All Free Chemical Engineering MCQs with Answers
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6,983 questions · page 261 of 350
5201. Which of the following increases during evaporative cooling process with recirculated water supply ?
- A. Both B. and C.
- B. Relative humidity
- C. Partial pressure of vapour
- D. Wet bulb temperature
Explanation: Evaporation adds water vapour to the circulating air, increasing both its relative humidity and water-vapour partial pressure.
Correct answer: Both B. and C.- A. Long tube vertical evaporator
- B. Agitated film evaporator
- C. Short tube evaporator
- D. Calandria
Explanation: An agitated film evaporator is suitable for concentrating rubber latex because agitation handles viscous material and the thin film gives…
Correct answer: Agitated film evaporator- A. Increasing the air velocity and area of exposed wet surface
- B. All A., B. and C.
- C. Reducing the humidity of the air
- D. Reducing the barometric pressure
Explanation: Evaporation in a cooling tower is enhanced by faster air movement, more exposed wet area, lower air humidity, and lower barometric…
Correct answer: All A., B. and C.- A. Solar evaporation
- B. Freeze drying
- C. Vacuum evaporation
- D. Electrolysis
Explanation: Vacuum evaporation removes water from brine at reduced pressure, giving better control and producing purer salt than solar evaporation…
Correct answer: Vacuum evaporation- A. L.D. converter
- B. Blast furnace
- C. Rotary kiln
- D. Recuperator
Explanation: A recuperator transfers heat from hot exhaust gases to incoming air or gas, so high thermal conductivity reduces the resistance to heat…
Correct answer: Recuperator5206. Optimum number of effects in a multiple effect evaporator is decided by the____________________?
- A. Cost benefit analysis
- B. Floor area availability
- C. Terminal parameters
- D. Evaporation capacity required
Explanation: Adding effects saves steam but increases equipment and operating complexity, so the optimum is found by comparing the economic benefit…
Correct answer: Cost benefit analysis- A. Parallel flow with equal heat capacities
- B. Counter flow with unequal heat capacities
- C. Counter flow with equal heat capacities
- D. Parallel flow with unequal heat capacities
Explanation: For counterflow with equal heat-capacity rates, both temperature profiles have the same slope, so they appear as parallel straight lines…
Correct answer: Counter flow with equal heat capacities- A. Steel
- B. Lignite
- C. Lime stone
- D. Water
Explanation: Heat stored for the same mass and temperature rise is mC_pΔT, so the material with the greatest specific heat stores the most heat.
Correct answer: Water- A. Radiation
- B. Conduction
- C. Convection
- D. Both B. & C.
Explanation: In a fluidised bed dryer, vigorous particle movement makes convection the dominant heat-transfer mode, while radiation contributes very…
Correct answer: Radiation- A. Steel
- B. Glass wood
- C. Copper
- D. Fireclay bricks
Explanation: For the same heat flow, area, and thickness, the temperature drop varies inversely with thermal conductivity.
Correct answer: Glass wood- A. Remain same
- B. Increases
- C. Decreases
- D. May increase or decrease; depends on the altitude where snow melts
Explanation: Melting snow requires latent heat, which is drawn from the surrounding atmosphere and lowers its temperature locally.
Correct answer: Decreases5212. The bank of tubes located at the back of the domestic refrigerators are the _______________ tubes?
- A. Refrigerant cooling
- B. Evaporator
- C. Throttling
- D. Condenser
Explanation: The tubes at the back release heat to the surroundings and condense the high-pressure refrigerant vapour into liquid.
Correct answer: Condenser- A. Radiation
- B. Conduction
- C. Natural convection
- D. Forced convection
Explanation: At about 1700°C, thermal radiation increases very strongly with absolute temperature and dominates over ordinary convection and conduction…
Correct answer: Radiation- A. Guard the boiler in case of abnormal rise in steam pressure
- B. Drain out water and sludge during its repair
- C. Regulate the supply of water in boiler
- D. Put out the fire in the furnace when the water level in the boiler falls to unsafe limit
Explanation: A blow-off cock is fitted at the lower part of a boiler to discharge water containing accumulated sludge and sediment, especially during…
Correct answer: Drain out water and sludge during its repair- A. Water alkalinity & leakage
- B. Hydrazine addition during feed water treatment
- C. Release of non-condensable gas from water in the boiler
- D. Scale formation
Explanation: Dissolved oxygen and other non-condensable gases promote electrochemical corrosion of boiler tubes and associated equipment.
Correct answer: Release of non-condensable gas from water in the boiler- A. Water equivalent
- B. Specific heat capacity
- C. Thermal conductivity
- D. Heat capacity
Explanation: Heat capacity is the heat required to raise the temperature of an entire body by one degree.
Correct answer: Heat capacity- A. T
- B. 1/T
- C. T2
- D. 1/T2
Explanation: The Wiedemann-Franz law states that the ratio of thermal conductivity to electrical conductivity is proportional to absolute temperature…
Correct answer: T- A. Spraying alumina powder
- B. Floating hollow polypropylene spheres
- C. Putting cement
- D. None of these
Explanation: A layer of floating hollow polypropylene spheres covers the liquid surface, reducing exposed area and limiting evaporation and heat…
Correct answer: Floating hollow polypropylene spheres- A. 0.01
- B. 0.1
- C. 0.25
- D. 0.5
Explanation: For equal heat loss and temperature drop, wall resistance must be equal: L1/k1 = L2/k2.
Correct answer: 0.1- A. 50
- B. 100
- C. 150
- D. 200
Explanation: At steady temperature, absorbed radiation equals convection: q'' = h(Ts − T∞).
Correct answer: 100