Internal energy transfer theory is motivated from the thermodynamic
point of view in which internal energy transfer depends
on intensive state variables as well as extensive state variables.
Internal energy transfer in a quasi-equilibrium (quasi-static) process
is conventionally described only by extensive state variables,
but internal energy in a non-equilibrium process can be stated
by including intensive state variables. Here, the dependence of
intensive state variables for internal energy transfer is addressed.
Euler’s equation of thermodynamics for the internal energy is