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September 6, 2013, 15:01 |
Spray dryer atomization
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#1 |
New Member
Luis García
Join Date: Sep 2013
Posts: 9
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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 pressure-nozzle. 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 K-e 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.
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September 6, 2013, 15:10 |
Some Pictures
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#4 |
New Member
Luis García
Join Date: Sep 2013
Posts: 9
Rep Power: 12 |
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September 6, 2013, 15:18 |
Zones
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#5 |
New Member
Luis García
Join Date: Sep 2013
Posts: 9
Rep Power: 12 |
Similar to the tuto, i used 3 inlet zones [co-flow-rate-inlet : hot air, central-air: (mass-flow-inlet) for tomato juice, and swirling-air-inlet : pressure air]. And only one pressure-outlet. Could you open the pictures in Drive?
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September 6, 2013, 15:53 |
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#6 |
Super Moderator
Ghazlani M. Ali
Join Date: May 2011
Location: Tokyo, Japan
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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 ? |
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September 6, 2013, 17:48 |
Simple Case
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#7 |
New Member
Luis García
Join Date: Sep 2013
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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 K-e, Standard Wall Fn 3. Species: a. Methyl-Alcohol-Air(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. Injection-0 a. Type: pressure-swirl-atomizer b. # of particle streams: 60 c. Particle Type: Droplet d. Material: Methyl-alcohol-liquid 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: 8.5e-0.5 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: Mass-Flow-Rate Mass-Flow-Rate: 9.167e-05 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 Co-flow-rate-inlet: Hot Air Type: Velocity Inlet Temperature 373 °K Turbulence: Intensity and Viscosity Ratio(5%,5%) Swirlig-air-inlet: 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: Pressure-outlet Temperature: 298°K Turbulence: Intensity and Viscosity Ratio(5%,5%) I made 300 iteration to start but it doest converge :S maybe much more |
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September 8, 2013, 08:53 |
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#8 |
Super Moderator
Ghazlani M. Ali
Join Date: May 2011
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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 ?
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September 8, 2013, 15:14 |
Corrections and atomization characteristics
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#9 |
New Member
Luis García
Join Date: Sep 2013
Posts: 9
Rep Power: 12 |
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 1-25um(dp=5um), nozzle diameter is 0.7mm(7e-4m) and 0° angle. |
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September 8, 2013, 16:29 |
I used this models...
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#10 |
New Member
Luis García
Join Date: Sep 2013
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1. Modelo de Energía: ON
2. Viscocidad: Realizable K-e, Standard Wall Fn 3. Species: a. Methyl-Alcohol-Air(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: Mass-Flow-Rate Mass-Flow-Rate: 9.167e-05 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 Co-flow-rate-inlet: 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) Swirlig-air-inlet: 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: Pressure-outlet 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 |
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September 8, 2013, 17:18 |
Discrete phase model and Injection
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#11 |
New Member
Luis García
Join Date: Sep 2013
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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: 1e-03 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 dynamic-drag or spherical?, I used dynamic-drag Injection-0 a. Type: pressure-swirl-atomizer b. # of particle streams: 2 c. Particle Type: Droplet d. Material: Methyl-alcohol-liquid 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 |
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September 9, 2013, 17:34 |
Injection
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#13 |
New Member
Luis García
Join Date: Sep 2013
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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.
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September 10, 2013, 14:07 |
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#14 |
Super Moderator
Ghazlani M. Ali
Join Date: May 2011
Location: Tokyo, Japan
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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 ?
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September 18, 2013, 13:49 |
Refine mesh
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#15 | |
New Member
Luis García
Join Date: Sep 2013
Posts: 9
Rep Power: 12 |
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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