(109b) Design Optimisation of Multi-Stream Plate Fin Heat Exchangers

Design Optimisation of Multi-stream Plate Fin Heat Exchangers

Kunpeng Guo, Nan Zhang, Robin Smith

Centre for Process Integration, School of Chemical Engineering and Analytical Science, the University of Manchester, Manchester, M13 9PL, United Kingdom

With small minimum temperature approach, large surface area per volume, high heat transfer coefficient and possibility of handling several streams, multi-stream plate fin heat exchangers, categorized as compact heat exchangers, are widely used in various industrial areas such as chemical, petrochemical processes, cryogenics and aerospace industries [1]. Compared with shell and tube heat exchangers, plate fin heat exchangers have larger heat transfer load per unit volume. Consequently, the capital cost and the process operating cost will be reduced to a large extent.

However, according to Kays and London [2], there are approximately sixty standardised fin parts with fixed geometry and heat transfer and pressure drop performance. A major challenge in designing optimal multi-stream plate fin heat exchangers is the large number of combinations of standardised fin geometries for various fin types to choose from, which adds discrete aspects to an already complicated design problem. Another challenge is the difficulty of simultaneous optimisation of fin selection and imposed pressure drop constraints caused by discrete heat transfer and pressure drop performance of standardised fin types [3], especially if one wants to consider the possibility of mixing different fin types in the same device to enhance the heat transfer performance.

In this work, a new design algorithm is proposed to mix and match fin types used in a single heat exchanger and optimise fin selection and consider pressure drop simultaneously. By treating basic fin geometries such as plate spacing, fin pitch, fin thickness and fin length as variables, and considering thermal hydraulic performance of different fin types as a function of basic fin geometries, the optimal fin types and their corresponding design parameters can be obtained by minimising the total volume or capital cost of heat exchanger. A case study from the literature are presented to illustrate the efficiency and accuracy of the proposed algorithm. The result shows that the new algorithm can give an optimum configuration with short computational time and accuracy compared to the published design methodologies.

Key words:

Plate-fin heat exchanger design optimisation mix and match

Reference:

[1] Yousefi, M., Enayatifar, R., Darus, A.N. and Abdullah, A.H., Optimization of plate-fin heat exchangers by an improved harmony search algorithm. Applied Thermal Engineering, 50 (2013): 877-885.

[2] Kays, W. M. and London, A. L., Compact heat exchangers. New York: McGraw-Hill Book Co, 1984.

[3] Guo, K., Zhang, N., Smith, R., Optimisation of fin selection and thermal design of plate-fin heat exchangers, Chemical Engineering Transactions, 39(2014), 325-330.