Study on the influence of pipe spacing on the annual performance of ground source heat pumps considering the factors of heat and moisture transfer, seepage and freezing

Considering heat and moisture transfer, seepage and freezing simultaneously, a three-dimensional dy-namic simulation platform of the ground source heat pump system (GSHPS) is established. Based on this platform, the annual performance of the GSHPS is analyzed. The results show that with the increase of pipe spacing, the soil moisture transfer radius, freezing time and freezing distance become smaller, and the unit performance becomes better. Compared with the pipe spacing of 3.5 m, when the pipe spacing is 4.5 m and 5.5 m, the moisture transfer radius decreases by 11.6% and 20.9% in summer and 6.7% and 15.6% in winter, the freezing time decreases by 25 days and 45 days, the maximum freezing distance decreases by 28.6% and 63.3% in unsaturated soil and 31.7% and 63.4% in saturated soil, and the unit average coefficient of performance (COP) increases by 0.7% and 1.9% in cooling period and 5.2% and 12.1% in heating period, respectively. The moisture transfer radius and freezing distance around the central borehole are the largest, and those around the boundary intersection borehole are the smallest. Compared with all other possible working conditions in heating period, the system performance is the best when considering heat and moisture transfer, seepage and freezing simultaneously. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

Increasing pipe spacing in a ground source heat pump system leads to better performance, with improvements in soil moisture transfer radius, freezing time, freezing distance, and coefficient of performance. The system performs best when considering heat and moisture transfer, seepage, and freezing simultaneously.