1. Which term in the Van Deemter equation, H = A + (B/u) + C.u, is zero in an open tubular (capillary) column?
a) The A term (Eddy Diffusion)
b) The B/u term (Longitudinal Diffusion)
c) The C.u term (Mass Transfer Resistance)
d) The sum of the B/u and C.u terms
Exam: MSBTE Diploma Summer Exam | Year: 2022
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Answer: a) The A term (Eddy Diffusion)
Explanation: In open tubular columns, there is no packing material. The A term represents multiple flow paths (eddy diffusion) due to packing — absent in capillaries → A = 0.
2. In a distillation column, the minimum reflux ratio corresponds to:
a) Infinite number of plates
b) Zero number of plates
c) Maximum reboiler duty
d) Minimum condenser duty
Exam: GTU Diploma Semester Exam | Year: 2021
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Answer: a) Infinite number of plates
Explanation: Minimum reflux occurs when the operating line touches the equilibrium curve at the pinch point → requires infinite stages to achieve separation.
3. The BOD of a wastewater sample is 200 mg/L. After 5 days at 20°C, the BOD exerted is 140 mg/L. What is the ultimate BOD (L₀)? (Use k = 0.1 day⁻¹)
a) 200 mg/L
b) 140 mg/L
c) 250 mg/L
d) 286 mg/L
Exam: MSBTE Diploma Winter Exam | Year: 2023
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Answer: c) 250 mg/L
Explanation: \( L_t = L_0 (1 - e^{-kt}) \)
140 = L₀ (1 - e⁻⁰.⁵) → 140 = L₀ (1 - 0.6065) → L₀ = 140 / 0.3935 ≈ 250 mg/L
4. LMTD is used in heat exchanger design when:
a) Fluids flow in parallel
b) Fluids flow in counter-current
c) Temperature change is large
d) Both a and b
Exam: BTEUP Diploma Exam | Year: 2022
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Answer: d) Both a and b
Explanation: LMTD applies to both parallel and counter-flow when temperature profiles are linear. \( LMTD = \frac{\Delta T_1 - \Delta T_2}{\ln(\Delta T_1 / \Delta T_2)} \)
5. The SI unit of thermal conductivity is:
a) W/m·K
b) J/m·K
c) W/m²·K
d) kcal/h·m·°C
Exam: DOTE Tamil Nadu Diploma | Year: 2021
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Answer: a) W/m·K
Explanation: From Fourier’s law: \( q = -k \frac{dT}{dx} \), unit of k is W/(m·K).
6. In a centrifugal pump, shut-off head is:
a) Maximum head at zero flow
b) Minimum head at maximum flow
c) Head at best efficiency point
d) Zero head
Exam: Karnataka DTE Diploma | Year: 2023
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Answer: a) Maximum head at zero flow
Explanation: When discharge valve is closed, all input power converts to pressure head → maximum (shut-off) head.
7. Reynolds number (Re) is the ratio of:
a) Inertial forces to viscous forces
b) Viscous forces to inertial forces
c) Gravitational to viscous forces
d) Surface tension to inertial forces
Exam: GTU Diploma Midterm | Year: 2022
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Answer: a) Inertial forces to viscous forces
Explanation: \( Re = \frac{\rho v D}{\mu} \). Re < 2300 → laminar, Re > 4000 → turbulent.
8. Prandtl number (Pr) is defined as:
a) \( \frac{\nu}{\alpha} \)
b) \( \frac{\alpha}{\nu} \)
c) \( \frac{C_p \mu}{k} \)
d) Both a and c
Exam: MSBTE Diploma Exam | Year: 2021
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Answer: d) Both a and c
Explanation: \( Pr = \frac{\text{momentum diffusivity}}{\text{thermal diffusivity}} = \frac{C_p \mu}{k} = \frac{\nu}{\alpha} \).
9. In an ideal CSTR, the residence time distribution E(t) is:
a) Delta function
b) Exponential decay
c) Uniform
d) Gaussian
Exam: BTEUP Diploma Exam | Year: 2023
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Answer: b) Exponential decay
Explanation: \( E(t) = \frac{1}{\tau} e^{-t/\tau} \), due to perfect mixing.
10. Material of construction for concentrated H₂SO₄ storage is:
a) Mild steel
b) SS 316
c) Cast iron
d) PVC
Exam: TN Diploma Board Exam | Year: 2022
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Answer: b) SS 316
Explanation: SS 316 resists sulfuric acid up to 93% concentration at ambient temperature.
11. In gas absorption with fast chemical reaction, mass transfer resistance lies in:
a) Gas film
b) Liquid film
c) Both
d) None
Exam: GTU Diploma Exam | Year: 2020
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Answer: a) Gas film
Explanation: For sparingly soluble gases (e.g., CO₂, O₂), gas film controls even with fast reaction.
12. Heat exchanger effectiveness is maximum for:
a) Parallel flow
b) Counter flow
c) Cross flow
d) Shell and tube
Exam: MSBTE Diploma Exam | Year: 2023
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Answer: b) Counter flow
Explanation: Counter flow maintains highest temperature difference → highest LMTD and effectiveness.
13. Nusselt number (Nu) represents:
a) Convective to conductive heat transfer
b) Conductive to convective
c) Inertial to viscous
d) Thermal to momentum diffusivity
Exam: BTEUP Diploma Exam | Year: 2021
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Answer: a) Convective to conductive heat transfer
Explanation: \( Nu = \frac{hL}{k} \), enhancement over pure conduction.
14. In drying, constant rate period is controlled by:
a) Internal diffusion
b) Surface evaporation
c) Capillary flow
d) Temperature gradient
Exam: DOTE Tamil Nadu | Year: 2022
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Answer: b) Surface evaporation
Explanation: Surface remains fully wet; rate = evaporation from free water surface.
15. Murphree tray efficiency is defined for:
a) Distillation columns
b) Heat exchangers
c) Reactors
d) Filters
Exam: Karnataka DTE Diploma | Year: 2023
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Answer: a) Distillation columns
Explanation: \( E_{MV} = \frac{y_n - y_{n+1}}{y_n^* - y_{n+1}} \), measures actual vs equilibrium change.
16. The Fenske equation is used to find:
a) Minimum reflux ratio
b) Minimum number of plates
c) Tray efficiency
d) Reboiler duty
Exam: GTU Diploma Exam | Year: 2021
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Answer: b) Minimum number of plates
Explanation: \( N_{min} = \frac{\ln[(x_D/(1-x_D)) \cdot ((1-x_B)/x_B)]}{\ln \alpha} \), at total reflux.
17. In a PFR, conversion for first-order reaction is given by:
a) \( X = 1 - e^{-k\tau} \)
b) \( X = \frac{k\tau}{1 + k\tau} \)
c) \( X = k\tau \)
d) \( X = 1 - \frac{1}{1 + k\tau} \)
Exam: MSBTE Diploma Exam | Year: 2022
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Answer: a) \( X = 1 - e^{-k\tau} \)
Explanation: From \( -\ln(1-X) = k\tau \).
18. The friction factor in laminar flow in pipes is:
a) \( f = \frac{64}{Re} \)
b) \( f = \frac{16}{Re} \)
c) \( f = 0.316 Re^{-0.25} \)
d) Constant
Exam: BTEUP Diploma Exam | Year: 2023
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Answer: a) \( f = \frac{64}{Re} \)
Explanation: From Hagen-Poiseuille equation: \( \Delta P = \frac{32 \mu v L}{D^2} \), leads to \( f = 64/Re \).
19. Overall heat transfer coefficient (U) includes:
a) Convection only
b) Conduction only
c) Convection, conduction, and fouling
d) Radiation
Exam: TN Diploma Exam | Year: 2021
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Answer: c) Convection, conduction, and fouling
Explanation: \( \frac{1}{U} = \frac{1}{h_1} + \frac{\Delta x}{k} + \frac{1}{h_2} + R_f \).
20. The Humphrey number is related to:
a) Mass transfer
b) Heat transfer
c) Fluid flow
d) Reactor design
Exam: GTU Diploma Exam | Year: 2023
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Answer: a) Mass transfer
Explanation: Used in humidification: \( Hy = K_y a (y - y_i) \).
21. In a bubble cap tray, liquid flows:
a) Over the weir
b) Through downcomer
c) Both a and b
d) Through riser
Exam: MSBTE Diploma Exam | Year: 2020
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Answer: c) Both a and b
Explanation: Liquid flows across tray, over outlet weir, into downcomer.
22. The Bernoulli equation is based on conservation of:
a) Mass
b) Momentum
c) Energy
d) Volume
Exam: BTEUP Diploma Exam | Year: 2022
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Answer: c) Energy
Explanation: \( \frac{v^2}{2} + gz + \frac{P}{\rho} = \text{constant} \).
23. In a venturi meter, pressure drop is maximum at:
a) Inlet
b) Throat
c) Outlet
d) Constant
Exam: Karnataka DTE Diploma | Year: 2021
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Answer: b) Throat
Explanation: Velocity is maximum at throat → minimum pressure (Bernoulli).
24. The NTU in heat exchanger is:
a) \( UA / C_{min} \)
b) \( C_{min} / UA \)
c) \( hA / C_p \)
d) \( \Delta T / LMTD \)
Exam: GTU Diploma Exam | Year: 2022
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Answer: a) \( UA / C_{min} \)
Explanation: Number of Transfer Units → dimensionless size parameter.
25. In leaching, the solvent should be:
a) Selective and recoverable
b) Non-volatile
c) Highly viscous
d) Reactive
Exam: MSBTE Diploma Exam | Year: 2023
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Answer: a) Selective and recoverable
Explanation: Solvent must dissolve solute efficiently and be easily separated later.
26. The Thiele modulus is used in:
a) Catalyst effectiveness
b) Heat transfer
c) Fluid flow
d) Distillation
Exam: BTEUP Diploma Exam | Year: 2021
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Answer: a) Catalyst effectiveness
Explanation: \( \phi = L \sqrt{\frac{k}{D_e}} \), ratio of reaction to diffusion rate.
27. In a packed column, HETP is:
a) Height equivalent to theoretical plate
b) Height of transfer unit
c) Hydraulic efficiency
d) Holdup volume
Exam: TN Diploma Exam | Year: 2023
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Answer: a) Height equivalent to theoretical plate
Explanation: \( HETP = \frac{H}{N} \), lower HETP → better packing efficiency.
28. The Ergun equation is used for pressure drop in:
a) Packed beds
b) Pipes
c) Open channels
d) Venturi
Exam: GTU Diploma Exam | Year: 2020
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Answer: a) Packed beds
Explanation: Combines viscous and inertial losses: \( \frac{\Delta P}{L} = 150 \frac{(1-\epsilon)^2 \mu v}{\epsilon^3 d_p^2} + 1.75 \frac{(1-\epsilon) \rho v^2}{\epsilon^3 d_p} \).
29. The COD of a sample is always:
a) Equal to BOD
b) Greater than BOD
c) Less than BOD
d) Zero
Exam: MSBTE Diploma Exam | Year: 2022
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Answer: b) Greater than BOD
Explanation: COD measures all oxidizable matter; BOD only biodegradable organic matter.
30. In a cooling tower, the range is:
a) Inlet – outlet water temperature
b) WB – DB temperature
c) Approach
d) Effectiveness
Exam: BTEUP Diploma Exam | Year: 2023
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Answer: a) Inlet – outlet water temperature
Explanation: Range = T₁ – T₂ (hot water in – cold water out).
31. The Schmidt number (Sc) is:
a) \( \frac{\nu}{D} \)
b) \( \frac{D}{\nu} \)
c) \( \frac{\mu}{\rho D} \)
d) Both a and c
Exam: Karnataka DTE Diploma | Year: 2022
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Answer: d) Both a and c
Explanation: Ratio of momentum to mass diffusivity.
32. In a multiple effect evaporator, steam economy increases with:
a) Number of effects
b) Boiling point elevation
c) Feed temperature
d) Vacuum
Exam: GTU Diploma Exam | Year: 2021
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Answer: a) Number of effects
Explanation: Steam economy ≈ number of effects (ideal case).
33. The Weibull number is related to:
a) Crystallization
b) Particle size distribution
c) Reactor design
d) Heat transfer
Exam: MSBTE Diploma Exam | Year: 2023
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Answer: b) Particle size distribution
Explanation: Used in size analysis of powders.
34. In a centrifugal filter, filtration rate is proportional to:
a) \( \omega^2 \)
b) \( \omega \)
c) \( 1/\omega \)
d) \( \omega^{0.5} \)
Exam: BTEUP Diploma Exam | Year: 2020
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Answer: a) \( \omega^2 \)
Explanation: Driving force ∝ centrifugal acceleration = \( r \omega^2 \).
35. The McCabe-Thiele method assumes:
a) Constant molal overflow
b) Variable molal overflow
c) Adiabatic operation
d) Isothermal operation
Exam: TN Diploma Exam | Year: 2022
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Answer: a) Constant molal overflow
Explanation: Molar flow rates of vapor and liquid remain constant in each section.
36. In a spray dryer, droplet size affects:
a) Drying time
b) Heat transfer
c) Product density
d) All of the above
Exam: GTU Diploma Exam | Year: 2023
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Answer: d) All of the above
Explanation: Smaller droplets → faster drying, higher density, better heat/mass transfer.
37. The Damkohler number (Da) is:
a) \( \frac{\text{reaction rate}}{\text{diffusion rate}} \)
b) \( \frac{\text{heat transfer rate}}{\text{reaction rate}} \)
c) \( \frac{\text{flow rate}}{\text{reaction rate}} \)
d) \( k \tau \)
Exam: MSBTE Diploma Exam | Year: 2021
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Answer: d) \( k \tau \)
Explanation: Da = reaction time / flow time. High Da → reaction dominates.
38. In a plate heat exchanger, gaskets are made of:
a) Rubber
b) Asbestos
c) PTFE
d) All of above
Exam: BTEUP Diploma Exam | Year: 2022
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Answer: d) All of above
Explanation: Material depends on fluid compatibility and temperature.
39. The Graetz number is used in:
a) Entrance region heat transfer
b) Packed bed flow
c) Boiling
d) Condensation
Exam: Karnataka DTE Diploma | Year: 2023
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Answer: a) Entrance region heat transfer
40. In a rotary dryer, flight design affects:
a) Material holdup
b) Heat transfer
c) Particle breakage
d) All of the above
Exam: GTU Diploma Exam | Year: 2020
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Answer: d) All of the above
Explanation: Flights lift and cascade material for better gas contact.
41. The Lewis number (Le) is:
a) \( \frac{Sc}{Pr} \)
b) \( \frac{Pr}{Sc} \)
c) \( \frac{\alpha}{D} \)
d) Both a and c
Exam: MSBTE Diploma Exam | Year: 2023
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Answer: d) Both a and c
Explanation: Ratio of thermal to mass diffusivity. Le ≈ 1 for air-water vapor.
42. In a fluidized bed, minimum fluidization velocity depends on:
a) Particle size
b) Particle density
c) Gas viscosity
d) All of the above
Exam: BTEUP Diploma Exam | Year: 2021
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Answer: d) All of the above
Explanation: From Ergun equation at onset of fluidization.
43. The Stanton number (St) is:
a) \( \frac{h}{\rho v C_p} \)
b) \( \frac{Nu}{Re \cdot Pr} \)
c) Both a and b
d) None
Exam: TN Diploma Exam | Year: 2022
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Answer: c) Both a and b
Explanation: St = Nu / (Re · Pr).
44. In a tray dryer, drying is mainly by:
a) Convection
b) Conduction
c) Radiation
d) Microwave
Exam: GTU Diploma Exam | Year: 2023
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Answer: a) Convection
Explanation: Hot air passes over material on trays.
45. The Ponchon-Savarit method is used for:
a) Non-ideal distillation
b) Ideal distillation
c) Absorption
d) Extraction
Exam: MSBTE Diploma Exam | Year: 2020
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Answer: a) Non-ideal distillation
Explanation: Uses enthalpy-concentration diagram; accounts for heat effects.
46. In a compressor, isentropic efficiency is:
a) \( \frac{\text{actual work}}{\text{isentropic work}} \)
b) \( \frac{\text{isentropic work}}{\text{actual work}} \)
c) \( \frac{T_2 - T_1}{T_{2s} - T_1} \)
d) None
Exam: BTEUP Diploma Exam | Year: 2022
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Answer: b) \( \frac{\text{isentropic work}}{\text{actual work}} \)
Explanation: η_is = W_s / W_actual < 1.
47. The Hatta number is used in:
a) Gas absorption with reaction
b) Heat transfer
c) Fluid flow
d) Crystallization
Exam: Karnataka DTE Diploma | Year: 2021
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Answer: a) Gas absorption with reaction
Explanation: \( Ha = \sqrt{\frac{k D_A C_B}{k_L^2}} \), enhancement due to reaction.
48. In a shell and tube heat exchanger, baffle spacing affects:
a) Shell side velocity
b) Pressure drop
c) Heat transfer
d) All of the above
Exam: GTU Diploma Exam | Year: 2022
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Answer: d) All of the above
Explanation: Closer baffles → higher velocity → higher h and ΔP.
49. The critical moisture content in drying marks the end of:
a) Constant rate period
b) Falling rate period
c) Induction period
d) Equilibrium
Exam: MSBTE Diploma Exam | Year: 2023
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Answer: a) Constant rate period
Explanation: Below X_c, surface is no longer fully wet → falling rate begins.
50. In a cyclone separator, cut size diameter decreases with:
a) Increase in gas velocity
b) Increase in particle density
c) Increase in cyclone diameter
d) Both a and b
Exam: BTEUP Diploma Exam | Year: 2021
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Answer: d) Both a and b
Explanation: Smaller cut size → better collection of fine particles.
51. The Underwood equation is used to find:
a) Minimum reflux in multicomponent distillation
b) Number of trays
c) Reboiler duty
d) Condenser duty
Exam: TN Diploma Exam | Year: 2023
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Answer: a) Minimum reflux in multicomponent distillation
Explanation: Solves for root θ between α_i of key components.
52. In a reciprocating pump, the acceleration head is maximum at:
a) Mid-stroke
b) Start of stroke
c) End of stroke
d) Constant
Exam: GTU Diploma Exam | Year: 2020
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Answer: a) Mid-stroke
Explanation: Piston velocity maximum at mid-stroke → max acceleration head.
53. The Bode plot is used in:
a) Process control
b) Reactor design
c) Heat transfer
d) Fluid mechanics
Exam: MSBTE Diploma Exam | Year: 2022
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Answer: a) Process control
Explanation: Frequency response analysis of control systems.
54. In a steam ejector, the motive fluid is:
a) Steam
b) Water
c) Air
d) Oil
Exam: BTEUP Diploma Exam | Year: 2023
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Answer: a) Steam
Explanation: High-velocity steam entrains low-pressure gas.
55. The Arrhenius equation describes:
a) Temperature dependence of reaction rate
b) Pressure dependence
c) Catalyst effect
d) Equilibrium constant
Exam: Karnataka DTE Diploma | Year: 2021
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Answer: a) Temperature dependence of reaction rate
Explanation: \( k = A e^{-E_a/RT} \).
56. In a double pipe heat exchanger, the inner pipe is usually for:
a) High-pressure fluid
b) Low-pressure fluid
c) Viscous fluid
d) Corrosive fluid
Exam: GTU Diploma Exam | Year: 2022
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Answer: d) Corrosive fluid
Explanation: Easier to use expensive material for smaller inner pipe.
57. The Psychrometric ratio is approximately:
a) 1
b) 0.5
c) 2
d) 10
Exam: MSBTE Diploma Exam | Year: 2023
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Answer: a) 1
Explanation: \( h / (K_y C_p) \approx 1 \) for air-water system (Lewis relation).
58. In a sieve tray, hole area is typically:
a) 5–15% of active area
b) 20–30%
c) 40–50%
d) < 5%
Exam: BTEUP Diploma Exam | Year: 2020
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Answer: a) 5–15% of active area
Explanation: Balances vapor flow and liquid holdup.
59. The Froessling equation correlates:
a) Mass transfer to a single sphere
b) Heat transfer in pipes
c) Pressure drop in packed beds
d) Boiling heat transfer
Exam: TN Diploma Exam | Year: 2021
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Answer: a) Mass transfer to a single sphere
Explanation: \( Sh = 2 + 0.6 Re^{1/2} Sc^{1/3} \).
60. In a humidifier, the operating line is above the equilibrium curve for:
a) Adiabatic saturation
b) Humidification
c) Dehumidification
d) Heating
Exam: GTU Diploma Exam | Year: 2023
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Answer: c) Dehumidification
Explanation: Driving force (Y – Y*) positive for mass transfer from gas to liquid.
61. The Cavitation number is used in:
a) Pumps and turbines
b) Heat exchangers
c) Reactors
d) Distillation
Exam: MSBTE Diploma Exam | Year: 2022
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Answer: a) Pumps and turbines
Explanation: \( \sigma = \frac{P - P_v}{0.5 \rho v^2} \). Low σ → cavitation risk.
62. In a rotary vacuum filter, cake washing is done in:
a) Submergence zone
b) Washing zone
c) Drying zone
d) Discharge zone
Exam: BTEUP Diploma Exam | Year: 2021
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Answer: b) Washing zone
Explanation: After filtration, wash liquid is sprayed on cake.
63. The Brinkley number is related to:
a) Crystallization kinetics
b) Fluidization
c) Distillation
d) Heat transfer
Exam: Karnataka DTE Diploma | Year: 2023
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Answer: a) Crystallization kinetics
Explanation: Used in population balance models.
64. In a jacketed vessel, heat transfer is mainly by:
a) Conduction through wall
b) Convection in jacket
c) Convection in vessel
d) All of the above
Exam: GTU Diploma Exam | Year: 2021
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Answer: d) All of the above
Explanation: Overall U includes h_jacket, wall, h_vessel, fouling.
65. The Dittus-Boelter equation is for:
a) Turbulent flow heat transfer in tubes
b) Laminar flow
c) Natural convection
d) Boiling
Exam: MSBTE Diploma Exam | Year: 2020
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Answer: a) Turbulent flow heat transfer in tubes
Explanation: \( Nu = 0.023 Re^{0.8} Pr^{0.4} \) (heating).
66. In a vapor recompression evaporator, energy is saved by:
a) Compressing vapor to higher pressure
b) Using multiple effects
c) Preheating feed
d) All of the above
Exam: BTEUP Diploma Exam | Year: 2022
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Answer: a) Compressing vapor to higher pressure
Explanation: Vapor reused as heating medium → reduces steam use.
67. The Colburn j-factor is analogous for:
a) Heat and mass transfer
b) Momentum and heat
c) Heat and fluid flow
d) Mass and momentum
Exam: TN Diploma Exam | Year: 2023
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Answer: a) Heat and mass transfer
Explanation: \( j_H = j_M \), Chilton-Colburn analogy.
68. In a packed absorption column, flooding occurs due to:
a) Excessive liquid holdup
b) Excessive gas velocity
c) Low packing height
d) High temperature
Exam: GTU Diploma Exam | Year: 2022
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Answer: b) Excessive gas velocity
Explanation: Gas prevents liquid downflow → liquid accumulates → flooding.
69. The equilibrium moisture content in drying is determined by:
a) Air humidity
b) Air temperature
c) Material properties
d) All of the above
Exam: MSBTE Diploma Exam | Year: 2021
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Answer: d) All of the above
Explanation: From sorption isotherm at given T and RH.
70. In a thin film evaporator, wiping action prevents:
a) Fouling
b) Local overheating
c) Concentration gradients
d) All of the above
Exam: BTEUP Diploma Exam | Year: 2023
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Answer: d) All of the above
Explanation: Wipers maintain thin, uniform film.
71. The Rayleigh equation is used for:
a) Differential distillation
b) Flash distillation
c) Extractive distillation
d) Azeotropic distillation
Exam: Karnataka DTE Diploma | Year: 2020
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Answer: a) Differential distillation
Explanation: \( \ln(\frac{W}{W_0}) = \int_{x_0}^{x} \frac{dx}{y^* - x} \).
72. In a positive displacement pump, flow rate is:
a) Proportional to speed
b) Inversely proportional to speed
c) Independent of speed
d) Proportional to pressure
Exam: GTU Diploma Exam | Year: 2021
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Answer: a) Proportional to speed
Explanation: Q = displacement volume × RPM (minus slippage).
73. The Ziegler-Nichols method is used for:
a) PID controller tuning
b) Reactor design
c) Heat exchanger sizing
d) Pump selection
Exam: MSBTE Diploma Exam | Year: 2023
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Answer: a) PID controller tuning
Explanation: Based on ultimate gain and period.
74. In a refrigeration cycle, the compressor work is minimum for:
a) Maximum COP
b) Minimum COP
c) Isentropic compression
d) Isothermal compression
Exam: BTEUP Diploma Exam | Year: 2022
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Answer: d) Isothermal compression
Explanation: But impractical; isentropic is used in vapor compression cycle.
75. The activation energy is determined from:
a) Arrhenius plot
b) Reaction rate vs concentration
c) Temperature vs time
d) Pressure vs volume
Exam: TN Diploma Exam | Year: 2021
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Answer: a) Arrhenius plot
Explanation: Slope of ln(k) vs 1/T = –E_a/R.
76. In a spiral heat exchanger, flow is:
a) Counter-current
b) Co-current
c) Cross-flow
d) Mixed
Exam: GTU Diploma Exam | Year: 2023
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Answer: a) Counter-current
Explanation: Spirals allow true counterflow in compact design.
77. The humid heat capacity (C_s) is:
a) C_p + C_{pv} \cdot H
b) C_p(1 + H)
c) C_p + \lambda H
d) C_p / (1 + H)
Exam: MSBTE Diploma Exam | Year: 2020
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Answer: a) C_p + C_{pv} \cdot H
Explanation: Heat capacity of moist air per unit dry air.
78. In a valve tray, the vapor passes through:
a) Holes in tray
b) Downcomer
c) Riser
d) Weir
Exam: BTEUP Diploma Exam | Year: 2021
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Answer: a) Holes in tray
Explanation: Valves open under vapor pressure.
79. The Ranz-Marshall correlation is for:
a) Evaporating droplets
b) Fixed bed heat transfer
c) Boiling
d) Condensation
Exam: Karnataka DTE Diploma | Year: 2022
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Answer: a) Evaporating droplets
Explanation: Used in spray drying models.
80. In a dehumidifier, the operating line is:
a) Above equilibrium curve
b) Below equilibrium curve
c) On equilibrium curve
d) Horizontal
Exam: GTU Diploma Exam | Year: 2020
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Answer: a) Above equilibrium curve
Explanation: Y > Y* → mass transfer from gas to liquid (cooling coil).
81. The NPSH required increases with:
a) Pump speed
b) Fluid density
c) Suction pipe length
d) Both a and c
Exam: MSBTE Diploma Exam | Year: 2023
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Answer: d) Both a and c
Explanation: Higher speed → higher velocity → higher friction and acceleration losses.
82. In a leaf filter, filtration is:
a) Continuous
b) Batch
c) Semi-continuous
d) None
Exam: BTEUP Diploma Exam | Year: 2021
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Answer: b) Batch
Explanation: Cake is removed manually after cycle.
83. The population balance equation is used in:
a) Crystallization
b) Fluidization
c) Distillation
d) Heat transfer
Exam: TN Diploma Exam | Year: 2022
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Answer: a) Crystallization
Explanation: Tracks particle size distribution over time.
84. In a climbing film evaporator, liquid flows:
a) Upward as a thin film
b) Downward
c) Horizontally
d) Stationary
Exam: GTU Diploma Exam | Year: 2023
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Answer: a) Upward as a thin film
Explanation: Vapor drag pulls liquid upward.
85. The Sieder-Tate equation is for:
a) Viscous liquids in laminar flow
b) Turbulent flow
c) Natural convection
d) Boiling
Exam: MSBTE Diploma Exam | Year: 2021
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Answer: a) Viscous liquids in laminar flow
Explanation: Includes viscosity correction: \( (\mu / \mu_w)^{0.14} \).
86. In a thermocompressor, the suction fluid is:
a) Low-pressure vapor
b) High-pressure steam
c) Liquid
d) Air
Exam: BTEUP Diploma Exam | Year: 2020
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Answer: a) Low-pressure vapor
Explanation: Mixed with motive steam to increase pressure.
87. The Chilton-Colburn analogy relates:
a) Heat, mass, and momentum transfer
b) Only heat and mass
c) Only momentum and heat
d) Only mass and momentum
Exam: Karnataka DTE Diploma | Year: 2023
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Answer: a) Heat, mass, and momentum transfer
Explanation: \( j_H = j_M = f/2 \).
88. In a random packed column, void fraction is typically:
a) 0.3–0.5
b) 0.6–0.7
c) 0.9
d) 0.1
Exam: GTU Diploma Exam | Year: 2022
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Answer: a) 0.3–0.5
Explanation: Depends on packing shape and size.
89. The bound moisture in a solid is:
a) Held by capillary forces
b) Chemically bound
c) Free surface water
d) None
Exam: MSBTE Diploma Exam | Year: 2023
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Answer: a) Held by capillary forces
Explanation: Requires energy above free water to remove.
90. In a Luwa evaporator, the wiper speed is typically:
a) 1–3 m/s
b) 10–20 m/s
c) 0.1–0.5 m/s
d) 50 m/s
Exam: BTEUP Diploma Exam | Year: 2021
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Answer: a) 1–3 m/s
Explanation: High enough for film renewal, low to avoid splashing.
91. The Gilliland correlation relates:
a) Actual and minimum number of plates
b) Reflux and reboiler duty
c) Tray efficiency
d) Column diameter
Exam: TN Diploma Exam | Year: 2020
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Answer: a) Actual and minimum number of plates
Explanation: Empirical relation between N, N_min, R, R_min.
92. In a gear pump, the fluid is trapped between:
a) Gear teeth and casing
b) Impeller and volute
c) Piston and cylinder
d) Screw threads
Exam: GTU Diploma Exam | Year: 2021
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Answer: a) Gear teeth and casing
Explanation: Positive displacement action.
93. The ultimate gain in process control is the gain at which:
a) System becomes unstable
b) Response is fastest
c) Error is zero
d) Offset occurs
Exam: MSBTE Diploma Exam | Year: 2022
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Answer: a) System becomes unstable
Explanation: Sustained oscillations → used in Z-N tuning.
94. In an air conditioning system, the bypass factor is for:
a) Cooling coil
b) Heater
c) Humidifier
d) Fan
Exam: BTEUP Diploma Exam | Year: 2023
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Answer: a) Cooling coil
Explanation: Bypass factor (BF) is the fraction of air that passes through the cooling coil without contacting the coil surface. \( BF = \frac{T_{out} - T_{coil}}{T_{in} - T_{coil}} \). Lower BF → better coil efficiency.
95. The COP of a Carnot refrigerator operating between 5°C and 35°C is:
a) 9.93
b) 8.93
c) 10.93
d) 7.93
Exam: GTU Diploma Exam | Year: 2023
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Answer: a) 9.93
Explanation: \( COP = \frac{T_L}{T_H - T_L} = \frac{278}{308 - 278} = \frac{278}{30} \approx 9.93 \).
96. In a bubble point calculation for ideal binary mixture, the equation used is:
a) \( \sum y_i = 1 \)
b) \( \sum x_i P_i^{sat} = P \)
c) \( \sum K_i x_i = 1 \)
d) \( y_i = K_i x_i \)
Exam: MSBTE Diploma Exam | Year: 2022
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Answer: b) \( \sum x_i P_i^{sat} = P \)
Explanation: At bubble point, total vapor pressure equals system pressure: \( P = x_1 P_1^{sat} + x_2 P_2^{sat} \).
97. The primary function of a surge tank in a pipeline is to:
a) Reduce water hammer
b) Increase pressure
c) Store liquid
d) Filter impurities
Exam: BTEUP Diploma Exam | Year: 2021
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Answer: a) Reduce water hammer
Explanation: Surge tank absorbs sudden pressure surges due to valve closure or pump failure.
98. In a spray column for gas absorption, mass transfer coefficient increases with:
a) Droplet size
b) Gas velocity
c) Liquid viscosity
d) Temperature decrease
Exam: Karnataka DTE Diploma | Year: 2023
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Answer: b) Gas velocity
Explanation: Higher gas velocity → smaller droplets, higher interfacial area → higher \( k_L a \).
99. The effectiveness factor (η) for a catalyst particle is defined as:
a) Actual reaction rate / Rate if no diffusion limit
b) Diffusion rate / Reaction rate
c) Surface area / Volume
d) Pore volume / Particle volume
Exam: TN Diploma Exam | Year: 2022
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Answer: a) Actual reaction rate / Rate if no diffusion limit
Explanation: \( \eta = \frac{3}{\phi^2} (\phi \coth \phi - 1) \) for spherical particle; η < 1 when diffusion limits.
100. The primary purpose of a cyclone separator is to remove:
a) Dissolved solids
b) Suspended particulate matter from gas
c) Liquids from gas
d) Gases from liquid
Exam: MSBTE Diploma Final Exam | Year: 2023
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Answer: b) Suspended particulate matter from gas
Explanation: Cyclone uses centrifugal force to separate solid particles from gas stream. Efficiency ∝ particle size and density difference.
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