Heat Transfer
For small temperature difference, the heat transfer rate as per Newton's law of cooling is proportional to (where, Δt = excess temperature)

√Δt
Δt
Δt³
Δt²

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

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
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
A red hot steel slab (having outside surface temperature as 1300°C) exposed to the atmosheric air at 35°C

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Heat Transfer
Water always boils when its

Saturated vapour pressure equals the external pressure on its surface
Vapour pressure equals 76 cm of Hg
Saturated vapour pressure is less than the atmospheric pressure
Temperature reaches 100° C

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