GATE Prev Year : Heat-Transfer Test-9

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Question 1

A spherical shaped vessel of 1.4 m outer diameter is 90mm thick. Find the rate of heat leakage, if the temperature difference between the inner and outer surfaces is 220 °C. Thermal conductivity of the material of the sphere is 0.083 W/mK.

• A0.2 kW
• B0.5 kW
• C1.088 kW
• D1.6 Kw

Question 2

Which law is used in calculation in black and grey heat transfer?

• AStefan-Boltzmann law
• BYoung’s Modulus
• CKeplers law
• DNone of these

Question 3

The object shape is affected in heat transfer by:

• AShape factor
• BConduction factor
• CConvection factor
• DRadiation factor

Question 4

For conducting through a spherical wall with constant thermal conductivity and with inner side temperature greater then outer wall temperature, (one dimensional heat transfer), what is the type of temperature distribution ___________?

• ALinear
• BParabolic
• CHyperbolic
• DNone of these

Question 5

In a condenser, water enters a 30°C and flows at the rate 1500 kg/hr. The condensing steam is at a temperature of 120°C and cooling water leaves the condenser at 80°C. Specific heat of water is 4.187 kJ/kg K. If the overall heat transfer coefficient is 2000 W/m² K, the heat transfer area is _______.

• A0.707 m²
• B7.07 m²
• C70.7 m²
• D141.4 m²

Question 6

The following figure was generated from experimental data relating spectral black body emissive power to wave length at three temperatures T₁, T₂ and T₃ (T₁> T₂ <T₃).

The conclusion is that the measurements are

• Acorrect because the maxima in b E l show that correct trend
• Bcorrect because Planck’s law is satisfied
• Cwrong because the Stefan Boltzmann law is not satisfied
• Dwrong because Wien’s displacement law is not satisfied

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