| An experimental and numerical investigation of rapid formation and collapse of a, vapor bubble formed on a pulsed microheater is presented herein. Short electric pulses in the range of 1 mus to 4 mu s are applied to the resistive heater in thermal inkjet printhead. The heater is immersed in deionized water and generates a heat flux of more than 750 MW/m2. As a result, explosive vaporization process and subsequent bubble growth and collapse process occur. A stroboscopic technique with a time resolution of 30 ns and spatial resolution of 2 mum is used to capture the dynamics of the bubble. By applying various heating conditions, the nucleation mechanism and the growth and collapse of a bubble are studied. The nucleation temperatures are obtained from the one-dimensional heat conduction equation at the time of nucleation. They are close to the superheat limit of the water and show a weak linear dependency on the heating rate.; For a three-dimensional numerical analysis of the growth and collapse process of a bubble on a microheater and the surrounding liquid flow, a commercial code called SIMULENT is used to develop a fluid model for flow field calculations. Full Navier-Stokes equations with surface tension effects are solved with a finite volume method. A volume of fluid (VOF) interface tracking algorithm is used to track the evolution of the bubble-liquid interface. The one-dimensional thermal model provides the pressure boundary condition at the bubble-liquid interface to the fluid model. The fluid model in turn provides the bubble volume and surface area to the thermal model for the next time step. As a result, the momentum and energy exchange between the bubble and the liquid are analyzed. The simulation of bubble surface evolution is reasonably accurate. The influence of the heater geometry on bubble dynamics are also investigated. |
