Abstract
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.