Use the Wall Mass Transfer node to model species loss to the surroundings of the pipe. This could be used if the diluted species is soluble in the pipe wall or if the pipe wall is semipermeable. A mass transfer coefficient is used to model the loss rate, and external bulk concentration i specified to define the driving force.

For each species, enter a Mass transfer coefficient kwall,c (SI unit: m/s). The default is 0 m/s. For each species, select an option from the list (when available) or define the Bulk concentration cbulk (SI unit: mol/m3). The default is 0 mol/m3.