BEYOND THE POINT C, RADIATION BECOMES SIGNIFICANT OF THESE STATEMEN...

4. Beyond the point C, radiation

becomes significant

Of

these

statements:

(a) 1, 2 and 4 are correct

(b) 1, 3 and 4 are correct

(c) 2, 3 and 4 are correct

(d) 1, 2 and 3 are correct

IES-8.

Assertion (A): If the heat fluxes in pool boiling over a horizontal surface

is increased above the critical heat flux, the temperature difference

between the surface and liquid decreases sharply.

[IES-2003]

Reason (R): With increasing heat flux beyond the value corresponding

to the critical heat flux, a stage is reached when the rate of formation

of bubbles is so high that they start to coalesce and blanket the surface

with a vapour film.

(a) Both A and R are individually true and R is the correct explanation of A

(b) Both A and R are individually true but R is not the correct explanation of A

(c) A is true but R is false

(d) A is false but R is true

IES-9.

In spite of large heat transfer coefficients in boiling liquids, fins are

used advantageously when the entire surface is exposed to: [IES-1994]

(a) Nucleate boiling

(b) Film boiling

(c) Transition boiling

(d) All modes of boiling

IES-10. When a liquid flows through a tube with sub-cooled or saturated

boiling, what is the process known?

[IES-2009]

(a) Pool boiling

(b) Bulk boiling

(c) Convection boiling

(d) Forced convection boiling

Page 57 of 97

IES-11. For film-wise condensation on a vertical plane, the film thickness

δ

and heat transfer coefficient h vary with distance x from the leading

edge as

[IES-2010]

(a)

δ

decreases, h increases

(b) Both

δ

and h increase

(c)

δ

increases, h decreases

(d) Both

δ

and h decrease

IES-12. Saturated steam is allowed to condense over a vertical flat surface and

the condensate film flows down the surface. The local heat transfer

coefficient for condensation

[IES-1999]

(a) Remains constant at all locations of the surface

(b) Decreases with increasing distance from the top of the surface

(c) Increases with increasing thickness of condensate film

(d) Increases with decreasing temperature differential between the surface and

vapour

IES-13. Consider the following statements:

[IES-1998]