Investigation of the effect of pH adjustment on the stability of nanofluid

M.T, Umar, S.T.,; Sulaiman, Fauziah; Abdullah, Nurhayati; Mohamad, Saiful Najmee

doi:10.1063/1.5066987

Cited by 44 publications

(16 citation statements)

References 11 publications

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“…Therefore, to prevent the flocculation of NPs and prepare stable nanofluids, the pH value should be kept significantly less or more than the IEP. 36 In this study, the pH of all the fluid samples is 7.5−8.0 and unchanged during ζ measurements.…”

Section: Methodsmentioning

confidence: 87%

“…Júnior et al observed that ζ of suspensions is positive when pH is below the isoelectric point (IEP), which is defined as the point with zero ζ of the suspensions, but it is negative when pH is above IEP. Therefore, to prevent the flocculation of NPs and prepare stable nanofluids, the pH value should be kept significantly less or more than the IEP . In this study, the pH of all the fluid samples is 7.5–8.0 and unchanged during ζ measurements.…”

Section: Methodsmentioning

confidence: 99%

“…ζ can be used to calculate reduced surface potential and, in turn, the double-layer force. Factors such as temperature, pressure, and pH can affect ζ measurements. ,, Al Mahrouqi et al observed that ζ of carbonate samples increases with temperature at low ionic strength but it does not have a discernible trend with increasing temperature at high ionic strength. Rodríguez and Araujo tested the effects of temperature and pressure on ζ of reservoir minerals and found that the absolute values of ζ of all minerals in low-salinity NaCl increase with temperature.…”

Section: Methodsmentioning

confidence: 99%

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A Theoretical Explanation for Wettability Alteration by Adding Nanoparticles in Oil-Water-Tight Rock Systems

2021

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We evaluated the idea of adding nanoparticles in an aqueous phase to enhance its wetting affinity to siltstone core plugs by conducting dynamic contact-angle experiments and by calculating the total interaction energy. We analyzed the performance of a colloidal dispersion with highly surface-modified silicon dioxide nanoparticles (NP). The rock samples are oil-wet when they are initially aged in the reservoir brine, and they are water-wet when initially soaked in the NP solutions (limiting conditions). To mimic the downhole conditions when the pumped fluid with nanoparticles is mixed with reservoir brine, we measured the change in contact angle of oil droplets initially equilibrated on the rock surface soaked in the reservoir brine during diffusion of the introduced nanoparticles. The results show that the diffusion of nanoparticles through the brine toward the oil droplet alters the system wettability from oil-wet to water-wet conditions. To investigate the mechanisms responsible for the observed wettability alteration, we analyzed aqueous-film stability using the Derjaguin, Landau, Verwey, and Overbeek theory. The calculated interaction energy for the cases of NP solutions is higher than that for the tap water and brine cases, indicating stronger repulsion between the rock and oil across the film of NP solution, leading to a more stable film. Increasing water salinity reduces the stability of water film due to the reduction of total interaction energy. The wettability alteration by the NP solution is more pronounced in the presence of low-salinity water.

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Section: Methodsmentioning

confidence: 87%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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A Theoretical Explanation for Wettability Alteration by Adding Nanoparticles in Oil-Water-Tight Rock Systems

2021

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“…These high zeta potentials were attributed to the surfactant layers being adsorbed onto the particle’s surface, which weakens the Van der Waals forces and prevents aggregation. Moreover, the stability of nanofluids is also dependent on the pH value, because the magnitude of the surface charge is also indicated by the pH value of the colloidal system [ 39 ]. Therefore, the pH of all samples was measured and correlated with the zeta potential, as shown in Figure 4 a,c,e.…”

Section: Resultsmentioning

confidence: 99%

Two-Dimensional Tungsten Disulfide-Based Ethylene Glycol Nanofluids: Stability, Thermal Conductivity, and Rheological Properties

et al. 2020

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Developing stable nanofluids and improving their thermo-physical properties are highly important in heat transfer applications. In the present work, the stability, thermal conductivity, and rheological properties of tungsten disulphide (WS2) nanoparticles (NPs) with ethylene glycol (EG) were profoundly examined using a particle size analyzer, zeta-sizer, thermal property analyzer, rheometer, and pH measuring system. WS2 NPs were characterized by various techniques, such as XRD (X-Ray Diffraction), FTIR (Fourier Transform Infrared Spectroscopy), FESEM (Field emission scanning electron microscopy), and high-resolution transmission electron microscopy (HRTEM). The nanofluids were obtained with the two-step method by employing three volume concentrations (0.005%, 0.01%, and 0.02%) of WS2. The influence of different surfactants (Sodium dodecyl sulphate (SDS), Sodium dodecylbenzenesulfonate (SDBS), Cetyltrimethylammonium bromide (CTAB)) with various volume concentrations (0.05–2%) on the measured properties has also been evaluated. Pristine WS2/EG nanofluids exhibit low zeta potential values, i.e., −7.9 mV, −9.3 mV, and −5 mV, corresponding to 0.005%, 0.01%, and 0.02% nanofluid, respectively. However, the zeta potential surpassed the threshold (±30 mV) and the maximum values reached of −52 mV, −45 mV, and 42 mV for SDS, SDBS, and CTAB-containing nanofluids. This showed the successful adsorption of surfactants onto WS2, which was also observed through the increased agglomerate size of up to 1720 nm. Concurrently, particularly for 0.05% SDS with 0.005% WS2, thermal conductivity was enhanced by up to 4.5%, with a corresponding decrease in viscosity of up to 10.5% in a temperature range of (25–70 °C), as compared to EG. Conversely, the viscoelastic analysis has indicated considerable yield stress due to the presence of surfactants, while the pristine nanofluids exhibited enhanced fluidity over the entire tested deformation range. The shear flow behavior showed a transition from a non-Newtonian to a Newtonian fluid at a low shear rate of 10 s−1. Besides this, the temperature sweep analysis has shown a viscosity reduction in a range of temperatures (25–70 °C), with an indication of a critical temperature limit. However, owing to an anomalous reduction in the dynamic viscosity of up to 10.5% and an enhancement in the thermal conductivity of up to 6.9%, WS2/EG nanofluids could be considered as a potential candidate for heat transfer applications.

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“…The addition of surfactant material seems to improve the mixing process and stability of these fluids, as well as adjusting the pH value. 70 However, for a more effective assessment of the system's viability, it is necessary to calculate the pumping losses and optimum pumping size. The pumping energy requirements are then subtracted from the energy produced by the PV/T system to get its electrical exergy.…”

Section: Referencesmentioning

confidence: 99%

Nano enhanced fluids and latent heat storage material for photovoltaic modules: A case study and parametric analysis

2021

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Thermal stress causes reduction in the open circuit voltage of photovoltaic (PV) modules which results in a reduction in overall power generation. Photovoltaic thermal (PV/T) collectors have been used to mitigate this issue by providing both cooling of the cell temperature and yielding thermal energy in the same space. However, the implementation of PV/T systems in the industry is still lacking and requires further innovative solutions to achieve higher electrical and thermal efficiencies. In this article, a case study experimental and parametric analysis of a PV/T system with nano-phase change material and nanofluid, as the heat transfer fluid, is presented. The system was tested in Bangi, Malaysia and the findings have been compared with previous studies in the literature. The findings of the evaluation show average and peak overall PV/T efficiencies of 61.6% and 77.8%, respectively. Moreover, the electrical efficiency of the PV and PV/T averaged at 9.9% and 13.1%, respectively. The main reason for the drop in the PV module was its average cell temperature which was around 45.6 C, while the PV/T's average cell temperature reached 39.2 C. Finally, the average thermal efficiency of the PV/T was around 48.5% when the mass flowrate was 0.175 kg/s.

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Investigation of the effect of pH adjustment on the stability of nanofluid

Cited by 44 publications

References 11 publications

A Theoretical Explanation for Wettability Alteration by Adding Nanoparticles in Oil-Water-Tight Rock Systems

A Theoretical Explanation for Wettability Alteration by Adding Nanoparticles in Oil-Water-Tight Rock Systems

Two-Dimensional Tungsten Disulfide-Based Ethylene Glycol Nanofluids: Stability, Thermal Conductivity, and Rheological Properties

Nano enhanced fluids and latent heat storage material for photovoltaic modules: A case study and parametric analysis

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