(adsbygoogle = window.adsbygoogle || []).push({}); A 2-m x 3-m flat plate is suspended in a room, and is subjected to air flow parallel to its surfaces along its 3-m-long side. The free stream temperature and velocity of the air are 20^{o}C and 7m/s. the total drag force acting on the plate is measured to be 0.86N. Determine the average heat transfer coefficient for the plate. Answer:h=12.7W/m^{2}K

Properties of air at 300K(from my textbook

ρ=1.1763

c=1.007e03

μ=1.862e-05

v=1.5e-05

Pr=0.717

k=2.614e-02

Attempt at a solution

Re_{L}=UL/v=7*3/1.5e-05=1.5e06 >5e05

x_{cr}=(Re_{cr}v)/U=1.07

Nu_{x,Laminar}=0.332Pr^{1/3}Re_{x}^{1/2}

Nu_{x,Turbulent}=(0.0296Re^{0.8}Pr)/(1+2.11Re_{x}^{-0.1}(Pr-1))

Avg heat coeff

=(1/L){_{0}∫^{xcr}h_{x, Laminar}dx +_{xcr}∫^{3}h_{x, Turbulent}dx}

= (1/L){_{0}∫^{xcr}Nu_{x, Laminar}(k/x)dx +_{xcr}∫^{3}Nu_{x, Turbulent}(k/x)dx}

= ...

=14.39

I did approximate 1+2.11Re_{x}^{-0.1}(Pr-1) to be equal to 1 in my working because I didn't know how to integrate it. Is that acceptable? And I don't know how to use the drag force provided in this question. :x

I've been pondering over this question for a few days and I still can't get the answer please help check if my approach is correct. Thank you.

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# Homework help:Heat transfer coefficient of flow over a flat plate

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