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# Moist Air - Specific vs. Relative Humidity

Humidity is the quantity of water vapor present in air. It can be expressed as an absolute, specific or a relative value.

If we know the relative humidity of the moist air and the water vapor density and the density of the air, the specific humidity can be expressed as:

x = 0.622 φ ρws / (ρ - ρws) 100%                               (1)

where

x = specific humidity (humidity ratio) of air vapor mixture (kgh2o/kgdry_air)

φ = relative humidity (%)

ρws = density of water vapor (kg/m3)

ρ = density of the moist or humid air (kg/m3)

## Related Topics

### • Air Psychrometrics

Moist and humid air - psychrometric charts, Mollier diagrams, air-condition temperatures and absolute and relative humidity and moisture content.

## Related Documents

### Air - Absolute Humidity

Absolute humidity is the actual mass of water vapor present in the air water vapor mixture.

### Air - Humidity Ratio

The mass of water vapor present in moist air - to the mass of dry air.

### Humid Air vs. the Ideal Gas Law

Pressure, temperature and volume in a perfect ideal gas like moist air (air with water vapor).

### Mixing of Humid Air

The change in state wwhen mixing moist air - enthalpy, heat, temperature and specific humidity.

### Moist Air - Density vs. Water Content and Temperature

Density of the mix of dry air and water vapor - moist humid air.

### Moist Air - Enthalpy

Sensible and latent heat of moist air.

### Moist Air - Properties

Psychrometric table with humid air properties like saturation pressure, specific volume, enthalpy and entropy.

### Moist Air - Relative Humidity

Relative humidity in moist air is the ratio of partial vapor pressure to air pressure.

### Moist Air - Specific Volume

Specific volume of moist air is defined as the total volume of humid air per mass unit of dry air

### Recommended Relative Humidity

Recommended relative humidity level.

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