How do you calculate approximately the triple point and critical point of any given CH-based gas mixture?
I have developed a software which uses iterations to find bubble point and dew point of any CH-based gas mixture. It uses Peng-Robinsson EOS and Van Der Vaals mixing algorithm.
When calculating the dew point pressure for a certain temperature, it's difficult to know the starting range for the iteration. First I used False-Position method in finding the root, but now I have switched to Bisection. Although it's slower, it's more safe as it's not affected by function derivatives.
What would be needed is as approximation of the range where the liquid/vapour phases are found. Setting the iteration's range to start below triple point pressure, or above critical point pressure will cause the iteration to diverge and never find a root.