Thermal Performance Evaluation of Various Inlet and Outlet Tube Materials in a Vertical Ground Heat Exchanger at Different Flow Rates

Geothermal energy is an effective and long‐term method of using earth natural heat in heating and cooling. In this paper, the thermal performance of a vertical double‐tube ground heat exchanger (GHE) is examined based on a two‐dimensional axisymmetric laminar flow CFD model on ANSYS Fluent. The study is an assessment of how the inlet–outlet tube material choice and flow rate affect the thermal performance of the cooling system in the context of the Bangladeshi ground conditions. Inlet and outlet tube combinations consisting of six materials are tested; they are silver, copper, stainless steel, galvanized iron, HDPE, and PVC. The simulations are performed at the flow rates of 1, 2, 4, and 6 L/min within 12 h of uninterrupted work. The heat transfer rate per unit borehole length of PVC using PVC as the outlet tube declines, respectively, in the sequence of inlet materials: silver, copper, galvanized iron, stainless steel, HDPE, and PVC. At 6 L/min; silver–PVC has the highest heat transfer rate per unit borehole length (44.57 W/m) with PVC‐HDPE having the lowest (29.45 W/m). The mean outlet temperature is 300.42 K (silver–PVC) to 304.31 K (PVC‐HDPE). PVC is the best outlet tube in terms of heat transfer than HDPE. The findings are that the heat transfer rate is proportional to flow rate, whereas the thermal resistance decreases and levels off at about 0.135 mK/W, and higher flow rates beyond 4 L/min do not add to the thermal performance but raise the energy consumption significantly. On balance, silver–PVC has the best thermal performance, and copper–PVC has the second best heat transfer rate per unit borehole length (44.54 W/m), an average outlet temperature of 303.87 K, and is a viable solution based on cost and mechanical strength.