1. Explain the significance of combined forced and natural convection. What is the role of the parameter Gr/Re 2 in this regard? 2. When does the effect of buoyancy force become important in forced...

1. Explain the significance of combined forced and natural convection. What is the role of the parameter Gr/Re²
in this regard?

2. When does the effect of buoyancy force become important in forced convection heat transfer? How is Graetz number relevant in combined convection?