Error - 'Argument of log must be positive'

Hi all,

I am trying to run a simple model to assess mass flow and temperature in a chain of 3-port gas volumes taken from the ventilation custom libary. However i get an error when running the simulation, see attached images.

The mass flow has been set to 0.5kg/s and a temperature of 200degC used at the reservoir and temperature input to the volume blocks.

Thanks