An experimental investigation on the effect of pH variation of MWCNT–H2O nanofluid on the efficiency of a flat-plate solar collector

Yousefi, Tooraj; Shojaeizadeh, Ehsan; Veysi, Farzad; Zinadini, Sirus

doi:10.1016/j.solener.2011.12.003

Cited by 266 publications

(80 citation statements)

References 30 publications

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“…A variety of direct absorption nanoparticles materials had have been analyzed in terms of the enhancement in the photothermal performance, including Ag [27][28][29], Au [30][31][32], CNT (carbon nanotubes) [33][34][35], Cu [36], Al 2 O 3 [37,38], graphite [17], graphene [22], and TiO 2 [39]. In addition to the volumetric heating, direct vapor generation due to localized heating of the As far as the steam generation mechanism is concerned, for nanobubbles to be produced around heated nanoparticles, it has been shown analytically that a minimum radiation flux of 3×10 8 W/m 2 is required to produce nanobubbles on heated nanoparticles [46,49,50], which can may only be reached developed by powerful laser beams.…”

Section: Introductionmentioning

confidence: 99%

Volumetric solar heating and steam generation via gold nanofluids

et al. 2017

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Volumetric solar absorption using nanofluids can minimize the thermal loss by trapping the light inside the fluid volume. A strong surface boiling with the underneath fluid still subcooled could have many interesting applications, whose mechanism is however still under strong debate. This work advanced our understanding on volumetric fluid heating by performing a novel experiment under a unique uniform solar heating setup at 280 Suns, with a particular focus on the steam production phenomenon using gold nanofluids. To take the temperature distribution into account, a new integration method was used to calculate the sensible heating contribution. The results showed that the photothermal conversion efficiency was enhanced significantly by gold nanofluids. A three-stage heating scenario was identified and during the first stage most of the energy was absorbed by the surface fluid, resulting in rapid vapor generation with the underneath fluid still subcooled. The condensed vapor analysis showed no nanoparticle escaping even under vigorous boiling conditions. Such results reveal that nanoparticle enabled volumetric solar heating could have many promising applications including clean water production in arid areas where abundant solar energy is available. highlights  Novel experiment was performed for nanofluids at a focused solar flux of 280 Suns. Strong surface evaporation was enabled while the bulk fluid was still subcooled  A new integration method was used to calculate photothermal conversion efficiency  Gold nanofluid (0.04w%) increased photothermal conversion efficiency by 95%. The authors are grateful for all the constructive comments from the reviewer and the Editor. Most of the comments were concerned on the presentation of the work. We have addressed all these concerns in the revised version, and a point-by-point reply is supplied below Reviewer #1:The authors of the present work experimentally investigated the surface boiling and steam production mechanism of gold nanofluids under uniform solar heating of 280 Suns. Various concentrations of gold nanofluids were produced and the generated steam was condensed and tested to reveal the presence of any nanoparticles.The study provides good insight to the surface boiling phenomenon of nanofluids and is in consonant with recent trend of investigation. However, there are several problems that need to be addressed before considering for publication in Applied Energy.1. The Abstract, in its current state is incomplete. It is more like a conclusion and needs to be re-written.Action: the abstract was rewritten with more focus on the novelty 2. The use of "gold nanofluids" should be mentioned in the Title and Abstract.Action: The title was slightly changed to reflect the content, and the was used in the title and the abstract in the revised version.3. In the statement: "For example, researchers [43] from Rice University", the Institution name should be replaced by the Authors' name.Action: T was used to replace the institution name in the revised version....

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Section: Introductionmentioning

confidence: 99%

Volumetric solar heating and steam generation via gold nanofluids

et al. 2017

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“…According to [19][20][21], ( ) and are called absorbed energy parameter and removed energy parameter respectively.…”

Section: Energy Analysismentioning

confidence: 99%

“…They demonstrated that 4.34% reduction of entropy generation, 22.15% enhancement of heat transfer coefficient and 1.58% pumping power penalty when using CuO nanofluid compared to that of water. Yousefi et al [19][20][21] carried out three different experimental analyses using MWCNT-H2O and Al2O3-H2O nanofluids in a flat-plate solar collector. They pointed out that he efficiency of flat-plate solar collector increased by 28.3% using 0.2 wt% Al2O3 and 15.63% using 0.4 wt% Al2O3 with surfactant compared to water.…”

Section: Introductionmentioning

confidence: 99%

Influence of nanofluids on the efficiency of Flat-Plate Solar Collectors (FPSC)

et al. 2017

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Abstract.A numerical investigation is performed using finite volume method to study the laminar heat transfer in a three-dimensional flat-plate solar collector using different nanofluids as working fluids. Three nanofluids with different types of nanoparticles (Ag, MWCNT and Al2O3 dispersed in water) with 1-2 wt% volume fractions are analyzed. A constant heat flux, equivalent to solar radiation absorbed by the collector, is applied at the top surface of the absorber plate. In this study, several parameters including boundary conditions (different volume flow rates, different fluid inlet temperatures and different solar irradiance at Skudai, Malaysia), different types of nanoparticles, and different solar collector tilt angles are investigated to identify their effects on the heat transfer performance of FPSC. The numerical results reveal that the three types of nanofluid enhance the thermal performance of solar collector compared to pure water and FPSC with Ag nanofluid has the best thermal performance enhancement. For all the cases, the collector efficiency increased with the increase of volume flow rate while fluid outlet temperature decreased. It is found that FPSC with tilt angle of 10° and fluid inlet temperature of 301.15 K has the best thermal performance.

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“…Yousefi et al [29] investigated the effect of pH of MWCNT-H2O nanofluid on the efficiency of a flat-plate solar collector as seen in Figure 16. The experiments were carried out using 0.2 wt% MWCNT (10-30 nm) with various pH values (3.5, 6.5 and 9.5) and with Triton X-100 as an additive.…”

Section: Role Of the Phmentioning

confidence: 99%

“…Choosing the right surfactant is mainly dependent on the properties of the base fluids and particles Yousefi et al [29] MWCNT/water flat plate solar collector They found that increasing or decreasing the pH with respect to the pH of the isoelectric point (IEP) would enhance the positive effect of nanofluids on the efficiency of the solar collector Sardarabadi et al [30] SiO2/water PV/T Thermal efficiency of the PV/T collector for the two cases of 1 and 3 wt% of silica/water nanofluid increased 7.6% and 12.8%, respectively.…”

Section: Using Nanofluids In Solar Pondmentioning

confidence: 99%

Performance evaluation of nanofluids in solar energy: a review of the recent literature

Bozorgan

Shafahi

2015

Micro and Nano Syst Lett

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Utilizing nanofluid as an absorber fluid is an effective approach to enhance heat transfer in solar devices. The purpose of this review is to summarize the research done on the nanofluids' applications in solar thermal engineering systems in recent years. This review article provides comprehensive information for the design of a solar thermal system working at the optimum conditions. This paper identifies the opportunities for future research as well.

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An experimental investigation on the effect of pH variation of MWCNT–H2O nanofluid on the efficiency of a flat-plate solar collector

Cited by 266 publications

References 30 publications

Volumetric solar heating and steam generation via gold nanofluids

Volumetric solar heating and steam generation via gold nanofluids

Influence of nanofluids on the efficiency of Flat-Plate Solar Collectors (FPSC)

Performance evaluation of nanofluids in solar energy: a review of the recent literature

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