Analysis of the thermal performance reduction of a groundwater source heat pump (GWHP) system

This paper investigates the thermal performance reduction of a groundwater heat pump (GWHP) system installed in Hubei province, China by the monitoring of the system operation over a two-year period. Pipe corrosion and deposits were detected in the maintenance of heat pumps, which might contribute to the thermal performance reduction. In order to understand the physic-chemical dynamics inside heat pumps during the system operation, the groundwater pumped out from the aquifers and the deposits collected in a condenser of a heat pump were analyzed. The groundwater has electrical conductivity of 973 μS/cm, indicating low salinity. The X-ray fluorescence (XRF) analysis shows the deposits were composed mainly of 66.4% Fe2O3 and 17.8% CaCO3, indicating both effects of iron oxidation and groundwater fouling. The corrosion effects on the heat transfer efficiency of metal pipes were examined. The heat transfer coefficient (HTC) comparison of a raw pipe and three rusted pipes show that the HTC of the rusted pipes was reduced by 8.3–41.5%, meaning a significant decrease in heat transfer efficiency. It is verified that the thermal reduction of the GWHP system could be attributed to the pipe corrosion which desires to be carefully considered in system design and operation in future. © 2021 Elsevier Ltd