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首页> 外文期刊>International Journal of Heat and Mass Transfer >Bubble nucleation, growth and surface temperature oscillations on a rapidly heated microscale surface immersed in a bulk subcooled but locally superheated liquid under partial vacuum
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Bubble nucleation, growth and surface temperature oscillations on a rapidly heated microscale surface immersed in a bulk subcooled but locally superheated liquid under partial vacuum

机译：在部分真空下浸没在大量过冷但局部过热的液体中的快速加热的微尺度表面上的气泡成核，生长和表面温度振荡

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摘要

The effect of ambient pressures below atmospheric, liquid subcooling and heating rate on bubble dynamics associated with rapid evaporation in highly superheated water is investigated. Platinum films of various aspect ratios are electrically heated under partial vacuum and the average metal film temperature monitored during a power pulse of duration of several tens of microseconds. At high liquid subcooling, the surface temperature of the pulse-heated thin platinum strips is shown to oscillate with a frequency on the order of 0.5 MHz. The oscillation frequency increases with ambient pressure in the range 0.02 MPa and 0.101 MPa, and decreases with increasing ambient temperature at a fixed pressure. An unusual dynamic instability is observed in which the surface temperature is constant before relaxing into oscillations, and the delay to oscillations increases with decreasing pressure. High speed imaging shows that the bubble growth phase of the oscillation is associated with surface heating and the collapse phase with surface cooling in the cyclic temperature history. These effects are explained by a bubble growth theory that includes a heat loss mechanism to the surrounding liquid. The nucleation temperature is unaffected by pressure in the sub-atmospheric range examined and it approaches the theoretical superheat limit for water at a heating rate of about 10~9 ℃/s.
机译：研究了环境压力低于大气压，液体过冷度和加热速率对与高度过热水中的快速蒸发相关的气泡动力学的影响。在部分真空下对各种纵横比的铂膜进行电加热，并在持续数十微秒的功率脉冲期间监控平均金属膜温度。在较高的液体过冷度下，脉冲加热的铂薄带的表面温度显示为以0.5 MHz的频率振荡。振荡频率随着环境压力在0.02 MPa和0.101 MPa范围内的增加而增加，并随着环境温度在固定压力下的增加而降低。观察到异常的动态不稳定性，其中在松弛之前，表面温度是恒定的，并且随着压力的降低，振动的延迟增加。高速成像表明，在循环温度历史中，振荡的气泡生长阶段与表面加热相关，崩溃的阶段与表面冷却相关。这些影响由气泡生长理论解释，该理论包括对周围液体的热损失机制。在所检查的低于大气压范围内，成核温度不受压力的影响，并且在大约10〜9℃/ s的加热速率下，它接近理论上的水过热极限。

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