Research On Heat Carrying Capacity Of Water In Lake-Water Source Heat Pump System

With the economic and technological development as well as energy and environmental issues have become increasingly prominent, the surface-water source heat pump (SWHP) draws more and more public attention. The Yangtze River district and the south of China abound with water resources, the surface-water source heat pump possess great significance. SWHP need appropriate water source, and there are heat load limit for one lake or reservoir. This paper focused on the research that the lake's or reservoir's highest heat capacity.The natural water temperature distribution characteristics of the lakes and reservoirs are studied in the paper: the temperature of the lake-water which the depth is greater than 4m is shown clear signs of thermal stratification in late spring, summer, early and mid autumn, but in the winter and early spring, the entire lake and reservoir water temperature distribution is uniform; the temperature of the lake-water which the depth is less than 3m is equally distributed during the whole year, and is non-thermal stratification, meanwhile, the water temperature is impacted by air meteorological parameters.In this paper, mathematical model of the natural water temperature distribution for the thermal stratification lakes and reservoirs is established, and utilized a large number of measured data to test the accuracy of the model and the reasonableness of parameters. On the basis of the natural water temperature model, the water temperature model when loading heat load is established by addition source item into equations, at the same time, the paper uses measured data of lake-water source heat pump air-conditioning system of People's Hospital in Kai County, Chongqing, to test the correctness of the water temperature model when loading heat load and the water flow model.By solving the water temperature model when loading heat load and the water flow model to calculate water's highest heat capacity. Takeing Chongqing in the areas cold in winter and hot in summer as an example calculated the lake-water's highest heat capacity with different temperature and different depth. Based on the data calculated, regressed the relationship between lake-water's highest heat capacity (w/m2) and lake's average depth (m) and lake-water's average temperature (℃). According to this, get the relationship between lake-water's highest air-conditioning cool load (w/m2), lake's average depth (m), lake-water's average temperature (℃) and the units'EER. With regards to drainage, there are two ways, one way is the drainage was drained to the layer which the temperature is as same as drainage's temperature, and the other way is the drainage was drained to the surface layer. In this paper, the water temperatures at bottom in these two ways was compared, and conclude that the first way is better than the second one. Suggest that the first way is a better approach in practical project.At last, studied the water temperature recovery, concluded that even if the water bears the highest heat load in summer, its temperature can recover to the level under natural conditions before the beginning of heating period.