Conference Year
2018
Keywords
plate heat exchangers, zeotropic mixtures, flow maldistribution, evaporators
Abstract
This paper presents an estimation of the degradation in heat transfer performance in plate heat exchanger (PHE) evaporators due to flow maldistribution. A booster heat pump system integrated in a district heating network is used as a case study. Butane and two zeotropic mixtures, namely Propylene/Butane (0.5/0.5) and R1234yf/R1233zdE (0.5/0.5) were evaluated as working fluids. The PHE was preliminarily sized for all the refrigerants by considering a fixed plate geometry from a commercial manufacturer. A two-dimensional (2D) numerical model was developed for the evaluation of the total heat flow rate degradation due to the imposed uneven liquid/vapor distribution at the inlet of the PHE channels. Butane showed the most sensitivity to both the effect of end plates and maldistribution, with an overall reduction of the heat flow rate equal to -11.2 %. Both the zeotropic mixtures were insignificantly affected by the uneven quality distribution at the inlet, and suffered a slight reduction of the overall heat flow rate of -0.861 % and -0.779 %, due to effect of end plates. Last, the sensitivity to the boundary conditions of the case study was assessed for the mixture Propylene/Butane (0.5/0.5), evaluating the dependence of the obtained results from superheat and number of channels, since both parameters impact the degradation of heat transfer performance