Passive enhancement of condensation heat transfer

Integral fin tubes are commonly used in the condensers of refrigeration, air conditioning and process industries especially where low surface tension fluids are used. In the last few decades, several three dimensional (3D) enhanced surfaces were developed for condensation heat exchangers. Also, several improvements were introduced to the standard integral finned tubes which resulted in a performance comparable to that of the 3D enhanced surfaces. Some of these improvements include optimisation of the fin specifications and the fin profile to make use of the surface tension and gravity forces, the use of ribs on the surface of the fins and the inclusion of drainage techniques. A review of the experimental and theoretical work used to augment the performance of integral finned tubes is presented in this paper. This is followed with a review of the 3D surfaces developed and a comparison between the integral fin tubes and the 3D surfaces. Performance in bundles and the effect of vapour shear are specific issues that were considered in the comparison.