Derivation of the macroscopic energy balance, show how to integrate Eq. (N) of Table 11.4-1 over the entire volume V of a flow system, which, because of moving parts, may be a function of time. With the help of the Gauss divergence theorem and the Leibniz formula for differentiating an integral, show that this gives the macroscopic total energy 'balance Eq. 15.1-2. What assumptions are made in the derivation? How is Wm to be interpreted?