4 rectangular fins are assembled on a 40x40x60 mm aluminum heat sink with the fi

Question

4 rectangular fins are assembled on a 40x40x60 mm aluminum heat sink with the fins being 30 mm long, t=4.0 mm wide. The system generates 3.0 W and the room temperature is maintained at 20 C. What is the temperature at the substrate surface that holds the fins, assuming the system is at steady state? Also, what is the heat transfer coefficient at the temperature for the system? The kinetic viscosity of air (k)=0.026 W/m-K. For the aluminum (which oxidizes a bit), k=160W/m-K. Will the Prandtl number always stay the same or is it an assumption? Explain

Explanation / Answer

Area of fins= 30*4= 120 x10-6m

Q= 3W

Q= u1A1? t

Heat transfer coefficient

U1= k1/x1=   160/30*10-3= 5.33 x 103 w/m2k

From the above eqn

Q= u1a1? t

3=5.33*103*120 x10-6*(t- 293)

T=297.69 K

Since prandtl no= cp? /k

So it

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