The equilibrium approach of Silver(1) and Bell and Ghaly(2), is widely used
in the industrial design of condensers because it usually gives acceptable
accuracy, though it is acknowledged to be less reliable than the film mode
l approach developed by Colburn et al.(3,4). It fails to describe wet wall
de-superheating of superheated vapour mixtures but has been successfully mo
dified by McNaught(5) for this case. This work shows that Silver-Bell also
fails to describe the condensation of vapour mixtures forming immiscible co
ndensates with acceptable accuracy. A new modification, similar to that of
McNaught, is proposed and shown to give good predictions of experimental da
ta, measured in a shell and tube condenser of industrial scale.