An isothermal vertical plate that is 50 cm high is suspended in atmospheric air. (a) Assume that air, which is at 20 ◦C temperature, flows in the vertical, downward direction at a velocity of 0.4 m/s...

An isothermal vertical plate that is 50 cm high is suspended in atmospheric air.

(a) Assume that air, which is at 20 ◦C temperature, flows in the vertical, downward direction at a velocity of 0.4 m/s parallel to the plate. Determine the lowest surface average temperature at which natural convection becomes significant.

(b) Repeat part (a), this time assuming that the air flow is in the upward direction.