1439. Which of the following has the minimum absorptivity?
Aluminium foil
Coal dust
Refractory bricks
Iron plates
✅ The correct answer is option A.
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.
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.
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.
1375. Grashhoff number is given by
gD³.β.Δtρ²/μ²
gD2βΔtρ/μ²
gD2βΔtP²μ
gD³βΔtP²/μ
✅ The correct answer is option A.
1378. In a shell and tube heat exchanger, floating head is used for
Large temperature differentials
High heat transfer co-efficient
Low pressure drop
Less corrosion of tubes
✅ The correct answer is option A.
1381. Convective heat transfer, in which heat is transferred by movement of warmed matter is described by
Fourier’s law
Newton’s law of cooling
Fick’s law
None of these
✅ The correct answer is option B.
1384. Economy of an evaporator is influenced by the
Steam pressure
Feed temperature
Number of effect
Both B & C
✅ The correct answer is option D.
1387. Forced circulation evaporators are useful for the concentration of viscous, salting and scale forming liquors. Which of the following is a forced circulation evaporator?
Long vertical evaporator
Horizontal tube evaporator
Agitated film evaporator
Calenderia vertical tube evaporator
✅ The correct answer is option C.
1390. In a parallel flow heat exchanger, if the outlet temperature of hot and cold fluids are the same, then the log mean temperature difference (LMTD) is
Minimum
Maximum
Zero
Infinity
✅ The correct answer is option C.