Heat Transfer
Which of the following situations can be approximated to a steady state heat transfer system?

A red hot steel slab (having outside surface temperature as 1300°C) exposed to the atmosheric air at 35°C
A sub-cooled refrigerant liquid at 8°C flowing at the rate of 6 Kg/minute through a copper pipe exposed to atmospheric air at 35°C
Boiling brine kept in open vessel when the bottom surface temperature of the vessel is maintained constant at 180°C
10 kg of dry saturated steam at 8 kgf/cm² flowing through a short length of stainless steel pipe exposed to atmospheric air at 35°C

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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

Total heat transfer area of all the effects is -less than that in a single effect evaporator 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
Heat transfer co-efficient in a single effect is much lower than that in any effect in a multieffect system

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Heat Transfer
Leidenfrost point is a term concerned with the

Boiling of a liquid on a hot surface
Condensation of the saturated vapor on a cold surface
Heat transfer between two highly viscous liquids
Concentration of a corrosive solution by evaporation

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