Electrohydrodynamic enhancement of heat transport capacity of micro heat pipe arrays

Recent research has demonstrated the effective use of electric fields to augment phase change heat transport associated with boiling, condensation and evaporation processes. Building upon this research, this study investigated the potential for employing electrohydrodynamic forces produced by electric fields to increase the heat transport capacity of micro heat pipes with a noncircular pore. The experiments conducted during the present research conclusively demonstrate the viability of using electrostatic fields to augment heat transfer in micro heat pipe devices. They addressed and evaluated the effects of electrohydrodynamic forces on the shape and the dynamics of the liquid-vapor interface in micro heat pipes, and on the fluid motion in the bulk and extended meniscus in micro heat pipes. Micro heat pipes of two different sizes were tested. Various liquids such as n-pentane, hexane, decane, acetone, ethanol and distilled de-ionized water, were used. The results indicated that the use of electrostatic field in the vicinity of the evaporator region provided a remarkable increase in the liquid mass flow rate into the evaporator. This influx of additional liquid into the evaporator would promote an increased heat transport and prevention of dry-out condition. An analytical model was developed which supported the experimentally observed trends.; The results and lessons from the first set of experiments inspired the design of a micro heat pipe array used in the follow-on experiments. It consisted of a flat quartz substrate containing seven rectangular cross-section micro grooves. An electric field was applied through four finger-type electrodes which covered the odd numbered grooves. 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 lower evaporator temperature. At increasing heat inputs, the presence of the electric field was shown to prevent evaporator dry-out. Further, the electric field contributed to an increasing heat transfer effectiveness in the evaporator as the heat input was increased.