Free Heat Transfer Operations MCQs with Answers
645 Heat Transfer Operations MCQs from Chemical Engineering, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
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645 questions · page 31 of 33
- 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- A. 2
- B. 8
- C. 10
- D. 40
Explanation: For a cylinder, the critical insulation radius is r_c = k_insulation/h = 0.1/5 = 0.02 m, or 2 cm.
Correct answer: 2- A. Dryness
- B. Moisture content
- C. Coolness
- D. Latent heat
Explanation: Dew-point temperature is the temperature at which the air becomes saturated and condensation begins, so it reflects the moisture content…
Correct answer: Moisture content- A. 370
- B. 340
- C. 320
- D. 300
Explanation: Newton’s law of cooling makes the temperature excess above the bath temperature fall by the same ratio in equal time intervals.
Correct answer: 370- A. 5 to 10
- B. 15 to 25
- C. 75 to 80
- D. 45 to 50
Explanation: Human comfort near 22 to 27°C generally requires moderate relative humidity, about 45 to 50 percent.
Correct answer: 45 to 50- A. Re0.8, Re0.5
- B. Re0.8, Re-0.5
- C. Re0.5, Re0.8
- D. Re-0.8, Re0.5
Explanation: For turbulent flow, the usual heat-transfer correlation gives Nu proportional to Re^0.8, while for laminar flow the dependence is…
Correct answer: Re0.8, Re0.5- A. 1/k
- B. k
- C. k2
- D. 1/k2
Explanation: Thermal diffusivity is given by α = k/(ρCp), so with density and heat capacity fixed it is directly proportional to thermal conductivity…
Correct answer: k- A. Boiler
- B. Evaporator
- C. Condenser
- D. All A. B. & C.
Explanation: A condenser removes latent heat from vapour as it changes into liquid, so heat is released to the cooling medium.
Correct answer: Condenser- A. Evaporative capacity
- B. Evaporation efficiency
- C. Thermal efficiency
- D. Steam load
Explanation: Evaporative capacity is the mass of water converted into steam per unit mass of fuel burned, usually expressed as kg/kg of fuel.
Correct answer: Evaporative capacity- A. Providing support for the tubes
- B. Both A & B
- C. Improving heat transfer
- D. Preventing the fouling of tubes & stagnation of shell side fluid
Explanation: Shell-side baffles support the tubes and force the fluid across them, increasing turbulence and heat-transfer coefficient.
Correct answer: Both A & B- A. Less
- B. More
- C. Equal
- D. Unpredictable
Explanation: For flow over a heated flat plate, Pr > 1 means momentum diffuses faster than heat, so the thermal boundary layer is thinner than the…
Correct answer: Less- A. Enthalpy
- B. Relative humidity
- C. Wet bulb temperature
- D. Dew point temperature
Explanation: Without condensation, cooling removes sensible heat while the humidity ratio remains constant; consequently, the water-vapour partial…
Correct answer: Dew point temperature620. Which of the following commonly used condenser tube materials has the lowest thermal conductivity ?
- A. Stainless steel
- B. Admiralty brass
- C. Aluminium brass
- D. Titanium
Explanation: Stainless steel has much lower thermal conductivity than admiralty brass, aluminium brass and titanium, so it offers the greatest…
Correct answer: Stainless steel