1. |
The diagram shows heat conduction through a plane wall. The surface temperature is 475 K and it radiates heat to the surroundings at 335 K. If thermal conductivity of the material is 12.5 W/m degree, find the temperature gradient. Let convective coefficient be 80 W/m² degree and radiation factor is 0.9
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a. | – 1052.4 degree celsius |
b. | – 2052.4 degree celsius |
c. | – 3052.4 degree celsius |
d. | – 4052.4 degree celsius |
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Answer: (a).– 1052.4 degree celsius
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2. |
From the concept of kinetic theory, mean travel velocity of the gas molecules is prescribed by the relation
(Where, G = Universal gas constant M = Molecular weight of the gas T = Absolute temperature) |
a. | V = (3M/GT)⅟₂ |
b. | V = (3GT/M)⅟₂ |
c. | V = (6T/GM)⅟₂ |
d. | V = (3GT/2M)⅟₂ |
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Answer: (b).V = (3GT/M)⅟₂
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3. | Low temperature insulation are used when the enclosure is at a temperature lower than the ambient temperature. Which one of the following is not a low temperature insulation? |
a. | Asbestos |
b. | Cork |
c. | Cattle hair |
d. | Slag wool |
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Answer: (a).Asbestos
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4. | The value of Lorenz number in 10¯⁸ W ohms/K² is |
a. | 2.02 |
b. | 2.35 |
c. | 2.56 |
d. | 2.45 |
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Answer: (d).2.45
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5. |
Consider the following parameters
(i) Composition (ii) Density (iii) Porosity (iv) Structure Then, thermal conductivity of glass wool varies from sample to sample because of variation is |
a. | 1 and 2 |
b. | 1, 2, 3 and 4 |
c. | 1 and 3 |
d. | 1, 2 and 3 |
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Answer: (b).1, 2, 3 and 4
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