Saturated steam pressure temperature relationship of water

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saturated steam pressure temperature relationship of water

A new formula for saturated water steam pressure within the temperature range − 25 to °C. Authors; Authors and affiliations. N. P. Romanov. In the case of H2O, the terms ice, water and steam are used to denote the three The relationship between the saturation temperature and the pressure is. Pressure – temperature relation for saturated steam. working pressure, saturated steam temperature. [bar], [PSI], [°C], [°F]. 1, 14,5, ,4, ,9. 2, 29, ,7,

saturated steam pressure temperature relationship of water

Radiant heat loss causes some of the steam to condense. The generated wet steam thus becomes even more wet, and condensate also forms, which must be removed by installing steam traps at appropriate locations. Heavy condensate that falls out of the steam flow can be removed through drip leg steam traps. However, the entrained wet steam will reduce heating efficiency, and should be removed through point-of-use or distribution separation stations Steam that incurs pressure losses due to piping friction, etc.


When steam is generated using a boiler, it usually contains wetness from non-vaporized water molecules that are carried over into the distributed steam. As the water approaches the saturation state and begins to vaporize, some water, usually in the form of mist or droplets, is entrained in the rising steam and distributed downstream. This is one of the key reasons why separation is used to dis-entrain condensate from distributed steam.

Superheated Steam Superheated steam is created by further heating wet or saturated steam beyond the saturated steam point. This yields steam that has a higher temperature and lower density than saturated steam at the same pressure. Advantages of using superheated steam to drive turbines: To maintain the dryness of the steam for steam-driven equipment, whose performance is impaired by the presence of condensate To improve thermal efficiency and work capability, e.

Vapour pressure of water - Wikipedia

It is advantageous to both supply and discharge the steam while in the superheated state because condensate will not be generated inside steam-driven equipment during normal operation, minimizing the risk of damage from erosion or carbonic acid corrosion.

In addition, as the theoretical thermal efficiency of the turbine is calculated from the value of the enthalpy at the turbine inlet and outlet, increasing the degree of superheating as well as the pressure raises the enthalpy at the turbine inlet side, and is thereby effective at improving thermal efficiency.

Disadvantages of using superheated steam for heating: Water In the liquid phase, the molecules are free to move, but are still less than one molecular diameter apart due to mutual attraction, and collisions occur frequently. More heat increases molecular agitation and collision, raising the temperature of the liquid up to its boiling temperature. The enthalpy of all other states can then be identified, relative to this easily accessible reference state. Sensible heat was the term once used, because the heat added to the water produced a change in temperature.

Types of Steam

However, the accepted terms these days are liquid enthalpy or enthalpy of water. It is from these figures that the value for the specific heat capacity of water Cp of 4. Steam As the temperature increases and the water approaches its boiling condition, some molecules attain enough kinetic energy to reach velocities that allow them to momentarily escape from the liquid into the space above the surface, before falling back into the liquid. Further heating causes greater excitation and the number of molecules with enough energy to leave the liquid increases.

As the water is heated to its boiling point, bubbles of steam form within it and rise to break through the surface. Considering the molecular arrangement of liquids and vapours, it is logical that the density of steam is much less than that of water, because the steam molecules are further apart from one another. The space immediately above the water surface thus becomes filled with less dense steam molecules. When the number of molecules leaving the liquid surface is more than those re-entering, the water freely evaporates.

At this point it has reached boiling point or its saturation temperature, as it is saturated with heat energy. If the pressure remains constant, adding more heat does not cause the temperature to rise any further but causes the water to form saturated steam. The temperature of the boiling water and saturated steam within the same system is the same, but the heat energy per unit mass is much greater in the steam.

Econosto Saturated steam tables by pressure

However, if the pressure is increased, this will allow the addition of more heat and an increase in temperature without a change of phase. Therefore, increasing the pressure effectively increases both the enthalpy of water, and the saturation temperature.

The relationship between the saturation temperature and the pressure is known as the steam saturation curve see image below. Water and steam can coexist at any pressure on this curve, both being at the saturation temperature. Steam at a condition above the saturation curve is known as superheated steam: Temperature above saturation temperature is called the degree of superheat of the steam.

saturated steam pressure temperature relationship of water

Water at a condition below the curve is called sub-saturated water. If the steam is able to flow from the boiler at the same rate that it is produced, the addition of further heat simply increases the rate of production. If the steam is restrained from leaving the boiler, and the heat input rate is maintained, the energy flowing into the boiler will be greater than the energy flowing out.

This excess energy raises the pressure, in turn allowing the saturation temperature to rise, as the temperature of saturated steam correlates to its pressure. Enthalpy of evaporation or latent heat hfg This is the amount of heat required to change the state of water at its boiling temperature, into steam.

The old term latent heat is based on the fact that although heat was added, there was no change in temperature. However, the accepted term is now enthalpy of evaporation. Like the phase change from ice to water, the process of evaporation is also reversible.