Refrigerant maldistribution in brazed plate heat exchanger evaporators. Part B: Analysis of the influence of maldistribution on the evaporator performance

Abstract

• Refrigerant maldistribution does not have always the same influence in evaporator performance. • The penalty of the maldistribution depends on the relation between superheat and water temperature drop. • Two parameters are used to characterize refrigerant maldistribution. • The conditions with 0 superheat do not show any degradation in the performance. • Higher qualities produces a better refrigerant distribution in the evaporator. The maldistribution of the refrigerant mass flowrate among the different channels of a brazed plate heat exchanger evaporator with distributor, has been studied with a thermographic camera working under different conditions of inlet vapor quality, superheat, and water temperature drop. Part A of this work includes the description of the experimental campaign and a full discussion of the obtained results. This paper (part B) presents, first an evaluation of the penalty caused by the refrigerant maldistribution on the evaporator performance, and the effect of the operation conditions on that penalty; second, a data reduction methodology, which allows the quantification of the maldistribution based on a series of simple assumptions and the flow conservation equations. Finally, given that it has been found that the water temperature drop across the evaporator has a strong influence on the performance penalty due to refrigerant maldistribution, the water temperature evolution is analyzed in detailed and the reasons for its great influence are explained and commented. On this regard, it is concluded that the penalty of the maldistribution on the evaporation performance strongly depends on the availability of the secondary fluid in the channels where most of the refrigerant liquid is concentrated. The described data reduction methodology, based on the analysis of the thermographies and the measured evaporator performance, is suitable to give an estimate of the maldistribution which seems reasonable and consistent with the observed data.