Effect of natural cold source on groundwater source heat pump according to laboratory and field geotechnical thermal physical tests

• There are many laboratory tests and TRTs that are firstly carried on in Jiagedaqi.
• The distribution of cold sources are studied according to testing results.
• The distribution is in a scattered pattern and temperature range is 0–1 °C.
• The paper analyzes heat breakthrough and influence radius of cold source in the GWHP.

This paper uses the numerical method and laboratory and field tests to determine the effect of cold source on groundwater source heat pump (GWHP) in Jiagedaqi. Cold sources are distributed in a scattered pattern, with temperatures ranging from 0 °C to 1 °C according to temperature field test results. Laboratory tests show that the thermal physical parameters of pebbles and grit present discrete phenomenon with depth and that the parameters of sandstone and granite undergo minimal change. By considering the correlation and discrepancy of laboratory and field tests and by modifying the parameters of the laboratory test via the analytic hierarchy process, this paper selects formation thickness, moisture content, density, and permeability as the main factors that influence the difference in thermal physical parameters. Basing on the geological conditions of the region, this paper constructs a numerical model with the data from modified laboratory tests and in-situ thermal response tests. The model analyzes heat breakthrough and influence radius of cold source in the producing/injecting system of multiple wells. Simulation results show that the influence range of cold source on GWHP is 150 m and that heat breakthrough is observed when the influence radius is less than 85 m.