Refrigeration system development with limited charge of flammable Refrigerant, R-290

Recently, natural refrigerants have gained a significant attention as a future alternative because of their performance and environmentally friendly characteristics; No Ozone Depleting Potential and near zero Global Warming Potential. The present paper reports an experimental study performed with refrigeration systems developed using one of natural refrigerants, R-290 (Propane & GWP = 3), particularly with the limited charge amount to meet the most stringent regulatory requirement, IATA Dangerous Goods Regulation. Under IATA regulation, refrigerating machines and components containing flammable gas are forbidden for international air freight unless the flammable charge shall be less than 100 g. Two types of standalone system were developed, so called Liquid Circulating Chiller and Air-Air Cooler. Both were with air-cooled condensers. Liquid Circulating Chiller consisted of a liquid cooled evaporator (liquid to liquid heat exchanger) while Air-Air Cooler came with an air-cooled evaporator (air to liquid heat exchanger). All component selections were made to achieve the minimum refrigerant charge and as a result, the total system charge was kept around 100 g or less. During the system development, several combinations of the components were considered (e.g., compressors and heat exchangers), and system developed was tested under various test conditions as a part of the system optimization. From the study, the maximum cooling capacity achieved was around 3 kW with less than 100 g of R-290 refrigerant charge.