【作者】 杨卫波； 施明恒；

【Author】 Yang Weibo Shi Mingheng (Department of Power Engineering, Southeast University, Nanjing 210096, China)

【机构】 东南大学动力工程系；

【摘要】 基于能量平衡法建立了垂直U型埋管的稳态传热模型,模型考虑了流体温度的沿程变化,并通过引入热干扰角与等效传热间距来反映两管脚间的热干扰问题,使之更复合实际的传热情况。通过所建模型对U型埋管的换热特性进行了数值模拟,结果表明:U型埋管的换热状况主要与土壤导热系数、回填物导热系数、管脚间距、管脚热干扰角、管内流体流量、进口流体温度及周围土壤温度有关,其中土壤导热性影响最为显著。增加土壤与回填物导热系数、管脚间距、管内流体流量及减小管脚热干扰角与进口流体温度(供热工况下)均可以增强埋管的换热效果。但回填物导热系数不可无限制增大,其大小还要考虑对增强管脚间热干扰的影响及其与管脚间距的相互关联性。同时,流量的增加要考虑对流动阻力增加的限制, 可以采用变流量设计来进行调节与优化。此外,为了充分发挥地源热泵的能效,其实际设计应该考虑埋管、热泵及负荷三者间的相互匹配性。更多还原

【Abstract】 Based on the energy conservation, a steady heat transfer model of vertical U-tube ground heat exchanger was developed , The model took the temperature variation of fluid along the depth into consider, and the thermal interference between the two adjacent legs was incorporated by introducing the idea of a thermal interact angle and equivalent distance so as to approach the actual heat transfer state more accurately. The numerical simulation on the heat exchanger characteristic of vertical U-tube buried coil was undertaken by use of the developed model, the results show that the heat transfer performance of U-tube is affected strongly by the conductivity of the soil and back grout, the distance between two legs, the thermal interact angle, the flow rate of fluid inside U-tube, the inlet fluid temperature of U-tube and the soil temperature in far field, and the influence of the conductivity of soil is predominate among these parameters. The increase of the conductivity of the soil and back grout, the distance between two legs, the flow rate and the decrease of the thermal interact angle and the soil temperature (in heating mode) can improve the heat transfer performance of U-tube. However, the increase of backfill conductivity should have a limit, the enhancement of thermal interference between the two adjacent legs resulting from the increase of conductivity of it and the mutual relationship between the distance of two legs and backfill conductivity should be considered in the determination of value of conductivity of backfill. At the same time, the increase of flow rate should be constrained by the resistance of flow, and the value of which could be optimized by variable flow design. Besides, the mutual match among buried coil, heat pump and heat load should also be considered to maximum the performance of GSHP.更多还原