An Improved Method for Predicting Heat Exchanger Network Area

Abstract

Successful application of pinch analysis to any process, be it for grassroots design or retrofit, depends upon the extent to which set targets are achieved in practice. This entails predicating the three stages of process integration namely targeting, synthesis and detailed design on the same basis. There exist gap between these three stages largely due to inaccuracies in film heat transfer coefficient and inability to replicate same at the various stages. This paper presents an improved methodology for area targeting that is consistent with detailed design of an exchanger not just because it is premised on the same basis of pressure drop constraints but, more importantly, because it allows, for necessary variation of stream properties with temperature. The validity of the methodology has been tested using two case studies from the literature. The results obtained in all studies reveal a difference of less than 2% between targeting, synthesis and detailed design with the new methodology. This is contrary to the difference of as high as 59% between targeting and detailed design obtained with the state-of-the-art methodology. There is therefore an excellent agreement between the three stages of process integration arising from the new methodology.

Keywords: heat exchanger network, area targeting, synthesis, detailed design, pressure drop, film heat transfer coefficient.