Hi SRP and thank you for your response. I have already checked the previous discussion and could not solve the issue yet. The solution never diverges and fluctuates at each DPM update interval. I think the problem lies in the material section and the physical properties that I have. I am not sure if I have defined correct materials.

I have velocity inlet ( I convert L/min to m/s based on the inlet area) and pressure outlet and have defined H2o (water vapor) based on the 50% relative humidity at both inlet and outlet species. The list of materials I used is attached. I have water in my drugsmi which evaporats so I defined water vapor at both fluid and species. I also have air in both. The drug you see in the list has water vapor physical properties and has mass fraction of 0 in the species. 

Please let me know if you need more information.