基于动态负荷的地埋管管群换热模型对比分析

Evaluating heat transfer models of ground heat exchangers with multi-boreholes based on dynamic loads

对比分析了地埋管换热器的无限长线热源、有限长线热源和渗流有限长线热源模型,指出轴向传热和地下水渗流作用对地埋管换热具有不可忽略的影响;基于温度场叠加原理和动态负荷建立了地埋管管群换热模型,借助于典型年动态年负荷模型,分析了管群长期动态换热特性。结果表明,无渗流型管群中心温度升高过快,长期运行应考虑土壤换热能力的衰减;对于渗流型管群换热,应采取合理优化策略避免下游土壤温升过快,并且设计埋管时应采用其进入稳定期的换热能力,避免长期运行时换热能力不足。对3种日负荷动态运行模式下管群的典型点温度变化进行了对比分析,结果表明,运行模式调节可以减缓土壤温度的上升趋势,特别是可减少渗流型管群的下游热量堆积,有利于土壤换热能力的恢复。

The comparison of the infinite line source model, finite line source model （FLS） and moving finite line source model （MFLS） ofborehole heat exchangers （BHEs） shows that the axial effects and groundwater flow have some effects on BHEs. Based on the temperature superposition principle and dynamic loads, the heat transfer models for multi-boreholes are established, combined with typical annual dynamic load model, the long-term multi-borehole heat transfer is analyzed with FLS and MFLS. The results show that the center tempera^tre of BHEs fields calculated with FLS increases fast and heat exchanger capacity attenuation should be taken into account for a long-term running. With MFLS, reasonable optimization strategy should be used to avoid fast increase of downstream soil temperature, and stable heat transfer ability should be adopted for design to prevent inadequate capacity of late runtime. The temperature rise at typical points in BHEs filed with three-day dynamic loads shows that the operation adjustment could significantly alleviate soil temperature rise and especially reduce the heat accumulation in downstream tubes, which is very good for recovery of soil heat exchanger capacity.