Thermal diffusivity/Momentum diffusivity
Thermal diffusivity x Momentum
Thermal diffusivity x Mass diffusivity
Mass diffusivity x Momentum diffusivity
✅ The correct answer is option A.
Heat Transfer MCQs
Hot water (0.01 m³ /min) enters the tube side of a counter current shell and tube heat exchanger at 80°C and leaves at 50°C. Cold oil (0.05 m³/min) of density 800 kg/m³ and specific heat of 2 kJ/kg.K enters at 20°C. The log mean temperature difference in °C is approximately
32
37
45
50
✅ The correct answer is option A.
Use of transverse baffles in a shell and tube heat exchanger is done to increase the
Rate of heat transfer
Flow velocity
Turbulence of shell side fluid
All of the above
✅ The correct answer is option D.
LMTD can’t be used as such without a correction factor for the
Multipass heat exchanger
Baffled heat exchanger
Condensation of mixed vapour in a condenser
All of the above
✅ The correct answer is option D.
As the difference between the wall temperature and bulk temperature increases, the boiling heat transfer co-efficient
Continues to increase
Continues to decrease
Goes through a minimum
Goes through a maximum
✅ The correct answer is option C.
For large heat transfer area requirement, shell and tube heat exchanger is preferred, because it
Occupies smaller space
Is more economical
Is easy to operate and maintain
All of the above
✅ The correct answer is option D.
The ratio of the total emissive power to the absorptivity for all bodies is same at ther-mal equilibrium. This is __________ law.
Kirchoffs
Planck’s
Wien’s displacement
Stefan-Boltzman
✅ The correct answer is option A.
Reynold’s analogy states that
Nst α f
Nst α NRe
NNu α f
NRe α f
✅ The correct answer is option A.
In the equation Q = UAΔt; Δt is
Geometric mean temperature difference
Arithmetic mean temperature difference
Logarithmic mean temperature difference
The difference of average bulk temperatures of hot and cold fluids
✅ The correct answer is option C.
In case of heat flow by conduction for a cylindrical body with an internal heat source, the nature of temperature distribution is
Linear
Hyperbolic
Parabolic
None of these
✅ The correct answer is option C.