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September 6, 2013, 15:01 
Spray dryer atomization

#1 
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Luis García
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Hi, I'm working in drying of tomato juice in my university. There are a tiny equipment in the school which i have to simulate in ANSYS Fluent. I am very new in fluent so I will be so grateful if you could help me. In order to understand fluent i had done some tutorial like "Modeling Evaporating Liquid Spray" and others. However there are a lot of things that i don't know. Firstly, i began making the chamber in SolidWorks. These has one outlet, one velocity inlet for the hot air, and another for the atomizer; this has an outlet of 0.7mm of area. This atomizer is a pressurenozzle. I did the mesh for Fluent with inflation: program controller and smooth transition through the workbench of ANSYS 14. In fluent, I used the gravity, the energy model, realizable Ke viscous, Species transport for the hot air( O2, H2O, N2) and the discrete phase for the atomizer. However the atomizer is for tomato juice so i have to use a multiphase but i don't know how to do it and if my model is correct. In order to simulate the nozzle I draw a similar air nozzle as the tuto "Modeling Evaporating..." however i don't know if this is necessary or is enough just an injection. If someone can help me. There are some pictures of this work.Thanks.


September 6, 2013, 15:10 
Some Pictures

#4 
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Luis García
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September 6, 2013, 15:18 
Zones

#5 
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Luis García
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Similar to the tuto, i used 3 inlet zones [coflowrateinlet : hot air, centralair: (massflowinlet) for tomato juice, and swirlingairinlet : pressure air]. And only one pressureoutlet. Could you open the pictures in Drive?


September 6, 2013, 15:53 

#6 
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Ghazlani M. Ali
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ok start by a very simple case , then make it more complex step by step.
Disable multiphase first, and use steady particle tracking, use 20 iteration per dpm calculation. have you done that ? 

September 6, 2013, 17:48 
Simple Case

#7 
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Luis García
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Ok First, thanks for your help. I made the first case without a second phase. I put the models that i use and more information in the doc:
Gravity z:9.81 1. Energy Model: ON 2. Viscous: Realizable Ke, Standard Wall Fn 3. Species: a. MethylAlcoholAir(4 Number of Volumetric Species) b. Inlet Diffusion c. Diffusion Energy Source 4. Discrete Phase Model: a. Interaction with Continuous Phase b. Number of Continuous Phase Interaction per DPM Interation> 20 c. Steady Particle tracking d. Any Physical Model 5. Injection0 a. Type: pressureswirlatomizer b. # of particle streams: 60 c. Particle Type: Droplet d. Material: Methylalcoholliquid e. Evaporating Species: Water f. Position: x=0, y=0, z=0.0015 g. Axis: X=0, Y=0, Z=1 h. Temperature: 25°c,298°K i. Flow Rate: 8.5e0.5 Kg/s j. Injection Inner Diameter(m)=0.00025 k. Spray Half Angle: 45° l. Upstream Pressure: 1000000Pascal m. Azimuthal Start Angle:0° n. Azimuthal Start End:180° o. Sheet Constant: 12 p. Ligament Constant: 0.5 q. Atomizer Dispersion Angle: 6 6. Boundary Conditions Central Air Inlet: Type: MassFlowRate MassFlowRate: 9.167e05 Kg/s Direction Vector: (0,0,1) Turbulence: Intensity and Viscosity Ratio(10%,10%) Temperature: 298°K Species: 0.23 n2, 0 o2, 0 h2o Coflowrateinlet: Hot Air Type: Velocity Inlet Temperature 373 °K Turbulence: Intensity and Viscosity Ratio(5%,5%) Swirligairinlet: High pressure air Type: Velocity Inlet Temperature: 298°K Velocity: 30 m/s Cylindrical coordinate System: 0, 0.7071, 0.7071 Turbulence: Intensity and Viscosity Ratio(5%,5%) Outlet Type: Pressureoutlet Temperature: 298°K Turbulence: Intensity and Viscosity Ratio(5%,5%) I made 300 iteration to start but it doest converge :S maybe much more 

September 8, 2013, 08:53 

#8 
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Ghazlani M. Ali
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have you first solved the cold flow ? do you have any information about your nozzle like angle and pressure of operation ? Why are you using any physical model for the droplets ?


September 8, 2013, 15:14 
Corrections and atomization characteristics

#9 
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Luis García
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Thanks you diamondx, you are right. First i have to remove the injection, so, we have three models, energy, viscous and species transport. I do this in order to solve the cold flow? right.
The information that i have about the nozzle is that it is a pneumatic double flow atomizer from Buchi, which is working at 250 KPa (2.5 bar), air flow rate is 7.6 Kg/h and 0.09 Kg/h of tomato juice, droplet size is 125um(dp=5um), nozzle diameter is 0.7mm(7e4m) and 0° angle. 

September 8, 2013, 16:29 
I used this models...

#10 
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Luis García
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1. Modelo de Energía: ON
2. Viscocidad: Realizable Ke, Standard Wall Fn 3. Species: a. MethylAlcoholAir(3 Number of Volumetric Species) b. Inlet Diffusion c. Diffusion Energy Source 4. Condiciones de Frontera (Boundary Conditions) Central Air Inlet: Jugo de tomate Type: MassFlowRate MassFlowRate: 9.167e05 Kg/s Direction Vector: (0,0,1) Turbulence: Intensity and Viscosity Ratio(10%,10%) Temperature: 273+25°K=293°K *(Species: 0 ch3oh, 0.21 o2, 0 h2o, 0 air) i don’t know Coflowrateinlet: Aire Caliente Type: Pressure inlet Pressure: 100 000 Pascal Temperature 408 °K (135°C) Turbulence: Intensity and Viscosity Ratio(5%,5%) Gauge total pressure=100 000 P Turbulence: Intensity and Viscosity Ratio(5%,5%) (Species: 0 ch3oh, 0 o2, 0 h2o, 1 air) Swirligairinlet: Aire a presión Type: Pressure Inlet Temperature: 298°K (25°C Pressure: 250 000 Pascal Turbulence: Intensity and Viscosity Ratio(5%,5%) (Species: 0 ch3oh, 0 o2, 0 h2o, 1 air) Outlet Type: Pressureoutlet Temperature: 358°K (85°C) Turbulence: Intensity and Viscosity Ratio(5%,5%) (Species: 0 ch3oh, 0 o2, 0 h2o, 0 air) it is converged at 345 iterations, now ill put the injection... case and data of this : https://docs.google.com/file/d/0Bz3M...it?usp=sharing 

September 8, 2013, 17:18 
Discrete phase model and Injection

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Luis García
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Now I try to simulate the injection with this parameters:
5. Discrete Phase Model: a. Interaction with Continuous Phase b. Number of Continuous Phase Interaction per DPM Interation> 20 c. Unsteady Particle tracking i. Particle time step size: 1e03 ii. Number of time steps: 1000 (is this for in 1 second, one particle every 0.001 s?) d. Physical Models: i. Breakup I just can use this because DEM Collision is not enable with breakup model, What more I need? e. Drag parameters Should I use dynamicdrag or spherical?, I used dynamicdrag Injection0 a. Type: pressureswirlatomizer b. # of particle streams: 2 c. Particle Type: Droplet d. Material: Methylalcoholliquid e. Evaporating Species: Water f. Position: x=0, y=0, z= 0.0050 g. Axis: X=0, Y=0, Z=1 h. Temperature: 25°c,298°K i. Flow Rate: 0.000025 Kg/s (0.09 Kg/h) > 0.045 Kg/h because I just simulate a half j. Start time: 0s, stop time: 60 s j. Injection Inner Diameter(m)=0.000025 k. Spray Half Angle: 0° l. Upstream Pressure: 250000Pascal m. Azimuthal Start Angle:0° n. Azimuthal Start End:30° o. Sheet Constant: 12 p. Ligament Constant: 0.5 q. Atomizer Dispersion Angle: 6 Turbulent dispersion  Discrete random walk model  Random eddy lifetime Materials Material Type: droplet particle Density: 1019 Kg/m^3 Cp: 4077 J/Kg°C Viscosity: 103 .55 din*s/cm^2 (10.355 Pa*s) Droplet surface : 0.0222 However I am not sure about many things :S 

September 9, 2013, 17:34 
Injection

#13 
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Luis García
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I used water as evaporating species because the liquid injection is tomato juice, moisture is 95.2% with a concentration of 22 of solids. How can i simulate this mixture?. Other thing, there is some picture where i can see all the parts of an injection. Because in the theory guide don't have a good information of this. I am not sure about some characteristics.


September 10, 2013, 14:07 

#14 
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Ghazlani M. Ali
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you need to refine the mesh ! see what it does. in the evaporating species , the material has to be the same as the one used it the mixture... any progress ?


September 18, 2013, 13:49 
Refine mesh

#15  
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Luis García
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Quote:
I refined the mesh however now it doesn't converge... some idea? what am i doing wrong? Or its ok? Last edited by luisUTM; September 18, 2013 at 18:46. 

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