A review of active enhancement methods for boiling and condensation

As the demand for better performing heat exchangers and thermal management devices increases, novel heat transfer enhancement methods become more necessary. Heat transfer in conventional heat exchangers has been enhanced passively with enhanced surfaces or by applying coatings, but passive methods can often only be effective in a narrow range of operating conditions, can require frequent replenishment (in the case of coatings) and may not provide enough heat transfer enhancement in applications that require very high heat fluxes. Therefore, there is a need to further investigate active methods of heat transfer enhancement for boiling and condensation, where the already high heat transfer coefficients can be made even higher for high heat flux applications. This study reviews several active enhancement methods frequently used in phase-change heat transfer applications. This includes electrohydrodynamic enhancement, active surface modifications (surface vibration, rotation, and adaptable surface geometries), and fluid vibration. The physical mechanisms of each enhancement method and experimental results published to date are presented and discussed. Finally, a comparison between the enhancement methods is made, and recommendations for future research are outlined.