Flow fields in shell-and-tube condensers: comparison of a pure refrigerant and a binary mixture

Detailed 2D CFD calculations for vapour flow field and rate of condensation are carried out for a geometry similar to a real shell-and-tube condenser with 100 tubes, with condensation on the shell-side. The differences in vapour flow behaviour are investigated for pure R22 and for a binary mixture of R32 and R134a, which has a gliding temperature difference of 5.5 K. It is shown that, the flow field for a zeotropic mixture is significantly different from that for a pure fluid. The nature of the mixture flow causes the vapour and condensate to flow counter-currently in part of the condenser. Adjustments of the inlet design turn out to influence the rate of heat transfer by up to 24% for the conditions tested, with greater influence on heat transfer for lower driving forces.