Abstract:

The influence of initial and operating conditions on spray flash evaporation characteristics was investigated based on a new high-temperature and high-pressure spray flash evaporation system. Water was used as the working fluid. The initial liquid temperature was raised to above 100℃ and the pressure inside the flash chamber was maintained positive for the first time. A specially-designed swirl nozzle with two S-shaped internal vanes was used to inject liquid upward or downward into the flash chamber. The experiments were conducted at initial temperatures ranging from 135 to 150℃, pressures of 121, 126, 131, 136, 141 and 146 kPa and superheats from 30 to 46℃. The results indicated that the mass flow rate of vapor generated by flashing increased with the increase of initial temperature and decreased with the increase of pressure. Downward injection outperformed upward injection for higher vapor generation rate and less water carried out by vapor. The flash efficiency was found to increase linearly with the degree of superheat. An empirical equation between flash efficiency and the degree of superheat was proposed based on a large amount of experimental data. The results provided reference for the application of spray flash evaporation at high temperature and high pressure in industrial fields.

Key words: spray flash evaporation, high temperature and high pressure, influencing factors, flash efficiency, phase change, two-phase flow, evaporation

摘要：

基于新型高温高压喷雾闪蒸实验台,以水为工质,研究初始条件和运行条件对闪蒸蒸发特性的影响。首次将液体初始温度提高至100℃以上,将闪蒸罐运行压力保持为正压,并使用具有独特双S形叶片的涡旋实心锥喷嘴,将液体向上或向下喷入闪蒸罐。实验过程中液体初始温度为135～150℃,闪蒸压力分别为121、126、131、136、141、146 kPa,液体过热度为30～46℃。实验结果表明,闪蒸蒸汽流量随初始温度的提高而增大,随闪蒸压力的提高而减小。液体向下喷射比向上喷射产汽量更高,蒸汽带水更少。闪蒸效率随过热度呈线性增长,在大量实验数据基础上拟合出二者之间的经验公式。实验结果为高温高压喷雾闪蒸的工业应用提供借鉴。

关键词: 喷雾闪蒸, 高温高压, 影响因素, 闪蒸效率, 相变, 两相流, 蒸发