All Free Chemical Engineering MCQs with Answers

• A. Interfacial tension
• B. Liquid viscosity
• C. Hot surface temperature
• D. Liquid density

Explanation: Interfacial tension strongly controls the force holding a vapour bubble to the heated surface and therefore affects the size and rate of…

• A. Type of absorbing surface
• B. None of these
• C. Surface area and temperature of the heat source
• D. Distance between the heat source and the object receiving the heat

Explanation: Radiation exchange depends on the absorbing surface, separation distance, emitting area and temperature, so each listed factor can affect…

• A. 1
• B. 1/2
• C. 2
• D. 4

Explanation: With the same total flow and tube dimensions, a double-pass exchanger sends the flow through roughly half as many parallel tubes during…

• A. Brinkman number
• B. Stanton number
• C. Peclet number
• D. Schmidt number

Explanation: The Schmidt number, Sc = ν/D, compares momentum diffusivity with mass diffusivity and belongs primarily to mass transfer.

• A. Kopp's
• B. Antoine
• C. Lee's
• D. Kistyakowsky

Explanation: Kopp's equation correlates the thermal conductivity of a solid with temperature.

• A. Temperature distribution is independent of time
• B. Temperature distribution is dependent on time
• C. Heat flows in one direction only
• D. Three dimensional heat flow is concerned

Explanation: Unsteady or transient conduction is identified by a temperature field that changes with time, even if heat flows in only one direction.

• A. t = 283 s
• B. t = 800 s
• C. t = 400 s
• D. t = 356 s

Explanation: For a semi-infinite rod with a suddenly fixed end temperature, temperature depends on x divided by the square root of time.

• A. 1 to 2
• B. 1000 to 2000
• C. 100 to 500
• D. 5 to 10

Explanation: For water near ordinary engineering temperatures, the Prandtl number is commonly of the order of 5 to 10, decreasing as temperature rises.

• A. Contaminated cooling
• B. Smooth clean
• C. Clean and dirt free
• D. Polished

Explanation: Dropwise condensation is promoted by a contaminated or coated surface that does not allow the condensate to spread as a continuous film.

• A. Decrease
• B. First increase and then decrease
• C. First decrease and then increase
• D. Increase

Explanation: For a cylindrical pipe, adding insulation first increases the outer area and can increase heat loss until the critical insulation radius…

• A. 0.5
• B. 1
• C. 0
• D. 2

Explanation: An opaque body transmits no radiation, so its absorptivity and reflectivity account for all incident radiation. Therefore, α + ρ = 1.

• A. Basket type
• B. Long tube vertical
• C. Short tube vertical
• D. Horizontal tube

Explanation: In a horizontal-tube evaporator, steam is passed inside the horizontal tubes while the liquor flows over their outer surfaces.

• A. 1.49
• B. 1
• C. 4.88
• D. None of these

Explanation: Converting the units gives 1 Btu/(hr·ft·°F) = 0.252 × 9/(0.3048 × 5) kcal/(hr·m·°C) ≈ 1.49. Therefore, option a is correct.

• A. Black & smooth
• B. Black & rough
• C. White & smooth
• D. White & rough

Explanation: A black surface absorbs and emits radiation strongly, while a rough surface generally has higher emissivity than a polished smooth…

• A. Brick
• B. Air
• C. Water
• D. Silver

Explanation: Silver has a very high thermal conductivity because its free electrons transport energy efficiently.

• A. Steam pressure
• B. Feed temperature
• C. Number of effect
• D. Both B. & C.

Explanation: Evaporator economy is strongly improved by using multiple effects and by feeding the solution hot, because less live steam is required per…

• A. Buffer zone
• B. Viscous sub-layer
• C. Both A. and B.
• D. Turbulent core

Explanation: For Prandtl number greater than one, thermal diffusivity is lower than momentum diffusivity, so the thermal boundary layer lies inside the…

• A. 1
• B. > 1
• C. < 1
• D. > 5

Explanation: When Prandtl number is less than 1, momentum diffuses more slowly than heat, so the thermal boundary layer becomes thicker than the…

• A. Remain unaffected
• B. Increases
• C. Increases exponentially
• D. Decreases

Explanation: Radiation intensity decreases as the source-receiver distance increases, following an inverse-square relationship for a point source.

• A. Decreases
• B. Increases
• C. Remains unchanged
• D. Increases exponentially

Explanation: For many liquid solutions, increasing solute concentration disrupts molecular energy transport and generally lowers thermal conductivity.