镀锌钢管套管式地埋管换热器换热影响因素研究

Influencing Factors of the Galvanized Steel Coaxial Ground Heat Exchanger

以武汉地区为例,使用TRNSYS软件中PID控制器使镀锌钢管套管式地埋管换热器系统在运行过程中进出水平均温度维持在冬季7.5℃、夏季32.5℃的设定温度,模拟研究钻孔深度、钻孔间距及内管流体流速对套管式埋管换热器换热量的影响。得到钻孔深度从80 m变化至120 m时,换热器的冬季延米平均换热量变化较小;夏季延米平均换热量呈上升趋势,最高可上升6.6%。当钻孔间距从3 m增加至6 m,冬、夏季平均延米换热量分别升高2.5%和1.6%。管内流速从0.03 m/s变化至0.7 m/s时,换热量逐渐上升并趋于平缓。将镀锌钢管套管式换热器与两种常规埋管换热器(单U-PE管和双U-PE管)对比,得到镀锌钢管套管式换热器换热效果最好,其冬季延米平均换热量分别高出常规换热器32.6%和28.5%;夏季延米平均换热量高出常规换热器29.6%和25.7%。

Taking Wuhan area as a case, the PID controller in TRNSYS software is applied to maintain the average temperature of the inlet and outlet water of the galvanized steel coaxial ground heat exchanger(GSCGHX) at the set temperature of 7.5 ℃ in winter and 32.5 ℃ in summer during the simulation. The influence of drilling depth, drilling spacing and velocity of inner tube flow on the heat transfer of the GSCGHX are investigated. It is concluded that, with the increasing of the drilling depth from 80 m to 120 m, the average heat transfer of GSCGHX changes slightly in winter. The average heat transfer shows an upward trend in summer and it can rise up to 6.6%. When the borehole spacing changes from 3 m to 6 m, the average heat transfer of the GSCGHX in winter and summer will increase by 2.5% and 1.6%, respectively. The heat transfer increases gradually and tends to be gentle with the flow velocity changing from 0.03 m/s to 0.7 m/s. Two conventional ground heat exchangers(single U-PE pipe and double U-PE pipe) are chosen as the references for comparison. The GSCGHX has the highest heat transfer rate for the average heat transfer of the GSCGHX are 32.6% and 28.5% in winter, 29.6% and 25.7% in summer higher than the references, respectively.