论文部分内容阅读
以超临界压力正癸烷为工质,在内径2mm的竖直圆管内进行了不同工况条件下的流动与换热不稳定性实验研究。实验发现两种原理的不稳定性现象。转捩型是由于流动状态由层流向湍流转变引起,多为随机的小幅震荡,约在Re=5000左右出现;物性型由准临界温度附近剧烈变化物性所致,具有较大振幅和固定周期,约8~15s。增强系统稳定性的方法主要包括提高进口流体温度、升高压力或者采用向下流动方式。实验还发现在振荡区间内存在稳定区间现象。
Using supercritical pressure n-decane as working medium, the instability of flow and heat transfer under different working conditions was investigated in a vertical tube with an inner diameter of 2 mm. The experiment found that the two principles of instability. The transition type is caused by the change of laminar flow to turbulent flow, which is mostly random small oscillations and occurs at around Re = 5000. The physical properties are caused by the violently changing physical properties near the quasi-critical temperature, with large amplitude and fixed period, About 8 ~ 15s. Methods to enhance the stability of the system include increasing the temperature of the inlet fluid, increasing the pressure or adopting a downward flow. The experiment also found that there is a stable interval oscillation phenomenon.