CFD Simulation and High-Speed Photography of Liquid Flow in the

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Thermodynamics, Transport, and Fluid Mechanics

CFD simulation and high-speed photography of liquid flow in the outer cavity zone of a rotating packed bed reactor Yi Liu, Wei Wu, Yong Luo, Guang-Wen Chu, Wei Liu, Bao-Chang Sun, and Jian-Feng Chen Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.8b05718 • Publication Date (Web): 08 Mar 2019 Downloaded from http://pubs.acs.org on March 9, 2019

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Industrial & Engineering Chemistry Research

CFD simulation and high-speed photography of liquid flow in the outer cavity zone of a rotating packed bed reactor

Yi Liu †,‡, Wei Wu †,‡, Yong Luo †,‡,*, Guang-Wen Chu †,‡,*, Wei Liu †,‡, Bao-Chang Sun †,‡, Jian-Feng Chen †,‡

†

State Key Laboratory of Organic-Inorganic Composites and ‡ Research Center of

the Ministry of Education for High Gravity Engineering and Technology, Beijing University of Chemical Technology, Beijing 100029, PR China

* Corresponding author: Tel: +86 10 64446466; Fax: +86 10 64434784. E-mail address: [email protected]; [email protected]

1 ACS Paragon Plus Environment

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Abstract: The outer cavity zone, having numerous moving liquids, is an important mass transfer zone in a rotating packed bed (RPB) reactor. However, investigation of the liquid flow in the outer cavity zone is scarce. In this work, liquid flow in the outer cavity zone of the RPB reactor with nickel foam packing was studied by computational fluid dynamics (CFD) simulation and then verified by high-speed photography technology. Large eddy simulation and volume of fluid model were adopted to predict the liquid flow pattern, average diameter and velocity of liquid droplets in the outer cavity zone. A high-speed photography method, called “Sudoku” with eight shooting windows, was employed to capture the liquid flow of different zones in imaging experiments. Simulation results of liquid droplet velocity agreed well with the experimental results within a deviation of ±10%. This CFD simulation assisted with “Sudoku” photography was helpful to comprehensively understand the liquid flow in the outer cavity zone of the RPB reactor with nickel foam packing.


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1. Introduction As one of the novel multiphase reactors, the rotating packed bed (RPB) reactor can considerably improve the performance of mass transfer and micromixing, about 1~3 orders of magnitude larger than that of the packed column.1-3 With the advantages of high-efficiency and low-cost, RPB reactors have been widely adopted in many processes, including absorption,4-8 sulfonation,9 and synthesis of nanoparticles.10 A typical RPB reactor can be divided into the inner cavity, packing, and outer cavity zones, as shown in Figure 1(a).11 The liquid was drastically split by the rotating packing and then thrown into the outer cavity zone, mainly as moving droplets. As a result, the effective interfacial area of liquid increased sharply in the outer cavity zone, which was beneficial for gas-liquid mass transfer. Liquid droplets in the outer cavity zone have a high velocity of 3-30 m/s leaving from the outer edge of the packing zone. When liquid droplets were rebounded from the RPB shell, the liquid droplets would be broken again to generate plenty of daughter droplets or films, resulting in a further improvement of liquid effective interfacial area and surface renewal rate. Previous studies showed that the mass transfer contribution of the outer cavity zone was near 25% of the entire RPB reactor.12 In order to comprehensively understand the liquid flow in the outer cavity zone and make use of the high kinetic energy of moving droplets, it’s meaningful to investigate their behaviors and patterns in detail. Liquid flow visualization in the outer cavity zone of the RPB reactor has been researched by various methods.13-15 Yang et al.16 employed a noninvasive X-ray technique to examine the liquid distribution in the inner cavity, packing, and outer cavity zones of a RPB reactor. Sang et al.5 used a high-speed camera to observe the 3 ACS Paragon Plus Environment


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liquid flow pattern transition, droplet diameter, and size distribution in the outer cavity zone of a RPB reactor. As a theoretically analysis tool, computational fluid dynamics (CFD) simulation can be employed to predict the hydrodynamics in RPB reactors.17 Shi et al.18 studied the effects of rotational speed and packing structure on the liquid velocity, liquid droplet size, and liquid flow patterns in a RPB reactor with two-dimensional (2D) packing model. Xie et al.19 investigated the liquid flow in a RPB reactor by using a fine grid and the model predictions were in agreement with observations. Guo et al.20 explored the three-dimensional (3D) simulation on liquid flow in a RPB reactor, showing that 3D model provided a more detailed description of various flow patterns inside RPB reactor. Among the above studies, there are few reports about liquid flow in the outer cavity zone of the RPB reactor. Combing CFD simulation and high-speed photography, this work investigated the liquid flow in the outer cavity zone of a RPB reactor with nickel foam packing that has high mass transfer and micromixing performance. A physical model of nickel foam packing for CFD simulation was obtained by computed tomography (CT) reconstruction. Large eddy simulation (LES) and volume of fluid (VOF) model were adopted for the calculation. Liquid flow patterns near the outer edge of packing and shell were respectively studied in detail, including the average diameter and velocity of liquid droplets. Simulation results were then verified by the novel “Sudoku” method via the high-speed photography that merged eight small windows to capture liquid flow behaviors in the entire outer cavity zone.

2. CFD simulation 2.1 Physical model and grid refinement 4 ACS Paragon Plus Environment

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Figure 1(a) displays the schematic diagram of the RPB reactor with nickel foam packing. Figure 1(b) shows the photo of the nickel foam packing (Kunshan Jiayisheng Electronics co., LTD) used in this work. The porosity of the packing is 40 pores per inch (ppi) and the water contact angle is 101.8°. The inner diameter, outer diameter, and axial thickness of packing ring are 35, 80, and 18 mm, respectively (Figure S1, Supporting Information). CT technology was applied to acquire the cross-sectional images of the nickel foam packing. The phoenix Industrial High-Resolution CT & X-Ray System (General Electric Company, United State) was employed and the radiography imaging was processed by using CT-Reconstruction software. The original images shown in Figure 2(a) were processed into binarized pictures by AlgoLab R2V Toolkit. In order to analyze the influence of threshold level on the quality of the reconstructed structure of the packing zone, a test of selecting threshold level was carried out. The nickel foam was packed in the packing zone and the inner and outer cavity zones did not contain any information about packing structure. When the threshold was set at 35 level (Figure S2, Supporting Information), the noisy points of the inner and outer cavity zones were all eliminated, as shown in Figure 2(b). Thus, a threshold level of 35 was selected for the reconstruction. The detail information about CT reconstruction was shown in Supporting Information. A 2D geometrical model, which was built based on the above information as shown in Figure 3, was used to describe the RPB reactor with nickel foam packing for CFD simulation. The inner cavity zone has a liquid inlet pipe and the outer cavity has a liquid outlet. Based on the geometry of the RPB reactor, a computational grid of the RPB reactor was setup. In order to verify the grid independence, several grids with different numbers of cells were tested. A mesh of



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4 981 604 cells was retained, including 98 220 elements in the inner cavity zone, 1 289 668 elements in the packing zone, and 3 593 696 elements in the outer cavity zone. The size of cells in the packing zone was 0.1 mm and the size of cells in the outer cavity zone was 0.05 mm (Figure S3, Supporting Information). It is accurate enough to reflect the hundreds micrometer size of liquid droplets. The final mesh for computation was 2D mixed mesh. The interfaces between the inner cavity zone, packing zone, and outer cavity zones were all managed by the mesh moving model. 2.2 Simulation implementation Software package of Fluent (Version 17.0) was employed to solve all the 2D cases. LES and VOF model were applied in the simulation. The detail equations were listed in Supporting information. The operating conditions for the simulations are as follows: liquid initial velocity ranging from 1.52 to 3.58 m/s, rotational speed ranging from 500 to 2500 r/min. All the surfaces of the nickel foam packing were defined as rotational moving walls. Pressure outlet boundary condition was imposed on the liquid outlet which was the edge of the liquid outlet tube (Figure 3). Each simulation was conducted for 1 × 104 time steps with a time step size of 10-4 s, and 30 iterations were performed per time step to converge. Calculations were performed using a HP Z840 workstation with 2 CPU (36 cores), which had 2×Intel(R) Xeon(R) E5 [email protected], random access memory 512GB.

3. Imaging Experiments 3.1 Experimental setup and procedure Figure 4(a) shows the setup for the imaging experiments, including a RPB 6 ACS Paragon Plus Environment

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reactor system and a high-speed camera system. The specification of the RPB reactor and operation conditions, which were same as those used for CFD simulation, were listed in Table 1. A high-speed camera (FASTCAM SA4, Photron Limited, Japan) equipped with a lens (AF 200 mm f/4D, Nikon Co., Japan) was utilized to capture images of liquid motion in the outer cavity zone of the RPB reactor. The parameters of the high-speed camera and lens were listed in Table 2. In the imaging experiments, water (temperature, ~25 °C; density, 997 kg m3 ; viscosity, 0.894 mPa  s ; surface tension, 0.072 N / m ) was fed into the packing zone by the liquid inlet tube with an inner diameter of 1 mm. Liquid with constant velocity flowed across the rotating packing. Plenty of liquid droplets were generated in the outer cavity zone by the violent shearing of the packing, subsequently collected at the bottom of the outer cavity zone, and discharged through the liquid outlet. The annular lamp was employed when the high-speed camera was in the open mode. Figure 4(b1) displays eight different photograph windows from 1 ~ 4 and 6 ~ 9. The entire outer cavity zone of the RPB reactor was included in the eight windows. Figure 4(b2) was a demo photo captured from window 6. 3.2 Data processing Eight different photos captured from windows 1 ~ 4 and 6 ~ 9 were merged to a full picture of the entire outer cavity zone under same operation conditions as shown in Figure 5, which was called as “Sudoku” method. For each merged picture, liquid boundaries were recognized (Figure S4, Supporting Information) and then converted to binarized picture (Figure S5, Supporting Information). The detail description of droplet identification see Supporting Information. The average liquid droplet diameter was measured by the software of Image Pro, and liquid droplet velocity was acquired from consecutive photos by Photron FASTCAM Analysis 7 ACS Paragon Plus Environment


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(PFA).21

4. Results and discussion 4.1 Liquid flow Figure 6 shows the schematic diagram of liquid flow in the outer cavity zone. After violent interaction between liquid and packing inside the packing zone, liquid droplets, films or ligaments were generated at the outer edge of the packing. After flying a certain flow distance, liquid films and ligaments were broken up to liquid droplets in the outer cavity zone. Finally, liquid droplets collided on the shell of the RPB reactor. Part of liquids was rebounded as daughter liquid droplets, and other liquids transferred to liquid films on the inner surface of the shell. 4.1.1 Liquid flow patterns nearby the outer edge of packing Figure 7 shows the simulated and experimental liquid flow patterns in the outer cavity zone of the RPB reactor. It can be seen that the liquid flow patterns simulated by CFD at different rotational speeds were in a good agreement with these by imaging experiments. Thus, the predictive capability of CFD simulation for the liquid flow was encouraging. When the rotational speed was 500 r/min, the liquid ligament was generated at the packing edge as shown in Figures 7(a1, a2). One end of the ligament was attached to the packing edge and the other linked with a droplet. Finally, this “match” shape ligament would be broken into several droplets with different sizes due to the effect of surface tension. As the rotational speed increased to 1500 r/min, more droplets were formed at the packing edge as shown in Figures 7(b1, b2).


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It was very hard to explain the phenomena of these two distinct flow patterns via imaging experiments, but CFD simulation can provide the information of the liquid flow patterns in the outer edge of the packing zone by the post-process step. When the rotational speed was low, the ligament linked with some continuous liquids in the channel of the packing zone. As liquid continuously flowed along the radial direction of the packing zone, liquid was hurled out of the packing zone and transferred to ligaments. As the rotational speed increased, lots of discrete liquid droplets could be found in the packing zone. With the development of liquid flow in the packing zone, these liquid droplets were finally hurled out of packing zone and kept the droplet flow patterns in the outer cavity zone of the RPB reactor. 4.1.2 Liquid flow nearby the shell of RPB reactor Figure 8 displays the simulated and experimental liquid flow patterns near the shell of the RPB reactor. When the rotational speed was low, it looked like liquid film attached on the inner surface of the shell, as shown in Figure 8(a). These films generated by the accumulation of large liquid droplets flowed on the inner surface with the function of the gravity. With the increase of the rotational speed, the liquid films become thinner and liquid ligament patterns appeared as displayed in Figure 8(b). Large quantity of small liquid droplets was accumulated on the surface of the shell quickly, and the thinner liquid film was generated due to the reflective ligaments. It is known that when the liquid droplets impacted on the surface of shell, part of the kinetic energy of liquid droplets converged to internal energy of liquid droplets.22 The rest of kinetic energy of liquid droplets made themselves rebound from the liquid films on the inner surface of the shell. 4.2 Liquid distribution



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The droplets experienced large deformation in the rotation packing zone of RPB reactor, resulting in a chaotic distribution in the outer cavity zone. Figure 9 presents the simulated and experimental profiles of droplets in the outer cavity zone after flowing through the packing zone. It can be found that the liquid droplets were generated at the position of packing edge randomly. The liquid was maldistributed in the outer cavity zone. 4.3 Liquid droplet 4.3.1 Droplet diameter Figure 10 shows the variation of average droplet diameter in the outer cavity zone according to the different rotational speeds and liquid initial velocities. When the liquid initial velocity was 1.91 m/s, the simulated average diameter of liquid droplets in the outer cavity zone first sharply decreased from about 1200 to 500 μm under the rotational speed of 500 ~ 1500 r/min and then slowly decreased from about 500 to 300 μm during the rotational speed of 1500 ~ 2500 r/min, as shown in Figure 10(a). The simulated and experimental average diameters of liquid droplets displayed same characters with liquid initial velocity of 3.58 m/s. It can be concluded that the average diameter of liquid droplets was not influenced by the liquid initial velocity, as shown in Figure 10(b). At the high rotational speed, the liquid was strongly broken into small liquid droplets, which directly influenced the size of liquid droplets. However, high liquid initial velocity just provided more liquids through the packing zone distributing in the outer cavity zone, and it is hard to affect the size of liquid droplets. Figure 11(a) shows that the maximum and minimum relative errors between simulated and experimental average droplet diameter were +31.1% and -10.9%, respectively. Based on the dimensional analysis, the dimensionless groups were obtained as:


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Re 

du 



N 2 2 r  900 g r

(1a)

(1b)

where Re was the Reynolds number and  was the high gravity level (ratio of centrifugal and gravitational acceleration). Re and  were defined in terms of average droplet diameter. d was the hole diameter of liquid distributor, 1 mm. u was liquid initial velocity injected from liquid distributor, m/s.  was the density of water, 998 kg/m3. 

was the viscosity of water, 0.895 mPa · s. N

was the

rotational speed of RPB’s rotor, r/min. r was the outer radius of packing, 40 mm.

g r was the gravitational acceleration, 9.8 m/s2. Based on the above data, the correlation of the average diameter can be fitted as follows: d drop

where d drop

R 2  0.99 (2)  0.0941Re 0.0669  0.4919 d was the average diameter of liquid droplets, mm. d was the hole

diameter of liquid distributor, 1 mm. The experimental and calculated average diameters were compared, as shown in Figure 11(b). It can be found that the CFD simulation and correlation could both reasonably predict the average droplet diameter. The correlation could calculate the average droplet diameter in a very short time. However, CFD simulation could provide more detailed information such as liquid distribution, flow pattern, and velocity, which represented the detailed characters of liquid flow in the outer cavity zone of the RPB reactor. 4.3.2 Droplet velocity Figure 12 presents the effects of rotational speed and liquid initial velocity on the average droplet velocity that was predicted by CFD simulation and measured



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by high-speed camera system separately. It can be observed that the average droplet velocity in the outer cavity zone linearly increased with the increase of the rotational speed, as displayed in Figure 12(a). Figure 12(b) shows that the average droplet velocity was not influenced by the liquid initial velocity. Besides, the liquid velocity was very close to the rotating linear velocity of packing’s outer edge when the rotational speed was less than 2000 r/min. When the liquid reached the outer edge of packing, the velocity was accelerated to the linear velocity of outer edge of the rotating packing, and the liquid radial velocity was decreased because of the resistance of packing. At the high rotational speed, the residence time of liquid was too short. The liquid velocity was difficult to be increased to the velocity of the outer edge of packing. Thus, the liquid velocity was slightly lower than the linear velocity of the outer edge of packing. Figure 13 shows that the simulated results agreed well with the experimental results within a deviation of ±10%.

5. Conclusions The hydrodynamics in the outer cavity zone of the RPB reactor with nickel foam packing was predicted by CFD simulation and observed by high-speed camera system with a “Sudoku” method. Two liquid flow patterns of ligament and droplet were predicted and observed separately. CFD simulation results explained the formation of the above two flow patterns. Liquid distribution in the outer cavity zone was chaotic. Liquid ligaments and droplets were not generated at every position of the packing’s outer edge. The average droplet velocity in the outer cavity zone of the RPB reactor linearly increased with the increase of the rotational speed, while liquid initial velocity did not affect the average droplet velocity. This CFD 12 ACS Paragon Plus Environment

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simulation assisted “Sudoku” imaging experiments is helpful to better understand the hydrodynamic of the outer cavity zone and provide fundamental data to build mathematical model for mass transfer process in the RPB reactor.

Supporting Information CT reconstruction, droplet identification, and mathematical model (PDF)

Acknowledgment This work was supported by the National Key Research and Development Program of China (No. 2017YFA0206801) and the National Natural Science Foundation of China (Nos. 21725601, 21676009, and 21436001).



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Notations d drop

average droplet diameter, μm

d

diameter of liquid distributor hole, mm

gr

gravitational acceleration, m/s2

Re

Reynolds number

u

liquid initial velocity, m/s

Greek letters 

density, kg/m3

μ

viscosity, mPa·s



high gravity level (ratio of centrifugal and gravitational acceleration)


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Ind. Eng. Chem. Res. 2017, 56 (28), 8169-8179. (21) Photron Ltd. Photron Fastcam Analysis Installation Manual. Tokyo Japan, 2015. (22) Hans, C. O.; John, T. M., Physics for Engineers and Scientists. W.W. Norton&Company, Inc.: New York, U.S.A., 2007; Vol. 1.


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Figure Captions Figure 1. (a) Schematic diagram of a RPB reactor; (b) Photo of the nickel foam packing and partially enlarged part. Figure 2. Original X-ray CT images of cut planes (a1) z = 9 mm, (a2) y = 0 mm, and (a3) x = 0 mm; (b) effect of thresholds on area of hole in packing zone. Figure 3. Computational model, mesh, and boundary conditions. Figure 4. Schematic of (a) experimental setup for imaging experiments, (b1) front view of packing zone, and (b2) shooting area. 1. Liquid flowmeter; 2. computer; 3. valve; 4. liquid inlet tube; 5. RPB reactor; 6. nickel foam packing; 7. liquid distributor; 8. high-speed camera. Figure 5. Process to combine 8 images into an image of entire outer cavity zone. Figure 6. Schematic diagram of liquid flow in the outer cavity zone. Figure 7. Typical liquid flow nearby the outer edge of nickel foam packing. (1) CFD simulation and (2) imaging experiments of (a) ligament flow (N = 500r/min, vL = 1.96 m/s) and (b) droplet flow (N = 1500 r/min, vL = 1.96 m/s). Figure 8. Typical liquid flow nearby the shell of the RPB reactor: (1) CFD simulation and (2) imaging experiments under (a) N = 500r/min, vL = 1.96 m/s and (b) N = 1500 r/min, vL = 1.96 m/s. Figure 9. Liquid distribution by (1) CFD simulation and (2) imaging experiments under (a) N = 15 00r/min, vL = 1.96 m/s and (b) N = 2500 r/min, vL = 3.58 m/s. Figure 10. Effects of (a) rotational speed and (b) liquid initial velocity on the average diameter of liquid droplets. Figure 11. Diagonal graphs of (a) experimental and simulation predicted average diameter, (b) experimental and correlation calculated average diameters. Figure 12. Effects of (a) rotational speed and (b) liquid initial velocity on average



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velocity of droplets. Figure 13. Diagonal graph of experimental and CFD-predicted average velocities of droplets.


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Table Captions Table 1. Specification of RPB reactor and operating conditions. Table 2. Specification of high-speed camera and lens.



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(a)

(b) Figure 1. (a) Schematic diagram of a RPB reactor; (b) Photo of the nickel foam packing and partially enlarged part.


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(a2)

(a1)

(a3) Inner Outer

10000

8000

Area (pix)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


6000

30

35

4000

2000

0

0

10

20

30

40

50

Threshold (level)

(b) Figure 2. Original X-ray CT images of cut planes (a1) z = 9 mm, (a2) y = 0 mm, and (a3) x = 0 mm; (b) effect of thresholds on area of hole in packing zone.



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Figure 3. Computational model, mesh, and boundary conditions.


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(a)

(b1)

(b2)

Figure 4. Schematic of (a) experimental setup for imaging experiments, (b1) front view of packing zone, and (b2) shooting area. 1. Liquid flowmeter; 2. computer; 3. valve; 4. liquid inlet tube; 5. RPB reactor; 6. nickel foam packing; 7. liquid distributor; 8. high-speed camera.



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Figure 5. Process to combine 8 images into an image of entire outer cavity zone.


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Figure 6. Schematic diagram of liquid flow in the outer cavity zone.



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(a1)

(a2)

(b1)

(b2)

Figure 7. Typical liquid flow nearby the outer edge of nickel foam packing: (1) CFD simulation and (2) imaging experiments of (a) ligament flow (N = 500r/min, vL = 1.96 m/s) and (b) droplet flow (N = 1500 r/min, vL = 1.96 m/s).


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(a1)

(a2)

(b1)

(b2)

Figure 8. Typical liquid flow nearby the shell of the RPB reactor: (1) CFD simulation and (2) imaging experiments under (a) N = 500r/min, vL = 1.96 m/s and (b) N = 1500 r/min, vL = 1.96 m/s.



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(a1)

(a2)

(b1)

(b2)

Figure 9. Liquid distribution by (1) CFD simulation and (2) imaging experiments under (a) N = 15 00r/min, vL = 1.96 m/s and (b) N = 2500 r/min, vL = 3.58 m/s.


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1800 vL = 1.91 m/s - Sim.

ddrop (m)

1500

vL = 1.91 m/s - Exp. vL = 3.58 m/s - Sim.

1200

vL = 3.58 m/s - Exp.

900 600 300 0

500

1000

1500

2000

2500

N (r/min)

(a) 1500

N = 1500 r/min - Sim. N = 1500 r/min - Exp. N = 2500 r/min - Sim. N = 2500 r/min - Exp.

1200

ddrop (m)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


900 600 300 0

1.5

2.0

2.5

3.0

3.5

vL (m/s)

(b) Figure 10. Effects of (a) rotational speed and (b) liquid initial velocity on the average diameter of liquid droplets.



Simulation predicted ddrop (m)

1500 1200 900

+20%

600

-20%

300 0

0

300

600

900

1200

1500

1200

1500

Experimental ddrop (m)

(a) 1500 1200 Caculated ddrop (m)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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900

+20%

600

-20%

300 0

0

300

600

900

Experimental ddrop (m)

(b) Figure 11. Diagonal graphs of (a) experimental and simulation predicted average diameter, (b) experimental and correlation calculated average diameters.


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12

vL = 1.91 m/s - Sim. vL = 1.91 m/s - Exp. vL = 3.58 m/s - Sim. vL = 3.58 m/s - Exp. linear velocity

v (m/s)

10 8 6 4 2 500

1000

1500

2000

2500

N (r/min)

(a)

12 10

v (m/s)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


8 6 N = 1500 r/min - Sim. N = 1500 r/min - Exp. N = 2500 r/min - Sim. N = 2500 r/min - Exp.

4 2 1.5

2.0

2.5

linear velocity (N = 1500 r/min) linear velocity (N = 2500 r/min)

3.0

3.5

vL (m/s)

(b) Figure 12. Effects of (a) rotational speed and (b) liquid initial velocity on average velocity of droplets.



12

Experimental v (m/s)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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9 +10% 6

-10%

3

0

0

3

6

9

12

CFD-predicted v (m/s)

Figure 13. Diagonal graph of experimental and CFD-predicted average velocities of droplets.


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Table 1. Specifications of RPB reactor and operating conditions. Items

Values

Parameters of RPB reactor Outer radial of outer cavity zone (mm)

120

Outer radial of rotor (mm)

80

Inner radial of rotor (mm)

35

Height of rotor (mm)

18

Specifications of packing Specific surface area (m2/m3)

2916

Porosity

0.96

Aperture

40ppi (0.64 mm)

Operating conditions Rotational speed (r/min)

500, 1000, 1500, 2000, 2500

Liquid initial velocity (m/s)

1.52, 1.91, 2.16, 2.91, 3.58



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Table 2. Specifications of high-speed camera and lens. Items

Values

Parameters of high-speed camera Frame

3600 fps

Shutter

1/10000 s~1/30000 s

Resolution ratio

1024×1024 pix

Parameters of lens Types

AF 200 mm f/4D

Working distance

~500 mm

Field of view

~40 mm


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TOC


CFD Simulation and High-Speed Photography of Liquid Flow in the

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