We postulate the total energy balance (the first law of thermodynamics) and
derive the third equation of the fluid model, the internal energy density balance
equation. The kinetic energy of the body is defined and its balance is discussed. The
power of forces acting on the body is also discussed. The notion of internal energy is
introduced, and its balance is considered. Finally, we formulate the complete system of
equations of the fluid model.
Keywords: Energy balance, Equation of state, First law of thermodynamics,
Force power, Heat flux, Internal energy, Kinetic energy, Mechanical energy,
Potential energy, System of fluid model equations, Total energy.
