Paper Title
Study a Comprehensive Optimization on Thermal Performance of U-Shaped Ground Heat Exchanger Using Finite Element Method

Abstract
This study describes an optimization on the thermal performance of U-shaped ground heat exchanger (GHE) at a base transceiver station (BTS) using finite element method. The thermal flow problem was solved in non-dimensional fashion under many effects of characteristic parameters such as Reynolds number (Re), Prandtl number (Pr), pipe width, pipe depth, and particularly the thermal conductivity (TC) of insulated plate. The numerical results indicated that the outlet temperature (Tout*) was shown to be nonlinearly proportional to Re and it can approach a minimal value at a given Re. In addition, the optimal design point at which Tout* is minimal, moves toward low Re when Pr increase. The Tout* decreases with increasing the pipe depth, however, its variation becomes smaller and flatter when the pipe width increases. Particularly, the Tout* decreases with decreasing the TC of insulated plate κI. The temperature reduction was up to 15% compared to the case without insulated plate used. This idea can be developed not only for U-shaped pipe but also for the other types of pipelines that were frequently used in practice. In addition, many good guidelines were provided for optimizing the thermal performance of a GHE and geothermal systems. Keywords - Computational Fluid Dynamics, Ground Heat Exchanger, Optimization.