Energy saving in refrigeration systems through the application of liquid pressure amplification

Abstract

The LPA technology utilises a refrigerant pump in the liquid line after the receiver to maintain a high enough pressure differential across the expansion valve to compensate for the pressure drop in long liquid lines. This allows the condenser pressure to be varied in line with variations in the ambient temperature leading to lower discharge pressures during periods of low ambient temperatures and lower compressor power consumption. Operation at lower pressures also increases the refrigeration capacity of the system enabling it to cope with increased load demands. LPA can be applied to new refrigeration plant and as a retrofit to existing plant. LPA also enables the use of liquid injection into the discharge line of the compressor which de-superheats the refrigerant vapour before entering the condenser. This increases the capacity of the condenser which in turn enables operation of the plant at lower condensing temperatures. This paper considers the application of a LPA and liquid injection to a cold store refrigeration system. The analysis has shown that more than 10% energy saving over and above the savings that can be achieved with floating head pressure, can be achieved by adopting the use of LPA in conjunction with liquid injection.