An analysis of thermodynamic irreversible principle (TPI), through determination of entropy generation rate, during double-diffusive convection in an octagonal shape, filled with saturated fluid in a porous enclosure, is numerically investigated in this work, by studying the influence of thermodiffusion effect on entropy generation variations. According to the fluid flow evolution under consideration, the influence of mass flux due to temperature gradient is incorporated into the governing equations of the problem, which are solved numerically, using the COMSOL software. Appropriated thermal and solutal Dirichlet boundary conditions are used under the Boussinesq approximation. For the porous medium, the Darcy–Brinkman model is assumed in coupling with energy and mass transfer balance equations. The flow model is described in terms of mass flux due to temperature gradient, buoyancy ratio, thermal Rayleigh number and porosity of the medium. Results of the variations of heat transfer and entropy generation in the studied enclosure are graphically illustrated and are basically discussed, through various physical aspects of the problem. The numerical computations are presented for various values of thermal Rayleigh number (Ra_T), thermal diffusion parameter (Kt), Darcy number (Da), buoyancy ratio (N) and porosity of the medium (ε). In addition, the total entropy generation due to thermal, species and mixed diffusion gradients; Darcy–Brinkman dissipation; and fluid friction are studied and discussed. It is found that the entropy generation increases strongly when passing from the cooperative case of buoyancy forces to the opposite case. A similar behaviour is obtained with increasing the thermal diffusion ratio, at a constant buoyancy ratio. Also, an accentuated increase in entropy generation is observed when the Darcy number exceeds the value 10⁻⁶. Moreover, the results show that the augmentation of the thermodiffusion effect induces an increase in total entropy generation, at fixed value of the porosity.

在这项工作中，通过研究热扩散效应的影响，通过数值研究确定了八角形双扩散对流过程中的热力学不可逆原理（TPI），该对流形式为八角形，充满了饱和流体。关于熵产生的变化。根据所考虑的流体流动演变，将温度梯度引起的质量通量的影响纳入问题的控制方程，并使用COMSOL软件对其进行数值求解。在Boussinesq近似下使用适当的热和稀释Dirichlet边界条件。对于多孔介质，假定Darcy-Brinkman模型与能量和质量传递平衡方程式耦合。用由于温度梯度，浮力比，热瑞利数和介质孔隙率引起的质量通量来描述流动模型。通过问题的各种物理方面，以图形方式说明并基本讨论了所研究外壳中传热和熵产生变化的结果。针对各种热瑞利数（Ra_T），热扩散参数（Kt），达西数（Da），浮力比（N）和介质的孔隙率（ε）。另外，由于热，物种和混合扩散梯度而产生的总熵；达西-布林克曼耗散；研究和讨论了流体摩擦。发现当从浮力的协作情况转到相反情况时，熵产生大大增加。在恒定的浮力比下，通过增加热扩散率可以获得类似的行为。另外，当达西数超过值10 ^-6时，熵的产生也明显增加。。而且，结果表明，在孔隙率固定的情况下，热扩散作用的增强引起总熵产生的增加。