Wang Zhengdao, Wei Yikun, Qian Yuehong
Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai 200072, China.
State-Province Joint Engineering Lab of Fluid Transmission System Technology, Faculty of Mechanical Engineering and Automation, Zhejiang Sci-Tech University, Hangzhou 310018, China.
Entropy (Basel). 2018 May 8;20(5):351. doi: 10.3390/e20050351.
Entropy generation in thermal convection with differentially discrete heat boundary conditions at various Rayleigh numbers () are numerically investigated using the lattice Boltzmann method. We mainly focused on the effects of and discrete heat boundary conditions on entropy generation in thermal convection according to the minimal entropy generation principle. The results showed that the presence of the discrete heat source at the bottom boundary promotes the transition to a substantial convection, and the viscous entropy generation rate () generally increases in magnitude at the central region of the channel with increasing . Total entropy generation rate () and thermal entropy generation rate () are larger in magnitude in the region with the largest temperature gradient in the channel. Our results also indicated that the thermal entropy generation, viscous entropy generation, and total entropy generation increase exponentially with the increase of Rayleigh number. It is noted that lower percentage of single heat source area in the bottom boundary increases the intensities of viscous entropy generation, thermal entropy generation and total entropy generation. Comparing with the classical homogeneous thermal convection, the thermal entropy generation, viscous entropy generation, and total entropy generation are improved by the presence of discrete heat sources at the bottom boundary.
采用格子玻尔兹曼方法对不同瑞利数（）下具有差分离散热边界条件的热对流中的熵产生进行了数值研究。根据最小熵产生原理，我们主要关注瑞利数和离散热边界条件对热对流中熵产生的影响。结果表明，底部边界处离散热源的存在促进了向充分对流的转变，并且随着瑞利数的增加，通道中心区域的粘性熵产生率（）通常在数值上增大。在通道中温度梯度最大的区域，总熵产生率（）和热熵产生率（）在数值上更大。我们的结果还表明，热熵产生、粘性熵产生和总熵产生随着瑞利数的增加呈指数增长。值得注意的是，底部边界中单个热源面积的较低百分比会增加粘性熵产生、热熵产生和总熵产生的强度。与经典的均匀热对流相比，底部边界处离散热源的存在提高了热熵产生、粘性熵产生和总熵产生。
