As the difference between the wall temperature and bulk temperature increases, the boiling heat transfer co-efficient

The scales form in heat exchanges after a period of operation and provide additional resistance to heat transfer with some heat transfer coefficient . The reciprocal of this scale heat transfer coefficient is called .

A

scaling factor

B

forming factor

C

resisting factor

D

fouling factor

Extended heat transfer surface like fins are used to increase the heat transfer rate. Fin efficiency is defined as the ratio of heat transferred across the fin surface to the theoretical heat transfer across an equal area held at the

A

Surrounding temperature

B

Average temperature of the fin

C

Temperature of the fin end

D

Constant temperature equal to that of the base

The rate of heat transfer from a vertical plate by natural convection depends upon the temperature differences (ΔT) between wall and outside bulk. The proportionality is given as

A

$${\left( {\Delta {\text{T}}} \right)^{\frac{1}{4}}}$$

B

$${\left( {\Delta {\text{T}}} \right)^{\frac{1}{2}}}$$

C

$${\left( {\Delta {\text{T}}} \right)^{\frac{5}{4}}}$$

D

$${\left( {\Delta {\text{T}}} \right)^{\frac{3}{4}}}$$

The distillation carried out in such a way that the liquid with the lowest boiling point is first evaporated and re-condensed, then the liquid with the next higher boiling point is then evaporated and re-condensed, and so on until all the available liquid fuels are separately recovered in the sequence of their boiling points. Such a process is called

A

Cracking

B

Fractional distillation

C

Full distillation

D

Carbonisation

A marble ball is rolled on a smooth floor of a room to hit a wall. If the time taken by the ball in returning to the point of projection is twice the time taken in reaching the wall, the coefficient of restitution between the ball and the wall, is

A

0.25

B

0.50

C

0.75

D

1.0

A glass ball is shot to hit a wall from a point on a smooth floor. If the ball returns back to the point of projection in twice the time taken in reaching the wall, the coefficient of restitution between the glass ball and the wall is

A

0.25

B

0.33

C

0.40

D

0.50

Even though heat transfer co-efficients in boiling liquids is large, use of fins is advantageous, when the entire surface is exposed to __________ boiling.

A

Film

B

Nucleate

C

Transition

D

All of the above

In spite of large heat transfer co-efficients in boiling liquids, fins are used advantageously, where the entire surface is exposed to __________ boiling.

A

Film

B

Nucleate

C

Transition

D

All of the above

Heat flux increases with temperature drop beyond the Leiden frost point in the plot of heat flux vs. temperature drop for a boiling liquid, because

A

Convection becomes important

B

Conduction becomes important

C

Radiation becomes important

D

Sub-cooled boiling occurs

A ladder is resting against a vertical wall and its bottom is 2.5 m away from the wall. If it slips 0.8 m down the wall, then its bottom will move away from the wall by 1.4 m. What is the length of the ladder?

A

6.2 m

B

6.5 m

C

6.8 m

D

\7.5 m

As the difference between the wall temperature and bulk temperature increases, the boiling heat transfer co-efficient

Related Questions