Abstract
Regarding the gas-liquid refrigerant flow in the multi-pass channel with a vertical header and horizontal branch tubes that simulates the parallel-flow type heat exchanger used for air conditioners, an attempt was made to improve the liquid distribution uniformity by supplying the refrigerant from the pipe with multiple outlet holes inserted in the inlet header. In particular, with the branch tubes heated evenly (20 - 100 W/tube), the flow in the header was visually observed and the gas liquid distributions to each branch tube were measured to make clear the influence of refrigerant evaporation in branch tubes on the effect of the multi-hole inner pipe. It was found that, similar to the standard channel without the inner pipe, the uniformity of the liquid distribution was improved by increasing the thermal loads in the channel with the multi-hole inner pipe. The influence of the evaporation of liquid refrigerant on the liquid distribution characteristics, however, were somewhat smaller than that observed in the standard channel. Experiments were also conducted under non-uniform heating conditions in which the heating loads on the branch tubes were changed for each tube, and the influence of the heating-load distribution on the liquid distribution was also investigated.
