Study On Comprehensive Performance and Energy Saving Effect of Cement Based Grouting Materials For Gshp Systems

The grouting material is a heat transfer medium between the borehole heat exchanger and geotechnical soil. The values of fluidity, thermal conductivity, compressive strength and adsorption properties of cement-based grouting materials with the highest allowed ratio of bentonite were obtained through experiments. And the results show an optimal performance of the material with water-cement ratio of 0.75 and sand-cement ratio of 2. The thermal conductivity value of the optimized grouting material can reach 2.62 W/m K, and its saturated adsorption capacity for pollutants is 12.85 mg/g. By applying the parameters of grouting materials to a real ground source heat pump project, the simulation results prove that the optimal grouting materials can effectively reduce the thermal resistance of borehole, and consequently reduce the total drilling depth of borehole and increase the heat transfer efficiency by 7.8%, which is of great significance to reduce the initial investment and the operating energy consumption of ground source heat pump systems.