Question: Straight rectangular fins (k=220 W/mK) are going to be attached to a round flat surface (diameter=0.7 m) kept at 150 °C. Total base area and total surface area of the attached fins are 0.06 m2 and 4 m2, respectively. Temperature of the surrounding medium is 25 °C, and the heat transfer coefficient on the surfaces is 20 W/m²K. What should be the efficiency of the fins to have an overall effectiveness of 9 ?
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