Technical Assessment of Frozen Soil on Geothermal Heat Pump Technology in Western Canada

Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, Canada

Abstract

This study examines the thermal performance of a two-dimensional borehole system, featuring a U-shaped pipe embedded in porous soil, through the application of computational fluid dynamics. The investigation encompasses 24 cases, assessing the impact of various factors such as soil thermal conductivity (k = 1.5, 1.84, 2 W/mK), average soil temperature (T = 280-285 K), and soil moisture content (10%-55%) on ice formation and heat transfer enhancement. The k-ε turbulence model and Darcy-Forchheimer model are employed for the pipe and porous medium, respectively. Furthermore, a solidification model is utilized to monitor potential ice formation within the system. The findings reveal that an increase in soil thermal conductivity enhances heat transfer between the soil and pipe while simultaneously reducing ice formation. Additionally, higher soil moisture levels lead to an elevated outlet temperature for the pipe and decreased ice formation in the soil. Lastly, it is observed that ice formation becomes negligible when the temperature reaches 285 K.