Automobile Exhaust Gas Heat Energy Recovery Using Stirling Engine: Thermodynamic Model

Higher fuel economy of the vehicle is a critical concern in automobile industry. Traditional internal combustion (IC) engines waste a large portion of the available fuel energy as heat loss via exhaust gas. This proposal aims at recovering the available exhaust heat of the IC engines using stirling engine (SE) as an add-on device. SE is a type of cyclic heat engine which operates by compression and expansion of the working fluid, at different temperature levels resulting in a conversion of the heat energy into mechanical work. A thermodynamic analysis is performed on the chosen beta SE rhombic drive configuration with different combinations of design parameters like working fluid mass, total dead volume, thermal resistance, and hot side and cold side temperatures. A regenerator temperature model is developed to account for first law consistency in the regenerator section of SE, along with heat transfer in accordance with mass flow within the regenerator. In conclusion, the results indicate that a device based upon the typical tube fin type compact heat exchanger and Hydrogen as working fluid will have a working fluid volume of about 7.8 liters with 1016 W power at 12.65% thermal efficiency. For similar power output (1028 W), a smaller heat exchanger like the printed circuit heat exchanger (PCHE) requires 3.25 liters of working fluid volume at 10.85% thermal efficiency.