Your company has developed a technique for forming very small fins on a plastic

Question

Your company has developed a technique for forming very small fins on a plastic substrate. The diameter of the fins at their base is D = 1 mm. The ratio of the length of the fin to the base diameter is the aspect ratio, AR = 10. The fins are arranged in a hexagonal close packed pattern. The ratio of the distance between fin centers and to the base diameter is the pitch ratio, PR = 2. The conductivity of the plastic material is k = 2.8 W/m-K. The heat transfer coefficient between the surface of the plastic and the surrounding gas is h = 35 W/m^2-K. The base temperature is T_b = 60 degree C and the gas temperature is T_infinity = 35 degree C. Determine the number of fins per unit area and the thermal resistance of the unfinned region of the base.

Explanation / Answer

tetta=Tb-Ta=60-35=25celsius

p=22/7*d=22/7 m

A=22/7/4*d*d=22/7*4m2

m=root over hp/KA=7.07

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