I aim to develop a mathematical model for finding out emanation rates of Insect Repellant Liquid Vaporiser. A porous wick is dipped in a multi-component liquid in a container. Liquid is climbing to the top of the wick, getting heated by the heater and evaporating.

I have formulated the governing equation for fluid flow in the porous wick. In this equation - the density, viscosity and surface tension is assumed constant. However, in the real-life situation, the liquid rising up in the porous wick consists of two hydrocarbon solvents (D80 - more volatile and D130 - heavier one). D130 constitutes larger portion. As a result the liquid properties change, as more liquid vaporises from the top. How do I take into account in my model this change, the impact of viscosity, surface tension and even density variation?