## 2 In Situ Thermal Response Test  
Several techniques can be employed to predict the thermal conductivity of a GHEX design. The easiest approach is to use the standard value of the rock where the GHEX is located. However, this method may require expensive samples and may not provide a full profile of the field. [PERSON] [8] presented a thermal response test (TRT) for estimating the ground value of underground thermal conductivity and the thermal resistance of a borehole system. The general method of TRT adopts a system in which the heat medium fluid circulates through the Hall system at a constant heat injection rate, as shown in Figure 2. The thermal response is then recorded continuously. After data acquisition, the temperature data are compared with mathematical models such as the source model [44; 45; 46; 47; 48]) or cylindrical source model [44; 45; 46; 49; 50]. Figure 1: Schematic diagram of ground-source heat pump geothermal heat exchange systems: (**a**) installed examples; (**b**) classification of geothermal heat exchanger system. Figure 3 consists of the trailer-type transport system used in this study [52; 53; 54; 55; 56]. In addition, a schematic diagram of the experimental set-up of the SCW system showing the thermal response of the test equipment shown in Figure 4 is shown. In the test set-up (Agilent 34970A), a measurement program (LabView) and a flow meter were used to measure temperature and flow. Control circuits and temperature sensors were installed on each pipe at the inlet/outlet, including boilers and filters. Each device used an instrument that was calibrated at the factory or regularly. The boiler capacity provided 84 kW (42 kW \(\times\) 2 units) of oil condensation. The flow rate of the circulating fluid was measured using a flow meter (Macnaught). In addition, a return pipe flow meter (water meter) was installed and the bleeding rate was controlled to measure the bleeding rate of the measuring device without introducing water into the SCW system. Table 1 shows the components installed in the experimental and measurement devices used in this study. Figure 3: Experimental apparatus of a standing column well (SCW) system. Figure 2: Thermal response test apparatus [51]. Figure 5 shows the behavior of the closed borehole and single/two-well SCW systems according to the exponential and exponential used in this study, as well as the position of the return pipe. The groundwater heat exchanger under test is of type SCW, eight inches in diameter and 350 m and 400 m deep. It has a PVC inner casing and a top extraction/bottom circulation structure. During the drilling process, water intake was observed to increase significantly at depths of 80-100 m and 270-290 m. The maximum quantity analyzed was found to be in the range of 600-800 tons/day based on the groundwater impact survey results, and the stable withdrawal capacity was found to be in the range of 200-250 tons/day. Table 2 shows the bleeding percentage used in this study. The bleeding rates of 10% and 25% have absorption capacities of 80 tons/day and 200 tons/day (0.06 m\({}^{3}\)/min and 0.13 m\({}^{3}\)/min), respectively. In this study, the characteristics of single-well and two-well underground heat exchangers were compared. We also evaluate the thermal performance of a two-well system and a single-well system underground heat exchanger when there is no discharge rate and when returning from the inlet and re-injecting the discharge into the wells [40; 41; 42].