Fin Effectiveness (cont.)
- To increase ?f, the fin’s material should have higher thermal conductivity, k.
- It seems to be counterintuitive that the lower convection coefficient, h, the higher ?f. But it is not because if h is very high, it is not necessary to enhance heat transfer by adding heat fins. Therefore, heat fins are more effective if h is low. Observation: If fins are to be used on surfaces separating gas and liquid. Fins are usually placed on the gas side. (Why?)
- P/AC should be as high as possible. Use a square fin with a dimension of W by W as an example: P=4W, AC=W2, P/AC=(4/W). The smaller W, the higher the P/AC, and the higher ?f.
- Conclusion: It is preferred to use thin and closely spaced (to increase the total number) fins.