TUTORIAL AE 726 & AE 460-HEAT TRANSFER FOR AEROSPACE APPLICATIONS

1) A cylindrical fin is 3mm in dia and 3cm long. Calculate and compare the value of the temperature at the fin tip if the fin is made up of (a) copper (k=350W/m K) (b) stainless steel (k=15 W/m K) (c) Teflon (k=0.350W/m K). Take h =10 W/m2K and Tf=200C and T1=1200C and assume heat loss from the fin tip is negligible.

2) Calculate a heat loss rate from a surface of a rectangular fin of length 2cm on a plane wall. The thickness of the fin is 2mm and its breadth is 20cm. Take θ1=2000C, h=15 W/m2K and K=45 W/m K and assume the heat loss from the fin tip is negligible.

3) In order to reduce the thermal resistance at the surface of a vertical plane wall (50x50 cm), 100 pin fins (1 cm dia., 10 cm long) are attached. If the pin fins are made of copper having thermal conductivity of 300 W/mK and the values of surface heat transfer coefficient is 15 W/m2K, calculate the decrease in thermal resistance. Also calculate the component increase in heat transfer rate from the wall it is maintained at T=2000C and the surrounding are at 200C.

4) A straight fin fabricated from 2024 Aluminum alloy (k= 185W/m.K) has a base thickness of t=3mm and a length of L=15 mm. its base temperature is Tb = 1000C and it is exposed to a fluid for which T∞=200C and h=50W/m2K. For the foregoing condition and for a fin of unit width, compare the fin rate, efficiency, volume for rectangular, triangular, and parabolic profiles.

5) A spherical shell of inner and outer radii ri and ro respectively contains heat dissipating components and at a particular instant the temperature distribution in the shell is known to be of the form T(r) = (C1/r)+C2. Are the conditions steady state or transient? how do the heat flux and heat rate vary with radius.