Heat Transfer
The heat transfer by radiation from a mild steel surface is to be reduced by reducing the emissivity of the surface. This can be best achieved by

Painting the surface black
Giving the surface a mirror finish
Roughening the surface
Painting the surface white (with aluminium paint)

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

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
Boiling brine kept in open vessel when the bottom surface temperature of the vessel is maintained constant at 180°C

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