A comparison of hot-gas by-pass and suction modulation method for partial load control in refrigerated shipping containers

Simulation studies using a mathematical model are made to compare the performance of the hot-gas by-pass control and the suction modulation control in refrigerated shipping containers. Key factors such as compressor power draw, coefficient of performance and the sensible heat factor of evaporator coil against variations in container load, set-point and ambient temperatures are examined. Results show that the suction modulation control strategy is the more energy efficient of the two. The evaporator performance is found to be largely unaffected by either strategy. The analysis indicates the possibility of controlling relative humidity in the cargo space by variation of the superheat level.