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 16 of 33
- A. Higher condensing film co-efficient is desired
- B. Condensate is corrosive in nature
- C. Lower pressure drop through the exchanger is desired
- D. Temperature of the incoming vapor is very high
Explanation: A corrosive condensate is placed inside the tubes so the expensive corrosion-resistant material is limited to the tube side and cleaning…
Correct answer: Condensate is corrosive in nature- A. Cube
- B. Plate
- C. Sphere
- D. All will cool at the same rate
Explanation: For equal mass and material, the sphere has the smallest surface-area-to-volume ratio.
Correct answer: Sphere- A. Increases the rate of condensation
- B. Decreases thermal resistance
- C. Is desirable to increase the film co-efficient
- D. None of these
Explanation: A non-condensing gas accumulates near the condensing surface and adds mass-transfer and heat-transfer resistance.
Correct answer: None of these- A. Grashoff number
- B. Peclet number
- C. Reynolds number
- D. Prandtl number
Explanation: Natural convection is driven by buoyancy caused by density differences, and its relative strength is measured by the Grashof number.
Correct answer: Grashoff number- A. BTU/hr. °F. ft
- B. BTU/hr. ft2°F
- C. BTU/hr. °F
- D. BTU/hr. ft
Explanation: The heat-transfer coefficient relates heat flux to temperature difference, so its units are energy divided by time, area, and temperature…
Correct answer: BTU/hr. ft2°F- A. Finned tube heat exchanger with air inside and steam outside
- B. Shell and tube heat exchanger with air inside tubes and steam on shell side
- C. Finned tube heat exchanger with air outside and steam inside
- D. Shell and tube heat exchanger with air on shell side and steam inside tubes
Explanation: Air has a much lower heat-transfer coefficient than condensing steam, so fins should be placed on the air side to increase its effective…
Correct answer: Finned tube heat exchanger with air outside and steam inside- A. W/m.k
- B. W/m
- C. None, 'a' is just a number
- D. W/m.k2
Explanation: Since K has units W/(m·K) and T has units K, the coefficient a in K = K0 + aT must have units W/(m·K²).
Correct answer: W/m.k2- A. 0.6 to 120
- B. 0.001 to 1
- C. 0.5 to 5
- D. 120 to 400
Explanation: The Colburn heat and mass transfer analogy is commonly applied over approximately 0.6 < Pr < 120.
Correct answer: 0.6 to 120- A. 0.06 to 120
- B. 1 to 103
- C. 0.6 to 120
- D. 1 to 50
Explanation: The Colburn analogy is commonly applied for Prandtl numbers from about 0.6 to 120.
Correct answer: 0.6 to 120- A. Thermal conductivity
- B. Thermal diffusivity
- C. Heat transfer co-efficient
- D. Heat flux
Explanation: Heat flux is the heat-transfer rate per unit area, q/A, and is commonly measured in W/m².
Correct answer: Heat flux- A. Sum
- B. Difference
- C. Ratio
- D. None of these
Explanation: Tube pitch is the centre-to-centre spacing between adjacent tubes, equal to the tube outside diameter plus the clear gap between tubes.
Correct answer: Sum- A. Small
- B. All
- C. Large
- D. One fixed
Explanation: An ideal black body emits radiation over the complete wavelength spectrum, although the intensity is not equal at every wavelength.
Correct answer: All- A. Decreases
- B. Remain constant
- C. Increases
- D. First decreases upto certain temperature and then increases
Explanation: In non-metallic amorphous solids, heat is carried mainly by lattice vibrations, and their thermal conductivity generally increases with…
Correct answer: Increases- A. 0.5
- B. 2
- C. 10
- D. 100
Explanation: For conduction from an isolated sphere into a stagnant surrounding medium, the characteristic spherical solution gives Nu = hD/k = 2.
Correct answer: 2315. The main purpose of providing fins on heat transfer surface is to increase the_________________?
- A. Heat transfer area
- B. Mechanical strength of the equipment
- C. Temperature gradient
- D. Heat transfer co-efficient
Explanation: Fins extend the available solid-fluid interface, increasing the heat-transfer area and therefore the total heat-transfer rate.
Correct answer: Heat transfer area- A. Pool
- B. Nucleate
- C. Film
- D. Transition
Explanation: When a stable vapour or gas blanket separates the hot surface from the liquid, the process is called film boiling.
Correct answer: Film- A. 77.2
- B. 71.2
- C. 63.8
- D. 48.7
Explanation: The conduction and convection resistances are 0.2/1.2 and 1/10 m²·K/W, respectively.
Correct answer: 48.7- A. Both A. and B.
- B. Total radiation only
- C. Monochromatic radiation only
- D. Only volumes and not to surfaces
Explanation: Kirchhoff’s law relates emissive power and absorptivity and can be stated for both wavelength-specific radiation and total radiation.
Correct answer: Both A. and B.- A. 16.5 kW/m2
- B. 12.0 kW/m2
- C. 14.6 kW/m2
- D. 11.2 kW/m2
Explanation: For the same furnace temperature, net radiation varies as T_element⁴ − T_furnace⁴, with temperatures in kelvin.
Correct answer: 16.5 kW/m2- A. 125
- B. 133
- C. 150
- D. 160
Explanation: The resistance of layer A is (L_B/2)/(2k_B)=L_B/(4k_B), while that of B is L_B/k_B, so the temperature drops divide in the ratio 1:4.
Correct answer: 160