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Question 1. In a Bingham plastic fluid, flow begins only when the applied shear stress exceeds a critical value called the: A) Viscosity coefficient B) Yield stress C) Consistency index D) Flow index Answer: B Explanation: Bingham plastics behave as a rigid body until the shear stress surpasses the yield stress; thereafter they flow with a linear relationship between shear stress and shear rate. Question 2. The Power‑Law model for non‑Newtonian fluids is expressed as τ = K·γ˙ⁿ. Which parameter determines whether the fluid is shear‑thinning? A) K (consistency) B) τ (shear stress) C) n (flow behavior index) D) γ˙ (shear rate) Answer: C Explanation: When n < 1 the fluid exhibits shear‑thinning (pseudoplastic) behavior; n > 1 indicates shear‑thickening (dilatant). Question 3. In the Casson model, the shear stress–shear rate relationship includes a term √τ₀. The model is most appropriate for describing: A) Polymer melts B) Blood flow C) Molten glass
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D) Oil sands Answer: B Explanation: The Casson model captures the yield stress and shear‑thinning behavior of blood, a suspension of cells in plasma. Question 4. For laminar flow of a Newtonian fluid in a helical coil, the Dean number (De) is defined as De = Re·(d/R)¹ᐟ². Increasing the coil curvature radius R will: A) Increase De, promoting secondary flow B) Decrease De, reducing secondary flow C) Not affect De D) Reverse flow direction Answer: B Explanation: De is proportional to (d/R)¹ᐟ²; larger R reduces curvature effects, thus lowering De and weakening Dean vortices. Question 5. In a porous medium, Darcy’s law relates volumetric flow rate to pressure drop. Which additional term must be added to account for non‑Newtonian behavior? A) Reynolds number B) Viscosity correction factor C) Forchheimer term D) Prandtl number Answer: C Explanation: The Forchheimer term adds a quadratic velocity component to Darcy’s law, capturing inertial effects typical of non‑Newtonian and high‑velocity flows.
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D) Archimedes number Answer: D Explanation: U_mf is calculated using the Archimedes number, which incorporates particle size, density difference, and fluid properties. Question 9. For turbulent boundary layers, the velocity profile near the wall follows the “log‑law”. Which constant is typically taken as κ ≈ 0.41? A) Von Kármán constant B) Prandtl number C) Reynolds analogy factor D) Skin‑friction coefficient Answer: A Explanation: κ is the von Kármán constant used in the logarithmic law of the wall for turbulent shear flows. Question 10. The Reynolds‑averaged Navier‑Stokes (RANS) equations require closure models. The k‑ε model introduces two extra transport equations for: A) Turbulent viscosity and pressure B) Turbulent kinetic energy (k) and its dissipation rate (ε) C) Turbulent shear stress and eddy diffusivity D) Turbulent Mach number and temperature Answer: B Explanation: The k‑ε model solves for k and ε to close the RANS equations, providing estimates of turbulent viscosity.
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Question 11. In the effectiveness‑NTU method, the number of transfer units (NTU) for a counter‑flow heat exchanger is given by: A) NTU = – ln(1‑ε) B) NTU = ε/(1‑ε) C) NTU = (1‑ε)/ε D) NTU = (C_min/C_max)·ln[(1‑ε·C_min/C_max)/(1‑ε)] Answer: D Explanation: For counter‑flow exchangers, NTU = (C_min/C_max)·ln[(1‑ε·C_min/C_max)/(1‑ε)], accounting for the heat capacity rate ratio. Question 12. The TEMA standard for shell‑and‑tube heat exchangers designates the “B” classification for: A) Straight‑tube, single pass, one shell pass B) U‑tube, one shell pass, two tube passes C) Longitudinally‑segmental tubes with multiple shell passes D) Helically‑coiled tubes with cross‑flow Answer: A Explanation: TEMA “B” denotes a basic configuration with straight tubes, single tube pass, and a single shell pass. Question 13. Fouling resistance (R_f) is added to the overall heat‑transfer coefficient calculation. Which unit correctly expresses R_f? A) W·m⁻²·K B) m²·K·W⁻¹ C) J·s⁻¹·K⁻¹
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B) Soot particles dominate radiative heat transfer C) High temperature gases emit in the infrared region D) Radiation is negligible compared to convection Answer: C Explanation: At combustion temperatures (≥1500 K), gases emit appreciable infrared radiation, contributing to heat transfer. Question 17. Psychrometric calculations require the use of the saturation vapor pressure curve. Which equation best represents the Antoine equation for water? A) log₁₀ P = A – B/(C+T) B) P = A·exp(–B/T) C) P = A·Tⁿ D) P = A·(1‑B·T) Answer: A Explanation: The Antoine equation expresses vapor pressure as log₁₀ P = A – B/(C+T), widely used for water over typical temperature ranges. Question 18. The approach temperature for a cooling tower is defined as: A) The temperature difference between inlet water and ambient air B) The temperature difference between outlet water and inlet air wet‑bulb temperature C) The temperature difference between outlet water and ambient dry‑bulb temperature D) The temperature difference between inlet water and outlet water Answer: B Explanation: Approach temperature = T_outlet water – T_inlet air wet‑bulb; a smaller approach indicates higher cooling effectiveness.
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Question 19. The Maxwell‑Stefan equations for multicomponent diffusion reduce to Fick’s law when: A) All species have equal molar volumes B) The mixture is binary and the diffusion coefficients are constant C) Pressure is constant and temperature varies D) The system is at high pressure Answer: B Explanation: In a binary mixture with constant diffusivity, the Maxwell‑Stefan equations simplify to the familiar Fick’s law form. Question 20. In a heterogeneous catalytic reaction following the Langmuir‑Hinshelwood mechanism, the rate expression typically includes: A) Only reactant concentrations B) Surface coverage terms in the denominator C) No adsorption terms D) Only a first‑order dependence on catalyst weight Answer: B Explanation: Langmuir‑Hinshelwood kinetics account for adsorption equilibria, leading to denominator terms containing (1 + K C) expressions. Question 21. The Thiele modulus (ϕ) for a first‑order reaction in a spherical catalyst pellet is defined as: A) ϕ = (k·R²/D_e)¹ᐟ² B) ϕ = k·R/D_e
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Question 24. In non‑isothermal PFR analysis, the temperature profile can exhibit multiple steady‑states (ignition/extinction) when: A) The reaction is endothermic B) The activation energy is low C) The heat removal is insufficient relative to heat generation D) The reactor operates at very low flow rates only Answer: C Explanation: Insufficient heat removal leads to thermal runaway possibilities, creating ignition and extinction points (multiple steady states). Question 25. The residence time distribution (RTD) function E(t) for a series of N equal tanks (tanks‑in‑series model) is: A) E(t) = (t/τ)ⁿ⁻¹·e^(‑t/τ) / (τ·(N‑1)!) B) E(t) = (1/τ)·e^(‑t/τ) C) E(t) = (N/τ)·(t/τ)^(N‑1)·e^(‑N·t/τ) D) E(t) = (t/τ)·e^(‑t/τ) Answer: A Explanation: For N tanks in series, E(t) = (t/τ)^(N‑1)·e^(‑t/τ) / (τ·(N‑1)!), describing the probability density of residence times. Question 26. In the dispersion model for tubular reactors, the dimensionless Peclet number (Pe) is defined as: A) Pe = u·L/D_ax B) Pe = D_ax/(u·L)
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C) Pe = u·D_ax/L² D) Pe = L·D_ax/u² Answer: A Explanation: Pe = u·L/D_ax compares convective transport to axial dispersion; high Pe indicates plug‑flow behavior. Question 27. The E‑curve in RTD analysis represents: A) Cumulative distribution of residence times B) Exit age distribution function C) Cumulative fraction of fluid that has exited the reactor D) Inlet concentration versus time Answer: C Explanation: The E‑curve (exit age distribution) integrated over time gives the fraction of fluid that has left the reactor up to that time. Question 28. In a trickle‑bed reactor, the gas‑liquid interfacial area per unit volume (a_GL) is commonly correlated with the liquid and gas superficial velocities using the Wen & Yu correlation. Which exponent is typically applied to the gas velocity? A) 0. B) 0. C) 0. D) 1. Answer: B Explanation: The Wen & Yu correlation often uses a_GL ∝ u_G^0.5·u_L^0.5, reflecting square‑root dependence on both phases.
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D) It eliminates the need for constraints Answer: B Explanation: MPC solves an optimization over the prediction horizon but only the first control move is applied; the horizon then recedes. Question 32. The Ziegler‑Nichols tuning method for a process with integrating behavior recommends: A) Setting K_i = 0 B) Using the ultimate gain and period from closed‑loop oscillations C) Tuning only the derivative term D) Applying a dead‑time compensator first Answer: B Explanation: For integrating processes, Z‑N suggests performing a closed‑loop test to find ultimate gain (K_u) and period (P_u), then applying specific formulas for PID gains. Question 33. In a Safety Instrumented System (SIS), a Safety Integrity Level (SIL) of 2 corresponds to a probability of failure on demand (PFD) between: A) 10⁻¹ to 10⁻² B) 10⁻² to 10⁻³ C) 10⁻³ to 10⁻⁴ D) 10⁻⁴ to 10⁻⁵ Answer: B Explanation: SIL 2 requires a PFD of 10⁻² to 10⁻³, indicating moderate risk reduction capability. Question 34. During a HAZOP study, a “Deviation” is defined as:
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A) A failure of a safety instrumented function B) A departure from the design intent of a process parameter C) A change in operating personnel D) An unexpected environmental event Answer: B Explanation: A deviation is any variation from the intended design condition (e.g., “No”, “More”, “Less”) that may lead to hazards. Question 35. The sizing of a pressure relief valve for a two‑phase (liquid‑vapor) discharge typically uses the Smith method, which accounts for: A) Only the vapor phase mass flow B) The liquid’s surface tension C) The ratio of liquid to vapor densities and the discharge coefficient D) The pipe roughness Answer: C Explanation: The Smith method incorporates the density ratio and a discharge coefficient to predict the required relieving area for two‑phase flow. Question 36. In a catalytic reforming unit, the primary purpose of a hydrogen recycle loop is to: A) Increase catalyst life by removing poisons B) Shift equilibrium toward dehydrogenated products C) Maintain high hydrogen partial pressure to suppress coke formation D) Cool the reactor effluent Answer: C
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B) Reduction of total reflux ratio compared to two separate columns C) Elimination of the reboiler D) Operation at atmospheric pressure only Answer: A Explanation: Dividing‑wall columns achieve simultaneous separation of ternary mixtures (or more) by creating two concurrent sections within one shell. Question 40. The Wilson activity model is most suitable for predicting phase equilibria of: A) Highly non‑ideal, strongly associating systems B) Non‑polar hydrocarbon mixtures C) Systems with large differences in molecular size D) Electrolyte solutions Answer: B Explanation: Wilson model accounts for size and energy differences in non‑polar mixtures, providing good predictions for hydrocarbon systems. Question 41. In a life‑cycle assessment (LCA), the “functional unit” is defined as: A) The total mass of raw material used B) The reference flow to which all inputs and outputs are normalized C) The total energy consumption of the process D) The monetary cost of the product Answer: B Explanation: The functional unit provides a basis for comparing environmental impacts across different systems (e.g., 1 kg of product).
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Question 42. The primary energy penalty associated with post‑combustion CO₂ capture using amine scrubbing is due to: A) The heat of reaction between CO₂ and amine B) The regeneration of the solvent requiring steam C) The compression of captured CO₂ D) The increased flue‑gas flow rate Answer: B Explanation: Solvent regeneration consumes large amounts of low‑pressure steam, representing the main energy penalty. Question 43. In Aspen HYSYS dynamic simulation, the “steady‑state” solver is replaced by a “dynamic” solver that integrates: A) Algebraic equations only B) Ordinary differential equations (ODEs) representing accumulation terms C) Partial differential equations for spatial variation D) Linearized transfer functions only Answer: B Explanation: Dynamic simulation solves ODEs that include accumulation (mass, energy) to capture transient behavior. Question 44. A random forest algorithm in process fault detection primarily uses: A) Linear regression models B) Ensemble of decision trees to improve classification accuracy C) Single neural network with back‑propagation D) Principal component analysis for dimensionality reduction only
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B) The interaction between polymer and solvent; χ < 0.5 denotes good solvent C) The viscosity of the solution D) The glass transition temperature Answer: B Explanation: χ quantifies polymer‑solvent interaction; lower χ values (<0.5) mean favorable mixing. Question 48. In a distillation column, the “Murphree vapor‑phase efficiency” is a measure of: A) The ratio of actual to theoretical number of stages on the vapor side B) The heat duty per tray C) The liquid holdup per tray D) The reflux ratio required for a given separation Answer: A Explanation: Murphree efficiency compares the actual change in vapor composition across a tray to the ideal equilibrium change. Question 49. For a binary mixture with strong azeotropy, adding an extractive solvent works because: A) The solvent forms a new azeotrope with the key component, breaking the original one B) The solvent lowers the overall system pressure C) The solvent increases the relative volatility of the components D) The solvent reduces the column diameter Answer: C
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Explanation: An extractive solvent changes relative volatilities, allowing separation without forming a new azeotrope. Question 50. The “effective diffusion coefficient” in a porous catalyst pellet accounts for: A) Only molecular diffusion B) Both molecular diffusion and Knudsen diffusion C) Only convection within pores D) Only bulk fluid diffusion Answer: B Explanation: In pores where pore size is comparable to molecular mean free path, both molecular and Knudsen diffusion contribute, yielding an effective coefficient. Question 51. In a CSTR with a first‑order irreversible reaction, the dimensionless Damköhler number (Da) is defined as: A) Da = k·τ (where τ = V/Ṽ) B) Da = τ/k C) Da = k·V·C₀ D) Da = (k·V)/C₀ Answer: A Explanation: Da = k·τ compares reaction rate to residence time; τ = reactor volume divided by volumetric flow rate. Question 52. The “critical micelle concentration” (CMC) is a property of: A) Non‑ionic solvents only B) Surfactant solutions, indicating the concentration at which micelles form
