Cyclic simulation of a model describing heat transfer from a ground-coupled water source heat pump, considering transient effects on both soil and water sides

Abstract

A dynamic model has been developed to simulate transient response of a heat transfer loop coupling the heat rejection of the Freon side of a heat pump to the soil as a heat sink. The model simulates thermal storage effects in both the soil and the water side. The closed water loop side is also simulated using convective transport and conduction effects from the water to the soil. This paper presents how the model works, using a sample of real experimental data from an existing refrigeration system as the input or forcing function for the model. The simulation is repeated for 18 cycles using the same daily input on the condenser heat rejection side to observe when the effect of the initial conditions subsides and when the simulation reaches a cyclic steady state. The model shows the temperature distribution in the water along the length of the loop. It can also monitor the average soil temperature for the whole solution domain. With the advent of affordable computing power, the model should be useful for design purposes, after adequate testing. The model can be used in choosing the optimum length for a water loop according to the type of soil and heat transfer demand patterns imposed on that part of the heat pump which is coupled to the ground and some a priori design criteria.