(ΔT)1/4
(ΔT)1/2
(ΔT)5/4
(ΔT)3/4
✅ The correct answer is option D.
Engineering MCQs
The overall heat transfer co-efficient for a shell and tube heat exchanger for clean surfaces is U0 = 400 W/m².K. The fouling factor after one year of operation is found to be hd0 = 2000 W/m².K. The overall heat transfer co-efficient at this time is
1200W/m².K
894W/m².K
333W/m².K
287 W/m².K
✅ The correct answer is option C.
For concentrating an aqueous solution of a material like anhydrous Na₂SO₄, whose solubility decreases with rise in temperature, the most suitable evaporator is a __________ evaporator.
High pressure
Vacuum
Backward feed
None of these
✅ The correct answer is option B.
When does the heat generated by fluid friction becomes appreciable compared to the heat transferred between the fluids?
At high fluid velocity
At low velocity
When fluid flows past a smooth surface
None of these
✅ The correct answer is option A.
With increase in temperature, the thermal conductivity of fresh lubricating oil
Increases
Decreases
Remains unchanged
May increase or decrease; depends on its composition
✅ The correct answer is option B.
Thermal conductivity of a conducting solid material depends upon its
Temperature
Porosity
Both A & B
Neither A nor B
✅ The correct answer is option C.
Dropwise condensation of steam on cooling surface is promoted
An oily surface
When both the steam and the tube are clean
Only in presence of air
None of these
✅ The correct answer is option A.
Prandtl number for most of dry gases is about
0.001
0.72
70
150
✅ The correct answer is option B.
The number of kg vaporised per kg of steam fed to the evaporator is defined as
Capacity
Rate of evaporation
Economy
Rate of vaporisation
✅ The correct answer is option C.
Mechanical recompression evaporation is used in the production of
Alcohol
Distilled water
Salt
Fruits jam
✅ The correct answer is option B.