two-phase, distributor, flow regime, distribution, visualization
Conical refrigerant distributors are usually used to improve the distribution of two-phase flow to each circuit of the DX evaporators. A nozzle is commonly added before a cone to homogenize two-phase flow and that way unify distribution among channels. However, when the nozzle is not properly sized or, in some cases, there is no nozzle, the distributor performance is much affected by the flow regimes at the distributor inlet. This paper presents the effect of the flow regime at the distributor inlet on the uniformity of two-phase flow distribution. In this case, the flow regime is determined by mass flux, quality, and distance from the expansion device. A high-speed camera is used to visualize the two-phase flow regimes between the expansion valve and distributor. The same technique is also used to interrogate the flow regime inside the distributor. We relate the distributor performance with flow regimes at the distributor inlet to understand the two-phase distribution behavior. The experiments using the distributor with the original design is set as the baseline. After acquiring results for the baseline situation, we implemented two approaches to change the flow regime at the distributor inlet besides changing the operating conditions. The first is adding an orifice to remix the two-phase flow, and the second is increasing the distance between the distributor and the expansion valve to make the two-phase flow fully developed. The average deviations of capacity for each branch are 6-10% for the baseline case, less than 2% for the distributor with an orifice, and 20% for the distributor with a 600mm inlet tube.