Investigation of economizer with screw compressor to provide subcooling and enhance cop in various natural refrigerant-based cascade freezer

Abstract

This study examines two configurations of a cascade refrigeration system using natural refrigerants-R744 in the low-temperature circuit (LTC) and one from this list of R717, R290, R1270, or R600a in the high-temperature circuit (HTC). The motivation behind the design of the two configurations is the subcooling provided by the internal heat exchanger (IHX) and economizer for the natural refrigerant combinations, which is the novelty of the work as well. Both configurations have a single low-temperature evaporator at − 45 °C and operate in a warm ambient of 45 °C. One of the configurations has two IHXs, one in the LTC and the other in the HTC and a desuperheater at the LTC compressor exit and is termed as IDI. The second configuration has an economizer in the HTC and an IHX in the LTC along with a desuperheater at the compressor exit and is termed as IDE. The configurations are compared in terms of energetic and exergetic performance. Among the configurations, the overall COP is found to be the maximum for the IDE system for all refrigerant pairs while R744/R600a outperforms others for both IDI and IDE configurations. The highest overall COP for R744/R600a is 1.21, while it is 1.29 for the IDE exhibiting a 6.6% improvement.