> 0.75
< 0.75
< 0.50
< 0.25
✅ The correct answer is option B.
Heat Transfer MCQs
462. Which of the following accessories is provided in the vapor line of an evaporator for removing the entrained liquid?
Bleed point
Vent
Catchall
Baffle
✅ The correct answer is option C.
463. Which characteristic of a fluid is not important in deciding its route in a shell and tube heat exchanger?
Corrosiveness
Fouling characteristic
Viscosity
None of these
✅ The correct answer is option D.
464. For small temperature difference, the heat transfer rate as per Newton’s law of cooling is proportional to (where, Δt = excess temperature)
Δt
Δt²
Δt³
√Δt
✅ The correct answer is option A.
465. Double pipe heat exchangers are preferably useful, when
High viscosity liquid is to be cooled
Requirement of heat transfer area is low
Overall heat transfer co-efficient is very high
A corrosive liquid is to be heated
✅ The correct answer is option B.
466. At what value of Prandtl number, the hydrodynamic and thermal boundary layers of a fluid flowing over a heated plate will be identical?
1
< 1
> 1
None of these
✅ The correct answer is option A.
467. Three solid objects of the same material and of equal mass-a sphere, a cylinder (length = diameter) and a cube are at 500°C initially. These are dropped in a quenching bath containing a large volume of cooling oil each attaining the bath temperature eventually. The time required for 90% change in temperature is the smallest for
Cube
Cylinder
Sphere
Equal for all the three
✅ The correct answer is option A.
468. Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer can not take place
Between two bodies in physical contact with each other
Between two bodies not in physical contact with each other
From one part of a body to the another part of the same body
Both B & C
✅ The correct answer is option B.
469. The heat flux in the nucleate boiling regimes is proportional to (where, ΔT = excess temperature)
(ΔT)²
(ΔT)⁴
(ΔT)³
√(ΔT)
✅ The correct answer is option C.
470. Thermal diffusivity of a material
Has the unit m² /sec
Is defined as K/ρ . Cp
Is the ratio of thermal conductivity to thermal capacity
All of the above
✅ The correct answer is option D.