The optimal dimensions of convective-radiating circular fins |
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Authors: | Jameel-ur-Rehman Khan S M Zubair |
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Institution: | (1) Mechanical Engineering Department King Fahd University of Petroleum and Minerals Dhahran 31261, Saudi Arabia, SA |
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Abstract: | The optimal dimensions of convective-radiating circular fins with variable profile, heat-transfer coefficient and thermal
conductivity, as well as internal heat generation are obtained. A profile of the form y=(w/2) 1+(r
o/r)
n
] is studied, while variation of thermal conductivity is of the form k=k
o1+ɛ((T−T
∞)/ (T
b−T
∞))
m
]. The heat-transfer coefficient is assumed to vary according to a power law with distance from the bore, expressed as h=K(r−r
o)/(r
e−r
o)]λ. The results for λ=0 to λ=1.9, and −0.4≤ɛ≤0.4, have been expressed by suitable dimensionless parameters. A correlation for
the optimal dimensions of a constant and variable profile fins is presented in terms of reduced heat-transfer rate. It is
found that a (quadratic) hyperbolic circular fin with n=2 gives an optimum performance. The effect of radiation on the fin performance is found to be considerable for fins operating
at higher base temperatures, whereas the effect of variable thermal conductivity on the optimal dimensions is negligible for
the variable profile fin. It is also observed, in general, that the optimal fin length and the optimal fin base thickness
are greater when compared to constant fin thickness.
Received on 22 February 1999 |
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Keywords: | |
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