All Free Chemical Engineering MCQs with Answers
Every Chemical Engineering question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
6,983 questions · page 260 of 350
- A. Cold water leaving the tower and the wet bulb temperature of the surrounding air
- B. Hot water entering the tower and the wet bulb temperature of the surrounding air
- C. Hot water entering the tower and the cooled water leaving the tower
- D. None of these
Explanation: Cooling-tower range is the temperature drop of the circulating water, calculated as hot-water inlet temperature minus cooled-water outlet…
Correct answer: Hot water entering the tower and the cooled water leaving the tower- A. High maintenance cost
- B. Non-uniform & low production rate
- C. High labour cost & low heat economy
- D. All 'a', 'b' & 'c'
Explanation: Batch tray dryers commonly give non-uniform drying and low production rates, while also requiring substantial labour and having poor heat…
Correct answer: High labour cost & low heat economy- A. 7
- B. 70
- C. 0.7
- D. 150
Explanation: For water near 20°C, the Prandtl number is approximately 7. It is much greater than unity because momentum diffusivity is about seven…
Correct answer: 7- A. Diffusion
- B. Heat transfer
- C. Both A. and B.
- D. Neither A. nor B.
Explanation: In a drum dryer, the wet material contacts a heated rotating drum and drying is mainly governed by the rate at which heat passes through…
Correct answer: Heat transfer- A. Range is 15°F
- B. Approach is 10°F
- C. Both A. & B.
- D. Neither A. nor B.
Explanation: The range is the decrease in water temperature, 95 - 80 = 15°F. The approach is the cold-water outlet temperature minus the entering-air…
Correct answer: Both A. & B.- A. Tray
- B. Vacuum
- C. Tunnel
- D. Rotary
Explanation: Calcium ammonium nitrate is commonly dried industrially in a rotary dryer, which provides continuous solids handling and good contact with…
Correct answer: Rotary5187. The suitable evaporator for concentration of foaming liquids is a ______________________ evaporator?
- A. Falling film
- B. Short tube
- C. Vacuum
- D. Long tube
Explanation: Long-tube evaporators are suitable for foaming liquids because the liquid and vapour move rapidly through long vertical tubes, limiting…
Correct answer: Long tube5188. Wet bulb and dry bulb temperatures becomes identical at _______________ percent saturation curve?
- A. 50
- B. 100
- C. 78
- D. None of these
Explanation: At 100% saturation, the air is fully saturated and no further evaporation occurs from the wet bulb.
Correct answer: 100- A. Drum
- B. Cylinder
- C. Rotary
- D. Freeze
Explanation: Rotary dryers are well suited to free-flowing granular solids because the rotating shell continuously lifts and tumbles the material…
Correct answer: Rotary- A. None of these
- B. Partial pressure of water vapor
- C. Relative humidity
- D. Wet bulb temperature
Explanation: With recirculated water, ideal evaporative cooling is approximately adiabatic saturation, so the wet-bulb temperature remains constant.
Correct answer: Wet bulb temperature5191. Which of the following decreases during evaporative cooling process with recirculated water supply ?
- A. None of these
- B. Relative humidity
- C. Partial pressure of vapour
- D. Wet bulb temperature
Explanation: In adiabatic evaporative cooling, some water evaporates, so the air's humidity and water-vapour partial pressure increase while its…
Correct answer: None of these- A. Humidity
- B. Both A. & B.
- C. Temperature
- D. Neither A. nor B.
Explanation: Natural-draft cooling towers depend on a strong density difference between warm, moist tower air and the cooler outside air.
Correct answer: Both A. & B.- A. Natural draft
- B. Forced draft
- C. Induced draft
- D. Atmospheric
Explanation: An induced-draft tower places the fan at the outlet, pulling air uniformly through the packing and reducing air recirculation.
Correct answer: Induced draft- A. Increasing the air velocity over the wet surfaces
- B. Reducing the humidity of entering air
- C. Lowering the barometric pressure
- D. None of these
Explanation: All three changes can enhance cooling: higher air velocity improves contact, drier entering air increases evaporation potential, and lower…
Correct answer: None of these- A. Less than the wet bulb
- B. More than the wet bulb
- C. Equal to the wet bulb
- D. Equal to the dry bulb
Explanation: A cooling tower cannot normally cool water below the entering-air wet-bulb temperature because that temperature represents the evaporative…
Correct answer: More than the wet bulb- A. Spray
- B. Rotary
- C. Cylinder
- D. Fluidised bed
Explanation: Paper is dried continuously by passing it over heated rotating cylinders, which transfer heat through the paper and evaporate its…
Correct answer: Cylinder- A. Dry-bulb
- B. Adiabatic saturation
- C. Dew point
- D. Wet-bulb
Explanation: When liquid evaporates into a large unsaturated gas stream, the liquid cools until evaporation and sensible heat transfer reach…
Correct answer: Wet-bulb- A. Both A. and B.
- B. Wet bulb temperature < dry bulb temperature
- C. Dew point < wet bulb temperature
- D. Neither A. not B.
Explanation: For unsaturated air, moisture can still evaporate, so the wet-bulb temperature is below the dry-bulb temperature.
Correct answer: Both A. and B.- A. Means discarding a small fraction of circulating water to prevent and limit the concentration
- B. of salt and impurities
- C. Increases the scale forming tendencies of water
- D. Is undesirable
- E. All A., B. & C.
Explanation: Blowdown is the controlled discharge of a small portion of circulating cooling water to remove concentrated salts and impurities.
Correct answer: Means discarding a small fraction of circulating water to prevent and limit the concentration- A. Vapor load
- B. Blow down
- C. Drift
- D. None of these
Explanation: Drift is the liquid water carried out of a cooling tower by the moving air as entrained droplets.
Correct answer: Drift