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Simulation approaches for nano-scale semiconductor devices

Science.gov (United States)

... turbine blade heat-transfer and study the heat-transfer augmentation in idealized geometry and its ... responsible for heat transfer augmentation. ...

Science.gov (United States)

... To maximise heat transfer rates, many heatshield designs make use of heat transfer augmentation devices such as large numbers of pin-fin ...

Energy Technology Data Exchange (ETDEWEB)

The possibility of switching the heat transfer consists of varying heat transfer surfaces and making the heat transfer temporarily more intensive. Heat tubes prove to be particularly suitable, which must be exposed to a heat carrier fluid or removed from its effect for switching the heat transfer. This report gives a survey of the possibilities of switching heat flows and for making the heat transfer more intensive. Further, the report contains a survey of patents limited to heat transfer in the fields of cooling internal combustion engines and exhaust systems. (orig.) With 17 figs., 183 refs.

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Energy Technology Data Exchange (ETDEWEB)

This book contains nine selections. Some of the titles are: High Heat-Flux, Forced-Convection Heat Transfer for Tubes with Twisted-Tape Inserts; Heat Transfer Augmentation by Interrupted Surfaces - Experimental Consideration; Turbulent Flow Heat Transfer from Externally Roughened Tubes in Axial Flow in Concentric Pipe Heat Exchangers; and Heat Transfer Enhancement of Turbulent Flow in Pipes with an Internal Circular Rib.

International Nuclear Information System (INIS)

This paper deals with construction types of high temperature heat exchangers, their circulation loops and temperature differences. Most attention is given to gas dynamics, convective heat transfer, convection and radiant heat transfer interaction in high temperature heat exchangers. The ways of heat transfer augmentation and efficient heat exchanger construction are discussed.

Science.gov (United States)

A compact heat exchanger pedestal array for augmenting heat transfer in a machine is disclosed. The compact heat exchanger pedestal array includes a wall having first and second surfaces. The first surface faces a heated flow path and the second surface p...

International Nuclear Information System (INIS)

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 ...

Science.gov (United States)

This dissertation presents the development of the novel mechanical testing technique of in situ nanoindentation in a transmission electron microscope (TEM). This technique makes it possible to simultaneously observe and quantify the mechanical behavior of nano-scale volumes of solids.

Science.gov (United States)

... mass of gray gas by thermal radiation; An experimental study of the turbulent wake behind a cone at M = 5; Heat transfer augmentation by steady ...

Science.gov (United States)

Fundamental study of heat transfer augmentation of tube inside surface by cascade smooth surface-turbulence promoters

International Nuclear Information System (INIS)

This textbook contains the following main topics: Heat conductivity, convection, condensation and evaporation, radiation heat transfer and heat exchangers. It includes the physical foundations for all these aspects and many examples. (orig.)

Energy Technology Data Exchange (ETDEWEB)

A method of augmenting heat transfer in the interior of a fluid or from the interface of a solid in contact to a fluid by utilizing electro hydrodynamic (EHD) phenomena has the following advantages: the heat transfer can be effected by using a relatively small, light-weight high voltage source and some simple structural members; no vibration and noise are generated; the method has a control function to control heat transfer by adjustment of field and voltage; and this method is effective in cost-saving. It is mass transfer by the electric force caused by interaction between true charges or polarized charges in a fluid and external electric filed that plays an important role in most of such heat transfer augmentation methods by EHD. Examples of heat transfer ...

International Nuclear Information System (INIS)

The authors discuss a two-phase two-component experimental system developed to study enhancement of heat transfer from a vertical chip size heater to surrounding liquid (Freon 113 or Ethanol) due to air jet impingement. Heat transfer coefficient was measured as function of jet velocity, heat flux and the distance between exit of jet tube and heated surface. The injector was placed very close to the hot surface. It was found that the heat transfer was notably enhanced with foreign gas impingement, especially in the cases of small temperature differences between wall and coolant. In fact for higher jet velocities the heat transfer coefficients tended to infinite while the temperature differences between wall and coolant were zero. The heat ...

Science.gov (United States)

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Science.gov (United States)

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Energy Technology Data Exchange (ETDEWEB)

Experimental investigation was carried out for friction factor and heat transfer coefficient in the case of a rotating tube with a twisted-tape insert for heat transfer augmentation. The data obtained were compared with existing data for a stationary tube with a twisted-tape insert. It has been observed that the enhancement in heat transfer offsets the rise in friction factor due to rotation, with respect to a plain tube under stationary conditions. A correlation has been proposed for the data obtained.

International Nuclear Information System (INIS)

This experiment investigated the effects of free-stream turbulence intensity, length scale, Reynolds number, and leading-edge velocity gradient on stagnation-region heat transfer. Heat transfer was measured in the stagnation region of four models with elliptical leading edges downstream of five turbulence-generating grids. Stagnation-region heat transfer augmentation increased with decreasing length scale but an optimum scale was not found. A correlation was developed that fit heat transfer data for isotropic turbulence to within #+-#4 percent but did not predict data for anisotropic turbulence. Stagnation heat transfer augmentation caused by turbulence was unaffected by the velocity gradient. The data of other researchers compared well with the correlation. A method of ...

International Nuclear Information System (INIS)

Heat-transfer augmentation by straight grid spacers in rod bundles is studied for single-phase flow and for post-critical heat flux dispersed flow. The heat transfer effect of swirling grid spacers in single-phase flow is also examined. Governing heat-transfer mechanisms are analyzed, and predictive formulations are established. For single-phase flow, the local heat transfer at a straight spacer and at its upstream or downstream locations are treated separately. The effect of local velocity increasing near swirling spacer is considered. For post critical heat flux (CHF) dispersed flow, the heat transfer by thermal radiation, fin cooling, and vapor convection near the spacer are calculated. The predictions are compared with experimental data with satisfactory agreement.

Energy Technology Data Exchange (ETDEWEB)

This investigation concerns the nonlinear dynamics of heat transfer from a surface using an upstream eddy promoter. A numerical model is developed for the coupled fluid flow and heat transfer process based on a modified MacCormack scheme. Numerical simulations are carried out to determine the response and heat transfer enhancement due to the promoter. The average heat transfer from a cavity floor is seen to be increased by a factor of approximately five over the unpromoted'' flow. Another interesting feature of the study is the nonlinear viscous flow dynamics from the cylinder-wall interaction which differ significantly from the familiar cylinder-free stream patterns.

Energy Technology Data Exchange (ETDEWEB)

A metal matrix is inserted into a phase-change material to enhance the heat transfer during phase-change processes. The metal matrix tends to act like a heat transfer fin from the heated or cooled surface and to increase the effective thermal conductivity of the phase-change fluid. The scope of the study involves numerically modeling the heat transfer to and from constant-temperature cylindrical tubes surrounded by water during the freezing and melting processes. Comparisons of heat transfer with and without the metal matrix are made, with different porosities and densities of the metal matrix being examined. The results of this study are discussed in terms of the effectiveness of the metal matrix as a heat transfer enhancement device.

Science.gov (United States)

Forced convective heat transfer in a cross-corrugated channel solar air heater has been studied experimentally using air as a working fluid. The channel was formed by two transversely positioned corrugated sheets and two flat thermally insulated side walls. One corrugated sheet was heated by a radiant heater, while the other was thermally insulated. The fluid velocity and temperature, and the wall temperature and the local heat flux across the heated corrugated sheet were measured for a variety of operating flow rates. Experimental results for the channel geometry have yielded the correlation Nu = 0.0743 (Re)[sup 0.76]. This heat-transfer coefficient is about 2.8 times that of a smooth flat channel. The experiments showed that local heat transfer rate was smaller on the valley of the corrugation than that on the peak. ...

International Nuclear Information System (INIS)

1 - Description of program or function: The COOLOD-N2 code provides a capability for the analyses of the steady-state thermal-hydraulics of research reactors. This code is a revised version of the COOLOD-N code, and is applicable not only for research reactors in which plate-type fuel is adopted, but also for research reactors in which rod-type fuel is adopted. In the code, subroutines to calculate temperature distribution in rod-type fuel have been newly added to the COOLOD-N code. The COOLOD-N2 code can calculate fuel temperatures under both forced convection cooling mode and natural convection cooling mode. A 'Heat Transfer package' is used for calculating heat transfer coefficient, DNB heat flux etc. The 'Heat Transfer package' is a subroutine program and is especially developed for research reactors in which plate-type fuel is adopted. ...

International Nuclear Information System (INIS)

An experimental study was undertaken to determine for the turbulent regime the heat transfer and fluid flow characteristics of a heat exchange array of unperforated, and perforated brass plates with 33% of the plate area open. In both cases, the plates were aligned parallel to the flow direction. For the flow conditions examined, the results showed enhancement of heat transfer and friction factor for the perforated array.

Energy Technology Data Exchange (ETDEWEB)

A comprehensive presentation is made of state-of-the-art configurations and design methodologies for heat transfer devices applicable to industrial processes, automotive systems, air conditioning/refrigeration, cryogenics, and petrochemicals refining. Attention is given to topics in heat exchanger mechanical design, single-phase convection processes, thermal design, two-phase exchanger thermal design, heat-transfer augmentation, and rheological effects. Computerized analysis and design methodologies are presented for the range of heat transfer systems, as well as advanced methods for optimization and performance projection.

Energy Technology Data Exchange (ETDEWEB)

Fundamental phenomena of condensation heat transfer at a steam-water interface have been studied related to the thermo-hydrodynamics of the emergency core cooling system for light water reactors. In this study temperature fluctuations near the interface and in the liquid phase were measured using fine thermocouples for a saturated steam-subcooled water co-current stratified two-phase flow in a nearly horizontal rectangular channel, and heat transfer coefficients were determined experimentally. The values of the condensation heat transfer coefficients in this experiment are from 6 to 40 kW/m{sup 2}K. In the regions of high Reynolds numbers, as the steam Reynolds numbers become larger, the average interfacial heat transfer coefficients tend to increase. The corelations of Nusselt numbers were obtained from the ...

Energy Technology Data Exchange (ETDEWEB)

An attempt is made to augment the heat transfer efficiency by means of inserting an oscillating thin plate into a tube of the shell and tube heat exchanger. However, the heat transfer augmenting mechanism has not been fully explained. To elucidate this heat transfer augmenting mechanism, an investigation was given on the heat transfer characteristics of a tube inlet at its preliminary run area when a double-hinged oscillating thin plate is inserted in the inlet. As a result of the experiment, the heat transfer augmentation in the tube as a result of inserting the double-hinged oscillating thin plate was found effective when the preliminary inlet run area is treated as the object. However, in comparison of the effect with the heat ...

Energy Technology Data Exchange (ETDEWEB)

(Boiling site densities and heat-transfer coefficients have been measured for ethanol-water and ethanol-benzene mixtures at 1.01 bar for a heated vertical brass disk. A strong effect of composition on the boiling site density was observed, which was attributed to the nature of the activation of the boiling surface and mass diffusion effects. The boiling heat-transfer coefficient was found to decrease with increasin subcooling, but for the mixtures at a given level of subcooling the decrease was less than that for the single components and azeotropic mixtures.) The heat-transfer coefficient at a given heat flux was seen to be quite insensitive to the very large increase in boiling site density in comparing the pure water and the ethanol-water azeotrope results, leading one to question pool boiling models that predict heat-transfer rates on the basis of boiling ...

Science.gov (United States)

... roughness. Since T u'v' and q v'"F the heat transfer augmentation is the square root of the skin friction augmentation: - 1/2 (( St - ,Cf 0 ...

Science.gov (United States)

The effect of velocity gradient on stagnation region heat transfer augmentation by free stream turbulence was investigated. Heat transfer was measured in the stagnation region of four models with elliptical leading edges with ratios of major to minor axes of 1:1, 1.5:1, 2.25:1, and 3:1. Four geometrically similar, square bar, square mesh, biplane grids were used to generate free stream turbulence with different intensities and length. Heat transfer measurements were made for the following ranges of parameters: Reynolds number, based on leading edge diameter, 37,000 to 228,000; dimensionless leading edge velocity gradient, 1.20 to 1.80; turbulence intensity, 1.1 to 15.9%; and length scale to leading edge diameter ratio, 0.05 to 0.30. Stagnation point heat transfer augmentation by free stream turbulence can be predicted ...

International Nuclear Information System (INIS)

The Subseabed Disposal Program has recently completed a 30-day, 0.286-scale laboratory simulation of an In Situ Heat Transfer Experiment (ISHTE), scheduled for eventual deployment in the deep ocean 600 nautical miles north of Hawaii. 10 figures.

Science.gov (United States)

Scraped-surface heat transfer augmentation is proposed as a possible technique for use in improved air-cooling designs. Although it has been in common use with liquids, the technique has apparently never been used with gases. An experimental investigation...

Science.gov (United States)

... Originator-supplied keywords include: Turbulators, Heat transfer augmentation, Enhancement, Fire tube boilers. (Author). ...

International Nuclear Information System (INIS)

... failures fftf reactor heat transfer hydraulics loss of coolant pipes primary coolant

International Nuclear Information System (INIS)

(Jun 1982). United States Edelman, Z. Chambre, P. Eilas, E. Naot, D. Technion,

Science.gov (United States)

Unsteady impinging jets are systematically controlled with respect to their time dependence in order to investigate the influence of unsteadiness on the heat transfer performance. This is achieved by a special mass flow control device, which allows almost arbitrary shapes of unsteadiness to be imposed onto the impinging jet. Three different standard signals (sinusoidal, triangular, rectangular) and two specially designed signals are applied and their influence on heat transfer is determined in terms of an enhancement factor. Heat transfer augmentation up to 30% was found and could be physically explained with the help of PIV and hot-wire measurements of the flow field.

Science.gov (United States)

... solid particle contamination. Solid particulate impact is a good mechanism for surface heat transfer augmentation. The aug ...

Energy Technology Data Exchange (ETDEWEB)

High-performance heat transfer augmentation methods applicable in the forced convection field of heat exchangers include a method which requires no external drive means, such as the insertion of a turbulence augmentation object into the flow passage and the use of a wave-shaped flow passage, but disturbs the main stream of flow to raise the heat transportation effect thereby to augment heat transfer in the flow passage. The heat transfer characteristics and thermal performance ratio achieved when sinusoidal-shape plates are inserted instead of augmentation objects, such as cylinders, with a high shape-induced resistance were studied. As a result, the relationship between the resistance coefficient, average Nusselt number, heat transfer coefficient, and pitch was clarified. It has ...

British Library Electronic Table of Contents (United Kingdom)

In order to reduce the size and cost of heat exchangers, an air-side wavy fin-and-tube heat transfer surface with three-row tubes needs to be replaced by two-row tubes with some appropriate enhancing techniques. The major purpose of the present paper is to search for such new structure by numerical simulation. First, longitudinal vortex generators of Delta-winglet type are tried. The influence of number and of arrangement of the winglets on the performance of the heat transfer surface is studied in detail. The numerical results show that the fin with two winglets aligned spanwise in the front and rear of each tube (Fin W6) has higher heat transfer capability than other enhanced structures with vortex generators, but it still unable to meet the heat transfer requirement. Then a combination ...

International Nuclear Information System (INIS)

This paper describes the heat transfer augmentation and flow situation around a single spacer (a circular cylinder) on a heated surface in a parallel plate duct in order to examine basically the effects of the spacer in the fuel elements of a High Temperature Gas-cooled Reactor. A thermosensitive liquid crystal film was used to clarify the effective region of the heat transfer. The mean Nusselt number, which was estimated within arbitrary distance from the spacer to the downstream direction, took a peak at the dimensionless distance X/D = 1 #approx# 3, and after that decreased gradually with flow direction. How heat transfer corresponds to the flow situation is also examined. The horseshoe vortex, produced around the spacer, affects the wake and contributes to the increase of the local heat transfer. ...

International Nuclear Information System (INIS)

This book is organized under the following headings: Electrohydrodynamic heat transfer augmentation; Forced convection augmentation and heat transfer control; Turbulent heat transfer; Thermal problems in the environment; Energy conversion systems; Measurement, visualization, and imaging; Thermal problems in space technology; and Thermal properties.

Science.gov (United States)

Analytical solutions are derived for a flow in a semi-infinite vertical porous medium with heat and mass transfer. When the temperature and mass concentration are uniform a constant pressure is possible and sustains a fully developed flow. Thereafter there is a small perturbation on the wall temperature and concentration and the subsequent two-dimensional problem is tackled for a large Prandtl number, free convection parameters and small Reynolds number. The heat transfer rate at the wall is discussed quantitatively.

Energy Technology Data Exchange (ETDEWEB)

This report focuses on a better understanding of the physical phenomenon related to the enhancement of boiling and non-boiling heat transfer by applying ultrasonic waves. Experimental results obtained both in a pool of water and in a vertically upward water flow proved clearly that macroscopic acoustic stream induced by ultrasonics is a major contribution to heat transfer augmentation. (author).

Science.gov (United States)

The paper investigates the effect of the wall heat flux ratio on the local heat transfer augmentation in a square channel with two opposite in-line ribbed walls for Reynolds numbers from 15,000 to 80,000. The square channel composed of 10 isolated copper sections has a length-to-hydraulic diameter ratio of 20. The rib height-to-hydraulic diameter ratio is 0.0625 and the rib pitch-to-height ratio equals 10. Six ribbed side to smooth side wall heat flux ratios are studied for four rib orientations. The results show that the ribbed side wall heat transfer augmentation increases with increasing ribbed side to smooth side wall heat flux ratios, but the reverse is true for the smooth side wall heat transfer augmentation. The average heat transfer augmentation of ...

British Library Electronic Table of Contents (United Kingdom)

Mixed convection heat transfer from longitudinal fins inside a horizontal channel has been investigated for a wide range of modified Rayleigh numbers and different fin heights and spacings. An experimental parametric study was made to investigate effects of fin spacing, fin height and magnitude of heat flux on mixed convection heat transfer from rectangular fin arrays heated from below in a horizontal channel. The optimum fin spacing to obtain maximum heat transfer has also been investigated. During the experiments constant heat flux boundary condition was realized and air was used as the working fluid. The velocity of fluid entering channel was kept nearly constant (0.15win0.16m/s) using a flow rate control valve so that Reynolds number was always about Re=1500. Experiments were conducted...

International Nuclear Information System (INIS)

A numerical analysis is performed to clarify the heat transfer characteristics of combined convection around the tubes which form a single row perpendicularly arranged to a forced flow in the direction of gravity. A boundary-fitted coordinate transformation technique is adopted to solve the governing equations numerically. It is found in the case of liquid sodium that gravity-induced flow gives no substantial effect to heat transfer augmentation in a low Reynolds number region while it can be sufficiently expected in the ordinary fluids in the same Reynolds number region. This means that such heat transfer augmentation as expected in ordinary fluids can not be realized when crossflow-type heat exchangers installed for decay-heat removal operates in a low Reynolds number region. (author).

Energy Technology Data Exchange (ETDEWEB)

An experimental and theoretical study of heat and mass transfer analogy and a comparison of that to a binary liquid mixture evaporation is presented. Common organic solvents, ethanol and n-heptane, were used to form an alcohol - hydrocarbon mixture. Studies were carried out in a horizontal rectangular channel having air flow velocities of 0.2 - 0.9 m/s. Heat transfer coefficients were measured with a copper plate resistor and mass transfer coefficients with a square pool. The heat and mass transfer analogy is presented for a system having two evaporating compounds with a fixed value of air flow and verified by measuring and comparing mass transfer coefficients for distilled water with air flow velocities of 0.2 - 0.9 m/s. An illustrative example of the use of the theory for industrial ventilation is presented. (author)

International Nuclear Information System (INIS)

Counter rotating longitudinal vortices produced by winglet in a channel are known to enhance heat transfer. In the present investigation the flow structure and heat-transfer enhancement by a winglet pair of non-zero thickness has been studied. A delta winglet pair type vortex generator is placed in a hydrodynamically developed and thermally developing laminar channel flow. Computations are done by solving the unsteady, three-dimensional, incompressible Navier-Strokes equations and energy equation using a modified Marker-and-Cell (MAC) method. The flow structure is complex and consists of main, corner and induced vortices. It is observed that as compared to a channel without winglets, the heat transfer is enhanced by 33% when single winglet is used and by 67% when a winglet pair is employed. Effects of thickness of the winglets and Reynolds number on the heat ...

Energy Technology Data Exchange (ETDEWEB)

Numerical investigations of three-dimensional flow and heat transfer in a finned tube with punched longitudinal vortex generators (LVG`s) are carried out for Reynolds number of 250 and 300. Air with a Prandtl number of 0.7 is used as the fluid. The flow is both thermally and hydrodynamically developing. The LVG is a delta winglet pair (DWP) punched out of the fin and is located directly behind the tube, symmetrically separated by one tube diameter. The DWP generates longitudinal vortices in the wake of the tube, defers flow separation on the tube, deflects the main stream into the tube wake, and strong reduces the ``dead water zone.`` Heat transfer reversal is avoided by the DWP. Comparison of the span-averaged Nusselt numbers for the fin with and without DWP shows significant local heat transfer enhancement of several hundred percent in the tube wake. For Re = ...

International Nuclear Information System (INIS)

Heat transfer augmentation based on the process intensification concept in heat exchangers and thermal reactors has received much attention in recent years, mainly due to energy efficiency and environmental considerations. The concept consists of the development of novel apparatuses and techniques that, compared to those commonly used today, are expected to bring dramatic improvements in manufacturing and processing, substantially decreasing equipment size, energy consumption, and ultimately resulting in cheaper, sustainable technologies. The objective of this paper was to investigate the heat transfer characteristics of tubular thermal reactor using static mixing technology. Glycerin and water were used as the test fluids and water was used as the heating source. The results for heat transfer rate were strongly ...

Energy Technology Data Exchange (ETDEWEB)

The heat transfer augmentation effect by the unsteady heat conduction between the particles and heat transfer surface is one of the main factors, causing the heat transfer augmentation around the stagnation point in the gas-solid two-phase impinging jet flow. By separating and evaluating that effect, material influence on it was studied of particles and heat transfer surface, together with change by the jet flow condition. That effect enlarged with enlarging in heat capacity, multiplied by the heat conduction coefficient, of both the particles and heat transfer surface, and if both of them were constant in material combination, was dominated by the contact frequency of particles per unit time. Therefore in case of ...

International Nuclear Information System (INIS)

The effect of heat transfer is described from heat exchange tubes of a horizontal steam generator on the distribution of primary water to the individual tubes of the tube bundle. It is shown that in a broad interval of mass flow rates and lengths of heat exchange tubes, the simplified method of calcualtion, i.e., calculation of the distribution of primary water into heat exchange tubes neqlecting the changes of physical properties of water along the heat exchange tubes, will yield sufficiently accurate results. (author).

Energy Technology Data Exchange (ETDEWEB)

Direct Flame Impingement involves the use of an array of very high-velocity flame jets impinging on a work piece to rapidly heat the work piece. The predominant mode of heat transfer is convection. Because of the locally high rate of heat transfer at the surface of the work piece, the refractory walls and exhaust gases of a DFI furnace are significantly cooler than in conventional radiant heating furnaces, resulting in high thermal efficiency and low NOx emissions. A DFI furnace is composed of a successive arrangement of heating modules through or by which the work piece is conveyed, and can be configured for square, round, flat, and curved metal shapes (e.g., billets, tubes, flat bars, and coiled bars) in single- or multi-stranded applications.

Energy Technology Data Exchange (ETDEWEB)

Heat transfer augmentation techniques (passive, active or a combination of passive and active methods) are commonly used in areas such as process industries, heating and cooling in evaporators, thermal power plants, air- conditioning equipment, refrigerators, radiators for space vehicles, automobiles, etc. Passive techniques, where inserts are used in the flow passage to augment the heat transfer rate, are advantageous compared with active techniques, because the insert manufacturing process is simple and these techniques can be easily employed in an existing heat exchanger. In design of compact heat exchangers, passive techniques of heat transfer augmentation can play an important role if a proper passive insert configuration can be selected according to the heat exchanger ...

Energy Technology Data Exchange (ETDEWEB)

The major goal of this continuation project is to advance the utilization of heat transfer enhancement techniques in commercial heat exchange equipment. Thirteen heat transfer enhancement techniques have been identified as having potential for improving heat transfer coefficients in full-scale industrial equipment. The following tasks are part of this project, which was originally planned for three years: (1) expansion of technology information base; (2) evaluation of performance of enhanced surfaces and inserts; (3) correlation of data for spirally fluted surfaces; (4) study of structured surfaces in pool boiling; and (5) study of structured surface in spray film evaporation.

Energy Technology Data Exchange (ETDEWEB)

Compact heat exchangers have traditionally found wide application in the transportation industry, where they are used as evaporators and condensers in vapor compression cycles for air conditioning and refrigeration. Such heat exchangers possess numerous attractive features including high thermal effectiveness, small size, low weight, design flexibility, and pure counterflow, and they can accommodate multiple streams. Today, there is a widespread interest in expanding the range of application of compact heat exchangers to include phase-change heat transfer in the process industries, among others. An overall objective of this effort is to provide the basis for establishing design technology in this area. In the present study, small channel flow boiling heat transfer was extended to a rectangular channel (4.06 {times} 1.70 mm) using refrigerant ...

International Nuclear Information System (INIS)

Heat transfer enhancement in a heat exchanger tube by installing a baffle is reported. The effect of baffle size and orientation on the heat transfer enhancement was studied in detail. Three different baffle arrangements were considered. The results show that for the vertical baffle, an increase in the baffle height causes a substantial increase in the Nusselt number but the pressure loss is also very significant. For the inclined baffles, the results show that the Nusselt number enhancement is almost independent of the baffle inclination angle, with the maximum and average Nusselt number 120% and 70% higher than that for the case of no baffle, respectively. For a given baffle geometry, the Nusselt number enhancement is increased by more than a factor of two as the Reynolds number decreased from 20,000 to 5000. Simulations were conducted by introducing another baffle to enhance ...

Energy Technology Data Exchange (ETDEWEB)

This sheet summarizes information on geothermal heat pumps (GHPs), which extracts heat from the ground in the winter and transfers heat to the ground in the summer. More than 200,000 GHPs are operating in US; they can reduce energy consumption and related emissions by 23 to 44% compared to air-source heat pumps. Opportunities for use of GHPs, requirements, and cost are described. Important terms are defined.

International Nuclear Information System (INIS)

Heat transfer tubes of a primary pressurized water cooled (PPWC) in the high temperature engineering test reactor (HTTR) form the reactor pressure boundary of the primary coolant, therefore are important from the viewpoint of safety. To establish inspection techniques for the heat transfer tubes of the PPWC, an automatic inspection system was developed. The system employs a bobbin coil probe, a rotating probe for eddy current testing (ECT) and a rotating probe for ultrasonic testing (UT). Nondestructive test of a half of the heat transfer tubes of the PPWC was carried out by the automatic inspection system during reactor shutdown period of the HTTR (about 55% in the maximum reactor power in this paper). The nondestructive test results showed that the maximum signal-to-noise ratio was 1.8 in ECT. Pattern and phase of Lissajous wave, which were obtained for the ...

Science.gov (United States)

A glass heat pipe is adapted for use as a solar energy absorber in an evacuated tube solar collector and for transferring the absorbed solar energy to a working fluid medium or heat sink for storage or practical use. A capillary wick is formed of granular glass particles fused together by heat on the inside surface of the heat pipe with a water glass binder solution to enhance capillary drive distribution of the thermal transfer fluid in the heat pipe throughout the entire inside surface of the evaporator portion of the heat pipe. Selective coatings are used on the heat pipe surface to maximize solar absorption and minimize energy radiation, and the glass wick can alternatively be fabricated with granular particles of black glass or obsidian.

British Library Electronic Table of Contents (United Kingdom)

A type of Si3N4-based nanocomposites ceramic cutting tool material was prepared by the addition of nano-scale Si3N4W whisker and nano-scale TiN particle. Cutting performance of the Si3N4/Si3N4W/TiN nanocomposite ceramic tool in machining of cast iron was investigated in comparison with a commercial sialon ceramic tool, and the tool wear mechanism was studied. The two types of cutting tools have similar cutting performance at relatively low cutting parameters, while Si3N4/Si3N4W/TiN nanocomposite tool exhibits a better wear resistance than sialon tool at the relatively high cutting parameters. The wear of sialon ceramic cutting tool is dominated by the plastic deformation, abrasive action, microcracking, pullout of grains and chemical action at the higher cutting parameters. The higher mech...

Energy Technology Data Exchange (ETDEWEB)

A three-dimensional steady numerical computation was made for a component model of fin and tube type of compact heat exchangers situated in a uniform flow. In this study, in order to find a clue to design high-efficient heat exchangers, numerical computation was made in the case where two fences are attached on the plate fin surface and their geometrical effects such as their locations, their heights and their attack angles on flow and heat transfer characteristics were investigated especially in the low Reynolds number range. The effect of a hole, open in the plate fin behind the fence, on heat transfer and flow structures was also examined. This hole simulates the hole of the plate fin to be produced in practical application, when a fence is produced by punching from the original plain fin plate. Two fences with holes were found to show several important ...

International Nuclear Information System (INIS)

A large amount of energy has been consumed so far in so called matured industries such as iron and steel, oil refinery, petrochemical, ceramic, paper and pulp manufacturing and so forth. A successive stimulation on the preceding industries has to be enhanced from a technological viewpoint in order to maintain a further development based on novel and innovative technologies. In this regard, energy technology has become and will be increasingly important in a high temperature system so that the basic concept for heat transfer augmentation methods by thermal radiation is reviewed briefly in accord with the recent developments together with theoretical background and the prominent features. The heat transfer augmentation related to thermal radiation is summarized.

British Library Electronic Table of Contents (United Kingdom)

This paper focuses on the design and modeling of the humidification dehumidification desalination (HDH) process. The process is only found on experimental or very small pilot scale. Literature studies are rather limited and it includes a number of experimental investigations, performance evaluation, and measurements of the heat and mass transfer coefficients. This study includes useful and new data on the evaluation of the heat transfer coefficient of the humid air stream in the condenser unit. The analysis develops a correlation for the heat transfer coefficient for the humid air stream as a function of the Reynolds and Prandtl numbers. Also, detailed evaluation of the system performance is presented as a function of the system temperatures and the inlet relative humidity of the air strea...

Science.gov (United States)

Experiments were conducted to study the condensation heat transfer characteristics of horizontal enhanced tubes. In the current experiment, six different enhanced tubes, including 26, 40 fpi low fin tubes and four three-dimensional-fin tubes, were tested. The working fluid used in the experiment was HCFC-22. Data were presented in the form of overall heat transfer coefficient at three working pressures, namely 1.32, 1.47 and 1.62 Mpa. In addition, the condensing heat transfer coefficients for the test tubes were obtained from the Wilson plot technique.

Science.gov (United States)

Constant property, laminar flow heat transfer in a semicircular tube with uniform wall temperature has been analyzed to define the lower bound of heat transfer augmentation in circular tubes with twisted-tape inserts. Two thermal boundary conditions, which correspond to the two extremes of the fin effect of twisted tapes encountered in practical applications, are considered. Numerical solutions, employing finite-difference formulations for the governing momentum and energy equations were carried out for the thermal entrance region and for fully developed flow.

Energy Technology Data Exchange (ETDEWEB)

An experimental study of forced convection heat transfer at the inner tube wall of a double pipe heat exchanger with coiled wire inserts as heat transfer augmentation devices was performed over a turbulent flow region. The test results from twelve augmented tubes with inserts of different combinations of wire diameters (0.813, 1.016 and 1.575 mm) and pitches (2.82, 3.63, 5.08 and 8.47 mm) indicate that the turbulence promoters studied improve heat transfer by a factor of 1.4 to 2.24 compared with a smooth tube, although at a cost of 10-30 times increase in friction factor. A formula for presenting dimensionless exergy losses in a tubular heat exchanger is derived first and then the thermohydrodynamic optimum instead of economic optimum is found by minimizing the exergy losses in the system. From the ...

Science.gov (United States)

Page 1. - AERE-' R-7310 THIS DOCUMENT 15 INTENDED FOR PUBLICATION IN THE OPEN LITERATURE. ... Y Page 3. AERE R I 7318 ...

International Nuclear Information System (INIS)

This paper describes the construction of PWR horizontal steam generator in Soviet Union, the water chemistry treatment for secondary side, the design of steam separator, the test of heat transfer characteristics and operation. (author).

Science.gov (United States)

coupled heat/mass transfer Stefan problem. Taking the diffusion coefficient of Bi as a free parameter, the best fit was observed for the published value, ...

International Nuclear Information System (INIS)

(1970). United States Bell, KJ Taborek, J. Fenoglio, F. Minneapolis, Minn.

Energy Technology Data Exchange (ETDEWEB)

Ferrofluids have promising potential for heat transfer applications, since advective transport in a ferrofluid can be readily controlled by using an external magnetic field. However, unlike conventional free or forced convection, ferrohydrodynamic convection is not yet well characterized. A full understanding of the relationship between an imposed magnetic field, the resulting ferrofluid flow, and the temperature distribution is a prerequisite for the proper design and implementation of applications involving thermomagnetic convection. The literature variously assumes constant magnetic fields, does not completely represent the variation in the imposed field, or its descriptions are inaccurate, since the fields do not comply with the Maxwell's equations of electromagnetism. We address this by simulating two-dimensional forced convection heat transfer in a channel with a ferrofluid that is under ...

Science.gov (United States)

The flow and heat transfers associated with a plane laminar flow past a forward-facing step were analyzed using a power-law numerical scheme combined with a false vorticity-stream function approach. To improve the traditional wall-vorticity boundary condition, a novel method, based on an accurate description of the nonslip wall condition, was developed and utilized. The convergence for a 56 x 49 grid system was obtained in about 350 iterations. The computed reattachment distances in the upper separated region agree with the available experimental data for a blunt plate. The heat transfer augmentation is significant across the step; however, it is counterbalanced by the deterioration of heat transfer immediately upstream of the step.

Science.gov (United States)

note that this form for heat transfer augmentation has apparently never been used with other evaporation models, even though it is a natural extension of ...

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The ISI (In-Service Inspection) system has been developed so as to maintain the structural integrity of heat transfer tubes in the primary pressurized water cooler in the HTTR (High Temperature Engineering Test Reactor). This system consists of eddy current probes, ultra-sonic probes, insertion and extraction units, positioning unit and so on. Verification and performance tests of the developed ISI system were carried out using mock-up heat transfer tubes in the primary pressurized water cooler. The constitution of the system, R and D results of the inspection probes, and verification and performance test results of the ISI system for heat transfer tubes are described in this paper. (author)

British Library Electronic Table of Contents (United Kingdom)

The heat transfer a characteristics and friction factor in the horizontal double pipes of flat tubes with full length helical screw element of different twist ratio and helical screw inserts with different spacer length are investigated. Cold and hot water are used as working fluid in tube side and shell side respectively. The experiments covered a range of Reynolds numbers 5.7x102Re1.31x103. The effect of spacer length on the heat transfer augmentation and friction factor and the effect of twist ratio on heat transfer augmentation and friction factor have been presented separately. The study shows that, the Nusslet number (Nu) and friction factor (f) decrease with the increase of S or Y for flat tube. The comparison between the data of present plain circular with that of previous plain ci...

Science.gov (United States)

Mar 1, 2011 ... heat transfer augmentation in the stagnation region is presented. The effects of free stream turbulence and surface roughness on spanwise ...

Energy Technology Data Exchange (ETDEWEB)

Experimental studies on the heat transfer and fluid dynamics of a high heat flux fuel rod for a very high temperature reactor (VHTR) were performed using a single channel test rig of a fuel stack test section (T{sub 1-s}) installed in a helium engineering demonstration loop (HENDEL). The fuel rod has been developed in order to enhance the turbulent heat transfer coefficient than that of the standard fuel rod obtained by the previous experiment. Two-dimensional square ribs were settled on the outer surface of the fuel rod axially to improve the heat transfer. The configuration of a square rib is 0.5 mm in width(w), 0.5 mm in height(h) and 5 mm in pitch(p): p/h=10. The experiment were carried out under the helium gas conditions of high temperature and pressure simulated the VHTR operation. For the turbulent region of Reynolds number ...

International Nuclear Information System (INIS)

During the last two decades, the demand for higher heat transfers in the heat exchangers has kept increasing. These high heat transfer rates can be obtained by using two-phase flows, or heat transfer augmented surfaces, or in some cases, both. Thus, the boiling flows and the associated two-phase flow instabilities have been studied by many investigators. Most of the work in boiling flows has been concentrated on single channel upflow systems or on parallel channel systems with plain heat transfer surfaces. The boiling flow instabilities in multi-channel systems should be covered to a greater extent, studying the effects of various parameters, such as inlet and outlet restriction, mass flow rates, the property variations, heat transfer coefficients, equal and ...

International Nuclear Information System (INIS)

The Supercritical Water Cooled Reactor(SCWR) operates in a pressure around 25MPa and temperature of 293#approx#510 .deg. C. In order to study the heat transfer behaviors and good comparisons between the various fluids, a heat transfer test loop(SPHINX) using CO_2 has been constructed in KAERI as a part of international research program, I-NERI. At a supercritical pressure, the heat transfer coefficient is much larger than that estimated from the Dittus-Boelter correlation for a relatively large flow rate with moderate wall heat flux conditions. This phenomenon was explained by the rapid variations of the physical properties near the wall with the temperature. On the contrary, the heat transfer becomes worse when the bulk fluid enthalpy is below the pseudo-critical enthalpy under a low flow rate with ...

Science.gov (United States)

The local heat transfer coefficient distribution of a square channel with two opposite ribbed walls was determined. The square channel was connected to a sudden contraction entrance in order to simulate the inlet condition of the turbine blade cooling passages. The test channel was heated by thin stainless steel foils with a thickness of 0.000025 m, and instrumented with 180 thermocouples. The brass ribs of a square cross-section were glued periodically, in line, onto the top and bottom walls of the foil-heated channel in patterns to achieve the desired spacing and angle-of-attack. The local heat transfer coefficients on the smooth side and the ribbed side walls, at the channel entrance and the downstream regions, were measured for eight rib configurations and three Reynolds numbers (Re = 10,000, 30,000, and 60,000).

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The present investigation represents the initial phase of a comprehensive experimental program designed to study the potential for increasing the heat transfer per unit pressure drop in a ribbed duct by positioning vortex generators at key locations in the flow. In particular, the present investigation consists of a rib positioned at the inlet to a rectangular test section with uniform heating at its bottom wall. Local and average Nusselt number results are obtained for a circular rod positioned either immediately above or just downstream of the rib.

International Nuclear Information System (INIS)

The heat transfer characteristics of a newly developed transport and storage cask for vitrified heat-producing radioactive waste from reprocessing are described. The theoretical layout of the cask was tested by measurements on a prototype cask of the scale 1:1. These measurements confirmed the theoretical thermodynamic layout data. They can be described by the function Nu=CxRa"m, with the constant C, but not the constant m, differing for a vertical and a horizontal position of the cask. The measured velocity and temperature profiles of the cask were verified with an existing code for the calculation of heat transfer from finned horizontal cylinders by natural convection. (orig.).

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A numerical study of laminar flow and heat transfer in an array of stacked rectangular plates is presented. The array is placed in a uniform stream, and the plates are subjected to a constant surface heat flux. This flow configuration is relevant to a number of practical heat transfer devices with finned surfaces. The computations were performed using a finite volume solution of the steady, two-dimensional Navier-Stokes equations and energy equation. A numerical scheme that reduces numerical diffusion is used to discretize the equations. The dominant feature of the flow is the separation, and subsequent reattachment of, the boundary layer, which takes place at Reynolds numbers greater than about 75. The separation first occurs downstream of the leading edge of the plate; then as Re increases, the separation point moves upstream and remains fixed at the leading edge, and the ...

Energy Technology Data Exchange (ETDEWEB)

Experimental investigation of heat transfer and friction factor characteristics of circular tube fitted with full-length helical screw element of different twist ratio, and helical screw inserts with spacer length 100, 200, 300 and 400mm have been studied with uniform heat flux under laminar flow condition. The experimental data obtained are verified with those obtained from plain tube published data. The effect of spacer length on heat transfer augmentation and friction factor, and the effect of twist ratio on heat transfer augmentation and friction factor have been presented separately. The decrease in Nusselt number for the helical twist with spacer length is within 10% for each subsequent 100mm increase in spacer length. The decrease in friction factor is nearly two times lower than the full length helical twist at low Reynolds number, ...

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The present paper is concerned with development and application of a so-called Effective Convection Model (ECM), which aims to provide a detailed, mechanistic description of heat transfer processes in a BWR lower plenum. The ECM is a Computational Fluid Dynamics (CFD)-like tool which employs a simpler and more effective approach to compute heat transfer by solving only energy conservation equation instead of solving the full set of Navier-Stokes and energy equations by a CFD code. We implement the ECM in a CFD code (Fluent), with detailed description of the ECM development, implementation and validation. A dual approach is used to validate the ECM, namely validation against experimental data and against heat transfer results obtained by CFD predictions in the same geometries and conditions. Insights gained from CFD simulations are also used to improve ECM. The ...

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This book presents papers on internal combustion engines. Topics considered include the influence of partial suppression of heat rejection on performance and emissions, duothermic combustion, turbochargers made of sintered silicon nitrides, heat flux, low heat rejection engines, exhaust energy recovery, combustion chamber insulation, computerized simulation, heat transfer, friction, hoop stress effects, and bonding ceramics and metals.

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An assessment of the cooling requirements for fusion reactor components, such as the first wall and limiter/divertor, was carried out using pressurized water as the coolant. In order to establish the coolant operating conditions, a survey of the literature on departure from nucleate boiling, critical heat flux, asymmetrical heating and heat transfer augmentation techniques was carried out. The experimental data and the empirical correlations indicate that thermal protection for the fusion reactor components based on current design concepts can be provided with an adequate margin of safety without resorting to either high coolant velocities, excessive coolant pressures, or heat transfer augmentation techniques. If, however, the future designs require heat transfer enhancement techniques, experimental verification would be ...

Energy Technology Data Exchange (ETDEWEB)

An assessment of the cooling requirements for fusion reactor components, such as the first wall and limiter/divertor, was carried out using pressurized water as the coolant. In order to establish the coolant operating conditions, a survey of the literature on departure from nucleate boiling, critical heat flux, asymmetrical heating and heat transfer augmentation techniques was carried out. The experimental data and the empirical correlations indicate that thermal protection for the fusion reactor components based on conventional design concepts can be provided with an adequate margin of safety without resorting to either high coolant velocities, excessive coolant pressures, or heat transfer augmentation techniques. If, however, the future designs require unconventional shapes or heat transfer enhancement techniques, ...

British Library Electronic Table of Contents (United Kingdom)

Mixed convection heat transfer from longitudinal fins inside a horizontal channel has been investigated in the natural convection dominated region for a wide range of Rayleigh numbers and different fin heights and spacings. An experimental parametric study was made to investigate effects of fin spacing, fin height and magnitude of heat flux on mixed convection heat transfer from rectangular fin arrays heated from below in a horizontal channel. The optimum fin spacing to obtain maximum heat transfer has also been investigated. During the experiments constant heat flux boundary condition was realized and air was used as the working fluid. The velocity of fluid entering channel was kept nearly constant (0.02win0.025m/s) using a flow rate control valve so that Reynolds number was always about ...

Energy Technology Data Exchange (ETDEWEB)

This project dealt with use of condensing heat exchangers to recover water vapor from flue gas at coal-fired power plants. Pilot-scale heat transfer tests were performed to determine the relationship between flue gas moisture concentration, heat exchanger design and operating conditions, and water vapor condensation rate. The tests also determined the extent to which the condensation processes for water and acid vapors in flue gas can be made to occur separately in different heat transfer sections. The results showed flue gas water vapor condensed in the low temperature region of the heat exchanger system, with water capture efficiencies depending strongly on flue gas moisture content, cooling water inlet temperature, heat exchanger design and flue gas and cooling water flow rates. Sulfuric acid vapor condensed in both ...

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Characteristics of pressure drop and heat transfer have been investigated for a lithium single-phase flow and a helium-lithium two-phase flow in a horizontal conducting circular channel in the presence of a uniform transverse magnetic field up to 1.4 T as related to the lithium cooling for magnetic-confinement fusion reactors. By the application of the magnetic field to the lithium single-phase flow, remarkable heat transfer enhancement has been observed at the top wall due to the suppression of the mixed convection occurring in the low Peclet number range, while appreciable heat transfer deterioration appeared in the high Peclet number range. It has been confirmed that the helium-lithium two-phase flow can reduce the high magnetohydrodynamic (MHD) pressure drop in a lithium single-phase flow, and it can provide much better heat ...

Energy Technology Data Exchange (ETDEWEB)

The enhancement of longitudinal heat transfer by means of fluid pulsation in a pipe has been investigated analytically and numerically, including the transient state. The effects of pulsation amplitude, frequency, and pipe length on thermal properties such as effective thermal diffusivity and delay time are clarified. Their effects on numerical calculations are also presented and suggestions for efficient numerical calculations of this problem are made concerning the combination of parameters.

Energy Technology Data Exchange (ETDEWEB)

What utilizes the effect of electrohydrodynamical technique (EHD), as one of heat transfer augmentation methods, is methodically frequented and partially prepared to be put to practical use. Then, the heat transfer augmentation effect on nucleate boiling, utilizing the EHD effect, was both experimentally and theoretically studied from both the applicative and basic viewpoints. By adding fleon with 2wt% ethyl alcohol, higher in electric conductivity, in order to have the mitigation time of electric charge correspond to the bubbling frequency of bubble, the heat transfer augmentation was enabled to be about 8.5 times as high as that without impressing the electric field. As a result of observing the behavior of bubble in the electric field, was observed a phenomenon of bubble, moving from place to place, without ascending, on the plane electrode plate, by which ...

International Nuclear Information System (INIS)

Experimental studies on the heat transfer and fluid dynamics of a high heat flux fuel rod for a very high temperature reactor (VHTR) were performed using a single channel test rig of a fuel stack test section (T_1_-_s) installed in a helium engineering demonstration loop (HENDEL). The fuel rod has been developed in order to enhance the turbulent heat transfer coefficient than that of the standard fuel rod obtained by the previous experiment. Two-dimensional square ribs were settled on the outer surface of the fuel rod axially to improve the heat transfer. The configuration of a square rib is 0.5 mm in width(w), 0.5 mm in height(h) and 5 mm in pitch(p): p/h=10. The experiment were carried out under the helium gas conditions of high temperature and pressure simulated the VHTR operation. For the turbulent region of Reynolds number ...

International Nuclear Information System (INIS)

The augmentation of the heat transfer by inserting different type turbulators into the channels is the conventional passive enhancement method. The coiled wire is one of the common heat transfer enhancement devices. These turbulators generate almost-periodic vortices into the flow while increasing the heat transfer rate. In this study, the properties of these vortices (i.e. the vortex shedding frequency and amplitudes of the pressure fluctuations of the vortices), flow (vortex)-acoustic coupling and the relation between entropy generation and vortex characteristics were investigated experimentally. Strouhal-Re-N_s_,_a and P_r_m_s-Re-N_s_,_a variations were presented graphically. It was observed that as the pitch increases, the vortex shedding frequencies decrease and the maximum amplitudes of pressure fluctuation of vortices produced by coiled wire turbulators ...

Energy Technology Data Exchange (ETDEWEB)

The heat transfer a characteristics and friction factor in the horizontal double pipes of flat tubes with full length helical screw element of different twist ratio and helical screw inserts with different spacer length are investigated. Cold and hot water are used as working fluid in tube side and shell side respectively. The experiments covered a range of Reynolds numbers 5.7 x 10{sup 2} {<=} Re {<=} 1.31 x 10{sup 3}. The effect of spacer length on the heat transfer augmentation and friction factor and the effect of twist ratio on heat transfer augmentation and friction factor have been presented separately. The study shows that, the Nusslet number (Nu) and friction factor (f) decrease with the increase of S or Y for flat tube. The comparison between the data of present plain circular with that of previous plain circular tube showed a good ...

International Nuclear Information System (INIS)

A nonlinear mathematical model is presented of a WWER-440 nuclear power plant horizontal steam generator. On the proposed model is based a computer program for investigating transients in steam generators during loss of coolant accidents. Processes taking place at the primary side of the steam generator are described by a set of partial differential equations while those at the secondary side of the steam generator are described by plain differential equations with the variables being complex time functions. The model takes account of the coolant as both a single- and two-phase medium, of changes in the direction of the primary coolant flow and of changes in the direction of heat transfer. Heat transfer through the wall is based on a simple model of heat transfer through a thin-walled tube and includes a correction for the heat resistance of ...

International Nuclear Information System (INIS)

The use of heat transfer augmentation devices has been proposed as a means for reducing the cost of steam generators for advanced LMR designs by approximately 25%. Experimental results are presented for two types of enhancers in the form of a twisted-tape and a core-tube insert in the steam tube of a 13.1-m-long, sodium-heated single-tube test section. Test parameters were prototypical of liquid metal reactor (LMR) steam generator design for a once-through high-pressure steam cycle. Heat transfer results are compared with the no-insert case on an overall and local basis. Although both augmentations increased overall performance, the mechanisms were different.

British Library Electronic Table of Contents (United Kingdom)

Present paper is performed to investigate the heat and exergy transfer characteristics of forced convection flow through a horizontal rectangular channel where open-cell metal foams of different pore densities such as 10, 20 and 30PPI (per pore inches) were situated. All of the bounding walls of the channel are subjected to various uniform heat fluxes. The pressure drop and heat transfer characteristics are presented by two important parametric values, Nusselt number (NuH) and friction factor (f), as functions of Reynolds number (ReH) and the wall heat flux (q). The Reynolds number (ReH) based on the channel height of the rectangular channel is varied from 600 to 33 000, while the Grashof number (GrDh) ranged from approximately 105-107 depending on q. Based on the experimental data, new em...

Energy Technology Data Exchange (ETDEWEB)

We have been developing an innovative Steam Generator concept of Fast Breeder Reactors by using liquid-liquid direct contact heat transfer. In this concept, the SG shell is filled with a molten alloys, 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 to discuss the heat transfer mechanisms of the direct contact between the water and the alloy, this phenomenon was visualized by real-time neutron radiography. JRR-3M real-time thermal neutron radiography in Japan Atomic Energy Research Institute was used. Followings are main results. (1) The vigorous evaporation occurs in the molten alloy. This phenomena is different from the known phenomenon such as the evaporation of refrigerant R-113 in the water. (2) The evaporation in the bubble has ...

Energy Technology Data Exchange (ETDEWEB)

The testing performed during the last phase of the geothermal direct contact heat exchanger program utilizing the 500 kW pilot plant provided more insight into the capabilities and limits of the direct contact approach and showed that more work needs to be done to understand the inner workings of a large direct contact heat exchanger if they are to be modeled analytically. Testing of the column demonstrated that the performance was excellent and that the sizing criteria is conservative. The system operated smoothly and was readily controlled over a wide range of operating conditions. Performance evaluation showed pinch differentials of 4/sup 0/F or less and better than predicted heat transfer capability. Testing during this final phase was directed towards establishing the limits of the column to transfer heat. The working column height was shortened ...

Energy Technology Data Exchange (ETDEWEB)

A steady-state mathematical model was developed for a bare collector. Results obtained by previous authors for heat transfer and friction in rectangular ducts with periodic disturbances were employed to evaluate the effect of such disturbances on bare collector efficiency and on its pressure drop. An effective efficiency, which takes into account extra heat obtained and additional mechanical (electric) energy consumption for moving air when heat-transfer augmentation devices are employed, was defined. Simulation results are given for a bare collector, with and without perturbations, showing efficiency and effective efficiency dependence on collector dimensions, solar radiation intensity, disturbance diameter and pitch for collector performance optimization. (author).

British Library Electronic Table of Contents (United Kingdom)

It has been considered that dry-out occurs easily in boiling heat transfer for a small channel, a mini- or microchannel, because the channel was easily filled with coalescing vapor bubbles. In the present study, the experiments of subcooled flow boiling of water were performed under atmospheric conditions for a horizontal rectangular channel for which the size is 1 mm height and 1 mm width, with a flat heating surface of 10 mm length and 1 mm width placed on the bottom of the channel. The heating surface has a top of copper heating block and is heated by ceramic heaters. In the high heat flux region of nucleate boiling, about 70-80% of the heating surface was covered with a large coalescing bubble and the boiling reached critical heat flux as observed by high-speed video. In the beginning ...

Energy Technology Data Exchange (ETDEWEB)

Heat transfer augmentation in narrow rectangular channels in a target system is a very important method to remove high heat flux up to 12 MW/m{sup 2} generated at target plates of a high-intensity proton accelerator of 1.5 GeV and 1 mA with a proton beam power of 1.5 MW. In this report, heat transfer coefficients and friction factors in narrow rectangular channels with one-sided rib-roughened surface were evaluated for fully developed flows in the range of the Reynolds number from 6,000 to 1,00,000; the rib pitch-to-height ratios (p/k) were 10,20 and 30; the rib height-to-equivalent diameter ratios (k/De) were 0.025, 0.03 and 0.1 by means of previous existing experimental correlations. The rib-roughened surface augmented heat transfer coefficients approximately 4 times higher than the smooth surface at Re=10,000, p/k=10 and k/De=0.1; ...

Energy Technology Data Exchange (ETDEWEB)

A passive heat exchange enhancement structure which operates by free convection includes a flat mounting portion having a plurality of integral fins bent outwardly from one side edge thereof. The mounting portion is securable around a stovepipe, to a flat surface or the like for transferring heat from the pipe through the fins to the surrounding air by rotation-enhanced free convection.

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The mainly instationary operation of a solar heated receiver can be simulated with sufficient accuracy only if data about the dynamic behavior are available. For this reason, the dynamic behavior of a solar cavity receiver with parabolic dish collector is investigated. The development of a mathematical simulation considering heat transfer and storage processes is presented and the procedure for a numerical solution is illustrated. The performance of the calculation method is finally demonstrated by simulating the passage of a cloud.

Energy Technology Data Exchange (ETDEWEB)

The unsteady state heat transfer behaviour of a vertical wall subject to the effects of uniform radiation is investigated and the dimensional analysis of combined heat transfers by conduction, convection and radiation is presented. The convective heat transfer coefficients used in the numerical model are determined experimentally by means of an assembly resembling the conditions encountered in the dwelling (variable temperatures and heat flows in time and space, wall associated with a floor, radiative flux outside the wall). In routine conditions (homogeneous wall dimensions, temperature differentials less than 40/sup 0/C), it is shown that the problem depends in practice on three parameters (instead of five) and that nomographs can give the energy accumulated in the wall as a function of its geometric and thermal charactersitics and the ...

International Nuclear Information System (INIS)

To resolve the central thermal safety issue for spent fuel dry storage concrete canister design or Wolsung (CANDU) nuclear power plant unit 1, a thermal analysis method has been developed for the complicated geometry of rod bundles and the multi-dimensional and multi-mode heat transfer phenomena. The canister geometry is simplified and combined heat transfer by conduction, convection, and radiation is considered through effective heat transfer coefficients. Mean temperature distributions of the fuel bundles within the fuel basket are obtained by solving the heat transfer problem using an existing computer code HEATING5. The measured steady state temperature distribution within a mock-up of a storage basket is compared to the calculated result. Steady state and/or transient fuel temperature ...

International Nuclear Information System (INIS)

The helium-cooled HTGR (High Temperature Gas-cooled Reactor) will take an important position in the global energy strategy. It is expected to supply not only electricity but also high quality thermal energy for various industries and local utilities without exhausting any green house effect gas or acid rain gas. The key R and D issue of the HTGR is economical competitiveness, particularly against light water reactors. Due to the poor heat transfer of the single phase helium, the HTGR's volumetric power density is restricted to tenth of corresponding PWR's value so that increasing the power density by improving heat transfer is strongly desired. The standstill can be broken through by adopting gas-solid suspension medium. Its heat transfer performance is quite excellent. Its heat capacity can be increased drastically without excessive ...

International Nuclear Information System (INIS)

A numerical and experimental investigation is carried out in a solar thermochemical reactor for the thermal dissociation of ZnO at 2000 K using concentrated solar energy. The reactor consists of a cavity-receiver lined with ZnO particles and directly exposed to high-flux irradiation. A transient heat transfer model is formulated to link the rate of radiation, convection, and conduction heat transfer to the reaction kinetics. The radiosity and Monte Carlo methods are applied to obtain the distribution of net radiative fluxes at the internal surfaces of the reactor cavity and at the surface of the ZnO bed. Validation is accomplished in terms of the calculated and measured transient temperature profiles and chemical reaction rates.

International Nuclear Information System (INIS)

Stable boiloff of core water during a severe LWR accident, that is, boiloff driven only by the decay power generated below the water level, is tractable analytically and is relatively insensitive to axial power distribution. As might be expected, calculated accident event times are sensitive to the fidelity of the decay power model. During later stages of boiloff, heat transfer or transport of energy from above the water level to the residual water can result in an unstable condition during which the boiloff rate increases greatly. The unstable boiloff phenomenon illustrates the highly nonlinear influence of core heat transfer during meltdown and emphasizes the great accuracy requirements which attend the modeling of the accident during periods of enhanced heat transfer when significant zirconium oxidation is possible.

Energy Technology Data Exchange (ETDEWEB)

This experimental research investigates mixed convection and heat transfer augmentation by gaseous forced jets in a large enclosure, at conditions simulating those of passive containment cooling systems for Gen III+ passively safe reactors. The experiment is designed to measure the key parameters governing heat transfer augmentation by forced jets, and to investigate the effects of geometric factors, including the jet diameter, jet injection orientation, interior structures, and enclosure aspect ratio. The tests cover a variety of injection modes leading to flow configurations of interest for mixing and stratification phenomena in containments under accident conditions. Correlations for heat transfer augmentation by forced jets are developed and compared with experimental data. The characteristic recirculation speed inside the enclosure is introduced and ...

International Nuclear Information System (INIS)

Co-current stratified flow of liquid metal and water was investigated in a horizontal rectangular channel. Position of the interface pressure drop and direct contact heat transfer between these immisci ble liquids were measured in a fully developed flow. A turbulence model was proposed to explain the experimental results considering that the turbulence is damped near the liquid-liquid interface by surface tension. The analytical results showed good agreement with the experimental ones. Main results are that (1) position of the interface mainly depends on the flow rate ratio of both liquids, that (2) the pressure drop is approximately proportional to square of the average velocity of water, and that (3) heat transfer rate at direct contact interface is several times higher than that of co-current flow separated by a thin solid plate. (author).

International Nuclear Information System (INIS)

Dispersed flow film boiling is the heat transfer regime that occurs at high void fractions in a heated channel. The way this transfer mode is modelled in the NRC computer codes (RELAP5 and TRAC) and the validity of the assumption and empirical correlations used is discussed. An extensive review of the theoretical and experimental work related with heat transfer to highly dispersed mixtures reveals the basic deficiencies of these models: the investigation refers mostly to the typical conditions of low rate bottom reflooding, since the simulation of this physical situation by the computer codes has often showed poor results. The alternative models that are available in the literature are reviewed, and their merits and limits are highlighted. The modification that could improve the physics of the models implemented in the codes are identified. (author) 13 figs., ...

British Library Electronic Table of Contents (United Kingdom)

SBA-15 supported nano-scaled copper oxide was synthesized by impregnation method via ultrasonic-assisted route. The removal test from gas mixture containing 0.1?vol.% hydrogen sulfide was carried out over this material at atmospheric conditions. The effects of the chemical nature of copper oxide and the textural properties of the material on removal capacity were studied. The materials before and after the removal test were analyzed by nitrogen adsorption, X-ray diffraction, Transmission Electron Microscope, X-ray photoelectron Spectroscopy, Fourier Transform Infrared Spectrometer and Inductive Coupled Plasma. The results showed that copper species are located predominantly in mesopore channels, existing as copper oxide nanoparticles. Mesopores are active sites for removal reaction. The ou...

International Nuclear Information System (INIS)

Full text of publication follows: As the coolant experiences no phase change in the core, SCWRs, unlike LWRs, cannot use design criteria based on the critical heat flux concept. The commonly accepted practice in SCWRs is to specify cladding temperature limits that must be met during transient and accident events. Therefore for the design of the SCWR, it is very important to predict the heat transfer coefficient to the supercritical water coolant with great accuracy. Our recent study focuses on the critical issue of measuring heat transfer to supercritical water at prototypical SCWR conditions and to develop the tools to predict the SCWR thermal behavior. A heat transfer test loop using a surrogate fluids, CO_2, is under construction. The reason of using CO_2 instead of water is that (i) valuable insight of the physical phenomena can be ...

Energy Technology Data Exchange (ETDEWEB)

An experimental rig was set up to study the performance of a thermal storage unit using stearic acid as the heat storage medium. The unit mainly consists of an electrical heating rod and an outer tube, and the space between is an annulus that is filled with stearic acid. The thermal performance of the unit is measured, and the heat transfer characteristics of the melting processes of stearic acid are studied under different heat flux conditions to determine the influence of heat flux on the melting processes. A new type of fin is designed and fixed to the electrical heating rod to enhance the thermal response of the stearic acid. The experimental results show that the fin can improve the heat transfer of the melting process of the thermal storage unit greatly. The equivalent thermal conductivity of ...

Energy Technology Data Exchange (ETDEWEB)

Full text of publication follows: A porous media solution PORFLO has been developed for the 3-dimensional two-phase flow by describing the process facility in Cartesian or cylindrical coordinates. The local porosity fraction is applied for distinguishing the fluid filled volumes from the solid structures. The solid structure contribute the two-phase flow through the wall friction, flow area and heat transfer. Optionally the solid structure may contain primary liquid of steam generators, steam in the higher temperature and pressure to be condensed or electrical heating power. By using these optional boundary conditions three different process facilities have been analysed. The thermohydraulic solution based on 5-equation approach, where the conservation equations are solved for the liquid and gas (vapour) mass, mixture momentum (giving the velocity only for the mixture), liquid and gas energy, is described shortly. In ...

Energy Technology Data Exchange (ETDEWEB)

This paper presents a mathematical model to analyze the solar evaporation in a shallow pond in steady state, when the inlet flow rate, concentration, surface area and solar radiation are given. The simultaneous heat and mass transfer mechanisms are considered for quantifying the amount of evaporated water to the atmosphere and the actual absorbed heat by wastewater is calculated to obtain the bottom temperature of water pond. The heat losses to air by radiation and convection mechanisms are considered and the heat transmission across the water film is evaluated by the forced convection mechanism. 6 refs., 5 figs., 1 tab.

British Library Electronic Table of Contents (United Kingdom)

An experimental study was performed to investigate the heat transfer characteristics of the mixed convection flow through a horizontal rectangular channel where open-cell metal foams of different pore densities (10, 20 and 30 PPI) were situated. A uniform heat flux was applied at all of the bounding walls of the channel. For each of three values of the uniform heat flux, temperatures were measured on the entire surfaces of the walls. Results for the average and local Nusselt numbers are presented as functions of the Reynolds and Richardson numbers. The Reynolds number based on the channel height of the rectangular channel was varied from 600 to 33000, while the Richardson number ranged from 0.02 to 103, extending over forced, mixed and natural convection. Second important parameter that in...

Science.gov (United States)

Experimental results are presented for a new and unique heat transfer augmentation technique in tubes. The technique consists of inserting a porous mesh structure into the flow passage of the tube. Due to the increased degree of turbulence, both the singl...

Energy Technology Data Exchange (ETDEWEB)

Staggered arrays of dimples printed on opposite surfaces of a cooling channel is formulated numerically and optimized with hybrid multi-objective evolutionary algorithm and Pareto optimal front. As Pareto optimal front produces a set of optimal solutions, the trends of objective functions with design variables are predicted by hybrid multi-objective evolutionary algorithm. The problem is defined by three non-dimensional geometric design variables composed of dimpled channel height, dimple print diameter, dimple spacing, and dimple depth, to maximize heat transfer rate compromising with pressure drop. Twenty designs generated by Latin hypercube sampling were evaluated by Reynolds-averaged Navier-Stokes solver and the evaluated objectives were used to construct Pareto optimal front through hybrid multi-objective evolutionary algorithm. The optimum designs were grouped by k-means clustering technique and some of the clustered points were evaluated ...

Science.gov (United States)

Shape optimization of heat transfer augmentation device employed in turbine blade internal cooling passage has been performed numerically using single as well as multi-objective optimization procedures. Polynomial response surface approximation method and multi-objective genetic algorithm are used for single and multi-objective optimizations, respectively. Problem to enhance heat transfer rate considering staggered dimples on single surface of cooling passage has been formulated, and Reynolds-averaged Navier-Stokes equations are solved to analyze the flow field and the heat transfer. Three design variables defining channel and dimple dimensions, and two objective functions related to Nusselt number and friction drag are employed. Latin hypercube sampling is used to generate sampling points in design space, and the evaluated objectives are used to generate a set ...

Energy Technology Data Exchange (ETDEWEB)

The project is described, the motivation for the research and the microclimate is defined in relation to both building physics research and applications. Air temperatur, air humidity, solar radiation and air velocity are briefly considered, whilst driving rain and long-wave radiation are described in more detail. Convective heat transfer and surface coefficients are discussed, although they are not microclimatic factors, merely resulting from combinations of such factors. They are included as they are important in relation to transfer of heat and moisture at the surface of the building envelope. Driving rain measurement is the main area of interest, including development of measurement equipment. Long-wave irradiation is measured and compared with empirical formulae from the literature. Window convection heat transfer is another main area of interest. Nocturnal ...

Energy Technology Data Exchange (ETDEWEB)

The authors report experimental results of heat transfer in the region of transition to turbulence. The augmentation was induced through deployment of periodically placed cylindrical eddy promoters in parallel plane channel flows. Eight different configurations were used. The presence of eddy promoters displaced the point of transition from Reynolds number values of 1500 for the plane channel to around 400 for the least stable case. The value of Nusselt number at the transition for eddy promoters cases was up to 2.5 times higher than the one for the plane channel at the transition. Furthermore, the lower the transition Reynolds number, the higher the Nusselt number at the transition. For the cases where the diameter of the promoters was small and/or the pitch large, the heat transfer results in the transition region were consistent with values obtained from the Reynolds analogy when the analogy was ...

International Nuclear Information System (INIS)

The corona wind caused by nonuniform electric fields has been experimentally reported so far to be effectively applicable to heat transfer augmentation. In this paper, first, a theoretical and experimental study has been conducted to make clear such a mechanism of augmentation of heat transfer to a downward-facing flat plate due to a nonuniform electric field caused by a fine wire anode and a plate cathode as that ions produced near the wire electrode move to the plate introducing the bulk convective motion of fluid caused by collision of ions and neutral molecules. Secondly, experiments have been carried out by using twin and multi-wire electrodes and the plate to find the augmentation performance of heat transfer for the number and the arrangement of the wire electrodes, to explain the performance from the electrohydrodynamical standpoint based on the ...

Science.gov (United States)

An inner surface substrate of metal tubes is provided with a single layer of randomly distributed metal bodies bonded to the substrate, spaced from each other, and substantially surrounded by the substrate to form body void space.

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Mixed convection heat transfer from longitudinal fins inside a horizontal channel has been investigated in the natural convection dominated region for a wide range of Rayleigh numbers and different fin heights and spacings. An experimental parametric study was made to investigate effects of fin spacing, fin height and magnitude of heat flux on mixed convection heat transfer from rectangular fin arrays heated from below in a horizontal channel. The optimum fin spacing to obtain maximum heat transfer has also been investigated. During the experiments constant heat flux boundary condition was realized and air was used as the working fluid. The velocity of fluid entering channel was kept nearly constant (0.02 {<=} w{sub in} {<=} 0.025 m/s) using a flow rate control valve so that Reynolds ...

Energy Technology Data Exchange (ETDEWEB)

A safety analysis code to design a pressurized water reactor and to obtain the licenses including entire proprietary rights is under development in domestic R and D project. The tasks of KAERI is to develop the constitutive relations including models for defining flow regimes and flow regime related models for inter-phase friction, wall frictions, wall heat transfer, and interphase heat and mass transfer in the two-phase three-field equations. In this paper, the process will be presented for choosing the best flow regime maps which occur in gas-liquid two-phase flow in horizontal and vertical tubes.

Science.gov (United States)

We present the results obtained from tests and studies carried out on the model of tube bundles for a PGV-1000 horizontal steam generator that were conducted for experimentally substantiating the design service life of a steam generator tube bundle intended for use at new nuclear power stations equipped with a PGV-1000MKP steam generator. Measures taken to minimize the incipience and development of local corrosion damage to the heat-transfer tubes and ensure their design service life are substantiated and confirmed.

Energy Technology Data Exchange (ETDEWEB)

A simplified approach has been proposed to model the drying of capillary-porous materials with small geometric parameters for practical purposes. Luikov`s theory of mass and heat transfer for capillary-porous bodies was applied to drying of biological materials and it was shown that the thermo diffusion effect can be neglected if the thermal gradient remains small during the whole period of drying. The resulting simplified equations can then be solved using available mathematical software. The simplified equations were applied to drying of wood and a peanut pod

International Nuclear Information System (INIS)

A safety analysis code, named as SPACE, for a pressurized water reactor is under development to obtain a licensing to be used for the PWR design and to hold entire proprietary rights. The task of KAERI is to develop the physical models and correlations which are required to solve the field equations. It can be divided into four parts; i) flow regime determination, ii) wall heat transfer, iii) wall and interfacial friction, iv) interfacial heat and mass transfer. This paper will describe the process to develop the models for the two-phase flow regime maps in the horizontal and vertical pipes.

International Nuclear Information System (INIS)

Accurate prediction of ribbed duct flow and heat transfer is of importance to the gas turbine industry. The present study comprehensively validates the use of large eddy simulations (LES) for predicting flow and heat transfer with measured flowfield data in a stationary duct with 90"o ribs and elucidates on the detailed physics encountered in the developing flow region, the fully developed region, and the 180"o bend region. Among the major flow features predicted with accuracy are flow transition at the entrance of the duct; the distribution of mean and turbulent quantities in the developing, fully developed, and 180"o bend; the development of secondary flows in the duct cross-section and the 180"o bend; and friction and heat transfer augmentation. At the duct inlet, both the computations and experiments show that the peak turbulence intensities reach values as ...

Energy Technology Data Exchange (ETDEWEB)

The theoretical analysis of a partially-ionized hydrogen gas flow (gas temperatures of approximately 10,000 to 20,000 K) through a particular class of magnetohydrodynamic (MHD) generators and the preliminary design of these MHD generators as open cycle, electric power supplies are performed. Analysis of the gas flow through these ultra-high temperature MHD generators requires a coupled gas dynamics/radiative heat transfer solution. Gas dynamics are modeled by a set of quasi-one-dimensional, nonlinear differential equations which account for friction, convective and radiative heat transfer and the interaction between the ionized gas and applied magnetic field. Radiative heat transfer is modeled using non-gray, absorbing-emitting two- and three-dimensional P-1 approximations which permit an arbitrary variation of the spectral absorption coefficient with frequency. ...

International Nuclear Information System (INIS)

The report presents the results of experimental studies conducted to provide a description of the conditions which lead to the occurrence of critical heat flux (CHF), in Combustion Engineering (C-E) fuel assemblies using the C-E standard spacer grid. A CHF correlation is presented which is based on CHF data obtained in tests with electrically heated rod bundles representative of the C-E 14 x 14 and 16 x 16 array fuel assemblies. The results reported are for a uniform axial heat flux distribution. The experiments were conducted in the Medium Pressure Heat Transfer Flow Loop at the Chemical Engineering Research Laboratories at Columbia University.

Science.gov (United States)

Hot dry rock (HDR) contains insufficient permeability and fluid for natural hydrothermal development, but water pumped in a circulation loop through a HDR reservoir (hydraulically fractured between two drill holes) is being tested and evaluated. The formation of such in situ heat transfer systems, and subsequent testing of the man-made geothermal reservoirs in the Jemez volcanic field, New Mexico have already indicated the technical feasibility of the hot dry rock (HDR) geothermal concept. Documented production history and heat-extraction data obtained during the period from 1978 to 1980 have confirmed heat transfer, low water loss, and predictable thermal drawdown models for the HDR systems. During a nine month test of closed-loop heat extraction operations, 15 x 10/sup 6/ kWh of thermal energy were produced. The effective heat-transfer ...

Energy Technology Data Exchange (ETDEWEB)

The thermal and heat transfer characteristics of stearic acid during the solidification processes were investigated experimentally in a vertical annulus energy storage system. The temperature distribution and temperature variations with time at different radial positions during the freezing processes were obtained. The thermal characteristics of the stearic acid, including movement of the solid-liquid interface in the radial direction, and the effects of Reynolds number on the heat transfer parameters were studied. The heat flux was estimated by using a simple approximate model. A new copper fin was designed and fixed to the electrical heating rod to enhance the thermal conductivity of the stearic acid. The results show that the new fin can enhance both the conduction and the natural convection heat transfer of the PCM, ...

Energy Technology Data Exchange (ETDEWEB)

Experimental investigations are being conducted on a single-cylinder direct-injection diesel engine to examine the effects of combustion chamber specifications and swirl ratios on the heat release and transient heat transfer characteristics. Heat rejection was examined on the basis of heat release calculations using cylinder pressure time histories. Transient surface temperature data obtained from stationary locations in the piston and cylinder head were used as the basis for determining the transient heat flux rates. The results showed good agreement with the heat rejection calculated from cylinder pressure data and that transient heat flux in a piston cavity was reduced with the larger cavity diameter and a higher swirl ratio. On the other hand, a transient heat flux in a piston head was not ...

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The failure of receivers has been one of the main operating problems at the White Cliffs solar thermal power plant. This Technical Note reports the results of an initial investigation that identifies the cause as having been their thermal fatiguing of the tube walls. The fatigue appears to be caused by unstable heat transfer at vapor qualities below the point where critical heat flux is generally exceeded. Methods for avoiding this problem are tested.

Energy Technology Data Exchange (ETDEWEB)

In this work, the thermal performance of a conventional collector is improved by inserting porous substrates at the inner walls of the collector tubes. The porous substrates improve the convective heat transfer coefficient between the tube wall and the fluid. This improvement is investigated numerically and its effects on the efficiency and the useful gain of the collector are evaluated. It is found that inserting the porous substrate may raise the collector efficiency considerably, especially at high values of the overall heat loss coefficient.

Energy Technology Data Exchange (ETDEWEB)

A phenomenological model of the heat transfer in direct injection diesel engines was developed. Utilizing the thermodynamic results of a combustion model as an input, the model is able to predict the temporal variation of the heat losses from the cylinder gas to the cylinder walls. Additionally, the division into isothermal combustion chamber subsurfaces allows the consideration of the spatial variation of the wall heat fluxes. The physical mechanisms such as flow dependent convection, heat radiation due to hot soot particles and isolation effects of deposited soot layers are described in detail. Thus the effects of these mechanisms on the overall heat transfer can be studied. The heat transfer model was verified successfully by the comparison to measured wall heat fluxes in a ...

Energy Technology Data Exchange (ETDEWEB)

An advanced ceramic dome cavity receiver is discussed which heats pressurized gas to temperatures above 1800/sup 0/F (1000/sup 0/C) for use in solar Brayton power systems of the dispersed receiver/dish or central receiver type. Optical, heat transfer, structural, and ceramic material design aspects of the receiver are reported and the development and experimental demonstration of a high-temperature seal between the pressurized gas and the high-temperature silicon carbide dome material is described.

Energy Technology Data Exchange (ETDEWEB)

The thermal performance of an automotive radiator plays an important role in the performance of an automobile's cooling system and all other associated systems. For a number of years, this component has been given little attention with very little changing in its manufacturing cost, operation and geometry. As opposed to the old tubular heat exchanger configurations used in automotive radiators, plate heat exchangers currently form the backbone of today's process industry with their advanced performance reaching levels the designers of tubular heat exchangers can only dream of. The aluminium roll-bonding technique widely used in manufacturing the cooling compartments for domestic refrigeration units is one of the cheapest methods for heat exchanger manufacturing. Using this technique, it is possible to manufacture a wide range of heat exchanger configurations that ...

Energy Technology Data Exchange (ETDEWEB)

The flow distribution through a plate-fin heat exchanger is studied by using a computational fluid dynamics (CFD) code, FLUENT. The flow distribution through any heat exchanger affects its performance. In designing a heat exchanger, it is assumed that the fluid is uniformly distributed through the heat exchanger core. In practice, however, it is impossible to distribute fluid uniformly, because of an improper inlet configuration, imperfect design, and a complex heat transfer process. The CFD simulation of the flow distribution in the header of a conventional plate-fin heat exchanger is presented. It is found that the flow maldistribution is very serious in the y-direction of the header. A modified header is proposed and simulated using CFD. The modified header configuration has a more uniform flow distribution than the conventional header ...

British Library Electronic Table of Contents (United Kingdom)

In this study, usage of a variable speed refrigeration system in latent heat thermal energy storage (LHTES) system is investigated to increase energy storage efficiency. Four different compressor speed control cases are compared to obtain a constant heat transfer fluid (HTF) temperature at the inlet of the energy storage tank. These control cases are (i) control with evaporation temperature, (ii) control with ethylene glycol temperature at the outlet section of evaporator, (iii) control with suction pressure of the compressor and (iv) on/off control. By means of the experimental analysis the best control strategy is obtained as control with Case (ii), in terms of stability of inlet temperature of heat transfer fluid, variations of energy efficiency of LHTES and coefficient of performance (...

British Library Electronic Table of Contents (United Kingdom)

In this paper, the unsteady MHD free convection heat and mass transfer of viscous fluid flowing through a Darcian porous regime adjacent to a moving vertical semi-infinite plate under Soret and Dufour effect have been examined. Viscous dissipation effects are included in the energy equation. A uniform magnetic field is applied transversely to the direction of the flow. The differential equations governing the problem have been transformed by a similarity transformation into a system of non-dimensional differential equations which are solved numerically by element free Galerkin method. The influence of Grashof number (Gr), magnetic parameter (M), heat absorption parameter (Q), permeability parameter (K), Schmidt number (Sc), Soret number (Sr), and Dufour number (Du) on the velocity, tempera...

Energy Technology Data Exchange (ETDEWEB)

The described heat transfer model supplies plausible results for the size distribution of active nucleation spots. For boiling states for which a comparison with measured bubble covering density is possible, that is for low boiling pressures and low heat flux densities, the bubble covering densities calculated by model on the basis of heat transfer measurements agree relatively well with the values observed. (orig.) [Deutsch] Das beschriebene Waermeuebergangsmodell liefert plausible Ergebnisse fuer die Groessenverteilung der aktiven Keimstellen. Fuer die Siedezustaende, fuer die ein Vergleich mit gemessenen Blasenbelegungsdichten moeglich ist, d.h. fuer niedrige Siededruecke und kleine Waermestromdichten, stimmen die aufgrund der Waermeuebergangsmessungen mit dem Modell berechneten Blasenbelegungsdichten verhaeltnismaessig gut mit den beobachteten Werten ueberein. (orig.)

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This report presents the results of analysis of selected data from the NRU test series dealing with heatup and reflood heat transfer during postulated PWR LOCA conditions. These tests used nuclear fuel rods and some considered clad ballooning and rupture. Also included was an electrically-heated rod ballooning test, REBEKA-6. The COBRA-TF computer program, renamed PYTHONS, was modified and used for the analytical tool. Modifications included provisions for fuel rod gas flow and pressure, creep deformation and rupture, channel blockage, and blockage heat transfer. Calculated clad temperatures for NRU unpressurized rods show quite good agreement with experimental data. The calculated amount and axial extent of clad ballooning for pressurized rods agrees reasonably well with post-test examinations of the NRU bundles. Time to failure was underpredicted in the MT-3 test as a result of ...

Energy Technology Data Exchange (ETDEWEB)

Solar heating of gas turbine plants is moving back to the focus of current research. The mainly unsteady operation of solar turbine power plants can only be predicted with sufficient accuracy if the transient behavior of the solar radiation receiver is known. Therefore the transient behavior of cavity receivers of different designs is investigated. The mathematical model used to simulate heat transfer and energy storage is illustrated. Computed results for two receivers with different inner lining are compared and evaluated concerning their use in practice.

Science.gov (United States)

This paper deals with a mixed convection water flow in a horizontal rectangular duct, uniformly heated from one lateral vertical wall and thermally insulated elsewhere. The supplied heat flux induces a secondary flow, which structure is constituted of one longitudinal roll in the considered aspect ratio (? = 1.9), embedded into a return flow of possibly large stream wise extension (up to twenty channel heights). Such situation induces helicoidal trajectories for the fluid flow particles, which contributes to a heat transfer enhancement compared to purely forced convection flow.

Science.gov (United States)

When induced by bottom heating in a horizontal fluid layer which is characterized by forced motion or solute stratification, buoyancy-driven flows may assume a variety of forms. The flows, which are examples of mixed or double-diffusive convection, can strongly influence heat tranfer or the entrainment of stratified fluid. General aspects of each form of convection are reviewed, and emphasis is placed on mixed convection in a horizontal rectangular channel and on double-diffusive convection due to thermally driven mixed-layer development in a solutally stratified fluids. Flow conditions are described, and experimental and theoretical results are presented for related heat-transfer and entrainment parameters.

Science.gov (United States)

The Gas Research Institute established the Gas Appliance Technology Center (GATC) in 1982 to develop improved gas appliances. Between 1986 and 1992, the scope of GATC activities at Battelle included technology transfer and overall industry support, residential appliances, commercial appliances, and residential space conditioning. The following tasks are representative of the GATC activities described in the report; gas burner technology, appliance venting, emissions, water heating, range/oven technology, self-powered appliances, commercial cooktop burners, reconstituting ovens, appliance reliability improvement, combination space-heating/water-heating systems, condensing heat exchangers, corrosion testing, and space heating technology. The report includes references to available sources for further reading.

International Nuclear Information System (INIS)

Frictional pressure drop and heat transfer performance in a very narrow rectangular channel having one-sided constant heat flux and repeated-ribs were studied experimentally for turbulent water flows. Their empirical correlations were derived for designing target cooling channels to remove high heat flux generated at target plates in a high-intensity proton accelerator system. The rib pitch-to-height ratios (p/k) were 10 and 20 while holding the rib height constant at 0.2 mm, the Reynolds number (Re) from 2,400 to 98,500 under different channel heights (H) of 1.2 mm and 3.2 mm, the rib height-to-channel equivalent diameter ratio (k/D_e) of 0.088 and 0.036, respectively. The results show that the rib-roughened surface augments heat transfer by about 2-2.5 times compared with the smooth surface at the expense of around 2.5 times higher frictional pressure drop ...

Energy Technology Data Exchange (ETDEWEB)

A cooling system was developed which could be used even in such areas where the maximum and minimum temperatures of a day might differ widely. The system features in that a latent heat storage unit is connected to the natural circulation cooling unit consisting of 2 heat exchangers where condensed gas (refrigerant) which performs gas-liquid change has been sealed, enabling to cool objects night and day without the requirement for any power source. Electronic equipment was installed in an insulated shelter. Lauric acid and refrigerant R-22 were used as the latent heat storage medium and the heat transport medium respectively. Natural convection heat transfer performance of the outside surfaces of the condenser and the evaporator and the transient behavior of the system during the melting and solidification periods of the latent heat storage ...