Multi-mode analysis of a CO2-based combined refrigeration and power cycle for engine waste heat recovery

Abstract

To realize the adjustable allocation of refrigeration and power in a combined refrigeration and power cycle, this study proposes a multi-mode cycle using CO2 as the working fluid. A refrigerated truck is selected as the research objective, the refrigeration demand and power demands of which vary frequently with different transportation conditions. The proposed system is driven by the exhaust gas of the main diesel engine and can replace the original refrigerator and related small-scale diesel engine. Three operating modes can be realized for different energy demands: full refrigeration output, combined refrigeration and power output, and full power output. The results indicate that the proposed system exhibits considerable potential for energy saving and diversified energy supply capacity. Following optimization of the configuration and parameters, the proposed energy solution (engine + proposed system) under the mode of combined refrigeration and power output can achieve a 2.9% fuel saving and 4.8% power increase simultaneously versus the original energy solution (engine + refrigerator) under refrigeration condition, 3.4% fuel saving and 1.6% power increase simultaneously under freezing conditions. The fuel economy is correspondingly improved 7.4% and 4.9%. Moreover, the proposed method can provide greater refrigeration and power capacities under the full refrigeration output and full power output modes.