All Free Chemical Engineering MCQs with Answers
Every Chemical Engineering question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
6,983 questions · page 255 of 350
- A. Lowest in last effect
- B. Highest in last effect
- C. Same in all effects
- D. Dependent on the number of effects
Explanation: In forward feed, the liquid flows from the first effect to successive effects while the pressure and boiling temperature are progressively…
Correct answer: Lowest in last effect- A. Increases
- B. Decreases
- C. Remain same
- D. First increases upto a certain temperature and then becomes constant
Explanation: The thermal conductivity of most common liquids decreases as temperature rises, although a few liquids show exceptional behaviour over…
Correct answer: Decreases- A. Once
- B. Thrice
- C. Twice
- D. Four times
Explanation: A longitudinal baffle divides the shell into two parallel flow passages, so the shell-side fluid travels through the exchanger twice…
Correct answer: Twice5084. Conductance is given by (where, x = thickness, A = heat flow area, K = thermal conductivity.)?
- A. x/KA
- B. A/Kx
- C. K/Ax
- D. KA/x
Explanation: From the conduction relation Q = KAΔT/x, conductance is Q/ΔT = KA/x. Therefore, increasing area or conductivity increases conductance…
Correct answer: KA/x- A. All A. B. and C.
- B. Baffled heat exchanger
- C. Condensation of mixed vapour in a condenser
- D. Multipass heat exchanger
Explanation: The basic LMTD must be multiplied by a correction factor when the exchanger arrangement causes temperature crossflow or multiple passes…
Correct answer: All A. B. and C.- A. 1.5
- B. 1
- C. > 1
- D. < 1
Explanation: The Reynolds analogy gives St = f/2 when the momentum and thermal diffusivities are equal, which corresponds to Pr = 1.
Correct answer: 1- A. None of these
- B. Directly proportional to LMTD and inversely proportional to the area
- C. Varies as square of the area
- D. Varies directly as the area and the LMTD
Explanation: For a heat exchanger, the heat-transfer rate is Q = UAΔTlm, so it increases directly with both heat-transfer area and the log mean…
Correct answer: Varies directly as the area and the LMTD- A. gD3.β.Δtρ2/μ2
- B. gD2βΔtρ/μ2
- C. gD2βΔtP2μ
- D. gD3βΔtP2/μ
Explanation: The Grashof number is Gr = gβΔTD³/ν². Since ν = μ/ρ, this becomes gD³βΔTρ²/μ², matching option a.
Correct answer: gD3.β.Δtρ2/μ2- A. Tar dolomite bricks followed by asbestos
- B. 85% magnesia cement and glass wool
- C. Cotton followed by aluminium foil
- D. Fireclay refractory followed by aluminium sheet
Explanation: Steam pipelines commonly use magnesia-based insulation, often with glass wool, because it has low thermal conductivity and can withstand…
Correct answer: 85% magnesia cement and glass wool- A. Horizontal
- B. Inclined
- C. Vertical
- D. Random
Explanation: Evaporator tubes are generally vertical because vapor and concentrated liquor can rise through them, promoting circulation and reducing…
Correct answer: Vertical- A. Less than
- B. More than
- C. Equal to
- D. Either more or less than (depending upon the fluid)
Explanation: In parallel flow, the hot and cold streams move in the same direction, and the hot-fluid outlet cannot practically fall below the…
Correct answer: Equal to- A. Grashoff
- B. Reynolds
- C. Both 'a' & 'b'
- D. Prandtl & Grashoff
Explanation: Natural-convection transition is governed by the Rayleigh number, Ra = Gr·Pr, so both the Grashof and Prandtl numbers are involved.
Correct answer: Prandtl & Grashoff- A. Increased steam economy
- B. Both A. and B.
- C. Decreased steam consumption
- D. Increased capacity
Explanation: In a multiple-effect evaporator, vapor from one effect heats the next effect, allowing the same steam to evaporate solvent repeatedly.
Correct answer: Both A. and B.- A. Both A. and B.
- B. Form friction
- C. Wall or skin friction
- D. Turbulent flow
Explanation: Heat-transfer and friction analogies relate wall shear stress to heat transfer at the fluid-solid interface, so they apply to skin or wall…
Correct answer: Wall or skin friction- A. U1 - U2
- B. U2 - U1
- C. 1/U2 - 1/U1
- D. 1/U1 - 1/U2
Explanation: The fouling resistance is the added thermal resistance caused by deposits, so 1/U_dirty = 1/U_clean + R_f.
Correct answer: 1/U1 - 1/U2- A. (1/U) Vs. (1/v0.8)
- B. (1/v0.8) Vs. U
- C. v0.8 Vs . U
- D. (1/U) Vs. (1/V)
Explanation: A Wilson plot linearizes the overall-resistance relation by plotting 1/U against the inverse velocity term, commonly 1/v^0.8.
Correct answer: (1/U) Vs. (1/v0.8)- A. 35.5
- B. 43.75
- C. 81.25
- D. 48.25
Explanation: At steady state, conduction through the wall equals convection from the oven air: (T_w − 25)k/l = (100 − T_w)(3k/l).
Correct answer: 81.25- A. Decreases the pressure drop
- B. Decreases the outlet temperature of cooling medium
- C. Increases the overall heat transfer coefficient
- D. None of these
Explanation: Multipassing increases the tube-side fluid velocity for the same flow rate and flow area per pass.
Correct answer: Increases the overall heat transfer coefficient- A. 1
- B. 2
- C. 3.5
- D. 5.5
Explanation: Calandria evaporators use relatively short vertical heating tubes, normally below about 2 m, to limit liquid head and circulation…
Correct answer: 2- A. 1.25
- B. 1.75
- C. 2.5
- D. 3.5
Explanation: The usual minimum tube pitch is about 1.25 times the tube outside diameter, providing enough ligament between adjacent tubes for…
Correct answer: 1.25