Heating of dry steam above saturation temperature is known as

Explanation:

Dry steam, or saturated steam, is characterized by the vapor quality or dryness fraction(x), which is equal to unity.

When the vapor quality is equal to 0, it is referred to as the saturated liquid state (single-phase).

On the other hand, when the vapor quality is equal to 1, it is referred to as the saturated vapor state or dry steam (single-phase).

Between these two states, vapor-liquid mixture or wet steam (two-phase mixture) exist. At constant pressure, the addition of energy does not change the temperature of the mixture, but the vapor quality and specific volume change.

In the case of dry steam (100% quality), it contains 100% of the latent heat available at that pressure. Saturated liquid water, which has no latent heat and therefore 0% quality, will therefore only contain sensible heat.

Dryness fraction is defined as the ratio of the mass of dry steam and the combined mass of dry steam & mass of water in the mixture. It is denoted by x.

\(Dryness\;fraction\;\left( x \right) = \frac{{mass\;of\;vapour\;\left( {{m_v}} \right)}}{{mass\;of\;vapour\;\left( {{m_v}} \right) + mass\;of\;liquid\;\left( {{m_l}} \right)}}\)

For saturated liquid x = 0

For saturated vapour = 1

The value of the dryness fraction lies between 0 and 1.

Note:

The term quality is used in the wet vapor zone and is of no significance in superheated or compressed liquid regions.

Heating of dry steam above saturation temperature is known as Superheat.