The Relationship Between Boiler Steam Pressure And Temperature

Steam is divided into saturated steam and superheated steam.

Under a certain pressure, the steam produced when water boils is called saturated steam. This saturated steam has the saturation temperature in this state. Saturation temperature refers to the temperature that liquid and vapor have when they are in a dynamic equilibrium state, that is, when they are in a saturated state. In the saturated state, the temperature of the liquid and vapor are equal. When the saturation temperature is constant, the saturation pressure is also constant; conversely, when the saturation pressure is constant, the saturation temperature is also constant. As the temperature rises, a new state of dynamic equilibrium will be formed at the new temperature. A certain saturation temperature of a substance must correspond to a certain saturation pressure. The optimal saturation temperature is not a fixed value, it changes with changes in external conditions.

In the saturated state, the specific relationship between pressure and temperature can be found in the “Comparison Table of Saturated Steam Temperature and Pressure”.

Steam Pressure vs Temperature Chart

If the saturated steam continues to be heated, its temperature will rise and exceed the saturation temperature at that pressure. This kind of steam above the saturation temperature is called superheated steam. It can be seen that there is no one-to-one correspondence between the temperature and pressure of the superheated steam. However, the temperature of superheated steam under a certain pressure must exceed the temperature of saturated steam under this pressure. The degree of excess is determined according to the degree of superheat of the steam.

The degree to which the steam is superheated is called the degree of superheat. The degree of superheat is numerically equal to the superheated steam temperature minus the saturated steam temperature at the corresponding pressure. For example, the absolute pressure of the superheated steam is 4MPa, the saturation temperature is 249℃, and the temperature of the superheated steam is 350℃, then the superheat degree is 350℃-249℃=101℃.

The pressure and temperature can be measured through a boiler pressure temperature gauge.