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The Axial Dispersion Model for Heat Transfer Equipment: A Review
Sarit K. Das and Wilfried Roetzel

Accurate modelling of heat exchangers is a formidable challenge even in this age of high speed computation. The axial dispersion model, which originated as a tool for fluid flow analysis about half a century ago, has drawn immense attraction in this respect during the recent years. Originally devised to analyse dispersion of concentration profile in flow situations deviating from the so called “plug flow”, the model has been reinforced by its capability to represent heat transfer phenomenon as well. This has given a boom in the last decade to use the model for heat transfer equipment. In fact the method can be seen as a bridge between computation and experiment providing simple means to predict the response of heat exchangers – both steady state and transient. The present review traces the origin of axial dispersion model and then concentrates mostly on application of this concept to the analysis of heat transfer equipment. The development, with respect to fundamental concept, application to heat exchangers of different types and experimental techniques for estimation of dispersion parameter, is discussed in details, indicating probable future direction of research in this area. Certain well used propositions, such as Danckwert boundary condition at exit which has been used by many researchers so far without any rigorous proof, have been justified in this paper for the first time combining the application of the First and the Second Law of thermodynamics. The subsequent development of ‘hyperbolic dispersion model’ has also been discussed in details.

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