Transient Thermal-Resistance-Capacitance Model for U-Tube Ground Heat Exchanger

Abstract

In a GSHP system, one of the most important components is the ground-coupled heat exchanger through which the thermal energy is exchanged between heat carrier fluid (i.e., water or water-antifreeze fluid) and soil. Since the ground heat exchanger is responsible for a major part of the initial cost of GSHP system and the efficiency of this system depends on the performance of ground heat exchanger, a careful design of ground heat exchanger is crucial for a successful application of GSHP system. Although the simplified analytical model or 3D numerical model for single U-tube ground heat exchanger has been proposed in the past several decades, the transient thermal-resistance-capacitance model of ground heat exchanger has become more popular due to the high numerical precision and low computational demand. This chapter will discuss the above-mentioned transient thermal-resistance-capacitance model for the typical single U-tube ground heat exchanger, the corresponding thermal resistance network within a borehole, and how to determine the specific thermal resistances for different thermal resistance networks with a borehole.