A numerical and experimental investigation on the performance of a low-flux direct absorption solar collector (DASC) using graphite, magnetite and silver nanofluids

Gorji, Tahereh B.; Ranjbar, A.A.

doi:10.1016/j.solener.2016.06.023

Cited by 155 publications

(54 citation statements)

References 49 publications

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“…The present work carries out the performance analysis of a new type of direct-absorption parabolic trough solar collector. Inspired by the flat-plate DASCs where a mirror is employed at the bottom of the channel to enhance the optical path length of sun rays inside the collector [9,31], we propose to apply a highly reflective metallic coating on the upper half of the inner tube outer surface such that the optical path length for the concentrated rays can be doubled due to the reflection. It is worth mention that the radiation heat loss from the inner tube outer surface can also be reduced greatly due to the low emissivity of a metallic coating compared to that of bare glass.…”

Section: Introductionmentioning

confidence: 99%

Performance analysis of a direct-absorption parabolic-trough solar collector using plasmonic nanofluids

2019

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A parabolic trough solar collector is a dominant technology for high-temperature industrial applications, but efficient use of a conventional surface-based parabolic trough solar collector (SBPTSC) is limited by its high radiation loss due to the high surface temperature. Recently, direct-absorption parabolic trough solar collector (DAPTSC) using nanofluids has been proposed, and its thermal efficiency has been reported to be 5-10% higher than the conventional SBPTSC for inlet temperature up to 250 • C. However, the inner tubes of the receivers of the existing DAPTSCs are all transparent, so the sun rays entering the inner tube can only travel once through the nanofluids. As a result, the optical path length for the sun rays is limited by the inner tube size, which in turn requires high value of the absorption coefficient of nanofluids. Due to the approximately linear relation between the absorption coefficient and the particle concentration, higher absorption coefficient is likely to cause particle agglomeration, leading to detrimental effects on maintaining stable collector performance. In the current study, the transparent DAPTSC is improved by applying a reflective coating on the upper half of the inner tube outer surface, such that the optical path length is doubled compared to the transparent DAPTSC; thus, the absorption coefficient of the nanofluids can be reduced accordingly. The coated DAPTSC is found to have obvious advantage compared to the transparent DAPTSC at absorption coefficient below 0.5 cm −1 for a receiver with inner tube diameter of 7 cm. In addition, performance of the transparent DAPTSC, the coated DAPTSC and the SBPTSC with black chrome coating have been compared to explore their advantageous operation conditions, such as inner tube diameter, flow rate, and inlet temperature, with or without a glass envelope for vacuum evacuation. The findings in this study will facilitate the use of nanofluids in a parabolic trough solar collector with more stability and provide a guide for choosing suitable type of parabolic trough solar collectors for specific working conditions.

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Section: Introductionmentioning

confidence: 99%

Performance analysis of a direct-absorption parabolic-trough solar collector using plasmonic nanofluids

2019

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“…Delfani et al used water/ethylene glycol (70:30 in volume) based MWCNT nanofluid in direct absorption solar collector and collector efficiency was increased 10-29% with increase in concentration compared to base-fluid. Gorji and Ranjbar [42]studied with water based graphite, Ag and Fe2O3 nanofluid in same type collector and found that all nanofluids have higher efficiency compared to base-fluid and maximum enhancement was observed for magnetite nanofluid. Dugaria et al [43] studied numerically with water based single wall carbon nanohorn in direct absorption solar receiver.…”

Section: Solar Collectorsmentioning

confidence: 99%

Carbon-based Nanofluid Applications in Solar Thermal Energy

2019

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Renewable energy sources such as solar, wind and geothermal are proposed as an alternative to fossil fuels whose excessive use causes global warming. The most popular one of the renewable energy sources is considered as solar energy due to the fact that required energy is provided by the sun entire year around the world. Solar energy systems convert the solar radiation to the useful heat or electricity. In order to achieve better performance in solar thermal systems many studies have been conducted. Some of these studies suggest that heat transfer fluid could be changed with the nanofluids which can be defined as new generation heat transfer fluid. Nanofluids are suspensions of nano-sized particles such as metals, metal-oxides, and Carbon-allotropes (C), in the conventional base-fluids (water, ethylene glycol and oil). Using nanofluid enhances the efficiency and thermal performance of solar systems due to their better thermophysical and optical properties. Recently, C-based nanofluids are getting attention due to their enhanced thermal conductivity and absorptivity at even low concentrations. The results show that C-based nanofluids have a potential to use in solar energy systems: solar collectors, solar stills, photovoltaic/thermal systems.

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“…One of the suggested modifications is to replace regular working fluids by Nanofluids . Several nanoparticles have been investigated as absorption medium; nonetheless, carbon‐based nanofluid seems to be more competitive as a result of its broader absorption spectra . Multiwalled carbon nanotube (MWCNT) mixed with water was found to improve the heat transfer coefficient by 33% to 40% for a concentration of 0.25 wt% for both turbulent and laminar flows …”

Section: Introductionmentioning

confidence: 99%

“…2 Several nanoparticles have been investigated as absorption medium; nonetheless, carbon-based nanofluid seems to be more competitive as a result of its broader absorption spectra. 3 Multiwalled carbon nanotube (MWCNT) mixed with water was found to improve the heat transfer coefficient by 33% to 40% for a concentration of 0.25 wt% for both turbulent and laminar flows. 4 To run the solar system on nanofluids, a closed-loop design is recommended where an internal or external heat exchanger will hold and exchange heat between the new working fluid and water.…”

Section: Introductionmentioning

confidence: 99%

Indirect thermosiphon flat‐plate solar collector performance based on twisted tube design heat exchanger filled with nanofluid

2020

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Summary Stationary solar collector such as flat‐plate collector is a thermal device, which traps solar energy and converts it into heat that can be used in industrial and domestic applications such as water heating. Flat‐plate collector thermal performance enhancement is investigated in this research paper. Two cross‐sectional geometries of the tube in the heat exchanger were investigated; a normal circular tube and a twisted tube were used in the experiment. The aim of the twisted tube exchanger is to enhance the performance of heat transfer of the tubes and to reduce the shell pressure drop; flat‐plate solar collector is the used application to study the heat exchanger performance. Both twisted tubes heat exchanger and normal circular tubes heat exchanger were examined in the same location and conditions with the same solar collector, both were used in the heat exchanger to study their effect, with two different working fluids, which are distilled water and multiwalled carbon nanotube (MWCNT)/water nanofluid. The system shows an increase in the performance when twisted tubes were used in the system compared with the circular tubes in both distilled water and MWCNT/water nanofluid by 12.8% and 12.5%, respectively, with an improvement by 34% for twisted tubes with MWCNT compared with normal circular tubes with distilled water.

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A numerical and experimental investigation on the performance of a low-flux direct absorption solar collector (DASC) using graphite, magnetite and silver nanofluids

Cited by 155 publications

References 49 publications

Performance analysis of a direct-absorption parabolic-trough solar collector using plasmonic nanofluids

Performance analysis of a direct-absorption parabolic-trough solar collector using plasmonic nanofluids

Carbon-based Nanofluid Applications in Solar Thermal Energy

Indirect thermosiphon flat‐plate solar collector performance based on twisted tube design heat exchanger filled with nanofluid

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