Heat transfer characteristics of horizontal in-tube evaporation
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Authors
Ha, Samchul
Issue Date
1992-08
Type
Electronic thesis
Thesis
Thesis
Language
ENG
Keywords
Mechanical engineering
Alternative Title
Abstract
Oil addition to pure refrigerant in smooth tubes altered the flow pattern dramatically at low mass fluxes: the flow changed from stratified/wavy or wavy flow to semi-annular flow, with a resultant enhancement of the wetting area by vigorous foaming. The coefficients of the mixture for low and medium qualities were 1.2 to 1.5 times higher than that of the corresponding pure refrigerant cases at low mass fluxes, but the enhancement was decreased with an increase in mass flux. However, the addition of the oil in refrigerant flow for the micro-fin tube reduced the heat transfer coefficient, with the most dramatic decrease at high qualities. A highly viscous oil-rich film around the entire perimeter of the tube was observed, and there was clear suppression of the normal foaming activity. The axial heat transfer coefficients of the mixtures in the micro-fin tube were about 1.5 times higher than those of similar mixture ins a smooth tube for a mass flux of 100kg/(m2·s).
Description
August 1992
School of Engineering
School of Engineering
Full Citation
Publisher
Rensselaer Polytechnic Institute, Troy, NY