Heat and mass transfer analysis in unsaturated ground soils around the buried heating pipe

Abstract

A new approach to the simulation of a horizontal type ground heat exchanger is proposed to result in a better accuracy and at the same time a reduced computational effort. These results come from the concentration of the computational effort at the locations with the largest temperature and moisture gradients, i.e. the pipe-soil interface. Thus, the model takes into account coupled heat and moisture transfer in the unsaturated soil, allowing for more accurate predictions of the soil thermal response to the heat fluxes induced by the operation of the ground heat exchanger. This in turn allows for a more accurate prediction of the soil temperature field and the circulating fluid temperature profile. And also, the performance of a single pipe carrying warm fluid buried in a medium wet sand is described in this paper. The new coupled differential equations have been solved using the finite element method as a spatial discretization technique coupled with a finite difference relationship to describe the transient behavior by a numerical code. The time varying soil moisture concentrations and temperatures are graphically presented. As a result, it can be achieved that the soil moisture profiles develop at a slower rate than the temperature distribution functions.