The convective heat transfer coefficient from a hot cylindrical surface exposed to still air varies in accordance with
Where ΔT is the temperature difference between the hot surface and surrounding ambient air.
The nusselt number of convective heat transfer between a horizontal tube and water surrounding it is prescribed by the relation Nu = 0.52 (Gr Pr)0.25 for a 5 cm diameter tube, the heat transfer coefficient is 6000 W/m2-K. Subsequently, the tube is replaced by one with 20 cm diameter tube. If the temperature and surface of the fluid remain same, the heat transfer coefficient will change to
In convection heat transfer one of the significant dimensionless number is
Nusselt number in case of free convection is the function of
For free convection
Nu = f(Gr, Pr)
Rayleigh number = Gr x Pr.
When there is flow of fluid over a flat plate of length L the average heat transfer coefficient is given by (Nux = Local nusselt number)
The Grashoff number is
The temperature profile for heat transfer from one fluid to another separated by a solid wall is
Match List-I with List-II and select the correct