A new design of ground heat exchanger with insulation plate for effectively geothermal management

Abstract

This paper proposes a new design of the ground heat exchanger (GHE) with the insulation plate based on the numerical approach. The heat transfer problem is solved in non-dimensional fashion under the important effects of many characteristic parameters, such as Reynolds number (Re), Prandtl number (Pr), pipe width, pipe depth, particularly the thermal conductivity (TC) and the dimensions of insulation plate. The numerical model has a good validation due to its excellent agreement with the results obtained in the literature. It was found that the temperature at the outlet (Tout*) is non–linearly proportional to Re and approaches a minimum value for a particular Re. Furthermore, the optimal design point where Tout* is minimal moves toward the low Re when Pr increases. The Tout* also decreases with increasing the pipe depth, however, its variation becomes smaller and flatter when the pipe width increases simultaneously. Additionally, the thermal performance increases significantly with decreasing the TC of insulation plate. The Tout* is up to 15 % lower than that without an insulation plate. In particular, the new design of the GHE prototypes with the insulation plate is first proposed. This idea can be developed not only for the U–shaped pipe, but also for the other GHE prototypes that are frequently used in practice, for example, the double U–tube, the W–shaped tube, and the spiral tube. The results obtained are very useful to effectively improve the thermal performance of the GHEs applied in the geothermal management.