EHD Conduction-Driven Enhancement of Critical Heat Flux in Pool Boiling

When a liquid undergoes pool boiling, there is a critical heat flux at which the departing vapor bubbles start to inhibit the flow of fresh liquid to the heated surface. A number of methods to enhance the critical heat flux of pool boiling have been considered, including electrohydrodynamic (EHD) enhancement. In these studies, the heater surface has generally been electrically grounded, and a high-voltage electrode has been placed a short distance away from the heater surface to create a high intensity field near the heater. The resulting configuration produces a dielectrophoretic force on the vapor bubbles to promote vapor removal. However, the high-voltage electrode can also act as a physical barrier to the incoming liquid and the departing vapor. This paper considers a different technique for the EHD enhancement of critical heat flux. EHD conduction pumping-type electrodes are embedded into the heater surface and used to pump liquid along the heated surface. The embedding of this pumping technique into the heater thereby promotes the wetting of the surface and subsequently delivers sizable enhancements to the heat transfer. The effect of a variety of applied voltages on the boiling curve and the critical heat flux point are quantified. An analytical model is developed to explain the enhancement effect.