Heat and mass transfer model of a ground heat exchanger: Theoretical development

A new approach to the simulation of a horizontal type Ground Heat Exchanger is proposed resulting in a better accuracy and at the same time a reduced computational effort. These results come from the concentration of the comp utational effort at the locations with the largest temperature and moisture gradients, i.e. the pipe-soil interface. The model takes into account heat and moisture transfer in the soil allowing for more accurate predictions o f the soil thermal response to the heat fluxes induced by the GHE operation . This in turn allows for a more accurate prediction of the soil temperatur e held and the circulating fluid temperature profile. A comparison of the r esults obtained by using the implicit and explicit methods of solving the s et of governing equations is discussed. The implicit method requires partia l linearization of the heat and mass transfer equations but results in a co nsiderably shorter simulation time. The explicit formulation allows for the solution of the fully nonlinear set of heat and mass transfer equations at the expense of increased simulation time. The following analysis shows tha t the difference between the solutions obtained using these two methods is minimal, thus favouring the implicit formulation. Copyright (C) 1999 John W iley & Sons, Ltd.