Compact heat exchangers extended surface

For extended surfaces, which include fins mounted perpendicularly to the tubes or spiral-wound fins, pin fins, plate fins, and so on, friction data for the specific surface involved should be used. For details, see Kays and London (Compact Heat Exchangers, 2d ed., McGraw-HiU, New York, 1964). If specific data are unavailable, the correlation by Gunter and Shaw (Trans. ASME, 67, 643-660 [1945]) may be used as an approximation. 

Tlie fin is the most common fonn of extended surface, associated with both tubular and plate-type heat exchangers - the car radiator is a highly compact finned unit. Most heat exchangers used in gas streams have fins to improve the gas-side heat transfer. Compact units such as the plate-fin heat exchanger have fins, or secondary surfaces , between each pair of plates. Fins are used in both natural and forced convection. They are also used, when they are sometimes called ribs, to aid boiling or to provide drainage... 

Advantages of the foam include a choice of metals resistant to temperatures up to 1000°C, low density, compact size and the ability to be formed into complex shapes. The foam can be catalysed, a feature that could be highly relevant to HEX-reactors. Extended surfaces and other features of compact/intensified heat exchangers are covered in full by Hesselgreaves (2001). 

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