Enhancing the performance of a CO2 combined refrigeration and power (CRP) cycle driven by engine exhaust gas by using heat exchangers in optimized locations

Abstract

Carbon Dioxide (CO2) has proven its efficiency as a working medium for power and cooling productions in vehicles and refrigerated trucks driven by engine exhaust gases. The main drawbacks of this system are the high/low critical pressure/temperature of the CO2 which leads to high compressor power and low efficiency. In the present paper two modifications by insertion of two heat exchangers in bottom and top CO2 compound cycles driven by engine exhaust gas are proposed to overcome on these drawbacks. Energy and exergy analysis are used to evaluate and compare their performances with the basic system. The results show that (i) the feasibility of using the proposed systems was justified and has proven potentials of energy and fuel consumption saving compared to traditional engine + stand-alone refrigerator, (ii) proposed modifications on the basic system (System I) by incorporated heat exchangers (System II and System III) has proven its potential for higher energy efficiency and refrigeration capacity and can recover about 18.33%, 20.38% and 19.22% of the energy of the exhaust gases for driven the compound CO2 cycle, (iii) parametric, comparison and optimization studies, showed that the proposed system (system II) has the highest refrigeration capacity, energy efficiency and fuel consumption cost saving with optimal values of 20.4%, 0.1819 kg/kWh, 7.1%, respectively.