Recall that we wrote the First Law of Thermodynamics as: The above only applies for a STEADY FLOW process, I.e. a process where none of the properties inside the control Volume (C.V.), including energy, are changing with time. The turbine problem is an example of a steady process. If the process is unsteady, i.e. transient, the total amount of energy inside the system (or CV) can change. The First Law for such a process is given by: Where dECV/dt is the rate of change in the total energy of the Control Volume. First law-ex-1