چكيده به لاتين
This study addresses the challenge of energy dissipation as heat in various devices, with a focus on thermoelectric generators (TEGs) as a means to convert this waste heat into electrical energy. The efficiency and reliability of TEGs are often constrained by the properties of the working fluid, with water being a common but suboptimal choice due to its low thermal conductivity. The objective of this research is to conduct a numerical investigation into the effects of nanofluids on the thermal performance of a thermosiphon system integrated with a TEG. The study explores the potential of nanofluids to mitigate the limitations associated with traditional working fluids. The research begins by focusing on heat sink geometry, specifically investigating fin height and spacing. The simulations reveal that fin spacing has a significant impact on performance. As spacing increases from 2.5 mm to 5.5 mm, the number of fins drops dramatically from 17 to 5, a 70% reduction in fin count. Despite this wider spacing increasing the heat transfer coefficient, it leads to higher heat sink temperatures. This counterintuitive result is due to the substantial loss in wetted surface area, which more than offsets any gains in convective heat transfer. The study concludes that, within the tested range, the smallest fin spacing of 2.5 mm is optimal. For fin height, the study identifies an optimal range between 5-25 mm. interestingly, increasing fin height leads to lower heat sink temperatures despite causing a decrease in the convective heat transfer coefficient. This is because the substantial increase in wetted surface area as fins grow taller more than compensates for the local decrease in heat transfer efficiency. These findings underscore that in passive, low-flow systems, surface area often trumps convective coefficients, a crucial insight for future designs. The research then moves on to investigate the impact of nanofluids on cooling performance. Both Al₂O₃-water and CuO-water nanofluids significantly enhance heat transfer compared to pure water. At a heat flux of 120 W, the Al₂O₃-water nanofluid at 4% concentration reduces the heat sink temperature from 75°C to about 62°C, a substantial 17% reduction. CuO-water at the same concentration yields a 13% decrease. Moreover, increasing Al₂O₃-water nanoparticle concentration from 1% to 4% provides an additional temperature drop of about 8°C, demonstrating that higher concentrations further enhance performance. The study culminates in a high-stakes test, subjecting the TEG system to a scorching 75,000 W/m² heat flux. Using the optimized heat sink design (15 mm fins height, 2.5 mm fin spacing) cooled by nanofluid, the system effectively maintains the cold side at a mere 39°C. This achievement is a testament to the design's effectiveness, showcasing how geometric optimization and advanced materials can synergize to deliver outstanding performance. Finally, the temperature and voltage contours from the simulations provide visual evidence of the cooling system's impact. The temperature gradients illustrate the stark contrast between the hot and cold sides, while the voltage contours (ranging from 1.07 to 11.07 mV) underscore how this temperature difference translates into electrical potential. These visuals confirm that the optimized passive cooling system, enhanced by nanofluids, can maintain the critical temperature gradient needed for substantial TEG power generation, even under extreme heat flux conditions
