All Free Chemical Engineering MCQs with Answers

• A. Corrosiveness
• B. Fouling characteristic
• C. Viscosity
• D. None of these

Explanation: Corrosiveness, fouling tendency, and viscosity all influence whether a fluid should flow through the tubes or shell side.

• A. 1
• B. 0
• C. 0.78
• D. 0.95

Explanation: A black body absorbs all incident radiation, so its absorptivity is unity.

• A. Exit-fluid temperature > wall temperature
• B. Exit fluid temperature = wall temperature
• C. Exit fluid temperature < wall temperature
• D. Graetz number > 100

Explanation: In the asymptotic condition, the fluid temperature approaches the constant wall temperature as the tube length becomes very large.

• A. High vacuum in the evaporator
• B. High evaporation rate
• C. Foaming of the solution
• D. High heat transfer rate

Explanation: Foaming carries liquid droplets into the vapour outlet, producing entrainment in evaporators.

• A. Provide very large heat transfer co-efficient
• B. Results in making part of the heating surface inactive
• C. Results in abruptly increased velocity
• D. None of these

Explanation: When the outlet temperature approaches the heating-fluid or wall temperature, increasing the exchanger length gives negligible additional…

• A. Both A. and B.
• B. Less surface area is required for a given heat transfer rate
• C. LMTD is greater
• D. More surface area is required for a given heat transfer rate

Explanation: For the same terminal temperatures, countercurrent flow generally gives a larger LMTD than parallel flow.

• A. 1
• B. < 1
• C. > 1
• D. None of these

Explanation: The economy of a single-effect evaporator is normally less than unity because some steam heat is consumed in heating the feed and is lost…

• A. Heat exchanger
• B. Condenser
• C. Multiple effect evaporator
• D. Steam jacketed kettle

Explanation: A steam-jacketed kettle is suitable for small-scale evaporation because steam heats the vessel indirectly and the liquor can be evaporated…

• A. < 1
• B. > 1
• C. 1
• D. ∞

Explanation: Counter-current flow maintains a larger average temperature-driving force than parallel flow for the same terminal temperatures, so its…

• A. Dense structure
• B. High proportion of air space
• C. High specific heat
• D. None of these

Explanation: Insulating materials contain many small air spaces, and trapped air has very low thermal conductivity.

• A. True temperature drop increases
• B. Capacity of the evaporator is increased
• C. Capacity of the evaporator is decreased
• D. Both B. and C.

Explanation: Raising the liquor level in a vertical-tube evaporator increases the hydrostatic pressure and boiling-point elevation, reducing the…

• A. Heating volume
• B. None of these
• C. Nusselt number
• D. Heat transfer area

Explanation: The heat-transfer rate is expressed as Q = UAΔT, where U is the overall coefficient, A is the heat-transfer area, and ΔT is the…

• A. k/ρCp
• B. ρCp/k
• C. μCp/a
• D. μ/hCp

Explanation: Thermal diffusivity measures how quickly temperature disturbances spread through a material and is defined as α = k/(ρCp).

• A. Least at the inlet of the first effect
• B. Least at the outlet of the last effect
• C. Highest at the inlet of the last effect
• D. Highest at the outlet of the last effect

Explanation: In forward-feed operation, the feed and vapor move from the first effect toward the last, while pressure is progressively reduced to…

• A. Iron plates
• B. Coal dust
• C. Refractory bricks
• D. Aluminium foil

Explanation: A bright aluminium foil surface reflects most incident radiation and therefore has very low absorptivity.

• A. Newton's law of cooling
• B. Fourier's law
• C. Fick's law
• D. None of these

Explanation: Convective heat transfer involves bulk movement of a fluid and is correlated by Newton’s law of cooling, Q = hAΔT.

• A. Flows through the tube
• B. Flows outside the tubes
• C. Can flow either inside or outside the tubes
• D. Should not be used as it gives very high pressure drop

Explanation: The lower heat-transfer coefficient produces the greater thermal resistance, so that fluid is placed outside the tubes where extended fins…

• A. r = 2k/h
• B. r = k/2h
• C. r = k/h
• D. r = h/k

Explanation: For a cylindrical pipe, the critical insulation radius is obtained by balancing the increase in outer convection area against the added…

• A. Economiser
• B. Regenerator
• C. None of these
• D. Ceramic recuperator

Explanation: An economiser, regenerator, and ceramic recuperator can all recover sensible heat from hot flue gas by transferring it to incoming feed…

• A. Velocity of circulation
• B. Liquor-film co-efficient
• C. Both A. and B.
• D. Neither A. and B.

Explanation: Raising the liquor level increases the static head over the heated tubes, which suppresses boiling and natural circulation.