Heat transfer during reflux condensation of an R134a/R123 mixture in vertical and inclined narrow tubular and rectangular channels

Heat transfer during reflux condensation in a narrow tube (0.007 m inner diameter, 0.5 m length) and a rectangular channel (0.007 m hydraulic diameter, 0.5 m length) was investigated. The basic mechanism of this process, i.e. removing high boiling point components from a stream of a more volatile fluid or even from inert gases, is still not sufficiently understood. The study presents experimental results with the zeotropic mixture of R134a and R123 at a constant composition of the incoming vapour of 50 mol%. The results show that both, gas side heat and mass transfer resistances and the resistances in the liquid film influence the condensation process. Channel inclination is less important in mixture condensation than in pure fluid condensation but not negligible, and increasing vapour mass flow enhances mixture condensation. Contrary to pure fluid results heat transfer in the rectangular channel with the same hydraulic diameter is much smaller than in the tube at the same vapour mass flow rate.