科研之友
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摘要
Energy piles, as an environmentally friendly means to exploit renewable energy, have attracted the attention of global researchers over the past years. Traditional heat exchanger configurations (1-U-shape, 1-W-shape, and multi-U-shape in series or parallel) have been utilized. Traditional 1-U-shape is limited by pile length, short heat transfer path, and low total heat transfer rate. Traditional 1-W-shape heat exchange tubes will cause thermal interference. Moreover, the heat exchange rate per unit tube length is not high for multi-U-shape in series or parallel. Therefore, this paper presents an efficient pile foundation heat exchanger configuration, i.e., deep penetration 1-U-shape configuration. Through a numerical study, energy pile groups with deep penetration 1-U-shape heat exchangers are investigated under continuous operation mode and intermittent operation mode. The temperature change of the piles and soil under intermittent operation mode is analyzed. Thermal performances (e.g., outlet water temperature and heat transfer efficiency) are compared under the two operation modes. Four typical monitoring points under the two operation modes are compared, and the difference in temperature variation is obtained to study the influence on the temperature field of the piles and soil. Results show that in summer mode, the temperature of the pile under intermittent operation mode presents restorability while the temperature of the soil increases gradually. Intermittent operation mode yields a lower temperature of outlet water temperature than continuous operation mode does, and therefore intermittent operation mode is recommended.
