A revised thermal resistance and capacity model for the ground heat exchanger under freezing soil conditions and thermal performance analysis

When designing ground source heat pump systems in northern regions, we usually face the problem of soil freezing/melting around ground heat exchanger. The impact of freezing on heat transfer should be evaluated. An improved thermal resistance and capacity model based on the effective heat capacity method is developed in the paper to evaluate the effect. Further comparisons have been carried out against measured data from an experimental set-up, and agreement of the results validates the proposed model when the parameters of the model are set properly. The heat transfer capacity could rise by 30% because of phase change. The quantity of heat transfer could stay at 75 W/m to 80 W/m during three-month operation, which is feasible for a GSHP system to operate normally in such extreme condition.