A model describing the behaviour of an industrial scale shell-and-tube condenser is presented. The model can be used under steady-state as well as under transient conditions and is able to predict Vapour and condensate flow rates, pressure drop and the temperatures of the vapour, condensate, wall and coolant. The derivation of the material and energy balances is presented. Thus the apparatus is subdivided into increments corresponding to the location of the baffles in the condenser. Each of these baffle spaces is assumed to be fully mixed. The heat and material fluxes between the phases are determined using local transfer coefficients which are calculated for each baffle space. The model also includes the determination of the pressure profile along the apparatus. The results of several simulations are compared with experimental data to achieve a validation of the model. Both the steady-state and the transient behaviour of the condenser were examined, the latter when the system was subjected to step changes in each of the five key loads that determine the condenser behaviour. These are the pressure, steam how rate, air dow rate, coolant Bow rate and coolant inlet temperature. The results of the simulations agreed well with the experimental data.