Types of Heat Transfer Chemical Engineering Questions - Set 03 - ObjectiveBooks

Types of Heat Transfer Chemical Engineering Questions - Set 03

Practice Test: Question Set - 03


1. The interchange factor for radiation heat transfer from surface 'x' to surface 'y' in case of an infinite parallel planes with emissivities εx & εy is given by
    (A) εx + εy
    (B) εx . εy
    (C) 1/εx + 1/εy
    (D) (εx + εy)/( εx + εy - εx . εy)

2. If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows __________ law.
    (A) Parabolic
    (B) Hyperbolic
    (C) Linear
    (D) Logarithmic

3. With increase in temperature, the thermal conductivity of a gas
    (A) Increases
    (B) Decreases
    (C) Remain same
    (D) May increase or decrease depending on the type of gas

4. Grashoff number is given by
    (A) gD3.β.Δtρ22
    (B) gD2βΔtρ/μ2
    (C) gD2βΔtP2μ
    (D) gD3βΔtP2

5. Which area is used in case of heat flow by conduction through a cylinder?
    (A) Logarithmic mean area
    (B) Arithmetic mean area
    (C) Geometric mean area
    (D) None of these

6. Pick out the wrong statement.
    (A) Heat transfer from a hot body to cold body by the emission of heat waves is called radiation
    (B) Filmwise condensation takes place on non-wettable surfaces
    (C) The boiling point of a solution is affected by liquid head as well as boiling point elevation
    (D) None of these

7. Choose the correct equation.
    (A) Nu = (Re) (Pr) (Gz)
    (B) Nu = (Re) (Pr) (St)
    (C) Nu = (Re) (Pr)
    (D) Nu = (Pr) (St)

8. In a heat exchanger, the rate of heat transfer from the hot fluid to the cold fluid
    (A) Varies directly as the area and the LMTD
    (B) Directly proportional to LMTD and inversely proportional to the area
    (C) Varies as square of the area
    (D) None of these

9. Pick out the wrong statement.
    (A) 'Solvates' are chemical compounds formed by solute with their solvents. When water is the solvent, then it is called a 'hydrate'
    (B) In heat exchanger calculations (Δt) weighted is used in place of Δt, when it involves more than one sequence of heating or cooling i.e., desuperheating & condensation or condensation & sub-cooling
    (C) Heat transfer co-efficient during nucleate boiling is not influenced by the agitation imparted
    (D) In case of short tube vertical evaporators, area of central downtake is about 50 to 100% of the total tube cross-sectional area

10. For what value of Prandtl number, St = f/2?
    (A) 1.5
    (B) 1
    (C) > 1
    (D) < 1

11. The rate of emission of radiation by a body does not depend upon the
    (A) Wavelength of radiation
    (B) Surface temperature of the body
    (C) Nature of the surface
    (D) Shape and porosity of the body

12. Heat sensitive materials can be concentrated in an evaporator employing
    (A) Vacuum
    (B) High pressure
    (C) High residence time
    (D) None of these

13. In a cooling tower, water becomes cool by
    (A) Loosing sensible heat
    (B) Heat transfer to surroundings
    (C) Vaporization due to heat loss to air
    (D) Loosing latent heat

14. Conductance is given by (where, x = thickness, A = heat flow area, K = thermal conductivity.)
    (A) x/KA
    (B) KA/x
    (C) K/Ax
    (D) A/Kx

15. Out of the following four assumptions used in the derivation of the equation for LMTD
[LMTD = (∆t1 - ∆t2)/ln(∆t1/∆t2)], which one is subject to the largest deviation in practice ?
    (A) Constant overall heat transfer co-efficient
    (B) Constant rate of fluid flow
    (C) Constant specific heat
    (D) No partial phase change in the system

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