Study on optimization and time effect of ground-source heat pump system in Nanjing

The reasonable design of hole spacing for buried heat exchangers is the first issue to be solved when developing shallow geothermal energy in the Nanjing erosion and accumulation plain area. In order to obtain the hole spacing for design reference and ensure ground-source heat pump system to operate long and stably, based on the ground-source heat pump test project at No. 102 Shimenkan, Qinhuai District of Nanjing, the hole spacing of ground heat exchanger and time effect of 10-year operation with ground-source heat pump system have been studied with the temperature monitoring system and numerical simulation method, and the hole spacing of ground heat exchanger and the operation mode have been obtained. The results show that : (1) during the complete operation cycle of summer, post summer recovery, winter and post winter recovery working conditions of ground-source heat pump system, formation temperature undergoes periodic change of heating, cooling, slow cooling and basic recovery. (2) The economical and reasonable hole spacing of ground heat exchanger is 4.0 meters suitable for the erosion accumulation plain of Nanjing. (3) In order to eliminate the heat accumulation during the summer working condition and promote the service life of ground-source heat pump system, the operation mode of equal cooling time in the summer and heating time in the winter is suggested, and the post summer recovery working condition is extended as much as possible. This study can provide scientific basis for the design of buried pipes and shallow geothermal energy engineering research in the Nanjing area.