MODEL TESTS ON THERMAL MECHANICAL BEHAVIOR OF ENERGY PILES INFLUENCED WITH HEAT EXCHANGERS TYPES

Pile geothermal heat pump system (also called energy pile) is a new heat pump system that can save underground space and construction cost, which to date has been used at home and abroad. However, the studies focusing on the heat transfer efficiency and mechanical characteristics of piles in dry sand are still limited. Based on the model test, the heat transfer performance and mechanical characteristics of different heat exchange concrete piles in dry sand are investigated. The temperature of pile and soil around pile, the thermal strain and thermal stress of the piles induced by temperature variation are measured. Moreover, the ultimate bearing capacity of the piles associated with different temperatures is analyzed. The results show that, for different types of heat exchangers under the same power of pump, the strain variation and pile head settlement of the W-shaped and S-shaped piles are more significant than that of the single U-shaped pile.