Showing papers on "Heat transfer published in 1991"
TL;DR: The authors showed that the eonvective term in the correlation should have a Prandtl number dependence and constructed an accurate predictive method with an explicit nucleate boiling term and without boiling number dependence.
803 citations
TL;DR: In this article, the concept of characteristic length introduced in the definition of the dynamic tortuosity by Johnson, Koplik, and Dashen is extended to express the frequency dependence of the bulk modulus of the saturating fluid at high frequencies.
Abstract: In this paper, the concept of characteristic length introduced in the definition of the dynamic tortuosity by Johnson, Koplik, and Dashen [J. Fluid Mech. 176, 379 (1987)] is extended to express the frequency dependence of the bulk modulus of the saturating fluid at high frequencies. A general phenomenological frequency dependence for this dynamic bulk modulus is obtained using the expression for the dynamic tortuosity. The theoretical predictions for dynamic tortuosity and bulk modulus are compared with experimental results obtained from acoustic measurements on a rigid‐frame porous material saturated with air.
751 citations
01 Jan 1991
TL;DR: In this article, the authors discuss industrial applications of fluidized beds; the dense bed: distributors, gas jets, and pumping power; Bubbling fluidization beds; and particle movement in beds.
Abstract: The book covers fluidization engineering. Topics covered include: Industrial applications of fluidized beds; The dense bed: distributors, gas jets, and pumping power; Bubbling fluidized beds. High-velocity fluidization; Particle-to-gas mass and heat transfer; Conversion of gas in catalytic reactions; Heat transfer between fluidized beds and surfaces; Circulation systems. Design of catalytic reactors. Reviews principles and applications of fluidization engineering; coverage of historical and current research influencing the development of this engineering field; bed-wall heat transfer; drying of solids, fast fluidization, heat exchangers, K-L model for catalytic reactions, mass transfer, and particle movement in beds.
571 citations
TL;DR: In this paper, an endoreversible Carnot-type heat engine was studied under the usual restrictions: no friction, working substance in internal equilibrium (endoreversibility), no mechanical inertial effects, and under Newton's cooling law for heat transfer between working fluid and heat reservoirs.
Abstract: An endoreversible Carnot‐type heat engine is studied under the usual restrictions: no friction, working substance in internal equilibrium (endoreversibility), no mechanical inertial effects, and under Newton’s cooling law for heat transfer between working fluid and heat reservoirs. A monoparametric family of straight lines which is isoefficient is found; i.e., all points (engine configurations) that belong to same line have the same efficiency. Along each line the power output divided by entropy production is a constant. From these properties and by using some dissipated quantities, relationships are obtained between reversible work and finite‐time work and between reversible efficiency and finite‐time efficiency. An ‘‘ecological’’ criterion is proposed for the best mode of operation of this heat engine. It consists in maximizing a function representing the best compromise between power and the product of entropy production and the cold reservoir temperature. The corresponding efficiency results almost equal to the average of the Carnot and the Curzon and Ahlborn [Am. J. Phys. 43, 22 (1975)] efficiencies.
483 citations
TL;DR: In this article, a pseudo-spectral Chebyshev algorithm was used to solve the equations of natural convection in a 2D differentially heated cavity with adiabatic top and bottom walls for values of Ra up to 108.
416 citations
TL;DR: In this article, the heat transfer characteristics of microencapsulated phase change material slurry flow in circular ducts are presented by taking into consideration both the heat absorption (or release) due to the phase change process and the conductivity enhancement induced by the motion of the particles.
310 citations
TL;DR: In this paper, an investigation into the two-dimensional cure simulation of thick thermosetting composites is presented, where temperature and degree of cure distributions within arbitrary cross-sectional geometries are predicted as a function of the autoclave temperature history.
Abstract: An investigation into the two-dimensional cure simulation of thick thermosetting composites is presented. Temperature and degree of cure distributions within arbitrary cross-sectional geometries are predicted as a function of the autoclave temperature history. The heat conduction equation for two-dimensional, transient anisotropic heat transfer is coupled to the cure kinetics of the thermosetting composite material. A heat generation term, expressed as a function of cure rate and the total heat of reaction, is introduced to account for the heat liberated during the curing process. A generalized boundary condition formulation is employed, enabling arbitrary temperature boundary conditions to be enforced straightforwardly. An incremental, transient finite difference solution scheme is implemented to solve the pertinent governing equations and boundary conditions. The boundary-fitted coordinate system (BFCS) transformation technique is combined with the Alternating Direction Explicit (ADE) finite difference ...
279 citations
Book•
01 Jan 1991
TL;DR: In this article, the authors present a detailed overview of the laser mining process and its application in the field of laser mining applications, including heat transfer and fluid mechanics for laser machining.
Abstract: Contents: Overview of Machining Processes.- Lasers for Machining.- Basics of Laser Machining.- Heat Transfer and Fluid Mechanics for Laser Machining.- Laser Machining Analysis.- Laser Machining Applications.
274 citations
TL;DR: In this article, the laminar and turbulent flow in a two-dimensional square cavity heated from the vertical side is numerically calculated up to a Rayleigh number of 1014 for air and up to 1015 for water.
262 citations
TL;DR: In this paper, the authors introduce various types of condensation and examine the surface wettability of the surface and discuss the transport process at the vapor-liquid interface and the arguments on whether the condensation coefficient takes the value of unity are discussed.
Abstract: Publisher Summary Condensation represents the change of phase from the vapor state to the liquid state because of cooling. It is considered one of the most important heat-transfer processes in many energy-conversion systems, such as electric power generation plants. This chapter emphasizes on the areas of condensation heat transfer that have made progress in the past 15 years. It introduces various types of condensation and examines the wettability of the surface. The transport process at the vapor-liquid interface and the arguments on whether the condensation coefficient takes the value of unity are discussed. Furthermore, the chapter reviews dropwise condensation and film condensation in detail. It also describes the techniques of enhancement of condensation heat transfer. The usage of surface tension force is one of the most sophisticated ways for augmentation of condensation because it does not require extra energy. The chapter concludes with discussion of future trends in research on condensation heat transfer.
TL;DR: Continuous wave and pulsed laser ablation of tissue is described as an explosive event and a decrease in water content dramatically alters the local rate of heat generation of laser radiation above 1.3 μm since water is the primary absorber.
Abstract: Continuous wave and pulsed laser ablation of tissue is described as an explosive event. A subsurface temperature maximum and superheated tissue produce high pressures that eject fragments from the tissue. Decreased water content due to dehydration and vaporization decreases thermal conductivity which reduces heat conduction. Also, a decrease in water content dramatically alters the local rate of heat generation of laser radiation above 1.3 microns since water is the primary absorber. In contrast, at UV wavelengths protein and DNA are the primary absorbers so destruction of tissue bonds is due to direct absorption of the laser light rather than heat transfer from water.
TL;DR: In this article, the authors characterized local heat transfer coefficients for round, single-phase free liquid jets impinging normally against a flat uniform heat flux surface, and found that the local Nusselt number characteristics were dependent on nozzle diameter.
Abstract: The purpose of this investigation was to characterize local heat transfer coefficients for round, single-phase free liquid jets impinging normally against a flat uniform heat flux surface. The problems parameters investigated were jet Reynolds number Re, nozzle-to-plate spacing z, and jet diameter d. A region of near-constant Nusselt number was observed for the region bounded by 0 {le} r/d {le} 0.75, where is the radical distance from the impingement point. The local Nusselt number profiles exhibited a sharp drop for r/d > 0.75, followed by an inflection and a shower decrease thereafter. Increasing the nozzle-to-plate spacing generally decreased the heat transfer slightly. The local Nusselt number characteristics were found to be dependent on nozzle diameter. This was explained by the influence of the free-stream velocity gradient on local heat transfer, as predicted in the classical analysis of infinite jet stagnation flow and heat transfer. Correlations for local and average Nusselt numbers reveal an approximate Nusselt number dependence on Re{sup 1,3}.
TL;DR: In this article, the problem of dimensionless thermal resistance in closed finned channels was generalized with a statement of the number of channels and the ratio of the heat source to the cooling channel.
Abstract: For fully developed flow in closed finned channels used to augment heat transfer, there exists an optimal geometrical design of the size and number of cooling channels. In this paper, the problem is generalized with a statement of dimensionless thermal resistance in terms of 9 the number of channels 9 a fin to channel thickness ratio 8 the length to width {planar dimensions) ratio of the heat source, and 9 a specified fin efficiency or fin length 9 a fluid to fin thermal conductivity ratio 9 the Prandtl Number of the coolant 8 a dimensionless pressure term, which incorporates the maximum allowable pressure drop through the cooling channels or alternatively, 9 a dimensionless work rate term, which incorporates the maximum allowable cool ant pumping power required, An optimization scheme is described and used for comparison with two previously published cases wherein both designs were restricted to a fixed fin to channel thickness ratio and laminar flow; one by Goldberg (1984) using air and copper and a second one only by Tuckerman and Pease (1981) for water-cooled Silicon wafers. Results from the present optimization scheme show that upon reexamination of the first study by Goldberg, significant reduction of thermal resistance can be obtained by using fin/channel dimensions other than unity. A similar reduction is found in the second instance (Tuckerman and Pease) with the relaxation of the laminar limitation.
TL;DR: Triangular and rectangular longitudinal vortex generators were formed by punching small pieces out of flat plate fins so that they stuck out of the plates and formed an angle (angle of attack) with the main flow direction.
TL;DR: In this paper, the surface curvature effects on the impingement cooling flow and the heat transfer processes over a concave and a convex surface were investigated, where an electrical resistance wire is used to generate smoke and the local heat transfer Nusselt number along the surfaces is measured.
Abstract: Experiments are performed to study 'surface curvature effects on the impingement cooling flow and the heat transfer processes over a concave and a convex surface. A single air jet issuing from different size slots continuously impinges normally on the concave side or the convexside of a heated semicylindrical surface. An electrical resistance wire is used to generate smoke, which allows us to visualize the impinging flow structure. The local heat transfer Nusselt number along the surfaces is measured. For impingement on a convex surface, three-dimensional counterrotating vortices on the stagnation point are initiated, which result in the enhancement of the heat transfer process. For impingement on a concave surface, the heat transfer Nusselt number increases with increasing surface curvature, which suggests the initiation of Taylor-Gortler vortices along the surface. In the experiment, the Reynolds number ranges from 6000 to 350,000, the slot-to-plate spacing from 2 to 16, and the diameter-to-slot-width ratio D/b from 8 to 45.7. Correlations of both the stagnation point and the average Nusselt number over the curved surface, which account for the surface curvature effect, are presented. 1 Introduction Impingement cooling has been widely used to cool a heat transfer component exposed to a high temperature or a high heat flux environment. The impingement cooling jet has the advantage that it is readily moved to the location of interest and removes a large amount of heat. It has been widely used in such industrial systems as high-temperature gas turbines, paper drying, glass manufacturing, and high-density electronic equipment. The impinging jet used in these systems is air. Over the past 30 years, impingement cooling heat transfer has been extensively studied. Good review articles are available (Martin, 1977; Becko, 1976). The impinging flow structure (Donaldson and Snedeker, 1971a, 1971b), the local heat transfer, and the correlations of average Nusselt number in terms of relevant parameters have been well studied (Gardon and Cobonpue, 1963; Gardon and Akfirat, 1966; Korger and Krizek, 1965; Zumbrunnen et al., 1989). However, the impingement cooling studied in the past was on a flat plate. The situation of impingement cooling over a curved surface may frequently be encountered. However, the studies of impingement cooling on a curved surface are relatively few. Chupp et al. (1969) studied the impingement cooling heat transfer for an array of round jets impinging on a concave surface. The geometric configuration studied is very similar to the case for cooling of the leading edge of a gas turbine airfoil. They measure the local Nusselt number and correlate the average Nusselt number in terms of the Reynolds number, the nozzle-to-plate spacing, and some nondimensional parameters of geometry. However, the local heat transfer obtained is actually an average over a relatively large space. A similar geometry is also studied by Metzger et al. (1969,1972) and Hrycak (1978, 1981). Tabakoff and Clevenger (1972) study three different configurations of impinging jets on a concave surface: the single slot jet, the one-dimensional row of round jets, and the two-dimensional array of jets. Both the local and the average Nusselt number are determined. However, the local heat transfer Nusselt number obtained is again an average over a relatively large space. A few correlations of average Nusselt numbers for slot jet impingement cooling over a concave or a
TL;DR: In this paper, the authors investigated the effect of ambient air entrainment into a heated impinging jet on the heat transfer from a flat surface and provided a well-characterized jet by using a long circular pipe to obtain fully developed pipe flow for the jet and a uniform heat flux surface thermal boundary condition.
Abstract: This paper reports on a study to investigate the effect of ambient air entrainment into a heated impinging jet on the heat transfer from a flat surface. It provides a well-characterized jet by using a long circular pipe to obtain fully developed pipe flow for the jet and a uniform heat flux surface thermal boundary condition by electrically heating a vacuum-deposited gold coating. The surface temperature distribution is measured using a liquid crystal.
TL;DR: A review of the essential ingredients needed to make a mathematical model of fire spread through a fuel bed is given in this article, where a unified mathematical treatment is presented, which permits a more objective comparison of the different physical models.
Patent•
08 Jan 1991
TL;DR: In this paper, the authors present a modular system in which a heating or cooling liquid is circulated in a hermetically sealed flow path between a heating device and a heating pad.
Abstract: The invention provides systems for topically heating or cooling an animal or human body, and more particularly concerns a modular system in which a heating or cooling liquid is circulated in a hermetically sealed flow path between a heating or cooling device and a heating or cooling pad. In a preferred embodiment, the flow path includes a cassette which is reversibly engageable with a pump and a heating or cooling unit located in a housing.
TL;DR: In this paper, a simple model suitable for hand calculations is presented to predict temperature profiles in two-phase flowing wells, assuming that the heat transfer within the wellbore is steady-state.
Abstract: In this paper, a simple model suitable for hand calculations is presented to predict temperature profiles in two-phase flowing wells. The model, developed with measured temperature data from 392 wells, assumes that the heat transfer within the wellbore is steady-state. Comparisons between the model's predictions and field data indicate that the model is highly accurate within its range of application.
Book•
29 Jan 1991
TL;DR: In this paper, the authors present a solution for the problem of surface heating and cooling in a plane with a single phase change at the phase-change interface, and an approximate solution for two phases of phase change in a semi-infinite region.
Abstract: 1. BASIC EQUATIONS . The Nature of the Thermodynamic System. General Energy Equation for a Continuum. Energy Balance at the Phase-Change Interface. Nonlinearity of Solidification Problems. Conservation of Mass, Momentum and Energy for Continuum. Heat, Mass, and Momentum Flow in Porous Media. Nomenclature. References. 2. PLANE PROBLEMS WITH TEMPERATURE BOUNDARY CONDITIONS. Neumann Problem and Variations. Neumann Problem With Variable Properties. Neumann Problem With Variable Temperatures. Melting Temperature Range. Subcooled Liquid - Frazil Ice. Solidification in Contact with Cold Wall. Thaw With Consolidation of Melted Medium. Freeze of a Flowing Fluid. Freeze Coating on a Moving Sheet. Continuous Casting of Slab. Convective Effects. Nomenclature. References. 3. PLANE PROBLEMS WITH CONVECTION (RADIATION) AT FREE SURFACE. Single-Phase Problems. Two-Phase Problems. Nomenclature. References. 4. PLANE PROBLEMS WITH SPECIFIED SURFACE HEAT FLUX. Exact Solution for Semi-Infinite Medium. Approximate Solutions, Single Phase, Semi-Infinite Region. Two-Phase Problems. Ablation with Complete Removal of Melt. Freezing of a Flowing Fluid. Nomenclature. References. 5. THAW BENEATH INSULATED STRUCTURES QUASI-STEADY SOLUTIONS. General Quasi-Steady Relations. Nomenclature. References. 6. CYLINDRICAL PROBLEMS . Outward Phase Change, Infinite Domain. Outward Phase Change, Finite Geometry. Inward Phase Change. Convective Effects and Relations. Nomenclature. References. 7. PROBLEMS IN SPHERICAL GEOMETRY. Outward Phase Change. Spherical Problems, Inward Growth. Nomenclature. References. 8. PHASE CHANGE IN POROUS MEDIA. Natural Convection in Porous Media Without Phase Change. Natural Convection With Phase Change. Coupled Energy and Mass Fluxes. Nomenclature. References. APPENDIX A: Quasi-Static Approximations and Perturbation Methods. APPENDIX B: The Heat Balance Integral Method. APPENDIX C: Biot's Variational Principle. APPENDIX D: Error Function and Error Integral Family. APPENDIX E: Exponential Integral and Related Functions. APPENDIX F: Porous Media and Macroscopic Equations. APPENDIX G: Laplace Transforms and Phase-Change Problems. SUBJECT INDEX. AUTHOR INDEX.
TL;DR: In this paper, the effects of rotation on turbulent convection were investigated over a wide range of bottom buoyancy fluxes q0 and rotation rates Ω, including q = 0; q 0 and q 0 were held constant during each experiment.
Abstract: Laboratory experiments were carried out to investigate the effects of rotation on turbulent convection. The experimental facility was a bottom-heated, water-filled, cubical tank mounted on a turntable. The investigations were performed over a wide range of bottom buoyancy fluxes q0 and rotation rates Ω, including Ω = 0; q0 and Ω were held constant during each experiment. The depth of the water column H was fixed for the entire experimental programme. For the non-rotating experiments, the r.m.s. velocity fluctuations were found to scale well with the convective velocity , where the integral lengthscale is estimated as lr ≈ 0.25hc. The mean buoyancy gradient in the mixed layer was found to be much higher than in the corresponding non-rotating case, and the r.m.s. fluctuations and mean buoyancies were found to scale satisfactorily with (q0Ω)½. A spectral form for the temperature fluctuations in rotating convection is also proposed and is compared to the experimental results.
AeA1
TL;DR: Determination d'equations determinant l'interaction thermique des electrons and des phonons dans the phase de refroidissement des cascades de deplacement energetique pour Ni and Cu.
Abstract: A thermal description of the electron-ion interaction in the cooling phase of the displacement cascade in metals is given. Differential equations governing the transfer of heat between the two systems are derived and solved numerically using physically reasonable parameters for cascades in Cu and Ni. Large differences are found in the cooling rates of cascades in these two metals and the differences are shown to depend on the ratio of a parameter ${\mathit{T}}_{0}$, the temperature at which the electron-phonon mean free path reduces to the radius of the Wigner-Seitz sphere and ${\ensuremath{\gamma}}_{\mathit{e}}$, the coefficient of the electronic heat capacity. Simplified versions of the heat-transfer equations have been incorporated into a molecular-dynamics code in order to include the interaction in simulations of cascades in Cu. The net effect of including the interaction is to actually inhibit defect production in low-energy cascades (\ensuremath{\sim}500 eV) by damping the ionic motion.
12 Feb 1991
TL;DR: In this article, a complete two-dimensional flow/thermal model of the micro-channel cooler was developed, and the design parameters were optimized for the case of a 1 kW/cm/sup 2/ heat flux with the top surface at 25 degrees C.
Abstract: A complete two-dimensional flow/thermal model of the micro-channel cooler is developed. Optimization of the design parameters with this model is demonstrated for the case of a 1 kW/cm/sup 2/ heat flux with the top surface at 25 degrees C. For this case, pure water could be used as the coolant, or 92% water/8% methanol (-5 degrees C freezing point) if the heat is to be dumped to ice/water. The flow rate should be about 50 cc/s per cm/sup 2/ of surface area. The distribution manifold channel spacing (center-to-center) should be 333 mu m (30 channels/cm). The fin height should be about 167 mu m (H/sub F//L=1). The distribution manifold channel widths should be about 200 mu m (W/L=0.6). The micro-channels should be between 7 mu m and 14 mu m wide, while the ratio of fin thickness to micro-channel width should be from 0.5 to 1.0. With these design parameters, an effective heat transfer coefficient (surface heat flux divided by surface to coolant inlet temperature difference) on the order of 100 W/cm/sup 2/ K will be achieved with a total pressure drop of only about 2 bar. >
TL;DR: In this paper, the area-averaged properties of the planetary boundary layer over heterogeneous terrain are considered and a simple method for estimating these roughness lengths for use in boundary-layer parametrization is provided.
Abstract: The area-averaged properties of the planetary boundary layer over heterogeneous terrain are considered. Previous studies which dealt with the average momentum transfer properties in neutral static stability conditions are extended to include the influence of stratification and also area-averaged properties for heat transfer. Results from numerical simulations demonstrate the utility of values of effective roughness length for both momentum and heat transfer. A heuristic model is found to show good agreement with the numerical simulations and to provide a simple method for estimating these roughness lengths for use in boundary-layer parametrization.
Significant anomalies in the surface heat fluxes, particularly those of sensible heat, accompanied the decrease in the sea ice concentration. Substantial atmospheric warming was simulated over and in the vicinity of areas in which leads were considered. In all but one experiment there were anomalous easterlies between about 40 and 60°S with westerly anomalies further to the south. The surface pressure at high latitudes appears to change in a consistent fashion with the fraction of open water, with the largest changes occurring in the Weddell and near the Ross Seas.
Some of the feedbacks which may enhance the responses here, but which are not included in our model, are discussed.
TL;DR: In this paper, a color-capturing technique for the quantitative interpretation of liquid crystal images used in convective heat transfer studies is presented, which is highly applicable to the surfaces exposed to convective heating in gas turbine engines.
Abstract: A new image processing based color capturing technique for the quantitative interpretation of liquid crystal images used in convective heat transfer studies is presented. This method is highly applicable to the surfaces exposed to convective heating in gas turbine engines. It is shown that, in the single-crystal mode, many of the colors appearing on the heat transfer surface correlate strongly with the local temperature. A very accurate quantitative approach using an experimentally determined linear hue vs temperature relation is found to be possible. The new hue-capturing process is discussed in terms of the strength of the light source illuminating the heat transfer surface, the effect of the orientation of the illuminating source with respect to the surface, crystal layer uniformity, and the repeatability of the process. The present method is more advantageous than the multiple filter method because of its ability to generate many isotherms simultaneously from a single-crystal image at a high resolution in a very time-efficient manner.
Patent•
18 Mar 1991
TL;DR: In this paper, a microprocessor-based thermostat assembly is used to automatically determine and implement an optimum thermostats setback schedule (80) which, while maintaining a user-specified occupancy comfort schedule (39), minimizes the energy consumption of the climate control system.
Abstract: A computer (37) or microprocessor-based thermostat system (10) for automatically determining and implementing an optimum thermostat setback schedule (80) which, while maintaining a user-specified occupancy comfort schedule (39), minimizes the energy consumption of the climate control system (18) within an enclosure (30). The method of the thermostat assembly (10), using the continuous measurement of various air temperatures, fluid flows, and energy consumption rates includes the adaptive capability of indirectly learning the relevant thermal and thermodynamic characteristics of both the enclosure (30) and the climate control system (18), including such thermal parameters as the effective thermal capacitance of the internal walls and contents (53,55) of the enclosure (30), the effective internal heat transfer conductance between the thermal capacitance and the air within the conditioned space (28), the effective external heat transfer conductance between the inside air (28) and the outside air (36) and the efficiency of the climate control system (18), which includes the associated air distribution system (22, 32), as a function of its input energy rate. The method also includes a non-linear efficiency model, using the aforementioned thermal parameters, which has the capability of predicting, in advance of implementation, the energy consumption of the climate control system (18) as a function of outside air temperature and the user-specified occupancy comfort schedule (39). An optimization scheme is then used to determine the most energy efficient thermostat setback schedule (80) for the current outdoor air temperature, while still satisfying the user-specified occupancy comfort schedule (39).
TL;DR: In this paper, a flow boiling map is developed to depict the relationships among the heat transfer coefficient, quality, heat flux, and mass flux for different fluids in the subcooled and the saturated flow boiling regions.
Abstract: The thermal behavior of a flow boiling system is represented by a flow boiling map to illustrate visually the relationships among various system parameter. An earlier flow boiling map by Collier (1981) does not include the effect of mass flux and is specific to water at low pressures. For other fluids, significant departures from the parametric trends displayed in Collier's map have been reported in the literature (e.g, Kandlikar). In the present paper, a new flow boiling map is developed to depict the relationships among the heat transfer coefficient, quality, heat flux, and mass flux for different fluids in the subcooled and the saturated flow boiling regions. The trends observed in the experimental data and correlations for water and refrigerants are used in deriving the present map. The particular areas where further investigation is needed to validate the trends are also indicated. In the subcooled investigation is needed to validate the trends are also indicated. In the subcooled boiling region, h{sub TP}/h{sub lo} is plotted against x with Bo as a parameter, while in the saturated boiling region, h{sub TP}/h{sub lo} is plotted against x with {rho}{sub l}/{rho}{sub g} and a modified boiling number Bo* as parameters. It is hopedmore » that the map would prove to be helpful in explaining the role of different heat transfer mechanisms in flow boiling of different fluids.« less