Heat Transfer
Heat transfer co-efficient (h1) for liquids increases with

Decreasing temperature
None of these
Increasing temperature
Decreasing Reynolds number

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Heat Transfer
A dilute aqueous solution is to be concentrated in an evaporator system. High pressure steam is available. Multiple effect evaporator system is employed, because

Heat transfer co-efficient in a single effect is much lower than that in any effect in a multieffect system
Boiling point elevation in a single effect system is much higher than that in any effect in a multieffect system
Total amount of vapor produced per Kg of feed steam in a multiple effect system is much higher than in a single effect
Total heat transfer area of all the effects is -less than that in a single effect evaporator system

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Heat Transfer
A 10 cm dia 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

Equal to that of the uninsulated steam pipe
Greater than that for uninsulated steam pipe
Less than the steam pipe with 5 cms insulation
Less than that of the uninsulated steam pipe

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Heat Transfer
In a laboratory test run, the rate of drying was found to be 0.5 x 10-3 kg/m².s, when the moisture content reduced from 0.4 to 0.1 on dry basis. The critical moisture content of the material is 0.08 on a dry basis. A tray dryer is used to dry 100 kg (dry basis) of the same material under identical conditions. The surface area of the material is 0.04 m²/kg of dry solid. The time required (in seconds) to reduce the moisture content of the solids from 0.3 to 0.2 (dry basis) is

2000
5000
6000
4000

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