Abstract:

This paper focuses on the relationship between bubble behavior and bumping of aging oil. A visualization boiling vessel is built and relevant mathematical model is established according to the generation, growth, departure and rising of single bubbles, recorded by a high-speed camera. Results show that, with the increase of driving force ΔT_s (degree of superheating), the water on the heat transfer surface boils, forming vapor-in-oil bubbles. The departure time of bubbles decreases with the increase of heat flux, while the density of nucleation sites on the heat transfer surface increases. As ΔT_s increases continuously, a bubble layer forms when the rupturing rate of bubble is lower than their producing rate. Accumulation of a large number of bubbles will make the bubble layer amplify to the entire container space rapidly to form bumping.

Key words: aging oil, boiling mechanism, bubbles, heat flux, nucleation site density

摘要：

实验室内建立可视化沸腾容器,用高速摄像机记录单个气泡的生成、成长、脱离、上升的过程,并建立相关数学模型,研究气泡行为与老化油暴沸之间的关系。研究表明,随着“驱动力”ΔT_s(即过热度)逐渐增大,传热面上水开始汽化沸腾,形成油包蒸汽气泡,气泡的跃离时间随热通量的增加而缩短,而传热面上的汽化核心密度增加;“驱动力”继续增大,气泡的破灭速度低于生成速度时,形成气泡层,大量的气泡累积会使气泡层迅速扩增到整个容器空间,形成暴沸。

关键词: 老化油, 暴沸机理, 气泡, 热通量, 汽化核心密度