Showing papers in "Journal of Heat Transfer-transactions of The Asme in 1990"
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
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
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
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.
258 citations
211 citations
TL;DR: In this article, a new temperature-based fixed-grid formulation is proposed, and the reason that the original equivalent heat capacity model is subject to such restrictions on the time step, mesh size and the phase-change temperature range is discussed.
Abstract: Fixed grid solutions for phase-change problems remove the need to satisfy conditions at the phase-change front and can be easily extended to multidimensional problems. The two most important and widely used methods are enthalpy methods and temperature-based equivalent heat capacity methods. Both methods in this group have advantages and disadvantages. Enthalpy methods (Shamsundar and Sparrow, 1975; Voller and Prakash, 1987; Cao et al., 1989) are flexible and can handle phase-change problems occurring both at a single temperature and over a temperature range. The drawback of this method is that although the predicted temperature distributions and melting fronts are reasonable, the predicted time history of the temperature at a typical grid point may have some oscillations. The temperature-based fixed grid methods (Morgan, 1981; Hsiao and Chung, 1984) have no such time history problems and are more convenient with conjugate problems involving an adjacent wall, but have to deal with the severe nonlinearity of the governing equations when the phase-change temperature range is small. In this paper, a new temperature-based fixed-grid formulation is proposed, and the reason that the original equivalent heat capacity model is subject to such restrictions on the time step, mesh size, and the phase-change temperature range will alsomore » be discussed.« less
167 citations
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.
142 citations
TL;DR: In this article, the effects of array configuration and pin-endwall fillet on the heat transfer and pressure drop of short pin-fin arrays are investigated experimentally, including an in-line and a staggered array, each having seven rows of five pins.
Abstract: The effects of array configuration and pin-endwall fillet on the heat transfer and pressure drop of short pin-fin arrays are investigated experimentally. The pin-fin element with endwall fillet, typical in actual turbine cooling applications, is modeled by a spool-like cylinder. The arrays studied include an in-line and a staggered array, each having seven rows of five pins
131 citations
TL;DR: In this article, a general flow model that accounts for the effects of the impermeable boundary and inertia is used to describe the flow inside the porous region and the dependence of these characteristics on the governing parameters such as the Darcy number, the inertia parameter, the Prandtl number and the ratio of the conductivity of the porous material to that of the fluid is also documented.
Abstract: Convective flow and heat transfer through a composite porous/fluid system have been studied numerically. The composite medium consists of a fluid layer overlaying a porous substrate, which is attached to the surface of the plate. The numerical simulations focus primarily on flows that have the boundary layer characteristics. However, the boundary layer approximation was not used. A general flow model that accounts for the effects of the impermeable boundary and inertia is used to describe the flow inside the porous region. Several important characteristics of the flow and temperature fields in the composite layer are reported. The dependence of these characteristics on the governing parameters such as the Darcy number, the inertia parameter, the Prandtl number, and the ratio of the conductivity of the porous material to that of the fluid is also documented. The results of this investigation point out a number of interesting practical applications such as in frictional drag reduction, and heat transfer retardation or enhancement of an external boundary.
126 citations
TL;DR: An analytical solution for the temperature profile in a semi-infinite body with an exponentially decaying (with position) source and convective boundary condition using Laplace transforms is obtained in this article.
Abstract: An analytical solution for the temperature profile in a semi-infinite body with an exponentially decaying (with position) source and convective boundary condition is obtained using Laplace transforms. The appropriate dimensionless parameters are identified and the temperature as a function of these parameters is presented in graphic form. With cooling at the exposed surface, the maximum temperature occurs in the interior of the slab instead of at the exposed surface. The location of the temperature maximum as a function of the various system parameters is presented in graphic form. Approximate relationships are presented for small values of dimensionless time.
119 citations
TL;DR: In this article, an experimental investigation is described that characterizes the convective heat transfer of a heated circular air jet impinging on a flat surface and the radial distributions of the recovery factor, the effectiveness, and the local heat transfer coefficient are presented.
Abstract: An experimental investigation is described that characterizes the convective heat transfer of a heated circular air jet impinging on a flat surface. The radial distributions of the recovery factor, the effectiveness, and the local heat transfer coefficient are presented. The recovery factor and the effectiveness depend on the spacing from jet exit to the impingement plate, but do not depend on jet Reynolds number. The effectiveness does not depend on the temperature difference between the jet and the ambient. A correlation is obtained for the effectiveness. The heat transfer coefficient is independent of the temperature difference between the jet and the ambient if it is defined with the difference between the heated wall temperature and the adiabatic wall temperature.
TL;DR: In this paper, the authors investigated single-phase heat transfer from a smooth 12.7 mm-sup 2 -simulated chip to a two-dimensional jet of dielectric Fluorinert FC-72 liquid issuing from a thin rectangular slot into a channel confined between the chip surface and nozzle plate.
Abstract: Experiments were performed to investigate single-phase heat transfer froma smooth 12.7 {times} 12.7 mm{sup 2} simulated chip to a two-dimensional jet of dielectric Fluorinert FC-72 liquid issuing from a thin rectangular slot into a channel confined between the chip surface and nozzle plate. The effects of jet width, confined channel height, and impingement velocity have been examined. Channel height had a negligible effect ont eh theat transfer performance of the jet for the conditions of the present study. A correlation for the convective heat transfer coefficient is presented as a function of jet, width, heat length, flow velocity, and fluid properties. A self-contained multichip cooling module consisting of a 3 {times} 3 array of heat sources confirmed the uniformity and predictability of cooling for each of the nine chips, and proved the cooling module is well suited for packaging large arrays of high-power density chips.
TL;DR: In this paper, the authors derived critical Rayleigh numbers for the onset of convection and examined the steady flow patterns at moderately supercritical Rayleigh number for horizontal rectangular channels filled by isotropic and anisotropic porous media.
Abstract: This paper is an analytical study on natural two-dimensional convection in horizontal rectangular channels filled by isotropic and anisotropic porous media. The channel walls, assumed to be impermeable and perfectly heat conducting, are nonuniformly heated to establish a linear temperature distribution in the vertical direction. The authors derive the critical Rayleigh numbers for the onset of convection and examine the steady flow patterns at moderately supercritical Rayleigh numbers. The stability properties of these flow patterns are examined against two-dimensional perturbations using a weakly nonlinear theory.
TL;DR: In this paper, the phonon mean free path in polycrystalline ceramic YBa{sub 2}Cu{sub 3}O{sub 7} can be approximated using the kinetic theory approximation and reported data.
Abstract: Using the kinetic theory approximation and reported data, this study shows that at low temperatures, the phonon mean free path in polycrystalline ceramic YBa{sub 2}Cu{sub 3}O{sub 7} can be of the order of the thickness of thin-film superconductors. In this case, boundary scattering reduces the thermal conductivity with decreasing film thickness. A simple method accounts for the size effect on conduction in thin films. This analysis rests solely on geometric arguments and does not consider the effect of grain boundaries. For conduction along the film, this model approximates well an analytical solution of Boltzmann transport equation, and is in good agreement with experimental data for thin lead films. The model is also employed to analyze the size effect on conduction across the film and the influence of anisotropy.
TL;DR: In this article, a high-purity copper sphere was plunged into cooling baths without boiling and the sphere was instrumented with several interior thermocouples for measuring the transient temperature response during quenching.
Abstract: Methodological and experimental aspects of the estimation of transient heat transfer coefficients in quenching experiments, using inverse heat transfer methods, were addressed and investigated. Beck's method was used for the estimation of the transient heat transfer coefficient history from interior transient temperature measurements during quenching. Experiments involved plunging a high-purity copper sphere into cooling baths without boiling. The sphere was instrumented with several interior thermocouples for measuring the transient temperature response during quenching. Water and ethylene glycol were investigated. The early transient values of the heat transfer coefficient history were found to be about 100-120% higher than the values predicted using well-known empirical correlations for free convection. The later time values were in good agreement with those predicted with empirical correlations. The transient inverse technique has the capability of estimating early transients and subsequent quasi-steady-state values of heat transfer coefficient in a single transient experiment.
TL;DR: In this paper, an analytical model to evaluate the dependent absorption and extinction characteristics of dense particulate systems is presented, where simple expressions are obtained by considering statistical averages based on the random character of the particulate medium.
Abstract: This study presents an analytical model to evaluate the dependent absorption and extinction characteristics of dense particulate systems. Simple expressions are obtained by considering statistical averages based on the random character of the particulate medium. Departure from the assumption of independent scattering and absorption of radiation originates from two mechanisms; perturbation of the internal field of each particle by the presence of other particles, and coherent addition (i.e., taking into account the constructive/destructive interference) of the far-field scattered radiation. Dependent scattering has been previously studied analytically by considering the second mechanism only. Dependent absorption, which is due to the former, has not been considered in the literature even though absorption is more important than scattering in the extinction of radiation by small (Rayleigh) absorbing particles.
TL;DR: In this paper, the authors investigated two-dimensional natural convection in a vertical differentially heated air-filled cavity and found several branches of solutions characterized by different numbers of cells in the flow structure.
Abstract: Two-dimensional natural convection in a vertical differentially heated air-filled cavity is investigated numerically from the onset of the multicellular flow structure to the return of the unicellular pattern. Several branches of solutions characterized by different numbers of cells in the flow structure are found. The return to the unicellular flow structure occurs through a gradual decrease in the number of cells and each change in the number of cells is characterized by hysteresis. Also, unsteady solutions are found.
TL;DR: In this paper, a rigorous numerical solution of a theoretical model based on laminar boundary layer theory for pool film boiling heat transfer from a horizontal cylinder including the contributions of liquid subcooling and radiation from the cylinder was obtained.
Abstract: A rigorous numerical solution of a theoretical model based on laminar boundary layer theory for pool film boiling heat transfer from a horizontal cylinder including the contributions of liquid subcooling and radiation from the cylinder was obtained. The numerical solution predicted accurately the experimental results of pool film boiling heat transfer from a horizontal cylinder in water with high radiation emissivity for a wide range of liquid subcooling in the range of nondimensional cylinder diameters around 1.3, where the numerical solution was applicable to the pool film boiling heat transfer from a cylinder with negligible radiation emissivity. An approximate analytical solution for the theoretical model was also derived. It was given by the sum of the pool film boiling heat transfer coefficient if there were no radiation and the radiation heat transfer coefficient for parallel plates multiplied by a nondimensional radiation parameter similar to the expression for saturated pool film boiling given by Bromley. The approximate analytical solution agreed well with the rigorous numerical solution for various liquids of widely different physical properties under wide ranges of conditions.
TL;DR: In this article, the authors showed that a small amount of surface active additive makes the nucleate boiling heat transfer coefficient h considerably higher, and that there is an optimum additive concentration for higher heat fluxes.
Abstract: In the first part of this work, nucleate boiling of aqueous solutions of sodium lauryl sulfate (SLS) over relatively wide ranges of concentration and heat flux was carried out in a pool boiling apparatus. The experimental results show that a small amount of surface active additive makes the nucleate boiling heat transfer coefficient h considerably higher, and that there is an optimum additive concentration for higher heat fluxes. Beyond this optimum point, further increase in additive concentration makes h lower. In the second part of this work, nucleate boiling heat transfer rate for n-propanol-water binary mixtures with various amounts of sodium lauryl sulfate were measured in the same pool boiling apparatus. The importance of the mass diffusion effect, which is caused by preferential evaporation of the more volatile component at the vapor-liquid interface on the boiling of the binary mixture, has been confirmed. However, it is shown that the effect exerted by the addition of a surfactant dominates over the mass diffusion effect in dilute binary mixtures.
TL;DR: In this article, a series of tests were performed to determine the evaporation and condensation performance of three 12.7mm o.d. tubes, referred to as microfin tubes, having many small, spiral inner fins.
Abstract: Using R-22 as the working fluid, a series of tests was performed to determine the evaporation and condensation performance of three 12.7-mm o.d. tubes having many small, spiral inner fins. The tubes, referred to as microfin tubes, had a 11.7-mm maximum i.d., 60 or 70 fins with heights ranging from 0.15 to 0.30 mm, and spiral angles from 15 to 25 deg. A smooth tube was also tested to establish a basis of comparison. The test apparatus had a straight, horizontal test section with a length of 3.67 m and was heated or cooled by water circulated in a surrounding annulus. Nominal evaporation conditions were 0 to 5C (0.5 to 0.6 MPa) with inlet and outlet qualities of 15 and 85%, respectively; condensation condition were 39 to 42C (1.5 to 1.6 MPa) with inlet and outlet qualities of 85 and 10%, 39 to 42C (1.5 to 1.6 MPa) with inlet and outlet qualities of 85 and 10%, 39 to 42C (1.5 to 1.6 MPa) with inlet and outlet qualities of 85 and 10%, 39 to 42 C (1.5 to 1.6 MPa) with inlet and outlet qualities of 85 and 10%, respectively. mass flux varied from 75 to 400 kg/m{sup 2}{centermore » dot}s. The average heat transfer coefficients in the microfin tubes, based on nominal equivalent smooth tube area, were 1.6 to 2.2 times larger for evaporation and 1.5 to 2.0 times larger for condensation than those in the smooth tube. The pressure drop increased, but by a smaller factor than the heat transfer coefficient.« less
TL;DR: In this article, the start-up process of a frozen heat pipe is described and a complete mathematical model is developed based on the existing experimental data, which is simplified and solved numerically.
Abstract: The start-up process of a frozen heat pipe is described and a complete mathematical model for the start-up of the frozen heat pipe is developed based on the existing experimental data, which is simplified and solved numerically. The two-dimensional transient model for the wall and wick is coupled with the one-dimensional transient model for the vapor flow when vaporization and condensation occur at the interface. A parametric study is performed to examine the effect of the boundary specification at the surface of the outer wall on the successful start-up from the frozen state. For successful start-up, the boundary specification at the outer wall surface must melt the working substance in the condenser before dry-out takes place in the evaporator.
TL;DR: In this paper, the experimental data of pool film boiling heat transfer from horizontal cylinders in various liquids such as water, ethanol, isopropanol, Freon-113 and liquid nitrogen, and liquid argon are reported.
Abstract: Experimental data of pool film boiling heat transfer from horizontal cylinders in various liquids such as water, ethanol, isopropanol, Freon-113, Freon-11, liquid nitrogen, and liquid argon for wide ranges of system pressure, liquid subcooling, surface superheat and cylinder diameter are reported. These experimental data are compared with a rigorous numerical solution and an approximate analytical solution derived from a theoretical model based on laminar boundary layer theory for pool film boiling heat transfer from horizontal cylinders including the effects of liquid subcooling and radiation from the cylinder. A new correlation was developed by slightly modifying the approximate analytical solution to agree better with the experimental data. The values calculated from the correlation agree with the authors data within {plus minus} 10%, and also with other researchers data for various liquids including those with large radiation effects, though these other data were obtained mainly under saturated conditions at atmospheric pressure.
TL;DR: In this paper, the authors presented the entropy generation (irreversibility) concept as a convenient method for estimating the quality of the heat exchange process in heat exchanger analysis.
Abstract: This paper presents the entropy generation (irreversibility) concept as a convenient method for estimating the quality of the heat exchange process in heat exchanger analysis. The entropy generation caused by finite temperature differences, scaled by the maximum possible entropy generation that can exist in an open system with two fluids, is used as the quantitative measure of the quality of energy transformation (the heat exchange process). This measure is applied to a two-fluid heat exchanger of arbitrary flow arrangement. The influence of different parameters (inlet temperature ratio, fluid flow heat capacity rate ratio, flow arrangements) and the heat exchanger thermal size (number of heat transfer units) on the quality of energy transformation for different types of heat exchangers is discussed. In this analysis it is assumed that the contribution of fluid friction to entropy generation is negligible.
TL;DR: In this article, the relative values of required hydraulic diameter, frontal area, total volume, pumping power, and number of transfer units for different heat transfer surface configurations were derived and displayed.
Abstract: This paper presents a family of methods for comparing compact heat transfer surface configurations It is shown how measures for the relative values of required hydraulic diameter, frontal area, total volume, pumping power, and number of transfer units for different surfaces can be derive and displayed, when any two of the above five parameters are held constant A wide range of comparisons that are independent of the particular duty can be simply made A further development allowing comparisons, where three of the five parameters are fixed, yields very clear and compact indications of the relative merits of different surfaces
TL;DR: In this article, the authors proposed a technique to reduce the integro-differential equation to a system of ordinary differential equations, which utilizes readily available software routines to solve the resulting set of coupled first-order ODEs as a two-point boundary value problem.
Abstract: This paper introduces a powerful but simple methodology for solving the general equation of radiative transfer for scattering and/or absorbing one-dimensional systems Existing methods, usually designed to handle specific boundary and energy equilibrium conditions, either provide crude estimates or involve intricate mathematical analysis coupled with numerical techniques In contrast, the present scheme, which uses a discrete-ordinate technique to reduce the integro-differential equation to a system of ordinary differential equations, utilizes readily available software routines to solve the resulting set of coupled first-order ordinary differential equations as a two-point boundary value problem The advantage of this approach is that the user is freed from having to understand complicated mathematical analysis and perform extensive computer programming Additionally, the software used is state of the art, which is less prone to numerical instabilities and inaccuracies Any degree of scattering anisotropy and albedo can be incorporated along with different conditions of energy equilibrium or specified temperature distributions and boundary conditions Examples are presented where the radiative transfer is computed by using different quadratures such as Gaussian, Lobatto, Fiveland, Chebyshev, and Newton-Cotes Comparison with benchmark cases shows that in a highly forward scattering medium Gaussian quadrature provides the most accurate and stable solutions
TL;DR: In this article, an experimental investigation into the effect of an electric field applied to pool boiling of Freon (R114) on a finned tube and a theoretical model of electrically enhanced nucleate boiling applicable to simple surfaces was presented.
Abstract: This paper describes: (a) an experimental investigation into the effect of an electric field applied to pool boiling of Freon (R114) on a finned tube and (b) a theoretical model of electrically enhanced nucleate boiling applicable to simple surfaces only. Experimental results have shown electrohydrodynamic (EHD) enhancement of heat transfer to be manifest in two ways: (1) elimination of boiling hysteresis, (2) augmentation of nulceate boiling heat transfer coefficients by up to an order of magnitude. These effects were also observed in electrically enhanced boiling of Freon/oil mixtures. A new analytical model is described whereby EHD nucleate boiling data from previous studies (employing simple apparatus comprising heated wires with concentric cylinder electrodes) have been correlated for the first time using the concept of an electrical influence number. This dimensionless parameter is based upon the relationship between applied electric field intensity and changes in bubble departure diameter at a heat transfer surface.
TL;DR: In this article, Lykoudis et al. showed that in low-Pr fluids the laminar flow expires at unexpectedly low Rayleigh numbers, whereas in high-Pr fluid the transition Rayleigh number is higher than 10{sup 9.
Abstract: As is often the case, the decision to embark on a new project was triggered by a set of coincidental and mutually reinforcing observations: (i) There is a definite lack of information (theoretical, numerical, experimental) on natural convection in low-Pr fluids (Lykoudis, 1989). This observation was stressed recently also by Wolff et al. (1988). (ii) Georgiadis (1989) drew attention to the line of work represented by Chao et al. (1982) and Bertin and Ozoe (1986), who showed numerically that the onset of Benard convection appears to be influence by the Prandtl number in the Pr < 1 range. (iii) The authors were struck by Bertin and Ozoe's (1986) discovery that they were unable to obtain numerically a steady flow below a certain Prandtl number (Pr = 0.001), even though the Rayleigh number based on height seemed sufficiently low (Ra = 2,800). The present study was motivated by these observations and the apparent suggestion that in low-Pr fluids the laminar flow expires at unexpectedly low Rayleigh numbers. This idea is particularly interesting if they think of the natural convection boundary layer near a vertical wall, for which the textbook teaches to associate the constant Ra {approx} 10{sup 9} with the heightmore » of transition to the turbulent flow, regardless of the Prandtl number (e.g., Incropera and DeWitt, 1985, p. 427). In order to test this idea, the authors reexamined the experimental record of observations on transition in vertical natural convection boundary layer flow. Indeed, the empirical data described next show that the Prandtl number has a strong influence on the transition Rayleigh number. In low-Pr fluids the transition occurs at Rayleigh numbers much lower than the often-mentioned Ra {approx} 10{sup 9}, while in high-Pr fluids the transition Rayleigh number is higher than 10{sup 9}. It appears that the constant Grashof number Gr {approx} 10{sup 9} (i.e., not Ra {approx} 10{sup 9}) marks the transition in the wide Pr range 0.001-1000.« less
TL;DR: In this paper, the transient analysis of the behavior of a packed bed of encapsulated phase change material and the condensing flow through it is presented and compared for a sensible heat storage material as well as for different latent heat storage materials (PCMs).
Abstract: In this work the transient analysis of the behavior of a packed bed of encapsulated phase change material (PCM) and the condensing flow through it is presented. The rigorous model used assumes no local thermal equilibrium between the bed particles and working fluid, and incorporates the inertia effects int eh momentum transport by the use of the Ergun-Forchheimer equation. Condensation in the working fluid is investigated. Thermal charging of the packed bed is analyzed and compared for a sensible heat storage material as well as for different latent heat storage materials (PCMs).
TL;DR: In this paper, the dynamics and tendency toward rupture of thin evaporating liquid films on a heated surface are discussed. And the connection between forced-convection subcooled nucleate boiling and thin-film heat transfer is discussed.
Abstract: This review covers the dynamics and tendency toward rupture of thin evaporating liquid films on a heated surface. Very large heat transfer coefficients can be obtained. The applications include various boiling heat transfer and film cooling devices. A relatively new area for study is heat transfer through ultrathin films, which are less than 100 nm in thickness, and hence subject to van der Waals and other long-range molecular forces. Some recent work employing lubrication theory to obtain an evolution equation for the growth of a surface wave is described. Earlier phenomenological work is briefly discussed, as well as the connection between forced-convection subcooled nucleate boiling and thin-film heat transfer.