内螺纹铜管成形工艺开发及换热性能研究

Research on Forming Process Development and Heat Exchange Performance of Internal Threaded Copper Tube

随着我国碳达峰碳中和战略的推进,行业标准对空调产品能效的准入门槛越来越高。增大内螺纹铜管的螺旋角可以有效提高空调换热器的能效,但增大螺旋角则会大幅增加内螺纹铜管生产制造的难度。为研发内螺纹铜管成形工艺,提升换热性能,通过逆推法设计了Φ7mm(外径)×0.23 mm(壁厚)×0.14 mm(齿高)、齿顶角15°、螺旋角35°、 58齿数的内螺纹铜管(XD7)的两种旋压成形模具参数。以旋模比、拉拔速度、退火温度和保温时间作为变量,通过显微观察和力学性能测试,确定了XD7的旋压成形工艺和退火工艺。同时对比研究了XD7与同外径的普通内螺纹铜管D7(7 mm×0.24 mm×0.15 mm)的换热性能。结果表明:小的钢球半径更有利于XD7的成形,旋模比和拉拔速度分别为460和40 m/min时,XD7的成形效果最好。XD7的最佳退火工艺为在460℃下保温30 min。与D7相比,XD7的冷凝换热系数和蒸发换热系数分别提高了7%和8%,内螺纹铜管单管换热能效明显提升。

With the promotion of China's carbon peak and carbon neutrality strategy,the entry threshold of industry standards for energy efficiency of air conditioner products is becoming higher and higher.The energy efficiency of air conditioner heat exchangers can be effectively improved by increasing the helix angle of internal threaded copper tubes.In order to develop the forming process of internal threaded copper tube and improve the heat exchange performance,two kinds of spinning forming mold parameters of internal threaded copper tube(XD7)withΦ7 mm(outer diameter)×0.23 mm(wall thickness)×0.14 mm(tooth height),with 15°tooth apex angle,35°helix angle and 58 teeth are designed by reverse thrust method.Taking the spinning mold ratio,drawing speed,annealing temperature and insulation time as the variables,the spinning forming process and annealing process were determined by microscopic observation and mechanic performance testing.At the same time,the heat exchange performance of XD7 and ordinary internal threaded copper tube D7(7 mm×0.24 mm×0.15 mm)with the same diameter were compared.The results show that a small ball radius is more favorable to the forming of XD7,and the best forming effect of XD7 is achieved when the spinning die ratio and drawing speed are 460 and 40 m/min respectively.The optimal annealing process for XD7 is the thermal insulation at 460℃for 30 min.Compared with D7,the condensing heat exchange coefficient and evaporative heat transfer coefficient of XD7 have increased by 7%and 8%respectively.The energy efficiency of single tube of internal threaded copper tube has been significantly improved.