Liquid film and heat transfer characteristics during superheated wall cooling via pulsed injection of a liquid jet
Liquid film and heat transfer characteristics during superheated wall cooling via pulsed injection of a liquid jet
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DOI：
10.1016/j.ijheatmasstransfer.2023.123934
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发表时间：
2023-05
影响因子：
5.2
通讯作者：
N. Sako;K. Noda;J. Hayashi;Y. Daimon;H. Kawanabe
中科院分区：
文献类型：
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作者：
N. Sako;K. Noda;J. Hayashi;Y. Daimon;H. Kawanabe
脉冲点火是小型航天器双组元推力器姿态控制的主要工作方式之一。在脉冲点火模式下，推进器的工作范围取决于液膜冷却性能的恶化。由于冷却性能是由液体膜去除的热量和传递到歧管的热量的平衡决定的，因此必须理解液体射流的间歇喷射下的液体膜的行为和传热特性，以实现更宽范围的操作模式。为了更好地理解脉冲冷却过程，我们通过脉冲喷射液体射流对过热金属板进行了冷却试验。不同的喷射模式，包括连续喷射，相同的喷射量，在两种类型的金属板（铝合金和铜）进行了研究，因为金属板的热性能影响的液体膜的传热特性和板的温升在脉冲间的持续时间。基于金属板上的液膜的演变和金属板的后侧温度来评估冷却过程。分别使用高速相机和红外相机同时可视化演化和温度。为了将液膜状态与传热过程联系起来，通过求解三维瞬态导热反问题，估算了冷却表面的温度和热流密度。结果表明，湿润锋位置对应于最大温度梯度的位置。此外，通过蒸发和与核态沸腾相关的液滴分散消耗残余液膜。金属板的热惯性和扩散率的影响突出了由液体膜移除的热量的差异。在脉冲冷却过程中，铝合金板上的液膜带走的热量呈现出峰值，并且高于连续喷射。在低占空比条件下移除较少的热量，并且由液膜移除的热量低于通过在铜板上连续注入移除的热量。
Pulse firing is one of the major operation modes of bipropellant thrusters for the attitude control of small-scale spacecrafts. In the pulse-firing mode, the operational range of the thruster depends on the deterioration of liquid film cooling performance. Because cooling performance is determined by the balance of heat removed by the liquid film and transferred to the manifold, the behavior and heat transfer characteristics of liquid films under the intermittent injection of liquid jets must be understood to enable a wider range of operational patterns. We conducted cooling tests on a superheated metal plate via the pulsed injection of a liquid jet for better understanding of the pulsed cooling process. Different injection patterns, including continuous injection, with the same injection quantity were examined on two types of metal plates (aluminum alloy and copper), because the thermal properties of metal plates affect both the heat transfer characteristics of the liquid film and temperature rise of the plate during the inter-pulse duration. The cooling process was evaluated based on the evolution of the liquid film on the metal plate and rear-side temperature of the metal plate. The evolution and temperature were simultaneously visualized using a high-speed camera and infrared camera, respectively. To link the liquid film state to the heat transfer process, the temperature and heat flux on the cooled surface were estimated by solving the inverse problem of three-dimensional transient heat conduction. The results indicate that the wetting front position corresponds to the position of the maximum temperature gradient. Additionally, the residual liquid film is consumed through the evaporation and the droplet dispersion related to the nucleate boiling. The effects of thermal inertia and diffusivity of the metal plate highlight the differences in the amount of heat removed by the liquid film. The heat removed by the liquid film during pulsed cooling exhibited a peak and was higher than that removed by continuous injection on the aluminum alloy plate. Less heat was removed under low-duty-cycle conditions, and the amount of heat removed by the liquid film was lower than that removed by continuous injection on the copper plate.