Maximum Moisture Content Air

Overview

Engineering reference data for Maximum Moisture Content Air in air psychrometrics.

Key Formulas

Humidity Ratio

$\omega = 0.622 \frac{P_v}{P_a}$

Mass of water vapor per mass of dry air.

Relative Humidity

$\phi = \frac{P_v}{P_{vs}} \times 100\%$

Ratio of actual to saturation vapor pressure.

Wet Bulb Temperature

$T_{wb} = T_{db} - \frac{P_{vs} - P_v}{\gamma}$

Temperature measured by wet-bulb thermometer.

Enthalpy of Moist Air

$h = c_p T + \omega h_g$

Sensible + latent heat per unit mass of dry air.

Variables

Air Moisture Capacity Data

Moisture Carrying Capacity Increase

The percentage increase in moisture carrying capacity when air is heated can be calculated as:

$\Delta\% = \frac{\rho_{w,T_2} - \rho_{w,T_1}}{\rho_{w,T_1}} \times 100\%$

where $\rho_{w,T_1}$ and $\rho_{w,T_2}$ are the maximum water content (g/m³) at the initial and final temperatures respectively.

Example: Heated Air for Drying

When air is heated from 20°C to 50°C:

• At 20°C: $\rho_{w,20} = 17.3 \text{ g/m}^3$
• At 50°C: $\rho_{w,50} = 83.0 \text{ g/m}^3$

$\Delta\% = \frac{83.0 - 17.3}{17.3} \times 100\% = 380\%$

This dramatic increase in moisture holding capacity explains why heated air is significantly more effective than cold air in industrial drying processes.

Interactive Charts

References

• Original Source