Cooling influence

Cooling devices could soon be available as an alternative to fans in laptop computers. They could even be placed in handheld electronic equipment too small for fans, such as mobile phones.

Georgia Institute of Technology spin-out company Innovative Fluidics has developed technology that it claimed can be used to provide highly efficient air cooling of processors at a fraction of the flow rate of traditional fans. The firm said that its SynJets devices could be used to cool laptops, PDAs and mobile phones.

Based on research carried out by Prof Ari Glezer of the School of Mechanical Engineering at the institute, SynJets work using an air-puffer powered by an inaudible vibrating membrane (150Hz).

Jon Goldman of Innovative Fluidics, explained how a vortex is created at every push stroke of the membrane. This vortex, he said, promotes good mixing of air and breaks up the boundary layer that is typically attached to each fin of the heatsink. Goldman added that though the devices operate at a considerably lower flow rate than a fan they nevertheless result in a very high heat transfer coefficient. While patent status prevented Goldman specifying the material used to make the membrane, he said that research has focused on loudspeakers and piezoelectrics.

The SynJet mechanism means that they can be built in a variety of different shapes and, most usefully, designed in a very flat profile. So the devices aren’t limited to the circular shape required by a fan.

Though reticent on the prospect of his technology replacing fans, Goldman believes Synjets could have potential where shape and profile militate against the use of fans. ‘There is the potential that in certain applications this technology could have some superior performance to fans particularly from a shape and noise point of view,’ he said.

However, in other applications he cited, the technology did seem more like an alternative to the fan. For example, in the case of laptop computer memory modules he explained how manufacturers go to some pains to route the fan internally and blow it over the memory module: ‘It isn’t particularly efficient. We’ve made Ritz Cracker-sized devices that will fit in the gap between the memory module and the bottom of the laptop and blow enough to do the job.’

Ian Mcleod, of Papst, a company that fits fans into every imaginable type of grey box, isn’t convinced that the tried-and-tested supremacy of the fan is under serious threat, however.

‘Fans are cheap, usable and last for a long time. There have been all sorts of alternatives suggested, but I don’t think that fans are under threat in computers because they’re always going to be cheaper. Why put £3-worth of cooling in there if you don’t need to?’ he said.

In other applications, Goldman said that the technology could be used alongside fans. In fact, the company has already investigated this possibility. ‘We had a case where there was a set-top box and it was crunching so many MIPS [millions of instructions per second] that it needed two pretty big case fans. We replaced them with one, directed it with a SynJet and got 24 per cent better performance – and it was quieter,’ he said.

Goldman said that Innovative Fluidics is confident that SynJets will be no more expensive to make than the equivalent fans.

He believes that following further tests the first prototype is probably about 12 months away. ‘We’re talking to a number of firms looking at using SynJets for cooling lasers, laptop batteries and LCD projectors,’ he said.

In an alternative cooling development, NEC recently announced the development of a prototype cooling module for notebook PCs. This features a slimline piezoelectric pump, where vibration pushes out coolant. The unit also makes simultaneous use of a water-cooled heatsink and a cooling fan. This method strikes a balance between lowering noise and achieving a required cooling capacity. NEC said that it aims to commercialise the module within two years.