Dehumidifiers

Overview

Engineering reference data for Dehumidifiers 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

Types of Dehumidifiers

Dehumidification devices can be classified into three main categories based on their operating principle.

Absorption Dehumidifiers

In an absorption dehumidifier, moisture is extracted using a sorbent material. The sorbent contains a vast number of microscopic pores where water is absorbed. When the sorbent becomes saturated, it can be regenerated with hot air.

Key characteristics:

• Intermittent process requiring more complicated control of air flow
• Requires periodic regeneration cycle

Spray Dehumidifiers

An air washer or spray dehumidifier can be used as long as the water temperature remains lower than the dew point of the air flow. The air is dehumidified when moisture in the air condenses on the surface of the sprayed water.

Refrigeration Dehumidifiers

In a refrigeration dehumidifier, the air flow passes over a cooled surface where some of the moisture in the air condenses. The surface or coil is cooled by a refrigeration unit.

Dehumidifier Comparison

References

• Original Source