A CFD Analysis of the Air Flow through the Matrix Regenerator of Stirling Engines

In this paper, a thermo-fluid dynamic 3-D numerical model of the air flow through the stacked woven matrix of Stirling engines regenerators has been used to characterize the pressure drop and heat transfer through the regenerator. Firstly, an isothermal flow, at 293 K, through the porous media has been analyzed. Four different matrices have been considered, two aligned and two misaligned and the simulations have been carried out over a range of Reynolds numbers from 5 to 2000. Two friction factor correlations have been obtained for the aligned and the misaligned matrices, respectively, and the results are compared with experimental data in the literature. Following this, heat transfer between the air flow and the matrix has been considered by varying the inlet gas temperature, i.e. 500-750 K, and keeping the wall temperature of the regenerator at 300 K. In this case, the simulations have been carried out over a Reynolds number ranging from 8 to 1700 by using the misaligned matrix. The regenerator efficiency and the Nusselt number as function of Re are given. A correlation equation for Nusselt number is given and compared with experimental results in the literature.