141. Multiple effect evaporation accounts for
Steam economy
Lower operating costs
Investment economy
None of these
✅ The correct answer is option A.
Heat Transfer MCQs
142. Boiling point of a solution according to Duhring’s rule is a linear function of the __________ of water.
Boiling point (at the same pressure)
Viscosity
Density
Thermal conductivity
✅ The correct answer is option A.
143. Radiation energy is emitted by all the substances, which are above
0°K
0°C
100°C
Room temperature
✅ The correct answer is option A.
144. In a laboratory test run, the rate of drying was found to be 0.5 x 10-3 kg/m².s, when the moisture content reduced from 0.4 to 0.1 on dry basis. The critical moisture content of the material is 0.08 on a dry basis. A tray dryer is used to dry 100 kg (dry basis) of the same material under identical conditions. The surface area of the material is 0.04 m²/kg of dry solid. The time required (in seconds) to reduce the moisture content of the solids from 0.3 to 0.2 (dry basis) is
2000
4000
5000
6000
✅ The correct answer is option C.
145. The local surface conductance for laminar film condensation on vertical surface is (where, t = film thickness)
∝ t
∝ 1/t
∝ √t
Independent of ‘t’
✅ The correct answer is option B.
146. Which of the following is not concerned with the heat transfer?
Brinkman number
Stanton number
Schmidt number
Peclet number
✅ The correct answer is option C.
147. If a single tube pass heat exchanger is converted to two pass, then for the same flow rate, the pressure drop per unit length in tube side will
Increase by 1.8 times
Decrease by 22
Increase by 216
Remain unchanged
✅ The correct answer is option C.
148. In a gas-liquid shell and tube heat exchanger, the
Presence of a non-condensible gas decreases the condensing film co-efficient
Gases under high pressure are routed through the tube side, because high pressure gases are corrosive in nature
Gases to be heated/cooled is normally routed through the shell side, because the corrosion caused by the cooling water or steam condensate remain localised to the tubes
All of the above
✅ The correct answer is option D.
149. In Joule’s experiment, an insulated container contains 20 kg of water initially at 25°C. It is stirred by an agitator, which is made to turn by a slowly falling body weighing 40 kg through a height of 4 m. The process is repeated 500 times. The acceleration due to gravity is 9.8 ms⁻². Neglecting the heat capacity of agitator, the temperature of water (in °C) is
40.5
34.4
26.8
25
✅ The correct answer is option B.
150. The heat transfer co-efficient in film type condensation is __________ that for dropwise condensation.
Greater than
Lower than
Is same as
Half
✅ The correct answer is option B.