Experimental study of a liquid over-feeding mobile air conditioning system.

摘要

Air conditioning systems usually use only 85% of the evaporator coils. The other 15% or so is used to superheat the refrigerant so that the compressor will be protected from liquid slugging. This practice results in excessive evaporator volume. In mobile air conditioning (MAC) systems where the space available for the evaporator is limited, the evaporator should be used fully to reach maximum evaporator efficiency. This study reports on the design and testing of a novel liquid overfeeding (LOF) MAC system that can use 100% of the evaporator effectively. A LOF system is designed so that not all the liquid refrigerant is evaporated in the evaporator. The excess low-pressure liquid flows into an accumulator-heat exchanger where it is boiled off by the warm, high-pressure liquid leaving the condenser. This design not only allows 100% use of the evaporator, but also reduces the system power consumption (per unit mass flow) and improves compressor reliability. Test results for the LOF MAC, compared with thermal expansion valve and metering valve MAC systems, indicated an increase of 20% in system cooling capacity and coefficient of performance (COP) at a compressor speed of 2020 revolutions per minute (RPM). Because the LOF system is easy to implement, this design is expected to increase the cost of MAC systems only marginally.