I will calculate the separation performance of cyclones working at high temperature and high pressure by Fluent. I want to know the following question: I can calculate the properties (density and viscosity) of gas of the given temperature and pressure. Therefore, I have to change the values when beginning simulating. However, after doing this, will I make the energy equation active? Thanks in advance, any suggestions will be important to for.

i would suggest to activate the energy equation, so you can later include the heat loss at the walls of you cyclon if needed. with energy equation active fluent will calculate the ideal gas density from roh=p*M/(R*T). You will supply the molecular weight of your gas in the material panel, the operation pressure in the define->operating conditions panel and the temperature at your boundaries. for dynamic viscosity you can specify a piecewise linear or polynomial function in the materials panel in terms of temperature. i wouldnt care much about pressure since dynmaic viscosity is almost pressure independent.

good luck

rom

Thanks for your useful suggestions. "For dynamic viscosity you can specify a piecewise linear or polynomial function in the materials panel in terms of temperature." I think dynamic viscosity and density are related to each other, for example Re number relates the two parameters. Therefore i think the dynamic viscosity is dependent of the density. Additionally, can you tell me the piecewise linear or polynomial function between the temperature and dynamic viscosity. Thanks a lot.

there are two definitions of viscosity. the dynamic viscosity (dv) and the kinematic viscosity (kv). in the material panel you will input the dv in (Pa*s) where kv can be calculated from kv=dv/density. dv is almost pressure independent. i dont know what gases do you use so i cant give you a function for dv in terms of temperature. a rough estimate for flue gases at about 1000°C is 4e-5 Pa*s.

good luck

rom

Thanks for your reply. I will not take into heat loss at the walls account in my simulation. In this condition, will I activate energy equation? In addtion, I indeed use the flue gases, but the forum displays " A rough estimate for flue gases at about 1000°C is 4e-5 Pa*s" , so I don't see it correctly. Would you like send it to me again? Thanks a lot.