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# GATE 2023 || Heat Transfer || Quiz 51

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Question 1

The rate equation used to describe the mechanism of convection when the solid surface is cooled by fluid is prescribed by

Question 2

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 :

Question 3

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 _____.

Question 4

The average Nusselt number in turbulent natural convection from a vertical wall at 290 °C with still air at 20 °C is found to be 48. If the wall temperature become 30 °C, all other parameters remaining same, the average Nusselt number will be

Question 5

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 TW. 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 δt 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?

Question 6

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 (hx) at x=L is ____________.
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