GATE 2023 || Heat Transfer || Quiz 51

The local heat transfer coefficient ( in W/m²K ) at a point is given as . The average heat transfer coefficient for a length of 8 m is :

For fully developed flow through a pipe, the wall temperature is maintained at 500°C. If the fluid has thermal conductivity of 0.12 W/m-K and diameter of pipe is 15 cm, then the heat transfer coefficient (in W/m²K) will be _____.

Air at a temperature of T_∞ flows over a flat plate with a free stream velocity of U_∞. The plate is maintained at a constant temperature of T_W. Temperature,T of air at any location is given by,

Where y is the distance measured from the plate along its normal,
and δ  and δ_t are the hydrodynamic and thermal boundary layer thickness, respectively.
If the free stream temperature is 50°C and plate temperature is 200°C & the other properties of the fluid at mean temperature is given 

and hydrodynamic boundary layer thickness (δ )= 0.5 mm

Then, the value of heat transfer coefficient?

In an experiment, the local heat transfer over a flat plate were correlated in the form of local Nussult number as expressed by the following correlation.

The ratio of the average convection heat transfer coefficient () over the entire plate length to the local convection heat transfer convection heat transfer coefficient (h_x) at x=L is ____________.