Performance analysis of an ejector based CO2 transcritical refrigeration system with integrated mechanical subcooling for dairy application

Abstract

Refrigeration system plays a crucial role in the dairy sector to preserve quality and prevent spoilage of milk. This sector also have enormous heating requirement for various processes such as pasteurization and heating of water for cleaning. The carbon dioxide (CO2) based refrigeration system is perceived to be an excellent choice for dairy application since it can simultaneously meet the cooling and heating demand. In the present study, a novel ejector based CO2 transcritical refrigeration system with integrated mechanical subcooling (IMS) is proposed for dairy applications. With IMS, the heating capacity of the refrigeration system is improved since the heat removed for subcooling can also be rejected into the heat recovery unit. The proposed system chills milk to 4 °C and simultaneously supply heat to water that can support various heating requirements. A parametric analysis of the proposed system is carried out and the results are analysed to comprehend the effect of ambient temperature, gas cooler pressure, effectiveness of the heat recovery heat exchanger and degree of subcooling on various performance parameters. It was found that the proposed system could heat water up to 80 °C and achieve an overall coefficient of performance of 4.15 at an ambient temperature of 40 °C. The study concludes that the proposed system is an energy efficient and clean alternative to conventional refrigeration and heating systems.