板翅式换热器是空气分离系统中实现冷凝、液化、蒸发等热量交换的关键装备，具有小温差不稳定传热、二次传热、允许阻力小、多股流物性变化激烈的显著特点。已有设计方法难以解决大型化引起的通道负荷不均、通道偏流失匀、工质流阻增加、换热效率下降问题。为此，提出了一种大型空分板翅换热器性能强化的逐流段设计方法。根据空分工艺流程，按多股流质量流速确定其流道数，沿外侧隔板正向逐通道选择可排流体，通过标准正态分布概率随机预设定初始排列，对反向有限个通道重排实现排列回溯，以累积换热负荷峰值、方差和范数为综合判据，在全通道可行排列集合中，确定多股流通道最优排列，满足了换热器大型化对通道多股流换热高均匀性的要求。在纵向传热与横向传热方向建立热平衡方程组，实现换热器多股流间单叠与复叠传热的逐流段设计，提高了长流道换热器参数的设计精度。进行换热器芯体传热与流阻性能的物理试验，比较不同翅片、不同排列的换热器芯体性能，对冷热流间相互传热的逐流段校核设计方法进行验证。所提出的方法已应用于八万等级大型化空分换热器研制。

Plate fin heat exchanger (PFHE) is key equipment where condensation, liquefaction, evaporation and other heat exchanges occur in air separation unit (ASU). The distinctive characteristics of PFHE are small temperature difference unstable heat transfer; secondary heat transfer; low allowance resistance; fierce physical properties changing of multi-streams. The existing design methods face the problems such as unbalanced heat load of passage; maldistributed passage flow; increased flow resistance; decreased thermal efficiency. Therefore, a segmented design method of performance enhancement for large PFHE of cryogenic ASU is proposed. Passage amount of each fluid is preset according to the mass flow rate of multi-streams on the basis of ASU process. The feasible fluid is originally prearranged with standard normal distribution probability passage-by-passage forward from external cover plate. Arrangement backtracking is realized by rearranging finite passages backward. The optimal passage arrangement of PFHE is determined from all possible passage arrangement according to synthesis criteria of peak, variance and norm of accumulative heat load. Heat balance equation set is built in longitudinal and horizontal direction. Segmented design of PFHE is realized considering heat transfer among multi-streams of single-cold-stream and dual-cold-stream to improve design accuracy of long passage heat exchanger parameters. The PFHE experiment of heat transfer and flow resistance is accomplished. The PFHE cores with different fins and flow configurations are compared to verify the segmented design method of PFHE. The proposed method is applied to the development of corollary PFHE of 8×104 N•m3O2/h ASU.