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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

End effects in packed beds

Clark, Craig January 1960 (has links)
Results are reported of steady-state heat transfer studies on various beds of 0.7-inch diameter porous spheres packed in simple cubic configuration, in which the simultaneous transfer of mass and heat occurs between the surface of these spheres and an air stream. The thermal wall effect, which is caused by the participation of the packing container walls in the heat transfer process, was investigated for seven different beds of spheres. The serious effect associated with brass walls was rendered almost insignificant by the use of perspex packing containers. The thermal end effects associated with air flow through a two-layer perspex-walled assemblage were practically eliminated by the addition of three inert layers at the bed entrance and two at the exit. Part of the apparent reduction in the heat transfer factor with the addition of inert layers to the shallow bed was attributed to a decrease in driving force caused by the development of perfect void-cell mixing within the bed. The residual difference in jH between the unguarded and guarded forms of the shallow bed was attributed to a decrease in the coefficient of heat transfer brought about by the removal of the sudden contraction and expansion of the air from the active portion of the bed. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Effect of packing geometry on heat and mass transfer in stacked beds of spheres

Komarnicky, Walter January 1956 (has links)
Experimental measurements have been made of the simultaneous rates of mass and heat transfer for the surface evaporation of water into air from a simple cubic, a rhombohedral, and two orthorhombic assemblages of uniform celite spheres, in the particle Reynolds number range 300-1200. The measurements were confined to the pre-determined constant rate drying period of the spheres. No appreciable differences in mass and heat transfer factors were found for the various assemblages, except for the cubic, which exhibited lower transfer factors at the higher Reynolds numbers. This is explained qualitatively by the fact that the cubic configuration shows a considerably larger free projected cross-sectional area than the others, thus allowing for greater fluid channelling. Various methods proposed by investigators of randomly packed beds for correlating mass transfer by the inclusion of fractional void volume functions in the mass transfer factor and/or the Reynolds number were tested for the stacked assemblages. None of these methods completely correlated the results. Galloway's fluid friction data for the two orthorhombic assemblages were recalculated and showed similar friction factors to those obtained by Martin for identical packings of brass spheres. Ergun's criteria for complete and for no longitudinal fluid mixing were applied to the various assemblages. The results for the cubic assemblage suggest the possibility of considerable air mixing therein. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Effect of orientation on heat and mass transfer in stacked beds of spheres

Galloway, Leslie Robert January 1955 (has links)
Heat, mass and momentum transfer rates have been measured in two stacked beds of porous spheres having equal fractional void volume but different orientation with respect to the direction of fluid flew. An air-water system was studied under essentially adiabatic conditions over a Reynolds number range 100-1200. Orientation had negligible effect on heat and mass transfer rates though considerable effect on friction factor. An explanation for this behaviour is presented in terms of a difference in the degree of turbulent wake formation for the two assemblages, similar to that observed in comparable banks of closely packed staggered and in-line heat exchanger tubes. The experimental results contradict simple analogies between momentum, heat and mass transfer which show a direct proportionality between total friction factor and heat and mass transfer factor. Measured friction factors were about 50% in excess of those obtained by Martin for similar assemblages of smooth metal spheres. This is explained by the higher surface roughness of the refractory-like spheres used in the present investigation. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

The effect of wall roughness on heat transfer in pipes

Smith, James Wilmer January 1955 (has links)
Heat transfer and friction data were obtained for air flow through seven commercial pipes with equivalent sand roughness ratios varying from 0.020 to 0.00041 in the Reynolds number range 10,000 - 80,000. Heat transfer for a given power loss decreased with increasing roughness ratio except at very high power losses, where this trend was to some extent reversed. The results for the Karbate pipe were somewhat out of line with those for standard pipes. This is attributed to a difference in the nature of the Karbate roughness. In the plots of friction factor and j[subscript H] versus Reynolds number, the experimental data show that j[subscript H] continues to decrease with Reynolds number when friction factor has become constant for a rough pipe. This fact contradicts not only Reynolds' simple turbulence analogy and Colburn's modification thereof, which are in other respects inapplicable, but is also at odds with the more rigorous analogy of Taylor and Prandtl and the similar, semi-empirical equation of Pinkel. It is, however, in agreement with the Karman analogy, which also gives a good absolute prediction of the heat transfer data. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Some measurements of heat transfer to air flowing parallel to a tube bundle in square array

Chandrasekharan, Kuppanna January 1958 (has links)
Heat transfer measurements were made in a heat exchanger where air flows parallel to an unbaffled tube bundle and where steam is condensing inside the tubes. The tubes were one-inch outside diameter and were arranged in a square lattice with one-inch clearance between adjacent tubes. The Reynolds Number range covered in this investigation was 630 - 8220. Pseudo-j(h)-factors have been calculated for the air film in the central unit cell and are presented along with the results of Miller et al and Inayatov and Mikeev, who worked with other lattice arrangements. The present data are insufficiently numerous and too unreliable for empirical correlation, but they do show a trend which is consistent with the work of the above investigators. The temperature measurements showed an apparent dissymmetry inside the shell of the heat exchanger, and suggestions are made for the improvement of these measurements for more dependable results. Further work that can be done, using the present set-up with slight modifications, is also cited. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Direct contact, liquid-liquid heat transfer to a vapourizing, immiscible drop.

Adams, Arthur Edward Steele January 1971 (has links)
This thesis presents a study of some of the factors affecting direct contact, liquid-liquid heat transfer from a continuous phase of 0.0%, 56.02%, 73.07%, and 77.06% glycerine-water solutions to a dispersed phase, which is vapourizing, of isopentane or cyclopentane. An average heat transfer coefficient based on the initial area, the total evaporation time, the total heat transferred, and the .temperature driving force at the end of evaporation was calculated. This coefficient was correlated to the parameters of the systems by the dimensionless groups of continuous phase Prandtl number, dispersed phase Prandtl number, and a viscosity ratio. The results are compared to the works of Klipstein, Sideman and Prakash. A comparison made between the photographic and dilatometric method of volume measurement showed the dilatometric method to be the best for this type of work. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Variable-property flow and heat transfer to single spheres in high temperature surroundings

Sayegh, Namir Najib January 1977 (has links)
No description available.

Heat transfer aspects of drying and processing by immersion in a particular medium.

Richard, Paul. January 1981 (has links)
No description available.

Experimental study for the fully-developed single-phase heat transfer and friction factor in micro-fin tube

Chu, Wun Wai January 2011 (has links)
University of Macau / Faculty of Science and Technology / Department of Electromechanical Engineering

Steady state and dynamic behaviour of poor boiling processes

Poon, Kwan-leung., 潘君亮. January 1970 (has links)
published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

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