According to the relationship between generalized force and generalized flow

established all phase entropy generation rate equation

and analysed the relationship between entropy flow and total entropy generation of system. The results show that when the steady state

the decreasing of total entropy generation of system

the increasing of entropy flow and heat transfer

specifically

in the case that heat and mass transfer processes are both spontaneous process. When mass flow and heat flow are in the same phase

the decreasing of phase difference between mass flow and heat flow

the increasing of heat transfer

which reflects field synergy mechanism of energy transfer between two spontaneous process， with positive entropy generation rate

while in the case that heat transfer is nonspontaneous process， and mass transfer is spontaneous process. When mass flow and heat flow are in the opposite phase

the increasing of phase difference between mass flow and heat flow

the increasing of heat transfer

which reflects the thermodynamic coupling mechanism of energy conversion between spontaneous process

with positive entropy generation rate，and nonspontaneous process

with negative entropy generation rate. Between mass flow and heat flow from the same phase to the opposite phase

corresponding to the energy transfer mechanism of field synergy

and the energy conversion mechanism of thermodynamic coupling

all reflecting the minimum entropy generation principle for convective heat transfer.