Parametric study of a low-temperature differential Stirling engine for low-grade thermal energy recovery

In the present study, a theoretical basis for design and performance evaluation of low-temperature differential Stirling engine (LTDSE) of gamma type using finite time thermodynamic analysis has been evolved. The influence of various thermodynamic parameters such as finite heat capacitance rate, the effectiveness of heat exchangers, the effectiveness of regenerator on thermal efficiency at maximum power output condition and work output of LTDSE is investigated. The geometrical parameters such as phase-angle, swept volume ratio, and dead volume ratio have been integrated with finite time thermodynamic model for the first time. An increase in finite heat capacitance rate and the effectiveness of heat exchangers increases work output while improvement in effectiveness of regenerator raises thermal efficiency. Although, an increase in compression ratio and swept volume ratio improves the work output and thermal efficiency at maximum power output condition, any change in any of these parameters affects the size/characteristics of LTDSE. Therefore, large diameter displacer with less stroke length are required to keep the compression ratio and swept volume ratio at a high value. The work output and thermal efficiency at maximum power output condition depend largely on swept volume ratio rather than dead volume ratio.