Study on the ground temperature response induced by GSHP system operation under different geological conditions

Abstract

Ground temperature is a crucial factor influencing the performance of the ground source heat pump (GSHP) system. Different from the periodic variation of the initial shallow-layer ground temperature, the deep-layer ground temperature variation becomes much more complex after the system starts operating. At this stage, not only the ground surface heat exchange conditions and the geothermal gradient are influencing factors, but also the heat exchange process of the buried pipe and geological conditions will affect the ground temperature variation. In this study, ground temperature data of two systems located in different geological conditions are taken as examples. Based on the monitored data, the relationship between the ground temperature variation and depth is analyzed, as well as the impact from geological distributions. It has been found that the variation amplitude of the ground temperature varies along the depth direction. However, it is hard to find clear laws of the ground temperature variations from the measured data. Therefore, CFD (Computational Fluid Dynamics) simulation work is conducted to verify some guesses from the monitoring data analysis. It has been found that, except for the pipe bottom, the difference in ground temperature response mainly results from the change in ground thermal properties, not the heat transfer depth position of the buried pipes. This finding is beneficial to understanding the ground temperature variation mechanism in the GSHP system operation.