7. depends upon density of fluid but not b. depends on fluid velocity and does o

Question

7. depends upon density of fluid but not b. depends on fluid velocity and does on its viscosity not depend on fluid properties c. depends on thermal conductivity of the| d. depends on velocity of the fluid and fluid, besides its density and viscosity. ts emissivity. 8. In the hydro dynamically fully developed flow region a. The velocity profile changes such b. The velocity profile does not changes in the flow direction and heat transfer coefficient is minimum that the profile becomes more flat. d. None of the above c. The velocity profile does not changes in the flow direction and heat transfer coefficient is maximum 9. A kind of heat transfer where fluid motion occurs due density difference is called, a. Forced convection b. Free convection c. Radiation d. None of the above

Explanation / Answer

8) d none of the above.

In the hydrodynamically fully developed flow region, the velocity profile does not change in the flow direction.

Heat transfer coefficient remains constant for a thermally fully developed flow in a pipe, for constant heat flow and surface temperature.

9) b Free convention

In natural or free convection the fluid motion occurs due to the density differences. As the cold fluid comes in contact with hot surface, the fluid particles next to the hot body get heated and their density decreases and move upwards due to buoyancy. Next layer of fluid particles come next to hot body and the process repeats until equilibrium is achieved.

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