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SynJets for Forced Air Cooling for Outdoor Telecom Equipment
Keywords: Telecom Equipment, Outdoor Operation, SynJets Forced Air Cooling
With an explosion in the number of mobile device users, the need for increased performance from wireless telecom equipment such as Remote Radio Units or Active Antennas has grown rapidly, creating significant thermal challenges in infrastructure equipment. Conventionally, outdoor telecom equipment is cooled with big heat sinks designed for natural convection. However, with increased power demands, these heat sinks are too big and heavy and thermal designers are being forced to consider forced air cooling, but the stringent reliability requirements make it undesirable to use conventional fans. This paper describes an air cooling technology called SynJets that provides an alternative approach for meeting the increasing thermal needs of the telecom industry. A SynJet is an intense, small-scale turbulent jet synthesized directly from the fluid in which it is embedded. The jet is formed when fluid is alternately entrained and ejected from the cavity by the motion of a diaphragm bounding the cavity, so that there is no net mass addition to the system but a positive momentum flux in the direction of the jet. The zero-mass flux nature of the jet precludes the need for input piping or complex fluidic packaging. The high momentum SynJet flow also creates a jet ejector effect inducing a secondary flow that is several times the mean flow generated by the jet. Some of the key attributes of the technology, including thermal performance, acoustics and power consumption are discussed using test data on large heat sinks of the type are typically seen on RRUs. The use of SynJet cooling can reduce heat sink size and weight by up to 50%. Since SynJet actuators have no moving parts in friction, Synjet reliability is orders of magnitude higher than traditional fans, as demonstrated by accelerated lifetime test data. The presentation discusses the design elements that enable SynJets to survive harsh outdoor environments as well the reliability tests that were performed to ensure compatibility with outdoor equipment.
Raghav Mahalingam,
Austin, TX

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