Which of the following is NOT a form of energy in the General Energy Equation?

Which of the following is NOT a form of energy in the General Energy Equation?

• A. Potential Energy (PE)
• B. Kinetic Energy (KE)
• C. Flow Energy (FE)
• D. Thermal Energy

Answer: (D)

The key idea is how the General Energy Equation accounts for energy in a control volume. In this formulation, the energy terms you actually balance explicitly are kinetic energy, potential energy, and flow energy. The flow energy term represents the energy carried by the fluid due to its motion and also accounts for the work required to push the fluid into or out of the control volume (the pV work). The internal, microscopic energy associated with temperature—what we often call thermal energy—is not treated as a separate term. It is already included in the enthalpy term, h, since h = u + p/ρ, which combines the internal energy (thermal energy) with the flow work. So there isn’t a distinct “thermal energy” form in the General Energy Equation; it’s embedded within enthalpy. Therefore, thermal energy is not a separate form of energy in this equation.

The key idea is how the General Energy Equation accounts for energy in a control volume. In this formulation, the energy terms you actually balance explicitly are kinetic energy, potential energy, and flow energy. The flow energy term represents the energy carried by the fluid due to its motion and also accounts for the work required to push the fluid into or out of the control volume (the pV work). The internal, microscopic energy associated with temperature—what we often call thermal energy—is not treated as a separate term. It is already included in the enthalpy term, h, since h = u + p/ρ, which combines the internal energy (thermal energy) with the flow work. So there isn’t a distinct “thermal energy” form in the General Energy Equation; it’s embedded within enthalpy. Therefore, thermal energy is not a separate form of energy in this equation.