Thermal evaluation of an integrated heat pump and thermal storage system with alternative refrigerant R290 for heating applications

This study integrated heat pump and thermal energy storage (TES) system using a shell-and-coil multipass heat exchanger. Here, paraffin wax (Suvarna Bheem™ 35P) was chosen as the phase-change material (PCM) for the TES unit. The experimental setup included a reciprocating compressor, a plate heat exchanger serving as the condenser, and an evaporator. The refrigerant R290 was used in the heat pump as an ecofriendly alternative owing to its low global warming potential and zero ozone depletion potential. The heat exchanger was designed with a PCM capacity of 200 kg to provide a thermal storage potential of 28.6 MJ. Water was used as the heat transfer fluid (HTF) in both the condenser and TES system. The HTF absorbed heat from the condenser and transferred it to the PCM, such that the energy was stored in both sensible and latent forms. We performed computational fluid dynamics analysis to validate the experimental findings; the results showed that the average theoretical coefficient of performance (COP) of the heat pump was 4.0, while the actual average COP was 2.6, with the observed deviation attributable to system irreversibilities. The average hourly heat transfer to the TES was recorded as 3,481 W, and the condenser supplied the HTF at an average temperature of 63.3 °C. Thus, for heating applications, we recommend employing PCMs in TES systems by highlighting their significant potential for recovering waste heat from heat pump condensers.