A rectangular cooper plate 10 cm ´ 50 cm, having a mass of 1 kg and at a temperature of 100 0C, is suspended vertically in still air at 20 0C so that 50 cm side is vertical. Neglecting radiation effect, find heat transfer coefficient due to natural convection and initial rate of cooling of the plate in 0C/ minute.
Take Cp for copper = 383 J/kg-K
The properties of air at mean temperature 60 0C are :
r = 1.06 kg/m3, v = 18.97 ´ 10–6 m2 / s
Pr = 0.696, Cp = 1.005 kJ/kg-K
k = 28.96 ´ 10–3 W/m-K
m = 20.1 ´ 10–6 N–s/m2.
You may use the following correlation :
Nu = 0.1 (Gr Pr)1/3
Will the result change if 10 cm side is vertical? Why?