Heat and Mass Transfer - Set 07 - ObjectiveBooks

# Practice Test: Question Set - 07

1. The value of the wavelength for maximum emissive power is given by
(A) Wien's law
(B) Planck's law
(C) Stefan's law
(D) Fourier's law

2. The heat of sun reaches to us according to
(A) Conduction
(B) Convection
(D) None of these

3. Log mean temperature difference in case of counter flow compared to parallel flow will be
(A) Same
(B) More
(C) Less
(D) Depends on other factors

4. Sensible heat factor is given by (where S.H. = Sensible heat, and L.H. = Latent heat)
(A) S.H/(S.H + L.H)
(B) (S.H + L.H) /S.H
(C) (L.H - S.H)/S.H
(D) S.H/(L.H - S.H)

5. The energy distribution of an ideal reflector at higher temperatures is largely in the range of
(A) Shorter wavelength
(B) Longer wavelength
(C) Remain same at all wavelengths
(D) Wavelength has nothing to do with it

6. The most commonly used method for the design of duct size is the
(A) Velocity reduction method
(B) Equal friction method
(C) Static regains method
(D) Dual or double method

7. Total emissivity of polished silver compared to black body is
(A) Same
(B) Higher
(C) More or less same
(D) Very much lower

8. The rate of heat flow through a body is Q = [kA (T₁ - T₂)]/x. The term x/kA is known as
(A) Thermal coefficient
(B) Thermal resistance
(C) Thermal conductivity
(D) None of these

9. According to Stefan Boltzmann law, ideal radiators emit radiant energy at a rate proportional to
(A) Absolute temperature
(B) Square of temperature
(C) Fourth power of absolute temperature
(D) Fourth power of temperature

10. The transfer of heat by molecular collision is known as
(A) Conduction
(B) Convection
(D) None of these

11. Which of the following property of air does not increase with rise in temperature?
(A) Thermal conductivity
(B) Thermal diffusivity
(C) Density
(D) Dynamic viscosity

12. The expression Q = ρ AT4 is called
(A) Fourier equation
(B) Stefan-Boltzmann equation
(C) Newton Reichmann equation
(D) Joseph-Stefan equation

13. The unit of Stefan Boltzmann constant is
(A) watt/cm² °K
(B) watt/cm⁴ °K
(C) watt²/cm °K⁴
(D) watt/cm² °K⁴

14. The unit of Stefan-Boltzmann constant is
(A) Watt/mK
(B) Watt/m²K²
(C) Watt/m²K4
(D) Watt/mK²

15. In free convection heat transfer, Nusselt number is function of
(A) Grashoff number and Reynold number
(B) Grashoff number and Prandtl number
(C) Prandtl number and Reynold number
(D) Grashoff number, Prandtl number and Reynold number

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