Comparison of water vapour condensation in vertically oriented pipes of condensers with internal and external heat rejection

This paper deals with the intensification of water vapour condensation in vertical pipes. Two configurations of vertical condensers are compared. A standard configuration and a novel configuration with cooling water at the inner pipe wall in direct contact with the condensing vapour. For this configuration, a detailed mathematical model of heat transfer is made using empirical relationships to describe the behaviour of the liquid film and vapour. The focus is placed on a detailed description of the processes at the vapour-liquid interface. The results of the mathematical model are compared with an experimental study in which the real condensing power was assessed depending on the vapour mass flow rate, the cooling water temperature at the pipe inlet, and the volumetric flow rate of the cooling water. This paper presents specific mean heat transfer coefficients useable for design calculations. The results show that the heat transfer coefficient is proportional to the liquid film temperature as well as the vapour flow rate. The condensers are compared with the same vapour flow rate and cooling water temperature. The novel configuration rejects the same amount of condensation heat as the standard configuration, but only requires a third of the amount of cooling water.