摘要
基于元体能量平衡法建立了垂直U型埋管的传热模型,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反映两管脚间的热干扰问题,使之更符合实际的传热情况。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: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,其中土壤导热性影响最为显著。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,实际设计应该考虑埋管、热泵及负荷三者间的相互匹配性。
Based on a method of element energy balance,established was a heat exchange model for vertical U-shaped embedded tubes.The model has taken account of the liquid temperature change along their flow path.The thermal interference problem between two tube feet has been reflected through the introduction of a thermal interference angle and an equivalent heat-transfer spacing,making the model more in compliance with the actual heat transfer conditions.Based on the model,a numerical simulation was conducted of the heat exchange characteristics of the U-shaped embedded tubes.The simulation results show that an increase in the heat conduction coefficient of soil and backfill substance,spacing between the tube feet and in-tube fluid flow rate and a decrease in the thermal interference angle of the tube feet and inlet fluid temperature under heat supply conditions can all lead to a better heat exchange effectiveness of the embedded tubes.Among the above factors,the heat conduction coefficient of the soil exercises a most conspicuous influence but that of the backfill substance shall not be increased unrestrictedly.Its magnitude has to take into account the influence of the increased thermal interference between the tube feet and its correlation with the tube feet spacing.In the meantime,concerning an increase in the flow rate,a restriction in flow resistance increase must be taken into consideration.A variable flow rate design method can be used for relevant adjustment and optimization.In addition,to give full play to the efficacy of geothermal source heat pumps(GSHP),one should during actual design pay attention to mutual matching of the characteristics of three factors: i.e.embedded tubes,heat pumps and loads.
出处
《热能动力工程》
EI
CAS
CSCD
北大核心
2007年第1期96-100,共5页
Journal of Engineering for Thermal Energy and Power
基金
国家自然科学基金资助项目(50276013)
关键词
垂直U型埋管
元体能量平衡
换热特性
地源热泵
数值模拟
vertical U-shaped embedded tube,element energy balance,heat exchange characteristics,geothermal source heat pump(GSHP),numerical simulation
