The Design of Ground-Coupled Heat Pump Systems

Abstract

Ground-coupled heat pumps are being installed in increasing numbers due to proven performance and economy. The overall thermal resistance between the ground coupling fluid and a given type of surrounding soil is affected by pipe material, wall thickness, diameter and length, the spacing and depth of burial, and the resistance of the flowing fluid. An important variable affecting performance is the thermal conductivity of the soil in which the ground coupling device is buried. The optimum ground-coupled system considers initial investment and operating costs on a discounted basis. The large number of variables affecting both first cost and performance makes the optimum difficult to determine. This paper discusses design tradeoffs and significant factors which determine performance.