Parametric Study of the Ground-Air Heat Exchanger (GAHE): Effect of Burial Depth and Insulation Length

Abstract

A parametric study of a ground-to-air heat exchanger (GAHE) using numerical models based on computational fluid dynamics with the finite volume method to evaluate the thermal potential of GAHE is presented. After the validation of the numerical code developed with published experimental data, it is proceeded to the study of the geometric parameters to define those that have the greatest impact on the application potential of GAHE. Climatological variables such as relative humidity, air flow velocity, and inlet air temperature are analyzed, as well as the increase in the thermal conductivity of the soil due to its humidity content. In addition, a study of the optimal installation depth as well as the length of the thermal insulation in the outlet pipe of the GAHE is presented. The results reveal that there is a higher heat exchange potential in the GAHE for an optimal burial depth of 4 m and a length of pipe of 15 m, 30% soil moisture content for heating and 32% for cooling, and a pipe diameter of 0.15 m. The use of thermal insulating is recommended only for the last 2 m of length in the outlet pipe of the GAHE.