| 41. | Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone. |
| a. | laminar |
| b. | transition |
| c. | both 'a' & 'b' |
| d. | highly turbulent |
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Answer: (d).highly turbulent
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| 42. | The actual temperature drop across the heating surface in an evaporator depends on the |
| a. | feed. |
| b. | depth of liquid over heating surface. |
| c. | pressure difference between steam chest and vapour space. |
| d. | all (a), (b) and (c). |
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Answer: (d).all (a), (b) and (c).
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| 43. | Which of the following is not used as a medium for high temperature heating ? |
| a. | Dowtherm |
| b. | mercury |
| c. | liquid metal (e.g. molten sodium) |
| d. | fused salts (e.g., an eutectic mixture of 53% KNO₃, 40% NaNO₂and 7% NaNO₃) |
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Answer: (b).mercury
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| 44. | Presence of a non-condensing gas in a condensing vapour |
| a. | increases the rate of condensation. |
| b. | decreases thermal resistance. |
| c. | is desirable to increase the film co-efficient. |
| d. | none of these. |
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Answer: (d).none of these.
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| 45. | The average heat transfer co-efficient for laminar film condensation on vertical surface is inversely proportional to (where, ΔT = Temperature drop across condensate film ) |
| a. | (ΔT)² |
| b. | √ΔT |
| c. | (ΔT)^1/4 |
| d. | (ΔT)^3/2 |
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Answer: (c).(ΔT)^1/4
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