Steam & Condensate Introduction
Pressure / Temperature Relationship of Steam Steam is created when water is heated to its boiling temperature until enough heat energy is absorbed to transform the water from a liquid to a gas. The temperature at which water boils is 212˚F; however, this is the boiling point of water at 0 psig, or atmospheric pressure. A unique property of steam is that there is a direct relationship between the pressure at which it is generated and the temperature at which it boils.
The boiling temperature increases as steam pressure increases. If steam is generated at a pressure higher than 0 psig, the temperature at which the water boils will be higher than 212˚F. An abbreviated version of the Saturated Steam Table is included to show the exact boiling temperature at various steam pressures. (The complete steam table is available in Engineering Section.)
Temperature (˚F )
Steam Pressure (psig)
Steam
Boiling Water
0 psi = 212˚ F 1 psi = 215˚ F 4 psi = 224˚ F 10 psi = 239˚ F 50 psi = 298˚ F 100 psi = 338˚ F 150 psi = 366˚ F 200 psi = 388˚ F 300 psi = 421˚ F
212˚ F 215˚ F 224˚ F 239˚ F 298˚ F 338˚ F 366˚ F 388˚ F 421˚ F
Where else is steam used? Hospitals and pharmaceutical manufacturers may use steam for the sterilization of medical instruments and production of medicines, while the petrochemical industry may use steam for processing gasoline from crude oil. Steam is essential in large scale food processing & manufacturing applications. Large cities, such as New York, have centralized steam systems for heating large apartment complexes. Heating Properties: The energy absorbed by water at its boiling point to transform it from a liquid to a gas is known as Latent Heat . This Latent Heat is then released by the steam when used for heating. Steam is very efficient in transferring heat to other processes. Steam, being a gas, allows it to surround any surface it needs to transfer its heat energy into. When steam transfers its heat, it condenses back into water, which will be drained away and sent back to the boiler in order to be used again (referred to as Condensate Recovery). Steam Supplies Heat at a Constant Temperature Steam does not reduce its temperature when it releases its heat; it just simply changes from a gas back into water at the same temperature. For example, steam at 50 psig (is at 298˚F; refer to steam chart above) will condense back to water at 298˚F when it releases its heat energy. In contrast to steam, water reduces in temperature when it gives up its heat. What is saturated steam? Steam that is generated under pressure inside the boiler, while in the presence of boiling water, is referred to as Saturated Steam . If additional heat is later added to the saturated steam to increase its temperature, it is then referred to as Superheated Steam. Superheated steam is used in power generation and saturated steam is used for heating. When saturated steam releases its energy, it condenses back to water. This hot water at or near boiling tem- perature is referred to
Steam Turbines in Power Plants
Steam exhaust from power plants
Steam used in cities for heat
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