地源热泵地埋管换热器换热性能试验研究

Experimental study on heat transfer performance of ground source heat pump buried tube heat exchanger

影响地源热泵系统效果的关键因素是室外地埋管换热器的设置情况,影响地埋管换热器换热性能的主要因素是岩土的综合导热系数、综合比热容以及钻孔的总热阻等热物性参数。各工程所在地地质条件差异很大,如何得到地埋管换热器换热性能参数是地源热泵系统设计必须解决的问题。本文基于线热源模型得出换热器内流体平均温度与时间的对数关系曲线,通过测试地埋管换热器进出口水温,进而推算出岩土的综合导热系数及热阻,大大简化了计算过程。此外,通过对地埋管测试井长期连续监测发现,在寒冷或严寒地区对于冬夏季冷热负荷不平衡的系统,室外地埋管换热区岩土温度呈下降趋势,设计时应考虑解决措施。

T he key of the ground source heat pump system is the design of the ground heat exchanger. Some soil thermal properties including soil heat conductivity,specific heat capacity and entire thermal resistance of the well drilling affect heat transfer characteristics of ground heat exchanger significantly. However,geological conditions are different in different area,resulting in the difficulty in acquiring ground heat exchanger heat transfer capacity in every project designing. In this paper,the log curve of the relationship between average temperature and time was obtained based on the line heat resource theory. According to the test of the inlet and outlet water temperature,the soil heat conductivity and thermal resistance were calculated,leading to a simpler calculation. Additionally,it was revealed that when summer cooling load and winter heating load was unbalanced in cold area,the temperature dropped in buried pipes outdoors,requiring solutions at the design stage.