MAE 204 Thermodynamics Chapter 1 1 MAE 204 Thermodynamics Why is thermo hard? 1. Abstract ideas: We probably know what heat is, but what is enthalpy? 2. Use of table and charts. 3. Wide range of subject. 4. Trouble with units. 5. Extremely cumulative. Motivation: 1. Thermodynamics is a study of energy exchange. 2. How can we convert energy to work? Example: A gas-turbine system has a compressor, combustion chamber and a turbine. Combustion Chamber Comp. Turb. W Back W Net Fresh Air Exhaust Gas Fuel This is an open system, as the working fluid (air) does not remain in the system. To make it closed, the equivalent system will look like: (The total output work W Net depends on the fluids states, which is the area enclosed by the curves) Heat Exchanger Comp. Turb. W Back W Net 1 4 Heat Exchanger 2 3 Q In Q Out v P 1 4 2 3 Brayton Cycle