R32 System Performance, heat transfer
An advanced simulation model of a packaged air cooled water chiller was developed. The nominal cooling capacity of the chiller is about 70 kW at 35°C dry bulb outdoor air temperature, and it consists of a single refrigerating circuit with two identical scroll compressors. The compressor was characterised by its experimental performance curve according to EN 12900 for both R410A and R32. Off-the-shelf copper tubes and louvered aluminium fins were considered for the condenser and typical brazed plate configurations for the evaporator. The finned coil condenser and the brazed plate heat exchanger evaporator were modelled by an elementary finite volumes technique, previously validated in other papers; for each volume the heat transfer coefficient and the pressure drop were calculated using semi-empirical correlations chosen among the most accurate ones available in the open literature. The aim of the paper is to compare the performance of R410A with that of R32 which is considered as a possible HFC substitute with lower GWP (675 instead of 2088). The condenser was optimised for R410A and R32 independently with regard to the number of internal circuits according to the so-called Performance Evaluation Criteria , without changing the overall heat exchanger dimensions. An analysis of the seasonal efficiency for each finned coil circuitry configuration (both with the same compressors) was carried out in terms of European Seasonal Energy Efficiency Ratio (ESEER) calculated according to the EN 14825 specifications for water chillers. We were able to conclude from that modelling work, that R32 system efficiency performance is acceptable as alternative to R410 for water chillers and further simulation analyses will include evaluating HFO blends.