Air at 5°C (ρ = 1.204 kg/m^3, Cp = 1007 J/kg.K, Pr = 0.7309) with a free stream velocity of 3 m/s is flowing over a 1 mx 1 m flat plate. The flat plate has a uniform surface temperature of 35°C. If the drag force asserted on the flat plate is 0.1 N, determine the rate of heat transfer from the plate. a)- 795W b. 964W c. 1083W d. 1241W

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Respuesta :

Netta00 Netta00 · Answer 1 · 2019-08-05T07:50:18+02:00

Answer:

d)1241W

Explanation:

We know that drag force given as

[tex]F_D=\dfrac{1}{2} \rho C_D AV^2[/tex]

Given that [tex]F_D=0.1N[/tex]

[tex]A=1 m^2[/tex]

V=3 m/s

[tex]\rho =1.204 kg/m^3[/tex]

Now by putting the values

[tex]0.1=\dfrac{1}{2} \times 1.204 C_D\times 1\times 3^2[/tex]

[tex]C_D=0.018[/tex]

Now from Reynold's analogy

[tex]St\times Pr^{\frac{2}{3}}=\dfrac{C_D}{2}[/tex]

Now by putting the values

[tex]St\times 0.7309^{\frac{2}{3}}=\dfrac{0.018}{2}[/tex] (Pr=0.7309 given)

So St=0.0111

We know that [tex]St=\dfrac{h}{\rho VC_p}[/tex]

⇒[tex]0.0111=\dfrac{h}{1.204\times 3\times 1007}[/tex]

So [tex]h=41.37 \dfrac{W}{m^2-k}[/tex]

We know that heat transfer given as

Q=hAΔT

Here given that ΔT=30°C

So now by putting the values

[tex]Q=41.37 \times 1\times 30[/tex]

So heat rate from plate=1241.1W

So our answer is d.