4. Exergy variation of an open system

Consider (figure 2 ) a closed system (SF) including at time t a certain mass m located within a control volume of an open system and a mass dm at the entrance to this control volume. During time interval dt, mass dm enters the control volume. At time t + dt, the closed system coincides with the open system. The exergy variation of the closed system, in the absence of chemical reactions, between time t and time t + dt is written according to equation (17) :