I am working on absorption refrigeration system using LİCl-H2O. I used state points of a article. I confronted a problem using Engineering Equation Solver (EES). Error showed by EES: This equation attempts to raise a negative number to a non-integer power.How can it be fixed ?
EES uses nonlinear iterative solvers to find the solution to the problem. Specifying the bounds of your variable is a good practice to accelerate the convergence. Default limits in the EES are set as - infinity to +infinity. If you are sure that your variables are positive, then try changing the limits of the variables. In your case, specifically change the limits of the variable which is being raised to the non-integer power (set the limits as 0 to infinity).
I haven't seen the equation, but I would imagine there are many better ways of solving it than EES. Many common equations can be solved with Excel. If you can't force EES to consider only positive values, you can simply make a change of variables. For example solving for (a^2)^(b/2) is the same as a^b except that you always have a positive result.