印刷电路板式换热器焊接质量影响因素分析

Analysis on Influence Factors of Welding Qualityof Printed Circuit Heat Exchanger

印刷电路板式换热器的换热芯体是对层层堆叠的冷热换热板采用扩散焊在高温高压下焊合而成的。但是,换热板中换热流道的存在阻碍了焊接压力沿换热板的均匀传递,使得板间轴向应力分布不均,造成流道处焊合质量差、层板变形等缺陷。采用有限元法,考虑矩形截面流道的几何尺寸(流道宽度、肋宽、板厚)与焊接压力等因素,研究轴向应力在换热板焊合界面间的分布规律。结果表明:板间轴向应力绝对值在1个流道宽度范围内沿一侧向另一侧呈现先减小后增大的分布,流道中心区域为焊合薄弱区域。随着流道宽度的增大,板间中心区域的轴向压应力减小,不利于焊合;随着板片肋宽、焊接压力的增加,板间轴向压应力增大,但是流道两侧应力集中加剧,易产生焊接变形;适当增加流道板厚可以使流道界面轴向应力分布更均匀。

The heat transfer core of the printed circuit heat exchanger is made of stacked hot and cold heat exchange plates by diffusion welding at high temperature and high pressure.However,the existence of heat exchange runner hinders the uniform transmission of welding pressure along the heat exchange plate,resulting in uneven distribution of axial stress between the plates and poor welding quality at the runner,deformation of the laminate and other defects.Considering the flow geometry size(runner width,rib width,plate thickness)and welding pressure,the distribution law of the axial stress between the welded interface of heat exchange plates was studied by using the finite element method.The results show that the absolute value of the axial stress between the plates shows the distribution of first decreasing then increasing from one side to the other within one flow channel width.The central area of the channel is the weak welding area.The axial compressive stress between the plates decreases with the increase of the channel width,which is not conducive to welding.With the increase of plate rib width and welding pressure,the axial compressive stress between plates increases,but the stress concentration at both sides of the channel intensifies,which is easy to produce welding deformation.The axial stress distribution of the runner interface is more uniform by appropriately increasing the thickness of the runner plate.