Feature Thermal management
Cool solutions for thermal management
A cooler environment within an enclosure can help prevent expensive equipment overheating. Here, Axair Fans takes a look at points to consider when selecting a fan and filter unit for your enclosure
W
hile failing to provide active ventilation is the main cause of failure within electrical cabinets – as it results in expensive equipment over- heating – many believe that the financial outlay of installing a fan is a cost that can be cut. However, the cost of a fan unit is practically inconsequential when compared to the cost of the equip- ment, labour and time needed to replace a component such as an inverter, for example. Not only that but a cooler operating environment significantly increases the lifespan and energy efficiency of equipment, as will protection from dust and water splashes (IP54).
A solution can be found in a com- bined fan and filter unit. These are designed to provide cooling air that is free of both dust and splashed water and, when required, shield against EMC/RFI emissions.
Selecting the right fan
Fan selection does not have to be as expensive and complicated as some believe. The main points to consider are the maximum ambient tempera- ture, the temperature that the equip- ment needs to be kept below, and the equipment heat loss figures. The latter can be obtained from the equipment instructions.
A simple equation can then be used which takes into account the air den- sity and then determines the required air volume flow rate.
V = 3.1 x Kw ΔT
V = 3.1 x 1200 15
Example: 3.1m3 x (1200W/15˚C ) = 248m3/h required airflow. 38
V = Volume required kW = Watts dissipation/heat loss
ΔT = Allowable temperature increase inside the cabinet
The FPF, FF and GF fan filter units feature chevron louvred panels to aid in the reduction of water and dust
Our air density figure of 3.1m3 is based on an altitude figure of between 1-100m above sea level. The higher the altitude, the larger the volume of air is required. Air density, it should be noted, will increase as tempera- tures decrease, therefore a better cooling effect will be realised.
Filtering choice
Installation time can be speeded up by using a ‘click-fit type’ of fan filter unit, which requires no tools. The fitted fans should be of a ball bearing construction, and the cover should be easy to remove to access the filter media. If the mechanism is not straightforward then the filter might not get changed, resulting in problems in the long run.
Three ranges of fan filter types are available from Axair – FPF, FF and GF by Fandis – and these feature chevron louvred panels to aid in the reduction of water and dust. Sizes range from 105mm to 325mm square, with the largest capable of filtering air at a rate of 660cu.m/h. In a standard fan filter unit the fan sucks air into an enclo- sure, first through the louvre, then the filter. Warmed air then exits, through a filtered louvre, generally of the same dimensions as the inlet but larger if necessary to improve the flow rate. Compact and quick to mount the FPF series has a low external profile and is of the click-fit mounting type. An integrated sealing gasket also provides secure dust and water protection. When space inside an enclosure is precious, adaptors are available for certain sizes which allow the filters to sit in a semi built-in position in the enclosure. This, in turn, reduces the internal dimensions
taken up by the fan filter unit. The GF range has innovative mounting systems with jacks which accommodate both plastic and plate enclosures with thick wall applica- tions. The FF fan filter, meanwhile, is the latest series offered by Axair. This also has a fast mounting tool-less system which allows the unit to be easily clipped onto the enclosure. Each fan filter is simple to fit and available in a variety of standard volt- ages both in AC and DC. Enhanced protection is available to IP55 along with EMC/RFI variants.
The units are available in standard air flow which introduces air in the cab- inet, and reverse air flow which extracts air. Where the required minimum flow rate is not available, a wide range of axial and centrifugal fans are available. In extreme cases it is possible to take a high performance fan and use it in conjunction with a number of standard filters, sized to achieve the ideal heat dissipating airflow. Roof mounted units with top covers are available for both indoor and out- door installation. The outdoor models are supplied with weather protection in the form of butterfly shutters that close under gravity during periods of system inactivity.
In some cases it may be necessary to utilise or combine standard products to make special solutions, and Axair Fans also offers an exten- sive range of thermal management equipment for electronic and electrical enclosures. These include standard and changeover thermostats, hydrostats, PTC heaters and lights.
Axair Fans T: 01782 349430
www.axair-fans.co.uk OCTOBER 2012 Design Solutions Enter 225
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