دانلود مقاله همرفت فتوترمال نانوسیال مغناطیسی در کلکتور خورشیدی جذب مستقیم
نکات برجسته
چکیده
چکیده گرافیکی
کلید واژه ها
1. مقدمه
2. روش شناسی
2.1. نانو سیال
2.2. سیستم آزمایشی
2.3. مدل ریاضی
3. نتایج و بحث
3.1. اختلاف دما
3.2. سرعت جریان
3.3. آنالیز حرارتی
3.4. راندمان حرارتی
4. نتیجه گیری
منابع
Highlights
Abstract
Graphical abstract
Keywords
1. Introduction
2. Methodology
2.1. Nanofluid
2.2. Experimental system
2.3. Mathematical model
3. Results and discussion
3.1. Temperature difference
3.2. Flow velocity
3.3. Thermal analysis
3.4. Thermal efficiency
4. Conclusions
Declaration of Competing Interest
Acknowledgements
References
چکیده
جذب مستقیم حرارت خورشیدی مبتنی بر نانوسیال منجر به بازده حرارتی برتر از فناوری حرارتی خورشیدی معمولی می‌شود. علاوه بر این، همرفت نانوسیال می‌تواند بدون پمپ در کلکتور حفظ شود. در این مقاله، ما یک نانوسیال مغناطیسی آبی را مطالعه می‌کنیم که قادر به برقراری همرفت فتوترمال در یک کلکتور خورشیدی جذب مستقیم در مقیاس آزمایشگاهی مجهز به یک سلونوئید است. نانوسیال شامل ذرات 60 نانومتری Fe2O3 است که در آب مقطر با غلظتی در محدوده 0.5٪ وزنی تا 2.0٪ وزنی پراکنده شده اند. یک مدل تجربی از همرفت فتوترمال بر اساس آزمایش‌ها توسعه داده شد. این مدل نیروهای مغناطیسی و ترموفورتیکی را که در نانوسیال عمل می‌کنند، در نظر می‌گیرد. نانوسیال تا 2.0 درصد وزنی. نانوذرات اکسید آهن تحت میدان مغناطیسی تا 28 میلی‌تانس سرعتی برابر با 5 میلی‌متر بر ثانیه دارند. این منجر به حداکثر بازده حرارتی کلکتور برابر با 65٪ شد.
توجه! این متن ترجمه ماشینی بوده و توسط مترجمین ای ترجمه، ترجمه نشده است.
Abstract
Nanofluid-based direct absorption of solar heat results in thermal efficiencies superior to conventional solar thermal technology. In addition, convection of nanofluid can be sustained pump-free in the collector. In this article, we study an aqueous magnetic nanofluid capable to establish the photothermal convection in a labscale direct absorption solar collector equipped with a solenoid. The nanofluid consisted of 60-nm Fe2O3 particles dispersed in distilled water at concentration in the range 0.5% wt.-2.0% wt. An empirical model of the photothermal convection was developed based on the experiments. The model accounted for magnetic and thermophoretic forces acting within the nanofluid. The nanofluid with up to 2.0% wt. iron oxide nanoparticles obtained the velocity of ∼5 mm/s under the magnetic field of up to 28 mT. This resulted in the maximum thermal efficiency of the collector equal to 65%.
Introduction
Nanofluids were developed by Choi and Eastman (1995) to increase the thermal conductivity of the existing heat transfer fluids and then to boost the coefficient of heat transfer during forced convection. However, the use of nanofluids for forced convection has inherent drawbacks (Rudyak and Minakov, 2018). The presence of nanoparticles increases the apparent viscosity of the nanofluids so that the pumping cost grows. Another issue connected to the use of the concentrated nanofluids is their possible nanotoxicity (Bostan et al., 2016) and erosion. These limitations hinder the replacement of the conventional heat transfer fluids by nanofluids. Although Hydromx (2021) reports various applications of their commercial nanofluids for domestic hot water and data centres, the scientific community considers the industrial use of the nanofluids as limited due to the discussed challenges.
Conclusions
In this paper, we investigated the process of photothermal convection in a labscale direct absorption solar collector with magnetic nanofluid. The collector was mounted in a closed loop, which was cooled on the opposite side of the circuit. The continuous flow of the nanofluid was established under the simultaneous influence of the external source of radiative heat and the solenoid mounted on the tubes. The experiments revealed that the temperature drop between the cold and warm parts of the collector could rise to 14 K at the magnetic field of 28 mT and the nanoparticle concentration of 0.5% wt. According to our theoretical estimates, the maximum flow velocity for the established pump-free magnetic convection was 5.1 mm/s at 28 mT and the concentration of 2.0% wt. The thermal efficiency of the collector was in the interval 8%–65% for the entire range of considered concentrations and solenoid currents. The maximum efficiency is comparable to the thermal efficiency of a commercial vacuum-tube collector operating in Northern climate conditions (Popsueva et al., 2021). Although the developed process finds promising applications in solar thermal technology, the current design requires good optimisation. Additional efforts are needed to reduce the consumed electrical power and, at the same time, limit the number of used nanoparticles as the concentrated nanofluids reduce the thermal efficiency of DASC and increase the pumping costs. An opportunity to boost the natural convection in a DASC establishing the supplementary photothermal convection should be considered in the future.