Heat Transfer
The average heat transfer co-efficient for laminar film condensation on vertical surface is inversely proportional to (where, ΔT = Temperature drop across condensate film )

ΔT
None of the listed here
(ΔT)2
(ΔT)1/4

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Heat Transfer
A hollow sphere and a solid sphere of the same material and equal radii are heated to the same temperature. In this case,

The cooling rate will be the same for the two spheres and hence the two spheres will have equal temperatures at any instant
Both the spheres will emit equal amount of radiation per unit time in the beginning
Both will absorb equal amount of radiation from the surrounding in the beginning
Both B & C

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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
4000
5000
6000

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