关键词: 微通道蒸发器, 分流板, 流量分配, 对流换热

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