Question

Air at 20 C and 1 atm flows over a flat plate at 35 m/s. The plate is 75 cm long and is maintained at 60 с. Assuming unit depth in the x direction, calculate the heat transfer from the plate.

Answer 1

Q=3198.744 W/m

Step-by-step explanation:

Given that

Air temperature=20 C

Velocity V= 35 m/s

Temperature of surface= 60 C

Length of plate= 75 cm

Now first find the properties of air at mean temperature of 20 and 60,it means that properties of air at temperature 40 C

`\rho=1.12 (Kg)/(m^3)`

`\\u =1.69* 10^(-5)(m^2)/(s)`

`K=0.027(W)/(m-K)`

Pr=0.71

Lets find the Reynolds number

`Re=(vL)/(\\u )`

`Re=(35*0.75)/(1.69* 10^(-5))`

`Re=15.53*10^5`

So this is turbulent flow

Nusselt equation of turbulent flow

`Nu=0.037Re^{(4)/(5)}Pr^{(1)/(3)}`

Now by putting the values

`Nu=0.037* (15.53*10^5)^{(4)/(5)}* 0.71^{(1)/(3)}`

Nu=2961.68

We know that

`NU=(hL)/(K_(air))`

So

`2961.68=(h* 0.75)/(0.027)`

`h=106.68(W)/(m^2-K)`

So heat transfer

Q=hAΔT

Q=106.68 x 0.75 x 1 x (60-20)

Q=3198.744 W/m