Thermodynamic analysis of a combined supercritical CO2 and ejector expansion refrigeration cycle for engine waste heat recovery

• Published in: Energy conversion and management Vol. 224; p. 113373
• Main Authors: Pan, Mingzhang, Bian, Xingyan, Zhu, Yan, Liang, Youcai, Lu, Fulu, Xiao, Gang
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 15.11.2020; Elsevier Science Ltd
• Subjects: Brayton cycle; Carbon dioxide; Ejector expansion refrigeration cycle; Exergy; Food preservation; Heat; Heat recovery; Heat recovery systems; High temperature; Inlet pressure; Pressure; Pressure drop; Refrigerated trucks; Refrigeration; Regenerative supercritical CO2 Brayton cycle; Topping cycle; Trucks; Turbines; Waste heat; Waste heat recovery; Weight; Zeotropic mixtures; Regenerative supercritical CO2 Brayton cycle; Ejector expansion refrigeration cycle; Waste heat recovery; Refrigerated trucks
• ISSN: 0196-8904; 1879-2227
• DOI: 10.1016/j.enconman.2020.113373

•A novel heat recovery system is proposed for refrigerated trucks.•CO2-based zeotropic mixture is used in the bottoming refrigeration cycle.•Thermodynamics and weight estimation analysis are conducted.•The proposed system shows great potential in providing refrigeration in mobile system. An engine waste heat driven combined power and refrigeration system, comprised of a regenerative supercritical CO2 Brayton cycle (RSCBC) and an ejector expansion refrigeration cycle (EERC), is proposed. In this system, the RSCBC is adopted as the topping cycle to generate power by recovering the high-temperature waste heat of engine. Meanwhile, the power is utilized by the compressor in the EERC. Such a waste heat recovery system can not only decrease the specific fuel consumption, but also provide refrigeration for refrigerated trucks to realize food preservation. Energy and exergy analysis are conducted on the RSCBC/EERC. The performance of four zeotropic mixtures used in EERC and different mixture compositions are compared. Moreover, the effects of several significant operating parameters are discussed in detail, including turbine inlet pressure and temperature, compressor inlet pressure and temperature, pressure drop in the ejector, evaporating temperature, and condensing temperature. To investigate the influence of the installation of the RSCBC/EERC system, weight estimation analysis is conducted. The results show that the refrigerating capacity and COPcomb of the system with R32/CO2 (0.9/0.1) are up to 225.5 kW and 2.05, respectively. And the equivalent power loss due to the additional weight is estimated to be 5.21 kW. In general, the RSCBC/EERC has proven its application potential in recovering waste heat to provide refrigeration through thermodynamic analysis.