Mechanical Engineering :: Heat and Mass Transfer
- A heat exchanger with heat transfer surface area A and overall heat transfer coefficient U handles two fluids of heat capacities Cmax and Cmin. The number of transfer units (NTU) used in the analysis of heat exchanger is specified as
- Reynolds number is the ratio of
- If the temperature of a solid surface changes form 27°C to 627°C, then its emissive power changes in the ratio of
- Kirchhoff's law states that
- Metals are good conductors of heat because
- Thermal conductivity of air at room temperature in kcal/m hr °C is of the order of
- According to Stefan's law, the total radiation from a black body per second per unit area is proportional to
- The critical temperature is the temperature
- Thermal conductivity of non-metallic amorphous solids with decrease in temperature
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A.
The total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature |
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B.
The wave length corresponding to the maximum energy is proportional to the absolute temperature |
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C.
The ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body |
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D.
None of the above |