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Simultaneous mapping of single bubble dynamics and heat transfer rates for SiO <sub/>2</sub> /water nanofluids under nucleate pool boiling regime
摘要： Dependence of single vapor bubble dynamics and heat transfer rates on varying concentration of SiO2 nanoparticles for a range of subcooled conditions (0–9 ?C) has been experimentally studied under nucleate pool boiling configuration. Non-invasive measurements have been carried out using rainbow schlieren deflectometry. Results on bubble dynamics showed that the bubble diameter and aspect ratio decrease with increasing subcooling levels as well as concentration of nanofluids. The frequency of bubble oscillations was found to increase first and then decrease with increasing subcooling levels while it decreases monotonically with increasing nanofluid concentration. Bubble departure frequency increased significantly for nanofluids, while it decreased with increasing subcooling levels. Condensation effects at the bubble interface were reflected in the form of redistribution of colors around it. Schlieren images clearly revealed a spread in the spatial extent of the thermal boundary layer region caused by the suspended nanoparticles around the vapor bubble as well as near the heated substrate. This phenomenon has been considered as one of the factors that tends to alter the condensation effects and, in turn, affects the bubble dynamics. Quantitative analysis of schlieren images revealed that the natural convective heat flux increases with increasing subcooling levels, while it decreases with increasing nanoparticle concentration. Deterioration in the natural convection phenomenon in the presence of suspended nanoparticles has been attributed to the reduced strength of thermal gradients adjacent to the heater substrate. On the other hand, evaporative heat flux was observed to decrease with increasing subcooling levels and increase with increasing concentration of nanofluids.
关键词： nucleate pool boiling,bubble dynamics,schlieren deflectometry,subcooling,heat transfer,nanofluids
更新于2025-09-23 15:23:52
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Challenges and opportunities for nanomaterials in spectral splitting for high-performance hybrid solar photovoltaic-thermal applications: A review
摘要： Hybrid photovoltaic-thermal (PV-T) collectors, which are capable of cogenerating useful thermal energy and electricity from the same aperture area, have a significantly higher overall efficiency and ability to displace emissions compared to independent, separate photovoltaic panels, solar thermal collectors or combinations thereof. Spectral splitting has emerged as a promising route towards next-generation high-performance PV-T collectors, and nanotechnology plays an important role in meeting the optical and thermal requirements of advanced spectral splitting PV-T collector designs. This paper presents a comprehensive review of spectral splitting technologies based on nanomaterials for PV-T applications. Emerging nanomaterials (nanofluids, nanofilms and nanowires) suitable for achieving spectral splitting based on reflection, diffraction, refraction and/or absorption approaches in PV-T collectors are presented, along with the associated challenges and opportunities of these design approaches. The requirements from such materials in terms of optical properties, thermal properties, stability and cost are discussed with the aim of guiding future research and innovation, and developing this technology towards practical application. Nanofluids and nanofilms are currently the most common nanomaterials used for spectral splitting, with significant progress made in recent years in the development of these materials. Nevertheless, there still remains a considerable gap between the optical properties of currently-available filters and the desired properties of ideal filters. Aiming to instruct and guide the future development of filter materials, a simple generalized method is further proposed in this paper to identify optimal filters and efficiency limits of spectral splitting PV-T systems for different scenarios. It is found that the optimal filter of a spectral splitting PV-T system is highly sensitive to the value of thermal energy relative to that of electricity, which therefore depends strongly on the application and location. The efficiency limit of spectral splitting PV-T collectors is significantly higher than that of standalone PV panels. The stability of nanomaterial filters remains a critical challenge for their long-term employment and also for high-temperature operation in practical applications.
关键词： Nanofilms,Spectral splitting,Nanomaterials,Thermal properties,Stability,Nanofluids,Optical properties,Cost,Nanowires,Hybrid photovoltaic-thermal (PV-T) collectors
更新于2025-09-23 15:21:01
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Study of thermal conductivity of synthesized Al2O3-water nanofluid by pulsed laser ablation in liquid
摘要： In the present study, Aluminum oxide (Al2O3) nanoparticles dispersed water based nanofluids were prepared via laser ablation in liquid method. Al2O3 nanoparticles were synthesized in deionized water using a nanosecond Nd-YAG pulsed laser operating at 1064 nm. The structural, optical and morphological characterizations of the produced nanofluids were performed. Thermal properties of the prepared samples were evaluated through thermal conductivity measurements which were carried out at various nanoparticles concentration and at temperatures ranging from 25 °C to 45 °C. Morphological analysis by transmission electron microscopy revealed spherically shaped Al2O3 nanoparticles with an average size of 9 nm. Moreover, the results indicated that the thermal conductivity of Al2O3-water nanofluid was improved as compared to the pure water. The increase in temperature and nanoparticles concentration leads to higher thermal conductivity of nanofluids. It was found that the thermal conductivity enhancement was around 8.6% at nanoparticles volume fraction of 0.7 vol.% and temperature of 45°C. This work proved the possibilities of fabricating Al2O3-water nanofluid with enhanced thermal conductivity via laser ablation in liquid medium without the use of hazardous chemicals and vacuum conditions. Therefore, the synthesized nanofluids have great potential to be applied in medium temperature applications.
关键词： thermal conductivity,nanofluids,temperature,Al2O3 nanoparticles,laser ablation
更新于2025-09-23 15:19:57
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Performance enhancement of photovoltaic panels using two types of nanofluids
摘要： One of the main problems that limit the extensive use of photovoltaic (PV) systems is the increase in the temperature of PV panels. Overheating of a PV module decreases the performance of the output power by 0.4% to 0.5% per 1°C over its rated temperature that in most cases is 25°C. An effective way of improving electrical performance (power output and efficiency) and reducing the rate of thermal degradation of a PV module is to reduce the operating temperature of the PV surface by a cooling medium. To achieve this, nanofluids can be considered as a potentially effective solution for cooling. In this study, two types of nanofluids, namely Al2O3 and TiO2 water‐based mixture of different volume flow rates and concentrations (0.01%, 0.05%, and 0.1%) by weight, were used. Also, three PV panels were cooled simultaneously using nanofluids, water, and natural air, respectively. Results showed that nanofluids for cooling enhanced heat transfer rate much better than water and natural air. Best results were achieved for TiO2 nanofluids at the considered concentration (0.1 wt%). Nanofluid cooling of turbulent flows for such an application has not been investigated before. These results represent the first application of nanofluid cooling in the turbulent flow regimes and in outdoor conditions including real solar irradiation.
关键词： photovoltaic module,Nusselt number,Al2O3,TiO2 nanofluids,heat transfer,electrical performance
更新于2025-09-23 15:19:57
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Introducing optical fiber as internal light source into direct absorption solar collector for enhancing photo-thermal conversion performance of MWCNT-H2O nanofluids
摘要： High-efficiency photo-thermal conversion is an attractive approach for solar thermal energy to alleviate energy crisis. In this work, MWCNT-H2O nanofluids were prepared and its photo-thermal conversion properties were characterized. Moreover, an optical fiber as internal light source was introduced into direct absorption solar collector (DASC), in which the photo-thermal conversion performance of the stored MWCNT-H2O nanofluids was systematically explored. The experimental results showed that the photo-thermal conversion performance of MWCNT-H2O nanofluids was improved by introducing optical fiber as internal light source into the DASC and a maximum photo-thermal conversion efficiency of 65.4% was acquired at the MWCNTs concentration of 0.010 wt.% and the optical fiber location of 15 mm. This study indicated that the MWCNT-H2O nanofluids applied in the DASC with optical fiber was a potential candidate for solar thermal energy.
关键词： direct absorption solar collector,nanofluids,optical fiber,Photo-thermal conversion
更新于2025-09-23 15:19:57
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Enhanced heat capacity of binary nitrate eutectic salt-silica nanofluid for solar energy storage
摘要： In concentrating solar power plants, the heat capacity of thermal storage media is a key factor that affects the cost of electricity generation. This work investigated the effective specific heat capacity of binary nitrate eutectic salts seeded with silica nanoparticles, using both experimental measurements and molecular dynamics simulations. The effects of the mass concentration (0–2.0 wt%) and average size (10, 20, and 30 nm) of the nanoparticles on the specific heat capacity value of nanofluids were analyzed. The results show that specific heat capacity increases when adding 10 nm silica nanoparticles up to 1.0 wt%, and then it decreases at higher concentrations. At this optimal mass concentration, the 20 nm nanoparticles displayed a maximum enhancement in the average specific heat capacity (by ~26.7%). The simulation results provided information about the different energy components in the system. The rate of potential energy change versus nanoparticle mass concentration was found to be maximized at 1.0 wt% concentration, which agrees with the experimental measurements. The potential energy components in the simulation system indicate that the change of Coulombic energy contributes the most to the variation of specific heat capacity.
关键词： Molten salt based nanofluids,Molecular dynamics simulation,Solar energy storage,Specific heat capacity
更新于2025-09-23 15:19:57
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MXene based new class of silicone oil nanofluids for the performance improvement of concentrated photovoltaic thermal collector
摘要： In this research work, MXene with a chemical formula of Ti3C2 is used for the first time with silicone oil to improve thermo-physical properties of MXene based silicone oil. This paper focuses on preparation, characterization, thermal properties, thermal stability and performance investigation of new class of silicone oil nanofluids induced with MXene in three different concentrations for a Concentrated Solar Photovoltaic Thermal (CPVT) collector. The thermal conductivity of the silicone oil-based MXene nanofluids is measured using a Transient Hot Bridge (THB) 500. Viscosity is measured using a Rheometer at various temperatures including 25, 50, 75, 100, and 125 °C. PerkinElmer Lambda 750 is used to measure optical absorbance. The highest thermal conductivity enhancement is found to be 64% for 0.1 wt% concentration of silicone oil-MXene nanofluid compared to pure silicone oil at 150 °C. The viscosity of MXene with silicone oil nanofluids is found to be independent of addition of MXene nanoparticles in the silicone oil base fluid. Viscosity is reduced by 37% when temperature is raised from 25 °C for different concentrations of MXene with silicone oil. Silicone oil-based MXene nanofluid with 0.1 wt% concentration is thermally stable up to ~380 °C. Introducing more MXene nanoparticles into silicone oil improves electrical efficiency of PV module due to better cooling of MXene based nanofluids. Higher solar concentration is resulted in higher average temperature of the PV module. This consequently raises thermal energy gain which is useful for different applications.
关键词： MXene,Nanofluids,CPVT,Thermo-physical properties
更新于2025-09-19 17:13:59
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Energy, exergy and efficiency of four photovoltaic thermal collectors with different energy storage material
摘要： Hybrid photovoltaic thermal (PV/T) is a technology with many variations and designs. The aim of this unit is cooling down PV temperature while producing hot water. In this paper, different PV/T designs are compared in terms of energy, exergy and efficiency. Data from experiments and numerical calculations conducted at Bangi, Malaysia was used for the comparisons. The proposed systems were tested in outdoor conditions. The designs in question are water-based PV/T, water-based PV/T with PCM tank, nanofluid-based PV/T with nano-PCM tank and conventional PV module. Effect of mass flow rate and solar irradiance are emphasized in this paper. The highest thermal efficiency, thermal energy and electrical exergy produced are found for PV/T with nanofluids and nano-PCM with around 72%, 14 kW and 76.152, respectively. All PV/T systems proposed exhibit better performance than the conventional PV module. These findings highlight the utility of PV/T technology and its massive potential to energize and popularize the solar energy field.
关键词： Nanofluids,PV/T,Nano-PCM,Exergy,Efficiency
更新于2025-09-19 17:13:59
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Performance Analysis of Flat Plate Solar Collector using Al2O3/Distilled Water Nanofluid: An Experimental Investigation
摘要： Owing to how effectively it can convert solar energy into usable form, solar thermal technology has gained a lot of importance during the recent years. Heat exchangers, refrigeration, air conditioning, material science engineering, etc. are the biggest proponents incorporating solar technology along with nano particles for their high thermal conductivity. This study concerns with the effect of water based Al2O3 Nano fluid on the performance of solar water heater- Flat plate type. In the study, the dispersion quality of nanoparticles in fluid was enhanced using high quality surfactant sodium dodecyl sulfate (SDS). The experiments were conducted at Amity University Rajasthan, Jaipur, India (27.1721° N, 75.9542° E) which has an annual average solar irradiance 5.56 kWh/m2/day. Different conditions like flow rate, pressure, climatic conditions, time, solar collector inclination angle, composition of Nano fluid etc. were tested. The Al2O3 concentration varied from 0.1 to 0.3 vol. percentage. The tests were performed at different mass flow rates 1-3 LPM. The measured values of the thermal conductivity in the range of 0.610-0.622 W/m-k. Results indicated that by increasing the volume fraction of Al2O3 from 0.1% to 0.3%, there is a 21.32% growth in collector efficiency.
关键词： Nanofluids,Solar collector-flat plate type,Solar Energy,Collector Efficiency
更新于2025-09-16 10:30:52
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Role on nanofluids in cooling solar photovoltaic cell to enhance overall efficiency
摘要： The electrical conversion efficiency of Solar photovoltaic module strongly depends on the operating temperature. Only up to 20% of the incident solar irradiation is converted to electricity and rest energy either reflected back to atmosphere or converted into heat and thereby increasing the cell temperature. As the cell temperature rises, the electrical efficiency decreases. There is need to cool down temperature of the solar photovoltaic panel to get maximum electrical conversion efficiency. Researchers have implemented many techniques for cooling solar PV by active and passive cooling technique. Active cooling uses air, water, nanofluids etc for cooling where as in passive cooling uses of phase change materials like paraffin wax, eutectics, organic materials, cotton wick etc for the cooling purpose. Nanofluids are used to bring down the temperature of the panel by increasing the thermal conductivity of base fluids. In this paper, emphasis has been given to present the effect of nanofluids as coolant in solar photovoltaic panel.
关键词： Nanofluids,Electrical conversion efficiency,Solar Photovoltaics,Thermal conductivity,Overall efficiency
更新于2025-09-12 10:27:22