A packed condenser and the auxiliary equipment were designed, built and tested for the condensation of steam in direct contact with Aroclor 1242 and 1248, which are commercial heat transfer agents and are immiscible with water. The co-current flow of steam and liquid, through a four inch inside diameter column packed with three-eighth inch ceramic Raschig rings, was studied. The packing heights used in the condensation of steam were estimated from the liquid temperature profile in the column. The heights of the transfer units for condensation and the average volumetric overall heat transfer coefficients were calculated. The height of the transfer unit for condensation was found to be affected largely by the mean viscosity and the flow rate of the liquid. Two empirical equations have been developed to describe the results of this study. HCU = F ( μ ) (n) where n = 1. 10 for Aroclor 1242 and n = 1. 16 for Aroclor 1248 is mean viscosity of the Aroclor in centipoise. For Aroclor 1242, F= 0.0535 + 8.90 x l0⁻⁶ L when L ≤ 2290 and F =-0. 0737 + 6. 44 x 10⁻⁵ L when L > 2290. For Aroclor 1248, F = 0. 02765 + 1. 244 x 10⁻⁵ L. L is superficial mass velocity of the Aroclor in lb /hr. ft² / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

No description available.

Condensation on banks of tubes is of considerable interest in the power, refrigeration and process industries, where large scale condensers form a significant proportion of plant capital costs. Since the pioneering paper by Nusselt in 1916, numerous investigations, both experimental and theoretical, have made great inroads into the understanding of the important physical factors effecting performance, including effects of vapour shear and condensate inundation on heat-transfer performance. Despite this there are still significant gaps in the knowledge and no single recognised design approach exists for condensers under all conditions. Purely theoretical models have shown some success in modelling condensation on single tubes under high shear regimes, but these have not been successfully extended to full tube banks. The present work begins by drawing together a comprehensive data base of experimental results from those available in the literature. This includes assessing the experimental accuracy of the data and organising it into a consistent format to allow detailed comparison with existing and future models. The resulting data base comprises 13 tube bank geometries, 7 test fluids and over 4000 individual data points. The data base was used to evaluate existing theoretical and empirical models, and highlighted the weaknesses therein. In particular, it was found that empirical approaches were limited to application (ie refrigeration or steam condensers), with development and validation being based on experimental data for single fluids or groups of fluids. When these models were compared to the more comprehensive data base described above their performance was poor. Consequently there is limited confidence in their extension to applications outside those they were developed for. A new empirical based model was then developed. The approach involved identifying relevant dimensionless groups to account for the various physical factors which may affect heat transfer during condensation on a bank of tubes and formulating these into an equation involving a number of initially unknown but empirically obtainable constants. An iterative scheme was then employed to eliminate those groups having little effect on the result while retaining those which proved to be more important. The resulting model predicted the majority of the experimental data base to around 12%. A subsequent parametric study 3 showed the correct dependence of heat transfer coefficient on factors such as vapour velocity and tube row. The thesis concludes with some suggestions for future work.

Digitized by Kansas Correctional Industries

Thesis (M.S.)--Mississippi State University. Department of Mechanical Engineering. / Title from title screen. Includes bibliographical references.

No description available.

Research to date has highlighted a number of conditions where dropwise condensation may offer heat transfer enhancements over filmwise condensation. Previous studies have shown at pressures above or around atmospheric, dropwise condensation offers significant benefit over filmwise. However, some of this research suggests that as the system pressure is reduced below atmospheric, the benefits of dropwise condensation diminish rapidly, to the extent that, at pressures around 50mbar the benefits of dropwise over filmwise are minimal. This thesis details a series of experiments which were conducted to investigate the heat transfer and pressure drop distributions in tube bundles during both dropwise and filmwise condensation of steam. The primary objective of the work was to determine the design implications associated with switching the mode of condensation of a electricity generating steam turbine condenser from the current filmwise mode, to dropwise. Experimental data were obtained from a new purpose build apparatus containing seventy-five, 150mm long titanium tubes, arranged in an in line configuration of five columns and fifteen rows. Dropwise and filmwise data were recorded from each row at test cell inlet pressures down to 50mbar using both pure steam and steam air mixtures. Filmwise heat transfer data indicated that, under most conditions, heat transfer coefficients were generally in agreement with those obtained by previous workers. Heat transfer data obtained during dropwise condensation suggested that the benefits of dropwise condensation are not significantly diminished at low pressure, and that, unlike filmwise condensation, inundation has little or no effect in a fifteen row bundle. The data also indicated that the pressure drop characteristics and effects of air are, within experimental error, identical during both modes of condensation and in line with models and theories proposed by previous workers.

Thesis (M.S.)--Rochester Institute of Technology, 1995. / Typescript. Bibliography: leaf 54.

No description available.

For many years it has been known that the complete charging and discharging of a condenser with complex dielectric involved a time element. Particularly, it was noted that a condenser could be discharged to zero potential, allowed to stand for an interval of time and a discharge then secured from the condenser. In some cases even after months a discharge could be obtained. The accumulation of such a charge on a condenser is spoken of no residual charge or dielectric absorption. The Lyden jar was used extensively in the early work on residual charge. Physicists such as Benjamin Franklin, Faraday, and Maxwell recognized this. In fact Maxwell gives us the first attempt ever made at a theoretical explanation of the phenomena of absorption.¹ Today this is the principal theory recognized in the Physics world for this phenomena. It was not until the day of speech communication over long distances that a study of the dielectric was given considerable attention. Theories have been developed for the explanation of dielectric absorption, some of which will be mentioned later. Even today large inconsistencies are found to exist between theory and experiment in this field of work. There are numerous factors upon which dielectric absorption depends. Some of these are, material or dielectric, previous history, charging potential, moisture content, air content, charge time, discharge time, recovery time, and temperature. It is the purpose of this paper to present results of experiment and to state conclusions drawn from work on temperature effects on residual charge of a paraffin paper dielectric. Through the study which has been made of this phenomenon it is felt information has been gained which can be added to our now small understanding of absorption. / Master of Science