows for measuring characteristics such as temperature, speed, pulse characteristics, probe method is used. Presents the first experimental results obtained for a pipe in a transverse magnetic field. During the experiments with various flow parameters data was obtained and processed with constructing temperature fields, dimensionless wall temperature distributions and heat transfer coefficients along the perimeter of the work area. Modes with low frequency pulsations of temperature were discovered. The boundaries where low frequency temperature fluctuations occur were defined in a circular tube.

Calculation codes for radiant heat transfers; Les codes de calcul de rayonnement thermique

Energy Technology Data Exchange (ETDEWEB)

NONE

1997-12-31

This document reports on 12 papers about computerized simulation and modeling of radiant heat transfers and fluid flows in various industrial and domestic situations: space heating, metal industry (furnaces, boilers..), aerospace industry (turbojet engines, combustion chambers) etc.. This workshop was organized by the ``radiation`` section of the French society of thermal engineers. (J.S.)

Calculation codes for radiant heat transfers; Les codes de calcul de rayonnement thermique

Energy Technology Data Exchange (ETDEWEB)

NONE

1996-12-31

This document reports on 12 papers about computerized simulation and modeling of radiant heat transfers and fluid flows in various industrial and domestic situations: space heating, metal industry (furnaces, boilers..), aerospace industry (turbojet engines, combustion chambers) etc.. This workshop was organized by the ``radiation`` section of the French society of thermal engineers. (J.S.)

Impact of External Pressure on the Heat Transfer Coefficient during Solidification of Al-A356 Alloy

DEFF Research Database (Denmark)

Jabbari, Masoud; Ilkhchy, A.Fardi; Moumani, E.

In this paper the interfacial heat transfer coefficient (IHTC) is correlated to applied external pressure, in which IHTC at the interface between A356 aluminum alloy and metallic mold during the solidification of the casting under different pressures were obtained using the Inverse Heat Conduction...... Problem (IHCP) method. The method covers the expedient of comparing theoretical and experimental thermal histories. Temperature profiles obtained from thermocouples were used in a finite difference heat flow program to estimate the transient heat transfer coefficients. The new simple formula was presented...

Heat transfer correlations in mantle tanks

DEFF Research Database (Denmark)

Furbo, Simon; Knudsen, Søren

2005-01-01

on calculations with a CFD-model, which has earlier been validated by means of experiments. The CFD-model is used to determine the heat transfer between the solar collector fluid in the mantle and the walls surrounding the mantle in all levels of the mantle as well as the heat transfer between the wall...... transfer correlations are suitable as input for a detailed simulation model for mantle tanks. The heat transfer correlations determined in this study are somewhat different from previous reported heat transfer correlations. The reason is that this study includes more mantle tank designs and operation......Small solar domestic hot water systems are best designed as low flow systems based on vertical mantle tanks. Theoretical investigations of the heat transfer in differently designed vertical mantle tanks during different operation conditions have been carried out. The investigations are based...

Thermal Stress and Heat Transfer Coefficient for Ceramics Stalk Having Protuberance Dipping into Molten Metal

Science.gov (United States)

Noda, Nao-Aki; Hendra; Li, Wenbin; Takase, Yasushi; Ogura, Hiroki; Higashi, Yusuke

Low pressure die casting is defined as a net shape casting technology in which the molten metal is injected at high speeds and pressure into a metallic die. The low pressure die casting process plays an increasingly important role in the foundry industry as a low-cost and high-efficiency precision forming technique. In the low pressure die casting process is that the permanent die and filling systems are placed over the furnace containing the molten alloy. The filling of the cavity is obtained by forcing the molten metal, by means of a pressurized gas, to rise into a ceramic tube having protuberance, which connects the die to the furnace. The ceramics tube, called stalk, has high temperature resistance and high corrosion resistance. However, attention should be paid to the thermal stress when the stalk having protuberance is dipped into the molten aluminum. It is important to reduce the risk of fracture that may happen due to the thermal stresses. In this paper, thermo-fluid analysis is performed to calculate surface heat transfer coefficient. The finite element method is applied to calculate the thermal stresses when the stalk having protuberance is dipped into the crucible with varying dipping speeds. It is found that the stalk with or without protuberance should be dipped into the crucible slowly to reduce the thermal stress.

Heat transfer II essentials

CERN Document Server

REA, The Editors of

1988-01-01

REA's Essentials provide quick and easy access to critical information in a variety of different fields, ranging from the most basic to the most advanced. As its name implies, these concise, comprehensive study guides summarize the essentials of the field covered. Essentials are helpful when preparing for exams, doing homework and will remain a lasting reference source for students, teachers, and professionals. Heat Transfer II reviews correlations for forced convection, free convection, heat exchangers, radiation heat transfer, and boiling and condensation.

Transfer of heat to fluidized-solids beds

Energy Technology Data Exchange (ETDEWEB)

1952-10-16

The improvement in the method described and claimed in patent application 14,363/47 (136,186) for supplying heat to a dense turbulent mass of solid fluidized by a gas flowing upwardly therethrough and subjected to a high temperature in a treating zone, by heat transfer through heat-transfer surfaces of heat-transfer elements in contact with the said turbulent mass of finely divided solid and heated by means of a fluid heating medium, including burning fuels comprising contacting the said heat-transfer surfaces with a fuel and a combustion supporting gas under such conditions that the combustion of the fuel is localized in the heat-transfer element near the point of entry of the fuel and combustion-supporting gas and a substantial temperature gradient is maintained along the path of said fuel combustion-supporting gas and combustion products through the said heat-transfer element.

Tunable heat transfer with smart nanofluids.

Science.gov (United States)

Bernardin, Michele; Comitani, Federico; Vailati, Alberto

2012-06-01

Strongly thermophilic nanofluids are able to transfer either small or large quantities of heat when subjected to a stable temperature difference. We investigate the bistability diagram of the heat transferred by this class of nanofluids. We show that bistability can be exploited to obtain a controlled switching between a conductive and a convective regime of heat transfer, so as to achieve a controlled modulation of the heat flux.

An assessment of RELAP5 MOD3.1.1 condensation heat transfer modeling with GIRAFFE heat transfer tests

International Nuclear Information System (INIS)

Boyer, B.D.; Parlatan, Y.; Slovik, G.C.; Rohatgi, U.S.

1995-01-01

RELAP5 MOD3.1.1 is being used to simulate Loss of Coolant Accidents (LOCA) for the Simplified Boiling Water Reactor (SBWR) being proposed by General Electric (GE). One of the major components associated with the SBWR is the Passive Containment Cooling System (PCCS) which provides the long-term heat sink to reject decay heat. The RELAP5 MOD3.1.1 code is being assessed for its ability to represent accurately the PCCS. Data from the Phase 1, Step 1 Heat Transfer Tests performed at Toshiba's Gravity-Driven Integral Full-Height Test for Passive Heat Removal (GIRAFFE) facility will be used for assessing the ability of RELAP5 to model condensation in the presence of noncondensables. The RELAP5 MOD3.1.1 condensation model uses the University of California at Berkeley (UCB) correlation developed by Vierow and Schrock. The RELAP5 code uses this heat transfer coefficient with the gas velocity effect multiplier being limited to 2. This heat transfer option was used to analyze the condensation heat transfer in the GIRAFFE PCCS heat exchanger tubes in the Phase 1, Step 1 Heat Transfer Tests which were at a pressure of 3 bar and had a range of nitrogen partial pressure fractions from 0.0 to 0.10. The results of a set of RELAP5 calculations al these conditions were compared with the GIRAFFE data. The effects of PCCS cell nodings on the heat transfer process were also studied. The UCB correlation, as implemented in RELAP5, predicted the heat transfer to ±5% of the data with a three-node model. The three-node model has a large cell in the entrance region which smeared out the entrance effects on the heat transfer, which tend to overpredict the condensation. Hence, the UCB correlation predicts condensation heat transfer in the presence of noncondensable gases with only a coarse mesh. The cell length term in the condensation heat transfer correlation implemented in the code must be removed to allow for accurate calculations with smaller cell sizes

Postaccident heat removal. II. Heat transfer from an internally heated liquid to a melting solid

International Nuclear Information System (INIS)

Faw, R.E.; Baker, L. Jr.

1976-01-01

Microwave heating has been used in studies of heat transfer from a horizontal layer of internally heated liquid to a melting solid. Experiments were designed to simulate heat transfer and meltthrough processes of importance in the analysis of postaccident heat removal capabilities of nuclear reactors. Glycerin, heated by 2.45-GHz microwave radiation, was used to simulate molten fuel. Paraffin wax was used to simulate a melting barrier confining the fuel. Experimentally measured heat fluxes and melting rates were consistent with a model based on downward heat transfer by conduction through a stagnant liquid layer and upward heat transfer augmented by natural convection. Melting and displacement of the barrier material occurred by upward-moving droplets randomly distributed across the melting surface. Results indicated that the melting and displacement process had no effect on the heat transfer process

Axial flow heat exchanger devices and methods for heat transfer using axial flow devices

Science.gov (United States)

Koplow, Jeffrey P.

2016-02-16

Systems and methods described herein are directed to rotary heat exchangers configured to transfer heat to a heat transfer medium flowing in substantially axial direction within the heat exchangers. Exemplary heat exchangers include a heat conducting structure which is configured to be in thermal contact with a thermal load or a thermal sink, and a heat transfer structure rotatably coupled to the heat conducting structure to form a gap region between the heat conducting structure and the heat transfer structure, the heat transfer structure being configured to rotate during operation of the device. In example devices heat may be transferred across the gap region from a heated axial flow of the heat transfer medium to a cool stationary heat conducting structure, or from a heated stationary conducting structure to a cool axial flow of the heat transfer medium.

Boiling heat transfer on horizontal tube bundles

International Nuclear Information System (INIS)

Anon.

1987-01-01

Nucleate boiling heat transfer characteristics for a tube in a bundle differ from that for a single tube in a pool and this difference is known as 'tube bundle effect.' There exist two bundle effects, positive and negative. The positive bundle effect enhances heat transfer due to convective flow induced by rising bubbles generated from the lower tubes, while the negative bundle effect deteriorates heat transfer due to vapor blanketing caused by accumulation of bubbles. Staggered tube bundles tested and found that the upper tubes in bundles have higher heat transfer coefficients than the lower tubes. The effects of various parameters such as pressure, tube geometry and oil contamination on heat transfer have been examined. Some workers attempted to clarify the mechanism of occurrence of 'bundle effect' by testing tube arrangements of small scale. All reported only enhancement in heat transfer but results showed the symptom of heat transfer deterioration at higher heat fluxes. As mentioned above, it has not been clarified so far even whether the 'tube bundle effect' should serve as enhancement or deterioration of heat transfer in nucleate boiling. In this study, experiments are performed in detail by using bundles of small scale, and effects of heat flux distribution, pressure and tube location are clarified. Furthermore, some consideration on the mechanisms of occurrence of 'tube bundle effect' is made and a method for prediction of heat transfer rate is proposed

Heat transfer and fire spread

Science.gov (United States)

Hal E. Anderson

1969-01-01

Experimental testing of a mathematical model showed that radiant heat transfer accounted for no more than 40% of total heat flux required to maintain rate of spread. A reasonable prediction of spread was possible by assuming a horizontal convective heat transfer coefficient when certain fuel and flame characteristics were known. Fuel particle size had a linear relation...

Condensation heat transfer in plate heat exchangers

International Nuclear Information System (INIS)

Panchal, C.B.

1985-01-01

An Alfa-Laval plate heat exchanger, previously tested as an evaporator, was retested as a condenser. Two series of tests with different chevron-angle plates were carried out using ammonia as a working fluid. The overall heat-transfer coefficient and pressure drop were measured, and the effects of operating parameters were determined. The experimental data were compared with theoretical predictions. In the analysis, a gravity-controlled condensation process was modeled theoretically, and the overall performance was calculated. The analysis shows that the overall heat-transfer coefficient can be predicted with an average uncertainty of about 10%. It is, however, important to consider the interfacial shear stress, because the effective friction factor is high for flow in plate heat exchangers

Component Cooling Heat Exchanger Heat Transfer Capability Operability Monitoring

International Nuclear Information System (INIS)

Mihalina, M.; Djetelic, N.

2010-01-01

The ultimate heat sink (UHS) is of highest importance for nuclear power plant safe and reliable operation. The most important component in line from safety-related heat sources to the ultimate heat sink water body is a component cooling heat exchanger (CC Heat Exchanger). The Component Cooling Heat Exchanger has a safety-related function to transfer the heat from the Component Cooling (CC) water system to the Service Water (SW) system. SW systems throughout the world have been the root of many plant problems because the water source, usually river, lake, sea or cooling pond, are conductive to corrosion, erosion, biofouling, debris intrusion, silt, sediment deposits, etc. At Krsko NPP, these problems usually cumulate in the summer period from July to August, with higher Sava River (service water system) temperatures. Therefore it was necessary to continuously evaluate the CC Heat Exchanger operation and confirm that the system would perform its intended function in accordance with the plant's design basis, given as a minimum heat transfer rate in the heat exchanger design specification sheet. The Essential Service Water system at Krsko NPP is an open cycle cooling system which transfers heat from safety and non-safety-related systems and components to the ultimate heat sink the Sava River. The system is continuously in operation in all modes of plant operation, including plant shutdown and refueling. However, due to the Sava River impurities and our limited abilities of the water treatment, the system is subject to fouling, sedimentation buildup, corrosion and scale formation, which could negatively impact its performance being unable to satisfy its safety related post accident heat removal function. Low temperature difference and high fluid flows make it difficult to evaluate the CC Heat Exchanger due to its specific design. The important effects noted are measurement uncertainties, nonspecific construction, high heat transfer capacity, and operational specifics (e

Computer aided heat transfer analysis in a laboratory scaled heat exchanger unit

International Nuclear Information System (INIS)

Gunes, M.

1998-01-01

In this study. an explanation of a laboratory scaled heat exchanger unit and a software which is developed to analyze heat transfer. especially to use it in heat transfer courses, are represented. Analyses carried out in the software through sample values measured in the heat exchanger are: (l) Determination of heat transfer rate, logarithmic mean temperature difference and overall heat transfer coefficient; (2)Determination of convection heat transfer coefficient inside and outside the tube and the effect of fluid velocity on these; (3)Investigation of the relationship between Nusselt Number. Reynolds Number and Prandtl Number by using multiple non-linear regression analysis. Results are displayed on the screen graphically

Heat transfer coefficient as parameter describing ability of insulating liquid to heat transfer

Science.gov (United States)

Nadolny, Zbigniew; Gościński, Przemysław; Bródka, Bolesław

2017-10-01

The paper presents the results of the measurements of heat transfer coefficient of insulating liquids used in transformers. The coefficient describes an ability of the liquid to heat transport. On the basis of the coefficient, effectiveness of cooling system of electric power devices can be estimated. Following liquids were used for the measurements: mineral oil, synthetic ester and natural ester. It was assumed that surface heat load is about 2500 W·m-2, which is equal the load of transformer windings. A height of heat element was 1.6 m, because it makes possible steady distribution of temperature on its surface. The measurements of heat transfer coefficient was made as a function of various position of heat element (vertical, horizontal). In frame of horizontal position of heat element, three suppositions were analysed: top, bottom, and side.

Heat transfer coefficient as parameter describing ability of insulating liquid to heat transfer

Directory of Open Access Journals (Sweden)

Nadolny Zbigniew

2017-01-01

Full Text Available The paper presents the results of the measurements of heat transfer coefficient of insulating liquids used in transformers. The coefficient describes an ability of the liquid to heat transport. On the basis of the coefficient, effectiveness of cooling system of electric power devices can be estimated. Following liquids were used for the measurements: mineral oil, synthetic ester and natural ester. It was assumed that surface heat load is about 2500 W·m-2, which is equal the load of transformer windings. A height of heat element was 1.6 m, because it makes possible steady distribution of temperature on its surface. The measurements of heat transfer coefficient was made as a function of various position of heat element (vertical, horizontal. In frame of horizontal position of heat element, three suppositions were analysed: top, bottom, and side.

Heat transfer pipe shielding device for heat exchanger

International Nuclear Information System (INIS)

Hanawa, Jun.

1991-01-01

The front face and the rear face of a frame that surrounds the circumference of the water chamber body of a multi-tube heat exchanger are covered by a rotational shielding plate. A slit is radially formed to the shielding plate for the insertion of a probe or cleaner to the heat transfer pipe and a deflector is disposed on the side opposite to the slit. The end of the heat transfer pipe to be inspected is exposed to the outer side by way of the slit by the rotation of the shielding plate, and the probe or cleaner is inserted in the heat transfer pipe to conduct an eddy current injury monitoring test or cleaning. The inside of the water chamber and the heat transfer pipe is exhausted by a ventilation nozzle disposed to the frame. Accordingly, a shielding effect upon inspection and cleaning can be obtained and, in addition, inspection and exhaustion at the cleaning position can be conducted easily. Since the operation for attachment and detachment is easy, the effect of reducing radiation dose per unit can be obtained by the shortening of the operation time. (N.H.)

Heat transfer in two-phase flow of helium

International Nuclear Information System (INIS)

Subbotin, V.I.; Deev, V.I.; Solodovnikov, V.V.; Arkhipov, V.V.

1986-01-01

The results of experimental study of heat transfer in two-phase helium flow are presented. The effect of operating parameters (pressure, mass velocity, heat flux and quality) on boiling heat transfer intensity was investigated. A significant influence of boiling process prehistory on heat transfer coefficients was demonstrated. On the basis of experimental data obtained three typical regimes of flow boiling heat transfer were found. Analogy of heat transfer in flow boiling and pool boiling of helium and noncryogenic liquids was established. Correlations were developed which are in close agreement with available heat transfer data

Heat transfer from internally-heated molten UO2 pools

International Nuclear Information System (INIS)

Stein, R.P.; Baker, L. Jr.; Gunther, W.H.; Cook, C.

1978-01-01

Experimental measurements of heat transfer from internally heated pools of molten UO 2 have been obtained for two cell sizes: 10 cm x 10 cm and 20 cm x 20 cm. The experiments with the large cell have supported a previous conclusion from early small data that the measured downward heat fluxes are higher than would be expected on the basis of considerations of thermal convection. A convective model underpredicts the downward heat fluxes by a factor of 2.5 to 4.5 for all but one early experiment. Arbitrary assumptions of increased thermal conductivity do not account for the discrepancy. A single model based on internal thermal radiation heat transfer is able to account for the high values. The model uses the optically thick Rosseland approximation. Because of this, it is tentatively concluded that thermal radiation plays a dominant role in controlling the heat transfer from internally heated molted fuel

Theory of Periodic Conjugate Heat Transfer

CERN Document Server

Zudin, Yuri B

2012-01-01

This book presents the theory of periodic conjugate heat transfer in a detailed way. The effects of thermophysical properties and geometry of a solid body on the commonly used and experimentally determined heat transfer coefficient are analytically presented from a general point of view. The main objective of the book is a simplified description of the interaction between a solid body and a fluid as a boundary value problem of the heat conduction equation for the solid body. At the body surface, the true heat transfer coefficient is composed of two parts: the true mean value resulting from the solution of the steady state heat transfer problem and a periodically variable part, the periodic time and length to describe the oscillatory hydrodynamic effects. The second edition is extended by (i) the analysis of stability boundaries in helium flow at supercritical conditions in a heated channel with respect to the interaction between a solid body and a fluid; (ii) a periodic model and a method of heat transfer sim...

Modeling of heat transfer into a heat pipe for a localized heat input zone

International Nuclear Information System (INIS)

Rosenfeld, J.H.

1987-01-01

A general model is presented for heat transfer into a heat pipe using a localized heat input. Conduction in the wall of the heat pipe and boiling in the interior structure are treated simultaneously. The model is derived from circumferential heat transfer in a cylindrical heat pipe evaporator and for radial heat transfer in a circular disk with boiling from the interior surface. A comparison is made with data for a localized heat input zone. Agreement between the theory and the model is good. This model can be used for design purposes if a boiling correlation is available. The model can be extended to provide improved predictions of heat pipe performance

Heat exchanger device and method for heat removal or transfer

Science.gov (United States)

Koplow, Jeffrey P

2013-12-10

Systems and methods for a forced-convection heat exchanger are provided. In one embodiment, heat is transferred to or from a thermal load in thermal contact with a heat conducting structure, across a narrow air gap, to a rotating heat transfer structure immersed in a surrounding medium such as air.

Visualisation of heat transfer in laminar flows

NARCIS (Netherlands)

Speetjens, M.F.M.; Steenhoven, van A.A.

2009-01-01

Heat transfer in fluid flows traditionally is examined in terms of temperature field and heat-transfer coefficients at non-adiabatic walls. However, heat transfer may alternatively be considered as the transport of thermal energy by the total convective-conductive heat flux in a way analogous to the

A heat transfer textbook

CERN Document Server

Lienhard, John H

2011-01-01

This introduction to heat transfer offers advanced undergraduate and graduate engineering students a solid foundation in the subjects of conduction, convection, radiation, and phase-change, in addition to the related topic of mass transfer. A staple of engineering courses around the world for more than three decades, it has been revised and updated regularly by the authors, a pair of recognized experts in the field. The text addresses the implications, limitations, and meanings of many aspects of heat transfer, connecting the subject to its real-world applications and developing students' ins

Laser Pulse Heating of Spherical Metal Particles

Directory of Open Access Journals (Sweden)

Michael I. Tribelsky

2011-12-01

Full Text Available We consider the general problem of laser pulse heating of spherical metal particles with the sizes ranging from nanometers to millimeters. We employ the exact Mie solution of the diffraction problem and solve the heat-transfer equation to determine the maximum temperature rise at the particle surface as a function of optical and thermometric parameters of the problem. Primary attention is paid to the case when the thermal diffusivity of the particle is much larger than that of the environment, as it is in the case of metal particles in fluids. We show that, in this case, for any given duration of the laser pulse, the maximum temperature rise as a function of the particle size reaches a maximum at a certain finite size of the particle. We suggest simple approximate analytical expressions for this dependence, which cover the entire parameter range of the problem and agree well with direct numerical simulations.

Elementary heat transfer analysis

CERN Document Server

Whitaker, Stephen; Hartnett, James P

1976-01-01

Elementary Heat Transfer Analysis provides information pertinent to the fundamental aspects of the nature of transient heat conduction. This book presents a thorough understanding of the thermal energy equation and its application to boundary layer flows and confined and unconfined turbulent flows. Organized into nine chapters, this book begins with an overview of the use of heat transfer coefficients in formulating the flux condition at phase interface. This text then explains the specification as well as application of flux boundary conditions. Other chapters consider a derivation of the tra

Heat and mass transfer

CERN Document Server

Karwa, Rajendra

2017-01-01

This textbook presents the classical treatment of the problems of heat transfer in an exhaustive manner with due emphasis on understanding of the physics of the problems. This emphasis is especially visible in the chapters on convective heat transfer. Emphasis is laid on the solution of steady and unsteady two-dimensional heat conduction problems. Another special feature of the book is a chapter on introduction to design of heat exchangers and their illustrative design problems. A simple and understandable treatment of gaseous radiation has been presented. A special chapter on flat plate solar air heater has been incorporated that covers thermo-hydraulic modeling and simulation. The chapter on mass transfer has been written looking specifically at the needs of the students of mechanical engineering. The book includes a large number and variety of solved problems with supporting line diagrams. The author has avoided duplicating similar problems, while incorporating more application-based examples. All the end-...

Heat Transfer Basics and Practice

CERN Document Server

Böckh, Peter

2012-01-01

The book provides an easy way to understand the fundamentals of heat transfer. The reader will acquire the ability to design and analyze heat exchangers. Without extensive derivation of the fundamentals, the latest correlations for heat transfer coefficients and their application are discussed. The following topics are presented - Steady state and transient heat conduction - Free and forced convection - Finned surfaces - Condensation and boiling - Radiation - Heat exchanger design - Problem-solving After introducing the basic terminology, the reader is made familiar with the different mechanisms of heat transfer. Their practical application is demonstrated in examples, which are available in the Internet as MathCad files for further use. Tables of material properties and formulas for their use in programs are included in the appendix. This book will serve as a valuable resource for both students and engineers in the industry. The author’s experience indicates that students, after 40 lectures and exercises ...

An evaluation of analytical heat transfer area with various boiling heat transfer correlations in steam generator thermal sizing

International Nuclear Information System (INIS)

Jung, B. R.; Park, H. S.; Chung, D. M.; Baik, S. J.

1999-01-01

The computer program SAFE has been used to size and analyze the performance of a steam generator which has two types of heat transfer regions in Korean Standard Nuclear Power Plants (KSNP) and Korean Next Generation Reactor (KNGR) design. The SAFE code calculates the analytical boiling heat transfer area using the modified form of the saturated nucleate pool boiling correlation suggested by Rohsenow. The predicted heat transfer area in the boiling region is multiplied by a constant to obtain a final analytical heat transfer area. The inclusion of the multiplier in the analytical calculation has some disadvantage of loss of complete correlation by the governing heat transfer equation. Several comparative analyses have been performed quantitatively to evaluate the possibility of removing the multiplier in the analytical calculation in the SAFE code. The evaluation shows that the boiling correlation and multiplier used in predicting the boiling region heat transfer area can be replaced with other correlations predicting nearly the same heat transfer area. The removal of multiplier included in the analytical calculation will facilitate a direct use of a set of concerned analytical sizing values that can be exactly correlated by the governing heat transfer equation. In addition this will provide more reasonable basis for the steam generator thermal sizing calculation and enhance the code usability without loss of any validity of the current sizing procedure. (author)

Characterizing convective heat transfer using infrared thermography and the heated-thin-foil technique

International Nuclear Information System (INIS)

Stafford, Jason; Walsh, Ed; Egan, Vanessa

2009-01-01

Convective heat transfer, due to axial flow fans impinging air onto a heated flat plate, is investigated with infrared thermography to assess the heated-thin-foil technique commonly used to quantify two-dimensional heat transfer performance. Flow conditions generating complex thermal profiles have been considered in the analysis to account for dominant sources of error in the technique. Uncertainties were obtained in the measured variables and the influences on the resultant heat transfer data are outlined. Correction methods to accurately account for secondary heat transfer mechanisms were developed and results show that as convective heat transfer coefficients and length scales decrease, the importance of accounting for errors increases. Combined with flow patterns that produce large temperature gradients, the influence of heat flow within the foil on the resultant heat transfer becomes significant. Substantial errors in the heat transfer coefficient are apparent by neglecting corrections to the measured data for the cases examined. Methods to account for these errors are presented here, and demonstrated to result in an accurate measurement of the local heat transfer map on the surface

An assessment of RELAP5 MOD3.1.1 condensation heat transfer modeling with GIRAFFE heat transfer tests

International Nuclear Information System (INIS)

Boyer, B.D.; Parlatan, Y.; Slovik, G.C.

1995-01-01

RELAP5 MOD3.1.1 is being used to simulate Loss of Coolant Accidents (LOCA) for the Simplified Boiling Water Reactor (SBWR) being proposed by General Electric (GE). One of the major components associated with the SBWR is the Passive Containment Cooling System (PCCS) which provides the long-term heat sink to reject decay heat. The RELAP5 MOD3.1.1 code is being assessed for its ability to represent accurately the PCCS. Data from the Phase 1, Step 1 Heat Transfer Tests performed at Toshiba's Gravity-Driven Integral Full-Height Test for Passive Heat Removal (GIRAFFE) facility will be used for assessing the ability of RELAP5 to model condensation in the presence of noncondensables. The RELAP5 MOD3.1.1 condensation model uses the University of California at Berkeley (UCB) correlation developed by Vierow and Schrock. The RELAP5 code uses this heat transfer coefficient with the gas velocity effect multiplier being limited to 2. This heat transfer option was used to analyze the condensation heat transfer in the GIRAFFE PCCS heat exchanger tubes in the Phase 1, Step 1 Heat Transfer Tests which were at a pressure of 3 bar and had a range of nitrogen partial pressure fractions from 0.0 to 0.10. The results of a set of RELAP5 calculations at these conditions were compared with the GIRAFFE data. The effects of PCCS cell noding on the heat transfer process were also studied. The UCB correlation, as implemented in RELAP5, predicted the heat transfer to ±5% of the data with a three--node model. The three-node model has a large cell in the entrance region which smeared out the entrance effects on the heat transfer, which tend to overpredict the condensation. Hence, the UCB correlation predicts condensation heat transfer correlation implemented in the code must be removed to allow for accurate calculations with smaller cell sizes

An assessment of RELAP5 MOD3.1.1 condensation heat transfer modeling with GIRAFFE heat transfer tests

Energy Technology Data Exchange (ETDEWEB)

Boyer, B.D.; Parlatan, Y.; Slovik, G.C. [and others

1995-09-01

RELAP5 MOD3.1.1 is being used to simulate Loss of Coolant Accidents (LOCA) for the Simplified Boiling Water Reactor (SBWR) being proposed by General Electric (GE). One of the major components associated with the SBWR is the Passive Containment Cooling System (PCCS) which provides the long-term heat sink to reject decay heat. The RELAP5 MOD3.1.1 code is being assessed for its ability to represent accurately the PCCS. Data from the Phase 1, Step 1 Heat Transfer Tests performed at Toshiba`s Gravity-Driven Integral Full-Height Test for Passive Heat Removal (GIRAFFE) facility will be used for assessing the ability of RELAP5 to model condensation in the presence of noncondensables. The RELAP5 MOD3.1.1 condensation model uses the University of California at Berkeley (UCB) correlation developed by Vierow and Schrock. The RELAP5 code uses this heat transfer coefficient with the gas velocity effect multiplier being limited to 2. This heat transfer option was used to analyze the condensation heat transfer in the GIRAFFE PCCS heat exchanger tubes in the Phase 1, Step 1 Heat Transfer Tests which were at a pressure of 3 bar and had a range of nitrogen partial pressure fractions from 0.0 to 0.10. The results of a set of RELAP5 calculations at these conditions were compared with the GIRAFFE data. The effects of PCCS cell noding on the heat transfer process were also studied. The UCB correlation, as implemented in RELAP5, predicted the heat transfer to {plus_minus}5% of the data with a three--node model. The three-node model has a large cell in the entrance region which smeared out the entrance effects on the heat transfer, which tend to overpredict the condensation. Hence, the UCB correlation predicts condensation heat transfer correlation implemented in the code must be removed to allow for accurate calculations with smaller cell sizes.

Heat transfer characteristics of a helical heat exchanger

International Nuclear Information System (INIS)

San, Jung-Yang; Hsu, Chih-Hsiang; Chen, Shih-Hao

2012-01-01

Heat transfer performance of a helical heat exchanger was investigated. The heat exchanger is composed of a helical tube with rectangular cross section and two cover plates. The ε–Ntu relation of the heat exchanger was obtained using a numerical method. In the analysis, the flow in the tube (helical flow) was considered to be mixed and the flow outside the tube (radial flow) was unmixed. In the experiment, the Darcy friction factor (f) and convective heat transfer coefficient (h) of the radial flow were measured. The radial flow was air and the helical flow was water. Four different channel spacing (0.5, 0.8, 1.2 and 1.6 mm) were individually considered. The Reynolds numbers were in the range 307–2547. Two correlations, one for the Darcy friction factor and the other for the Nusselt number, were proposed. - Highlights: ► We analyze the heat transfer characteristics of a helical heat exchanger and examine the effectiveness–Ntu relation. ► Increasing number of turns of the heat exchanger would slightly increase the effectiveness. ► There is an optimum Ntu value corresponding to a maximum effectiveness. ► We measure the Darcy friction factor and Nusselt number of the radial flow and examine the correlations.

Single phase flow pressure drop and heat transfer in rectangular metallic microchannels

International Nuclear Information System (INIS)

Sahar, Amirah M.; Özdemir, Mehmed R.; Fayyadh, Ekhlas M.; Wissink, Jan; Mahmoud, Mohamed M.; Karayiannis, Tassos G.

2016-01-01

Numerical simulations were performed using Fluent 14.5 to investigate single phase flow and conjugate heat transfer in copper rectangular microchannels. Two different configurations were simulated: (1) single channel with hydraulic diameter of 0.561 mm and (2) multichannel configuration consisting of inlet and outlet manifolds and 25 channels with hydraulic diameter of 0.409 mm. In the single channel configuration, four numerical models were investigated namely, 2D thin-wall, 3D thin-wall (heated from the bottom), 3D thin-wall (three side heated) and 3D full conjugate models. In the multichannel configuration, only 3D full conjugate model was used. The simulation results of the single channel configuration were validated using experimental data of water as a test fluid while the results of the multichannel configuration were validated using experimental data of R134a refrigerant. In the multichannel configuration, flow distribution among the channels was also investigated. The 3D thin-wall model simulation was conducted at thermal boundary conditions similar to those assumed in the experimental data reduction (uniform heat flux) and showed excellent agreement with the experimental data. However, the results of the 3D full conjugate model demonstrated that there is a significant conjugate effect and the heat flux is not uniformly distributed along the channel resulting in significant deviation compared to the experimental data (more than 50%). Also, the results demonstrated that there is a significant difference between the 3D thin-wall and full conjugate models. The simulation of the multichannel configuration with an inlet manifold having gradual decrease in cross sectional area achieved very reasonable uniform flow distribution among the channels which will provide uniform heat transfer rates across the base of the microchannels.

Heat Transfer in a Thermoacoustic Process

Science.gov (United States)

Beke, Tamas

2012-01-01

Thermoacoustic instability is defined as the excitation of acoustic modes in chambers with heat sources due to the coupling between acoustic perturbations and unsteady heat addition. The major objective of this paper is to achieve accurate theoretical results in a thermoacoustic heat transfer process. We carry out a detailed heat transfer analysis…

Natural Convection Heat Transfer of Oxide Pool During In-Vessel Retention of Core Melts

Energy Technology Data Exchange (ETDEWEB)

Park, Hae-Kyun; Chung, Bum-Jin [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2015-10-15

The integrity of reactor vessel may be threatened by the heat generation at the oxide pool and to the natural convection heat transfer to the reactor vessel by those two layers. Therefore, External Reactor Vessel Cooling (ERVC) is performed in order to secure the integrity of the reactor vessel. Whether the IVR(In-Vessel Retention) Strategy can be applicable to a larger reactor is the technical concern, which nourished the research interest for the natural convection heat transfer of metal and oxide pool and ERVC performance. Especially, it is hard to simulate oxide pool by experimentally due to the high level of buoyancy. Moreover, the volumetrically exothermic working fluid should be adopted to simulate the behavior of the core melts. Therefore, the volumetric heat sources that immersed in the working fluid have been adopted to simulate oxide pool by experiment. We investigated oxide pool with two different designs of the volumetric heat sources that adopted previous experiments. The investigation was performed by mass transfer experiment using analogy between heat and mass transfers. The results were compared to previous studies. We simulated the natural convection heat transfer of the oxide pool by mass transfer experiment. The isothermally cooled condition was established by limiting current technique firstly. The results were compared to previous studies under identical design of the volumetric heat sources. The average Nu's of the curvature and the top plate were close to the previous studies.

"Nanotechnology Enabled Advanced Industrial Heat Transfer Fluids"

Energy Technology Data Exchange (ETDEWEB)

Dr. Ganesh Skandan; Dr. Amit Singhal; Mr. Kenneth Eberts; Mr. Damian Sobrevilla; Prof. Jerry Shan; Stephen Tse; Toby Rossmann

2008-06-12

ABSTRACT Nanotechnology Enabled Advanced industrial Heat Transfer Fluids” Improving the efficiency of Industrial Heat Exchangers offers a great opportunity to improve overall process efficiencies in diverse industries such as pharmaceutical, materials manufacturing and food processing. The higher efficiencies can come in part from improved heat transfer during both cooling and heating of the material being processed. Additionally, there is great interest in enhancing the performance and reducing the weight of heat exchangers used in automotives in order to increase fuel efficiency. The goal of the Phase I program was to develop nanoparticle containing heat transfer fluids (e.g., antifreeze, water, silicone and hydrocarbon-based oils) that are used in transportation and in the chemical industry for heating, cooling and recovering waste heat. Much work has been done to date at investigating the potential use of nanoparticle-enhanced thermal fluids to improve heat transfer in heat exchangers. In most cases the effect in a commercial heat transfer fluid has been marginal at best. In the Phase I work, we demonstrated that the thermal conductivity, and hence heat transfer, of a fluid containing nanoparticles can be dramatically increased when subjected to an external influence. The increase in thermal conductivity was significantly larger than what is predicted by commonly used thermal models for two-phase materials. Additionally, the surface of the nanoparticles was engineered so as to have a minimal influence on the viscosity of the fluid. As a result, a nanoparticle-laden fluid was successfully developed that can lead to enhanced heat transfer in both industrial and automotive heat exchangers

Visualization of direct contact heat transfer between water and molten alloy by neutron radiography. 1

International Nuclear Information System (INIS)

Nishi, Yoshihisa; Furuya, Masahiro; Kinoshita, Izumi; Takenaka, Nobuyuki; Matsubayashi, Masahito.

1997-01-01

Design of an innovative Steam Generator (SG) for Liquid Metal Fast Reactors (LMFRs) using liquid-liquid direct contact heat transfer has been developing. In this concept, the SG shell is filled with a molten alloy, which is heated by primary sodium. Water is fed into the high-temperature, molten alloy, and evaporates by direct contact heating. In order to obtain the fundamental information needed to discuss the heat transfer mechanisms of direct contact between the water and molten alloy, this phenomenon was observed by neutron radiography. JRR-3M thermal neutron radiography at the Japan Atomic Energy Research Institute was used. This paper deals with the results of visualization of direct contact heat exchange in the molten alloy. (author)

Heat transfer entropy resistance for the analyses of two-stream heat exchangers and two-stream heat exchanger networks

International Nuclear Information System (INIS)

Cheng, XueTao; Liang, XinGang

2013-01-01

The entropy generation minimization method is often used to analyze heat transfer processes from the thermodynamic viewpoint. In this paper, we analyze common heat transfer processes with the concept of entropy generation, and propose the concept of heat transfer entropy resistance. It is found that smaller heat transfer entropy resistance leads to smaller equivalent thermodynamic force difference with prescribed heat transfer rate and larger heat transfer rate with prescribed equivalent thermodynamic force difference. With the concept of heat transfer entropy resistance, the performance of two-stream heat exchangers (THEs) and two-stream heat exchanger networks (THENs) is analyzed. For the cases discussed in this paper, it is found that smaller heat transfer entropy resistance always leads to better heat transfer performance for THEs and THENs, while smaller values of the entropy generation, entropy generation numbers and revised entropy generation number do not always. -- Highlights: • The concept of entropy resistance is defined. • The minimum entropy resistance principle is developed. • Smaller entropy resistance leads to better heat transfer

Heat transfer coeffcient for boiling carbon dioxide

DEFF Research Database (Denmark)

Knudsen, Hans Jørgen Høgaard; Jensen, Per Henrik

1997-01-01

Heat transfer coefficient and pressure drop for boiling carbon dioxide (R744) flowing in a horizontal pipe has been measured. The pipe is heated by condensing R22 outside the pipe. The heat input is supplied by an electrical heater wich evaporates the R22. With the heat flux assumed constant over...... the whole surface and with measured temperature difference between the inner surface and the evaporation temperature a mean heat transfer coefficient is calculated. The calculated heat transfer coefficient has been compared with the Chart Correlation of Shah. The Chart Correlation predicts too low heat...... transfer coefficient but the ratio between the measured and the calculated heat transfer coefficient is nearly constant and equal 1.9. With this factor the correlation predicts the measured data within 14% (RMS). The pressure drop is of the same order as the measuring uncertainty and the pressure drop has...

Calculation and validation of heat transfer coefficient for warm forming operations

Science.gov (United States)

Omer, Kaab; Butcher, Clifford; Worswick, Michael

2017-10-01

In an effort to reduce the weight of their products, the automotive industry is exploring various hot forming and warm forming technologies. One critical aspect in these technologies is understanding and quantifying the heat transfer between the blank and the tooling. The purpose of the current study is twofold. First, an experimental procedure to obtain the heat transfer coefficient (HTC) as a function of pressure for the purposes of a metal forming simulation is devised. The experimental approach was used in conjunction with finite element models to obtain HTC values as a function of die pressure. The materials that were characterized were AA5182-O and AA7075-T6. Both the heating operation and warm forming deep draw were modelled using the LS-DYNA commercial finite element code. Temperature-time measurements were obtained from both applications. The results of the finite element model showed that the experimentally derived HTC values were able to predict the temperature-time history to within a 2% of the measured response. It is intended that the HTC values presented herein can be used in warm forming models in order to accurately capture the heat transfer characteristics of the operation.

Heat transfer and critical heat flux in a asymmetrically heated tube helicoidal flow

International Nuclear Information System (INIS)

Boscary, J.

1995-10-01

The design of plasma facing components is crucial for plasma performance in next fusion reactors. These elements will be submitted to very high heat flux. They will be actively water-cooled by swirl tubes in the subcooled boiling regime. High heat flux experiments were conducted in order to analyse the heat transfer and to evaluate the critical heat flux. Water-cooled mock-ups were one-side heated by an electron beam gun for different thermal-hydraulic conditions. The critical heat flux was detected by an original method based on the isotherm modification on the heated surface. The wall heat transfer law including forced convection and subcooled boiling regimes was established. Numerical calculations of the material heat transfer conduction allowed the non-homogeneous distribution of the wall temperature and of the wall heat flux to be evaluated. The critical heat flux value was defined as the wall maximum heat flux. A critical heat flux model based on the liquid sublayer dryout under a vapor blanket was established. A good agreement with test results was found. (author). 198 refs., 126 figs., 21 tabs

Supercritical heat transfer in an annular channel with external heating

International Nuclear Information System (INIS)

Remizov, O.V.; Gal'chenko, Eh.F.; Shurkin, N.G.; Sergeev, V.V.

1980-01-01

Results are presented of experimental studies of the burnout heat transfer in a 32x28x3000 mm annular channel with a uniform distribution of a heat flow at pressures of 6.9-19.6 MPa and mass rates of 350-1000 kg/m 2 xs. The heating is electrical, external, one-sided. It is shown that dependencies of the heat-transfer coefficient on rated parameters in the annular channel and tube are similar. An empirical equation has been obtained for the calculation of the burnout heat transfer in the annual channels with external heating in the following range: pressure, 6.9 -13.7 MPa; mass rate 350-700 kg/m 2 xs, and steam content ranging from Xsub(crit) to 1

Hydrodynamics and heat transfer in reactor components cooled by liquid metal coolants in single/two phase. 11. meeting of the International Association for Hydraulic Research (IAHR) Working Group. Working material

International Nuclear Information System (INIS)

2005-01-01

This Working Material includes the papers presented at the International Meeting 'Hydrodynamics and heat transfer in reactor components cooled by liquid metal coolants in single/two-phase', which was held 5-9 July 2004 at the State Scientific Center of Russian Federation - Institute for Physics and Power Engineering named after A.I. Leypunsky, in Obninsk near Moscow. The objectives of the meeting were to discuss new results obtained in the field of liquid metal coolant and to recommend the lines of further general physics and applied investigations, with the purpose of validating existing and codes under development for liquid metal cooled advanced and new generation nuclear reactors. Most of the contributions present results of experimental and numerical investigations into velocity, temperature and heat transfer in fuel subassemblies of fast reactors cooled by sodium or lead. In the frame of the meeting a benchmark problem devoted to heat transfer in the model subassembly of the fast reactor BREST-OD-300 was proposed. Experts from 5 countries (Japan, Netherlands, Spain, Republic of Korea, and Russia) took part in this benchmark exercise. The results of the benchmark calculations are summarized in the Working Material. The results of hydrodynamic studies of pressure head chambers and collector systems of liquid metal cooled reactors are presented in a number of papers. Also attention was given to the generalization of experimental data on hydraulic losses in the pipelines in case of mutual influence of local pressure drops, and to the modeling of natural convection in the fuel subassemblies and circuits with liquid metal cooling. Special emphasis at the meeting was placed on thermal hydraulics issues related to the development and design of target systems, such as heat removal in the target unit of the cascade subcritical reactor cooled by liquid salt; the target complex MK-1 for accelerator driven systems cooled by eutectic lead-bismuth alloy; and the test

Hydrodynamics and heat transfer in reactor components cooled by liquid metal coolants in single/two phase. 11. meeting of the International Association for Hydraulic Research (IAHR) Working Group. Working material

Energy Technology Data Exchange (ETDEWEB)

NONE

2005-07-01

This Working Material includes the papers presented at the International Meeting 'Hydrodynamics and heat transfer in reactor components cooled by liquid metal coolants in single/two-phase', which was held 5-9 July 2004 at the State Scientific Center of Russian Federation - Institute for Physics and Power Engineering named after A.I. Leypunsky, in Obninsk near Moscow. The objectives of the meeting were to discuss new results obtained in the field of liquid metal coolant and to recommend the lines of further general physics and applied investigations, with the purpose of validating existing and codes under development for liquid metal cooled advanced and new generation nuclear reactors. Most of the contributions present results of experimental and numerical investigations into velocity, temperature and heat transfer in fuel subassemblies of fast reactors cooled by sodium or lead. In the frame of the meeting a benchmark problem devoted to heat transfer in the model subassembly of the fast reactor BREST-OD-300 was proposed. Experts from 5 countries (Japan, Netherlands, Spain, Republic of Korea, and Russia) took part in this benchmark exercise. The results of the benchmark calculations are summarized in the Working Material. The results of hydrodynamic studies of pressure head chambers and collector systems of liquid metal cooled reactors are presented in a number of papers. Also attention was given to the generalization of experimental data on hydraulic losses in the pipelines in case of mutual influence of local pressure drops, and to the modeling of natural convection in the fuel subassemblies and circuits with liquid metal cooling. Special emphasis at the meeting was placed on thermal hydraulics issues related to the development and design of target systems, such as heat removal in the target unit of the cascade subcritical reactor cooled by liquid salt; the target complex MK-1 for accelerator driven systems cooled by eutectic lead-bismuth alloy; and the test

Heat and mass transfer in particulate suspensions

CERN Document Server

Michaelides, Efstathios E (Stathis)

2013-01-01

Heat and Mass Transfer in Particulate Suspensions is a critical review of the subject of heat and mass transfer related to particulate Suspensions, which include both fluid-particles and fluid-droplet Suspensions. Fundamentals, recent advances and industrial applications are examined. The subject of particulate heat and mass transfer is currently driven by two significant applications: energy transformations –primarily combustion – and heat transfer equipment. The first includes particle and droplet combustion processes in engineering Suspensions as diverse as the Fluidized Bed Reactors (FBR’s) and Internal Combustion Engines (ICE’s). On the heat transfer side, cooling with nanofluids, which include nanoparticles, has attracted a great deal of attention in the last decade both from the fundamental and the applied side and has produced several scientific publications. A monograph that combines the fundamentals of heat transfer with particulates as well as the modern applications of the subject would be...

Thermal radiation heat transfer

CERN Document Server

Howell, John R; Mengüç, M Pinar

2011-01-01

Providing a comprehensive overview of the radiative behavior and properties of materials, the fifth edition of this classic textbook describes the physics of radiative heat transfer, development of relevant analysis methods, and associated mathematical and numerical techniques. Retaining the salient features and fundamental coverage that have made it popular, Thermal Radiation Heat Transfer, Fifth Edition has been carefully streamlined to omit superfluous material, yet enhanced to update information with extensive references. Includes four new chapters on Inverse Methods, Electromagnetic Theory, Scattering and Absorption by Particles, and Near-Field Radiative Transfer Keeping pace with significant developments, this book begins by addressing the radiative properties of blackbody and opaque materials, and how they are predicted using electromagnetic theory and obtained through measurements. It discusses radiative exchange in enclosures without any radiating medium between the surfaces-and where heat conduction...

A heat transfer study for vertical straight-tube steam generators heated by liquid metal

International Nuclear Information System (INIS)

Valette, M.

1984-04-01

A single-tube mockup of a vertical straight-tube steam generator heated by sodium-potassium alloy NaK was submitted to thermal and hydraulic testing in conditions representative of fast breeder reactor operation. The mockup consisted of a 10mm I.D. ferritic steel heat exchange tube centered inside a cylindrical stainless steel shell. The complete assembly was 20.9 meters long. Water flowed upward inside the exchange tube, and NaK flowed downward in the annular gap between the tube and the shell. The steam outlet pressure ranged from 90 to 195 bars, while the liquid metal temperature at the mockup inlet was between 480 and 580 0 C. The water flowrate in the tube ranged from 153 to 2460 kg.m -2 .s -1 . During the tests the fluid inlet and outlet temperatures, flowrate and pressures were measured, as was the NaK temperature profile over the full length of the device. The test results were subsequently compared with heat exchange and pressure drop values calculated using the standard formulas for straight-tube heat exchangers. The heat exchange coefficients predicted by these correlations in the boiling zone were found to be largely overestimated, while the calculated pressure drop values proved satisfactory. A set of modified correlations is proposed to account for the observed phenomena, and for use in designing commercial units, provided the sodium flow in the tube bundle is adequately distributed

Required momentum, heat, and mass transport experiments for liquid-metal blankets

International Nuclear Information System (INIS)

Tillack, M.S.; Sze, D.K.; Abdou, M.A.

1986-01-01

Through the effects on fluid flow, many aspects of blanket behavior are affected by magnetohydrodynamic (MHD) effects, including pressure drop, heat transfer, mass transfer, and structural behavior. In this paper, a set of experiments is examined that could be performed in order to reduce the uncertainties in the highly related set of issues dealing with momentum, heat, and mass transport under the influence of a strong magnetic field (i.e., magnetic transport phenomena). By improving our basic understanding and by providing direct experimental data on blanket behavior, these experiments will lead to improved designs and an accurate assessment of the attractiveness of liquid-metal blankets

Effect of surface etching on condensing heat transfer

Energy Technology Data Exchange (ETDEWEB)

Seok, Sung Chul; Park, Jae Won; Jung, Jiyeon; Choi, Chonggun; Choi, Gyu Hong; Hwang, Seung Sik; Chung, Tae Yong; Shin, Donghoon [Kookmin University, Seoul (Korea, Republic of); Kim, Jin Jun [Hoseo University, Asan (Korea, Republic of)

2016-02-15

This study conducted experiments on humid air condensation during heat transfer in an air preheating exchanger attached to a home condensing boiler to improve thermal efficiency. An etchant composed of sulfuric acid and sodium nitrate was used to create roughness on the heat exchanger surface made from STS430J1L. A counter flow heat exchanger was fabricated to test the performance of heat transfer. Results showed that the overall heat transfer coefficients of all specimens treated with etchant improved with respect to the original specimens (not treated with etchant), and the overall heat transfer coefficient of the 60 s etching specimen increased by up to 15%. However, the increasing rate of the heat transfer coefficient was disproportional to the etching time. When the etching time specifically increased above 60 s, the heat transfer coefficient decreased. This effect was assumed to be caused by surface characteristics such as contact angle. Furthermore, a smaller contact angle or higher hydrophilicity leads to higher heat transfer coefficient.

Suppression of the sonic heat transfer limit in high-temperature heat pipes

Science.gov (United States)

Dobran, Flavio

1989-08-01

The design of high-performance heat pipes requires optimization of heat transfer surfaces and liquid and vapor flow channels to suppress the heat transfer operating limits. In the paper an analytical model of the vapor flow in high-temperature heat pipes is presented, showing that the axial heat transport capacity limited by the sonic heat transfer limit depends on the working fluid, vapor flow area, manner of liquid evaporation into the vapor core of the evaporator, and lengths of the evaporator and adiabatic regions. Limited comparisons of the model predictions with data of the sonic heat transfer limits are shown to be very reasonable, giving credibility to the proposed analytical approach to determine the effect of various parameters on the axial heat transport capacity. Large axial heat transfer rates can be achieved with large vapor flow cross-sectional areas, small lengths of evaporator and adiabatic regions or a vapor flow area increase in these regions, and liquid evaporation in the evaporator normal to the main flow.

Heat transfer enhancement using 2MHz ultrasound.

Science.gov (United States)

Bulliard-Sauret, Odin; Ferrouillat, Sebastien; Vignal, Laure; Memponteil, Alain; Gondrexon, Nicolas

2017-11-01

The present work focuses on possible heat transfer enhancement from a heating plate towards tap water in forced convection by means of 2MHz ultrasound. The thermal approach allows to observe the increase of local convective heat transfer coefficients in the presence of ultrasound and to deduce a correlation between ultrasound power and Nusselt number. Heat transfer coefficient under ultrasound remains constant while heat transfer coefficient under silent conditions increases with Reynolds number from 900 up to 5000. Therefore, heat transfer enhancement factor ranges from 25% up to 90% for the same energy conditions (supplied ultrasonic power=110W and supplied thermal power=450W). In the same time cavitational activity due to 2MHz ultrasound emission was characterized from mechanical and chemical viewpoints without significant results. At least, Particle Image Velocimetry (PIV) measurements have been performed in order to investigate hydrodynamic modifications due to the presence of 2MHz ultrasound. It was therefore possible to propose a better understanding of heat transfer enhancement mechanism with high frequency ultrasound. Copyright © 2017 Elsevier B.V. All rights reserved.

Engineering heat transfer

International Nuclear Information System (INIS)

Welty, J.R.

1974-01-01

The basic concepts of heat transfer are covered with special emphasis on up-to-date techniques for formulating and solving problems in the field. The discussion progresses logically from phenomenology to problem solving, and treats numerical, integral, and graphical methods as well as traditional analytical ones. The book is unique in its thorough coverage of the fundamentals of numerical analysis appropriate to solving heat transfer problems. This coverage includes several complete and readable examples of numerical solutions, with discussions and interpretations of results. The book also contains an appendix that provides students with physical data for often-encountered materials. An index is included. (U.S.)

Research progress on microgravity boiling heat transfer

International Nuclear Information System (INIS)

Xiao Zejun; Chen Bingde

2003-01-01

Microgravity boiling heat transfer is one of the most basic research topics in aerospace technology, which is important for both scientific research and engineering application. Research progress on microgravity boiling heat transfer is presented, including terrestrial simulation technique, terrestrial simulation experiment, microgravity experiment, and flow boiling heat transfer

Experimental investigation of heat transfer performance for a novel microchannel heat sink

International Nuclear Information System (INIS)

Wang, Y; Ding, G-F

2008-01-01

We demonstrated a novel microchannel heat sink with a high local heat transfer efficiency contributed by a complicated microchannel system, which comprises parallel longitudinal microchannels etched in a silicon substrate and transverse microchannels electroplated on a copper heat spreader. The thermal boundary layer develops in transverse microchannels. Meanwhile, the heat transfer area is increased compared with the conventional microchannel heat sink only having parallel longitudinal microchannels. Both benefits yield high local heat transfer efficiency and enhance the overall heat transfer, which is attractive for the cooling of high heat flux electronic devices. Infrared tests show the temperature distribution in the test objects. The effects of flow rate and heat flux levels on heat transfer characteristics are presented. A uniform temperature distribution is obtained through the heating area. The reference temperatures decrease with the increasing flow rate from 0.64 ml min −1 to 6.79 ml min −1 for a constant heat flux of 10.4 W cm −2 . A heat flux of 18.9 W cm −2 is attained at a flow rate of 6.79 ml min −1 for assuring the maximum temperature of the microchannel heat sink less than the maximum working temperature of electronic devices

Heat transfer capability analysis of heat pipe for space reactor

International Nuclear Information System (INIS)

Li Huaqi; Jiang Xinbiao; Chen Lixin; Yang Ning; Hu Pan; Ma Tengyue; Zhang Liang

2015-01-01

To insure the safety of space reactor power system with no single point failures, the reactor heat pipes must work below its heat transfer limits, thus when some pipes fail, the reactor could still be adequately cooled by neighbor heat pipes. Methods to analyze the reactor heat pipe's heat transfer limits were presented, and that for the prevailing capillary limit analysis was improved. The calculation was made on the lithium heat pipe in core of heat pipes segmented thermoelectric module converter (HP-STMC) space reactor power system (SRPS), potassium heat pipe as radiator of HP-STMC SRPS, and sodium heat pipe in core of scalable AMTEC integrated reactor space power system (SAIRS). It is shown that the prevailing capillary limits of the reactor lithium heat pipe and sodium heat pipe is 25.21 kW and 14.69 kW, providing a design margin >19.4% and >23.6%, respectively. The sonic limit of the reactor radiator potassium heat pipe is 7.88 kW, providing a design margin >43.2%. As the result of calculation, it is concluded that the main heat transfer limit of HP-STMC SRPS lithium heat pipe and SARIS sodium heat pipe is prevailing capillary limit, but the sonic limit for HP-STMC SRPS radiator potassium heat pipe. (authors)

Transient heat transfer in liquid helium

International Nuclear Information System (INIS)

Shiotsu, Masahiro

1991-01-01

Detailed knowledge on the steady-state and transient heat transfer from solid surfaces in He I and He II is important as a database for the analysis of the influence of local thermal disturbances on the stability of He I or He II cooled large superconducting magnets. In this paper, an overview of the transient heat transfer characteristics on solid surfaces in He I and He II caused by various large stepwise heat inputs, such as the quasi-steady nucleate boiling with a certain lifetime in He I and the quasi-steady Kapitza conductance heat flux with a certain lifetime in He II, are presented in comparison with their steady-state heat transfer characteristics. (author)

Evaluation of the decay heat removal capability using the concept of a thermosyphon in the liquid metal reactor

International Nuclear Information System (INIS)

Kim, Y. S.; Sim, Y. S.; Kim, W. K.

2000-01-01

A study related to understand the characteristics of the heat pipe and thermosyphon was performed to evaluate their applicabilities to the current PSDRS (Passive Safety Decay heat Removal System) in the KALIMER (Korea Advanced LIquid MEtal Reactor) design. The possible heat transfer rate by the heat pipe and thermosyphon was reviewed to compare the required capability in the PSDRS. A quantitative comparison was done between the current PSDRS and the modified PSDRS with the thermosyphon. The result showed the dominant heat transfer rate in the air channel, e.g. radiation or convection, is different from each other. The total heat transfer rate is not sensitive to the operating temperature of the thermosyphon. The heat removal by the air in the modified case is relatively reduced and the resultant outlet temperature appears less than above 10 .deg. C. A reversal heat transfer between the air and the thermosyphon may exist near the exit of the active heat transfer region. The total heat transfer rate by the modified case showed about 20∼40% increase relative to the reference one

Conjugate heat and mass transfer in heat mass exchanger ducts

CERN Document Server

Zhang, Li-Zhi

2013-01-01

Conjugate Heat and Mass Transfer in Heat Mass Exchanger Ducts bridges the gap between fundamentals and recent discoveries, making it a valuable tool for anyone looking to expand their knowledge of heat exchangers. The first book on the market to cover conjugate heat and mass transfer in heat exchangers, author Li-Zhi Zhang goes beyond the basics to cover recent advancements in equipment for energy use and environmental control (such as heat and moisture recovery ventilators, hollow fiber membrane modules for humidification/dehumidification, membrane modules for air purification, desi

Experimental and analytical study of natural-convection heat transfer of internally heated liquids

International Nuclear Information System (INIS)

Green, G.A.

1982-08-01

Boundary heat transfer from a liquid pool with a uniform internal heat source to a vertical or inclined boundary was investigated. The experiments were performed in an open rectangular liquid pool in which the internal heat source was generated by electrical heating. The local heat flux was measured to a boron nitride test wall which was able to be continuously inclined from vertical. Gold plated microthermocouples of 0.01 inch outside diameter were developed to measure the local surface temperature, both front and back, of the boron nitride. The local heat flux and, thus, the local heat transfer coefficient was measured at nineteen locations along the vertical axis of the test plate. A theoretical analysis of the coupled nonlinear boundary layer equations was performed. The parametric effect of the Prandtl number and the dimensionless wall temperature on the boundary heat transfer were investigated When the analytical model was used to calculate the boundary heat transfer data, agreement was achieved with the experimental data within 3% for the local heat transfer and within 2% for the average heat transfer

Analysis of the heat transfer in double and triple concentric tube heat exchangers

Science.gov (United States)

Rădulescu, S.; Negoiţă, L. I.; Onuţu, I.

2016-08-01

The tubular heat exchangers (shell and tube heat exchangers and concentric tube heat exchangers) represent an important category of equipment in the petroleum refineries and are used for heating, pre-heating, cooling, condensation and evaporation purposes. The paper presents results of analysis of the heat transfer to cool a petroleum product in two types of concentric tube heat exchangers: double and triple concentric tube heat exchangers. The cooling agent is water. The triple concentric tube heat exchanger is a modified constructive version of double concentric tube heat exchanger by adding an intermediate tube. This intermediate tube improves the heat transfer by increasing the heat area per unit length. The analysis of the heat transfer is made using experimental data obtained during the tests in a double and triple concentric tube heat exchanger. The flow rates of fluids, inlet and outlet temperatures of water and petroleum product are used in determining the performance of both heat exchangers. Principally, for both apparatus are calculated the overall heat transfer coefficients and the heat exchange surfaces. The presented results shows that triple concentric tube heat exchangers provide better heat transfer efficiencies compared to the double concentric tube heat exchangers.

Effects of stabilizers on the heat transfer characteristics of a nuclear waste canister

International Nuclear Information System (INIS)

Vafai, K.; Ettefagh, J.

1986-07-01

This report summarizes the feasibility and the effectiveness of using stabilizers (internal metal structural components) to augment the heat transfer characteristics of a nuclear waste canister. The problem was modeled as a transient two-dimensional heat transfer in two physical domains - the stabilizer and the wedge (a 30-degree-angle canister segment), which includes the heat-producing spent-fuel rods. This problem is solved by a simultaneous and interrelated numerical investigation of the two domains in cartesian and polar coordinate systems. The numerical investigations were performed for three cases. In the first case, conduction was assumed to be the dominant mechanism for heat transfer. The second case assumed that radiation was the dominant mechanism, and in the third case both radiation and conduction were considered as mechanisms of heat transfer. The results show that for typical conditions in a waste package design, the stabilizers are quite effective in reducing the overall temperature in a waste canister. Furthermore, the results show that increasing the stabilizer thickness over the thickness specified in the present design has a negligible effect on the temperature distribution in the canister. Finally, the presence of the stabilizers was found to shift the location of the peak temperature areas in the waste canister

Analysis of relations for heat transfer at the post-CHF regime

Energy Technology Data Exchange (ETDEWEB)

Dorokhovich, S. L. [Obninsk State Techical Univ., Obninsk (Russian Federation); Kirillov, P. L. [Institute of Physics and Power Engineering, Obninsk (Russian Federation)

2003-07-01

Information about heat transfer rates in two-fluid flow at the post-CHF regime is important for analysis of accidents of water-cooled nuclear reactors as well as calculations of steam generators (liquid metal-water). It is complicate to create analytical methods because there is a variety of two-fluid flow regimes dictated by channel size, pressure, mass flow rate, heat flux, droplet spectrum, flow quality, other factors and, finally, by crisis type. At crisis in subcooled liquid or low quality two-phase flows Inverted Annular Film Boiling (IAFB) takes place when liquid flow is separated from the wall by a thin superheated vapor film. For dispersed flow crisis is usually related to drying a liquid film moving along the heated surface (wall). In both cases two-phase flow is thermodynamically nonequilibrium since the temperatures of phases (liquid and vapor) are different. The mean (at the rate of heat content) flow temperature is not the determining parameter. Different boundary conditions of experiment s uniform heat fluxes or 'hot' spots, are able to lead to different relations for the heat transfer coefficient. Last years the great number of semiempirical models were elaborated, that become more and more complicate. It is difficult to examine many parameters of the models. An agreement between final results and separate experimental data is not yet the evidence for the verity of extension while prerequisites taken in the models are often doubtful and hardly examined. Thus the correlations obtained from experimental data, for example, are used in practice. The analysis of relations for heat transfer at the Deteriorated Heat Transfer (DHT) regime, the comparison of relations with the data of look up tables made on the basis of the Institute of Physics and Power Engineering and Chalk River Laboratories experimental data banks are the objective of current report.

Analysis of relations for heat transfer at the post-CHF regime

International Nuclear Information System (INIS)

Dorokhovich, S. L.; Kirillov, P. L.

2003-01-01

Information about heat transfer rates in two-fluid flow at the post-CHF regime is important for analysis of accidents of water-cooled nuclear reactors as well as calculations of steam generators (liquid metal-water). It is complicate to create analytical methods because there is a variety of two-fluid flow regimes dictated by channel size, pressure, mass flow rate, heat flux, droplet spectrum, flow quality, other factors and, finally, by crisis type. At crisis in subcooled liquid or low quality two-phase flows Inverted Annular Film Boiling (IAFB) takes place when liquid flow is separated from the wall by a thin superheated vapor film. For dispersed flow crisis is usually related to drying a liquid film moving along the heated surface (wall). In both cases two-phase flow is thermodynamically nonequilibrium since the temperatures of phases (liquid and vapor) are different. The mean (at the rate of heat content) flow temperature is not the determining parameter. Different boundary conditions of experiment s uniform heat fluxes or 'hot' spots, are able to lead to different relations for the heat transfer coefficient. Last years the great number of semiempirical models were elaborated, that become more and more complicate. It is difficult to examine many parameters of the models. An agreement between final results and separate experimental data is not yet the evidence for the verity of extension while prerequisites taken in the models are often doubtful and hardly examined. Thus the correlations obtained from experimental data, for example, are used in practice. The analysis of relations for heat transfer at the Deteriorated Heat Transfer (DHT) regime, the comparison of relations with the data of look up tables made on the basis of the Institute of Physics and Power Engineering and Chalk River Laboratories experimental data banks are the objective of current report

On the heat transfer correlation for membrane distillation

International Nuclear Information System (INIS)

Wang, Chi-Chuan

2011-01-01

Research highlights: → Heat transfer coefficients applicable for membrane distillation. → Data reduction for heat transfer coefficient for membrane distillation method. → Uncertainty of permeate side due to large magnitude of membrane resistance. → Increase accuracy of heat transfer coefficient by modified Wilson plot technique. -- Abstract: The present study examines the heat transfer coefficients applicable for membrane distillation. In the available literatures, researchers often adopt some existing correlations and claim the suitability of these correlations to their test data or models. Unfortunately this approach is quite limited and questionable. This is subject to the influences of boundary conditions, geometrical configurations, entry flow conditions, as well as some influences from spacer or support. The simple way is to obtain the heat transfer coefficients from experimentation. However there is no direct experimental data for heat transfer coefficients being reported directly from the measurements. The main reasons are from the uncertainty of permeate side and of the comparatively large magnitude of membrane resistance. Additional minor influence is the effect of mass transfer on the heat transfer performance. In practice, the mass transfer effect is negligible provided the feed side temperature is low. To increase the accuracy of the measured feed side heat transfer coefficient, it is proposed in this study to exploit a modified Wilson plot technique. Through this approach, one can eliminate the uncertainty from permeate side and reduce the uncertainty in membrane to obtain a more reliable heat transfer coefficients at feed side from the experimentation.

Finite element simulation of heat transfer

CERN Document Server

Bergheau, Jean-Michel

2010-01-01

This book introduces the finite element method applied to the resolution of industrial heat transfer problems. Starting from steady conduction, the method is gradually extended to transient regimes, to traditional non-linearities, and to convective phenomena. Coupled problems involving heat transfer are then presented. Three types of couplings are discussed: coupling through boundary conditions (such as radiative heat transfer in cavities), addition of state variables (such as metallurgical phase change), and coupling through partial differential equations (such as electrical phenomena).? A re

Evaluation of piping heat transfer, piping flow regimes, and steam generator heat transfer for the Semiscale Mod-1 isothermal tests

International Nuclear Information System (INIS)

French, R.T.

1975-08-01

Selected experimental data pertinent to piping heat transfer, transient fluid flow regimes, and steam generator heat transfer obtained during the Semiscale Mod-1 isothermal blowdown test series (Test Series 1) are analyzed. The tests in this first test series were designed to provide counterparts to the LOFT nonnuclear experiments. The data from the Semiscale Mod-1 intact and broken loop piping are evaluated to determine the surface heat flux and average heat transfer coefficients effective during the blowdown transient and compared with well known heat transfer correlations used in the RELAP4 computer program. Flow regimes in horizontal pipe sections are calculated and compared with data obtained from horizontal and vertical densitometers and with an existing steady state flow map. Effects of steam generator heat transfer are evaluated quantitatively and qualitatively. The Semiscale Mod-1 data and the analysis presented in this report are valuable for evaluating the adequacy and improving the predictive capability of analytical models developed to predict system response to piping heat transfer, piping flow regimes, and steam generator heat transfer during a postulated loss-of-coolant accident (LOCA) in a pressurized water reactor (PWR). 16 references. (auth)

Subcooled boiling heat transfer on a finned surface

International Nuclear Information System (INIS)

Kowalski, J.E.; Tran, V.T.; Mills, P.J.

1992-01-01

Experimental and numerical studies have been performed to determine the heat transfer coefficients from a finned cylindrical surface to subcooled boiling water. The heat transfer rates were measured in an annular test section consisting of an electrically heated fuel element simulator (FES) with eight longitudinal, rectangular fins enclosed in a glass tube. A two-dimensional finite-element heat transfer model using the Galerkin method was employed to determine the heat transfer coefficients along the periphery of the FES surface. An empirical correlation was developed to predict the heat transfer coefficients during subcooled boiling. The correlation agrees well with the measured data. (6 figures) (Author)

Engineering calculations in radiative heat transfer

CERN Document Server

Gray, W A; Hopkins, D W

1974-01-01

Engineering Calculations in Radiative Heat Transfer is a six-chapter book that first explains the basic principles of thermal radiation and direct radiative transfer. Total exchange of radiation within an enclosure containing an absorbing or non-absorbing medium is then described. Subsequent chapters detail the radiative heat transfer applications and measurement of radiation and temperature.

Industrial furnace with improved heat transfer

Energy Technology Data Exchange (ETDEWEB)

Hoetzl, M.; Lingle, T.M.

1992-07-07

This patent describes an industrial furnace for heating work which emits volatiles during heating. It comprises a generally cylindrical, closed end furnace section defining a sealable heat transfer chamber for heating work disposed therein; fan means for directing furnace atmosphere as a swirling wind mass about the interior of the furnace section over a portion thereof; heat means for heating the wind mass within the fan chamber; and an incineration track formed as a circumferentially extending groove about the exterior of the furnace section and in heat transfer relationship with and situated at least to extend about a portion of the fan chamber.

Transient thermal and nonthermal electron and phonon relaxation after short-pulsed laser heating of metals

International Nuclear Information System (INIS)

Giri, Ashutosh; Hopkins, Patrick E.

2015-01-01

Several dynamic thermal and nonthermal scattering processes affect ultrafast heat transfer in metals after short-pulsed laser heating. Even with decades of measurements of electron-phonon relaxation, the role of thermal vs. nonthermal electron and phonon scattering on overall electron energy transfer to the phonons remains unclear. In this work, we derive an analytical expression for the electron-phonon coupling factor in a metal that includes contributions from equilibrium and nonequilibrium distributions of electrons. While the contribution from the nonthermal electrons to electron-phonon coupling is non-negligible, the increase in the electron relaxation rates with increasing laser fluence measured by thermoreflectance techniques cannot be accounted for by only considering electron-phonon relaxations. We conclude that electron-electron scattering along with electron-phonon scattering have to be considered simultaneously to correctly predict the transient nature of electron relaxation during and after short-pulsed heating of metals at elevated electron temperatures. Furthermore, for high electron temperature perturbations achieved at high absorbed laser fluences, we show good agreement between our model, which accounts for d-band excitations, and previous experimental data. Our model can be extended to other free electron metals with the knowledge of the density of states of electrons in the metals and considering electronic excitations from non-Fermi surface states

Fundamental principles of heat transfer

CERN Document Server

Whitaker, Stephen

1977-01-01

Fundamental Principles of Heat Transfer introduces the fundamental concepts of heat transfer: conduction, convection, and radiation. It presents theoretical developments and example and design problems and illustrates the practical applications of fundamental principles. The chapters in this book cover various topics such as one-dimensional and transient heat conduction, energy and turbulent transport, forced convection, thermal radiation, and radiant energy exchange. There are example problems and solutions at the end of every chapter dealing with design problems. This book is a valuable int

Numerical simulation of fluid flow and heat transfer in a concentric tube heat exchanger

International Nuclear Information System (INIS)

Mokamati, S.V.; Prasad, R.C.

2003-01-01

In this paper, numerical simulation of a concentric tube heat exchanger is presented to determine the convective heat transfer coefficient and friction factor in a smooth tube. Increasing the convective heat transfer coefficient can increase heat transfer rate in a concentric tube heat exchanger from a given tubular surface area. This can be achieved by using heat transfer augmentation devices. This work constitutes the initial phase of the numerical simulation of heat transfer from tubes employing augmentation devices, such as twisted tapes, wire-coil inserts, for heat transfer enhancement. A computational fluid dynamics (CFD) simulation tool was developed with CFX software and the results obtained from the simulations are validated with the empirical correlations for a smooth tube heat exchanger. The difficulties associated with the simulation of a heat exchanger augmented with wire-coil inserts are discussed. (author)

Visualisation of heat transfer in unsteady laminar flows

NARCIS (Netherlands)

Speetjens, M.F.M.; Steenhoven, van A.A.

2011-01-01

Heat transfer in fluid flows traditionally is examined in terms of temperature fields and heat-transfer coefficients. However, heat transfer may alternatively be considered as the transport of thermal energy by the total convective-conductive heat flux in a way analogous to the transport of fluid by

Internally Heated Screw Pyrolysis Reactor (IHSPR) heat transfer performance study

Science.gov (United States)

Teo, S. H.; Gan, H. L.; Alias, A.; Gan, L. M.

2018-04-01

1.5 billion end-of-life tyres (ELT) were discarded globally each year and pyrolysis is considered the best solution to convert the ELT into valuable high energy-density products. Among all pyrolysis technologies, screw reactor is favourable. However, conventional screw reactor risks plugging issue due to its lacklustre heat transfer performance. An internally heated screw pyrolysis reactor (IHSPR) was developed by local renewable energy industry, which serves as the research subject for heat transfer performance study of this particular paper. Zero-load heating test (ZLHT) was first carried out to obtain the operational parameters of the reactor, followed by the one dimensional steady-state heat transfer analysis carried out using SolidWorks Flow Simulation 2016. Experiments with feed rate manipulations and pyrolysis products analyses were conducted last to conclude the study.

Heat transfer coefficient for boiling carbon dioxide

DEFF Research Database (Denmark)

Knudsen, Hans Jørgen Høgaard; Jensen, Per Henrik

1998-01-01

Heat transfer coefficient and pressure drop for boiling carbon dioxide (R744) flowing in a horizontal pipe has been measured. The calculated heat transfer coeeficient has been compared with the Chart correlation of Shah. The Chart Correlation predits too low heat transfer coefficient but the ratio...... between the measured and the calculated heat transfer coefficient is nearly constant and equal 1.9. With this factor the correlation predicts the measured data within 14% (RMS). The pressure drop is of the same order as the measuring uncertainty and the pressure drop has not been compared with correlation's....

Condition monitoring of steam generator by estimating the overall heat transfer coefficient

International Nuclear Information System (INIS)

Furusawa, Hiroaki; Gofuku, Akio

2013-01-01

This study develops a technique for monitoring in on-line the state of the steam generator of the fast-breeder reactor (FBR) “Monju”. Because the FBR uses liquid sodium as coolant, it is necessary to handle liquid sodium with caution due to its chemical characteristics. The steam generator generates steam by the heat of secondary sodium coolant. The sodium-water reaction may happen if a pinhole or crack occurs at the thin metal tube wall that separates the secondary sodium coolant and water/steam. Therefore, it is very important to detect an anomaly of the wall of heat transfer tubes at an early stage. This study aims at developing an on-line condition monitoring technique of the steam generator by estimating overall heat transfer coefficient from process signals. This paper describes simplified mathematical models of superheater and evaporator to estimate the overall heat transfer coefficient and a technique to diagnose the state of the steam generator. The applicability of the technique is confirmed by several estimations using simulated process signals with artificial noises. The results of the estimations show that the developed technique can detect the occurrence of an anomaly. (author)

Heat transfer coefficient of cryotop during freezing.

Science.gov (United States)

Li, W J; Zhou, X L; Wang, H S; Liu, B L; Dai, J J

2013-01-01

Cryotop is an efficient vitrification method for cryopreservation of oocytes. It has been widely used owing to its simple operation and high freezing rate. Recently, the heat transfer performance of cryotop was studied by numerical simulation in several studies. However, the range of heat transfer coefficient in the simulation is uncertain. In this study, the heat transfer coefficient for cryotop during freezing process was analyzed. The cooling rates of 40 percent ethylene glycol (EG) droplet in cryotop during freezing were measured by ultra-fast measurement system and calculated by numerical simulation at different value of heat transfer coefficient. Compared with the results obtained by two methods, the range of the heat transfer coefficient necessary for the numerical simulation of cryotop was determined, which is between 9000 W/(m(2)·K) and 10000 W/(m (2)·K).

Exploratory heat transfer studies on critical elements of a proposed 6 GeV synchrotron

International Nuclear Information System (INIS)

Kuzay, T.M.; Knapp, G.S.

1985-11-01

Certain types of insertion devices for angiography, can produce extraordinarily large heat fluxes on critical components of a synchrotron beam line and its optics. The shutters, beam splitters, filters, and the first-stage monochromators all are subjected to large fluxes of radiation. The cooling requirements of such beam line components are approached in a comprehensive manner to identify the governing parameters from first principles. Analytical techniques have been used to study various methods of handling the heat loads using both liquid metal and water coolants for various potential heated geometries. It is found that when properly designed, liquid metal cooling can be much more efficient. In addition, composites and low Z surfaces have been considered. Also investigated are the heat transfer problems of the optical stages and rotating monochromators

Exploratory heat transfer studies on critical elements of a proposed 6 GeV synchrotron

International Nuclear Information System (INIS)

Kuzay, T.M.; Knapp, G.S.

1986-01-01

Certain types of insertion devices for angiography can produce extraordinarily large heat fluxes on critical components of a synchrotron beam line and its optics. The shutters, beam splitters, filters, and the first-stage monochromators all are subjected to large fluxes of radiation. The cooling requirements of such beam line components are approached in a comprehensive manner to identify the governing parameters from first principles. Analytical techniques have been used to study various methods of handling the heat loads using both liquid metal and water coolants for various potential heated geometries. It is found that when properly designed, liquid metal cooling can be much more efficient. In addition, composites and low Z surfaces have been considered. Also investigated are the heat transfer problems of the optical stages and rotating monochromators

Computational simulation of heat transfer in laser melted material flow

International Nuclear Information System (INIS)

Shankar, V.; Gnanamuthu, D.

1986-01-01

A computational procedure has been developed to study the heat transfer process in laser-melted material flow associated with surface heat treatment of metallic alloys to improve wear-and-tear and corrosion resistance. The time-dependent incompressible Navier-Stokes equations are solved, accounting for both convective and conductive heat transfer processes. The convection, induced by surface tension and high surface temperature gradients, sets up a counterrotating vortex flow within the molten pool. This recirculating material flow is responsible for determining the molten pool shape and the associated cooling rates which affect the solidifying material composition. The numerical method involves an implicit triple-approximate factorization scheme for the energy equation, and an explicit treatment for the momentum and the continuity equations. An experimental setup, using a continuous wave CO 2 laser beam as a heat source, has been carried out to generate data for validation of the computational model. Results in terms of the depth, width, and shape of the molten pool and the heat-affected zone for various power settings and shapes of the laser, and for various travel speeds of the workpiece, compare very well with experimental data. The presence of the surface tension-induced vortex flow is demonstrated

Heat transfer characteristics and limitations analysis of heat-pipe-cooled thermal protection structure

International Nuclear Information System (INIS)

Guangming, Xiao; Yanxia, Du; Yewei, Gui; Lei, Liu; Xiaofeng, Yang; Dong, Wei

2014-01-01

The theories of heat transfer, thermodynamics and fluid dynamics are employed to develop the coupled heat transfer analytical methods for the heat-pipe-cooled thermal protection structure (HPC TPS), and a three-dimensional numerical method considering the sonic limit of heat pipe is proposed. To verify the calculation correctness, computations are carried out for a typical heat pipe and the results agree well with experimental data. Then, the heat transfer characteristics and limitations of HPC TPS are mainly studied. The studies indicate that the use of heat pipe can reduce the temperature at high heat flux region of structure efficiently. However, there is a frozen startup period before the heat pipe reaching a steady operating state, and the sonic limit will be a restriction on the heat transfer capability. Thus, the effects of frozen startup must be considered for the design of HPC TPS. The simulation model and numerical method proposed in this paper can predict the heat transfer characteristics of HPC TPS quickly and exactly, and the results will provide important references for the design or performance evaluation of HPC TPS. - Highlights: • Numerical methods for the heat-pipe-cooled thermal protection structure are studied. • Three-dimensional simulation model considering sonic limit of heat pipe is proposed. • The frozen startup process of the embedded heat pipe can be predicted exactly. • Heat transfer characteristics of TPS and limitations of heat pipe are discussed

Simulations and experiments of laminar heat transfer for Therminol heat transfer fluids in a rifled tube

International Nuclear Information System (INIS)

Xu, Weiguo; Ren, Depeng; Ye, Qing; Liu, Guodong; Lu, Huilin; Wang, Shuai

2016-01-01

Graphical abstract: Predicted laminar Nusselt number using regression correlation of Therminol-55 heat transfer fluid is in agreement with experiments in the rifled tube. - Highlights: • Heat transfer coefficient and friction factor are measured and predicted in the rifled tube. • Correlations for Nusselt number and friction factor are proposed. • The roughness height of 0.425 mm in transition SST model is suggested as an input parameter. • k–kl–ω transition and transition SST models are recommended for laminar–turbulent transition. • Thermal enhancement factor and synergy angle are predicted in the rifled tube. - Abstract: Simulations and experiments of flow and heat transfer behavior of Therminol-55 heat transfer fluid have been conducted in a horizontal rifled tube with outer diameter and inner diameter 25.0 and 20.0 mm, pitch and rib height of 12.0 and 1.0 mm, respectively. Numerical simulations of three-dimensional flow behavior of Therminol-55 heat transfer fluid are carried out using FLUENT code in the rifled tube. Experimental results show that the heat transfer and thermal performance of Therminol-55 heat transfer fluid in the rifled tube are considerably improved compared to those of the smooth tube. The Nusselt number increases with the increase of Reynolds number, and is from 3.5 to 5.1 times over the smooth tube. Also, the pressure drop results reveal that the average friction factor of the ribbed tube is in a range of 2.2 and 4.2 times over the smooth tube. Predictive Nusselt number and friction factor correlations have been presented. The numerical results show that the laminar flow model is valid only at lower Reynolds number in the developed laminar flow of rifled tube. The k–kl–ω transition model and transition SST model with roughness of 0.425 mm are recommended for the predictions of transition process from laminar to turbulent flow in the rifled tube.

Modeling microscale heat transfer using Calore.

Energy Technology Data Exchange (ETDEWEB)

Gallis, Michail A.; Rader, Daniel John; Wong, Chung-Nin Channy; Bainbridge, Bruce L.; Torczynski, John Robert; Piekos, Edward Stanley

2005-09-01

Modeling microscale heat transfer with the computational-heat-transfer code Calore is discussed. Microscale heat transfer problems differ from their macroscopic counterparts in that conductive heat transfer in both solid and gaseous materials may have important noncontinuum effects. In a solid material, three noncontinuum effects are considered: ballistic transport of phonons across a thin film, scattering of phonons from surface roughness at a gas-solid interface, and scattering of phonons from grain boundaries within the solid material. These processes are modeled for polycrystalline silicon, and the thermal-conductivity values predicted by these models are compared to experimental data. In a gaseous material, two noncontinuum effects are considered: ballistic transport of gas molecules across a thin gap and accommodation of gas molecules to solid conditions when reflecting from a solid surface. These processes are modeled for arbitrary gases by allowing the gas and solid temperatures across a gas-solid interface to differ: a finite heat transfer coefficient (contact conductance) is imposed at the gas-solid interface so that the temperature difference is proportional to the normal heat flux. In this approach, the behavior of gas in the bulk is not changed from behavior observed under macroscopic conditions. These models are implemented in Calore as user subroutines. The user subroutines reside within Sandia's Source Forge server, where they undergo version control and regression testing and are available to analysts needing these capabilities. A Calore simulation is presented that exercises these models for a heated microbeam separated from an ambient-temperature substrate by a thin gas-filled gap. Failure to use the noncontinuum heat transfer models for the solid and the gas causes the maximum temperature of the microbeam to be significantly underpredicted.

Flow and heat transfer in a curved channel

Science.gov (United States)

Brinich, P. F.; Graham, R. W.

1977-01-01

Flow and heat transfer in a curved channel of aspect ratio 6 and inner- to outer-wall radius ratio 0.96 were studied. Secondary currents and large longitudinal vortices were found. The heat-transfer rates of the outer and inner walls were independently controlled to maintain a constant wall temperature. Heating the inner wall increased the pressure drop along the channel length, whereas heating the outer wall had little effect. Outer-wall heat transfer was as much as 40 percent greater than the straight-channel correlation, and inner-wall heat transfer was 22 percent greater than the straight-channel correlation.

Non-Uniform Heat Transfer in Thermal Regenerators

DEFF Research Database (Denmark)

Jensen, Jesper Buch

, a numerical model, which simulates a single-blow operation in a parallel-plate regenerator, was developed and used to model the heat transfer under various conditions. In addition to the modeling of the heat transfer, a series of experiments on passive regenerators with non-uniform, but precisely controlled....... Additionally, the experiments gave real comparative results, whereas the model to a certain degree more served to provide insight to the heat transfer processes taking place inside the regenera- tors, something that would be - if not impossible - then highly impractical to do experimentally. It has been found......This thesis presents investigations on the heat transfer in complex heat ex- changers in general and in regenerative heat exchangers (regenerators) in par- ticular. The motivation for this work is a result of inconsistencies obeserved in the results from a series of experiments on active magnetic...

Cooperative heat transfer and ground coupled storage system

Science.gov (United States)

Metz, P.D.

A cooperative heat transfer and ground coupled storage system wherein collected solar heat energy is ground stored and permitted to radiate into the adjacent ground for storage therein over an extended period of time when such heat energy is seasonally maximally available. Thereafter, when said heat energy is seasonally minimally available and has propagated through the adjacent ground a substantial distance, the stored heat energy may be retrieved by a circumferentially arranged heat transfer means having a high rate of heat transfer.

Heat transfer enhancement with nanofluids

CERN Document Server

Bianco, Vincenzo; Nardini, Sergio; Vafai, Kambiz

2015-01-01

Properties of NanofluidSamuel Paolucci and Gianluca PolitiExact Solutions and Their Implications in Anomalous Heat TransferWenhao Li, Chen Yang and Akira NakayamaMechanisms and Models of Thermal Conductivity in NanofluidsSeung-Hyun Lee and Seok Pil JangExperimental Methods for the Characterization of Thermophysical Properties of NanofluidsSergio Bobbo and Laura FedeleNanofluid Forced ConvectionGilles RoyExperimental Study of Convective Heat Transfer in NanofluidsEhsan B. Haghighi, Adi T. Utomo, Andrzej W. Pacek and Björn E. PalmPerformance of Heat Exchangers Using NanofluidsBengt Sundén and Za

Heat transfer in Rockwool modelling and method of measurement. The effect of natural convection on heat transfer in fibrous materials

Energy Technology Data Exchange (ETDEWEB)

Dyrboel, Susanne

1998-05-01

Fibrous materials are some of the most widely used materials for thermal insulation. In this project the focus of interest has been on fibrous materials for building application. Interest in improving the thermal properties of insulation materials is increasing as legislation is being tightened to reduce the overall energy consumption. A knowledge of the individual heat transfer mechanisms - whereby heat is transferred within a particular material is an essential tool to improve continuously the thermal properties of the material. Heat is transferred in fibrous materials by four different transfer mechanisms: conduction through air, conduction through fibres, thermal radiation and convection. In a particular temperature range the conduction through air can be regarded as a constant, and conduction through fibres is an insignificant part of the total heat transfer. Radiation, however, constitutes 25-40% of the total heat transfer in light fibrous materials. In Denmark and a number of other countries convection in fibrous materials is considered as non-existent when calculating heat transmission as well as when designing building structures. Two heat transfer mechanisms have been the focus of the current project: radiation heat transfer and convection. The radiation analysis serves to develop a model that can be used in further work to gain a wider knowledge of the way in which the morphology of the fibrous material, i.e. fibre diameter distribution, fibre orientation distribution etc., influences the radiation heat transfer under different conditions. The convection investigation serves to examine whether considering convection as non-existent is a fair assumption to use in present and future building structures. The assumption applied in practically is that convection makes a notable difference only in very thick insulation, at external temperatures below -20 deg. C, and at very low densities. For large thickness dimensions the resulting heat transfer through the

Heat transfer unit and method for prefabricated vessel

Science.gov (United States)

Tamburello, David A.; Kesterson, Matthew R; Hardy, Bruce J.

2017-11-07

Vessel assemblies, heat transfer units for prefabricated vessels, and methods for heat transfer prefabricated vessel are provided. A heat transfer unit includes a central rod, and a plurality of peripheral rods surrounding the central rod and connected to the central rod. The plurality of peripheral rods are movable between a first collapsed position and a second bowed position, wherein in the second bowed position a midpoint of each of the plurality of peripheral rods is spaced from the central rod relative to in the first position. The heat transfer unit further includes a heat transfer element connected to one of the plurality of peripheral rods.

Study on enhancement of heat transfer of RVACS

International Nuclear Information System (INIS)

Nishi, Yoshihisa; Kinoshita, Izumi

1989-01-01

As for the enhancement of heat transfer on Reactor Vessel Auxiliary Cooling System (RVACS), utilization of high porosity porous bodies have been proposed by the last report. This report describe the experimental results to evaluate heat transfer performance of the porous bodies and to estimate the extrapolation to long heat transfer surface such as reactor scale. Following are typical results. (1) Usually the Heat Transfer coefficient at the lower reaches is smoller than that of the upper reaches. But Using with the high porosity porous bodies, the Heat Transfer coefficient at the lower reaches remains a constant value against distance from entrance point or a increase slightly compared to that of the upper reaches because of the effect of thermal radiation. (2) From the results of Heat Transfer coefficients against distance from the entrance point, the increasing ratio of enhancement of heat removal in the case of reactor scale is about 1.3. (author)

Supercritical heat transfer phenomena in nuclear system

International Nuclear Information System (INIS)

Seo, Kyoung Woo; Kim, Moo Hwan; Anderson, Mark H.; Corradini, Michael L.

2005-01-01

A supercritical water (SCW) power cycle has been considered as one of the viable candidates for advanced fission reactor designs. However, the dramatic variation of thermo-physical properties with a modest change of temperature near the pseudo-critical point make existing heat transfer correlations such as the Dittus-Boelter correlation not suitably accurate to calculate the heat transfer in supercritical fluid. Several other correlations have also been suggested but none of them are able to predict the heat transfer over a parameter range, needed for reactor thermal-hydraulics simulation and design. This has prompted additional research to understand the characteristic of supercritical fluid heat transfer

Proceedings of the 33rd national heat transfer conference NHTC'99

International Nuclear Information System (INIS)

Jensen, M.K.; Di Marzo, M.

1999-01-01

The papers in this conference were divided into the following sections: Radiation Heat Transfer in Fires; Computational Fluid Dynamics Methods in Two-Phase Flow; Heat Transfer in Microchannels; Thin Film Heat Transfer; Thermal Design of Electronics; Enhanced Heat Transfer I; Porous Media Convection; Contact Resistance Heat Transfer; Materials Processing in Solidification and Crystal Growth; Fundamentals of Combustion; Challenging Modeling Aspects of Radiative Transfer; Fundamentals of Microscale Transport; Laser Processing and Diagnostics for Manufacturing and Materials Processing; Experimental Studies of Multiphase Flow; Enhanced Heat Transfer II; Heat and Mass Transfer in Porous Media; Heat Transfer in Turbomachinery and Gas Turbine Systems; Conduction Heat Transfer; General Papers; Open Forum on Combustion; Combustion and Instrumentation and Diagnostics I; Radiative Heat Transfer and Interactions in Participating and Nonparticipating Media; Applications of Computational Heat Transfer; Heat Transfer and Fluid Aspects of Heat Exchangers; Two-Phase Flow and Heat Transfer Phenomena; Fundamentals of Natural and Mixed Convection Heat Transfer I; Fundamental of Natural and Mixed Convection Heat Transfer II; Combustion and Instrumentation and Diagnostics II; Computational Methods for Multidimensional Radiative Transfer; Process Heat Transfer; Advances in Computational Heat and Mass Transfer; Numerical Methods for Porous Media; Transport Phenomena in Manufacturing and Materials Processing; Practical Combustion; Melting and Solidification Heat Transfer; Transients in Dynamics of Two-Phase Flow; Basic Aspects of Two-Phase Flow; Turbulent Heat Transfer; Convective Heat Transfer in Electronics; Thermal Problems in Radioactive and Mixed Waste Management; and Transport Phenomena in Oscillatory Flows. Separate abstracts were prepared for most papers in this conference

A study on the heat transfer characteristics of a self-oscillating heat pipe

International Nuclear Information System (INIS)

Yoon, Seok Hun; Oh, Cheol; Choi, Jae Hyuk

2002-01-01

In this paper, the heat transfer characteristics of a self-oscillating heat pipe are experimentally investigated for the effect of various working fluid fill charge ratios and heat loads. The characteristics of temperature oscillations of the working fluid are also analysed based on chaotic dynamics. The heat pipe is composed of a heating section, a cooling section and an adiabatic section, and has a 0.002m internal diameter, a 0.34m length in each turn and consists of 19 turns. The heating and the cooling portion of each turn has a length of 70mm. A series of experiments was carried out to measure the temperature distributions and the pressure variations of the heat pipe. Furthermore, heat transfer performance, effective thermal conductivity, boiling heat transfer and condensation heat transfer coefficients are calculated for various operating conditions. Experimental results show the efficacy of this type of heat pipe

Heat transfer enhancement in heat exchangers by longitudinal vortex generators

International Nuclear Information System (INIS)

Guntermann, T.; Fiebig, M.; Mitra, N.K.

1990-01-01

In this paper heat transfer enhancement and flow losses are computed for the interaction of a laminar channel flow with a pair of counterrotating longitudinal vortices generated by a pair of delta-winglets punched out of the channel wall. The geometry simulates an element of a fin-plate or fin-tube heat exchanger. The structure of the vortex flow and temperature distribution, the local heat transfer coefficients and the local flow losses are discussed for a sample case. For a Reynolds number of Re d = 1000 and a vortex generator angle of attack of β = 25 degrees heat transfer is enhanced locally by more than 300% and in the mean by 50%. These values increase further with Re and β

Heat Transfer Phenomena of Supercritical Fluids

Energy Technology Data Exchange (ETDEWEB)

Krau, Carmen Isabella; Kuhn, Dietmar; Schulenberg, Thomas [Forschungszentrum Karlsruhe, Institute for Nuclear and Energy Technologies, 76021 Karlsruhe (Germany)

2008-07-01

In concepts for supercritical water cooled reactors, the reactor core is cooled and moderated by water at supercritical pressures. The significant temperature dependence of the fluid properties of water requires an exact knowledge of the heat transfer mechanism to avoid fuel pin damages. Near the pseudo-critical point a deterioration of heat transfer might happen. Processes, that take place in this case, are not fully understood and are due to be examined systematically. In this paper a general overview on the properties of supercritical water is given, experimental observations of different authors will be reviewed in order to identify heat transfer phenomena and onset of occurrence. The conceptional design of a test rig to investigate heat transfer in the boundary layer will be discussed. Both, water and carbon dioxide, may serve as operating fluids. The loop, including instrumentation and safety devices, is shown and suitable measuring methods are described. (authors)

A one-dimensional heat transfer model for parallel-plate thermoacoustic heat exchangers

NARCIS (Netherlands)

de Jong, Anne; Wijnant, Ysbrand H.; de Boer, Andries

2014-01-01

A one-dimensional (1D) laminar oscillating flow heat transfer model is derived and applied to parallel-plate thermoacoustic heat exchangers. The model can be used to estimate the heat transfer from the solid wall to the acoustic medium, which is required for the heat input/output of thermoacoustic

Near-field heat transfer between graphene/hBN multilayers

OpenAIRE

Zhao, Bo; Guizal, Brahim; Zhang, Zhuomin M.; Fan, Shanhui; Antezza, Mauro

2017-01-01

We study the radiative heat transfer between multilayer structures made by a periodic repetition of a graphene sheet and a hexagonal boron nitride (hBN) slab. Surface plasmons in a monolayer graphene can couple with a hyperbolic phonon polaritons in a single hBN film to form hybrid polaritons that can assist photon tunneling. For periodic multilayer graphene/hBN structures, the stacked metallic/dielectric array can give rise to a further effective hyperbolic behavior, in addition to the intri...

Enhancement of heat and mass transfer by cavitation

International Nuclear Information System (INIS)

Zhang, Y N; Du, X Z; Xian, H Z; Zhang, Y N

2015-01-01

In this paper, a brief summary of effects of cavitation on the heat and mass transfer are given. The fundamental studies of cavitation bubbles, including its nonlinearity, rectified heat and mass diffusion, are initially introduced. Then selected topics of cavitation enhanced heat and mass transfer were discussed in details including whales stranding caused by active sonar activity, pool boiling heat transfer, oscillating heat pipe and high intensity focused ultrasound treatment

Single-phase convection heat transfer characteristics of pebble-bed channels with internal heat generation

International Nuclear Information System (INIS)

Meng Xianke; Sun Zhongning; Xu Guangzhan

2012-01-01

Graphical abstract: The core of the water-cooled pebble bed reactor is the porous channels which stacked with spherical fuel elements. The gaps between the adjacent fuel elements are complex because they are stochastic and often shift. We adopt electromagnetic induction heating method to overall heat the pebble bed. By comparing and analyzing the experimental data, we get the rule of power distribution and the rule of heat transfer coefficient with particle diameter, heat flux density, inlet temperature and working fluid's Re number. Highlights: ► We adopt electromagnetic induction heating method to overall heat the pebble bed to be the internal heat source. ► The ball diameter is smaller, the effect of the heat transfer is better. ► With Re number increasing, heat transfer coefficient is also increasing and eventually tends to stabilize. ► The changing of heat power makes little effect on the heat transfer coefficient of pebble bed channels. - Abstract: The reactor core of a water-cooled pebble bed reactor includes porous channels that are formed by spherical fuel elements. This structure has notably improved heat transfer. Due to the variability and randomness of the interstices in pebble bed channels, heat transfer is complex, and there are few studies regarding this topic. To study the heat transfer characters of pebble bed channels with internal heat sources, oxidized stainless steel spheres with diameters of 3 and 8 mm and carbon steel spheres with 8 mm diameters are used in a stacked pebble bed. Distilled water is used as a refrigerant for the experiments, and the electromagnetic induction heating method is used to heat the pebble bed. By comparing and analyzing the experimental results, we obtain the governing rules for the power distribution and the heat transfer coefficient with respect to particle diameter, heat flux density, inlet temperature and working fluid Re number. From fitting of the experimental data, we obtain the dimensionless average

Experimental study on local heat transfer characteristics of porous media with internal heat source

International Nuclear Information System (INIS)

Zan Yuanfeng; Wang Taotao; Xiao Zejun; Wang Fei; Huang Yanping

2008-01-01

Model of porous media with internal heat source is established. The model uses water as flowing media, and the stainless steel test section is packed with steel spheres in manner of regular triangle, respectively. The armoured resistance wire is inserted inside the steel sphere. On the basis of the experimental model, many parameters of the local heat transfer characteristics including current velocity and wall temperature of steel sphere are measured. The experimental results show that the coefficient of heat transfer scarcely changes with pressure. The coefficient of heat transfer increases with the surface heat flux of steel sphere. When raising the inlet temperature of the cooling water, the coefficient of heat transfer presents the descending trend. In addition, the influence of entrance effect on heat transfer is discovered in the experiment, which is much less than the liquid flow in the light tube. After experiment data are analyzed and processed, the relation model of heat transfer on local heat transfer characteristic of porous media with internal heat source was described with a power-law-equation. The deviations between calculation and experimental values are within ±10%. (authors)

Forced convection heat transfer in He II

International Nuclear Information System (INIS)

Kashani, A.

1986-01-01

An investigation of forced convection heat transfer in He II is conducted. The study includes both experimental and theoretical treatments of the problem. The experiment consists of a hydraulic pump and a copper flow tube, 3 mm in ID and 2m long. The system allows measurements of one-dimensional heat and mass transfer in He II. The heat transfer experiments are performed by applying heat at the midpoint along the length of the flow tube. Two modes of heat input are employed, i.e., step function heat input and square pulse heat input. The heat transfer results are discussed in terms of temperature distribution in the tube. The experimental temperature profiles are compared with numerical solutions of an analytical model developed from the He II energy equation. The bath temperature is set at three different values of 1.65, 1.80, and 1.95 K. The He II flow velocity is varied up to 90 cm/s. Pressure is monitored at each end of the flow tube, and the He II pressure drop is obtained for different flow velocities. Results indicate that He II heat transfer by forced convention is considerably higher than that by internal convection. The theoretical model is in close agreement with the experiment. He II pressure drop and friction factor are very similar to those of an ordinary fluid

Application of intensified heat transfer for the retrofit of heat exchanger network

International Nuclear Information System (INIS)

Wang, Yufei; Pan, Ming; Bulatov, Igor; Smith, Robin; Kim, Jin-Kuk

2012-01-01

Highlights: → Novel design approach for the retrofit of HEN based on intensified heat transfer. → Development of a mathematical model to evaluate shell-and-tube heat exchanger performances. → Identification of the most appropriate heat exchangers requiring heat transfer enhancements in the heat exchanger network. -- Abstract: A number of design methods have been proposed for the retrofit of heat exchanger networks (HEN) during the last three decades. Although considerable potential for energy savings can be identified from conventional retrofit approaches, the proposed solutions have rarely been adopted in practice, due to significant topology modifications required and resulting engineering complexities during implementation. The intensification of heat transfer for conventional shell-and-tube heat exchangers can eliminate the difficulties of implementing retrofit in HEN which are commonly restricted by topology, safety and maintenance constraints, and includes high capital costs for replacing equipment and pipelines. This paper presents a novel design approach to solve HEN retrofit problems based on heat transfer enhancement. A mathematical model has been developed to evaluate shell-and-tube heat exchanger performances, with which heat-transfer coefficients and pressure drops for both fluids in tube and shell sides are obtained. The developed models have been compared with the Bell-Delaware, simplified Tinker and Wills-Johnston methods and tested with the HTRI (registered) and HEXTRAN (registered) software packages. This demonstrates that the new model is much simpler but can give reliable results in most cases. For the debottlenecking of HEN, four heuristic rules are proposed to identify the most appropriate heat exchangers requiring heat transfer enhancements in the HEN. The application of this new design approach allows a significant improvement in energy recovery without fundamental structural modifications to the network.

Decay heat removal analyses on the heavy liquid metal cooled fast breeding reactor. Comparisons of the decay heat removal characteristics on lead, lead-bismuth and sodium cooled reactors

International Nuclear Information System (INIS)

Sakai, Takaaki; Ohshima, Hiroyuki; Yamaguchi, Akira

2000-04-01

The feasibility study on several concepts for the commercial fast breeder reactor(FBR) in future has been conducted in JNC for the kinds of possible coolants and fuel types to confirm the direction of the FBR developments in Japan. In this report, Lead and Lead-Bismuth eutectic coolants were estimated for the decay heat removal characteristics by the comparison with sodium coolant that has excellent features for the heat transfer and heat transport performance. Heavy liquid metal coolants, such as Lead and Lead-Bismuth, have desirable chemical inertness for water and atmosphere. Therefore, there are many economical plant proposals without an intermediate heat transport system that prevents the direct effect on a reactor core by the chemical reaction between water and the liquid metal coolant at the hypocritical tube failure accidents in a steam generator. In this study, transient analyses on the thermal-hydraulics have been performed for the decay heat removal events in Equivalent plant' with the Lead, Lead-Bismuth and Sodium coolant by using Super-COPD code. And a resulted optimized lead cooled plant in feasibility study was also analyzed for the comparison. In conclusion, it is become clear that the natural circulation performance, that has an important roll in passive safety characteristic of the reactor, is more excellent in heavy liquid metals than sodium coolant during the decay heat removal transients. However, we need to confirm the heat transfer reduction by the oxidized film or the corrosion products expected to appear on the heat transfer surface in the Lead and Lead-Bismuth circumstance. (author)

Effect of radiant heat transfer on the performance of high temperature heat exchanger

International Nuclear Information System (INIS)

Mori, Yasuo; Hijikata, Kunio; Yamada, Yukio

1975-01-01

The development of high temperature gas-cooled reactors is motivated by the consideration of the application of nuclear heat for industrial uses or direct steelmaking and chemical processes. For these purposes, reliable and efficient heat exchangers should be developed. This report analyzes the effect of radiant heat transfer on the performance of high temperature heat exchangers. The heat transfer model is as follows: the channel composed with two parallel adiabatic walls is divided with one parallel plate between the walls. Non-radiative fluid flows in the two separated channels in opposite direction. Heat transfer equations for this system were obtained, and these equations were solved by some approximate method and numerical analysis. The effect of radiation on heat transfer became larger as the radiant heat transfer between two walls was larger. In the heat exchangers of counter flow type, the thermal efficiency is controlled with three parameters, namely radiation-convection parameter, Stanton number and temperature difference. The thermal efficiency was larger with the increase of these parameters. (Iwase, T.)

Analytical heat transfer

CERN Document Server

Han, Je-Chin

2012-01-01

… it will complete my library … [and] complement the existing literature on heat transfer. It will be of value for both graduate students and faculty members.-Bengt Sunden, Lund University, Sweden

Boiling heat transfer modern developments and advances

CERN Document Server

Lahey, Jr, RT

2013-01-01

This volume covers the modern developments in boiling heat transfer and two-phase flow, and is intended to provide industrial, government and academic researchers with state-of-the-art research findings in the area of multiphase flow and heat transfer technology. Special attention is given to technology transfer, indicating how recent significant results may be used for practical applications. The chapters give detailed technical material that will be useful to engineers and scientists who work in the field of multiphase flow and heat transfer. The authors of all chapters are members of the

The contact heat transfer between the heating plate and granular materials in rotary heat exchanger under overloaded condition

Directory of Open Access Journals (Sweden)

Luanfang Duan

2018-03-01

Full Text Available In the present work, the contact heat transfer between the granular materials and heating plates inside plate rotary heat exchanger (PRHE was investigated. The heat transfer coefficient is dominated by the contact heat transfer coefficient at hot wall surface of the heating plates and the heat penetration inside the solid bed. A plot scale PRHE with a diameter of Do = 273 mm and a length of L = 1000 mm has been established. Quartz sand with dp = 2 mm was employed as the experimental material. The operational parameters were in the range of ω = 1 – 8 rpm, and F = 15, 20, 25, 30%, and the effect of these parameters on the time-average contact heat transfer coefficient was analyzed. The time-average contact heat transfer coefficient increases with the increase of rotary speed, but decreases with the increase of the filling degree. The measured data of time-average heat transfer coefficients were compared with theoretical calculations from Schlünder’s model, a good agreement between the measurements and the model could be achieved, especially at a lower rotary speed and filling degree level. The maximum deviation between the calculated data and the experimental data is approximate 10%. Keywords: Rotary heat exchanger, Contact heat transfer, Granular material, Heating plate, Overloaded

Effects of Liquid Metal Fin on Critical Heat Flux under IVR-ERVC Condition

Energy Technology Data Exchange (ETDEWEB)

Park, Seong Dae; Bang, In Cheol [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of)

2014-05-15

The molten fuel is relocated to bottom of reactor vessel after core is damaged and not cooled continuously. In-vessel retention through external reactor vessel cooling (IVR-ERVC) is presented to terminate the progression of accidents by removing the decay heat. IVR-ERVC is suitable for small size reactors like AR-600, AP-1000. There is uncertainty for high power reactor like APR-1400 and CAP-1400. This uncertainty originates from the thermal margin between the CHF value and real heat flux on the reactor vessel under severe accidents. The main mechanism of heat removal on IVR-ERVC strategy is boiling on the outer wall of reactor vessel. The boiling heat transfer is limited due to the CHF phenomenon. There should be an enough margin for preventing the CHF in boiling heat transfer systems. The CHF tests for IVR-ERVC system were conducted to confirm or increase the thermal margin. The design of thermal insulator was changed to vent the vapor smoothly. Forming the coating layer on the vessel surface was proposed to enhance the CHF margin. The liquid metal was designed to flood the space around the reactor vessel. The liquid metal has high boiling point and superb thermal conductivity in comparison with the coolant. In this work, experimental tests were conducted to validate the CFD results about the IVR-ERVC system with liquid metal. The behavior of vapor was observed to predict the tendency of CHF increase with small-scaled facility to simulate the IVR-ERVC system.

A one-dimensional heat transfer model for parallel-plate thermoacoustic heat exchangers.

Science.gov (United States)

de Jong, J A; Wijnant, Y H; de Boer, A

2014-03-01

A one-dimensional (1D) laminar oscillating flow heat transfer model is derived and applied to parallel-plate thermoacoustic heat exchangers. The model can be used to estimate the heat transfer from the solid wall to the acoustic medium, which is required for the heat input/output of thermoacoustic systems. The model is implementable in existing (quasi-)1D thermoacoustic codes, such as DeltaEC. Examples of generated results show good agreement with literature results. The model allows for arbitrary wave phasing; however, it is shown that the wave phasing does not significantly influence the heat transfer.

Heat transfer and critical heat flux in a spiral flow in an asymmetrical heated tube

International Nuclear Information System (INIS)

Boscary, J.; Association Euratom-CEA, Centre d'Etudes Nucleaires de Cadarache, 13 - Saint-Paul-lez-Durance

1997-03-01

The design of plasma facing components is crucial for plasma performance in next fusion reactors. These elements will be submitted to very high heat flux. They will be actively water-cooled by swirl tubes in the subcooled boiling regime. High heat flux experiments were conducted in order to analyse the heat transfer and to evaluate the critical heat flux. Water-cooled mock-ups were one-side heated by an electron beam gun for different thermal-hydraulic conditions. The critical heat flux was detected by an original method based on the isotherm modification on the heated surface. The wall heat transfer law including forced convection and subcooled boiling regimes was established. Numerical calculations of the material heat transfer conduction allowed the non-homogeneous distribution of the wall temperature and of the wall heat flux to be evaluated. The critical heat flux value was defined as the wall maximum heat flux. A critical heat flux model based on the liquid sublayer dryout under a vapor blanket was established. A good agreement with test results was found. (author)

The log mean heat transfer rate method of heat exchanger considering the influence of heat radiation

International Nuclear Information System (INIS)

Wong, K.-L.; Ke, M.-T.; Ku, S.-S.

2009-01-01

The log mean temperature difference (LMTD) method is conventionally used to calculate the total heat transfer rate of heat exchangers. Because the heat radiation equation contains the 4th order exponential of temperature which is very complicate in calculations, thus LMTD method neglects the influence of heat radiation. From the recent investigation of a circular duct in some practical situations, it is found that even in the situation of the temperature difference between outer duct surface and surrounding is low to 1 deg. C, the heat radiation effect can not be ignored in the situations of lower ambient convective heat coefficient and greater surface emissivities. In this investigation, the log mean heat transfer rate (LMHTR) method which considering the influence of heat radiation, is developed to calculate the total heat transfer rate of heat exchangers.

Numerical study on heat transfer characteristics of thermosyphon heat pipes using nanofluids

International Nuclear Information System (INIS)

Huminic, Gabriela; Huminic, Angel

2013-01-01

Highlights: • Numerical study of nanofluid heat transfer in thermosyphon heat pipes is performed. • Effect of nanoparticle concentration and operating temperature are studied. • Fe 2 O 3 –water nanofluid with 5.3% volume concentration shows the best performance. • Results show the improvement the thermal performances of thermosyphon heat pipe with nanofluids. - Abstract: In this work, a three-dimensional analysis is used to investigate the heat transfer of thermosyphon heat pipe using water and nanofluids as the working fluid. The study focused mainly on the effects of volume concentrations of nanoparticles and the operating temperature on the heat transfer performance of the thermosyphon heat pipe using the nanofluids. The analysis was performed for water and γ-Fe 2 O 3 nanoparticles, three volume concentrations of nanoparticles (0 vol.%, 2 vol.% and 5.3 vol.%) and four operating temperatures (60, 70, 80 and 90 °C). The numerical results show that the volume concentration of nanoparticles had a significant effect in reducing the temperature difference between the evaporator and condenser. Experimental and numerical results show qualitatively that the thermosyphon heat pipe using the nanofluid has better heat transfer characteristics than the thermosyphon heat pipe using water

Influence of water–air ratio on the heat transfer and creep life of a high pressure gas turbine blade

International Nuclear Information System (INIS)

Eshati, S.; Abu, A.; Laskaridis, P.; Khan, F.

2013-01-01

An analytical model to investigate the influence of Water–Air Ratio (WAR) on turbine blade heat transfer and cooling processes (and thus the blade creep life) of industrial gas turbines is presented. The effects of WAR are emphasised for the modelling of the gas properties and the subsequent heat transfer process. The approach considers convective/film cooling and includes the influence of a thermal barrier coating. In addition, the approach is based on the thermodynamic outputs of a gas turbine performance simulation, heat transfer model, as well as a method that accounts for the changes in the properties of moist air as a function of WAR. For a given off-design point, the variation of WAR (0.0–0.10) was investigated using the heat transfer model. Results showed that with increasing WAR the blade inlet coolant temperature reduced along the blade span. The blade metal temperature at each section was reduced as WAR increased, which in turn increased the blade creep life. The increase in WAR increased the specific heat of the coolant and increased the heat transfer capacity of the coolant air flow. The model can be implemented by using the thermodynamic cycle of the engine, without knowing the turbine cooling details in the conceptual design stage. Also, this generic method assists the end user to understand the effect of operating conditions and design parameter on the creep life of a high pressure turbine blade. -- Highlights: • The influence of WAR on gas turbine blade heat transfer and creep life is examined. • Coolant specific heat capacity is the key property affected by changes in WAR. • Increase in WAR reduces the coolant and metal temperature along the blade span. • Creep life increases with increase in WAR even if ambient temperature is increased

Convective heat transfer enhancement using Carbon nanofibers (CNFs): influence of amorphous carbon layer on heat transfer performance

NARCIS (Netherlands)

Taha, T.J.; Lefferts, Leonardus; van der Meer, Theodorus H.

2013-01-01

In this work, an experimental heat transfer investigation was carried out to investigate the combined influence of both amorphous carbon (a-C) layer thickness and carbon nanofibers (CNFs) on the convective heat transfer behavior. Synthesis of these carbon nano structures was achieved using catalytic

HEAT TRANSFER METHOD

Science.gov (United States)

Gambill, W.R.; Greene, N.D.

1960-08-30

A method is given for increasing burn-out heat fluxes under nucleate boiling conditions in heat exchanger tubes without incurring an increase in pumping power requirements. This increase is achieved by utilizing a spinning flow having a rotational velocity sufficient to produce a centrifugal acceleration of at least 10,000 g at the tube wall. At this acceleration the heat-transfer rate at burn out is nearly twice the rate which can be achieved in a similar tube utilizing axial flow at the same pumping power. At higher accelerations the improvement over axial flow is greater, and heat fluxes in excess of 50 x 10/sup 6/ Btu/hr/sq ft can be achieved.

Heat transport and surface heat transfer with helium in rotating channels

International Nuclear Information System (INIS)

Schnapper, C.

1978-06-01

Heat transport and surface heat transfer with helium in rotating radially arranged channels were experimentally studied with regard to cooling of large turbogenerators with superconducting windings. Measurements with thermosiphon and thermosiphon loops of different channel diameters were performed, and results are presented. The thermodynamic state of the helium in a rotating thermosiphon and the mass flow rate in a thermosiphon loop is characterized by formulas. Heat transport by directed convection in thermosiphon loops is found to be more efficient 12 cm internal convection in thermosiphons. Steady state is reached sooner in thermosiphon loops than in thermosiphons, when heat load suddenly changes. In a very large centrifugal field single-phase heat transfer with natural and forced convection is described by similar formulas which are also applicable 10 thermosiphons in gravitation field or to heat transfer to non-rotating helium. (orig.) [de

Evaluation of empirical heat transfer models using TFG heat flux sensors

International Nuclear Information System (INIS)

De Cuyper, T.; Broekaert, S.; Chana, K.; De Paepe, M.; Verhelst, S.

2017-01-01

Thermodynamic engine cycle models are used to support the development of the internal combustion engine (ICE) in a cost and time effective manner. The sub model which describes the in-cylinder heat transfer from the working gases to the combustion chamber walls plays an important role in the accuracy of these simulation tools. The heat transfer affects the power output, engine efficiency and emissions of the engine. The most common heat transfer models in engine research are the models of Annand and Woschni. These models provide an instantaneous spatial averaged heat flux. In this research, prototype thin film gauge (TFG) heat flux sensors are used to capture the transient in-cylinder heat flux behavior within a production spark ignition (SI) engine as they are small, robust and able to capture the highly transient temperature swings. An inlet valve and two different zones of the cylinder head are instrumented with multiple TFG sensors. The heat flux traces are used to calculate the convection coefficient which includes all information of the convective heat transfer phenomena inside the combustion chamber. The implementation of TFG sensors inside the combustion chamber and the signal processing technique are discussed. The heat transfer measurements are used to analyze the spatial variation in heat flux under motored and fired operation. Spatial variation in peak heat flux was observed even under motored operation. Under fired operation the observed spatial variation is mainly driven by the flame propagation. Next, the paper evaluates the models of Annand and Woschni. These models fail to predict the total heat loss even with calibration of the models coefficients using a reference motored operating condition. The effect of engine speed and inlet pressure is analyzed under motored operation after calibration of the models. The models are able to predict the trend in peak heat flux value for a varying engine speed and inlet pressure. Next, the accuracy of the

Evaluation of heat transfer enhancement in air-heating collectors

Energy Technology Data Exchange (ETDEWEB)

Mattox, D. L.

1979-06-01

The present research effort was initiated for the purpose of increasing the thermal efficiency of air heating solar collectors through identification and development of optimum design and operation criteria for solar absorber-to-air heat exchangers. Initially this effort took the form of a solar collector systems analysis to evaluate the impact of various techniques for enhancing the heat transfer between the absorber and air stream on overall thermal performance of the entire solar collector. This systems analysis resulted in the selection of solar collector designs providing ducted cooling air on the absorber shaded side as a base line. A transient heat transfer analysis of a complete solar air heating collector was used to demonstrate that an optimum absorber-to-air heat exchanger design could be provided with several interrupted fin configurations. Additional analyses were performed to establish that the maximum solar collector thermal performance to required pumping power was realized for a Reynolds number range of 1000 to 2000. This Reynolds number range was used to establish a theoretical design limit curve for maximum thermal performance versus required pumping power for all interrupted fin designs as published in the open literature. Heat and momentum transfer empirical relationships were defined for scaling the state-of-the-art high conductance fin designs identified from a compact configuration to the less compact designs needed for solar collectors.

Heat transfer from humans wearing clothing

NARCIS (Netherlands)

Lotens, W.A.

1993-01-01

In this monograph the effects of clothing on human heat transfer are described. The description is based on the physics of heat and mass transfer, depending on the design of the clothing, the climate, and the activity of the wearer. The resulting model has been stepwise implemented in computer

An introduction to heat transfer principles and calculations

CERN Document Server

Ede, A J; Ower, E

1967-01-01

An Introduction to Heat Transfer Principles and Calculations is an introductory text to the principles and calculations of heat transfer. The theory underlying heat transfer is described, and the principal results and formulae are presented. Available techniques for obtaining rapid, approximate solutions to complicated problems are also considered. This book is comprised of 12 chapters and begins with a brief account of some of the concepts, methods, nomenclature, and other relevant information about heat transfer. The reader is then introduced to radiation, conduction, convection, and boiling

ANL ITER high-heat-flux blanket-module heat transfer experiments

International Nuclear Information System (INIS)

Kasza, K.E.

1992-02-01

An Argonne National Laboratory facility for conducting tests on multilayered slab models of fusion blanket designs is being developed; some of its features are described. This facility will allow testing under prototypic high heat fluxes, high temperatures, thermal gradients, and variable mechanical loadings in a helium gas environment. Steady and transient heat flux tests are possible. Electrical heating by a two-sided, thin stainless steel (SS) plate electrical resistance heater and SS water-cooled cold panels placed symmetrically on both sides of the heater allow achievement of global one-dimensional heat transfer across blanket specimen layers sandwiched between the hot and cold plates. The heat transfer characteristics at interfaces, as well as macroscale and microscale thermomechanical interactions between layers, can be studied in support of the ITER engineering design effort. The engineering design of the test apparatus has shown that it is important to use multidimensional thermomechanical analysis of sandwich-type composites to adequately analyze heat transfer. This fact will also be true for the engineering design of ITER

Heat transfer performance of heat pipe for passive cooling of spent fuel pool

International Nuclear Information System (INIS)

Wang Minglu; Xiong Zhengqin; Gu Hanyang; Ye Cheng; Cheng Xu

2014-01-01

A large-scale loop heat pipe has no electricity driven component and high efficiency of heat transfer. It can be used for the passive cooling of the SFP after SBO to improve the safety performance of nuclear power plants. In this paper, such a large-scale loop heat pipe is studied experimentally. The heat transfer rate, evaporator average heat transfer coefficient operating temperature, operating pressure and ammonia flow rate have been obtained with the water flow ranging from 0.007 m/s to 0.02 m/s outside the evaporator section, heating water temperature in the range of 50 to 90℃, air velocity outside the condensation section ranging from 0.5 to 2.5 m/s. It is found that the heat transfer rate reaches as high as 20.1 kW. Parametric analysis indicates that, the heat transfer rate and ammonia flow rate are influenced significantly by hot water inlet temperature and velocity, while beyond 1.5 m/s, the effect of air velocity outside the condensation section is minor. (authors)

Transient heat transfer characteristics of liquid helium

International Nuclear Information System (INIS)

Tsukamoto, Osami

1976-01-01

The transient heat transfer characteristics of liquid helium are investigated. The critical burnout heat fluxes for pulsive heating are measured, and empirical relations between the critical burnout heat flux and the length of the heat pulse are given. The burnout is detected by observing the super-to-normal transition of the temperature sensor which is a thin lead film prepared on the heated surface by vacuum evaporation. The mechanism of boiling heat transfer for pulsive heating is discussed, and theoretical relations between the critical burnout heat flux and the length of the heat pulse are derived. The empirical data satisfy the theoretical relations fairly well. (auth.)

Overall conductance and heat transfer area minimization of refrigerators and heat pumps with finite heat reservoirs

International Nuclear Information System (INIS)

Sarkar, J.; Bhattacharyya, Souvik

2007-01-01

In the present study, the overall conductance and the overall heat transfer area per unit capacity of refrigeration and heat pump systems have been minimized analytically considering both internal and external irreversibilities with variable temperature (finite capacity) heat reservoirs. Hot and cold side refrigerant temperatures, conductance and heat transfer area ratios have been optimized to attain this goal. The results have been verified with the more elaborate numerical optimization results obtained for ammonia based vapour compression refrigeration and heat pump systems working with variable temperature reservoirs. It is observed that the analytical results for optimum refrigerant temperatures, minimum overall conductance and heat transfer area deviate marginally from the numerically optimized results (within 1%), if one assumes a constant heat rejection temperature. The deviation of minimum overall conductance and heat transfer area is more (about 20%), if one considers both the desuperheating and condensation regions separately. However, in the absence of complex and elaborate numerical models, the simple analytical results obtained here can be used as reasonably accurate preliminary guidelines for optimization of refrigeration and heat pump systems

Turbulent heat transfer for heating of water in a short vertical tube

International Nuclear Information System (INIS)

Hata, Koichi; Noda, Nobuaki

2008-01-01

The turbulent heat transfer coefficients for the flow velocities (u=4.0 to 21 m/s), the inlet liquid temperatures (T in =296.5 to 353.4 K), the inlet pressures (P in =810 to 1014 kPa) and the increasing heat inputs (Q 0 exp(t/τ), τ=10, 20 and 33.3 s) are systematically measured by an experimental water loop. The Platinum test tubes of test tube inner diameters (d=3, 6 and 9 mm), heated lengths (L=32.7 to 100 mm), ratios of heated length to inner diameter (L/d=5.51 to 33.3) and wall thickness (δ=0.3, 0.4 and 0.5 mm) with surface roughness (Ra=0.40 to 0.78 μm) are used in this work. The turbulent heat transfer data for Platinum test tubes were compared with the values calculated by other workers' correlations for the turbulent heat transfer. The influence of Reynolds number (Re), Prandtl number (Pr), Dynamic viscosity (μ) and L/d on the turbulent heat transfer is investigated into details and, the widely and precisely predictable correlation of the turbulent heat transfer for heating of water in a short vertical tube is given based on the experimental data. The correlation can describe the turbulent heat transfer coefficients obtained in this work for the wide range of the temperature difference between heater inner surface temperature and average bulk liquid temperature (ΔT L =5 to 140 K) with d=3, 6 and 9 mm, L=32.7 to 100 mm and u=4.0 to 21 m/s within ±15%, difference. (author)

Turbulent heat transfer for heating of water in a short vertical tube

International Nuclear Information System (INIS)

Hata, Koichi; Noda, Nobuaki

2007-01-01

The turbulent heat transfer coefficients for the flow velocities (u=4.0 to 21 m/s), the inlet liquid temperatures (T in =296.5 to 353.4 K), the inlet pressures (P in =810 to 1014 kPa) and the increasing heat inputs (Q 0 exp(t/τ), τ=10, 20 and 33.3 s) are systematically measured by the experimental water loop. The Platinum test tubes of test tube inner diameters (d=3, 6 and 9 mm), heated lengths (L=32.7 to 100 mm), ratios of heated length to inner diameter (L/d=5.51 to 33.3) and wall thicknesses (δ=0.3, 0.4 and 0.5 mm) with surface roughness (Ra=0.40 to 0.78 μm) are used in this work. The turbulent heat transfer data for Platinum test tubes were compared with the values calculated by other workers' correlations for the turbulent heat transfer. The influences of Reynolds number (Re), Prandtl number (Pr), Dynamic viscosity (μ) and L/d on the turbulent heat transfer are investigated into details and, the widely and precisely predictable correlation of the turbulent heat transfer for heating of water in a short vertical tube is given based on the experimental data. The correlation can describe the turbulent heat transfer coefficients obtained in this work for wide range of the temperature difference between heater inner surface temperature and average bulk liquid temperature (ΔT L =5 to 140 K) with d=3, 6 and 9 mm, L=32.7 to 100 mm and u=4.0 to 21 m/s within ±15% difference. (author)

Loop heat pipes - highly efficient heat-transfer devices for systems of sun heat supply

Energy Technology Data Exchange (ETDEWEB)

Maydanik, Yu. [Ural Branch of the Russian Academy of Sciences, Ekaterinburg (Russian Federation). Inst. of Thermophysics

2004-07-01

Loop heat pipes (LHPs) are hermetic heat-transfer devices operating on a closed evaporation-condensation cycle with the use of capillary pressure for pumping the working fluid [1]. In accordance with this, they possess all the main advantages of conventional heat pipes, but, as distinct from the latter, have a considerably higher heat-transfer capacity, especially when operating in the ''antigravity'' regime, when heat is transferred from above downwards. Besides, LHPs possess a higher functional versatility, are adaptable to different operating conditions and provide great scope for various design embodiments. This is achieved at the expense of both the original design of the device and the properties of the wick - a special capillary structure used for the creation of capillary pressure. The LHP schematic diagram is given in Fig. 1. The device contains an evaporator and a condenser - heat exchanger connected by means of smooth-walled pipe-lines with a relatively small diameter intended for separate motion of vapor and liquid. At present loop heat pipes are most extensively employed in thermoregulation systems of spacecrafts. Miniature LHPs are used for cooling electronics and computers. At the same time there exists a considerable potential of using these devices for the recovery of low-grade (waste) heat from different sources, and also in systems of sun heat supply. In the latter case LHPs may serve as an efficient heat-transfer link between a sun collector and a heat accumulator, which has a low thermal resistance and does not consume any additional energy for pumping the working fluid between them. (orig.)

Heat transfer enhancement in cross-flow heat exchanger using vortex generator

International Nuclear Information System (INIS)

Yoo, S. Y.; Kwon, H. K.; Kim, B. C.; Park, D. S.; Lee, S. S.

2003-01-01

Fouling is very serious problem in heat exchanger because it rapidly deteriorates the performance of heat exchanger. Cross-flow heat exchanger with vortex generators is developed, which enhance heat transfer and reduce fouling. In the present heat exchanger, shell and baffle are removed from the conventional shell-and-tube heat exchanger. The naphthalene sublimation technique is employed to measure the local heat transfer coefficients. The experiments are performed for single circular tube, staggered array tube bank and in-line array tube bank with and without vortex generators. Local and average Nusselt numbers of single tube and tube bank with vortex generator are investigated and compared to those of without vortex generator

Influence of short heat pulses on the helium boiling heat transfer rate

International Nuclear Information System (INIS)

Andreev, V.K.; Deev, V.I.; Savin, A.N.; Kutsenko, K.V.

1987-01-01

Investigation results on heat transfer in the process of helium boiling on a heated wall under conditions of pulsed heat effect are described. Results of the given study point to one of possible ways of heat exchange intensification in boiling helium by supplying short heat pulse to the heater. Even short-time noncontrolled or incidental increase in the heater capacity during experiment with boiling helium can result in a considerable disagreement of experimental data on heat transfer

Natural convection heat transfer of fluid with temperature-dependent specific heat

International Nuclear Information System (INIS)

Tanaka, Amane; Kubo, Shinji; Akino, Norio

1998-01-01

The present study investigates natural convection from a heated vertical plate of fluid with temperature-dependent specific heat, which is introduced as a model of microencapsulated phase change material slurries (MCPCM slurries). The temperature dependence of specific heat is represented by Gauss function with three physical parameters (peak temperature, width of phase change temperature and latent heat). Boundary layer equations are solved numerically, and the velocity and temperature fields of the flow are obtained. The relation between the heat transfer coefficients and the physical parameters of specific heat is discussed. The results show that the velocities and temperatures are smaller, and the heat transfer coefficients are larger comparing with those of the fluid with constant specific heat. (author)

Evaluation of Heat Transfer to the Implant-Bone Interface During Removal of Metal Copings Cemented onto Titanium Abutments.

Science.gov (United States)

Cakan, Umut; Cakan, Murat; Delilbasi, Cagri

2016-01-01

The aim of this investigation was to measure the temperature increase due to heat transferred to the implant-bone interface when the abutment screw channel is accessed or a metal-ceramic crown is sectioned buccally with diamond or tungsten carbide bur using an air rotor, with or without irrigation. Cobalt-chromium copings were cemented onto straight titanium abutments. The temperature changes during removal of the copings were recorded over a period of 1 minute. The sectioning of coping with diamond bur and without water irrigation generated the highest temperature change at the cervical part of the implant. Both crown removal methods resulted in an increase in temperature at the implant-bone interface. However, this temperature change did not exceed 47°C, the potentially damaging threshold for bone reported in the literature.

Proceedings of the twenty third national heat and mass transfer conference and first international ISHMT-ASTFE heat and mass transfer conference: souvenir and book of abstracts

International Nuclear Information System (INIS)

2015-01-01

The conference covered various aspects of heat and mass transfer like Aero-thermodynamics, Atmospheric flows, Biological heat and mass transfer, Combustion and reactive flows, Cryogenics, Electronic and photonic cooling, Energy engineering, Environmental engineering, Experimental techniques, Heat transfer enhancement, Heat transfer equipment's, Heat transfer in nuclear applications, Mass transfer, Materials processing and manufacturing, Microscale and nanoscale transport, Multiphase transport and phase change, Multi mode heat transfer, Numerical methods, Refrigeration and air conditioning, Space heat transfer, Transport phenomena in porous media, and Turbulent transport. Papers relevant to INIS are indexed separately

Introduction to heat transfer

International Nuclear Information System (INIS)

Weisman, J.

1983-01-01

Heat may be defined as that form of energy which spontaneously flows between two bodies, or two regions of a body, by virtue of a temperature difference. The second law of thermodynamics tells us that we cannot have heat flow from a low temperature to high temperature without doing work. Heat flows spontaneously from a high temperature to a low temperature region. Thermodynamics, which is concerned with equilibrium states, cannot tell us anything about the rate of heat flow in the presence of a finite temperature difference. It is to the discipline of heat transfer to which we must turn for this answer

Heat Transfer and Entropy Generation Analysis of an Intermediate Heat Exchanger in ADS

Science.gov (United States)

Wang, Yongwei; Huai, Xiulan

2018-04-01

The intermediate heat exchanger for enhancement heat transfer is the important equipment in the usage of nuclear energy. In the present work, heat transfer and entropy generation of an intermediate heat exchanger (IHX) in the accelerator driven subcritical system (ADS) are investigated experimentally. The variation of entropy generation number with performance parameters of the IHX is analyzed, and effects of inlet conditions of the IHX on entropy generation number and heat transfer are discussed. Compared with the results at two working conditions of the constant mass flow rates of liquid lead-bismuth eutectic (LBE) and helium gas, the total pumping power all tends to reduce with the decreasing entropy generation number, but the variations of the effectiveness, number of transfer units and thermal capacity rate ratio are inconsistent, and need to analyze respectively. With the increasing inlet mass flow rate or LBE inlet temperature, the entropy generation number increases and the heat transfer is enhanced, while the opposite trend occurs with the increasing helium gas inlet temperature. The further study is necessary for obtaining the optimized operation parameters of the IHX to minimize entropy generation and enhance heat transfer.

Heat Transfer and Pressure Drop Characteristics in Straight Microchannel of Printed Circuit Heat Exchangers

Directory of Open Access Journals (Sweden)

Jang-Won Seo

2015-05-01

Full Text Available Performance tests were carried out for a microchannel printed circuit heat exchanger (PCHE, which was fabricated with micro photo-etching and diffusion bonding technologies. The microchannel PCHE was tested for Reynolds numbers in the range of 100‒850 varying the hot-side inlet temperature between 40 °C–50 °C while keeping the cold-side temperature fixed at 20 °C. It was found that the average heat transfer rate and heat transfer performance of the countercurrrent configuration were 6.8% and 10%‒15% higher, respectively, than those of the parallel flow. The average heat transfer rate, heat transfer performance and pressure drop increased with increasing Reynolds number in all experiments. Increasing inlet temperature did not affect the heat transfer performance while it slightly decreased the pressure drop in the experimental range considered. Empirical correlations have been developed for the heat transfer coefficient and pressure drop factor as functions of the Reynolds number.

Enhancing heat transfer in microchannel heat sinks using converging flow passages

International Nuclear Information System (INIS)

Dehghan, Maziar; Daneshipour, Mahdi; Valipour, Mohammad Sadegh; Rafee, Roohollah; Saedodin, Seyfolah

2015-01-01

Highlights: • The fluid flow and conjugate heat transfer in microchannel heat sinks are studied. • The Poiseuille and Nusselt numbers are presented for width-tapered MCHS. • Converging walls are found to enhance the thermal performance of MCHS. • The optimum performance of MCHS for fixed inlet and outlet pressures is discussed. • For the optimum configuration, the pumping power is reduced up to 75%. - Abstract: Constrained fluid flow and conjugate heat transfer in microchannel heat sinks (MCHS) with converging channels are investigated using the finite volume method (FVM) in the laminar regime. The maximum pressure of the MCHS loop is assumed to be limited due to constructional or operational conditions. Results show that the Poiseuille number increases with increased tapering, while the required pumping power decreases. Meanwhile, the Nusselt number increases with tapering as well as the convection heat transfer coefficient. The MCHS having the optimum heat transfer performance is found to have a width-tapered ratio equal to 0.5. For this tapering configuration and at the maximum pressure constraint of 3000 Pa, the pumping power reduces by a factor of 4 while the overall heat removal rate is kept fixed in comparison with a straight channel

Numerical simulation of shell-side heat transfer and flow of natural circulation heat exchanger

International Nuclear Information System (INIS)

Xue Ruojun; Deng Chengcheng; Li Chaojun; Wang Mingyuan

2012-01-01

In order to analyze the influence on the heat transfer and flow characteristics of the heat exchanger model of different solving models and structures, a variety of transformation to the model equivalent for the heat exchanger was studied. In this paper, Fluent software was used to simulate the temperature-field and flow-field of the equivalent model, and investigate its heat-transferring and flow characteristics. Through comparative analysis of the distribution of temperature-field and flow-field for different models, the heat-transferring process and natural convection situation of heat exchanger were deeply understood. The results show that the temperature difference between the inside and outside of the natural circulation heat exchanger tubes is larger and the flow is more complex, so the turbulence model is the more reasonable choice. Asymmetry of tubes position makes the flow and heat transfer of the fluid on both sides to be dissymmetrical and makes the fluid interaction, and increases the role of natural convection. The complex structure of heat exchanger makes the flow and heat transfer of the fluid on both sides to be irregular to some extent when straight tubes into C-bent are transformed, and all these make the turbulence intensity increase and improve the effect of heat transfer. (authors)

Heat transfer from rotating finned heat exchangers with different orientation angles

Energy Technology Data Exchange (ETDEWEB)

Tawfik, Adel Abdalla [Suez Canal University, Marine Engineering and Naval Architecture Department, Faculty of Engineering, Port Said (Egypt)

2010-03-15

The local and average heat transfer characteristics of spoke like fins that extend outward from a rotating shaft have been determined experimentally. The experiments encompassed a number of geometrical parameters, including the length and chord of the fins, the number of fins deployed around the circumference of the shaft and the orientation angles of the fin. The experiments cover a wider range of rotational speeds, which varies from 25 up to 2,000 rpm. Three wire heat flux sensors have been used in conjunction with a slip ring apparatus to evaluate the local and average heat transfer coefficients. The output results indicated that, the heat transfer transition on rotating fins occurs at Reynolds number lower than encountered on the stationary rectangular fins in crossflow. In general, with non zero incidence angle, the rotating system acts as a fan and creates axial air motion, which enhance the heat transfer rate. However, the effect of orientation angle reduces with increasing the rotational speed. The Nusselt number data are independent of the number of fins in the circumferential array at high rotational speed and are weakly dependent at low Reynolds numbers. To facilitate the use of the results for design, correlations were developed which represent the fin heat transfer coefficient as a continuous function of the investigated independent parameters. (orig.)

On the heat transfer in packed beds

International Nuclear Information System (INIS)

Sordon, G.

1988-09-01

The design of a fusion reactor blanket concept based on a bed of lithium containing ceramic pebbles or a mixture of ceramic and beryllium pebbles demands the knowledge of the effective thermal conductivity of pebble beds, including beds formed by a binary mixture of high conducting metallic pebbles and poorly conducting pebbles. In this work, binary mixtures of spheres of same diameter and different conductivities as well as beds formed by one type of spheres were investigated. The experimental apparatus consists of a stainless steel cylinder with a heating rod along the symmetry axis. Experiments with stagnant and flowing gas were performed. The pebbles were of Al 2 O 3 (diameter = 1, 2, 4 mm), of Li 4 SO 4 (diameter = 0.5 mm) of Al (diameter = 2 mm) and of steel (diameter = 2, 4 mm). Experimental values of the thermal conductivity and of the wall heat transfer coefficient are compared with the predicted ones. Modifications of already existing models were suggested. (orig.) [de

Oxidation and metal-insertion in molybdenite surfaces: evaluation of charge-transfer mechanisms and dynamics

Directory of Open Access Journals (Sweden)

Shutthanandan V

2008-06-01

Full Text Available Abstract Molybdenum disulfide (MoS2, a layered transition-metal dichalcogenide, has been of special importance to the research community of geochemistry, materials and environmental chemistry, and geotechnical engineering. Understanding the oxidation behavior and charge-transfer mechanisms in MoS2 is important to gain better insight into the degradation of this mineral in the environment. In addition, understanding the insertion of metals into molybdenite and evaluation of charge-transfer mechanism and dynamics is important to utilize these minerals in technological applications. Furthermore, a detailed investigation of thermal oxidation behavior and metal-insertion will provide a basis to further explore and model the mechanism of adsorption of metal ions onto geomedia. The present work was performed to understand thermal oxidation and metal-insertion processes of molybdenite surfaces. The analysis was performed using atomic force microscopy (AFM, scanning electron microscopy (SEM, transmission electron microscopy (TEM, Rutherford backscattering spectrometry (RBS, and nuclear reaction analysis (NRA. Structural studies using SEM and TEM indicate the local-disordering of the structure as a result of charge-transfer process between the inserted lithium and the molybdenite layer. Selected area electron diffraction measurements indicate the large variations in the diffusivity of lithium confirming that the charge-transfer is different along and perpendicular to the layers in molybdenite. Thermal heating of molybenite surface in air at 400°C induces surface oxidation, which is slow during the first hour of heating and then increases significantly. The SEM results indicate that the crystals formed on the molybdenite surface as a result of thermal oxidation exhibit regular thin-elongated shape. The average size and density of the crystals on the surface is dependent on the time of annealing; smaller size and high density during the first one-hour and

Oxidation and metal-insertion in molybdenite surfaces: evaluation of charge-transfer mechanisms and dynamics.

Science.gov (United States)

Ramana, C V; Becker, U; Shutthanandan, V; Julien, C M

2008-06-05

Molybdenum disulfide (MoS2), a layered transition-metal dichalcogenide, has been of special importance to the research community of geochemistry, materials and environmental chemistry, and geotechnical engineering. Understanding the oxidation behavior and charge-transfer mechanisms in MoS2 is important to gain better insight into the degradation of this mineral in the environment. In addition, understanding the insertion of metals into molybdenite and evaluation of charge-transfer mechanism and dynamics is important to utilize these minerals in technological applications. Furthermore, a detailed investigation of thermal oxidation behavior and metal-insertion will provide a basis to further explore and model the mechanism of adsorption of metal ions onto geomedia.The present work was performed to understand thermal oxidation and metal-insertion processes of molybdenite surfaces. The analysis was performed using atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Rutherford backscattering spectrometry (RBS), and nuclear reaction analysis (NRA).Structural studies using SEM and TEM indicate the local-disordering of the structure as a result of charge-transfer process between the inserted lithium and the molybdenite layer. Selected area electron diffraction measurements indicate the large variations in the diffusivity of lithium confirming that the charge-transfer is different along and perpendicular to the layers in molybdenite. Thermal heating of molybenite surface in air at 400 degrees C induces surface oxidation, which is slow during the first hour of heating and then increases significantly. The SEM results indicate that the crystals formed on the molybdenite surface as a result of thermal oxidation exhibit regular thin-elongated shape. The average size and density of the crystals on the surface is dependent on the time of annealing; smaller size and high density during the first one-hour and significant

Review of the critical heat flux correlations for liquid metals

International Nuclear Information System (INIS)

Lee, Yong Bum; Han, H. D.; Chang, W. P.; Kwon, Y. M.

1999-09-01

The CHF phenomenon in the two-phase convective flows has been an important issue in the fields of design and safety analysis of light water reactor (LWR) as well as sodium cooled liquid metal reactor (LMR). Especially in the LWR application, many physical aspects of the CHF phenomenon are understood and reliable correlations and mechanistic models to predict the CHF condition have been proposed over the past three decades. Most of the existing CHF correlations have been developed for light water reactor core applications. Compared with water, liquid metals show a divergent picture of boiling pattern. This can be attributed to the consequence that special CHF conditions obtained from investigations with water cannot be applied to liquid metals. Numerous liquid metal boiling heat transfer and two-phase flow studies have put emphasis on development of models and understanding of the mechanism for improving the CHF predictions. Thus far, no overall analytical solution method has been obtained and the reliable prediction method has remained empirical. The principal objectives of the present report are to review the state of the art in connection with liquid metal critical heat flux under low pressure and low flow conditions and to discuss the basic mechanisms. (author)

Experimental and numerical investigation on heat transfer augmentation in a circular tube under forced convection with annular differential blockages/inserts

Science.gov (United States)

Waghole, D. R.

2018-01-01

Investigation on heat transfer by generating turbulence in the fluid stream inside the circular tube is an innovative area of research for researchers. Hence, many techniques are been investigated and adopted for enhancement of heat transfer rate to reduce the size and the cost of the heat exchanger/circular tube. In the present study the effect of differential solid ring inserts /turbulators on heat transfer, friction factor of heat exchanger/circular tube was evaluated through experimentally and numerically. The experiments were conducted in range of 3000 ≤Re≤ 6500 and annular blockages 0 ≤ɸ≤50 %. The heat transfer rate was higher for differential combination of inserts as compared to tube fitted with uniform inserts. The maximum heat transfer was obtained by the use of differential metal circular ring inserts/blockages. From this study, Nusselt number, friction factor and enhancement factor are found as 2.5-3.5 times, 12% - 50.5% and 155% - 195%, respectively with water. Finally new possible correlations for predicting heat transfer and friction factor in the flow of water through the circular tube with differential blockages/inserts are proposed.

Heat transfer coefficient for flow boiling in an annular mini gap

Directory of Open Access Journals (Sweden)

Hożejowska Sylwia

2016-01-01