Abstract
Required refrigerant charge in heat pump systems with propane is analyzed. Two systems are compared: the first a direct heat pump, with fin-and-tube heat exchangers, and the second an indirect system, with plate heat exchangers with an additional brine-to-air heat exchanger. Each system was considered to be able to work reversibly, with 5 kW design cooling capacity in summer and 8 kW design heating capacity in winter. Two separately developed simulation codes were used to calculate the required refrigerant charge and the efficiency of each of the systems. The charge was reduced by the use of microfinned tubes up to 22% in direct system reduced using microfinned tubes compared to the smooth tube. For the indirect system using specially designed plate heat exchangers with the minimum internal volume, their charge was reduced by up to 66% compared to normal plate heat exchangers.
Highlights
Version 3.9.0 developed by the Universidad Politecnica de Valencia (UPV) which is a commercial tool for the design and optimization of refrigeration cycles [31]
As for the plate heat exchangers, BPHE3 performs slightly worse than the other plate heat exchangers which is again caused by the slight variation in saturation temperatures
System B was simulated with three brazed plate heat exchangers with different internal volumes
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Studies have shown that the majority of charge is stored in heat exchangers [5,6], minimizing the heat exchangers’ volume seems to be the most effective method of increasing the capacity of these systems with regards to limitations on their charge. This is even more critical in the condenser’s case as it could contain 50% of the total charge [6]. These utilized models were based on correlations developed by experimental data on two-phase flow of propane
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