A Hybrid Ejector and CO2 Compression Refrigeration System

The proposed project aims to investigate a high-performance, low energy refrigeration system for refrigeration in general and for food transport vehicles in particular. The proposed system is based on the integration of a trans-critical CO2 mechanical driven compression cycle and a compact ejector cooling system. The system will be driven by heat rejected from the vehicle exhaust system and heat recovered from the CO2 gas in the mechanical compression cycle. The ejector evaporator replaces the ambient air in the CO2 mechanical compression cycle, by utilizing the cooling effect produced in the ejector cycle to provide sub-cooling of the high-pressure CO2 fluid below ambient temperature. This is thought to help improve the performance of the CO2 cycle. The ejector cycle is integrated in a way to enhance sub-cooling of the high pressure gas, but not to limit the overall system performance to that of the ejector cycle. The system could be operated using two working fluids i.e., CO2 for the mechanical compression cycle and an environmentally friendly working fluid e.g., water or methanol. The proposed system is efficienct, compact and requires minimal energy to operate, features which make the system particulary suitable for applications in transport vehcles. The research programme will involve:1. Thermodynamics and energy transfer analysis of the combined CO2 mechanical compressor -ejector refrigeration system2. Computer modelling for components sizing and performance analysis of the combined refrigeration system.3. Laboratory evaluation of the performance of the system components;4. Analysis of the environmental impact of application of the system.Development of the proposed system would enable refrigeration to be provided for food storage in food transport vehicle with minimum energy consumption owing to utilisation of the waste heat and improvement of the performance of the CO2 mechanical compression cycle. The improved system performance would reduce energy consumption in this sector and also reduce the impact of the global warming attributed to the use of HFC refrigerants.