Boiling heat transfer enhancement by submerged vibration induced jets

This paper describes a new two-phase cooling cell based on channel boiling and a vibration-induced cavitation jet whose collective purpose is to delay the onset of critical heat flux by forcibly dislodging the small vapor bubbles attached to a solid surface during nucleate boiling and propelling them into the cooler bulk liquid within the cell. The submerged turbulent cavitation jet is generated by a vibrating piezoelectric diaphragm operating at resonance. The piezoelectric driver induces pressure oscillations in the liquid near the surface of the driver, resulting in the time-periodic formation and collapse of cavitation bubbles that entrain surrounding liquid and generate a strong liquid jet. The resultant jet, which is directed at a heated surface, enhances boiling heat transfer by removing attached vapor bubbles that insulate the surface while providing additional forced fluid convection on the surface. By introducing a crossflow within the cell, the heat transfer is increased even further due to the fact that the flow sweeps the bubbles downstream while keeping the temperature of the water within the cell regulated.