| 46. | Bulk of the convective heat transfer resistance from a hot tube surface to the fluid flowing in it, is |
| a. | in the central core of the fluid. |
| b. | uniformly distributed throughout the fluid. |
| c. | mainly confined to a thin film of fluid near the surface. |
| d. | none of these. |
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Answer: (c).mainly confined to a thin film of fluid near the surface.
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| 47. | Which of the following is concerned with both heat and mass transfer ? |
| a. | Lewis relationship |
| b. | Nusselt number |
| c. | Kutateladze number |
| d. | Froude number |
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Answer: (a).Lewis relationship
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| 48. | A backward feed multiple effect evaporator is better than forward feed for concentrating cold feed, because it provides |
| a. | higher economy |
| b. | lower capacity |
| c. | both (a) & (b) |
| d. | lower economy |
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Answer: (a).higher economy
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| 49. | A 10 cm diameter steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m².°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be |
| a. | greater than that for uninsulated steam pipe. |
| b. | less than that of the uninsulated steam pipe. |
| c. | equal to that of the uninsulated steam pipe. |
| d. | less than the steam pipe with 5 cms insulation. |
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Answer: (b).less than that of the uninsulated steam pipe.
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| 50. | Fouling factor |
| a. | is a dimensionless quantity. |
| b. | does not provide a safety factor for design. |
| c. | accounts for additional resistances to heat flow. |
| d. | none of these. |
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Answer: (c).accounts for additional resistances to heat flow.
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