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 12 of 33
- A. Vertical heat exchanger with steam on tube side
- B. Vertical heat exchanger with steam on shell side
- C. Horizontal heat exchanger with steam on tube side
- D. Horizontal heat exchanger with steam on shell side
Explanation: Placing steam on the shell side allows condensation over the outside of the tubes, while cooling water flows inside them.
Correct answer: Vertical heat exchanger with steam on shell side- A. Both B. and C.
- B. Solids
- C. Liquids
- D. Gases
Explanation: Solids and most liquids absorb or reflect thermal radiation rather than transmitting it, so they are generally treated as opaque.
Correct answer: Both B. and C.- A. Both A. and B.
- B. Non-isothermal
- C. Isothermal
- D. Neither A. and B.
Explanation: Fourier’s law relates conductive heat flux to the temperature gradient, and it can be applied with respect to isothermal surfaces as well…
Correct answer: Both A. and B.- A. √(ΔT1 . ΔT2)
- B. 2 (ΔT1 . ΔT2)/(ΔT1 - ΔT2)
- C. 2 (ΔT1 . ΔT2)/(ΔT1 + ΔT2)
- D. (ΔT1 - ΔT2)/(ΔT1 . ΔT2)
Explanation: The harmonic mean of two temperature differences is twice their product divided by their sum. Therefore, ΔT_h = 2ΔT1ΔT2/(ΔT1+ΔT2).
Correct answer: 2 (ΔT1 . ΔT2)/(ΔT1 + ΔT2)- A. ha = hl
- B. ha = 0.75 hl
- C. ha = 0.5 hl
- D. ha = 2hl
Explanation: For laminar flow over a flat plate, the local coefficient varies approximately as x⁻¹ᐟ².
Correct answer: ha = 2hl- A. Density
- B. Viscosity
- C. Thermal conductivity
- D. Heat capacity
Explanation: Heating changes fluid density, causing the warmer and cooler regions to rise or sink differently under gravity.
Correct answer: Density- A. 555
- B. 55.5
- C. 0.55
- D. 0.15
Explanation: For a lumped sphere, the time constant is ρc_pr/(3h) = 800 s. Since (60−30)/(90−30) = 0.5, t = 800 ln 2 = 554 s ≈ 0.15 h, so the very…
Correct answer: 0.15- A. Stanton
- B. Nusselt
- C. Prandtl
- D. Grashoff
Explanation: The Prandtl number is the ratio of momentum diffusivity, ν, to thermal diffusivity, α: Pr = ν/α.
Correct answer: Prandtl- A. Between 0 and ∞
- B. One
- C. ∞
- D. Zero
Explanation: A perfect insulator permits no conductive heat flow, so Fourier’s law requires its thermal conductivity to be zero.
Correct answer: Zero- A. 0.1714 x 10^-8W/m2.°K4
- B. 5.6697 x 10^-8W/m2.°K4
- C. 5.6697 x 10^-8kcal/m2. °K4
- D. 0.1714 x 10^-8kcal/m2. °K4
Explanation: The SI Stefan-Boltzmann constant is σ = 5.6697 × 10⁻⁸ W/m²·K⁴. The kcal-based values are not in the requested SI unit.
Correct answer: 5.6697 x 10^-8W/m2.°K4- A. Plate type
- B. Double pipe type with fin on steam side
- C. Double pipe type with fin on air side
- D. Shell and tube type
Explanation: Air has a much lower convective heat-transfer coefficient than condensing steam, so the air-side resistance controls the exchanger design.
Correct answer: Double pipe type with fin on air side- A. Agitated film evaporator
- B. None of these
- C. Open pan evaporator
- D. Long tube vertical evaporator
Explanation: A long-tube vertical evaporator is commonly used for foaming or frothy liquors because the rising vapor helps carry the liquid upward and…
Correct answer: Long tube vertical evaporator- A. 1000
- B. 727
- C. 800
- D. 1200
Explanation: From q = εσT⁴, T = [22,680/(0.4 × 5.67 × 10⁻⁸)]¹/⁴, which is approximately 1000 K.
Correct answer: 1000- A. Increases rapidly with temperature rise
- B. Decreases rapidly with temperature rise
- C. In independent of pressure
- D. Both B. and C.
Explanation: For an ideal dilute solution, ΔT_b = K_bm, and K_b is approximately proportional to T_b²/ΔH_vap, so the elevation increases as the boiling…
Correct answer: Increases rapidly with temperature rise- A. Facilitate the cleaning of outer tube surface
- B. Hold the tubes in position
- C. Enhance turbulence
- D. All A , B & C
Explanation: Baffles direct the shell-side fluid across the tubes, increasing its velocity and turbulence and therefore improving heat transfer.
Correct answer: Enhance turbulence- A. 5000-15000
- B. 100-500
- C. 1000-1500
- D. 10-50
Explanation: Condensing steam provides a high heat-transfer coefficient, typically about 5000–15000 kcal/(h·m²·°C) in evaporators.
Correct answer: 5000-15000- A. Wavelength of radiation
- B. Temperature of the body
- C. Nature of the body
- D. None of these
Explanation: Kirchhoff’s law gives E/α = Eb, where Eb is the blackbody emissive power at the body’s temperature.
Correct answer: Temperature of the body- A. Δt3
- B. Δt2
- C. Δt
- D. √(Δt)
Explanation: Newton’s law of cooling states that heat-transfer rate is proportional to the excess temperature for small temperature differences: q ∝…
Correct answer: Δt239. Overall heat transfer co-efficient for cooling of hydrocarbons by water is about_________________?
- A. 50 -100 Kcal/hr.m2.°C
- B. 50 -100 W/m2.°K
- C. 50 -100 BTU/hr. ft.2°F
- D. 1000 - 1500 BTU/hr. ft.2°F
Explanation: Cooling hydrocarbons with water commonly gives an overall coefficient of roughly 50–100 Btu/(h·ft²·°F), because the hydrocarbon-side…
Correct answer: 50 -100 BTU/hr. ft.2°F- A. Horizontal tube
- B. Basket type
- C. Calandria
Explanation: A basket-type evaporator has a removable heating basket, allowing the tubes to be taken out and cleaned intermittently.
Correct answer: Basket type