Two-phase thermal management using a small-scale, heat transfer cell based on vibration-induced droplet atomization

A two-phase heat transfer module in which thin-film evaporation on the hot surface is achieved using surface droplet atomization is described and characterized. Surface atomization is achieved using a vibration-induced droplet atomization (VIDA) process in which small liquid droplets are produced within a sealed heat transfer cell and are propelled onto the heated surface. The VIDA technique involves the violent break-up of thin liquid layers on the vibrating surface of a piezoelectrically driven membrane that is operated at resonance. Liquid is supplied to the atomizer at a controlled rate using an integrated miniature piezoelectric pump thereby enabling orientation insensitive cell operation. The impact of the atomized droplets on the heated surface forms a thin film that evaporates continuously and the resulting vapor is condensed both on the internal surfaces of the heat transfer cell and on the surface of the atomized droplets. The condensate is collected and returned to the atomizer module by the integral diaphragm pump. The present paper describes the operation and characterization of a small-scale VIDA heat transfer module for cooling integrated circuits at the power level of desktop microprocessors. A unique element of the new cell is the addition of an internal synthetic jet that operates in the vapor space and regulates the droplet motion towards the heated surface and the transport of the vapor. Particular emphasis is placed on the cell´s operating characteristics and cooling capabilities. Heat fluxes as high as 420 W/cm² have been realized at die temperature below 135°C.