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Design and simulation tool for ground source heat pump systems considering groundwater advection

Shoji, Yutaka
Katsura, Takao
Higashitani, Takashi
Nagano, Katsunori
Sakata, Yoshitaka

Calculation of the underground temperature resulting from heat injection/extraction into/from ground heat exchangers (GHEXs) with hourly variation is one of the most noteworthy challenges to address when simulating and designing a ground source heat pump (GSHP) system. Especially in Japan, considering the groundwater flow is desirable because there is the possibility to reduce the installation cost for GSHP system. In order to overcome this challenge, the authors introduce a method to calculate the underground temperature, by considering heat injection/extraction into/from GHEXs with hourly variation. The method applies the superposition of the Moving Infinite Cylindrical Source (MICS) solution and the Moving Infinite Line Source (MILS) solution to calculate the temperature change due to heat injection/extraction into/from the certain GHEX and other neighboring GHEXs, respectively. In this paper, the outlines of the MICS and the method that calculate the MICS solution were firstly introduced. Next, the calculation method of underground temperature and the simulation model for the GSHP system were explained. Finally, the temperature variations of the heat carrier fluid were calculated by changing the conditions the geological layer and groundwater velocity.