Thesis (M.S.)--University of Michigan, 1962. / Project completed June 1961. Degree awarded Feb. 1962.

Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on March 13, 2008) Vita. Includes bibliographical references.

Heat Transfer Lab report ; no. 80047-99 / Sponsored by Empire State Electric Energy Research Corporation, New York.

No description available.

Fouling by a petroleum gas oil and a dilute suspension of sand in water was studied as a function of mass flow rate and wall temperature. The experiments were carried out by circulating the liquid through a single tube maintained at constant heat flux by electrical heating. The change in fouling resistance and pressure drop with time was measured. The fouling resistance of the water and of the oil at low heat fluxes grows to an asymptotic value. At higher heat fluxes the oil fouling resistance increased almost linearly with time after an induction period. The asymptotic fouling resistance of both the oil and the water decreased with increasing mass flow rate. At constant clean tube wall temperature the initial fouling rate of the oil decreased with increasing mass flow rate. The initial fouling rate of the water increased with increasing mass flow rate up to a critical mass flow rate, and then decreased with further increases in mass flow rate. At constant mass flow rate, the initial fouling rate of the oil depended exponentially on the clean tube wall temperature. An activation energy of 29 Kcal/mole was calculated for the oil fouling process by fitting the initial fouling rate data to an Arrhenius type of equation. The pressure drop increase showed the same general trends with mass flow rate and tube wall temperature as did the fouling resistance. Fouling resistances for heated Kraft cooking liquor, calculated from pulp mill operating data and from a single fouling experiment, appeared to follow similar trends to those, followed in common by the gas oil and the water. The experimental results of this study were compared to the mathematical model of Kern and Seaton. While the shape of most fouling curves was in agreement with that predicted generally by this model, dependence of the initial fouling rate and of the asymptotic fouling resistance of the gas oil on the mass flow rate were both in disagreement with the detailed predictions of the model. For low mass flow rates of the water, however, even the detailed predictions were borne out. It was, moreover, possible to remove part of the sand deposit by increasing the velocity of the water, in accord with the postulated removal mechanism of Kern and Seaton, but the coke-like deposit from the gas oil could not be similarly removed by increasing the oil velocity. Mathematical models are developed in which the deposition term is written as the product of a material flux to the wall region and a sticking probability, after Parkins, and the removal term depends on the shear stress, after Kern and Seaton. Specific cases are considered where deposition is controlled by transfer to the surface, adhesion at the surface, and a combination of both steps.. Where deposition is controlled partly by transfer and partly by adhesion, the model predicts mass flow rate and temperature dependence of the initial fouling rate in agreement with the experimental results found for the oil. The observed asymptotic fouling resistance of the oil, however, depended less strongly on the reciprocal of the mass flow rate than is predicted by the model. Where transfer alone controls the deposition process, the extended model reduces to a form similar to that of Kern and Seaton. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

The mathematical equations describing transient heat transfer between the fluid flowing through a fixed bed and a moving bed of packing were formulated. The resistance to heat transfer within the packing due to its finite thermal conductivity was taken into account. An approximate integral method was applied to obtain an analytical solution to transient response of the bed packing. Results for two cases of fixed and moving bed were obtained. The validity of the approximate method was checked against the more exact method employed by Handley and Heggs who obtained the results for a fixed bed of packing with a step change in fluid inlet temperature. It was concluded that the approximate method gives results that agree well with the more exact methods. The method considered here provides a quick determination of the packing mean temperature in order to obtain the effectiveness. The other peculiarity of this method is that the effect of packing thermal conductivity can be examined very quickly since the solution is in analytical form. The analysis of the results revealed that as the thermal conductivity of the packing decreases the difference between its surface and mean temperature increases. A series of charts showing the comparison between the packing surface and mean temperatures for different thermal conductivities are presented. The approximate method was a moving bed of packing. It was packing thermal conductivity is series of charts representing versus dimensionless length conductivities are presented. then applied to the case of concluded that the effect of more severe than expected. A the moving bed effectiveness for different thermal / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

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No description available.

PhD, Faculty of Engineering and the Built Environment, University of the Witwatersrand / In this study the heat transfer and frictional pressure drop performance characteristics of plate heat exchangers (PHE’s) used as refrigerant liquid overfeed evaporators were investigated. PHE’s have been gaining new applications in the refrigeration industry, especially as evaporators, during the last few decades, but the available information in the open literature for operation in this mode is rather limited. This study aims to extend the knowledge of PHE evaporator performance and to develop a model for use in evaluating heat transfer and pressure drop over as wide a range of operating conditions as possible. A laboratory experimental facility was constructed and the thermal-hydraulic characteristics of three middle-size industrial PHE’s were measured. The exchangers all had 24 plates of the same size but with different chevron angle combinations of 28°/28°, 28°/60°, and 60°/60°. Two sets of tests were carried out with the three units: single-phase performance tests with water, and evaporator performance tests with R134a and R507A, for which the exchangers operated as refrigerant liquid over-feed evaporators. The tests with water served to provide accurate water-side heat transfer information for the evaporator performance analysis which is the primary purpose of this study. In the evaporator performance tests, refrigerant flow boiling heat transfer and two-phase pressure drop data were obtained under steady conditions, over a range of heat flux from 1.9 to 6.9 kW/m2, refrigerant mass flux from 5.6 to 31.4 kg/(m2s), outlet vapour quality from 0.2 to 0/95, and saturation temperatures from 5.9 to 13.0 °C. Additional field data of thermal performance were collected on an ammonia and a R12 PHE water chiller, operating as thermo-siphon evaporators at their design working conditions. All experimental data were reduced and analyzed to obtain the refrigerant-side heat transfer coefficients and frictional pressure drops in the PHE evaporators. The heat transfer results showed a strong dependence on heat flux and a weak dependence on mass flux, vapour fraction and the chevron angle. Along with the ii observations from the ammonia and R12 evaporators, it is concluded that the dominating heat transfer mechanism in this type of evaporator is nucleate boiling rather than forced convection. In contrast to the heat transfer characteristics, the refrigerant two-phase frictional pressure drop was found to be strongly influenced by mass flow rate, vapour fraction and also the chevron angle. An almost linear increase of the frictional pressure drop with the homogeneous two-phase kinetic energy per unit volume was observed for both refrigerants. Based on the experimental data, correlations were developed for predicting the refrigerant boiling heat transfer coefficient and two-phase frictional pressure drop in PHE liquid over-feed evaporators. Two correlations were developed for boiling heat transfer, one of these reflecting the h-q relationship in pool boiling, the other with all constants and exponents determined by regression analysis. The mean absolute errors are respectively 7.3% and 6.8% for these correlations. For two-phase frictional pressure drop, data were correlated using two established methods, namely the homogeneous and the Lockhart-Martinelli methods, with means absolute errors of 6.7% and 4.2%, respectively. The homogeneous model showed a slightly higher discrepancy with the experimental data but is likely to be more physically sound for PHE evaporators, and is much simpler to apply. Validation of these correlations with other data has been difficult due to the shortage of published information. For other refrigerants operating at comparable conditions, these correlations should serve as a guide, while more accurate design or evaluation may need to be based on further testing. The performance analysis carried out in this study was based on systematic experimental investigations and field tests on industrial PHE units. Correlations were developed covering a rather extensive range of flow parameters, plate geometry and various refrigerants. Such correlations have not been reported previously for PHE liquid over-feed evaporators. The results simplify the performance analysis of PHE evaporators and provide a reliable thermalhydraulic model of PHE liquid over-feed evaporators, which can be used for system modeling of water-chilling machines employing this type of evaporator.

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