This report contains a description of a mathematical model developed for the purpose of simulating the performance of direct expansion, ground-coupled heat pump systems. The simulation tool is a Fortran computer program that predicts the transient performance of a heat pump in which either the condenser or the evaporator is a ground-loop heat exchanger concentrator (GLHXC). The performance of the conventional indoor components of the system (i.e., compressor, condenser or evaporator, and expansion valve) is simulated with a heat pump program in which the outdoor component (condenser or evaporator) of the system is replaced by the ground-loop model in order to predict overall system performance in either the heating or cooling mode. Thermal analysis involves the transient conduction in the earth, heat transfer in the ground loop, and component performance. The steady-state program had to be modified to accommodate the transient behaviour. Numerical results from the simulation of a particular GLHXC system are compared with experimentally measured performance data in order to validate the model for both heating and cooling mode operations.

KEYWORDS: heat pumps, soil heat pumps, models, calculating, performance, computer programs, compressors, condensers, evaporators.