High Fins

High Fins To calculate heat-transfer coefficients for cross-flow to a transversely finned surface, it is best to use a correlation based on experimental data for that surface. Such data are not often available, and a more general correlation must be used, making allowance for the possible error. Probably the best general correlation for bundles of finned tubes is given by Schmidt [Knltetechnik, 15, 98-102, 370-378 (1963)] ... 

Low-fin tubes (Mfi-in-high fins) provide 2.5 times the surface per lineal foot. Surface required should be divided by 2.5 then use Fig. 11-41 to determine basic cost of the heat exchanger. Actual surface times extra costs (from Table 11-14) should then be added to determine cost of fin-tube exchanger. 

Figure 10-10C. Bimetal high-finned tube. (Used by permission Wolverine Tube, Inc.)...

Figure 10-10H. Geometrical dimensions for High-Finned Wolverine Trufin tubes. The fins are integral with the basic tube wall. (Used by permission Wolverine Tube, Inc., Engineering Data Book, II, 1984.)...

These two may not be the same. In some instances, high-finned surface area but low bare tube surfece means that a lot of tall (sometimes less efficient) fins are crowded onto the tube. In this case, horsepower might be expected to be higher. 

Banks of radial high-fin tubes e = (bare tube surface)/(total surface of finned tube)... 

A small value of thermal resistance indicates a small temperature drop across the heat sink, and thus a high fin efficiency. 

In-line banks of high-finned tubes are not usually used in air-cooled heat-transfer equipment because the preferential flow path between the fin tips of adjacent tubes allows flow bypassing and reduces the apparent heat-transfer coefficient. This effect tends to disappear in the deeper tube banks used in convection sections of fired heaters. 

The heat transfer from the lateral fin surfaces together with the supporting cylinder were correlated [269] for high fins, 1.67 < Did < °°, by... 

XheC-C.fins are desjgned with stffi te.a,[low.forlow.tberrT]al resistance (high fin.. ... 

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