GATE Prev Year : Heat-Transfer Test-3

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Question 1

For the circular tube of equal length and diameter shown below, the view factor F₁₃ is 0.17. The view factor F₁₂ in this case will be

• A0.17
• B0.21
• C0.79
• D0.83

Question 2

One dimensional unsteady state heat transfer equation for a sphere with heat generation at the rate of ‘q’ can be written as

• A
• B
• C
• D

Question 3

Consider a laminar boundary layer over a heated flat plate. The free stream velocity is At some distance x from the leading edge the velocity boundary layer thickness is and the thermal boundary layer thickness is If the Prandtl number is greater than 1, then

• A
• B
• C ~
• D ~ x^–1/2

Question 4

A thin metal plate is exposed to solar radiation. The air and the surroundings are at 30 °C. The heat transfer coefficient by free convection from the upper surface of the plate is 17.4 W/m²K. The plate has an absorptivity of 0.9 at solar wavelength and an emissivity of 0.1 at the long wavelength. Neglecting any heat loss from the lower surface, determine the incident solar radiation intensity in kW/m², if the measured equilibrium temperature of the plate is 50 °C. Stefan Boltzmann constant is 5.67×10^-8 W/m²K⁴.

• A0.452
• B0.76
• C5.45
• D0.402

Question 5

What will be the heat transfer rate through the slab as shown, if Q, T1 and T2 are given?

• AQ = T_L – T_R / R = (T_L – T_R) / (R₁ + R₂)
• BQ = T_L + T_R / R = (T_L – T_R) / (R₁ + R₂)
• CQ = T_L – T_R / R = (T_L + T_R) / (R₁ + R₂)
• DQ = T_L + T_R / R = (T_L + T_R) / (R₁ + R₂)

Question 6

A solid sphere of radius r₁ = 20 mm is placed concentrically inside a hollow sphere of radius r₂ = 30 mm as shown in the figure.

The view factor F₂₁ for radiation heat transfer is

• A2/3
• B4/9
• C8/27
• D9/4

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