Numerical investigations on thermal performance between the traditional full-filter well and improved semi-filter well in moderate climates

The operating efficiency of groundwater heat pump (GWHP) gets reduced because of thermal breakthrough. In order to explore an effective approach to minimize thermal breakthrough, an improved semi-filter well (SFW) that is different from the traditional full-filter well (FFW) has been proposed to achieve active control over the direction of groundwater advection. Based on the numerical simulation method, this paper has first analyzed the thermal flow differences between FFW and SFW in terms of heating/cooling load, flow rate and extraction-injection temperature difference. The results show that SFW can better govern the fluctuation in the pumping temperature and decrease thermal breakthrough, while as to FFW, thermal breakthrough tends to deteriorate and energy loss is about 195% higher compared with SFW. Subsequently, the simulation results of the allocation of the extraction-injection well types indicate that changing the extraction well type can enhance the influence on thermal flow. As long as the extraction well is SFW, thermal breakthrough and energy loss can be decreased. In addition, the simulation results were validated and the maximum relative error was less than 6%.