基于多极理论的U型地埋管轴向流动传热模型研究

STUDY ON AXIALFLOW HEAT TRANSFER MODEL OF U-TUBE GROUND HEAT EXCHANGERS BASED ON MULTIPOLE THEORY

以钻井壁为界将U型地埋管的传热区域分为钻井内外两部分,分别采用稳态与瞬态传热分析,两区域模型间通过钻井壁温度结合起来,以构成完整的埋管传热模型。钻井内部采用多极理论传热模型求解,对于钻井外部,采用恒热流柱热源模型来求解钻孔瞬时壁温。在考虑地埋管换热器中循环介质流动情况下,基于热阻网络平衡原理并建立地埋管传热模型,以实测的埋管进口温度与流速作为模型的输入量,用地埋管实测与计算的出口温度值为比较对象,验证多极理论U型地埋管轴向流动传热模型用于分析土壤源热泵系统的有效性。

The heat transfer region of vertical U-typed ground heat exchangers was divided into two zones, whose tempera- ture was coupled with the boundary of the borehole wall. Both steady and transient heat transfer methods were used to analyze the heat transmission inside and outside borehole, respectively. As for inside borehole, multipole theory model was used to solve the heat transfer problems. As for outside borehole, constant heat flux cylindrical source model was used to calculate the borehole wall temperature. On the basis of recirculated medium flow, the heat transfer model of GHEs was developed based on heat resistance network balance. The mnltipole theory model of ground heat exchangers considering the axial flowing of recirculated medium was verified to effectively analyze GSHP systems by taking experimental inlet temperature and flow velocity as input of the heat transfer model of GHEs and comparing the outlet temperature between experimental and calculated results.