Example of a Thermodynamics Problem that Cannot Be Solved with Only the Mass and Energy Balances^{7}
A compressor is a gas pumping device that takes in gas at low pressure and discharges it at a higher pressure. Since this process occurs quickly compared with heat transfer, it is usually assumed to be adiabatic; that is, there is no heat transfer to or from the gas during its compression. Assuming that the inlet to the compressor is air [which we will take to be an ideal gas with C_{ P }^{*} = 29.3 J/(mol K)] at 1 bar and 290 K and that the discharge is at a pressure of 10 bar, estimate the temperature of the exit gas and the rate at which work is done on the gas (i.e., the power requirement) for a gas flow of 2.5 mol/s.
^{7}We return to this problem in the next chapter after formulating the balance equation for an additional thermodynamic variable, the entropy