制冷剂雾化喷嘴节流性能研究

Study on throttling performance of refrigerant atomizing nozzle

为提高制冷系统蒸发器内液态制冷剂的分配均匀度和换热性能,该文提出采用雾化喷嘴代替节流阀的雾化节流方案。采用计算流体动力学(CFD)方法对制冷剂的节流雾化特性进行模拟,分析了系统蒸发温度、冷凝温度、阀前过冷度等对制冷剂节流雾化特性的影响。结果表明,当蒸发温度、冷凝温度和过冷度的范围分别为5~15℃、45~55℃和0~8 K时,节流雾化喷嘴的出口流量在4.125~5.230 g/s之间波动,并受冷凝温度影响较大;雾化流场中约90%的两相流体处于3m/s以下的低速段时,雾化效果较好。冷凝温度升高、蒸发温度降低、过冷度减小均有利于雾化,但也造成雾化流场蒸发量不均,气流紊乱,使得湍动能边界产生剧烈波动,雾化不稳定。

In order to improve the distribution evenness and the heat transfer performance of the liquid refrigerant in the evaporator of the refrigeration system, an innovative scheme of an atomizing nozzle replacing the throttle valve is presented here. The throttling and atomization performance of the liquid refrigerant are simulated by the computational fluid dynamics （ CFD） method, and the influences of the evaporation temperature, the condensation temperature and the sub-cooling temperature on the atomization performance of the liquid refrigerant throttling are analyzed. The results show that,the flow rate of the nozzle outlet fluctuates in 4. 125 ~5. 230 g/s when the ranges of the evaporation temperature, the condensation temperature and the sub-cooling temperature are 5 ~ 15 °C , 45 ~ 55 °C and 0 ~ 8 K respectively, and it is more sensitive to the condensation temperature. When the velocity of about 90% two-phase flow in the atomized flow field is below 3 m/s, the atomization performance is better. Increasing the condensation temperature and decreasingthe evaporation temperature and the sub-cooling temperature are beneficial to atomization, but cause uneven evaporation and disorder airflow in the atomized flow fie ld and then result in the violent fluctuation of the turbulence kinetic energy boundary, thus leading to the instability of atomization.