hi,I have a question:in my diffusion model,when I have done the iteration,I want to see some cocentration of each species,but when I use two different units of mass fraction and mole fraction,the solutions are the same(the numbers in each nodes in mass fraction are the same as those in mole fraction).I do not know the reason,are these two units same? thank for your help

No. Mole fraction is volume fraction.

If the molecular weights of two species are the same, then mole fraction and mass fraction are the same.

Anyway, the trend(pattern) of mole fraction and mass fraction is always the same. The difference is only absolute value.

Sincerely, Jinwook

I know only when the molecular weights of the species are same,the two units are same. But in my solution ,the absolute values are the same as well as the trend. Can you help me finding the probably reasons? thank you

If molecular weights of two species are the same, absolute values of mass fraction and mole fraction, as well as the trend, should be the same.

Otherwise(if molecular weights are not the same), it is, as far as my experience, impossible solution and I never think such situation occur Fluent's simulation result. It's only post processing.

Sincerely, Jinwook

Sorry,I've made a mistake.The absolute values are not the same exactly,but they are so low that the difference between them are uneasy to see.Thank you for your help.