Nanofluids In Solar Collectors Research Articles

Assessment of thermohydraulic performance and entropy generation in an evacuated tube solar collector employing pure water and nanofluids as working fluids

This study conducts a numerical comparison of the thermal performance of three distinct working fluids (pure water, TiO2, and SiO2 water-based nanofluids) within an evacuated tube solar collector using Computational Fluid Dynamics. The study evaluates thermohydraulic performance alongside global and local entropy generation rates, while considering variations in solar radiation values and inlet mass flow rates. Results indicate that nanofluids demonstrate superior performance under low solar radiation, exhibiting higher outlet temperatures, velocities, thermal efficiency, and exergy efficiency compared to pure water. However, at the higher solar radiation level, the efficiency of SiO2 water-based nanofluid diminishes due to its impact on specific heat. Furthermore, the entropy generation analysis reveals significant reductions with TiO2 water-based nanofluid in all the phenomena considered (up to 79 %). The SiO2 nanofluid performance aligns closely with pure water under high radiation value. This investigation offers valuable insights into the utilization of nanofluids in solar collectors across diverse operating conditions, emphasizing their pivotal role in enhancing overall performance.

Performance enhancement by tungsten trioxide and silicon dioxide mixed nanofluids in solar collector of evacuated tube type

This study compares the effectiveness of evacuated tube solar collectors with nanofluids. Three different combinations of two nanoparticles were examined at the present investigation. Here, silicon dioxide and tungsten trioxide nanoparticles having diameters of 80 and 90 nm, respectively, have been employed in the preparation of nanofluids. There are different concentrations of nanoparticles in volume fractions of 0.01%, 0.015%, 0.02%, 0.025%, and 0.03% at different mass flow rates, such as 20 g/s, 40 g/s, and 60 g/s, employed in this study. The observations like variations in temperature, heat absorption, efficiency, density, specific heat, and thermal conductivity measurements have been determined. Better qualities are found in nanofluid with a volume fraction of 0.030%. The 0.030% volume fraction of Nanofluid at 60 g/s of the mass flow rate provided 4053.49 W of heat gain and 72.69% of efficiency, which is higher than other Cases; therefore, this is a recommendation for obtaining greater performance.

Effect of symmetrical and asymmetrical structures of transverse tube on heat transfer performance of nanofluids in a solar collector system

AbstractIn an effort to enhance the heat transfer performance of solar collectors, this paper proposed to replace the smooth tube with symmetrical and asymmetrical transversely corrugated tubes, and to couple with SiO2‐H2O nanofluids for heat transfer of solar collectors. Effects of nanofluids mass fraction (w = .0%, .1%, .3%, and .5%), Reynolds number (3000, 4000, 5000, 6000, and 7000), and groove radius (1.5, 2, and 2.5 mm) on the flow and heat transfer properties of nanofluids in solar collectors were studied. The comprehensive evaluation index was used to consider the heat transfer property and flow resistance of fluid flow at the same time. Results showed that with the augment of nanofluids mass fraction, Reynolds number, and groove radius, the heat transfer enhancement performance of the collector becomes better. Among them, when the Reynolds number is 4000, the asymmetric transversely corrugated tube with a nanofluids mass fraction of .5% and a groove depth of 2.5 mm has the best comprehensive flow and heat transfer performance, and the comprehensive evaluation index can reach 1.62. The study results in this paper are beneficial to the coupling of nanofluids and transversely corrugated tubes and their application in the domain of enhanced heat transfer of solar collectors.

Hydroxyl functionalized MWCNT nanofluids with excellent photothermal conversion performance in direct absorption solar collectors

Developing novel nanofluids with good stability, excellent photothermal conversion performance, and appropriate thermophysical properties is of great importance in promoting the practical utilization of nanofluids in solar collectors. In this work, hydroxyl multi-walled carbon nanotube (MWCNT-OH) nanofluids are proposed, which can achieve a high photothermal conversion of 88.2 % at a concentration of 20 ppm under 1-sun irradiation. Both the sedimentation experiment and spectrophotometer analysis prove that the prepared MWCNT-OH nanofluids have excellent stability. The influence of hydroxyl functionalization, MWCNT-OH concentrations, and temperature on the thermophysical and optical properties is analyzed. Moreover, the comparison between MWCNT-based nanofluids with different functionalization reported in the literature and our work is carried out, the results show that MWCNT-OH nanofluids in our work outperform MWCNT-based nanofluids with other types of functionalization reported in the literature. This work may promote the use of MWCNT-OH nanofluids as working fluids in solar collectors.

Recent Trends in Applications of Nanofluids for Effective Utilization of Solar Energy

:Renewable-energy sources have been explored recently by scientists to fulfill the global energy demand. According to the International Energy Agency (IEA), by 2040, wind and solar power will be the star performers for energy conservation. The annual potential energy received from the sun ranges from 1,575 to 49,800 exajoules (EJ). However, this energy is not being utilized to its potential. Recently, researchers have proven that nanofluids can be used as a working fluid replacing the conventional working fluid for solar collectors and other heat exchange operations. The selection of the nanofluid is not only based on the size and shape of nanoparticles but the pH value and stability of nanofluids are also important parameters.:This review paper is mainly focused on the recent trends in nanofluids applications for the capture, conservation, and utilization of solar energy. The present paper reviews the detailed analysis of various forces affecting the nanofluid system and also highlights the important aspects to reduce the frictional energy losses, exergy destruction, entropy generation, effect of the flow properties, and thermo-physical properties of the nanofluids, and other reasons for wastage of the exergy. This study also compares the performance of the direct absorption solar panel, flat plate solar panel, parabolic solar collector, photovoltaic thermal solar collector, linear Fresnel solar collector, solar dish, and evacuated type solar collector.:Among these solar collectors, direct absorption solar collectors, flat plate solar collectors, photovoltaic solar collectors, and evacuated type solar collectors are more commonly used solar collectors; thus, the exergy and energy analyses of these collectors are important for their design and application. Stability issues and agglomeration problems are still some major concerns involved in the application of nanofluids. However, the use of nanofluid increases the performance of the solar collector compared to the base fluid as a working fluid. This paper also highlights the recent trends in the application of nanofluids in solar collectors.

A review of applications of plasmonic and conventional nanofluids in solar heat collection

• The research progress of plasmonic nanofluids in recent ten years is reviewed. • Comparison of plasmonic nanofluids with conventional nanofluids. • The LSPR effect of plasmonic nanofluids enhances the light absorption. • Many factors affect the light absorption and photothermal conversion characteristics. • How to improve the light absorption properties of plasmonic nanofluids needs further discussion. With the development of solar energy utilization and nanotechnology, nanofluid heat collection has attracted significant attention. The solar plasmonic nanofluids with significant local surface plasmon resonance (LSPR) effect have exhibited superior behaviors in thermophysical properties, optical properties, and photothermal conversion efficiency. This paper reviews the research progress of plasmonic nanofluids in solar collectors and PV/T systems and compares them with conventional nanofluids for the first time. The plasmonic nanofluids exhibit excellent light absorption capacity and controllable light intensity and resonance frequency. Due to the existence of the LSPR effect, plasmonic nanofluids show significant absorption peak, which can meet the requirements of broadband solar energy absorption and have better usage value than conventional nanofluids in solar heat collection. Many factors affect the photothermal conversion efficiency of plasmonic nanofluids, such as particle size, concentration and flow rate. Using hybrid nanofluids can significantly broaden the extinction spectrum and further enhance light absorption. To clarify the specific mechanism of plasmonic nanofluids, improve their stability and make them more suitable for different types of solar heat collection, more experimental exploration is needed.

4E study of experimental thermal performance enhancement of flat plate solar collectors using MWCNT, Al2O3, and hybrid MWCNT/ Al2O3 nanofluids

Nanofluid is a cutting-edge heat transfer fluid with the potential to significantly improve the heat transfer performance of conventional fluids. The most valued aspects to increase the overall solar collector's effectiveness are to improve design factors and the convection heat transfer coefficient between the absorber tubes and fluid. Water nanofluids including MWCNTs, Al2O3, TiO2, SiO2, and CuO are the most often utilized nanofluids in solar collectors. In this paper, the Flat Plate Solar collector thermal efficiency was experimentally investigated for MWCNT, Al2O3, and hybrid MWCNT/Al2O3 50:50% as a working fluid, under controlled circumstances. The effects of several parameters, including solar radiation intensity, volume proportion of nanoparticles, and volumetric flow rate on the efficiency, are investigated. Four volume concentration percentages were studied for each type of nanofluid (0.5%, 0.025%, 0.01% and 0.005%) with three different mass flow rates for each concentration. The results show that using hybrid MWCNT/Al2O3 (50:50%) offers an increase in efficiency by 26%, 29%, and 18% for 1.5 L/m, 2.5 L/m, and 3.3 L/m, respectively, recommending the replacement of 50% of the MWCNTs by the more economic and environmentally friendly Al2O3.

Recent advancement of nanofluids in solar concentrating collectors: A brief review

Employing nanofluids as a working fluid is very interesting idea which is preferably a mixture of a base liquid with a certain volume fraction of nanoparticles of nanometre size. This brief review has an objective to check the performance of solar collectors by applying nanofluid as an operating fluid. In past two decades, the solar energy has been proven very useful for thermal energy systems (TES) in various experimental applications. Nanofluids are the fluid which has demonstrated numerous improvements in the thermophysical properties over the past decade. The nano fluids have a big ability to improve the rheologic characteristics of the primary base fluid used. Nanofluids are the deferment of essentially the fluids such as water, ethanol, etc. in nanoparticles like alumina (Al2O3), Copper Oxide (CuO), Titanium oxide (TiO2) of size micro or millimetre and reveals distinguishing characteristics in comparison to conventional liquids applied. Since nanofluids have improved rheological properties, these are applied to boost the implementation of traditional solar arrangements. The stated study offers the comprehensive analysis of the solar collectors, presentation of nanofluids in solar collector and their growth in rheological characteristics.

Thermal properties, flow and comparison between Cu and Ag nanoparticles suspended in sodium alginate as Sutterby nanofluids in solar collector

Solar energy's unrestricted accessibility aids in environmental sustainability and renewable technology. Parabolic trough solar collector (PTSC) is a well-established, low-cost talent that is utilized in a variety of solar technical applications. Current research focuses on thermic radiation, slippage velocity, sucking (injection), and convective boundary constraint to improve the heat transmission of PTSC in the existence of magnetic force. Entropy analysis is probed in a penetrable material of Sutterby nanofluid (SNF) flow past an exponentially extending horizontal plate that features PTSC. The study looks at two types of nanofluids: copper-sodium alginate (Cu-SA) and silver-sodium alginate (Ag-SA). To transform partial differential equations (PDEs) to nonlinear ordinary differential equations (ODEs) with associated boundary constraints, enough similarity variables are used. To get an approximate solution to reduced ODEs, an efficient Keller-box approach is used. The results are visually represented and analyzed in terms of physical factors. According to major discoveries, raising the Brinkmann and Reynolds numbers increases the total system entropy. The Sutterby nanofluid parameter improves the heat rate of the Parabolic Trough Solar Collector. When the parameters are changed, the thermal efficiency of Cu-SA increases by 1.7% at the least and 4.8% at the most.

A review of the use of nanofluids as heat-transfer fluids in parabolic-trough collectors

Due to their enhanced thermophysical properties, nanofluids have great potential for improving heat-transfer efficiency. Nanofluids are employed in various thermal applications in the automotive industry, heat exchangers, solar power generation and more. Among the applications of this technology, its use to enhance the heat transfer of solar collectors appears promising. It is therefore not a surprise that the use of nanofluids in solar collectors has become a popular research area. Still, there are important obstacles with the use of nanofluids in solar collectors. Stability is the most evident, in addition to environmental aspects and the need to design suitable large-scale production processes for the application of nanofluids at the required scale for large solar collectors’ fields. In this literature review, we study nanofluids in solar collectors, and parabolic-trough collectors in particular, at temperatures between 100 °C and 300 °C. We present recent advances and research on nanofluids and consider the progress in understanding stability mechanisms, characterization and preparation methods, as well as their thermophysical properties. We describe the main research gaps and suggest areas of further research.

Experimental Investigation on Solar–Thermal Conversion and Migration Characteristics of Nanofluids

Solar–thermal conversion and migration characteristics of nanofluids have attracted intensive attention recently. Due to the strong absorption of solar energy, solar collectors with nanofluids have wide applications in many areas including desalination and power generation. Researchers have mainly focused on the macroscopic performance of nanofluids in solar collectors, but the nanoparticles’ migration characteristics with vapor during phase transformation have not been further investigated. Therefore, an experimental investigation on solar–thermal conversion characteristics of nanofluids and migration characteristics with vapor during phase transformation was conducted in this work, in order to verify the enhancement effect of nanoparticles on solar energy absorption and explore the nanoparticles’ migration behavior with vapor. It was found that part of Ag nanoparticles migrate out of the nanofluids with generated vapor by boiling nanofluids, and most of the nanoparticles remained in the nanofluids. In addition, more Ag nanoparticles migrated with vapor with the increased heating power. The concentration of migrated nanofluids was 20.58 ppm with a power of 16.2 W and 31.39 ppm with a power of 20 W. The investigation pointed out the potential danger of nanofluids in the process of utility and provided a reference for the standardized application of nanofluids.

Thermal Conductivity and Rheology of Graphene Oxide Nanofluids and a Modified Predication Model

In order to reveal the heat transfer performance of nanofluids in solar collectors, the thermal conductivity and dynamic viscosity of five kinds of graphene oxide nanofluids, with a mass fraction of 0.002% to 0.01%, were studied in the temperature range of 25–50 °C. To ensure the dispersion and stability of the prepared nanofluids, UV–Vis absorption spectrum, zeta potential and particle size distribution were employed for nanofluid characterization. Agglomeration and sedimentation of the prepared nanofluids after standing for 20 days were observed, showing the good stability of the prepared graphene oxide–water nanofluid. The dynamic viscosity and thermal conductivity were measured. They show that with the increase in temperature, the dynamic viscosity of nanofluids decreases and the thermal conductivity increases. With the increase in mass concentration, the viscosity and thermal conductivity are improved. The highest thermal conductivity increase is obtained when the nanofluid concentration is 0.01% and the temperature is 50 °C. Finally, and most importantly, considering the inaccuracy of the existing experimental correlations to the predicted values of thermal conductivity, we propose our new mathematical model of correlation and carry out a series of tests to verify its reliability. The experimental correlations with temperature and concentration as independent variables show good agreement and accuracy with the experimental data.

A review on performance of nanofluids in various heat pipe solar collector

Energy from the Sun brings as Solar energy which is abundantly available and utilized for various applications. Owing to the increase in energy demand, having a limit of non-renewable energy sources, more interest is given to Solar energy. One of the most fundamental applications of using Solar energy is a Solar collector. The efficiency of the Solar collector depends upon the fluids used in the Solar collector and thermal performance also can be enhanced by using heat pipes in the Solar collector. Compared to flat plate solar collectors, the major disadvantage of heat loss can be rectified in heat pipe solar collectors. Still, to improve the performance of heat pipe solar collectors, nanofluids can be used instead of base fluids to improve thermal performance. In this review paper, the application of nanofluid in Solar collectors results in the percentage of improvement in heat transfer by nanofluid at optimum condition is discussed. This paper reviewed widely the recent development and upcoming research that can be done to enhance the working of heat pipe Solar collectors using nanofluids.

Güneş Kolektörlerinde Nanoakışkanların Kullanılmasının Etkileri

The importance of using solar energy, one of the renewable energy sources, has started to be understood more recently. The negative environmental effects and limited amounts of fossil fuels have led to increased demand for renewable energy sources worldwide and the production of various models and devices has accelerated to take advantage of solar energy, which is the basis of all energy sources. Using solar collectors as a way to benefit from solar energy has been used for many years. Although solar collectors are generally divided into 4 types as flat plate (FPSC), evacuated tube (ETSC), parabolic (PSC) and heat pipe (HPSC), these types can also be divided into separate types with many different features. The most commonly used solar collector type in the world is Flat Plate Solar Collector. The most important reasons for this are being cheap, easily produced and applied in various ways. Yet, the thermal productivity of FPSCs decreases below 40% in non-ideal climate conditions with low surrounding temperature. The existence of such disadvantages of FPSCs led to the production of Evacuated Tube Solar Collectors. With the advancing technology, the utilization of heat pipes in collectors has come to the agenda and as a result of the studies conducted, it has been determined that the use of heat pipe improves efficiency. In addition, the use of nanofluids in solar collectors and heat pipes has become quite common, and many studies have been carried out especially on this subject recently. The primary objective is always to improve the performance of the system and achieve efficiency. In this way, solar energy will be used in the most effective way and world energy supply demand will be met by using renewable resources.

Long-Term Performances and Technoeconomic and Environmental Assessment of Al2O3/Water and MWCNT/Oil Nanofluids in Three Solar Collector Technologies

Bringing together nanofluids and solar collectors has been widely discussed without any major advance or long-term study being carried out. In this context, this paper provides a useful feasibility study to help future decisions in using nanofluids in Solar Water Heating Systems (SWHSs) in different locations. The performances of SWHSs using the nanofluid-based flat plate solar collector (FPSC), evacuated tube collector (ETC), and compound parabolic collector (CPC) under the Mediterranean, arctic, and desert climate conditions are presented and discussed. The analysis is carried out using a transient-based numerical approach, solving energy balance equations for different systems. Various performance factors such as energy saving, solar fractions, and environmental impacts of auxiliary energy supplies are evaluated to feasibly assess the use of nanofluids in such devices. Simulation results demonstrate that the use of nanofluids increases the solar heater performance which reduces considerably the payback period ( P P ) of the investment in solar heating systems up to 3.34 years in Tunisian climate. Under Quebec’s climate region, the annualized solar return of the ETC system increases from 4874.65 US$ to 9785.93 US$ by adding 0.06 v% Al2O3 in water. Also, the use of nanofluids in solar collectors with electric auxiliary heaters reduces harmful CO2 emissions up to 0.49 tons/year.

A Review on the Use of Hybrid Nanofluid in a Solar Flat Plate and Parabolic Trough Collectors and Its Enhanced Collector Thermal Efficiency

Energy demand is high in all parts of the world, mostly in all industrial sectors. To meet the energy demand the fossil fuel is the only way. Due to rapid industrial growth and use of fossil fuel result in global warming and environmental pollution. Moreover, the limited availability of the fossil fuels, it is necessary to depend on the renewable energy sources. Promising renewable energy in the world is solar energy, which is available largely on the earth surface. The solar energy can be converted into thermal energy in the solar flat plate collector. The collector thermal efficiency is purely depends on the working fluid used in it. Most of the studies revealed that replacing the working fluid with high thermal conductivity fluids called as nanofluids and hybrid nanofluids can improve the collector thermal efficiency. Few decades back studies have been conducted with nanofluids in solar collectors. Currently the researchers are working on solar collectors for further improvement of its efficiency using hybrid nanofluids. In this review paper, we will discuss about the synthesis of hybrid nanoparticles, hybrid nanofluids, characterization, thermophysical properties, and application of hybrid nanofluids in solar flat plate collector under natural and forced circulation of fluid. The research gap in the solar collector is also discussed in this article. This paper also explains about the heat transfer capabilities of hybrid nanofluids especially used solar collectors.

Stability, thermophsical properties of nanofluids, and applications in solar collectors: A review

<abstract> <p>Recently, renewable energies have attracted the significant attention of scientists. Nanofluids are fluids carrying nano-sized particles dispersed in base fluids. The improved heat transfer by nanofluids has been used in several heat-transfer applications. Nanofluids' stability is very essential to keep their thermophysical properties over a long period of time after their production. Therefore, a global approach including stability and thermophysical properties is necessary to achieve the synthesis of nanofluids with exceptional thermal properties. In this context, the objective of this paper is to summarize current advances in the study of nanofluids, such as manufacturing procedures, the mechanism of stability assessment, stability enhancement procedures, thermophysical properties, and characterization of nanofluids. Also, the factors influencing thermophysical properties were studied. In conclusion, we discuss the application of nanofluids in solar collectors.</p> </abstract>

Progress and application of nanofluids in solar collectors: An overview of recent advances

Sun is the vital source of energy on the earth and it is one of the most significant options in contrast to the traditional petroleum products. It is only because of its property to directly convert solar energy into thermal energy in form of heat energy and finally into electrical energy without any harmful environmental effects such as greenhouse gas emission and other environmental effects. The effective way to enhance the performance of solar energy system is to utilize a high-quality heat transfer fluid with superior thermophysical properties such as high thermal conductivity and hence nanofluid is the best option to enhance the performance of the system. The lack of petroleum products and its harmful effect on the environment inspired the researchers to think about the alternative source of energy and sun is the best alternative source of solar energy. The main aim of this review paper is to investigate the applications of nanofluid and its recent advancement in solar collectors.

Potential Use of Nanofluids in Solar Collectors: A Review

Solar energy is clean and easily available everywhere. It is trapped by a device called a solar collector. Solar collectors are used to utilize solar energy. Generally, the performances of the solar collector are low. Nanofluid is used in solar collectors to boost up the performance of the solar collector. This paper presents a review of the literature on the role of nanofluids in various types of solar collectors. It is found that the performance of the solar collector improves by using nanofluids as a heat transfer medium.

Advances of Nanofluids in Solar Collectors - A Review of Numerical Studies

Advances of Nanofluids in Solar Collectors - A Review of Numerical Studies