Long term coupled simulation for ground source heat pump and underground heat exchangers

• The real-time interaction between heat pump and soil temperature was investigated.
• A long-term dynamic coupling model was built and validated by experiment data.
• Different scales of GSHP systems were simulated and compared.

A long-term dynamic coupling model based on variable heat line source model, one-dimensional heat transfer model and a steady-state heat pump model was built in this paper to simulate the performance of ground source heat pump (GSHP) system and soil temperature variation around the underground heat exchangers (UHEs). The model describes the real-time interaction between the performance of heat pump system and soil temperature variation in the long term. Simulation agreed well with the measured data. The soil temperature variation and heat pump system performance in 15 years in Changzhou was simulated. The results showed that the soil temperature will increase by 2.56–3.00 °C after 15 years, and cooling water inlet temperature will be 36 °C after 9 years, therefore the coefficient of performance (COP) of GSHP will decrease in summer, while increase in winter. It also prove that the temperature of the soil around borehole will rise with the operation of GSHP in the middle and downstream of Yangtze River, the more drilling hole amount the more obvious trend.