Simulation-based analysis of a novel geothermal pavement ice/snow melting system with reversible thermosyphons to eliminate soil thermal imbalance

Ice/snow removal from pavement is important for maintaining the functionality of transportation system in winter. Thermosyphons have been used to extract shallow geothermal energy for pavement ice/snow melting (PISM). However, heat extraction of thermosyphons from underground soil in winter leads to high soil thermal imbalance (STI). A novel geothermal PISM system with reversible thermosyphons (RT) is proposed to eliminate STI. The working fluid in a RT can circulate reversely by a micro-pump to collect heat from pavement and inject the heat into ground. To investigate its operating performance, a model for the simulation of underground heat exchange and soil temperature variation was developed and validated. Numerical simulations for annual operation of the investigated system were performed. The simulation results showed that the temperature of the region under 4.5 m underground at the end of recovery period was 1.9–2.9 °C lower than the undisturbed soil temperature at the same depth if no thermal storage occurred. The proposed system with thermal storage could make the average soil temperature of the computation domain increase by 1.66 °C, and the average soil temperatures at pipe outer surface and borehole wall all increase by 2.6 °C at the end of recovery period. After thermal storage, the temperature of most regions exceeded (in the central region) or approached the initial temperature. The simulation and analysis results indicated that the proposed system could effectively eliminate STI and avoid the degradation of heating performance.