Experimental and Theoretical Analysis of Subcooling Control in Residential Air Conditioning Systems
Air Conditioning, Electronic Expansion Valve, Optimization, Subcooling
Widespread use of electronic expansion valves in residential air conditioning systems has provided an opportunity to further improve performance by use of alternative refrigerant flow control strategies. This paper focuses on an experimental and theoretical investigation on the effect of subcooling control in air conditioning system. A 2 Ton (7 kW) R410-A system was used in the experimental study and a model for the same system was developed and validated. The paper provides a theoretical analysis and determination of a control scheme to maximize COP and an experimental validation on the performance of a RAC system with subcooling control against a TXV-based baseline system. The theoretical analysis showed that subcooling can be defined as a linear function of temperature difference of refrigerant condensation and condenser air (Δ����������������) and that the effect of the evaporator conditions on its COP-maximizing values are negligible. The system was evaluated at AHRI 240/270 dry conditions with a properly charged TXV (6600g) and EXV subcooling control (8500g) comparison. Results show an average 9.8% increase in COP and 10.4% in capacity using subcooling control for the SEER conditions and a resulting increase of 9.4% in SEER. Validation with both experimental and model data show that subcooling control based on Δ���������������� prov ides a co nt rol sche me with good agreement to the data for air conditioning system capable of increasing both COP and capacity.