Absorbs
Reflects
Transmits
None of these
✅ The correct answer is option C.
Engineering MCQs
Multipass heat exchangers are used
Because of simplicity of fabrication
For low heat load
To obtain higher heat transfer co-efficient and shorter tube
To reduce the pressure drop
✅ The correct answer is option C.
Which is the best tube arrangement (in a shell and tube heat exchanger) if the fluids are clean and non-fouling?
Square pitch
Triangular pitch
Diagonal square pitch
None of these
✅ The correct answer is option B.
Multiple effect evaporation is generally recommended, when the
Large scale evaporation of liquor is needed
Corrosive liquids are to be concentrated
Fuel is cheaply available
Evaporation on small scale is to be done
✅ The correct answer is option A.
Prandtl number is the reciprocal of
Thermal diffusivity/Momentum diffusivity
Thermal diffusivity x Momentum
Thermal diffusivity x Mass diffusivity
Mass diffusivity x Momentum diffusivity
✅ The correct answer is option A.
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.
Unsteady state heat conduction occurs, when
Temperature distribution is independent of time
Temperature distribution is dependent on time
Heat flows in one direction only
Three dimensional heat flow is concerned
✅ The correct answer is option B.
The thermal boundary layer at NPr > 1
Is thicker than hydrodynamic boundary layer
Is thinner than hydrodynamic boundary layer
And the hydrodynamic boundary layer are identical
Disappears
✅ The correct answer is option B.