1441. A diathermaneous substance __________ the thermal radiation completely.
Absorbs
Reflects
Transmits
None of these
✅ The correct answer is option C.
Chemical Engineering
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1442. 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.
1443. 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.
1444. 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.
1445. 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.
1446. 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.
1447. 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.
1448. 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.
1449. Condensing film co-efficient for steam on horizontal tubes ranges from 5000 to 15000 Kcal/hr.m² .°C. Condensation of vapor is carried out inside the tube in a shell and tube heat exchanger, when the
Higher condensing film co-efficient is desired
Condensate is corrosive in nature
Lower pressure drop through the exchanger is desired
Temperature of the incoming vapor is very high
✅ The correct answer is option B.
1450. A sphere of radius ‘R₁’ is enclosed in a sphere of radius ‘R₂’. The view (or shape) factor for radiative heat transfer of the outer sphere with respect to the inner sphere is
0
R₂/(R₁+R₂)
1
(R₁/R₂)2
✅ The correct answer is option B.