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Vapor Steam

Reference data and engineering information about vapor steam for air psychrometrics applications.

vaporsteam

Overview

Engineering reference data for Vapor Steam in air psychrometrics.

Key Formulas

Humidity Ratio

ω=0.622PvPa\omega = 0.622 \frac{P_v}{P_a}

Mass of water vapor per mass of dry air.

Relative Humidity

ϕ=PvPvs×100%\phi = \frac{P_v}{P_{vs}} \times 100\%

Ratio of actual to saturation vapor pressure.

Wet Bulb Temperature

Twb=Tdb−Pvs−PvγT_{wb} = T_{db} - \frac{P_{vs} - P_v}{\gamma}

Temperature measured by wet-bulb thermometer.

Enthalpy of Moist Air

h=cpT+ωhgh = c_p T + \omega h_g

Sensible + latent heat per unit mass of dry air.

Variables

SymbolDescriptionUnit
ω\omegaHumidity ratiokg/kg
ϕ\phiRelative humidity%
PvP_vVapor pressurePa
PvsP_{vs}Saturation vapor pressurePa
TdbT_{db}Dry bulb temperature°C
TwbT_{wb}Wet bulb temperature°C

Types of Vapor and Steam

This section expands on the key definitions related to vapor states.

  • Saturated Vapor: Vapor at the temperature of the boiling point corresponding to its pressure.
  • Wet Saturated Vapor: Carries liquid globules in suspension. It does not follow the general gas law.
  • Dry Saturated Vapor: Free from liquid particles. Any decrease in temperature or increase in pressure will condense liquid out of the vapor. It also does not follow the general gas law.
  • Super-heated Vapor: Exists at a temperature higher than the saturation temperature for its pressure. It cannot contain liquid particles and, within limits, will not condense with an increase in pressure or decrease in temperature. Highly superheated vapors behave approximately like ideal gases.
  • High Pressure Steam: Steam with pressure significantly above atmospheric pressure.
  • Low Pressure Steam: Steam with pressure less than, equal to, or not greatly above, atmospheric pressure.

Saturated Steam Properties Reference

Detailed property tables for saturated steam are essential engineering references for thermodynamic calculations. These tables list properties such as temperature, pressure, specific volume, enthalpy, and entropy for both the saturated liquid and saturated vapor states.

The Engineering Toolbox provides comprehensive saturated steam tables in both imperial and SI units. These tables are critical for process design involving boilers, condensers, and turbines.

For complete property data, refer to the standard Saturated Steam Tables - Imperial Units and Saturated Steam Tables - SI Units from reliable engineering references.

References

Source: engineeringtoolbox.com