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Showing papers on "Heat transfer published in 1990"


Journal ArticleDOI
TL;DR: In this article, a simple correlation was developed earlier by Kandlikar (1983) for predicting saturated flow boiling heat transfer coefficients inside horizontal and vertical tubes, which was further refined by expanding the data base to 5,246 data points from 24 experimental investigations with ten fluids.
Abstract: A simple correlation was developed earlier by Kandlikar (1983) for predicting saturated flow boiling heat transfer coefficients inside horizontal and vertical tubes. It was based on a model utilizing the contributions due to nucleate boiling and convective mechanisms. It incorporated a fluid-dependent parameter F{sub fl} in the nucleate boiling term. The predictive ability of the correlation for different refrigerants was confirmed by comparing it with the recent data on R-113 by Jensen and Bensler (1986) and Khanpara et al. (1986). In the present work, the earlier correlation is further refined by expanding the data base to 5,246 data points from 24 experimental investigations with ten fluids. The proposed correlation gives a mean deviation of 15.9 percent with water data, and 18.8 percent with all refrigerant data, and it also predicts the correct h{sub TP} versus x trend as verified with water and R-113 data yielded the lowest mean deviations among correlations tested. The proposed correlation can be extended to other fluids by evaluating the fluid-dependent parameter F{sub fl} for that fluid from its flow boiling or pool boiling data.

1,003 citations


Journal ArticleDOI
TL;DR: A new finite-volume method is proposed to predict radiant heat transfer in enclosures with participating media and test results indicate that good accuracy is obtained on coarse computational grids, and that solution errors diminish rapidly as the grid is refined.
Abstract: A new finite-volume method is proposed to predict radiant heat transfer in enclosures with participating media. The method can conceptually be applied with the same nonorthogonal computational grids used to compute fluid flow and convective heat transfer. A fairly general version of the method is derived, and details are illustrated by applying it to several simple benchmark problems. Test results indicate that good accuracy is obtained on coarse computational grids, and that solution errors diminish rapidly as the grid is refined.

824 citations


Journal ArticleDOI
TL;DR: The thermal dispersion conductivity tensor for convection in a porous medium is derived based on the method of volume averaging of the velocity and temperature deviations in the pores.

619 citations


Book
01 Jun 1990
TL;DR: In this paper, basic ϵon-N{sub tu} analysis for complicated flow arrangements, single-phase heat transfer and pressure drop measurements, correlations and predictions, and applications of compact heat exchangers are discussed.
Abstract: This book is covered under the following headings: Basic {epsilon}-N{sub tu} analysis for complicated flow arrangements; Single-phase heat transfer and pressure drop measurements, correlations and predictions; and Applications of compact heat exchangers.

542 citations


Journal ArticleDOI
TL;DR: In this article, the heat equation for an axially heated cylinder with a thermally conductive boundary at the periphery has been solved using both a full numerical solution and an analytic approximation which assumes only radial heat flow.
Abstract: In order to estimate deleterious effects caused by heating in continuous‐wave end‐pumped solid‐state lasers, the heat equation has been solved for an axially heated cylinder with a thermally conductive boundary at the periphery Steady‐state thermal profiles are developed using both a full numerical solution and an analytic approximation which assumes only radial heat flow The analytic solution, which is in good agreement with the numerical solution, is utilized to obtain an expression for the thermal focusing due to temperature‐induced refractive index changes For Nd:YAG, 1 W of pump power deposited as heat is predicted to cause a thermal focusing length comparable to the cavity length of a typical diode end‐pumped laser

536 citations


Journal ArticleDOI
TL;DR: A treatment of the self-heating problem is presented, showing that, in the steady state, some of the heuristic models of heat generation, thermal conductivity, and heat capacity could indeed approximate the correct results within an error bound of 1-10%.
Abstract: A treatment of the self-heating problem is presented. It is based on the laws of phenomenological irreversible thermodynamics (e.g. Onsager's relations and conservation of total energy) and is also consistent with the physical models usually considered in the isothermal drift diffusion approximation. The classical isothermal device equations are extended and completed by a generalized heat-conduction equation involving heat sources and sinks which, besides Joule and Thomson heat, reflect the energy exchanged through recombination (radiative and nonradiative) and optical generation. Thus the extended model also applies to direct semiconductors (e.g., optoelectronic devices) and accounts for effects caused by the ambient light intensity. It fully allows for low temperature since the case of incomplete ionization of donors and acceptors (impurity freeze-out) is properly incorporated in the theory. A critical comparison with previous work is made, showing that, in the steady state, some of the heuristic models of heat generation, thermal conductivity, and heat capacity could indeed approximate the correct results within an error bound of 1-10%. In the transient regime, however, none of the models used previously seems to be reliable, particularly, if short switching times ( >

467 citations


Journal ArticleDOI
TL;DR: In this paper, the physical meaning of the constant τ in Cattaneo and Vernotte's equation for materials with a nonhomogeneous inner structure has been considered and some values for selected products have been given.
Abstract: The physical meaning of the constant {tau} in Cattaneo and Vernotte's equation for materials with a nonhomogeneous inner structure has been considered. An experimental determination of the constant {tau} has been proposed and some values for selected products have been given. The range of differences in the description of heat transfer by parabolic and hyperbolic heat conduction equations has been discussed. Penetration time, heat flux, and temperature profiles have been taken into account using data from the literature and the experimental and calculated results.

459 citations


Journal ArticleDOI
TL;DR: In this paper, a 2-fluid thermal-hydraulic code capable of simulating thermal and mechanical phenomena occurring in the primary and secondary circuits of PWRs for a wide variety of accidental situations is presented.

397 citations


01 Jan 1990
TL;DR: In this paper, the authors introduce the physical effects underlying heat and mass transfer phenomena and develop methodologies for solving a variety of real-world problems and emphasize the importance of conservation principles, particularly the first law of thermodynamics, in heat transfer analysis, and have been expanded to encompass principles and problems in mass transfer.
Abstract: This text introduces the physical effects underlying heat and mass transfer phenomena and develops methodologies for solving a variety of real-world problems. It emphasizes the importance of conservation principles, particularly the first law of thermodynamics, in heat transfer analysis, and has been expanded to encompass principles and problems in mass transfer. Includes numerous examples and problems.

355 citations


Book ChapterDOI
TL;DR: The chapter summarizes analytical, numerical, and experimental work in literature, in order to facilitate the improvement of existing schemes and provide a basis for the development of new ones on the thermal control of semiconductor devices, modules, and total systems.
Abstract: Publisher Summary Thermal control of electronic components has one principal objective, to maintain relatively constant component temperature equal to or below the manufacturer's maximum specified service temperature, typically between 85 and 100°C. It is noted that even a single component operating 10°C beyond this temperature can reduce the reliability of certain systems by as much as 50%. Therefore, it is important for the new thermal control schemes to be capable of eliminating hot spots within the electronic devices, removing heat from these devices and dissipating this heat to the surrounding environment. Several strategies have developed over the years for controlling and removing the heat generated in multichip modules, which include advanced air-cooling schemes, direct cooling, and miniature thermosyphons or free-falling liquid films. The chapter summarizes analytical, numerical, and experimental work in literature, in order to facilitate the improvement of existing schemes and provide a basis for the development of new ones. The chapter focuses on investigations performed over the past decade and includes information on the thermal control of semiconductor devices, modules, and total systems.

285 citations



Book
01 Jan 1990
TL;DR: In this paper, the authors present an overview of the properties of Gases and Vapours, including their properties in terms of heat transfer mechanisms and diffusion and mass transfer, as well as their physical properties.
Abstract: Units and Dimensions Density and Specific Gravity Properties of Fluids, Hydrostatics and Dynamics Viscosity Solid Rheology and Texture Surface Properties Introduction to Thermodynamic and Thermal Properties Sensible and Latent Heat Changes Heat Transfer Mechanisms Unsteady-state Heat Transfer Properties of Gases and Vapours Electrical Properties Diffusion and Mass Transfer Bibliography and references Index.

Journal ArticleDOI
TL;DR: In this paper, an analysis for the forced convective flow of a gas through a packed bed of spherical solid particles, and the associated heat transport processes was presented, and it was shown that the local thermal equilibrium condition was very sensitive to the particle Reynolds number (Re{sub p}) and the Darcy number (Da) while thermophysical properties did not have a very significant effect on this condition.
Abstract: This paper presents an analysis for the forced convective flow of a gas through a packed bed of spherical solid particles, and the associated heat transport processes. Ergun's correlation was used as the vapor phase momentum equation in order to account for the inertia effects as well as the viscous effects. No local thermal equilibrium was assumed between the solid and the vapor phases. A thorough discussion of the thermal interactions between the solid and vapor phases and their effect on the fluid flow as well as the pressure and density fields is presented. The analysis shows that the local thermal equilibrium condition was very sensitive to the particle Reynolds number (Re{sub p}) and the Darcy number (Da) while thermophysical properties did not have a very significant effect on this condition. On the other hand, two-dimensional behavior of certain variables was found to be very sensitive to thermophysical parameters but insensitive to Re{sub p} and Da.

Journal ArticleDOI
TL;DR: In this article, Radiative exchanges are calculated with the assumption of diffuse surfaces and with use of a viewed and hidden part algorithm together with a Galerkin discretization.

Proceedings ArticleDOI
TL;DR: In this article, the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages were investigated with a large scale, multi-pass, smooth-wall heat transfer model with both radially inward and outward flow.
Abstract: Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large scale, multi-pass, smooth-wall heat transfer model with both radially inward and outward flow. An analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages (coolant-to-wall temperature ratio, Rossby number, Reynolds number and radius-to-passage hydraulic diameter ratio). These four parameters were varied over ranges which are typical of advanced gas turbine engine operating conditions. It was found that both Coriolis and buoyancy effects must be considered in turbine blade cooling designs and that the effect of rotation on the heat transfer coefficients was markedly different depending on the flow direction. Local heat transfer coefficients were found to decrease by as much as 60 percent and increase by 250 percent from no rotation levels. Comparisons with a pioneering stationary vertical tube buoyancy experiment showed reasonably good agreement. Correlation of the data is achieved employing dimensionless parameters derived from the governing flow equations.

Journal ArticleDOI
TL;DR: In this paper, the effect of a centered, square, heat-conducting body on natural convection in a vertical square enclosure was examined numerically and the analysis revealed that the fluid flow and heat transfer processes are governed by the Rayleigh and Prandtl numbers, the dimensionless body size, and the ratio of the thermal conductivity of the body to that of the fluid.
Abstract: The effect of a centered, square, heat-conducting body on natural convection in a vertical square enclosure was examined numerically. The analysis reveals that the fluid flow and heat transfer processes are governed by the Rayleigh and Prandtl numbers, the dimensionless body size, and the ratio of the thermal conductivity of the body to that of the fluid. For Pr = 0.71 and relatively wide ranges of the other parameters, results are reported in terms of streamlines, isotherms, and the overall heat transfer across the enclosure as described by the Nusselt number. Heat transfer across the enclosure, in comparison to that in the absence of a body, may be enhanced (reduced) by a body with a thermal conductivity ratio less (greater) than unity. Furthermore, the heat transfer may attain a minimum as the body size is increased. These and other findings are justified through a careful examination of the local heat and fluid flow phenomena.

Journal ArticleDOI
TL;DR: In this article, a model for the thermal evolution of the Martian mantle and core and for the evolution of its magnetic field is developed by expanding the planetary thermal history model of Stevenson et al. and using the energy balance equations from that work.
Abstract: A model for thermal evolution of the Martian mantle and core and for the evolution of the Martian magnetic field is developed by expanding the planetary thermal history model of Stevenson et al (1983) and using the energy balance equations from that work Several parameter values are chosen differently from those of the Stevenson model, including those for mantle density, core radius, core density, central pressure, and pressure at the core-mantle boundary The model is further modified to allow calculations of lithosphere thickness through time According to the model, the core contains a light alloying constituent, assumed to be sulfur The results of calculations show that a small Martian magnetic field can be generated by a weakly convecting liquid core


Journal ArticleDOI
TL;DR: A mathematical model was developed and tested to simulate the generation and transfer of heat in solid substrate fermentation (SSF) and it was shown that conduction through the fermentation fixed bed was the main heat transfer resistance.
Abstract: A mathematical model was developed and tested to simulate the generation and transfer of heat in solid substrate fermentation (SSF). The experimental studies were realized in a 1-L static bioreactor packed with cassava wet meal and inoculated with Aspergillus niger. A simplified pseudohomogeneous monodimensional dynamic model was used for the energy balance. Kinetic equations taking into account biomass formation (logistic), sugar consumption (with maintenance), and carbon dioxide formation were used. Model verification was achieved by comparison of calculated and experimental temperatures. Heat transfer was evaluated by the estimation of Biot and Peclet heat dimensionless numbers 5-10 and 2550-2750, respectively. It was shown that conduction through the fermentation fixed bed was the main heat transfer resistance. This model intends to reach a better understanding of transport phenomena in SSF, a fact which could be used to evaluate various alternatives for temperature control of SSF, i.e., changing air flow rates and increasing water content. Dimensionless numbers could be used as scale-up criteria of large fermentors, since in those ratios are described the operating conditions, geometry, and size of the bioreactor. It could lead to improved solid reactor systems. The model can be used as a basis for automatic control of SSF for the production of valuable metabolites in static fermentors.

Journal ArticleDOI
TL;DR: The response to a boundary heating of a very compressible, low-diffusivity, supercritical fluid under zero-gravity is studied by solving numerically the full non-linear one-dimensional Navier-Stokes equations.
Abstract: The response to a boundary heating of a very compressible, low-diffusivity, supercritical fluid (${\mathrm{CO}}_{2}$) under zero-gravity is studied by solving numerically the full non-linear one-dimensional Navier-Stokes equations. Both short (acoustic) and long (diffusion) time scales are investigated. A new mechanism of heat transport is seen, where the thermal energy is transformed into kinetic energy in a hot expanding boundary layer (the piston), which in turn is transformed in the bulk into internal energy. Steeply profiled waves are observed. In contrast to the ``critical slowing down'' behavior, the enhancement of heat transport is so important that it is nearly completed after 1% of the diffusion time.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the heat transfer coefficients on interior building surfaces (such as vertical walls, ceilings and glazing) using a real-sized indoor test cell which measures 2.95 × 2.08 m (length × width × height) and a total of 142 tests, each one lasting about 24 hours, were conducted under controlled steady-state conditions to cover nine of the most widely used heating configurations in buildings.


Journal ArticleDOI
TL;DR: In this article, an analytical model is presented that can be used to predict the heat-transfer characteristics of film evaporation on a microgroove surface, assuming that the liquid flow along a "V"-shaped groove channel is driven primarily by the capillary pressure difference due to receding of the meniscus toward the apex of the groove, and the flow up the groove side wall is driven by the disjoining pressure difference.
Abstract: An analytical model is presented that can be used to predict the heat-transfer characteristics of film evaporation on a microgroove surface. The model assumes that the liquid flow along a "V"-shaped groove channel is driven primarily by the capillary pressure difference due to the receding of the meniscus toward the apex of the groove, and the flow up the groove side wall is driven by the disjoining pressure difference. It also assumes that conduction across the thin liquid film is the dominant mechanism of heat transfer. A correlation between the Nusselt number and a nondimensional parameter ¥ is developed from this model which relates the heat transfer for the microgroove surface to the fluid properties, groove geometry, and the constants for the disjoining pressure relation. The results of a limited experimental study of the heat transfer during vaporization of a liquid coolant on a microgroove surface are also reported. Film-evaporation transfer coefficients inferred from these experiments are found to correlate fairly well in terms of Nusselt number and ¥ parameter format developed in the model. The results of this study suggest that disjoining pressure differences may play a central role in evaporation processes in microgroove channels.

Journal ArticleDOI
Abstract: The evolution of plane-parallel magnetized thermal conduction fronts in the interstellar medium (ISM) was studied. Separating the coronal ISM phase and interstellar clouds, these fronts have been thought to be the site of the intermediate-temperature regions whose presence was inferred from O VI absorption-line studies. The front evolution was followed numerically, starting from the initial discontinuous temperature distribution between the hot and cold medium, and ending in the final cooling stage of the hot medium. It was found that, for the typical ISM pressure of 4000 K/cu cm and the hot medium temperature of 10 to the 6th K, the transition from evaporation to condensation in a nonmagnetized front occurs when the front thickness is 15 pc. This thickness is a factor of 5 smaller than previously estimated. The O VI column densities in both evaporative and condensation stages agree with observations if the initial hot medium temperature Th exceeds 750,000 K. Condensing conduction fronts give better agreement with observed O VI line profiles because of lower gas temperatures.


Journal ArticleDOI
TL;DR: In this paper, the identification and quantification of conductive and convective components in the heat transfer of a sedimentary basin is demonstrated for the Rheingraben, and three different methods of varying complexity as well as three independent data sets are employed: (1) energy budget considerations based on hydraulically perturbed thermal data from shallow boreholes ( lo00 m), and (3) 2-D finite difference modelling of the fully coupled fluid flow and heat transport equations on a vertical cross-section of the entire Rheinraben.
Abstract: SUMMARY The identification and quantification of conductive and convective components in the heat transfer of a sedimentary basin is demonstrated for the Rheingraben. Three different methods of varying complexity as well as three independent data sets are employed: (1) energy budget considerations based on hydraulically perturbed thermal data from shallow boreholes ( lo00 m), and (3) 2-D finite difference modelling of the fully coupled fluid flow and heat transport equations on a vertical cross-section of the entire Rheingraben. Energy budget considerations yield a conductive basal heat flow density of 84 + 40/-10 mW mP2, and in good agreement with this Peclet number analysis, gives median values in the range 90 f 35 mW m-’. In the first case, the basement is formed by low permeable, tertiary sediments at about 500 m depth, and in the second by the transition from the sedimentary graben fill to the crystalline basement at depths of between 2000 and 4000m. It is shown how results from numerical modelling support the flow field assumptions made by methods (1) and (2), as well as the value of 80 f 10 mW m-’ for average basal heat flow density entering the graben from below. Conversely, the Peclet number range Pe I 1.2 inferred from method (2) can be applied for a (at least partial) calibration of the fully coupled hydrothermal model calculatioris. This technique is suggested as a potentially interesting thermal method for constraining regional-scale permeability. An interpretation of heat transport is presented that satisfies the experimentally established patterns of both temperature and heat flow density in the Rheingraben. Moreover, it is demonstrated that the thermal anomalies along the western rim of the graben (such as Pechelbronn, France or Landau, Germany) can be convincingly explained by a basin-wide, deep rooted E-W groundwater circulation that locally enhances a background basal heat flow density of about 80 mW m-’ on average by 50 per cent and at individual sites by as much as 120 per cent.

Journal ArticleDOI
TL;DR: In this article, the effects of operating conditions, reactor geometry, and heat transfer characteristics on flow patterns and growth rate uniformity in vertical, axisymmetric reactors for metalorganic vapor phase epitaxy (MOVPE) are described.

Journal ArticleDOI
TL;DR: In this paper, the performance of a class of irreversible Carnot refrigeration cycles operating between two heat reservoirs at a low temperature TL and a high temperature TH, for which the only irreversibility results from the finite rate of heat conduction, is studied.
Abstract: The performance of a class of irreversible Carnot refrigeration cycles operating between two heat reservoirs at a low temperature TL and a high temperature TH, for which the only irreversibility results from the finite rate of heat conduction, is studied. The relation between the optimal rate of refrigeration and the coefficient of performance of these cycles is derived, based on a general heat transfer law. Moreover, the optimal performance of these cycles is discussed and the effect of different heat transfer laws on the optimal performance is investigated. Consequently, some new and useful results for refrigeration cycles are obtained.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the heat transfer and pressure drop characteristics of a circular tube fitted with regularly spaced twisted-tape elements connected by thin circular rods and found that the regularly spaced tape elements performed significantly better than full-length twisted tapes at high Reynolds numbers, high twists, and small spacings.

Journal ArticleDOI
TL;DR: In this article, the authors presented evaporation and boiling heat transfer coefficients for thin, distilled water films flowing over the outside of horizontal, electrically heated brass tubes for thin-slot water distribution system for 2.54 and 5.08-cm-dia smooth tubes.
Abstract: Evaporation and boiling heat transfer coefficients are presented for thin, distilled water films flowing over the outside of horizontal, electrically heated brass tubes. Tests were conducted with a thin-slot water distribution system for 2.54- and 5.08-cm-dia smooth tubes. Both local and average heat transfer data were obtained for nonboiling and boiling conditions corresponding to feedwater temperatures ranging from 49 to 127C and heat-flux values ranging from 30 to 80 kW/m{sup 2}. Feedwater flow rates ranged from 0.135 to 0.366 kg/s per meter length per side of the tube. Both nonboiling and boiling correlations of the average heat transfer coefficients were developed and compared.