Diffusion effects on multicomponent condensation - influence of glide on mass transfer resistance
Paper in proceedings, 2003
The influence of glide on mass transfer resistance effects is investigated theoretically for condensation of zeotropic mixtures on the outside of horizontal tube banks. Calculations for different compositions of R134a/R32, corresponding to different glides, are carried out to give a measure at what glide mass transfer effects can be apparent enough to be considered when designing multicomponent condensers. In the calculations, mass transfer by diffusion is considered in both phases, and together with a heat balance the rate of condensation is determined locally. Results for high duties show a significant influence of mass transfer resistance on heat transfer at glides higher than about 4 K. For part loads the influence is even greater. Already at a glide of 1 K there is a significant decrease in heat transfer rate. At a glide of 5.5 K, corresponding to the glide of R407C, the decrease in heat transfer rate is around 20% at a high duty and as much as 75% at a lower duty.