Straight fin

FIGURE 9.12 Diagram for determining the heat transfer coefficient for a straight fin plate. 

Assuming that the height of the fin is small compared with its circumference and that it may be treated as a straight fin of length (jr/2)(d] + dj), then ... 

Numerous fin corrugations have been developed, each with its own special characteristics (Figure 15). Straight fins and straight perforated fins act like parallel tubes with a rectangular cross section. Convective heat exchange occurs due to the friction of the fluid in contact with the surface of the fin. The channels of serrated fins are discontinuous, and the walls of the fins are offset. For air flows,... 

Efficiency of straight fins of rectangular, triangular, and parabolic profiles. 

Fig. 1.14 Examples of extended surface, a straight fins, b pins, c circular fins...

This differential equation covers all forms of extended surfaces, as long as the aforementioned assumptions are met. The different fin or pin shapes are expressed by the terms Aq = Aq(x) for the cross sectional area and Af = Af(x) for the fin surface area over which the heat is released. So for a straight fin of width b perpendicular to the drawing plane in Fig. 2.11, with a profile function y = y(x) we obtain the following for the two areas... 

Fig. 2.11 Straight fin of width b (perpendicular to drawing plane) with any profile function y = y(x)...

Fig. 2.13 Temperature distribution in a straight fin with a rectangular profile (fin thickness

In the following we will deal with a straight fin with a rectangular profile. Its thickness will be indicated by <5f, so that the profile function y(x) = 5 /2 in Fig. 2.11 is valid. From (2.67) follows the simple differential equation... 

Fig. 2.14 Efficiency rjt of a straight fin with a rectangular profile according to...

The heat flow Qt for a straight fin with a rectangular profile was calculated in the last section. Using (2.74) and j4q0 = bSt it follows from (2.76) that... 

Chen, S.-Y. Zyskowski, G.L. Steady-state heat conduction in a straight fin with variable film coefficient. ASME-Paper No. 63-HT-12 (1963)... 

Plate fins are categorized as (1) plain (i.e., uncut) and straight fins such as plain triangular and rectangular fins, (2) plain but wavy fins (wavy in the main fluid flow direction), and (3) interrupted fins such as offset strip, louver, and perforated. Examples of commonly used fins are shown in Fig. 17.13. 

The expressions for 1-D fin efficiency formulas for some common fins are presented in Table 17.7. For other fin geometries, refer to Refs. 13 and 14. The fin efficiencies for straight (first and third from the top in Table 17.7) and circular (seventh from the top in Table 17.7) fins of uniform thickness 8 are presented in Fig. 17.27 (relr = 1 for the straight fin). 

L. J. Huang and R. K. Shah, Assessment of Calculation Methods for Efficiency of Straight Fins of Rectangular Profile, Int. J. Heat Fluid Flow, Vol. 13, pp. 282-293,1992. 

Figure 4.13-5. Fin efficiency rj for various fins (a) longitudinal or straight fins, (b) circular or transverse fins. See Fig. 4.13-3 for the dimensions of the fins.)...

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