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The pressure in a mixture of dry air and water vapor - humid or moist air - can be estimated by using Daltons Law of partial pressures.
Daltons Law states that
- the total pressure of a mixture of gases is equal to the sum of the partial pressures of the constituent gases
The partial pressure is the pressure each gas would exert if it alone occupied the volume of the mixture.
Daltons Law of partial pressure for moist air can be expressed as
p = pa + pw (1)
p = total pressure of air (Pa, N/m2)
pa = partial pressure dry air (Pa, N/m2)
pw = partial pressure water vapor (Pa, N/m2)
With the partial pressure for dry air and water vapor (1) can be modified to:
p = ρa286.9T + ρw455T (2)
ρa = density of air (kg/m3)
ρw = density of water vapor (kg/m3)
- Moist and humid air - psychrometric charts, Mollier diagrams, air-condition temperatures and absolute and relative humidity and moisture content.
- Dry air is a mechanical mixture of nitrogen, oxygen, argon and several other gases in minor amounts.
- Relative humidity in moist air can estimated by measuring the dry and wet bulb temperature.
- Maximum water content in humid air vs. temperature.
- The moisture holding capacity of air increases with temperature.
- Air in the steam will lower the surface temperatures in heat exchangers - and less heat will be transferred.
- Pressure, temperature and volume in a perfect ideal gas like moist air (air with water vapor).
- Humidity ratio of moist air to humidity ratio of saturated moist air.
- Density of moist air vs. pressure ranging 75 - 1000 mmHg.
- Density of the mix of dry air and water vapor - moist humid air.
- Sensible and latent heat of moist air.
- Psychrometric table with humid air properties like saturation pressure, specific volume, enthalpy and entropy.
- Relative humidity in moist air is the ratio of partial vapor pressure to air pressure.
- Specific volume of moist air is defined as the total volume of humid air per mass unit of dry air
- Saturation pressure of water vapor in moist air vs. temperature.
- Weight of water vapor in air
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