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RESEARCH PAPERS

J. Heat Transfer. 1983;105(4):687-693. doi:10.1115/1.3245649.

Experimental blowdown results for initially isothermal, saturated water from a small pressure vessel containing internal geometry are presented. This experiment simulated a break in a large duct of approximately three diameters in length which exited from the vessel. Choking only occurred at the exit of the discharge duct, and the instantaneous internal vessel pressure distribution was nearly uniform. Most of the fluid within the vessel immediately after the initiation of the blowdown became superheated liquid. This thermodynamic state together with the activated wall cavities inside the vessel maintained a nearly constant internal vessel pressure history early in the blowdown. However, in the latter stage of the depressurization, the remaining fluid within the vessel was essentially in thermodynamic equilibrium. A nonuniform distribution of fluid quality within the vessel was also detected in this experiment. In addition, this experiment illustrates that transient, two-phase, critical flow in large diameter ducts is similar to steady, two-phase, critical flow in small diameter ducts.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):694-699. doi:10.1115/1.3245650.

Analytical models are presented to predict the internal vessel conditions during the decompression regimes of an initially saturated liquid. A subcooled blowdown analysis considers the elasticity of both the liquid and vessel. A bubble growth analysis for the intermediate period of blowdown is based on thermally dominated bubble growth from a solid surface into a superheated liquid. A dispersed analysis for the latter decompression period assumes the vapor bubbles have grown sufficiently so the liquid is uniformly distributed within the vapor phase. The sub-cooled analysis predicts the initial period of blowdown reasonably well. The bubble growth analysis predicts the rise in system pressure above that value to which it initially falls after the end of subcooled blowdown. It considers an initially “slow” depressurization rate (less than 400 MPa/s) where nucleation and bubble growth is the dominate volume producing, and thus pressure recovery, mechanism. It provides insight into why the system pressure initially drops below the saturation pressure, and it also offers an explanation for the subsequent recovery of the system pressure toward the saturation pressure. The thermodynamic equilibrium analysis provides a reasonable prediction of the latter stage of decompression. The combination of these three models predicts the overall two-phase decompression phenomenon reasonably well.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):700-705. doi:10.1115/1.3245651.

A steady-state analytical model has been developed to predict channel pressure drop as a function of inlet vapor flow rate and applied heat flux during conditions of countercurrent two-phase flow. The interfacial constitutive relations utilized are flow structure dependent and allow for the existence of either smooth or wavy liquid films. A computer code was developed to solve the analytical model. Predictions of Δp versus vapor flow rate were found to agree favorably with experimental data from adiabatic, air/water systems. In addition, the model was used to predict countercurrent flow conditions in heated channels characteristic of a BWR/4 nuclear reactor fuel assembly.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):706-712. doi:10.1115/1.3245652.

A study of steam condensation in countercurrent stratified flow of steam and subcooled water has been carried out in a rectangular channel inclined 33 deg to the horizontal. The variables in this experiment were the inlet water and steam flow rates, and the inlet water temperature. Condensation heat transfer coefficients were determined as functions of local steam and water flow rates, and the degree of subcooling. Correlations are given for the local Nusselt number for the smooth and for the rough interface regimes, and also for the dimensionless wave amplitude. A turbulence-centered model is also developed. It is shown that better agreement with the data can be obtained if the characteristic scales in the turbulent Nusselt number and Reynolds numbers are related to measured interfacial parameters rather than the bulk flow parameters. The important effect of interfacial shear, missing in previous eddy-transport models, is thus implicitly included.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):713-718. doi:10.1115/1.3245653.

Flooding of stratified countercurrent steam-water flow in nearly-horizontal and in inclined flat-plate geometries is investigated. An envelope theory for onset of flooding in inclined stratified flow is developed, which agrees better with the experimental data than other theories. In addition, some basic flow parameters, such as mean film thickness and interfacial friction factor in the roll-wave regime (near-flooding) have been measured. Empirical correlations for these parameters were sought, which are essential in the flooding analysis.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):719-727. doi:10.1115/1.3245654.

Reflux and natural circulation condensation in vertical inverted U-tube steam generators form an important heat removal mechanism for nuclear reactors in certain accidents. As a first step in understanding the behavior of such steam generators, condensation was studied in a single vertical tube with a cooling jacket. Steam was fed into the tube from an inlet plenum and condensed in the jacketed region. The inlet and outlet pressures and cooling jacket conditions were controlled to give well-defined boundary conditions. The amount of steam condensed and the flow patterns obtained were determined. The steam flow rate into the tube initially increased with pressure differences between the inlet and outlet plenums. The condensate ran back to the inlet plenum countercurrent to the steam flow (reflux flow). At a certain pressure difference, no further increase in steam inlet flow rate was observed though pure refluxing was maintained. Instead, a column of liquid formed above the two-phase condensing region. The length of this column increased as the pressure difference was increased. At a sufficiently large pressure difference the liquid column carried over the top of the vertical U-bend and there was a dramatic change in flow regime to natural circulation condensation in which the bulk of the condensate flowed cocurrently with the steam. The behavior of the system was explained by postulating that “flooding” conditions were reached at the inlet when the pressure difference became large enough for a liquid column to form above the condensing region. A small perturbation analysis of the stability of the condensing and liquid column regions was done using a lumped parameter approach and constant pressure boundary conditions. Experimental results on the frequency of oscillations in a single tube followed the qualitative trends predicted by the linear analysis, but the predicted frequencies were about twice as high as those observed.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):728-735. doi:10.1115/1.3245655.

The paper discusses the limitations of current practices of evaluating thermal performance of wet cooling towers and describes a more advanced mathematical model for mechanical and natural draft cooling towers. The mathematical model computes the two-dimensional distributions of: air velocity (two components); temperature, pressure, and moisture content; and water temperature. The downward direction of water flow is presumed. The local interphase heat and mass transfer rates are calculated from empirical correlations for which two options are provided. In the first option, only one constant (Ka, based on Merkel’s approximations) is employed; in the second option, two separate constants for heat and mass transfer are used. Boundary conditions can be either of the prescribed cooling range or of the prescribed hot water temperature types. The governing equations are solved by a finite difference method. The model is embodied into a computer code (VERA2D) which is applicable for the natural and mechanical draft towers of both the crossflow and counterflow arrangements. Several applications of the code are described in Part II of the paper.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):736-743. doi:10.1115/1.3245656.

This paper presents several applications of the mathematical model described in Part 1 of the paper. Natural and mechanical draft towers of counterflow and crossflow arrangement have been considered. Predicted thermal performances compare well with the available data from operating towers. The distributions of air velocities, pressure, temperature, moisture fraction, and water temperature have been assessed from the considerations of physical plausibility only, since no experimental data are available for comparison. Some sample parametric computations for a mechanical draft crossflow tower are also presented. The parameters studied are: (a) air travel dimension of fill; (b) aspect ratio of fill; (c) fan power; and (d) atmospheric pressure. The results are self-consistent and demonstrate the applicability of the model as an analysis tool.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):744-750. doi:10.1115/1.3245657.

Fluid-elastic instability is widely recognized as a mechanism which can cause rapid failure of tubes in shell and tube heat exchangers. The shellside flow velocity for the onset of the fluid-elastic whirling is commonly calculated from Connors’ formula provided that the instability factor is known. The literature contains several reported values of the instability factor for different tube bundles but these have been obtained from a variety of test configurations and this has led to some large discrepancies. This paper describes a systematic study of the effect of tube layout on the instability factor for sixteen tube bundles. The results presented show that the instability factor varies by a factor of 3 over the range of tube layouts tested. This paper concludes with a comparison of the results of the present study with values taken from the open literature.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):751-758. doi:10.1115/1.3245658.

This paper describes how a single porous baffle can be used to prevent the occurrence of acoustic vibration in a crossflow tubular heat exchanger. A method for determining the optimum location and the optimum specific flow resistance of the porous baffle is presented. Finally, a description of how a porous baffle was successfully applied to control acoustic vibration which was occurring in the heat recovery region of a 375-MW brown coal steam generator is given.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):759-766. doi:10.1115/1.3245659.

A numerical and experimental investigation on natural convective heat transfer with the coupling of heat conduction and thermal radiation from a vertical unheated plate connected to an upstream isothermal plate is carried out. The governing equations for conduction in the unheated plate and for convection in the boundary layer are written in finite difference form and are analyzed numerically by using an iterative technique coupled through the common heat flux with thermal radiation. The numerical results are discussed after comparing with the experimental results of temperature and velocity profiles and heat transfer coefficient. The coupling effects of heat conduction in the unheated plate and thermal radiation from the surface on laminar natural convective heat transfer from the plate connected to an isothermal heated upstream plate is greatly influenced by the plate-fluid thermal conductivity ratio and plate thickness, and the radiation emissivity of the plate.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):767-773. doi:10.1115/1.3245660.

Calculations of the stability of the buoyancy-induced flow of cold water, adjacent to a vertical surface, have been carried out. The disturbance equations, for an isothermal boundary condition, have been formulated with a new density relation for pure and saline water, of very high accuracy. Buoyancy terms in the base flow and disturbance equations, thereby, accurately express the buoyancy forces in water at low temperatures. Stability results are presented for a Prandtl number of 12.6 for a variety of ambient and surface temperature conditions. The anomalous cold water density behavior was found to produce important differences in stability from the Boussinesq solutions. The Boussinesq approximation consistently overpredicts the buoyancy force in upflow circumstances. The resulting neutral stability prediction lies upstream of the accurate ones. For temperature conditions which result in downflow, the predictions lie downstream of the accurate values. The effects may be very large.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):774-781. doi:10.1115/1.3245661.

An analysis is performed to study the heat/mass transfer and vortex instability characteristics of buoyancy induced flows that result from simultaneous diffusion of heat and mass in laminar boundary layers adjacent to horizontal and inclined surfaces. Numerical results are obtained for a Prandtl number of 0.7 over a range of Schmidt numbers and various angles of inclination from the horizontal, φ. For a given φ, it is found that when the two buoyancy forces from thermal and mass diffusion act in the same direction, both the surface heat and mass transfer rates increase, causing the flow to become more susceptible to the vortex mode of instability. These trends are reversed when the two buoyancy forces act in the opposite directions. On the other hand, as φ is increased, the heat and mass transfer rates are enhanced, but the instability of the flow to the vortex mode of disturbances decreases and eventually vanishes at φ = 90 deg.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):782-788. doi:10.1115/1.3245662.

The horizontal and vertical velocity profiles near a heated vertical wall of rectangular enclosure were measured for the laminar regime of natural convection with a laser-Doppler anemometer. The horizontal temperature profiles near the heated wall were measured with a thermocouple. An almost perfect two-dimensional mode of flow was confirmed for the central regime of the box. A minimum in the temperature profile between the hot wall and the thermally stratified central core resulted in a downward flow just outside the boundary layer of upward flow, but the central core was stagnant. Visualization of the flow with a phenolphtalein tracer confirmed the two-dimensionality of the flow along the vertical heated wall and revealed a zone of three-dimensional flow in the form of spiral streaklines along the insulated top plate toward the opposing cooled vertical wall. Measurements such as these provide for the first time the basis for a critical test of the accuracy of numerical solutions.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):789-794. doi:10.1115/1.3245663.

The one-equation model of turbulence is applied to the turbulent thermal convection between horizontal plates maintained at constant temperatures. A pseudo-three-layer model is used consisting of a conduction sublayer adjacent to the plates, a turbulent region within which the mixing length increases linearly, and a turbulent core within which the mixing length is a constant. It is assumed that the Nusselt number varies with the Rayleigh number to the one-third power. As a result, the steady-state distributions of the turbulent kinetic energy and the mean temperature are obtrained and presented in closed forms. These results include the effects of Prandtl number. The predictions are compared with the available experimental results for different Prandtl and Rayleigh numbers. Also included are the predictions of Kraichnan, which are based on a less exact analysis. The results of the one-equation model are in fair agreement with the experimental results for the distribution of the turbulent kinetic energy and the mean temperature distribution. The predictions of Kraichnan are in better agreement with the experimental results for the mean temperature distribution.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):795-802. doi:10.1115/1.3245664.

An experimental effort is presently underway to investigate natural convection in liquid-saturated porous media utilizing a geometry and hydrodynamic/thermal boundary conditions relevant to the problem of nuclear-waste isolation in geologic repositories. During the first phase of this research program, detailed measurements were made of the steady-state thermal field throughout an annular test region bounded by a vertical, constant-heat-flux, inner cylinder and a concentrically placed, constant-temperature, outer cylinder. An overlying, constant-pressure fluid layer was utilized to supply a permeable upper surface boundary condition. Results showed the heater surface temperature to increase with increasing vertical distance due to the buoyantly driven upflow. The measured temperature difference (ΔT) between the average heater surface temperature and the constant outer-surface temperature was found to be progressively below the straight-line/conduction-only solution for ΔT versus power input, as the latter was systematically increased. Comparisons between measured results and numerical predictions obtained using the finite element code MARIAH showed very good agreement, thereby contributing to the qualification of this code for repository-design applications.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):803-808. doi:10.1115/1.3245665.

This paper describes a theoretical and experimental study of two-dimensional, buoyancy-driven flow in a rectangular porous cavity with one permeable endwall. Connected to a constant temperature tank, the permeable end allows for natural recharge and discharge of the saturating fluid. The other vertical endwall is impermeable and maintained at a constant but higher temperature, thus inducing a buoyancy-driven flow. The theoretical study includes an asymptotic analysis developed for a shallow cavity with one permeable endwall and the numerical solutions of the power-law difference representation of the full governing equations. The experimental system consists of water-saturated glass beads packed in a rectangular cavity with a length-to-height aspect ratio of 3.17, for which the Rayleigh number can vary up to 120. Measurements were made of the steady-state temperature distribution in the cavity and the heat transfer rate from the impermeable endwall. It is shown that the constant pressure and temperature assumptions at the permeable wall, as employed in the theoretical analysis, satisfactorily predict the experimental data. Results are also compared with those existing in the literature.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):809-816. doi:10.1115/1.3245666.

A new experimental technique is introduced which facilitates visualization of the fluid flow phenomena occurring on a small surface immersed in an air fluidized bed. The flow visualization was correlated qualitatively with heat transfer data from the surface. Heat transfer coefficients versus air velocity curves were obtained and found to be strongly dependent on the angle of inclination of the surface relative to the air flow direction. Flow visualization has facilitated the identification of three mechanisms of heat transfer to a surface as a function of the angle of inclination and the air flow velocity. These include, conduction through a stationary layer of particles, convection through a flow of solid particles, and heat transfer by sequential contact with voids and a well mixed conglomerate of solid particles.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):817-822. doi:10.1115/1.3245667.

Flow visualization studies and heat transfer measurements have been made for water flow in an open channel which is uniformly heated from below. In addition, a two-dimensional boundary layer model, which includes a buoyancy term in the momentum equation and accounts for the effect of buoyancy on turbulence, has been used to predict the heat transfer measurements. Thermal boundary layer development involves an inlet region for which buoyancy effects are negligible, a transition region characterized by mixed convection, and a downstream region which is dominated by turbulent free convection. The regions are delineated in terms of the mixed convection parameter Grx /Rex 3/2 , and heat transfer measurements are compared with existing forced, free, and mixed convection correlations.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):823-829. doi:10.1115/1.3245668.

Results of a study of heat transfer in the vicinity of a backward-facing step of a uniform temperature are presented. Temperature distribution are measured using a Mach-Zehnder interferometer. The heat transfer upstream of the step is shown to be strongly enhanced by streamline curvature. Downstream of the step the heat transfer increases monotonically in the streamwise direction but is always less than the flat-plate value. For the largest step investigated, the average heat transfer in the reverse flow region is reduced to 56 percent of the flat-plate results, in agreement with an existing theory for laminar separated flow originally developed for a cavity. The heat transfer is systematically smaller for smaller steps. For all steps, the average heat transfer is described by the equation, St = 0.787(Res )−0.55 (s/xs )0.72 .

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):830-834. doi:10.1115/1.3245669.

The effects of the stretching of filaments on the cooling of fibers during the melt-spinning process are studied numerically. The filament is modeled as a continuous, cylindrical cone that moves steadily through an otherwise quiescent environment, with its diameter attenuating exponentially. Radiative cooling from the fiber surface is also accounted for in the analysis. The buoyancy-affected laminar and turbulent boundary layer equations are solved by a finite difference scheme, to determine the axial temperature variation of the filament. It is found that the reduction of the fiber diameter and the subsequent increase in the local speed of the filament enhances greatly the cooling from the filament surface, whereas the increase of the cooling due to radiative losses is not significant for all the flow cases considered.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):835-840. doi:10.1115/1.3245670.

Measured heat transfer rates through turbulent and transitional boundary layers on an isothermal, convexly curved wall show Stanton numbers 20–50 percent below flat wall values. Recovery is slow on a flat wall downstream of the curve; after 60 cm, Stanton numbers were 15–20 percent below flat wall values. Five secondary effects were studied: (i) initial boundary layer thickness, (ii) free-stream velocity, (iii) free-stream acceleration, (iv) unheated starting length, and (v) transition. Regardless of the initial state, curvature without acceleration eventually forced the boundary layer into an asymptotic condition: StαRe Δ2 −1 . Strong acceleration with curvature brought the exponent on ReΔ2 to −2.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):841-845. doi:10.1115/1.3245671.

Extensive measurements were made of the response of a turbulent boundary layer to a double step change of wall heat flux. The measurements include mean temperature and velocity as well as temperature-velocity correlations up to third order occurring in the ϑ2 and vϑ transport equations together with the skewness and flatness of temperature fluctuations. Two thermal layers start to develop within the primary boundary layer due to the change in heat flux at boundary. These layers are characterized with different growth rates which depend on the wall heat flux. Most of the changes in the downstream stations take place inside the second thermal layer.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):846-850. doi:10.1115/1.3245672.

The influence of forced flow on the He I-He II, two-phase flow has been studied during heat transfer to superfluid He II in a U-shaped tube, at pressures from 2.4 bar to 10 bar, bath temperatures from 1.6 K to 2.1 K, and flow velocities from zero internally applied speed (“zero net mass flow”) to the order of 0.1 cm/s. Within this range of conditions, forced flow (i) did not influence heat transfer prior to phase transitions more than 10 percent; (ii) reduced temperature excursions at lambda phase transitions by a factor of 2 at most with respect to zero net mass flow; (iii) did not influence the limiting heat flux density at initiation of the lambda transition in the supercritical pressure range covered.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):851-861. doi:10.1115/1.3245673.

Experiments were performed in a flat rectangular duct to determine the heat transfer and pressure drop response to periodic, rod-type disturbance elements situated adjacent to one principal wall and oriented transverse to the flow direction. In a portion of the experiments, heat transfer occurred only at the rodded wall, while in the remainder, heat was transferred at both principal walls of the duct. Highly detailed axial distributions of the local heat transfer coefficient were obtained. These distributions revealed the rapid establishment of a periodic (i.e., cyclic) fully developed regime as well as recurring local maxima and minima. Cycle-average, fully developed heat transfer coefficients were evaluated and were found to be much larger than those for a smooth-walled duct. Linear pressure distributions were measured between periodically positioned stations in the fully developed region, and the corresponding friction factors were several times greater than the smooth-duct values. The heat transfer and friction data were very well correlated using parameters that take account of the effective surface roughness associated with the disturbance rods.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):862-869. doi:10.1115/1.3245674.

An experimental and numerical study is reported on heat transfer in the separated flow region created by an abrupt circular pipe expansion. Heat transfer coefficients were measured along the pipe wall downstream from an expansion for three different expansion ratios of d/D = 0.195, 0.391, and 0.586 for Reynolds numbers ranging from 104 to 1.5 × 105 . The results are compared with the numerical solutions obtained with the k ∼ ε turbulence model. In this computation a new finite difference scheme is developed which shows several advantages over the ordinary hybrid scheme. The study also covers the derivation of a new wall function model. Generally good agreement between the measured and the computed results is shown.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):870-877. doi:10.1115/1.3245675.

Measurements were made of the axial and circumferential distributions of the heat transfer coefficient in a tube in which the entering airflow is highly skewed. The skewness was caused by competition between the test section tube and a parallel tube which draws air from the same plenum chamber. For each of several fixed Reynolds numbers in the test section tube, the flow imbalance between the competing tubes was varied parametrically (up to a factor of eighteen), as was the center-to-center separation distance between the tubes (separation = 1.5, 3, and 4.5 times the tube diameter). Measurements were also made of the pressure drop, and a visualization technique was employed to examine the pattern of fluid flow. Practically significant effects of the flow imbalance on the axial distribution of the heat transfer coefficient were encountered only at the smallest of the investigated intertube spacings. Even for that case, the effects were moderate; for example, the imbalance-related changes for an imbalance ratio of two did not exceed 7 percent. The experiments involved naphthalene sublimation, and a new technique was developed for coating the inside surface of a tube with naphthalene.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):878-883. doi:10.1115/1.3245676.

An analytical method for the numerical calculation of the heat transfer coefficient in arbitrarily shaped ducts with constant wall temperature at the boundary is presented. The flow is considered to be laminar and fully developed, both thermally and hydrodynamically. The method presented herein makes use of Galerkin-type functions for computation of the Nusselt number. This method is applied to circular pipes and ducts with rectangular, isosceles triangular, and right triangular cross sections. A three-term or even a two-term solution yields accurate solutions for circular ducts. The situation is similar for right triangular ducts with two equal sides. However, for narrower ducts, a larger number of terms must be used.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):884-888. doi:10.1115/1.3245677.

The events associated with the discharge of a 20-mm caliber weapon have been examined in detail in order to identify and understand important features of the reacting gun muzzle flow field. The diagnostics applied involves shadowgraph and Schlieren photography, invasive pressure probes, spectroscopy for temperature measurements and Laser-Doppler velocimetry for velocity measurements. Emphasis has been on velocity measurements using two setups to determine both the axial and lateral velocity components throughout the muzzle flow field. The data clearly demonstrate the complexity of the processes involved in the unsteady flow expansion of the gun muzzle exhaust flow.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):889-894. doi:10.1115/1.3245678.

This paper describes experimental studies of heat transfer due to the oscillations of gas columns that are spontaneously induced in a tube with steep temperature gradients. The tube (∼3 m in length) is closed at both ends and bent into U-shaped form at the midpoint. The temperature distribution along the tube is step-functional and symmetrical with respect to the midpoint. The warm part (closed-end sides) is maintained at room temperature and the cold one is immersed in liquid helium (4.2 K). The heat transported from the warm part to the cold is estimated from the evaporation rate of liquid helium. The heat flux by the oscillations is proportional to the square of the pressure amplitude, and the effective heat conductivity can be several orders of magnitude larger than the molecular heat conductivity of gas. The experimental results are compared with the theory of the second-order heat flux proposed by Rott and are found to be in satisfactory agreement with this.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):895-901. doi:10.1115/1.3245679.

An experimental study was carried out on the properties and growth rate of the frost layer which developed on a cooled vertical plate in free convective flow. Dimensionless parameters introduced by dimensional analysis were found to be effective in predicting frost densities, its thermal conductivities and growth rates. It was also found that the frost formation process can be divided into two periods if the frost growth data are correlated with the dimensionless parameters presented.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):902-907. doi:10.1115/1.3245680.

The wave nature of heat propagation in a semi-infinite medium containing volumetric energy sources is investigated by solving the hyperbolic heat conduction equation. Analytic expressions are developed for the temperature and heat flux distributions. The solutions reveal that the spontaneous release of a finite pulse of energy gives rise to a thermal wave front which travels through the medium at a finite velocity, decaying exponentially while dissipating its energy along its path. When a concentrated pulse of energy is released, the temperature and heat flux in the wave front become severe. For situations involving very short times or very low temperatures, the classical heat diffusion theory significantly underestimates the magnitude of the temperature and heat flux in this thermal front, since the classical theory leads to instantaneous heat diffusion at an infinite propagation velocity.

Commentary by Dr. Valentin Fuster

TECHNICAL BRIEFS

J. Heat Transfer. 1983;105(4):908-910. doi:10.1115/1.3245681.
Abstract
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):916-919. doi:10.1115/1.3245684.
Abstract
Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):919-922. doi:10.1115/1.3245685.

An analysis of the laminar steady-state forced convection heat transfer from a nonisothermal thin needle in an accelerating incompressible non-Newtonian fluid is presented. Similarity temperature profile and heat transfer characteristics are obtained for needles with axial power-law variations in surface temperature and surface heat flux. Effects of the needle size, the non-Newtonian flow behavior, and the generalized Prandtl number of the thermal characteristics of the flow are examined in detail.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):922-924. doi:10.1115/1.3245686.
Abstract
Topics: Convection , Ducts
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):928-931. doi:10.1115/1.3245688.
Abstract
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster

DISCUSSIONS

J. Heat Transfer. 1983;105(4):939. doi:10.1115/1.3245692.
FREE TO VIEW
Abstract
Topics: Heat transfer
Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1983;105(4):939. doi:10.1115/1.3245693.
FREE TO VIEW
Abstract
Topics: Heat transfer

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