Abstract: Three different micro-channel evaporators with parallel flow were designed with the only difference in the structure of the first deflector,with the same open area but different number and location of holes. The performance of three evaporators was tested with refrigerant 134a under the same conditions.  Flow and heat transfer characteristics in the evaporators were investigated with different number and location of holes in deflectors. The results show that the structure of deflector affects the flow and heat transfer performance of the evaporator remarkably. An appropriate structure of deflector can improve the uniformity of flow distribution, cooling capacity and pressure drop. The increase in pressure drop is faster than that of cooling capacity. With the same open area of holes in the deflector, their number and location in deflectors have no effect on the resistance coefficient of the evaporator. Insufficient holes in deflectors may generate the mal-distribution of refrigerant and deteriorate the heat transfer performance of the evaporator. When the holes in the deflector are not in the middle of two neighboring flat tubes,flow of the refrigerant is limited and the uniformity of flow distribution gets worse. The optimal structure of the first deflector is that the number of holes is half of that of the flat tubes,and the projection location of each hole has the same distance from two adjacent flat tubes.

Key words: micro-channel evaporator, deflector, flow distribution, convective heat transfer

摘要： 试验研究了仅改变微通道平行流蒸发器内第一个分流板上的开孔数量和位置时，蒸发器的流动和换热性能的变化规律。结果表明：分流板的开孔数量和位置对蒸发器的流动和换热性能影响很大。合理布置分流板的结构，可以改善蒸发器内的流量分配，从而提高蒸发器的制冷能力，同时压降也会上升，且上升幅度大于制冷量的增加幅度。分流板上的总开孔面积一定时，开孔数量和位置的变化对蒸发器的内部阻力系数没有影响。分流板上的开孔数量太少及开孔位置偏离中心都不利于流量的均匀分配。分流相对均匀的第一个分流板的结构是：开孔数量是扁管数量的一半，开孔位置与相邻两扁管的投影等距。

关键词: 微通道蒸发器, 分流板, 流量分配, 对流换热