基于经济性分析的中深层地埋管换热器优化研究

Study on optimization of mid-deep borehole heat exchanger based on economic analysis

地埋管换热器设计优劣和运行经济性是制约中深层地热能利用的关键。文章基于建立的中深层套管式地埋管换热器地下换热模型,提出了钻孔设计优化方法,以承担建筑热负荷400 kW中深层地埋管地源热泵系统为例,对比分析了不同钻孔方案对初投资成本及运行经济性的影响。结果表明:取热量相同的条件下,钻孔深而数量少的方案涉及地层温度高,埋管每延米换热量高,因此钻孔总长度较小,钻孔成本显著降低;循环水流量增大可提高埋管每延米换热量,但提高幅度不大,而运行费用会因热泵功耗增加而显著增加,因此换热器运行时不宜大幅增加流量。

The design quality and operation economy of borehole heat exchanger is the key of utilizing mid-deep geothermal energy.Based on the established underground heat transfer model of mid-deep borehole heat exchangers,the determining method is proposed to optimize the drilling depth.Take the case of a deep ground source heat pump which burdens a heating load of 400 kW,the initial cost and operation economy of different drilling schemes are compared.The results show that the deeper boreholes mean higher soil temperature involved and higher heat extraction capacity per linear meter of the buried pipe,which reduces the total boreholes length.Thus,the drilling cost can be significantly reduced.The study also shows that although increasing circulating water flow rate can increase the heat extraction capacity per linear meter of borehole to a certain extent,it is not suitable to increase the heat extraction capacity by greatly improving flow rate for this will greatly increase the operation cost by increasing pump power.