1684. Heat transfer rate described by Fourier’s law will decrease, if the __________ increases.
Thermal conductivity
Thickness
Temperature difference
Heat transfer area
✅ The correct answer is option B.
1685. Boiling point elevation of an ideal solution
Increases rapidly with temperature rise
Decreases rapidly with temperature rise
In independent of pressure
Both B and C
✅ The correct answer is option A.
1686. With increase in the distance between the heat source and the object receiving the heat, the radiation heat transfer
Decreases
Increases
Increases exponentially
Remains unaffected
✅ The correct answer is option A.
1687. The ratio of velocity head to tube side return loss in case of a multipass shell and tube heat exchanger is
2
1-Feb
4
1-Apr
✅ The correct answer is option D.
1688. The interchange factor for radiation heat transfer from surface ‘x’ to surface ‘y’ in case of an infinite parallel planes with emis-sivities εx & εy is given by
Εx + εy
Εx . εy
1/εx + 1/εy
(εx + εy)/(εx + εy – εx . εy)
✅ The correct answer is option D.
1689. With increase in temperature, the total emissivity of conductors
Increases
Decreases
Remains same
Decreases linearly
✅ The correct answer is option A.
1677. A __________ surface has the maximum thermal emissivity out of the following.
Black & smooth
Black & rough
White & smooth
White & rough
✅ The correct answer is option B.
1668. For a perfectly transparent surface (like gases), the
Absorptivity = 0
Transmissivity = 1
Reflectivity = 0
All of the above
✅ The correct answer is option B.
1671. Finned tube heat exchangers
Give larger area per tube
Use metal fins of low thermal conductivity
Facilitate very large temperature drop through tube wall
Are used for smaller heat load
✅ The correct answer is option A.
1674. Heat transfer by natural convection is enhanced in system with
High viscosity
High co-efficient of thermal expansion
Low temperature gradients
Low density change with temperature
✅ The correct answer is option B.