Air humidification technologies
One goal, different routes:
Air humidification technologies
Different systems and technologies are applied in practical applications to ensure adequate humidity: Nozzle atomisers, steam humidifiers, ultrasonic atomisers and evaporators are often used as functional principles and utilised in central air humidification systems as well as in direct room humidification. DRAABE has specialised in direct air humidification and mostly uses nozzle systems with high-pressure and compressed air technology. The various systems differ in terms of energy consumption, maintenance costs and humidification capacity.
1. Nozzle air humidification
In nozzle air humidification systems a distinction must be made between high-pressure and compressed air nozzle atomisers.
During high-pressure nozzle air humidification water is pressurised (85 bar) with a high-pressure pump. Water is transported directly to the humidifiers via high-pressure hoses (one-substance-process). It is then atomised with special high-pressure nozzles, micro-fine and virtually silent. Furthermore, high-pressure nozzle atomisers consist of a control unit and require water treatment.
In these nozzle systems the water is being atomised with compressed air. Compressed air and water are fed into the humidifier separately (two-substance-process). This long-established technology is economical, especially for smaller production areas (up to approx. 4000 m3) and is suitable for applications with lower requirements on droplet size and operating noise.
2. Steam humidifier
Evaporators produce steam in a temperature stable plastic or stainless steel cylinder, where humidifier water is heated to 100°C. Steam humidifiers are divided into three types: Electron beam, resistance and gas evaporators. The heating in the frequently used electrodes and resistance evaporators is done with electrical energy, which is why the electrical power consumption is very high.
Evaluation: The steam humidifiers operate with low-noise, but have high energy consumption. Steam cylinders have a limited service life because of lime deposits.
3. Ultrasonic humidifier
During ultrasonic humidification the water is excited to high-frequency oscillations by piezoelectric crystal elements, which makes water escape in the form of a cold fog. The resulting aerosol is transported into the room by normal air flow.
Evaluation: The advantage of ultrasonic humidifiers is in their low energy consumption. An opposing fact is however that there is a large risk of contamination because of the constantly moist surfaces. Mineral deposits will also limit the service life of the ultrasonic oscillators. Furthermore, they require fully demineralised water and regular inspection and cleaning of the atomisers.
In the case of evaporators, the humidifying water is distributed on a contact body, or the contact body is saturated, to create a large surface for the evaporation process. A fan pushes the room air through the contact body. The humidification process takes place by evaporation on the surface of the contact body. Fixed devices are connected to the water supply. The contact body may be fixed or rotating.
Evaluation: Evaporators have only low energy needs, but also have a big risk of contamination of the continually wet surface and also require regular inspection and cleaning.
On the basis of VDI 6022 Sheet 6 the use of small portable devices is not allowed at the workplace for precautionary reasons, unless the user can provide comprehensible proof of risk-free operation.
Even decorative water powered devices (such as water walls, fountains) may bear hidden risks of stressing the respiratory system through contaminated water, unless they are properly supplied, cleaned and maintained. Special inspection and measures are therefore required for risk-free operation.
Evaluation of the humidification systems
In comparing the various humidification systems, we need to look at the operating costs, the technical equipment and also the service offerings carefully and in detail. In the interest of a high level of health protection and comprehensive operating safety, systems with integrated water treatment and a sustainable maintenance concept are preferable.
One very important decision point in the selection of a suitable air humidification system is the VDI certificate. The user of a system certified in this way does have the security of operating a low-maintenance, economical and hygienic system.