Abstract:

The effects of high temperature and pressure on bubble formation under constant flow conditions in N₂-H₂O, He-H₂O and N₂-tetradecane were experimentally investigated. The experiment conditions covered orifice velocity from about 0 up to 1500 cm/s, temperature from 293 K up to 393 K, pressure from 0 up to 6 MPa, orifice diameter 1.12 mm up to 2.5 mm. The experiments were carried out in a stainless steel bubble column of 50 mm I.D with three pairs of high strength quartz windows. The bubble flow was visualized and recorded through high speed camera. The results show that bubble diameter decreases and aspect ratio increases with increase of pressure. The effect of temperature is complicated owing to the change of saturated vapor pressure, ratio to system pressure. When the ratio is larger, bubble diameter increases with temperature due to vaporization phenomenon. When the ratio is smaller, bubble diameter decreases with temperature. According to the experimental results, the bubble diameter model proposed by Gaddis was modified, and the saturated vapor pressure contribution was introduced to obtain a new estimation formula for the bubble diameter under high temperature and high pressure conditions.

Key words: bubble, vaporization, temperature, pressure, saturated vapor pressure, gas-liquid flow

摘要：

温度压力对进气管孔口气泡的生成具有重要影响。以氮气-水、氦气-水、氮气-十四烷为研究体系，采用高速摄像法，观察了恒速流下孔口气泡的形成过程，考察了孔口气速（0~1500 cm/s）、温度(293~393 K)、压力（0~6 MPa）、孔径（1.12, 2.5 mm）、气体类型（N₂、He）对气泡生长过程的影响。实验表明：随着压力增加，气泡直径减小，纵横比增加；温度升高一方面导致黏度、密度和表面张力降低，使气泡直径减小，另一方面加剧了液体汽化，使得气泡直径增大。根据实验结果修正了Gaddis提出的气泡直径模型，引入饱和蒸气压贡献项，得出新的适用于高温高压条件下气泡直径的估算式。

关键词: 气泡, 汽化, 温度, 压力, 饱和蒸气压, 气液两相流