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Passive fluid pumping during boiling using the concept of asymmetry in the geometry of the heated surface is studied experimentally. The geometry consists of a channel that is located within a chamber filled with dielectric fluid. The channel ends (inlet and outlet) are exposed to the chamber, such that the ends of the channel have the same pressure prior to the addition of heat. Two types of asymmetry are introduced on the heated surface, and their effect is assessed on the net bubble growth and motion within the open-ended channel. The first is a millimeter-scale asymmetry caused by contouring the vertical walls of the channel into repeating 60-30-degree ratchets. The second asymmetry consists of microscale reentrant cavities, located periodically on the shallow ratchet face of the ratchet. To assess the motion of two-phase flow within the channel, visualization at various heat fluxes ranging from 0.8 – 2.6 watts per square centimeter and subcooling from 2.7 - 11.5 degrees C is performed. Videos of bubble ebullition, mergers and slug transport are analyzed to obtain growth rates, velocities, and frequency counts of slugs emanating from either end of the open-ended channel. 

Passive fluid pumping during boiling using the concept of asymmetry in the geometry of the heated surface is studied experimentally. The geometry consists of a channel that is located within a chamber filled with dielectric fluid. The channel ends (inlet and outlet) are exposed to the chamber, such that the ends of the channel have the same pressure prior to the addition of heat. Two types of asymmetry are introduced on the heated surface, and their effect is assessed on the net bubble growth and motion within the open-ended channel. The first is a millimeterscale asymmetry caused by contouring the vertical walls of the channel into repeating 60-30-degree ratchets. The second asymmetry consists of microscale reentrant cavities, located periodically on the shallow ratchet face of the ratchet. To assess the motion of two-phase flow within the channel, visualization at various heat fluxes ranging from 0.8 – 2.6 W/cm2 and subcooling from 2.7 - 11.5 oC is performed. Videos of bubble ebullition, mergers and slug transport are analyzed to obtain growth rates, velocities, and frequency counts of slugs emanating from either end of the open-ended channel.