Addition of New Heat Transfer Area in Retrofit

as discussed in Chapter 15, rather than install additional heat transfer area to cater for the new operational requirements, heat transfer enhancement can be considered. Changes to the number of tube passes or the baffle arrangement might allow the heat transfer coefficient to be enhanced. Alternatively, tube inserts could be used. This was discussed in Chapter 15. The major disadvantage in using heat transfer enhancement is that it increases the pressure drop. In retrofit this can be important, as the pumps driving the flow might be limited in their capacity to meet the required increase in pressure drop. 

These rules are both necessary and sufficient for the design to achieve the energy target given that no individual exchanger should have a temperature difference smaller than ATmin. 

The design of heat exchanger networks can be summarized in five steps. 

Divide the problem at the pinch into separate problems. 

The design for the separate problems is started at the pinch, moving away. 

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