1. Why are heat transfer coefficients for natural convection much less than those in forced convection? 2. Explain the velocity and temperature profiles for air filling the gap between two horizontal...

1. Why are heat transfer coefficients for natural convection much less than those in forced convection?

2. Explain the velocity and temperature profiles for air filling the gap between two horizontal plates when (a) the bottom plate is maintained at a temperature higher than the top plate and (b) the bottom plate is maintained at a temperature lower than the top plate.