HUMIDITY CONTROL Advanced humidity control
High performance humidity control has a vital role in a vast range of applications and industrial processes. Terry Stevens-Smith, director - national accounts at Watkins Hire, highlights the main approaches and how the technology works.
T
he range of applications requiring effective humidity control is vast, extending from the construction industry and IT sector, to pharmaceuticals, waste treatment, process manufacturing and the offshore oil and gas industry.
Humidity is something of a wild card in terms of air treatment. While the gaseous composition of air is practically the same everywhere, the amount of water vapour it contains varies greatly depending on geographical location, weather conditions and local factors in the immediate vicinity. Airborne moisture is highly active chemically, biologically and thermodynamically. It also plays an important role in determining the electrostatic properties of air. As a result, moisture levels have a direct influence on metal corrosion, mould growth, the behaviour of powders, the quality of surface treatments, and the stability of hygroscopic products such as drugs and confectionery.
As a result, for many industrial applications the level of humidity is a critical factor influencing the resultant quality of a product or industrial process, and significant investment may depend on its effective control.
Fortunately, humidity levels in air can be controlled in a
number of ways. The particular technology of choice will depend on the precise temperature and humidity conditions required in the application, and the scale and rate of moisture removal involved.
The simplest method of dehumidification is condensation through mechanical cooling. This involves drawing moist air over a refrigeration coil, in the process cooling it to below the dew point. Condensed moisture is collected in a drain pan or holding tank and disposed of or reclaimed for a secondary use.
Cooling-based dehumidification is suited to relatively small scale applications, where ambient temperatures are relatively high. For larger scale applications, and where ambients and relative humidity are low, other more powerful approaches are required.
Desiccant dehumidification systems are designed for use in such higher volume, higher intensity applications. A desiccant dehumidifier operates on a different principle to a refrigerant-based unit, harnessing the properties of hygroscopic chemicals to adsorb moisture from the air, and then give it up in a regenerative process.
The main benefit of desiccant dehumidifiers is that they
50 September 2017
www.acr-news.com
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