Air Conditioning Hot Water One Compound Defrost Control Technology Research

This article described air conditioner with domestic hot water supply, using the basic working principle of heat pump, united the Air-conditioning and water heating equipment together, Only use a set of heat pump system's main components(compressor, heat exchanger, four-way valve etc), through effective control strategy, can set heating, refrigeration and produce hot water three functions in one equipment, Not only reduces the initial investment, but also increase the unit's energy efficiency is an energy efficient air conditioning and water heating equipment. However, in practice, also found that operation, the device is running at low temperature conditions, units of outdoor finned tube heat exchanger easy frost, with the frost layer thickened, will appear the phenomenon of evaporation temperature drop, system heat reduce and heating unstable and so on, In order to maintain stable operation, defrost is requirement. Thus, Seek a kind of effective defrost way and control strategy is urgent study.According to the shortages of some most common way to defrost, this paper puts forward a bypass defrost and reverse circulation defrost combination of composite defrosting method, and analyzes composite defrost theory and working process. established the finned tube exchanger frost model, by solving the model get the surface of heat exchanger frosting rule and frosted the major effect factor, Determine the representative environment temperature and fin temperature as the discriminant basis of starting defrost, and the optimal defrosting time was studied and analysis, formulated the defrost start and end control strategy. According to the way of composite defrosting control requirements and bypass defrost characteristics, using a self-correction function of the fuzzy control strategy, start the reverse cycle defrost when bypass defrost insatiable defrost requirements, adjust two defrost mode optimal switching period, realize the intelligent defrosting control. On the basis of the previous defrost control strategy, this paper through the soft, hardware realized composite defrost controller, then through the test to detect the control technology used in the actual product in the defrost effect. Experimental results show that compound defrost and defrost control technology can achieve the purpose of on-demand, defrosting effect is excellent, heating stability in defrost process, which can improve the effect of equipment in the low temperature conditions.