Numerical simulation of air-water two-phase flow under elevated pressures and temperatures using CFD-PBM coupled model

doi:10.11949/0438-1157.20210186

Abstract

Abstract:

The combination of computational fluid dynamics and the population balance model (CFD-PBM) can effectively simulate the fluid behavior in the bubble column, and more accurately predict the flow characteristic, phase holdup and local bubble size distribution. In this paper, numerical simulations of air-water two-phase flow are studied under thermal conditions by using CFD-PBM coupled model in a pressurized bubble column with a 100 mm diameter and 1.3 m height. The system has been investigated in the range of 1MPa, the superficial gas velocity of 0.08—0.24 m/s, and the temperature of 30—160℃. The effect of the superficial gas velocity, temperature and solid content of air-water system on the average gas holdup, large and small bubbles gas holdup, bubble diameter, and bubble size distribution are discussed. The results show that the simulation results of the average gas holdup are in good agreement with the experimental values within the error range of 10%. The temperature change mainly affects the coalescence and breakage of bubbles in the tower, and the coalescence and breakage mechanism is used to explain the influence of temperature on the fluid behavior.

Key words: bubble column, computational fluid dynamics, two-phase flow, gas holdup, large and small bubbles, high temperature and pressure, solid holdup

摘要：

计算流体力学与群体平衡模型（CFD-PBM）结合可有效地模拟鼓泡塔内流体行为，较准确地预测流场、相含率以及局部气泡尺寸分布。以直径100 mm、高1.3 m的加温加压鼓泡塔为模拟对象，在系统压力为1 MPa、表观气速为0.08~0.24 m/s、温度为30~160℃条件下系统地考察了空气-水体系的表观气速、温度以及固含率对平均气含率、大小气泡气含率、气泡直径和气泡尺寸分布等参数的影响。结果表明，平均气含率的模拟结果和实验值在10%的误差范围内吻合较好；温度的变化主要影响了塔内气泡的聚并和破碎，并用聚并破碎的机理解释了温度对其流体行为的影响。

关键词: 鼓泡塔, 计算流体力学, 两相流, 气含率, 大小气泡, 加温加压, 固含率

CLC Number:

TQ 028.8

Wenlong ZHANG, Yan HOU, Haibo JIN, Lei MA, Guangxiang HE, Suohe YANG, Xiaoyan GUO, Rongyue ZHANG. Numerical simulation of air-water two-phase flow under elevated pressures and temperatures using CFD-PBM coupled model[J]. CIESC Journal, 2021, 72(9): 4594-4606.

张文龙, 侯燕, 靳海波, 马磊, 何广湘, 杨索和, 郭晓燕, 张荣月. 加温加压下CFD-PBM耦合模型空气-水两相流数值模拟研究[J]. 化工学报, 2021, 72(9): 4594-4606.

Figures/Tables 14

Fig.1 Experimental device

Table 1 Physical properties of gas and liquid

气液相	黏度/ (mPa·s)	密度/ (kg/m³)	表面张力/ (mN/m)	固含率/%
H₂O Ⅰ 35℃	0.7340	992.6	69.83	0
H₂O Ⅰ 100℃	0.2820	990.1	58.84	0
H₂O Ⅰ 160℃	0.1740	993.9	46.58	0
H₂O Ⅱ 45℃	0.8264	1017.5	68.65	5
H₂O Ⅱ 100℃	0.2915	985.4	58.84	5
H₂O Ⅱ 160℃	0.1792	934.8	46.58	5
H₂O Ⅲ 60℃	0.5225	1064.0	66.20	15
H₂O Ⅲ 100℃	0.3139	1039.0	58.84	15
H₂O Ⅲ 160℃	0.1930	1016.0	46.58	15
H₂O Ⅳ 30℃	0.9780	1130.9	70.42	25
H₂O Ⅳ 100℃	0.3449	1095.4	58.84	25
H₂O Ⅳ 160℃	0.2120	1044.4	46.58	25
空气（1 MPa）	0.0179	12.09

Fig.2 Partition of different quality grids

Fig.3 The influence of different mesh quality on average gas holdup

Fig.4 The relationship between superficial gas velocity of air-water system and average gas holdup under different temperatures

Fig.5 The relationship between temperature of air-water system and average gas holdup under different temperatures

Fig.6 The distribution of average gas holdup of air-water TA system under different solid holdups

Fig.7 The relationship between temperature of the air-water system and large and small bubbles gas holdup under different temperatures

Fig.8 The relationship of large-bubble and small-bubble gas holdup of air-water TA system with different solid holdups

Fig.9 Radial gas holdup distribution diagram of air-water system at different temperatures

Fig.10 Distribution diagram of air holdup contours in axial section of air-water system

Fig.11 Radial distribution of liquid velocity at different temperatures

Fig.12 The bubble diameter distribution diagram of air-water system at different temperatures

Fig.13 The relationship between temperature of air-water system and bubble number density distribution under different temperatures

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