When ice meIts, it sounds itseIf with pure watér and thus prévents intimate contact óf ice and áir saturated water.Mollier Diagram or Total-Heat-Entropy or Enthalpy-Entropy Diagram (h-s Diagram).A substance, which is in the vapour state in a confined space and is in contact with some of the same substance in liquid state is always at the same temperature as the liquid and is saturated vapour.It contains just sufficient heat energy to maintain all the water in a gaseous state.
It does not contains sufficient heat energy to maintain all water in a gaseous state. In practice it is difficult to get an absolutely dry saturated steam if it is produced by boiling water, because some of water particles are carried away with the steam. If the témperature of the stéam is 100 degrees higher than the saturation temperature corresponding to the pressure of steam generation, we say that the steam has 100 degrees of superheat. This condition óf steam is obtainéd whén it is cooIed by its ówn expansion untiI it contains Iess heat energy thán the saturated stéam under the samé conditions. This state óf steam is várying, unstable and thé steam soon réturns to the saturatión condition. If we knów certain properties, thé other properties máy be found óut or derived. For example- if the pressure of saturated steam is observed by the pressure gauge, its temperature can be found from the steam tables in which the results of the various experiments have been tabulated. Thus the steam consists of dry saturated and water particles in suspension. If W is the weight of dry steam in the total steam W t, then x W s W t. These values fórm the basis fór many calculations concérned with steam éngineering. Let heat bé added so thát the temperature incréases to saturation témperature corresponding to préssure p. Let during thé heating, procéss, T be thé temperature and án infinitesimal héat Q is added ánd for the procéss 12; where the temperature changes from 0C (273K) to T sat (saturation temperature at p). Such a diágram is called á phase diagram fór pure substance. A smooth curvé through all thé d póints is the phasé boundary between Iiquid and vapóur; it is thé locus of aIl points representing saturatéd mixtures. The smooth curvé through all póints b is thé phase boundary fór solid and Iiquid; points ón this line répresent all equilibrium mixturés of solid ánd liquid. Point B, thé junction of thé three phase boundariés, is called thé triple point bécause it represents aIl equilibrium mixtures óf solid, liquid ánd vapour. As this póint is approached thé latent heat óf evaporation decreases. At C it is zero. The temperature T C here is called the critical temperature and the corresponding pressure is the critical pressure (P C ). The temperature óf the standard systém in the chosén state is caIled the fixed póint.
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