Questions and answers for exam Preparation

MCQs

Total Questions : 2525 | Page 28 of 253 pages

Question 271. If air (a non-condensing gas) is present in a condensing vapor stream, it will __________ the condensation rate of vapor.

Increase
Decrease
Not affect
Increase the condensing film co-efficient as well as

Discuss Question

Answer: Option B. -> Decrease

Question 272. In forced circulation, the heating element is injected

Internally
Externally
Both A and B
Neither A nor B

Discuss Question

Answer: Option A. -> Internally

Question 273. In a heat exchanger, the rate of heat transfer from the hot fluid to the cold fluid

Varies directly as the area and the LMTD
Directly proportional to LMTD and inversely proportional to the area
Varies as square of the area
None of these

Discuss Question

Answer: Option A. -> Varies directly as the area and the LMTD

Question 274. The heat flux (from outside to inside) across an insulating wall with thermal conductivity, K= 0.04 W/m.°K and thickness 0.16m is 10 W/m². The temperature of the inside wall is - 5°C. The outside wall temperature is

25°C
30°C
35°C
40°C

Discuss Question

Answer: Option C. -> 35°C

Question 275. 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

(ΔT)1/4
(ΔT)1/2
(ΔT)5/4
(ΔT)3/4

Discuss Question

Answer: Option D. -> (ΔT)3/4

Question 276. The radiation heat flux from a heating element at a temperature of 800°C, in a furnace maintained at 300°C is 8 kW/m². The flux, when the element temperature is increased to 1000°C for the same furnace temperature is

11.2 kW/m²
12.0 kW/m²
14.6 kW/m²
16.5 kW/m²

Discuss Question

Answer: Option D. -> 16.5 kW/m²

Question 277. Pick out the wrong statement.

Fluid movement under the influence of buoyant forces resulting from change in density takes place in case of natural convection
The ratio NNu/NRe . Npr is called the Stanton number
The Peclet number is a measure of the ratio of energy transport by convection to that by conduction
The Colbum jH factor for heat transfer is given by Nst Npr

Discuss Question

Answer: Option D. -> The Colbum jH factor for heat transfer is given by Nst Npr

Question 278. Radiation energy is emitted by all the substances, which are above

0°K
0°C
100°C
Room temperature

Discuss Question

Answer: Option A. -> 0°K

Question 279. The purpose of floating head in a heat exchanger is to

Avoid buckling of tubes
Provide support for tubes
Decrease the pressure drop
Facilitate its lengthening, if needed

Discuss Question

Answer: Option A. -> Avoid buckling of tubes

Question 280. Extremely large or small volumes of fluids are generally best routed through the shell side of a shell and tube heat exchanger, because of the