All Free Chemical Engineering MCQs with Answers

• A. The porosity of the bed when true fluidisation begins
• B. That corresponding to completely fluidised bed
• C. That corresponding to static bed
• D. Less than that of the' static bed

Explanation: The minimum fluidisation porosity is the bed voidage at the instant fluidisation begins, when the upward fluid force just supports the bed…

• A. Wall roughness
• B. Both A. & B.
• C. Reynolds number
• D. Neither A. nor B.

Explanation: For turbulent flow, frictional pressure loss depends on both Reynolds number and wall roughness through the friction factor.

• A. Sump
• B. Volute
• C. Vacuum
• D. Submerged

Explanation: A vacuum pump draws gas from a pressure below atmospheric and discharges it at or near atmospheric pressure.

• A. Employs impellers in both the radial & axial directions
• B. Mixes the two fluids before pumping them
• C. Pumps the two fluids separately and then mixes them
• D. Employs such an impeller, through which the flow is a combination of radial & axial flow

Explanation: A mixed-flow pump combines the two principal flow patterns: fluid leaves the impeller with both radial and axial components.

• A. Vacuum pump
• B. Compressor
• C. Blower
• D. Fan

Explanation: A vacuum pump can produce a very low suction pressure while discharging near atmospheric pressure, giving a larger pressure ratio than…

• A. G is above B
• B. B is above G
• C. B & G coincide
• D. None of these

Explanation: A fully submerged body is stable when its centre of buoyancy lies above its centre of gravity, so a small tilt produces a restoring…

• A. Same
• B. Less
• C. More
• D. Unpredictable

Explanation: A soap bubble has two liquid-gas interfaces, giving an excess pressure of 4σ/r inside the bubble.

• A. 0.1
• B. 0.5
• C. 0.94
• D. 1

Explanation: For a Borda mouthpiece, the jet contracts to approximately half the mouthpiece area at the vena contracta under the idealized frictionless…

• A. No means
• B. Use of floats of different densities
• C. Increasing the diameter of the float
• D. Decreasing the diameter of the float

Explanation: A rotameter's float position depends on the balance between buoyancy, weight and drag, so floats with different densities can provide…

• A. Used for mixing liquids of high viscosity
• B. Low speed impeller
• C. Axial flow mixers
• D. Radial flow mixers

Explanation: Propellers impart mainly axial flow and are high-speed impellers used for low- to moderate-viscosity liquids.

• A. Equal to the developed head
• B. Greater than the vapour pressure of the liquid at that temperature
• C. Equal to the vapour pressure
• D. Less than the vapour pressure of the liquid at that temperature

Explanation: Cavitation begins when the local liquid pressure falls below its vapour pressure at the operating temperature, allowing vapour bubbles to…

• A. Cavitation
• B. Low speed of impeller
• C. Its operation with delivery valve closed for considerable time after starting the pump
• D. Off centering of pump with motor

Explanation: Cavitation bubbles collapse near the impeller surface and generate shock waves, producing characteristic pitting and erosion.

• A. 0.5
• B. 1
• C. 1.5
• D. 2

Explanation: For laminar flow in a circular pipe, the parabolic velocity profile makes the kinetic-energy correction factor α equal to 2.

• A. Is always below
• B. Intersects at right angle
• C. Is the evolute of
• D. Is tangential to

Explanation: As a floating body changes orientation, the metacentre traces the evolute of the curve traced by the centre of buoyancy.

• A. Narrow
• B. Deep
• C. Neither A. nor B.
• D. Both A. & B.

Explanation: Slugging is promoted when a fluidised bed is both narrow and deep, because gas bubbles combine into large plugs spanning the bed…

• A. Expanding tube at increasing rate
• B. Long pipe at decreasing rate
• C. Long pipe at constant rate
• D. Expanding tube at constant rate

Explanation: Unsteady flow changes with time, while non-uniform flow changes with position.

• A. Vavg
• B. 1.2 Vavg
• C. 1.5 Vavg
• D. 1.8 Vavg

Explanation: The turbulent velocity profile is relatively flat compared with the parabolic laminar profile, so the centreline maximum is only about 1.2…

• A. Parabolic law
• B. Linear law
• C. Logarithmic law
• D. None of these

Explanation: In the turbulent boundary layer, velocity follows the logarithmic law in the region away from the immediate viscous sublayer.

• A. Turbulent flow
• B. Laminar flow through an open channel
• C. Steady flow
• D. None of these

Explanation: The relation f = 16/Re refers to the Fanning friction factor for laminar flow in a circular pipe.

• A. Fluid flow at the inlet to a nozzle
• B. Fluid flow between parallel plates
• C. Viscous fluid flow between converging plates
• D. None of these

Explanation: Flow entering a nozzle generally has velocity components and variation in all three spatial directions, making it three-dimensional.