HUMIDITY CONTROL
are known in advance, a ducted solution is generally the simplest choice to manage, and can be correctly sized during the second stage of design, called ‘Requirements definition and planning’. In order to accommodate a humidification system that meets the requirements of high efficiency, the ducting must have suitable features, determined in the design stage, when it is still possible to adapt the configuration of the AHU. Ducted humidification allows easier management and maintenance than direct humidification. When relative humidity is underestimated
or neglected in stage two of AHU design, problems will occur in the fourth stage, called “Performance monitoring”. A retrofit solution will thus be required. In these cases, it is usually advisable to opt for an in-room humidification system, so as to reduce the cost of investment and avoid having to carry out major work on the existing HVAC system, which moreover may often not be suitable for traditional ducted humidification.
All in-room humidification solutions feature a distribution system for delivering steam (isothermal system) or droplets of water (adiabatic system), which may include the use of blowers or be directly incorporated into the humidifier. In both cases, suitable free space must be provided near the distribution system to avoid condensation. The design stage is crucial for correct evaluation of the humidification load, the choice of the humidifier and the position of the distribution system in the points where most required. The chosen solution is always a compromise between technical performance, surrounding conditions and return on investment. Special attention must be paid to the specific application, to the free heights available, to the presence and location of people in the air-conditioned space and to the existing air-conditioning and distribution system.
Isothermal humidifiers (heaterSteam, gaSteam, humiSteam, compactSteam) feature high energy consumption, however can be installed in spaces with low free heights, as the steam generated is easily absorbed by the surrounding air. Furthermore, hygiene is guaranteed without the use of additional systems.
Adiabatic solutions on the other hand, require
on average more free space to guarantee complete evaporation of the droplets of water, however feature lower energy consumption and can partially cool internal thermal loads (1 l of evaporated water has an equivalent cooling
capacity of 690 W), thus saving on the air- conditioning system. In the industrial applications mentioned above, where cost reduction, time to market, final product quality and energy saving requirements are increasingly demanding, humidity control is essential to ensure continuity of the business. In older facilities that undergo renovations and upgrades to meet market requirements, direct humidification plays a key role. In commercial applications, on the other hand, in-room humidification is adopted to ensure comfort for a limited investment.
www.acr-news.com
September 2020 39
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