地埋管换热器钻孔换热热阻与水力平衡综合分析

Comprehensive analysis for thermal resistance of ground heat exchanger and hydraulic balance

针对实际工程中地埋管换热器各并联埋管的水力不平衡情况,采用理论分析与设计软件模拟计算相结合的方式,分析了地埋管水力不平衡对地埋管钻孔内外换热热阻的影响。分析结果表明,当阻力不平衡率在±30%以内时,地埋管换热器钻孔内的传热热阻变化在±5%以内;长期运行的地埋管换热器钻孔内热阻在钻孔总热阻中所占比例很小,因此钻孔内热阻在±5%范围内变化对地埋管换热器总热阻的影响是可以忽略不计的;如果并联埋管环路阻力不平衡率在30%以内,建议采用异程连接,这样可以大大降低管材成本。

Some concerns have been raised on hydraulic imbalance of pipes in boreholes connected in parallel for geothermal heat pumps. The influenee of hydraulic imbalance of ground heat exchanger in boreholes on borehole thermal resistance is analyzed by means of a professional design ＆ simulation software. The results show that variation of the borehole thermal resistance is within ＋5% when the hydraulic imbalance rate varies in the range of ±30%. However, the borehole thermal resistance only contributes to less than ±5% of total thermal resistance of a ground heat exehanger. This indieates that influence of the hydraulic imbalance on the borehole thermal resistance can be neglected. Finally, the direct return system is suggested for the case of hydraulic imbalance within 30% , which can significantly reduce pipe cost compared to reverse return system.