All Free Chemical Engineering MCQs with Answers

• A. 250
• B. 450
• C. 650
• D. 750

Explanation: A vacuum of 650 mm Hg corresponds to an absolute pressure of about 110 mm Hg when atmospheric pressure is 760 mm Hg.

• A. Same as that for fluid flow
• B. More than that for fluid flow
• C. Less than that for fluid flow
• D. D2 - D1 (D1 and D2 are I.D. of inner and outer pipes respectively)

Explanation: For annular flow, the heat-transfer hydraulic radius is based on the heat-transfer surface, whereas the flow hydraulic radius uses the…

• A. Equal to the tube diameter
• B. More than the tube diameter
• C. Not less than one-fourth of the tube diameter or 3/16″
• D. More in case of triangular pitch as compared to the square pitch tube layout

Explanation: Tube layout requires sufficient clearance for fabrication, cleaning, and fluid flow, generally at least one-fourth of the tube diameter or…

• A. Less than arithmetic mean value
• B. More than arithmetic mean value
• C. More than geometric mean value
• D. Both B. & C.

Explanation: The logarithmic mean temperature difference lies between the geometric and arithmetic means, and the multipass correction factor further…

• A. Both B. and C.
• B. Not greater than
• C. Not less than one fifth of
• D. More than

Explanation: Shell-side baffle spacing is normally kept between about one-fifth of the shell inside diameter and the shell diameter.

• A. 4(P2 - πd2/4)/πd
• B. (P2 - rd2/4)/rd
• C. 4P2/πd
• D. πd/4P2

Explanation: Equivalent diameter is four times the flow area divided by the wetted perimeter.

• A. Same
• B. Less
• C. About 3 times
• D. About 0.33 times

Explanation: For similar condensing conditions, condensate drains more effectively and the film resistance is lower on a horizontal condenser, giving a…

• A. 15-20
• B. 5-10
• C. 30-35
• D. 35-40

Explanation: Heat-transfer equipment is commonly given an overdesign allowance of about 15–20% to cover fouling, uncertainty in coefficients, and…

• A. Higher
• B. Lower
• C. Same
• D. Unpredictable

Explanation: At equal mass velocity, gases generally have much lower film coefficients because their thermal conductivity and density are far lower…

• A. Always less than the diameter of the tube
• B. Called tube clearance
• C. Called tube pitch
• D. None of these

Explanation: Tube pitch is the centre-to-centre distance between adjacent tubes in a tube bundle.

• A. Aluminium
• B. Stainless steel
• C. Copper
• D. Carbon steel

Explanation: Copper has a higher thermal conductivity than aluminium, carbon steel, and stainless steel, so it gives the lowest tube-wall resistance…

• A. Geometric mean of the true temperature difference and the LMTD
• B. Ratio of LMTD to the true temperature difference
• C. Differenced of true temperature difference and the LMTD
• D. Ratio of true temperature difference to the LMTD

Explanation: For multipass or cross-flow exchangers, the actual mean temperature driving force is lower than the ideal countercurrent LMTD.

• A. Tubes to avoid the expansion of high pressure shell construction
• B. Shell side for smaller total pressure drop
• C. Shell side, if the flow is counter-current and tube side if the flow is co-current
• D. Shell side for large overall heat transfer co-efficient

Explanation: Routing the high-pressure fluid through the tubes reduces the required thickness and cost of the pressure-containing shell, while tube…

• A. It is unsuitable for concentrating those liquids, which form a scale or deposit salt
• B. It is suitable for process, in which the final product is a liquor instead of solid
• C. Liquor flows inside the tube, while the steam is outside submerging the tube
• D. height = 2.5-4 metres
• E. Its usual dimensions are: tube dia = 2-3 cms; evaporator body dia = 1-4 metres and evaporator

Explanation: In a horizontal-tube evaporator, steam generally flows inside the horizontal tubes and the liquor remains outside, where it is heated by…

• A. Electric immersion
• B. None of these
• C. Steam coil
• D. Pipestill

Explanation: A pipestill, or fired tubular heater, heats crude by passing it through tubes exposed to hot combustion gases before it enters the…

• A. Large latent heat
• B. Low viscosity
• C. Small latent heat
• D. None of these

Explanation: Water absorbs a large amount of heat during vaporisation because its latent heat of vaporisation is high.

• A. Forced
• B. Natural
• C. Induced
• D. None of these

Explanation: Natural-draft towers use the density difference between warm, moist tower air and cooler ambient air to establish airflow.

• A. Dew point
• B. Wet bulb
• C. Both A & B
• D. Neither A nor B

Explanation: For unsaturated air, the dry-bulb temperature is higher than the wet-bulb temperature, and the wet-bulb temperature is higher than the…

• A. Evaporation
• B. Blowdown
• C. Entrainment
• D. All A., B. & C.

Explanation: Cooling-tower water is lost through evaporation, drift or entrainment, and intentional blowdown used to control dissolved solids.

• A. Both A. & B.
• B. Is equal to the number of kg, of water circulated times the cooling range
• C. Means the amount of heat thrown away (KCal/hr.) by the cooling tower
• D. Neither A. nor B.

Explanation: Cooling-tower heat load is the heat rejected per hour, and for water it is calculated approximately as mass flow rate multiplied by the…