跨临界CO_2节流短管流量特性实验研究

Experimental Study of the Trans-critical Carbon-Dioxide Two-Phase Flow Through Short Tubes

以节流短管为对象,实验研究了流量和节流短管上游压力、下游压力、入口温度以及几何结构的关系,得到了CO2通过节流短管的半经验流量关系式.研究结果表明,跨临界CO2节流短管流动与制冷剂R134a显著不同,通过短管的制冷剂流量和直径呈指数关系,CO2的指数(2.73)大于常规制冷剂(R134a为2.11);所有实验条件下,流动均发生临界流现象,即CO2通过短管的流量对下游压力不敏感,对进出口倒角也不敏感.

Refrigerant-744 flow through a short-tube orifice was investigated. R744 flow depending upon upstream pressure, upstream superheating, downstream pressure, and short-tube geometries was examined. A correlation for mass flow rate prediction was developed based on a large amount of experimental data. The experimental results show that the flow of R744 through a short-tube orifice is greatly different from that of a conventional refrigerant such as R134a. The choked flow exists in all cases. The R744 flow is strongly affected by the diameter of tube, and it is proportional to the upstream pressure but is insensitive to the inlet and exit chamfering.