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The Antoine equation is a class of semi-empirical correlations describing the relation between vapor pressure and temperature for pure substances. The Antoine equation is derived from the Clausius–Clapeyron relation. The equation was presented in 1888 by the French engineer Louis Charles Antoine (1825–1897). [1]
e * is the saturation water vapor pressure T is the absolute air temperature in kelvins T st is the steam-point (i.e. boiling point at 1 atm.) temperature (373.15 K) e * st is e * at the steam-point pressure (1 atm = 1013.25 hPa) Similarly, the correlation for the saturation water vapor pressure over ice is:
As wet steam is heated further, the droplets evaporate, and at a high enough temperature (which depends on the pressure) all of the water evaporates and the system is in vapour–liquid equilibrium. [5] When steam has reached this equilibrium point, it is referred to as saturated steam.
The values were not computed according formulas widely used in the US, but using somewhat more exact formulas (see below), which can also be used to compute further values in the appropriate temperature ranges. The saturated vapor pressure over water in the temperature range of −100 °C to −50 °C is only extrapolated [Translator's note ...
Row 3. Values of the five parameters for the first C p equation; temperature limit for the equation. Row 4. Values of the five parameters for the second C p equation; temperature limit for the equation. Row 5. Values of the five parameters for the third C p equation; temperature limit for the equation. Row 6. Number of H T - H 298 equations ...
The quantitatively described steam quality (steam dryness) is the proportion of saturated steam in a saturated water/steam mixture. In other words, a steam quality of 0 indicates 100% liquid, while a steam quality of 1 (or 100%) indicates 100% steam. The quality of steam on which steam whistles are blown is variable and may affect frequency.
The atmospheric pressure boiling point of a liquid (also known as the normal boiling point) is the temperature at which the vapor pressure equals the ambient atmospheric pressure. With any incremental increase in that temperature, the vapor pressure becomes sufficient to overcome atmospheric pressure and cause the liquid to form vapor bubbles.
Unless the pressure and temperature reach supercritical levels in the boiler, the temperature range over which the cycle can operate is quite small. As of 2022, most supercritical power plants adopt a steam inlet pressure of 24.1 MPa and inlet temperature between 538°C and 566°C, which results in plant efficiency of 40%.