20.8
40.8
40.4
20.4
✅ The correct answer is option B.
Engineering MCQs
For gases, the thermal conductivity increases with temperature rise. For liquids, with increase in concentration, its thermal conductivity generally
Decreases
Increases
Remains unchanged
Increases exponentially
✅ The correct answer is option A.
If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows __________ law.
Hyperbolic
Parabolic
Linear
Logarithmic
✅ The correct answer is option C.
Which of the following is the most widely used heat insulating material for pipelines carrying steam?
Tar dolomite bricks followed by asbestos
Fireclay refractory followed by aluminium sheet
Cotton followed by aluminium foil
85% magnesia cement and glass wool
✅ The correct answer is option D.
Planck’s distribution law is valid for __________ bodies.
Black
White
Coloured
All of the above
✅ The correct answer is option C.
In a co-current double pipe heat exchanger used for condensing saturated steam over the inner tube, if the entrance and exit conditions of the coolant are interchanged, then the rate of condensation will
Increase
Decrease
Remain unchanged
Either increase or decrease; depends on the coolant flow rate
✅ The correct answer is option C.
With increase in porosity, the thermal conductivity of a solid substance
Increases
Decreases
Remains unchanged
May increase or decrease; depends on the solid
✅ The correct answer is option B.
In a heat exchanger, floating head is provided to
Facilitate cleaning of the exchanger
Increase the heat transfer area
Relieve stresses caused by thermal expansion
Increase log mean temperature gradient
✅ The correct answer is option C.
In a liquid-liquid heat exchanger, for the same process temperature, the ratio of the LMTD in parallel flow to the LMTD in counter flow is always
< 1
> 1
1
∞
✅ The correct answer is option A.
Vacuum is generally maintained in the vapour space of an evaporator mainly to
Get economical temperature difference by using moderate pressure steam
Facilitate forward feeding in multiple effect evaporation
Concentrate heat sensitive materials
Achieve very high concentration of the final product
✅ The correct answer is option A.