Faster Cool-Down of a Reefer Unit by Optimizing the System Losses through Experimental Investigation

Refrigerated shipping containers are one of the four segments of the cold chain; cooling and storage; refrigerated transport; distribution centre and refrigerated display in super markets. The term reefer has become an established term to refer refrigerated shipping containers. It is one of the emerging areas in transport segments. With the onset of ongoing pandemic this area has further drawn global attention recently and due focus is being given to the development and improvement of reefer unit Hence with the growing demand in this field the energy consumption is also leapfrogging day by day. Primary energy sources (fossil fuel) are depleting and their environmental impact is raising anxiety around the world. In order to minimize unnecessary energy waste in refrigerated shipping container system, it needs to be designed to be energy efficient and provide high cooling capacity to ensure rapid pull down to carriage temperature and to maintain product quality at idle. Improper operation and design cause a significant waste of energy. This avoidable waste of energy results in unnecessary economic loss. An experimental investigation was conducted in the present paper in order to minimize the energy consumption to run the system at idle condition and to achieve the faster rate of cooling. An existing reefer system was considered for this study. The existing system was designed for small container, size upto 8 ft, was first evaluated experimentally in the climatic test chamber under different climatic conditions resembling actual ambient usage. The experimental data was analysed in details and all concerned areas were identified such as losses in suction lines, ineffective utilization of condenser frontal area, air-bypass from evaporator coil and compressor being exposed to hot air etc. Appropriate countermeasures were taken to eliminate these losses and system was modified with these changes. Further the modified system was tested again in climatic test chamber. It was observed that the rate of cooling is much faster than that of existing and also the energy consumption to reach to the desired container temperature is significantly lower as compared to the existing system. Energy required to maintain at low speed e.g. idle is also minimized. Hence the study was quite useful in establishing design measures at the initial stages of development.