Effect of Underground Convective Flows on the Performance of Ground Source Heat Pump Systems

Abstract

Ground Source Heat Pump Systems (GSHPS) are becoming more and more commonplace everywhere in the world. There are many factors influencing the performance of GSHPS systems such as the distance between the boreholes, number of boreholes, the number of tubes circulated in a borehole and etc. Mathematical models that are used in modeling the performance of GSHPS systems are well established. These models usually account for the conductive heat transfer into the strata and the convective heat transfer within the tubes the fluids flow. One of the parameters that could affect the performance of the GSHPS is the presence of underground convective flows. This can also have a very significant effect on the GSHPS performance. In this study we have developed a numerical model for the purpose of studying the effects of underground water flow on the performance of GSHPS. The model is based on solving the energy balance equation only. Hence we assume steady state flow of fluid in the underground and in the tubes. Results show that the presence of underground convective flows can considerably change the distribution of temperature caused by the fluid flowing in the borehole tubes. Furthermore we also carry out a sensitivity study regarding the types of tube configurations used in a borehole.