تعیین بازده انرژی و اگزرژی کلکتور خورشیدی صفحۀ تخت عمل‌کننده تحت جریان آشفتۀ نانوسیال با نانوذرات دی‌سولفید مولیبدن در موفولوژی‌های مختلف برای مناطق گرمسیری ایران

در این مطالعه به بررسی آنالیز انرژی و اگزرژی یک کلکتور خورشیدی صفحه‌تخت که در جزیرۀ ابوموسی (خلیج فارس) در استان هرمزگان (منطقۀ گرمسیری) قرار گرفته است، پرداخته می‌شود. هدف از انجام این مطالعه بررسی اثر شکل نانوذرات دی‌سولفید مولیبدن (mos2) برای چهار شکل مختلف از نانوذرات (تیغه‌ای، صفحه‌ای، آجری و استوانه‌ای) بر انتقال حرارت و تولید آنتروپی است. نتایج خروجی شامل عدد ناسلت متوسط، دمای سیال خروجی، افت فشار، ضریب اصطکاک، ضریب عملکرد هیدرولیکی حرارتی (pec) و تولید آنتروپی برای شکل‌های مختلف نانوذرات و کسر حجمی صفر تا 4% از نانوذرات در جریان آشفته با دبی‌های جرمی 0.5 و 0.75 کیلوگرم بر ثانیه ارائه شده است. بر اساس نتایج به‌دست‌آمده و با توجه به معیار ارزیابی علمکرد هیدرولیکی حرارتی، بهترین حالت در دبی جرمی 0.5 کیلوگرم بر ثانیه مربوط به نانوذرۀ آجری، در کسر حجمی 3% می‌باشد که مقدار آن 1.269 است؛ درحالی‌که در دبی جرمی 0.75 کیلوگرم بر ثانیه بهترین حالت مربوط به نانوذرات آجری، در کسرحجمی 4% است و مقدار آن 1.182 می‌باشد. همچنین برای جریان با دبی جرمی 0.5 کیلوگرم بر ثانیه افزودن نانوذرۀ آجری و تیغه‌ای به سیال پایه از نظر بهبود بازده اگزرژی اثری ندارد. این در حالی است که برای جریان با دبی جرمی 0.75 کیلوگرم بر ثانیه استفاده از کسر حجمی 1 تا 4% از نانوذرات آجری و تیغه‌ای می‌توانند سرعت تولید آنتروپی را به‌اندازۀ 8% در مقایسه با سیال پایه کاهش دهند.

Determination of Energy Efficiency and Exergy of Solar Collector Bed, Operating Plate under Turbulent Nanoscale Flow with Molybdenum Disulfide Nanoparticles in Different Morphologies for Tropical Regions of Iran

Extended AbstractIntroduction:Due to development in engineering and in industrial processes as well as the rise of environmental and energy concerns, heat exchanger systems must be improved to transfer heat more efficiently. Different technologies are used to enhance the efficiency of the heat exchanger systems. For the higher thermal conductivity of solid particles, solid particles in conventional fluids is applied to enhance the heat transfer performance of these fluids. It has been about two decades that the term of Nanofluid has been introduced to scientific society. In fact, high thermal conductivities of solid nanoparticles in nanofluids effectively increase the suspensions. The literature review elucidates that the effects of Molybdenum Disulfide (MoS2) nanoparticle shape on thermal hydraulic performances and entropy generation in sheet and tube solar collectors have not been yet investigated, despite the fact that the effect of some nanoparticles ( gamma;‒AlOOH and SiO2), different shapes on heat transfer, thermal‒hydraulic and entropy generation in heat sink solar collectors and common heat exchangers have been assessed, Hence, for the first time in this study, the effects of using nanofluid on the heat transfer and entropy generation along with the effects of MoS2 nanoparticle shape, a solar absorber located in Abu‒Musa Island as one of the best solar irradiation receiver cities in Iran, are evaluated.2. Material and Methods:The schematic diagram of studied sheet and tube collector is shown in Fig. 1. Figure (1): Schematic diagram of simulated sheet and tube collectorThe system of governing equations for fluid flow and heat transfer in the flat‒plate sheet and tube solar collector can be written in the Cartesian tensor system.Discussion and Results: Fig. 2 shows the variations of Nusselt number for different nanoparticle shapes for model with ṁ=0.50 kg/s. It is seen that for different shapes the trend of changes in Nusselt number is similar with each other and is increasing. However, the brick shape in high volume fractions Nusselt number decreases. It is perceived that Nusselt number of nanofluid with brick shape in volume fraction of 3% is on average 28% higher than water. Outlet temperature increases because the heat capacity of nanofluids decreases. (a)(b) (c)(d)Figure (2): Variations of (a) Nusselt number, (b) outlet fluid temperature, (c) pressure drop, and (d) friction factor, for different shapes of nanoparticles for model with ṁ=0.50 kg/sConclusion: The effects of different shapes of molybdenum disulfide nanoparticles suspended in water on the performance of a sheet and tube based solar collector located in Persian Gulf have been examined. The findings are summarized as follows:Nusselt number increases with an increase in volume fraction of nanoparticles. This change is higher for brick shaped particles.The outlet temperature increases with an increase in volume fraction of nanoparticles. This increase is higher for brick shaped particles and is lower for platelet shaped particles.For both mass flow rates in the nanofluids with platelet and brick nanoparticle shapes, the pressure drop is the highest and the lowest value between all models respectively. Consequently, the value of friction factor for nanofluid with brick nanoparticle shapes is the lowest compared to the other models.The PEC of solar collector using MoS2/water nanofluid with ϕ=3% volume fraction and brick nanoparticle shape in mass flow rate of 0.5 kg/s is found to be the best among all the models, and its value is around 1.269. However, in mass flow rate of 0.75 kg/s this value for nanofluid with ϕ=4% volume fraction and brick shape nanoparticle is found to be the best among all the models and is about 1.182.With an increase in the volume fraction of particles, the entropy generation rate due to heat transfer reduces for all shapes of nanoparticles, although this reduction is insignificant.The trends of total entropy generation and entropy generation due to fluid friction were found to be similar for all nanoparticle shapes.