Q. Heat exchanger tubes are never made of

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Q. At constant temperature, the thermal conductivities of gases __________ with rise in pressure.

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Q. A __________ evaporator employs an annular downtake.

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Q. Radiation heat losses from satisfactorily insulated high pressure boilar may be about __________ percent.

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Q. In natural convection heat transfer, the correlating parameter is the

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Q. Boiling of milk in an open vessel is an example of __________ boiling.

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Q. Pick out the wrong statement.

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Q. The value of Stefan-Boltazman constant in SI unit is

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Q. The unit of heat transfer co-efficient is

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Q. For turbulent flow in a tube, the heat transfer co-efficient is obtained from the Dittus-Boelter correlation. If the tube diameter is halved and the flow rate is doubled, then the heat transfer co-efficient will change by a factor of

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Q. The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m⁻¹.°C⁻¹ respectively. The ambient air is at 30°C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m⁻².°C⁻¹. The rate of heat loss from the outer surface in W.m⁻² is

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Q. Value of Nusselt number [Nu = (hD/k)] for the heat transfer by conduction from a droplet or a spherical particle to a surrounding stagnant film is

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Q. Pick out the wrong statement.

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Q. Evaporation by thermocompression results in the

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Q. Forced circulation evaporators are normally used for concentrating liquids having

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Q. Steam economy in case of a triple effect evaporator will be

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Q. In a heat exchanger with steam outside the tubes, a liquid gets heated to 45°C, when its flow velocity in the tubes is 2 m/s. If the flow velocity is reduced to 1 m/s, other things remaining the same, the temperature of the exit liquid will be

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Q. Multiple effect evaporation accounts for

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Q. In case of a supercooled solution, which is on the verge of crystallisation, the free energy of the solution as compared to that of the solid is

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Q. Maximum water velocity in tubes of a 1-2 shell and tube heat exchanger may be around __________ metres/second.

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