纯水静态闪蒸中液膜高度演变的实验研究

doi:10.11949/j.issn.0438-1157.20180991

摘要/Abstract

摘要：

设计搭建了静态闪蒸实验台，利用高速摄影对不同过热度、节流孔板直径和闪蒸速率下纯水静态闪蒸过程中液膜高度的演变规律进行了实验研究。实验中过热度为7.0~32.5 K，节流孔板直径为5、10、20 mm，闪蒸速率为0.004~0.073 s^-1。通过液膜膨胀率来衡量和比较液膜高度的变化，液膜膨胀率是指闪蒸过程中液膜实时液位与初始液位的比值。结果表明：最大膨胀率随过热度或节流孔板直径的增大而增大；节流孔板直径一定时，闪蒸速率可通过改变过热度来调节，此时最大膨胀率随闪蒸速率的增大而减小；当过热度一定时，闪蒸速率可通过改变节流孔板直径来调节，此时最大膨胀率随闪蒸速率的增大而增大。最后，根据实验结果拟合得到过热度、闪蒸速率与最大膨胀率的实验关联式，其计算值与实验值吻合良好。本文研究结果对工业闪蒸设备小型化、紧凑化和精细控制提供了重要的实验依据。

关键词: 静态闪蒸, 过热度, 节流孔板直径, 闪蒸速率, 最大膨胀率

Abstract:

Experimental study on evolution of waterfilm height during static flash of pure water was carried out with superheat varying between 7.0 K and 32.5 K, orifice diameter at 5, 10, 20 mm, and flash speed between 0.004 s^-1 and 0.073 s^-1. Results indicated that the maximum expansion rate of waterfilm increased with rising superheat or orifice diameter. At given orifice diameter, the flash speed decreased with rising superheat, however, the maximum expansion rate of waterfilm increased with it. At given superheat, both flash speed and the maximum expansion rate increased with increasing orifice diameter. At last, an experimental correlation was set up between maximum expansion rate and superheat, flash speed. The calculated results matched well with experimental data. These results provided a technical support for the miniaturization, compactness and finely control of industrial flash system.

Key words: static flash, superheat, orifice diameter, flash speed, maximum expansion rate

中图分类号:

TK 124

王辉辉, 张丹, 杨庆忠, 牛照程. 纯水静态闪蒸中液膜高度演变的实验研究[J]. 化工学报, 2019, 70(S1): 54-60.

Huihui WANG, Dan ZHANG, Qingzhong YANG, Zhaocheng NIU. Experimental study on evolution of waterfilm height during static flash of pure water[J]. CIESC Journal, 2019, 70(S1): 54-60.

图/表 11

图1 静态闪蒸实验系统

Fig.1 Experiment system of static flash

表1 实验参数的不确定性

Table 1 Uncertainty analyses of experiment parameters

参数	绝对不确定度,dx	最小测量值,x_min	最大相对不确定度,dx/x_min
T/K	0.2	66.2	3.0×10^-3
H_fc/m	5.0×10^-4	0.1	5.0×10^-3
τ/s	0.025	2	0.0125
ΔT/K	—	—	4.2×10^-3
H_r	—	—	7.1×10^-3
NET	—	—	5.9×10^-3
FS/s^-1	—	—	0.0138

图2 液膜液位演变的典型过程

Fig.2 Typical evolution of waterfilm height

图3 过热度对液膜膨胀高度的影响

Fig.3 Evolutions of waterfilm height under different superheats

图4 过热度变化下液膜膨胀率的比较

Fig. 4 Comparison of expansion rate of waterfilm under different superheats

图5 节流孔板直径对液膜膨胀高度的影响

Fig. 5 Evolutions of waterfilm height under different orifice diameters

图6 节流孔板直径变化下液膜膨胀率的比较

Fig.6 Comparison of expansion rate of waterfilm under different orifice diameters

图7 分界点时刻定义

Fig.7 Definition of turning instant between fast and gradual evaporation stages

图8 节流孔板直径一定时最大膨胀率随闪蒸速率的变化

Fig.8 Maximum expansion rate versus flash speed at given orifice diameter

图9 过热度一定时最大膨胀率随闪蒸速率的变化

Fig.9 Maximum expansion rate versus flash speed at given superheat

图10 最大膨胀率计算值与实验值的相对误差

Fig.10 Relative error between calculated and experimental maximum expansion rate

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