Numerical study of boiling single bubble in vertical impact of dual synthetic jets

In response to the new active enhanced heat transfer technologies required for current aerospace and electronic device cooling, a numerical study was conducted on dual synthetic jets vertical impact boiling single bubble, analyzing the effects of jets impact on bubble growth and detachment during boiling. Compared with not impacted, the bubble detachment frequency significantly increased after the jets impact, while the detachment volume decreased. At the same time, the jets can effectively remove near-wall bubbles, disrupt the near-wall thermal boundary layer, efficiently draw cold fluid from the mainstream region to near the wall, and reduce bubble coverage \phi . It was found that the larger the bubble coverage, the smaller the convective heat transfer coefficient. Dual synthetic jets impact can transform the original boiling from a violently oscillating unstable state to a relatively stable and controllable state, reducing surface bubble coverage while stabilizing the convective heat transfer coefficient at a relatively high value. Under the conditions of an amplitude of 1.4 m/s, a frequency of 50 Hz, and an impact distance of 15 mm, the average bubble coverage decreased by 7.64%, and the convective heat transfer coefficient increased by 32.18%. In addition, the effects of Dual synthetic jets amplitude, frequency and impact distance on the impact performance were analyzed: changes in amplitude directly determine the jet velocity and have a greater effect on the impact, the minimum heat transfer improvement is 21.33% when the amplitude is 0.8 m/s, and the maximum can reach 41.32% when the amplitude is 1.1 m/s. Meanwhile, jet velocity is the main factor determining the horizontal displacement of bubble.The change in frequency also affects the impact effect, its influence is relatively small compared with the change in amplitude. Moreover, it can always maintain a good heat transfer enhancement effect, the heat transfer enhancement within the frequency range of 10 Hz to 90 Hz differs by less than 10%. There exists an optimal impact distance that can achieve the best heat transfer enhancement effect. When the impact distance is 11 mm, the improvement is minimal, and the heat transfer coefficient increases by 16.34%; The maximum improvement is achieved when the impact distance is 15 mm, and the heat transfer coefficient increases by 31.97%.