Experimental study on a cold storage system with a variable speed compressor

Selection of a compressor for a refrigeration system is generally done based on a peak load operating condition. The energy consumed by the compressor can potentially be reduced by regulating the compressor speed using an inverter. This experimental study investigates energy saving and performance enhancement potentials in an experimental cold-storage system when the electric frequency supply is reduced from 45 to 25 Hz, with a 5 Hz interval. The system is equipped with a compressor with a power rating of 3 HP (2.25 kW) and R22 was used as the refrigerant. The cooling load of the system was provided using an electric heater placed at the bottom of the cold storage chamber. Results show that the power input to the compressor was reduced when the electric frequency supply was decreased. The highest reduction in the compressor power input occurred when the electric frequency was decreased from 45Hz to 40Hz. The results also show that the coefficient of performance (COP) of the cold storage system was improved when the electric frequency supply was decreased. The largest COP improvement occurred when the frequency was decreased from 30 Hz to 25 Hz