The use of minimum flux instead of minimum approach temperature as a design specification for heat exchanger networks

Abstract

In this paper it is proposed that a minimum flux be used in the synthesis of heat exchanger networks as the basic design parameter to be varied in evaluating the utility/area trade-off. The minimum flux replaces the minimum approach temperature which will be derived for each stream from the minimum flux and the stream heat transfer coefficient. This eliminates the multi-variable optimisation which results when stream-dependent minimum approach temperatures are used. Values of minimum flux in the range 1000–3500 W/m 2 are recommended. Typical values of stream heat transfer coefficient for different types of streams lead to a wider range of minimum approach temperatures than have been used in the past. This approach is applied to two practical examples.