Preliminary Study of Tree-shaped Ground Heat Exchanger Based on Constructal Theory for GSHP Application

The horizontal ground heat exchanger (GHE) has several advantages over the vertical GHE, such as easy installation and not requiring specialized skills. Based on Constructal theory, this study uses a horizontal tree-shaped GHE with three branches for Ground Source Heat Pump (GSHP). Water was selected as the working fluid with flow rate configured at 1, 4, and 8 L/min. The bifurcation angles were 30°, 60°, and 120°. The impact of varying flow rates and bifurcation angles on heat transfer rate and pressure drop was examined. COP improvement factor evaluates energy savings because of increased heat transfer rate and energy loss because of pressure drop on GHE. The smooth straight pipe was selected as a benchmarking performance of Tree-shaped GHE. Results show that the pressure drop and heat transfer in horizontal tree-shaped GHE at the flowrate of 8 L/min is 128-263% and 171-175%, respectively, greater than that of a smooth straight pipe. Based on the COP improvement factor, the horizontal tree-shaped GHE at the flowrate of 8 L/min improves the COP improvement factor of GSHPs by 1.71 – 1.75. The findings indicate that the horizontal tree-shaped GHE outperforms the smooth straight pipe GHE. Based on these findings, the tree-shaped GHE is recommended for applications in horizontal GHE. Nonetheless, additional research is required to comprehend how ground thermal conductivity affects the effectiveness of the horizontal tree-shaped GHE.