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The Control Study of the Redundant Refrigerant Charge Amount in Heationg Operating Condition of the

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Tutor: SuShunYu
School: Wuhan University of Science and Technology
Course: Environmental Engineering
Keywords: air-source heat-pump,redundant refrigerant charge amount,simulation calculation,
Type: Master's thesis
Year:  2013
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As the air-source heat-pump has the advantages of installation conveniently, simplicity andlow initial investments and can be used all year around,it has been widely used in the middle andlower reaches of the Yangtze River where there is no heating in winter in recent years. But thebiggest challenges of the ordinary air-source heat-pump are the low heating efficiency and thelong time defros due to the defrosting heat is not enough in the low temperature conditions inwinter. This study mainly focused on improving the efficiency of heating in winter of the air-source heat-pump and defrosting at the same time without affecting the normal heating circleand calculating the thermal efficiency.This paper takes R410A as refrigerant and makes numerical simulation of heat exchanger,according to the result of the calculation, the fluid flow and heat transfer characteristics of theheat exchangers are analyzed.On the basis of the research,this paper calculates the refrigerantcharge amount respectively between the refrigeration operating condition and heating operatingcondition, and the difference of the refrigerant charge amount in two different conditions is the0.4843kg.According to the difference,the control method of the redundant refrigerant chargeamount can be determined.The redundant refrigerant flux in winter was applied in three different heat-pump defrostingmodels including the hot gas bypass defrosting, the sensible heat defrosting and the heat outputfrom refrigerant subcooling. Calculating results show that three defrosting models all can beused to restrain frosting on the surface of outdoor heat-exchanger effectively in the heatingoperating air-source heat-pump air-conditioning system with refrigerant flux control. And amongthem, the heat output from refrigerant subcooling is the best defrosting method. When defrostingat predetermined time, defrosting time of the sensible heat defrosting is the least.The redundant refrigerant flux in winter applied in heat-pump defrosting models is not onlycan take advantage of the redundant refrigerant flux but also can make the air-source heat-pumpheat normally while inhibiting the formation of frost layer.When the air-source heat-pump runsunder frosting conditions in winter, redundant refrigerant flux in winter applying to thedefrosting models is a good measure,which can save energy and optimization air-source heat-pump¡¯s working performance.
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