Learning Forum

[Mehdi Salakhi]

I did a simulation with the particle combustion module in Ansys Rocky. However, the value of heat of radiation rate I calculate by hand is totally different than the value I get from Rocky. Therefore, I just changed the heat of radiation rate to a fixed value (like 1 W) in the C++ code, and compiled the code. I was expecting to see a 1 W value, but it shows a garbage value attached in the screenshot. There is nothing much I can do for this problem, so I was thinking maybe there is a bug in the core of the code to which I don't have access. I was wondering can someone help me with this?

[Rob]

 

I’ve not tried that module (yet) but do know the radiation models are less developed than in Fluent. Are you coupling with Fluent, and how high is the solids fraction? I can't see the image, but suspect that's a forum issue, hopefully that'll turn up when they fix whatever else went wrong overnight. 

 

[Mehdi Salakhi]

Thanks for your reply!

To answer your questions:

Are you coupling with Fluent? yes as the combustion module is only applicable by coupling with CFD!

how high is the solids fraction: so it's a fluidized bed with a height of almost 0.1 out of 0.5 m. 

The problem is not related to any physical concept. For the starter, let's forget about any physical concept like radiation heat transfer. In the combustion module, I just defined the rate of heat transfer to be a fixed value of 1 W and I'd expect to see this value in the UI of the software as well no matter what happens. But it is showing a totally different fixed value. I tried to attach the screenshot again. Hopefully, you could see it!

[Rob]

Where did you set the heat transfer rate? Just wondering if it's W/m2 or W/m3 that you've set. 

[Mehdi Salakhi]

Thanks for your reply!

I also checked the units. The heat transfer here is defined for solid particles as the following equation.  So, the unit is W.

mc(dT/dt)p=qreaction + qradiation

Where did you set the heat transfer rate?

As you may know, Rocky has ready-to-use costume modules that can be added to the software. Inside the source code of the particle combustion module, I just corrected the radiation heat transfer to 1 W.

 

[Mehdi Salakhi]

Here I also wanted to show the part of the code that calculates the heat transfer rate

 //double rate_heat_radiation = particle_area * data->emissivity * data->stefan_boltzmann * (pow(gas_temperature, 4.0) - pow(particle_temperature, 4.0));

    double rate_heat_radiation = 1; //this is what I corrected

[Rob]

I think you're looking in the wrong bit of the API. I've heard back, and what I'm seeing isn't what you have in the above. However, I also can't post information that's not in the publically available documentation. Rocky documentation isn't in the normal install, so I need to see if it's in the imminent 22R2 version. 

What you do need to look for are some non-dimensional terms in the macros: I don't think you're adding the correct amount of heat.