The numerical modeling of the vapor bubble growth on the silicon substrate inside the flat plate heat pipe

Abstract

Inside the flat plate heat pipes for the microelectronics packages, the micro scale boiling is a common phenomenon under the suddenly high heat flux. The internal vast vapor bubble nucleation and growth become a challenge for the stable operations. Due to the lack of the direct observations, the vapor bubble growth in early stage is still unclear. In order to study the initial bubble growth, the molecular dynamics models of water-silicon interfaces which have different sizes of simulation boxes were examined. The vapor bubble diameter growth rates (0.18 ± 0.02 × 106 mm/s) were calculated among the different sizes of simulation boxes. Since the lack of extra energy input, the initial vapor bubble can only expand to 45 nm diameter large (under 100 W/cm2 heat flux at 350 K initial temperature). The growth phenomena of 0.1 μm to 0.3 mm scale bubbles could be further modeled by the Mixture models. The observed bubble (bubble diameter between 10 μm and 0.3 mm) had a diameter growth of 0.71 ± 0.19 mm/s that was close to the Mixture model simulated one (0.75 mm/s). In addition, the ratio of the bubble volume growth rate to the bubble covered bottom area was about 7 ± 0.2 mm/s. By calculating the ratio between the growth rate of observed bubbles and volume of the simulated stable nucleation bubble, the bubble generation rate (3 × 1014 bubble/s mm2) under certain conditions might be estimated. Therefore, the whole process of bubbles growth could be deduced.