Learning Forum

[bfialkoff]

Hi

I need to simulate an autoclaves operating conditions and monitor the temperature of the autoclave as a function of time. The autoclave has two inlets and one outlet. One of the inlets introduces a bi-phase chemical fluid (liquid/solid) which undergoes a reaction with the oxygen (that is introduced in the second inlet). I am having a hard time understand what time of simulation i need to run over here. I've been reading through the theory guide to try and understand what needs to be accounted for. I know that all the basic transport and conservation equations need to be solved, I'm just not sure exactly how to define the simulation scenario.

Any help would be greatly appreciated.

I'm happy to provide further clarification if need be.

[peteroznewman]

A sketch of the geometry showing where the inlets and outlets are and where the heat is applied would help members to visualize the problem.

[MANUNAYAK]

Hi,

Considering your inputs I understand that you need to monitor the temperature history inside autoclave during transient calculation. First, you have to be aware of specific autoclave working process in real application to decide the total physical time that you want to simulate using CFD. And accordingly choose your time step based on your mesh size. As you mentioned that the working fluids may undergo chemical reactions, this may take additional equations into the account during calculation process and hence more time.

[Rob]

As Peter says, the best starting point is to sketch the geometry (roughly to scale) on a piece of paper and dimension it. Then write on all the flow rates & of what enter through each boundary. Which solver do you plan on using?

You're probably going to need a multiphase model, heat transfer, some chemistry and possibly turbulence. I can't be more specific than that at present, and as staff I can only offer limited guidance anyway. 

[bfialkoff]

The second paragraph @rwoolhou mentions is in fact what I am primarily interested in understanding since once the appropriate model becomes clear the implementation will become fairly straightforward. My understanding is that my scenario is a case of a bi-phase, turbulent, reactive, and compressible flow involving heat transfer.  As such we are required to solve equations for conservation of mass and momentum (basic flow), energy (heat), and species (chemistry).

Can anyone clarify whether or not this is correct?

Assuming what I wrote above is correct I am still unclear on how to approach the specifics of each scenario. For example:

In the case of the energy equation the method of heat transfer is critical. How can I determine if my case is one of conductance/convection or if I need to account for natural convection?

Does the creation of new species due to chemical reaction affect the form of the source term in the mass equation?

How do I account for the presence of an agitator in the autoclave chamber? Is this accounted for in turbulence or do I need to involve a rotating reference frame or is there yet another method?

How can I determine whether or not the dilute approximation for species transport is acceptable, or if full multicomponent diffusion is required?

In my reaction I know the reaction rates are approximated according to Arrhenius kinetic expressions. How do I choose the appropriate reaction rate model?

 

 

[Rob]

I think we'll need a sketch with some figures to understand what assumptions can be made. It's also likely that ANSYS staff won't be able to offer too much assistance as it'll get too specific: we're limited in what we can say on a public forum. Hopefully the wider community will be able to help.