Heat is on for cool technology use
http://www.flightinternational.com/ (22Jul03, 348 words)
Rolls-Royce is to look into using solid-state cooling technology for electronics in its gas turbines, while the US Navy is to study evaporative spray cooling for power supplies.
Gibraltar-based Cool Chips has developed wafer-like discs which use electron tunnelling as the primary cooling mechanism, and R-R is to acquire the rights to use the technology for its electronics cooling needs. Cool Chips says the technology will refrigerate more efficiently than any competing technology and weigh less than 10% of equivalent compressor-based systems.
Thermoelectric cooling technology works by allowing hot electrons to migrate to one side of a body and be replaced by cooler ones. Traditional methods suffer, however, when heat is conducted back through the material. Cool Chips eliminates the problem by having a vacuum gap of less than 10 nanometers between the two walls of the flat chips. Heat is transferred via electrons which tunnel across the gap driven by a potential difference across the wafer. The heat is trapped at the hot side of the disc and dissipated by external methods.
Cool Chips says its discs can achieve 55% Carnot thermal efficiency, compared with 45% for compressor-based systems and less than 10% for traditional thermoelectric devices. The company expects to achieve cooling outputs of the order of hundreds of watts per cm2.
Peter Cowley, R-R chief scientist research and technology, says the technique could be useful for electronics used to distribute power around aircraft. “If Cool Chips is able to deliver what it promises, this technology will revolutionise our electronic heat management systems,” he says.
Meanwhile, the USN is to flight test an electrical power system using evaporative spray cooling on a Northrop Grumman EA-6B Prowler. The SprayCool aft power supply (SC-APS) system, supplied by Washington-based ISR, eliminates the need for heat sinks and is 10% lighter than air-cooled units. The tests are being managed by Naval Air Systems Command, which says the technology will be “a significant enabler of advanced airborne electronics”. SC-APS is designed to cope with extremely high heat density and handle six to 10 times the heat generated by the older devices.
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