Passive heat transfer (PHT) methods provide an energy-efficient and environmentally friendly approach for transferring heat between systems, making them a promising solution for renewable and clean energy utilization across various applications. Changing the performance of heat transfer systems can be achieved by manipulating fluid flows. In this study, an investigation was conducted on the use of four blocks with different positions and sizes as obstacles embedded within a square enclosure, which affected the heat transfer through natural convection. Additionally, the study explored the effectiveness of a hybrid nanofluid created by injecting two types of nanoparticles, titanium oxide () and Multi-walled Carbon Nanotube (MWCNT), into the cooling fluid. Computational fluid dynamics (CFD) simulations were employed to examine the impact of the blocks, nanoparticle concentration, and Rayleigh number on heat transfer parameters. The findings revealed that the addition of a 6 % volume fraction of titanium oxide and MWCNT to the base fluid resulted in a notable increase of over 5 % but less than 30 % in the average Nusselt number. In contrast to expectations, embedding obstacles drooped off average Nusselt number by 9 to 30 % in Rayleigh numbers of 10,000 and 100,000, and had no effect in Rayleigh numbers of 100 and 1000.

中文翻译：

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使用多壁碳纳米管和氧化钛作为清洁和可再生能源应用的被动传热方法的助推器

被动传热（PHT）方法提供了一种在系统之间传递热量的节能且环保的方法，使其成为跨各种应用的可再生和清洁能源利用的有前途的解决方案。改变传热系统的性能可以通过操纵流体流动来实现。在这项研究中，对使用四个不同位置和大小的块作为嵌入方形外壳内的障碍物进行了调查，这会影响自然对流的传热。此外，该研究还探讨了通过将两种类型的纳米粒子（氧化钛 () 和多壁碳纳米管 (MWCNT)）注入冷却液中而产生的混合纳米流体的有效性。采用计算流体动力学 (CFD) 模拟来检查块、纳米颗粒浓度和瑞利数对传热参数的影响。结果表明，在基液中添加体积分数为 6% 的氧化钛和多壁碳纳米管，平均努塞尔数显着增加超过 5%，但不到 30%。与预期相反，在瑞利数为 10,000 和 100,000 时，嵌入障碍物使平均努塞尔数下降 9% 至 30%，而在瑞利数为 100 和 1000 时则没有影响。