Moisture is the water vapor carried by the air. In the fight against moisture, definitions of absolute humidity and proportional humidity should be known and evaluated on psychometry.
The mass amount of water vapor that is carried within 1 m³ of air is defined as absolute humidity and the maximum amount of water vapor it can carry is defined as saturation point. Relative humidity is the maximum moisture content that the moisture in the air will carry under certain conditions.
Psychometry is the science of moist air. Psychometry examines the amount of water vapor in the air and examines its thermodynamic properties such as temperature, pressure, humidity, and enthalpy.
The psychometric diagram is prepared depending on the altitude above the sea level which is accepted as the atmospheric pressure of the region where it is used. To protect the material in industrial facilities and all material warehouses, mold, corrosion and so on. Moisture control is essential to avoid damages.
The requirement for favorable climatic conditions is usually relative humidity. The main objective is to keep the relative humidity at a certain level, no matter how many degrees the ambient temperature. Examples of storage and manufacturing site humidity conditions for some general applications are given below.
• 45% for metal materials
• Electronic goods 40%
• Pharmaceutical production 5-45%
• Military ammo storage 45%
Drying Systems
When designing dehumidification systems, the data such as moisture content of the air, enthalpy (temperature change under constant pressure of the system), dry and wet thermometer temperatures, relative humidity are seen on the psychrometric diagram, to calculate dew point, condensation, hidden heat, etc. It is possible to see graphically in the diagram.
Dehumidification by Cooling on Cold Surface
If the air is cooled below the dew point, its ability to retain moisture decreases and the water vapor in the air begins to condense and decomposes into water. In this way, excess moisture is removed from the cooled air and heated to ambient air temperature and fed back into the environment.
Generally, such systems are defined as compressor dehumidification systems containing refrigerant cycles. All equipments of the cooling cycle are designed by including them in the system.
The air passing through the evaporator is cooled below the dew point, the air is dehumidified, the dry thermometer temperature is increased through the condenser. In this way, the relative humidity and absolute humidity of the process air can be reduced.
This dehumidification system is suitable for applications with high relative humidity and dry thermometer temperature. It is not suitable for use in cold climates with high humidity.
Desiccative-Evaporative Dehumidification Systems (Absorption Dehumidification)
Main function of desiccant dehumidification is to keep the water vapor molecules in the moist air in the labyrinths of the carrier materials (adsorbents) and to give the dried air to the environment. Silica gel is generally used as desiccant. Silicon gel filled rotors are used in absorption dehumidification units.
The rotor filler divided into two chambers is rotated at a speed of 5 to 25 revolutions per hour. 75% of the rotor fill is used for adsorbtion and the other 25% is used for desorbtion. Continuous rotation of the rotor ensures the continuity of the dehumidification process and the desired humidity level.
The water molecules captured in the silica gel labyrinths in the rotor evaporate with the hot air blown in the discharge section. Desiccant method dehumidification systems can be used in high and hot climatic conditions, as well as in high and cold climatic conditions.
This feature provides the advantage of application flexibility compared to the dehumidification system on cold surfaces.
Çiğdem Arslan - Proje ve Satış Direktörü - Project and Sales Director - Rolax
