Sensitivity analysis of dependency of working fluid thermo-dynamics properties to temperature on performance of Gama-type Stirling engine

This research proposes the effect of temperature variation in the Prandtl number on the power, the efficiency and the heat loss of the Gama-type Stirling engine. It should be noted that the Prandtl number included the viscosity, the thermal conductivity coefficient and the specific heat at constant pressures of the working fluid, which the temperature dependency of such first two thermo-dynamics properties were studied in this article. For this objective, a thermo-dynamics code based on the non-ideal-adiabatic method was firstly written to consider losses, including the engine pressure drop and the regenerator heat loss. In the second stage, such code was validated by experimental data. Then, results at 8 bar of the pressure, 970 rpm of the speed for three working fluids of air, helium and hydrogen were obtained within the hot source temperature of 350-750°C and for two conditions of constant Prandtl number and variable Prandtl number with the temperature. Obtained results demonstrated that the variation value for the power, the efficiency and the heat loss was less than 12%, 6% and 5% for air, helium and hydrogen, respectively, where the maximum change was observed in the engine power. Finally, using the regression analysis, the sensitivity value of the variation percentage of the Stirling engine performance was determined for three working fluids and under two conditions of constant and variable Prandtl number.