Thermodynamic Analysis of Cascade Refrigeration System for Low Temperature Applications

Abstract

In recent years, concern about global warming and ozone layer depletion has been growing. Increasing attention is being given to refrigerants used in refrigeration and air-conditioning systems as they have a signi cant contribution towards these environmental issues. As industries and di erent chemical plants are increasing day by day, it is becoming a challenge for researchers to nd suitable refrigerants that will be safe for the environment and maintain the desired performance. In the case of di erent ultra-low temperature (-100oC to -150oC) applications (e.g., LNG, LPG liquefaction, cryogenic engineering, food, and medicine storage), it is even more challenging to satisfy environmental conditions and performance. This study aims to nd suitable environment-friendly refrigerants and implement them in a triple cascade refrigeration system (TCRS) for low-temperature application (-100oC to -150oC). For this purpose, a simulation model for the system was developed and validated. Based on low global warming potential, and low ozone depletion poten- tial; eco-friendly hydrocarbon (HC) refrigerants were selected for implementation in the triple cascade refrigeration system (TCRS). In the lower temperature cir- cuit (LTC), 1-butene was used as working uid, and in the higher temperature circuit (HTC), m-Xylene was used. For the mid-temperature circuit (MTC), trans- 2-butane, n-heptane, n-butane, cis-2-butane were used. To assess the performance of TCRS, energy analysis and exergy analysis were conducted, and analyzed. The results show that 1-butene/heptane/m-Xylene pair gives the best performance in terms of 1st law e ciency (COP) and 2nd law e ciency (exergy destruction) for 3 Triple Cascade Refrigeration System low-temperature applications (lower than -100°C). The results obtained from the simulation model suggests that exergy destruction mainly occurs at the condenser, hence further studies can be carried out on the condenser to increase the overall COP. Further experimental studies can be carried out to assess the feasibility of utilizing the proposed refrigerants pair for low-temperature applications.