Electro-Hydrodynamic Augmentation of Heat Transport in Micro Heat Pipe Arrays

Abstract

Abstract Research is reported on a novel use of electrostatic fields to both enhance the effectiveness of heat transport and the maximum heat transfer throughput of micro heat pipe devices. This research has sought to make practical the electro-hydrodynamic heat pipe concept proposed by T. Jones in the early 1970s, but which never was successfully developed at macroscales. Experiments are reported which conclusively demonstrate the viability of using electrostatic fields to augment heat transfer in micro heat pipe devices. An n-pentane filled glass heat pipe array comprised of 1mm width grooves having 1mm of ‘land’ between each groove was fabricated from quartz. The heat pipe array was 25.4 mm long. Gold-palladium electrodes, approximately 100 microns in thickness, were vapor deposited on both sides of the heat pipe to allow for the application of an electrostatic field across the grooves of up to 10 kV/mm. The electrodes were semi-transparent, thereby permitting visual observation of the liquid orientation within the micro heat pipe. For a majority of experiments, however, the micro heat pipes were contained in an insulated enclosure. The experiments indicated little difference in the micro heat pipe temperature at low heat inputs (less than 0.3 W/groove). At heat inputs sufficient to cause the onset of dry-out of the evaporator without application of the electric field, the presence of the electric field was noticeable in producing a more uniform micro heat pipe temperature and a relatively lower evaporator temperature. At increasing heat inputs, the presence of the electric field was shown to prevent evaporator dry-out for the heat inputs considered. Further, at heat inputs sufficient to cause dry-out of the evaporator without an applied electric field, the electric field contributed to an increasing heat transfer effectiveness in the evaporator as the heat input was increased.