Transient boiling and pressure recovery in a vacuum vessel during cooling of a high temperature body with an impinging jet

对装在真空容器中的高温(30 0ﾟC)圆柱体在冲击射流作用下冷却并回收容器内压力的过程中的瞬时换热进行了实验研究。实验的初始压力为500~1000Pa，射流速度为1~15m/S，射流直径为1~3 mm，射流温度为10~90ﾟC。以铜、黄铜和钢为试验材料，考察了不同热物性对瞬时冷却的影响。结果表明：1.压力恢复和换热特性可分为三个区域A：压力恢复以过热液体的冲刷蒸发为主。这一地区在很短的时间内完成。高温体的换热速度有限，导致射流液体蒸发很少。区域B：压力恢复受沸腾…产生的水蒸汽量的影响更多关于高温磁盘的信息。沸腾区域随时间向磁盘表面外缘移动。区域C：压力恢复到相应的状态并保持不变，在此期间表面的换热变为强制对流。由于高温表面开始润湿的时间取决于热物性，因此压力恢复和换热速率受试验材料的影响很大。材料表面的换热速率受材料热物性的控制。尽管表面和测量点之间存在时间滞后，因此不能准确地预测表面热流密度，但提出了一种根据冷却过程中的瞬时温度估算表面热流密度的计算方法。明确了沸腾区域运动与换热速率之间的关系，但两者之间存在一定的时滞。建立了冷却过程换热压力恢复率预测模型，预测值与实验值吻合较好。较少

An experimental study has been made on transient heat transfer during cooling of a high temperature (300ﾟC) cylindrical body mounted in a vacuum vessel with an impinging jet and then recovery of pressure in the vessel. The experiment was carried out for initial pressure of 500 to 1000 Pa, jet velocity of 1 to 15 m/s, jet diameter of 1 to 3 mm, and jet temperature of 10 to 90ﾟC using water as test liquid. Copper, brass and steel are used as test material in order to check effect of different thermal properties on the transient cooling. The following results are obtained :1. Characteristics of pressure recovery and heat transfer are categorized in to three regions asRegion A : The pressure recovery is dominated by flush evaporation of superheated liquid. This region finishes at a short time. The heat transfer rate from high temperature body is limited resulting into little evaporation of liquid of jet.Region B : The pressure recovery is influenced by amount of vapor generated by boiling … More on high temperature disk. Boiling area moves toward outer edge of disk surface with time.Region C : The pressure recovers to a corresponding state and is kept constant during which heat transfer from the surface becomes forced convective, only.2. The pressure recovery and heat transfer rate are strongly influenced by test material since the time at which wetting of the high temperature surface starts depends on thermal properties. The heat transfer rate from the surface would be controlled by thermal properties of material.3. A computation procedure is developed to estimate surface heat flux from transient temperature during cooling, although a time lag exist between surface and measuring points and then is not predicted accurate.4. A relationship between movement of boiling area and heat transfer rate is made clear, although a time lag between them exists.5. A model to predict pressure recovery from heat transfer rate during cooling is developed, showing that the value predicted is in good agreement with experimental one. Less