Question

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

Answer 1

d)1241W

Step-by-step explanation:

We know that drag force given as

`F_D=(1)/(2) \rho C_D AV^2`

Given that
`F_D=0.1N`

`A=1 m^2`

V=3 m/s

`\rho =1.204 kg/m^3`

Now by putting the values

`0.1=(1)/(2) * 1.204 C_D* 1* 3^2`

`C_D=0.018`

Now from Reynold's analogy

`St* Pr^{(2)/(3)}=(C_D)/(2)`

Now by putting the values

`St* 0.7309^{(2)/(3)}=(0.018)/(2)` (Pr=0.7309 given)

So St=0.0111

We know that
`St=(h)/(\rho VC_p)`

⇒
`0.0111=(h)/(1.204* 3* 1007)`

So
`h=41.37 (W)/(m^2-k)`

We know that heat transfer given as

Q=hAΔT

Here given that ΔT=30°C

So now by putting the values

`Q=41.37 * 1* 30`

So heat rate from plate=1241.1W

So our answer is d.