Engineering Archives

1431. In sub-cooled boiling,

Temperature of the heating surface is less than the boiling point of the liquid

Temperature of the heating surface is more than the boiling point of the liquid

Bubbles from heating surface are absorbed by the mass of the liquid

Very large vapour space is necessary

✅ The correct answer is option B.

1432. In a cooling tower, water becomes cool by

Loosing sensible heat

Heat transfer to surroundings

Vaporisation due to heat loss to air

Loosing latent heat

✅ The correct answer is option A.

1433. Duhring rule is important in solving problems on

Distillation

Crystallisation

Evaporation

Humidification

✅ The correct answer is option C.

1434. Corrosiveness of steam condensate is due to the presence of

CO₂

Dissolved O₂

Both A & B

Neither A nor B

✅ The correct answer is option C.

1435. __________ heat exchanger is used for chilling oil to be dewaxed.

U-tube

Double pipe

Fixed tube

Floating head

✅ The correct answer is option B.

1436. The average heat transfer co-efficient over the entire length of the plate (ha) and the local heat transfer co-efficient (hL), in case of heat transfer over a flat plate in lminar zone is related as

Ha = 0.8hL

Ha = 2hL

Ha = hL

Ha= 5hL

✅ The correct answer is option B.

1437. A metal wire of 0.01 m dia and thermal conductivity 200 W/m.K is exposed to a fluid stream with a convective heat transfer coefficient of 100 W/m².K. The Biot number is

5.6

0.025

3.5

0.0035

✅ The correct answer is option B.

1438. Value of Nusselt number [Nu = (hD/k)] for the heat transfer by conduction from a droplet or a spherical particle to a surrounding stagnant film is

0.5

100

✅ The correct answer is option B.

1439. Which of the following has the minimum absorptivity?

Aluminium foil

Coal dust

Refractory bricks

Iron plates

✅ The correct answer is option A.

1440. If the baffle spacing in a shell and tube heat exchanger increases, then the Reynolds number of the shell side fluid

Remains unchanged

Increases

Increases or decreases depending on number of shell passes

Decreases

✅ The correct answer is option D.