Here " S " is the entropy of the system; " T " k is the temperature at which the heat flow \ dot Q _ k enters the system; \ dot S _ k = \ dot n _ k S _ { mk } = \ dot m _ k s _ k represents the entropy flow into the system at position " k ", due to matter flowing into the system ( \ dot n _ k, \ dot m _ k are the molar flow and mass flow and " S " mk and " s " k are the molar entropy ( i . e . entropy per mole ) and specific entropy ( i . e . entropy per unit mass ) of the matter, flowing into the system, respectively ); \ dot S _ { ik } represents the entropy production rates due to internal processes.
