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Modelling of tablets drying

Modelling of tablets drying

Modelling of tablets drying

Dear All,

I develop a model (in Fluent) that will simulate the drying process of a bunch of tablets stored in a chamber. Tablets are dried by the air that is pumped to the chamber (through a single inlet) and penetrates a perforation plate (on which tablets are put on) and then it penetrates tablets (finally the air leaves the chamber through a single outlet).

The tablet consists of two layers: bulk (softer material) and coating (harder material). Tablet size is approx. 17mmx17mmx7mm. Porosity of a bunch of tablets is approx. 0.4 (air volume/overall volume).
I have some empirical data, as a reference point for validation. I have measured the drying rate of tablets inside the chamber (a water content in tablets before and after drying process, measured over a specific period of time).

In the CFD drying analysis, the most important aspects will be:
- Prediction of a drying rate of tablets, for a given air velocity applied to the inlet (effectively, for air velocity in specific areas of the drying chamber).
- I think that I will need to take into account the increasing humidification of the air as it flows through a bunch of tablets. As the air collects the water from tablets located nearest to the inlet, its ability to collect the water from tablets located near to the outlet decreases (at least at the beginning of the process).

According to my research, the drying model could be set up as follows:
- A bunch of tablets can be represented by the porous medium.
- A perforation plate can be represented by the porous jump.
- The drying of tablets can be modelled with use of the DDPM.

I am seeking for the advice whether:
1. The combination of the porous medium (volume approx. 0.5m^3) and DDPM can work
2. The combination of the porous jump and DDPM is ok.
3. I have already developed a (working) model that includes the porous medium and the porous jump (without DDPM). This model shows the airflow distribution across the chamber, the differences of velocities across the porous medium, etc.
Since from this model I know that in a specific area of the porous medium the air velocity is e.g. 50mm/s, would it make sense to develop the drying model for a single tablet, exposed to the airflow of 50mm/s. In such a solution though, the described earlier effect of air humidification could not be taken into account.
4. Perhaps you could suggest another approach to modelling of the described scenario.
5. I would be grateful for your tips and a little guidance on how to proceed with development of the model.

Thank you.

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