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Air handling Units: It's good news for those who exercise control

The growth in technology is good news for close control applications says Joe Wieckowski, general sales manager for Colman Moducel
Air handling Units: It
THE demand for close control applications has kept pace with developments in technology as it provides a solution for a wide range of applications and industries, that all share a common requirement: the control of air quality and/or humidification to within specific tolerances.

Close control was generally applied to industry where the provision of temperatures and humidity conditions are critical for a given application. Although associated with computer rooms and data processing centres, in reality close control is widely used across a wide range of industries.

The growth in technology usage and its increasing presence in office environments, combined with health and safety issues, has fuelled a demand for strict control of humidity and temperature in the work place too. Little wonder then that the future for close control air conditioning has never looked brighter.

There are no hard and fast rules governing acceptable working conditions but good design criteria ensures that the comfort and well-being of a building and its occupancy is between 19-230C with 45 to 55% relative humidity.

Comfort air conditioning systems provide and maintain comfortable working environments for people. They provide cooling or cooling and heating functions together with basic air filtration within the occupied space.

Close control systems on the other hand maintain the desired environment for products, processes and equipment. Personal comfort is not the primary concern.

Most close control applications require full control over dry bulb temperature and humidity levels independently of each other. Air filtration standards are also normally higher than those found in comfort systems.

Modern technology

Close control equipment is often required to operate for 24 hours a day, 365 days per year. As a result manufacturers, ever wary of environmental considerations. design more energy efficient systems and take advantage of all that modern technologies can offer.

There are four key functions that need to be controlled in close control critical area applications; heating, de-humidification, dry bulb cooling and humidification.

Close co-operation between the designer and owner of the building and/or process is critical to meet the desired environmental conditions. Determining the heating and cooling loads from the outset establishes the systems' capacity requirements. Cooling loads and humidity requirements are used to size air-conditioning (comfort and process cooling) systems.

In other systems, heating and/or ventilation may be the critical factors in sizing and selection and there will be further choices to make depending on the building and whether it is new or a refurbishment project.

Looking at a close control project in its entirety will determine whether an installation meets the required specification. For example, evaluating how changes to one part of a system will affect another or how a change in one system will affect another system's performance. All too frequently, kit is installed on an adhoc basis over time resulting in a grossly inefficient and costly system.

The largest and most obvious market for close control is the telecommunications and computing sectors. The positive advances of technology is tempered with the heat the equipment generates and heat loads in excess of 3kW/m3 are not uncommon.

There are plenty of other critical area applications that afford many opportunities including museums and repository facilities that require specific conditions for the storage of works of art, artefacts and photographic records. Without special handling and storage conditions, these materials would rapidly deteriorate.

The printing and textile industries, reliant on temperature sensitive inks, require specific humidity levels to prevent manufacturing and material handling problems. Trackside communications facilities as used by Network Rail and other operators require cooling to prevent internal equipment from overheating.

The food industry relies on close control equipment to comply with safe preparation, storage and retailing of food.

Tightest control

In such cases dual function ceiling cassettes providing air conditioning with temperatures as low as 100C are ideal. Low humidity conditions are also desirable in open chilled food cabinet display areas within supermarkets and products such as sacrificial humidifiers can address this.

Of all the applications, clean rooms, laboratories, quality control and material test rooms probably require the tightest control. Temperature and humidity control is crucial in many manufacturing quality and testing environments where tolerance of ±0.50C dB and ±1% RH are common.

Health care environments also depend on close control installations. Units are used in MRI and CAT scanners to cool water to ±0.50C.

The possibilities are endless and ensure that the market for close control is much in demand.
1 May 2007


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