Consider atmospheric air at 20°C and a velocity of 30 m/s flowing over both surfaces of a 1-m-long flat plate that is maintained at 130°C. Determine the rate of heat transfer per unit width from the plate for values of the critical Reynolds number corresponding to 105, 5 × 105, and 106.

given:

to determine avg temperature:

from the properties of air table A-4 corresponding to T avg=348 K approximately equal to 350 K so we can find:

A) case in which critical Reynolds number with value

Reynolds number is equal to :

calculating local nusselt number :

insert values and we get

now calculating the heat transfer coefficient:

calculating the rate of heat transfer per unit width of plate: