Exposure testing of dielectric liquids for aircraft EHD heat exchanger applications

An eight-week test evaluated long-term exposure effects of pulsed high voltage electric fields on fluid properties. Two electronics cooling fluids suitable for aviation use were tested: FC-72, a perfluorocarbon, and PAO, or polyalphaolefin, a dielectric cooling oil. These fluids were exposed to approximately 10,000 on-off cycles and tested for changes in fluid physical and electrical properties and chemical composition. Test results showed no significant changes in FC-72 properties, but a substantial reduction in the dielectric strength and increase in electrical conductivity of PAO. Further testing is required to isolate the cause of these changes.