Performance analysis of a CO2 based milk chiller with evaporative cooling arrangement operating in hot climate

In this paper, the cooling and heating performance of a parallel compression CO2 refrigeration system with a cooling capacity of 240 kW is analysed for milk pasteurization application. The system chills the milk to 4 ˚C and the recovered heat partially supports the pasteurization process or is used to heat the clean-in-place water. The annual performance of the system is evaluated theoretically for the hot climatic condition of Pilani (Rajasthan, India). It was found that for a system with an evaporative air-cooling arrangement, the CO2 exit temperature of the gas cooler during peak summer conditions of 51 °C ambient can be reduced by about 10 °C. This leads to an increase in cooling COP by an average of 48%, reduction in compressor work by 32% as well as a 21% improvement in the overall COP. The evaporative cooling reduces the compressor discharge temperature by 32 K and the discharge pressure by 2.2 MPa. These advantages are achieved with a water demand of about 264 litres/hr and reduced heat recovery potential of about 39%. Keywords: CO2 Trans-critical System, Evaporative Cooling, Parallel Compression, Milk Chilling, Split Gas Cooler