Three-dimensional numerical model for heat balance simulation of ground-water heat pump

Abstract: In order to simulate and predict the change law of heat balance accurately and avoid heat penetration phenomenon during the groundwater heat pump operation, a three dimensional coupling numerical model of groundwater seepage and thermal transport was established and applied to the demonstration project of groundwater heat pump system in Zhengding, Hebei province. The model was based on the groundwater seepage theory, saturated water-bearing medium thermal transport theory and Terzaghi effective stress principle, combined with the design scheme and operation situation of groundwater heat pump, the future heat balance development tendency of groundwater heat pump system under three different conditions was forecasted and analyzed. The water temperature difference between the pumping well and recharge well reduced by 20% (eight degree centigrade) or increased by 20% (twelve degree centigrade) was the first condition which means the cooling and heating load was kept constant. Second condition was the water temperature difference between pumping well and recharge well confirmed and the circulating water volume increased by 20%, or the volume of circulating water kept constant and water temperature difference between pumping well and recharge well increased 20%, which means the cooling and heating load was increased. Meanwhile, in the third condition, the cooling and heating load was reduced. The water temperature difference between the pumping well and recharge well was confirmed and the volume of circulating water reduced 20%, or the water temperature difference between pumping well and recharge well reduced 20% while the circulating water volume kept constant. It was shown that there is a heat penetration phenomenon between the pumping well and recharge well in the demonstration project under the condition of design scheme, which has one pumping well and one recharge well. When the cooling and heating load of the groundwater heat pump system is confirmed, increasing 20% of the water temperature difference between the pumping well and recharge well is more conducive to remiting the heat penetration between the pumping well and recharge well than reducing 20% of the water temperature difference between pumping well and recharge well. In addition, when the cooling and heating load of the groundwater heat pump system is increased, increasing 20% of the water temperature difference between the pumping well and recharge well is a more efficient method for remiting the heat penetration between pumping well and recharge well than reducing 20% of the circulating water volume. Meanwhile, when the cooling and heating load of the groundwater heat pump system is reduced, reducing 20% of the circulating water volume is more conducive to remiting the heat penetration between pumping well and recharge well than reducing 20% of water temperature difference between the pumping well and recharge well. This research indicates in the groundwater heat pumping system, reducing circulating water volume and increasing water temperature difference between pumping well and recharge well can remit heat penetration phenomenon effectively.