Original scientific paper https://doi.org/10.2298/TSCI170911058Y In order to evaluate the irreversibility and exergy losses of the regenerators in a solar beta-type free piston Stirling engine due to flow friction, 1-D thermodynamic model to quantify exergy loss in the regenerators are built. The effects of important parameters, such as oscillating flow pressure drop, the exergy loss to flow friction, the exergy losses to conduction heat transfer at the hot and cold side of the regenerator and

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... he percentage of Carnot efficiency of Stirling engine are presented and studied in detail. Results show that exergy loss decreases with the increase of the porosity and matrix diameter. As for the regenerator length, there is an optimum value that is equal to 0.035 m where the exergy loss is minimal and the percentage of Carnot efficiency is maximal. Therefore, some parameters should be selected reasonably to meet the overall design requirements of a solar Stirling engine.