yes, I do understand the equation ... but what happens is when you have all the liquid in the cell evaporating, the temperature decreases ... this causes the solver to re-apply the equation and condenses all the vapour ... the temperature in the cell increases ... and so on. In addition to having energy balance between the cells, this becomes a a tough process for the solver to reach solution.nWhat happens in reality is ... the temperature increases, then part of the liquid evaporates until the temperature reaches saturation ... not all the liquid. So, the coefficient should not be 1 ... The default value is 0.1 .. you can increase it to 0.2 .. 0.5 ... but 1 will end up with numerical instability n