Experimental study on improving the performance of dry evaporator with rectifying nozzle type critical distributor

In order to ensure uniform distribution of dry evaporator under various operating conditions, two novel distributors based on the distribution concept of ``flow pattern setting & critical distribution'' are proposed. The theoretical analysis and structure design of rectifying nozzle type critical distributor (RD) based on the distribution principle of ``swirling setting & critical distribution'' are carried out. And the mechanism of swirling setting and critical flow of gas-liquid two-phase refrigerant is expounded. The flow pattern setting is to adjust the up-flow non-uniform and asymmetrical flow pattern to ideal annular flow by rectifying elements, to overcome the influence of up-flow flow state on distribution characteristics. The critical distribution is to make the two-phase flow reach the local sound velocity by sonic nozzle, to overcome the influence of the non-uniform heat transfer of each branch of the downflow on distribution characteristics, and solve the influence of inconsistent resistance of each breach, pressure wave oscillation and other unfavorable factors on the heat transfer performance of the dry evaporator. Based on the results of theoretical analysis, the RD is designed, and tested on the performance test system of dry evaporator. The experimental research results show that the distribution effect of RD is the best. The cooling capacity of the dry evaporator with the RD is increased by 22.7% or more, compared with Venturi distributor. The results show that the use of RD restrain the problem of gas-liquid two phase refrigerant mal-distribution in dry evaporator.