Get more out of your heat exchangers with heat transfer enhancement : Part 1 – the basics
In this series of articles we will look at the idea of heat transfer enhancement . The benefits of enhancement are that your heat exchangers will provide the same performance at a lower cost or provide better performance at the same or smaller overall size and footprint .
By Himanshu Joshi , Heat Exchanger Specialist , and Lou Curcio , Heat Transfer Advisor
The purpose of a heat exchanger is to transfer heat ( provide a heat duty ), which requires a temperature difference and a surface across which the heat is transferred . In the process industry , the starting point for a heat exchanger design is almost always a shell-and-tube ( S & T ) heat exchanger with plain tubes , plain implying no fins or other surface modifications . Enhancement techniques result in heat exchangers which are smaller , less prone to failure ( more reliable ), have lower fouling , or are easier to maintain .
The heat duty is represented by this commonly used equation : Q = U * A * ∆T ( 1 ) Which can also be written as A = Q / ( U * ∆T ) ( 2 ) Q = heat duty [ W ] U = overall heat transfer coefficient , OHTC [ W / m 2 -C ] A = heat transfer surface area [ m 2 ] ΔT = Temperature driving force for heat transfer [ C ] Eq . ( 1 ) shows that we can increase the heat duty by increasing the surface area or the OHTC . It may be possible to increase the temperature difference , for example by ensuring fully countercurrent flow , but in practice the other two parameters have a significantly larger impact . Eq . ( 2 ) shows that for a fixed heat duty the surface area can be decreased by increasing the OHTC . A third aspect , not conveyed by these
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