Porous media structures have been proposed as an interesting solution on the design of high-temperature volumetric heat exchangers and sensible thermal energy storage devices. The wide exchange area between the solid matrix and the fluid offers the possibility to reach higher conversion efficiencies, particularly on applications of high-temperature (∼1000°C) gases. Nevertheless, the presence of the solid matrix increases the hydrodynamic resistance on the flow, and consequently, generates irreversibilities. The entropy generation can assess in the same figure of merit the different irreversibilities generation mechanisms. In this context, this work presents a physical and mathematical model to determine the local entropy generation (LEG) rate and recognizes its different generation mechanisms for porous media. The proposed model defines a useful expression to determine the LEG as a post-process variable from the usual CFD scalar and vectorial results (temperature, velocity, TKE, and $ϵ$), without the necessity of solving an additional entropy transport equation. A numerical experiment was implemented showing inflection points where the porous hydrodynamic resistance forces exceed the heat transfer in the LEG rate. The Forchheimer hydrodynamic resistance effect can domine the LEG in comparison to the volumetric heat transfer for high porous Reynolds regimes ($\text{R}{\text{e}}_D$>100) when the porosity is under 0.6.

多孔介质结构已被提议作为高温容积式换热器和显热储能装置设计的有趣解决方案。固体基质和流体之间的广泛交换区域提供了达到更高转换效率的可能性，特别是在高温（~1000°C）气体的应用中。然而，固体基质的存在增加了流动的流体动力阻力，因此产生了不可逆性。熵生成可以在相同的品质因数中评估不同的不可逆性生成机制。在这种情况下，这项工作提出了一个物理和数学模型来确定局部熵生成 (LEG) 率，并识别其不同的多孔介质生成机制。$\epsilon$)，无需求解额外的熵传输方程。实施了一个数值实验，显示了多孔流体动力阻力超过 LEG 速率中的热传递的拐点。与高孔雷诺体系的体积传热相比，Forchheimer 流体动力阻力效应可以支配 LEG（$\text{R}{\text{e}}_D$>100) 当孔隙率低于 0.6 时。