摘要:

AbstractExperimental data are reported for condensing Freon‐114 (tetrafluorodichloroethane) and steam at several pressures. The condition of the vapors ranged from saturation to 180°F. of superheat. The condensing tube containing embedded thermocouples was 3/4 in. in diameter and 3 ft. long. Visual observation showed that steam condensed by dropwise condensation in part. Increase of superheat in the vapor at constant pressure caused a lowering of the tube‐wall temperature, which was indicative of a lowering of the surface temperature of the condensate. The lowering of the condensate‐surface temperature below the saturation temperature was computed from the experimental tube‐wall temperatures, the heat flux, and Nusselt's equation for the condensate‐film resistance. The lowering of the condensate‐surface temperature is correlated with degree of superheat. An interfacial coefficient of heat transfer between the superheated vapor and the condensate surface is reported based on the computed surface temperatures. Schrage's analysis and equations for relating mass and heat transfer with conditions at an interface were simplified and used to correlated the experimental condensing load with the degree

ISSN:0001-1541    

DOI:10.1002/aic.690040109

出版商:American Institute of Chemical Engineers    

年代:1958

数据来源: WILEY

摘要:

AbstractA new, simple electric analogue model is demonstrated which gives solutions, accurate within ten %, to problems in nonsteady state flow of heat, diffusion, and flow of liquids in porous media. The analogue consists essentially of a sandwich of electrical conducting paper, polyethylene or polyester sheeting, and metal foil. One‐ or two‐dimensional problems can be treated. This analogue provides a medium with distributed resistance and capacitance rather than the finite steps of conventional analogues; therefore two‐dimensional problems of complex shape can easily be modeled. The analogue is pulsed by a square wave generator and the transient potential response is displayed on a cathode‐ray oscil

ISSN:0001-1541    

DOI:10.1002/aic.690040110

出版商:American Institute of Chemical Engineers    

年代:1958

数据来源: WILEY

摘要:

AbstractProblems in heat conduction involving a moving boundary are encountered in the freezing of liquids and in other situations. Such problems are difficult to solve, and exact solutions are almost unknown. A graphical method for obtaining numerical solutions to problems of this type which can be described in terms of one space coordinate is derived and is demonstrated in two examples involving the freezing of liquids. The method, which does not require specialized knowledge or equipment, takes into account both sensible heats and latent heat.

ISSN:0001-1541    

DOI:10.1002/aic.690040111

出版商:American Institute of Chemical Engineers    

年代:1958

数据来源: WILEY

摘要:

AbstractHeat transfer measurements were made with vertical stainless steel bayonet tubes, 3/8 to 3/4 in. O.D., with lengths from 2.6 to 6.5 in. The heat source was steam. The boiling film ΔTranged from 154° to 314°F. for three organic liquids and from 547° to 788°F. for nitrogen, all at 1 atm. No forced convection was used. Benzene, carbon tetrachloride, and nitrogen on the longer tubes hadhvalues two or three times greater than predicted by the Bromley equation; however, the Reynolds numbers were found to exceed 2,000. Nitrogen on the 2.6‐in. length obeyed the equation; the Reynolds numbers were less than 2,000, the flow was proved by photography to be turbulent and thehvalues were much higher than predicted for viscous flow. A correlation is given which fits all the data except for methanol. It shows that a vertical orientation is superior to the horizontal for liquids boiling outside

ISSN:0001-1541    

DOI:10.1002/aic.690040112

出版商:American Institute of Chemical Engineers    

年代:1958

数据来源: WILEY

摘要:

AbstractHeat and momentum transfer studies have been made for the flow of gases through fixed beds consisting of randomly packed, solid metallic particles. The experimental technique employed in these studies made possible for the first time the procurement of gas‐film heat transfer data under steady state conditions and in the absence of mass transfer effects. Electric current passed through the metallic particles of the bed created within the particles a steady generation of heat, which was continuously removed by gases flowing through the bed. Several direct temperature measurements of both gases and solids within the bed made possible the direct calculation of the heat transfer coefficient for the gas film to produce the Colburn heat transfer factorjh, which has been found to correlate with the modified Reynolds number,Reh= √ApG/[µ(1 – ∈)φ]. The shape factor φ was established in these studies for cubes and cylinders and was found to be identical to their respective sphericities.Pressure‐drop measurements produced a friction factorfkof the Blake type, which yielded separate curves for each shape when correlated with the modified Reynolds numberRem. No simple relationship was found to exist between the heat transfer and friction factors. A single correlation of the pressure‐drop data was obtained for the modulusfkoφnwhen correlated with a Reynolds number of the typeRem= √ApG/[µ(1 – ∈)]. The exponentnvaries with the particle shape.Experimental runs have been carried out for 3/16, 1/4, 5/16‐in. spheres, 1/4 and 3/8‐in. cubes, and regular cylinders using hydrogen and carbon dioxide to extend the range of molecular weights beyond that of air, used for the majority of these runs. A particle‐size, column‐diameter effect was found to exist for both heat and momentum transfer. This effect becomes signific

ISSN:0001-1541    

DOI:10.1002/aic.690040113

出版商:American Institute of Chemical Engineers    

年代:1958

数据来源: WILEY

摘要:

AbstractSteady state heat transfer experiments were carried out in a 4‐in. I.D. transite tube packed with 3/8‐, 1/4‐, and 5/32‐in. steel spheres. Heat was generated in the pellets by means of a high‐frequency induction coil surrounding the test section. Average heat transfer coefficients between the bed of spheres and a stream of air passing through the bed were calculated for Reynolds numbers of from 200 to 10,400. To ensure the reproducibility of the data, the bed was repacked six times for each pellet size.A study of the effect of the tube‐to‐pellet‐diameter ratio indicates that this effect is large for low values of the ratio, but much smaller for higher ratios. The results are presented both graphically and in terms of empirical equations. The analogies among heat, mass, and momentum transfer are discussed, and it was found that no simple relation between the heat transfer coefficient and the friction factor exists for packed beds with a gas as the fluid.An attempt is made to predict the heat transfer rates for packed beds from heat transfer data for single spheres and from pressure‐drop measurements for the packed bed; however, the rates predicted from the pressure‐drop measurements are somewhat lower than the e

ISSN:0001-1541    

DOI:10.1002/aic.690040114

出版商:American Institute of Chemical Engineers    

年代:1958

数据来源: WILEY

摘要:

AbstractLocal boiling heat transfer coefficients were experimentally determined for nucleate boiling around the outer circumference of horizontal copper tubing. The tubes used were of 16 B.W.G. hard‐temper copper with outside diameters of 1 1/4 and 2 in; the liquids boiled were methanol andn‐hexane. The maximum peripheral variation occurred with the 1 1/4‐in. tube in methanol where an over‐all ΔTof 30.2°F. gave local outside coefficients varying between 249 and 548 B.t.u./(hr.)(sq. ft.)(°F.). The minimum variation was found to occur in the same system, in which an over‐all ΔTof 72.3°F. gave coefficients varying between 856 and 910 B.t.u./(hr.)(sq. ft.)(F.°). The results, plotted in polar coordinates, showed a cardioid configuration for methanol with the maximum coefficients occurring at the bottom of the tube. Then‐hexane results had the general shape of horizontal ellipses with maximum coefficients occurring at the

ISSN:0001-1541    

DOI:10.1002/aic.690040115

出版商:American Institute of Chemical Engineers    

年代:1958

数据来源: WILEY

摘要:

AbstractOne of the important factors affecting the rate of heat transfer by natural convection is the temperature‐density relationship of the convecting fluid. The importance of this factor is amplified when the heat is being transferred to a medium which has a maximum density.This investigation consisted of measuring the heat transfer rates, velocity gradients, and temperature profiles when heat is transferred from a flat vertical plate to water in the region of 4°C. In some experiments the flow in the boundary layer was observed to be downward while at other conditions of plate and fluid temperature a dual motion (both up and down) was noted, thus establishing a basic difference in the heat transfer mechanism and precluding a unified theory. Theoretical consideration is given to each mechanism and a criterion is derived to predict the flow regime which will prevail at fixed conditions of plate and bulk temperatures.An analogue computer was used to establish theoretical velocity and temperature profiles. The theoretical values agree reasonably well with the measured values; however, the experimental temperrature gradients near the wall were not sufficiently accurate to be extrapolated to determine a point heat transfer coeffice

ISSN:0001-1541    

DOI:10.1002/aic.690040116

出版商:American Institute of Chemical Engineers    

年代:1958

数据来源: WILEY

摘要:

AbstractRates of flow of pure gases, both those with no adsorption and those with appreciable adsorption, were studied as a function of pressure level, pressure drop, and temperature for flow through 1/2‐in.‐diameter cylindrical plugs of activated carbon and of unsintered Vycor glass. Adsorption isotherms for the pure gases on Vycor glass were measured over the range of variables covered in the flow studies. A few measurements were made for bulk liquid flowing through a Vycor plug.Permeabilities, which are proportional to the rate of flow per unit of pressure drop, were satisfactorily correlated for hydrogen, helium, argon, and nitrogen by employing existing gas‐phase flow theory. Permeabilities considerably larger than the values predicted from the nonadsorbed gas correlation, sometimes more than seventeen times as large, were observed for ethylene, propylene, and isobutane flowing through a Vycor plug. For the hydrocarbon‐Vycor systems, permeabilities for vapor flow are as much as sixty times larger than for bulk liquid flow.The unusual flow phenomena for the hydrocarbon‐Vycor systems are attributed to a rapid transport in the adsorbed layer. The total transport is treated as being the sum of gas‐phase and adsorbed‐layer flow. An equation describing adsorbed‐layer movement is derived by utilizing a force balance together with thermodynamic principles. The resulting equation has just one empirical constant, and its use requires adsorption‐isotherm data. It correlates very well the surface flow rates for the major range of the variables covered in this investigation. Rate measurements were made for adsorbed‐layer concentrations ranging from about one tenth of a monolayer up through the capillary condensation region. Deviations in the one constant form of the equation are observed below one tenth of a monolayer. The available literature data on flow in adsorbed layers are reasonably well correlated b

ISSN:0001-1541    

DOI:10.1002/aic.690040117

出版商:American Institute of Chemical Engineers    

年代:1958

数据来源: WILEY

ISSN:0001-1541    

DOI:10.1002/aic.690040118

出版商:American Institute of Chemical Engineers    

年代:1958

数据来源: WILEY