
#1
Mar2013, 12:42 PM

P: 1

1. The problem statement, all variables and given/known data
A straight, rectangular fin made from 2024 aluminium has a thickness of t = 3mm and length L = 20mm. Base temperature is 100 °C and it is exposed to a fluid at 20 °C. h = 60 W/m^2K k = 185 W/mK (a) Determine the heat transfer rate from the fin to the fluid per unit length (b) Repeat (a) if the fin is made of copper (h = 400 W/m^2K) 2. Relevant equations η_{o} = 1  (NAc/At) (1η_{f}) A_{t} = NA_{c}+A_{b} 3. The attempt at a solution n_{f} = tanh(mL_{c})/mL_{c} (I know this equation is right, but I'm lost from this point forward. Any help would be excellent.) 



#2
Mar2013, 05:50 PM

Sci Advisor
HW Helper
Thanks
PF Gold
P: 4,445

Do you know how to write the steady state differential heat balance equation for a cooling fin, including the conductive heat transfer along the fin and the convective heat transfer from the fin to the surrounding air? If so, lets see it.
Chet 



#3
Mar2013, 06:15 PM

P: 197

There's formulas for this...it's really plug and chug, you're given everything you need.
You need to calculate your m and M for a rectangular fin m=(2h/kt)^1/2; plug in your h, k and thickness For a rectangular fin M= (2hw^2tk)^1/2 *(tbtinfinity) again substitute your h,k, width and thickness. Now that you have M and m you can just apply the formula, you have everything you need. 


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