This paper describes the development of a new method for measuring water vapor transport through common building materials. The method represents an improvement in flexibility over the standard ASTM cup methods in terms of allowing isothermal and nonisothermal testing. The method also accounts for convective boundary layers on both sides of the test material. This paper contains preliminary test results using gypsum board materials. Future testing will attempt to gain transport data for these and other materials under likely operating environments.

Numerical simulations of a geothermal reservoir often assume that the primary heat source is a magmatic system; however, heat from the host rock and the coupled complex transport phenomena between magma chamber and host rock also need to be considered. This research numerically simulated the cooling history of an enclosed magma chamber and the thermal effects on the host rock around it from which geothermal energy could be extracted. Modeling of the magma body included natural convection, the effect of latent heat of phase change when the crystals are being formed between the liquidus temperature and the solidus temperature, and heat conduction when the temperature is below the solidus temperature. This study takes as an example a geothermal reservoir in southern Peru (Western Cordillera) whose heat source is a rhyolitic magma chamber like those that gave rise to the intrusive rocks of the Peru coastal cordillera. This analysis varies the chamber shape and uses three solidification temperature ranges for convection and conduction models above the rock formation temperature (solidus) to study the implications for heating of the host rock. This is the first study of its kind in this area. The center of an average-sized magma chambers takes approximately 500 ka to cool from 800 °C to 300 °C. Simulated cooling times between intrusion and solidus temperatures decreased 3 ka when convection was modeled along with conduction cooling. Cooling times decreased by up to 6 ka when the solidification temperature range was increased. The host rock temperature pattern depends strongly on the stage at which the magma chamber is modeled to begin cooling. The temperatures results near the surface of the host rock obtained in this work match well with measurements at hot springs founded in several places in the Western Cordillera. Application of the methodology proposed in this study can reduce uncertainties in planning geothermal energy extraction wells. The accuracy of the numerical model described here could be improved by including more ground data from exploration wells, e.g., soil stratigraphy and temperatures variation with depth.

A two-dimensional finite difference numerical model has been developed to study coupled soil heat and moisture flow around an earth-sheltered construction. Simulations of a basement wall backfilled with a sand and a clay loam were performed. For the sandy soil, a 9% greater wall heat loss during the winter and an increase of over 40% in summer heat gain were observed when the coupling was modelled. The principle mechanism for the greater heat flow was the energy transported by the moisture flow from the ground surface. For the clayey soil, there was no difference between the coupled and uncoupled results.

A mathematical model is presented for evaporating waste from the Melton Valley Storage Tanks (MVSTs) at Oak Ridge National Laboratory. This paper shows that the evaporation of liquid waste from the MVSTs is a viable option for increasing the available waste storage volume over a significant time period. The evaporation process has been modeled using mass and heat transfer through the formation of a bubble chain. This bubble chain is formed by sparging air through five 1-in. diam pipes. The sparged air is then dispersed inside a tank with a 50000 gal waste capacity. This paper discusses in detail the bubble formation, velocity of rise and the correlation obtained, and how it is used for heat- and mass-transfer analysis. The mathematical model is then used to compute the vapor concentration in milligrams per liter inside the tanks and in the associated piping system. These findings, along with the experimental measurements from the pilot plant, are illustrated in tabular and graphical form. The accuracy of the mathematical model was verified using data from a laboratory-scale experimental system. Comparison of these results indicates an excellent agreement for liquid water and synthetic waste. In addition, the evaporation rate and the number of tanks required are plotted against the sparging air temperature for dehumidified air, as well as for different mass flow rates and the significance of these curves is also discussed.

Synthese bibliographique et bibliographie des publications mondiales sur le transfert de chaleur en 1984

Ratios of the thermal diffusion coefficient to the moisture diffusion coefficient were experimentally determined for two types of soils. The ratio of the diffusion coefficients was found to increase with increasing moisture content, reach a broad maximum, and thereafter decrease. Except for the drier regions near the warm end, the ratio was found to be in the range 10−3-10−20C−1. Analytical predictions for the thermal diffusion coefficients were combined with the experimental results to determine the moisture diffusion coefficients. The thermal diffusion coefficient was predicted to decrease with both decreasing temperature and increasing moisture content. For the soils used in this study, the moisture diffusion coefficient was estimated to be in the range 10−5-10−4 g s−1 cm−1.

Synthese des travaux publies et bibliographie mondiale sur le transfert de chaleur pour l'annee 1983

Convective heat transfer properties of an hydrodynamically and thermally fully-developed flow in a multi-passage circular tube subjected to an external uniform heat flux are analyzed. The significant dimensionless parameters affecting the problem have been determined. The expressions of Nusselt numbers on the inner and the outer wall are obtained. The limiting cases are correlated with the existing values. The representative curves illustrating the variation of Nusselt numbers with the pertinent parameters are plotted.On analyse la convection thermique d'un écoulement hydrodynamiquement et thermiquement établi dans un tube circulaire multi-passage, soumis à un flux de chaleur externe uniforme. Les paramètres sans dimension qui caractérisent le problème sont déterminés. On obtient les expressions des nombres de Nusselt sur les parois interne et externe. Les cas limites sont reliés aux valeurs existantes. On donne les courbes représentant la variation des nombres de Nusselt avec les paramètres pertinents.Der konvektive Wärmeübergang bei einer hydrodynamisch und thermisch voll entwickelten Strömung in einem mehrgängigen kreisrunden Rohr wurde bei aufgeprägter äuβerer Wärmestromdichte untersucht. Die signifikanten dimensionslosen Parameter wurden bestimmt. Es werden Ausdrücke für die Nusseltzahl des inneren und äuβeren Wärmeüberganges ermittelt. Die Grenzfälle werden mit vorhandenen Werten korreliert. Die dargestellten Kurvenverläufe zeigen die Abhängigkeit der Nusseltzahl von den entsprechenden Parametern.Aнaлизиpyютcя чapaктepиcтики кoнвeктивнoгo тeплooбмeнa гидpoдинaмичecки и тepмичecки пoлнocтью paзвитoгo тeчeния в мнoгoкaнaльнoй кoльцeвoй тpyбe пpи paвнoмepнoм нaгpeвe внeшним тeплoвым пoтoкoм. Oпpeдeлeны вaжныe бeзpaзмepныe пapaмeтpы. Пoлyчeны выpaжeния для чиceл Hycceльтa нa внyтpeннeй и внeшнeй cтeнкaч. Paccмoтpeнo cooтнoшeниe мeждy дaнными в пpeдeльныч cлyчaяч и имeющимиcя вeличинaми. Пocтpoeны гpaфичecкиe зaвиcимocти измeнeния чиceл Hycceльтa oт cooтвeтcтвyющич пapaмeтpoв.

A band model for atmospheric absorption is used to calculate the incoming longwave atmospheric radiative flux for some typical clear sky conditions. The sky radiation is also measured using a specially-designed calorimetric apparatus over a wide range of ground-level atmospheric conditions. Good agreement is obtained between the measurement and the calculation using appropriate atmospheric conditions. Two simple equations are proposed for the prediction of seasonal values of sky radiation: one for summer-type conditions without a quasi-permanent temperature inversion, and one for winter-type conditions with a quasi-permanent temperature inversion. Spectral information of the atmospheric radiation is presented, and the spectral flux in the wavelength range 8–14 μm is computed for typical conditions.

Experiments were performed to study freezing on a finned vertical tube when either conduction in the solid or natural convection in the liquid controls the heat transfer. Conduction is the controlling mode when the liquid is at its fusion temperature, whereas natural convection controls when the liquid temperature is above the fusion value. The phase change medium was a paraffin, 99% pure n-eicosane, with a fusion temperature of 36.4°C. Auxiliary experiments were also performed with an unfinned tube to obtain comparison data. For conduction control, the enhancement of freezing due to finning is less than the area ratio of the finned and unfinned tubes, whereas for natural-convection control the enhancement is very nearly equal to the area ratio. The liquid-solid interface is a thicket of whisker-like crystals when conduction controls but is straight (i.e. vertical). On the other hand, the interface is smooth but tapered when natural convection controls—yielding bottom-heavy frozen specimens. When conduction controls, freezing continues more or less indefinitely, whereas natural convection severely retards the freezing and ultimately terminates it altogether.

Inserting roughness geometry on the heat transfer surface of the collector plate is one of the sound ways to improve the heat transport rate through a solar air heater duct (SAHD). The present study elucidates a collective review of the type of roughness geometry used, the range of parameters investigated, and optimum parameters for the maximum thermal performance. This review article compares thermo-hydraulic performance and enhancement in heat transfer of various experimental and numerical works. The provision of artificial roughness on the collector surface has been effective due to breaking the boundary layer, strong-turbulence generation, and secondary flow formation. Roughness elements like multi v-fashion ribs with gaps, multi arc-fashion ribs with gaps, discrete multiple arc-fashion ribs, and conical ring turbulator with jet-impingement are found to have maximum heat transfer ratio compared to the base model in the respective parametric range. A mathematical model with 90% porous serpentine-wavy wire mesh on a collector plate was found to have thermal efficiency and an effective efficiency of 80% and 74%, respectively. The three-sided ribbed SAHD is far superior (40–48% increase in efficiency) to that of single-sided SAHD. Maximum effective efficiency of 80.12% was observed for a parallel-pass double duct with inclined ribs.

A systematic experimental study was carried out to determine how the heat transfer characteristics of a turbulent tube flow are affected by the length and diameter of a cylindrical plenum chamber which delivers fluid to the tube. The net pressure loss due to the presence of the plenum was also measured. The experimental arrangement was such that the fluid experiences a consecutive expansion and contraction in the plenum before entering the electrically heated test section. Air was the working fluid, and the Reynolds number was varied over the range from 5,000 to 60,000. It was found that at axial stations in the upstream portion of the tube, there are substantially higher heat transfer coefficients in the presence of longer plenums. Thus, a longer plenum functions as an enhancement device. On the other hand, the plenum diameter appears to have only a minor influence in the range investigated (i.e., plenum diameters equal to three and six times the tube diameter). The fully developed Nusselt numbers are independent of the plenum length and diameter. With longer plenums in place, the thermal entrance length showed increased sensitivity to Reynolds number in the fully turbulent regime. The pressure loss coefficient, which compares the plenum-related pressure loss with the velocity head in the tube, increases more or less linearly with the plenum length. With regard to experimental technique, it was demonstrated that guard heating/cooling of the electrical bus adjacent to the tube inlet is necessary for accurate heat transfer results at low Reynolds numbers but, although desirable, is less necessary at higher Reynolds numbers.

Experiments were performed to study the transition between freezing controlled by natural convection in the liquid adjacent to a freezing interface and freezing controlled by heat conduction in the solidified material. The freezing took place on a cooled vertical tube immersed in an initially superheated liquid contained in an adiabatic-walled vessel. At early and intermediate times, temperature differences throughout the liquid induce a vigorous natural convection motion which retards freezing, but the temperature differences diminish with time and natural convection ebbs. At large times, the freezing rate is fully controlled by heat conduction in the solidified material. The frozen specimens for short and intermediate freezing times are smooth-surfaced and tapered, while those for large times are straight-sided and have surfaces that are overlaid with a thicket of large discrete crystals. These characteristics correspond respectively to those of natural-convection-controlled freezing and conduction-controlled freezing. At early times, the measured mass of the frozen material is identical to that for natural-convection-controlled freezing. At later times, the frozen mass tends to approach that for conduction-controlled freezing, but a residual deficit remains.

Heat transfer and pressure drop experiments were performed for in-line pin fin arrays to obtain basic data to complement available information for staggered arrays. The experimental data were utilized as input to analyses aimed at establishing performance relationships between in-line and staggered arrays. In the experiments, mass transfer measurements via the naphthalene sublimation technique were employed to determine the row-by-row distribution of the heat (mass) transfer coefficient. Fully developed conditions prevailed for the fourth row and beyond. In general, the fully developed heat transfer coefficients for the in-line array are lower than those for the staggered array, but the pressure drop is also lower. The deviations between the two arrays increase with increasing fin height. With regard to performance, the in-line array transfers more heat than the staggered array under conditions of equal pumping power and equal heat transfer area. On the other hand, at a fixed heat load and fixed mass flow rate, the staggered array requires less heat transfer surface than the in-line array.

The performance of several solar collector configurations has been predicted using both inappropriate and appropriate relations to evaluate the wind-related heat transfer coefficient. The combinations analyzed are: one or two covers and a selectively absorbing surface coating, and one or two covers and a nonselectively absorbing surface coating all collectors are of the basic liquid heating type. It is shown that the optimum results are obtained by using a global correlation equation proposed by Sparrow et al. (1979).