Experimental Study Of A Direct Expansion Ground-source Heat Pump Air Conditioning System

The direct-expansion heat pump (DXHP) with the series of buried copper pipes is a specialstyle of ground-source heat pump (GSHP), which uses the refrigerant filling the pipes totransfer heating with the ground. The effect of heat transfer is considered higher with the hightemperature difference between the refrigerant and the ground, besides, the thermalconductivity of the copper is higher than PE. The coefficient of performance is believed higherbecause the lower power with lack of the water pump and water-fluid circle system.This paper set up a experimental platform to monitor and acquisition the data to get theseasonal performance factor (SPF) during winter and summer, the effect factor of the SPF andimprove way is considered through the parameter changes of the unit, such as the unit statepoint, the temperature of the refrigerant in the buried copper and the water-circle system. Thenfocus on the oil-return problem in the heating mode and the refrigerant-return problem in thecooling mode. Seting up oil-separator and oil-return bend to solve the oil-return problem ishelpful for the oil-return problem.The mathematical model of refrigeration charging is established by using void fractionmethod and the theoretical calculation is made. The calculate method of the refrigerationcharging in each components and pipes of the DXHP system is received. The chargeoptimization for the unit is also analyzed through series of experiment. which result are in goodagreement with the model.The result of experiment and mathematical model are worth to the next application of theDXHP..