Dynamic Modeling and Control Strategy of a Transcritical CO_2 Cycle for a Multi-Temperature Refrigerated Container System for Military Applications

摘要

A transcritical carbon dioxide (CO_2) refrigeration cycle has been investigated for applications in U.S.Army Multi-Temperature Refrigerated Container Systems (MTRCS). The cycle configuration hasbeen optimized to meet both environmental and energy efficiency targets. The proposed transcriticalCO_2 cycle utilizes an axial multi-piston compressor-expander based on the Sanderson Rocker ArmMechanism (S-RAM) that enables expansion energy recovery. The cycle features three compressionstages, intercooling between the 2nd and 3rd compression stages, flash tank economization, andexpansion work recovery. The numerical optimizations led to a maximum coefficient of performance(COP) of 1.0 at an ambient air temperature of 57.2 °C. Due to the complexity of the cycle, a dynamicmodel of the system was developed to investigate different control strategies. Simulation resultsshowed that the system was able to operate with adequate compressor suction superheats and flashtank liquid under excitations as well as varying operating conditions applied to both evaporators.