Study On Energy Storage Characteristic In Confined Aquifer Of Double-well Groundwater Heat Pump

The groundwater heat pump is an efficient environmental air-conditioning system which can supply both heat and refrigeration. It uses aquifer to store energy, and transfers heat with water running underground. The aquifer chose to store energy is confined where the flowing is plain and slow. The confined aquifer is influenced by both heat transfer and groundwater flow during storing energy. The temperature field and head field will change a lot, which have an impact on pumping temperature and storage ratio, and then decrease the efficiency of heat pump system. So it is significant to describe exactly the change of temperature field, the influence factors of thermal breakthrough and storage ratio. Based on the double-well system, considering the groundwater dynamic model, thermodynamic model and Darcy rule, energy storage characteristic on confined aquifer of double-well groundwater heat pump is simulated by Flowheat which focuses on moisture and heat transfer in the porous media.Firstly, the aquifer thickness is considered as equal, the ground water fully saturates the porous medium within the region of ground-water flow, and described by Darcy’s Law. Based on that, comparing the single well with double well, the relationship of the thermal breakthrough time is discussed. It can be found that:(a) permeability produces little effect to the pumping temperature,(b) the smaller the porosity is, the less the pumping temperature changes,(c) the thicker the aquifer is, the less the pumping temperature changes,(d) the bigger the inter-well distance is, the less the pumping temperature changes,(e) the smaller the pumping flow is, the less the pumping temperature changes,(f) the smaller the temperature distance is, the less the pumping temperature changes,(g) when the load is constant, the big temperature difference with small water flow rate is better,(h) when the hydraulic gradient is perpendicular to the double wells, the bigger the hydraulic gradient is, the less the pumping temperature changes.Furthermore, the storage ratio is calculated and analy:zed and the factors which produce big effect to thermal breakthrough are discussed on the storage ratio. It can be found that:(a) the bigger the porosity is, the bigger the storage ratio is,(b) the bigger the inter-well distance is, the bigger the storage ratio is,(c) the thicker the aquifer is, the bigger the storage ratio is,(d) the smaller the temperature difference is, the bigger the storage ratio is,(e) the bigger the hydraulic gradient is, the smaller the storage ratio is. After that, the temperature field and the storage ratio of next five years in two different mode are calculated and compared.