Author: Maciej Chwalowski

Publisher:

Published: 1991

Total Pages: 146

ISBN-13:

The design of the heat exchanger utilizing nonazeotropic refrigerant in an air conditioning application presents unique problems due to the phase change of the moist air and the variable specific heat of the evaporating refrigerant mixture. This study discusses the performance analysis and the design procedure of a cross counterflow heat exchanger working as an evaporator in an experimental system which simulated a residential air conditioning application. The design of the heat exchanger, used for the experimental testing, consisted of several depth rows. Separated banks permitted the determination of the sensible and the latent heat loads for each bank and the heat profiles across the heat exchanger. The interaction between the refrigerant mixture and the moist air was quantified by determining the temperature profiles of both media and the moisture removal rate. The overall heat transfer coefficient for each bank of the heat exchanger was determined from the measured quantities. The effect of the change of the mixture composition on heat exchanger performance was evaluated. The focus of the theoretical study was the development of the effectiveness/NTU (epsilon/NTU) relationships with the use of the experimentally derived quantities for moist air flowing across the heat exchanger. For moist air, the variable mixture specific heat, air and heat profiles obtained from the experimental results were utilized to obtain the expression for epsilon/NTU. The derived epsilon/NTU relations were verified and found to be in good agreement with dry and moist air test results. This study resulted an understanding of an application of a refrigerant mixture working fluid in an evaporator and provided tools to design such a heat exchanger.