| Title | Thermal Performance Analysis of Coaxial Borehole Heat Exchangers Under Variable Design Parameters |
|---|---|
| Authors | N.Yildirim |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | |
| Abstract | Geothermal energy plays a vital role in the energy transition due to its low environmental impact and sustainable nature. In shallow geothermal applications, borehole heat exchangers (BHEs), which facilitate heat exchange with the ground, are among the most critical components that directly influence system efficiency. Properly designed BHE systems enhance the usability of low-temperature geothermal resources and contribute to the reduction of carbon emissions. BHEs are generally classified into U-tube, coaxial (concentric), and spiral (helical) types. While U-tube systems offer advantages in terms of low cost and ease of installation, coaxial systems provide higher heat transfer efficiency. Spiral designs are suitable for compact installations in limited spaces. This study investigates the energy capacity of coaxial borehole heat exchangers composed of two concentric pipes. Under conditions of 30 °C inlet fluid temperature and a constant bedrock temperature of 12.2 °C, various configurations with different pipe lengths, geometries, materials (aluminum and stainless steel), and flow rates (500, 1000, 1500, and 2000 L/h) were modeled using Engineering Equation Solver (EES) software. The thermal capacity of the borehole and the influence of design parameters were evaluated through numerical simulations. The results demonstrate how material selection, pipe geometry, and flow rate significantly affect the heat transfer performance. These findings provide valuable input for the optimization of borehole heat exchanger design in ground-source heat pump systems. |