Liquid Nanofluid Research Articles

Nanoparticle migration in nanofluid film boiling: A numerical analysis using the continuous-species-transfer method

Investigating the boiling behavior of nanofluids remains a topic of considerable research interest. The existing theoretical framework often underscores Brownian motion and thermophoresis among the predominant mechanisms that influence nanoparticles' movement within nanofluids. However, most current numerical models addressing nanofluid boiling either neglect these mechanisms or incorporate them inadequately. A comprehensive review of the literature reveals two primary gaps. The larger set of numerical studies on nanofluids boiling does not account for any governing equation for nanoparticle concentration, neglecting the primary mechanisms of nanoparticle movement. The smaller set includes such an equation but limits its application to the vapor domain, thereby overlooking the liquid nanofluid phase. Moreover, in the context of film boiling involving nanofluids, an insulating vapor film forms between the nanofluid and the heated surface. This vapor film is dynamic, experiencing evaporation at its outer boundary, leading to an increase in nanoparticle concentration at the vapor-liquid interface—another aspect always neglected in existing numerical models. To address these research gaps, this study introduces a specialized governing equation employing the Continuous-Species-Transfer method within the framework of Computational Multi-Fluid Dynamics. Importantly, it also incorporates governing equations for thermophoresis and Brownian motion to account for the motion of nanoparticles. The method's efficacy is further corroborated by solving a two-dimensional axisymmetric film boiling problem on a vertical cylinder, with results aligning well with analytical studies that consider Brownian motion and thermophoretic behavior. Overall, the study fills a critical gap in the literature by providing a comprehensive tool for examining complex interfacial behaviors in nanofluid film boiling.

Ionic Liquids Facilitate the Dispersion of Branched Polyethylenimine Grafted ZIF-8 for Reinforced Epoxy Composites.

Metal-organic frameworks (MOFs) have been previously shown as an emerging modified class of epoxy resin. In this work, we report a simple strategy for preventing zeolitic imidazolate framework (ZIF-8) nanoparticles from agglomerating in epoxy resin (EP). Branched polyethylenimine grafted ZIF-8 in ionic liquid (BPEI-ZIF-8) nanofluid with good dispersion was prepared successfully using an ionic liquid as both the dispersant and curing agent. Results indicated that the thermogravimetric curve of the composite material had no noticeable change with increasing BPEI-ZIF-8/IL content. The glass transition temperature (Tg) of the epoxy composite was reduced with the addition of BPEI-ZIF-8/IL. The addition of 2 wt% BPEI-ZIF-8/IL into EP effectively improved the flexural strength to about 21.7%, and the inclusion of 0.5 wt% of BPEI-ZIF-8/IL EP composites increased the impact strength by about 83% compared to pure EP. The effect of adding BPEI-ZIF-8/IL on the Tg of epoxy resin was explored, and its toughening mechanism was analyzed in combination with SEM images showing fractures in the EP composites. Moreover, the damping and dielectric properties of the composites were improved by adding BPEI-ZIF-8/IL.

Dynamic Monitoring and Enhanced Oil Recovery Evaluation of the Water Flooding Process of Liquid Nanofluids in Tight Reservoirs

The CT scanning technology can observe fluid saturation distribution in the rock at different times during water flooding in tight reservoirs. However, this technology has not been used to study the water flooding characteristics in changing the wettability of liquid nanofluids. First, this study evaluated the basic properties of a nonionic liquid nanofluid, including the contact angle (CA), interfacial tension (IFT), and aqueous stability tests. Then, the water flooding process in tight rocks is dynamically monitored by the CT scanning technology. The water flooding characteristics of liquid nanofluids changing reservoir wettability are analyzed by measuring the rock’s water phase saturation distribution at different times. Finally, the spontaneous imbibition experiment evaluated the enhanced oil recovery of liquid nanofluids. The results show that the particle size of the liquid nanofluid is at the nanometer level (7.5 nm) and can change the wettability of oil-wet to water-wet. Liquid nanofluid has low interfacial tension and can exist stably in brine with a high salinity (20,000–50,000 ppm). In water flooding, the front profile of water phase saturation changes obviously, and it is driven forward with a similar “piston” type. Compared with the brine water, the water invasion front gradually becomes uniform, which is strong evidence that a liquid nanofluid can change the wettability of rocks. Besides, the invasion depth of the fracturing fluid with liquid nanofluids is deeper than that of brine water and displaces more oil. Finally, the spontaneous imbibition test shows that the recovery factor of high-concentration (1 wt %) liquid nanofluids increases by 28.9% compared with that of brine water. This paper provides theoretical support for applying liquid nanofluids in tight reservoirs.

Physicochemical characterisation of graphene-ammonium lactate ionic liquid nanofluid

A new series of nanofluids based on graphene dispersed in 2-hydroxyethylammonium lactate (ML) ionic liquid was developed. Concentrations of 0.1, 0.5 and 1 wt% of graphene were studied and these dispersions were stable after 2 months. Raman spectra showed a strong interaction between ML and graphene. The effect of the concentration of graphene and temperature on the viscoelastic behaviour and conductivity of the nanofluids was studied. An unexpected decrease in the viscosity was found with a low concentration of graphene due to the suppression of hydrogen bonding of the ionic liquid. Shear thinning effects appeared with higher concentrations of graphene and Ostwald and Herschel-Bulkley equations were used to describe the steady-state viscosity results. Creep-recovery tests were also performed, and the data were fitted to a complex Burgers model for the nanofluid with 1 wt% of graphene, with a 47 % of elastic response. The complexity of the model was related to the presence of different molecular arrangements in the nanofluid. An enhancement of the conductivity was observed with increasing values of the graphene concentration. The effect of temperature on viscosity and electrical conductivity was successfully modelled by using both Vogel-Fulcher-Tammann and Power Law equations. Electrochemical characterisation at room temperature was also carried out, finding an irreversible oxidation at 1 V only for the highest concentration (1 wt%). The concentration of percolation was estimated in the range of 0.5 to 1 wt% of graphene.

Hybridized Fe/Ru-SiMWCNT-ionic liquid nanofluid for CO2 conversion into carbamate using superoxide ion

Suppressing the nucleophilic susceptibility of ionic liquids based nanofluid is necessary for energy storage and superoxide ion (O2•−) utilization. This study reports the development of novel pseudocapacitive Fe/Ru-SiMWCNT nanofluid comprising of Fe3O4, RuO2, SiO2, and MWCNT hybridized phases. The Fe/Ru-SiMWCNT nanohybrid possessed CO2 and O2 sorption capability, as confirmed from the temperature-programmed desorption experiments. Detailed spectroscopy techniques characterize the Fe/Ru-SiMWCNT nanohybrid component's physicochemical and morphological properties. The novel ionic liquid (IL) based nanofluid index is Fe/Ru-SiMWCNT/1-(2-methoxyethyl)-1-methylpyrrolidinium tris(pentafluoroethyl) trifluorophosphate. Therefore, stable O2•− was generated therein at −0.445 V vs Ag/AgCl and recorded long-term stability for 2 days with 87.31 % efficiency. Moreover, the O2•− mediated CO2 conversion to C2O62− at −0.54 V vs Ag/AgCl with 97.90 % energy efficiency. Also, the normalized exchange current density in the nanofluid was 2.20 mA/cm2, which is higher than 1.94 mA/cm2 observed in the IL counterpart. The high normalized exchange current density is due to Fe/Ru-SiMWCNT nanohybrid phase's pseudocapacitance. Accordingly, this pseudocapacitive capability enables converting O2 and CO2 in the nanofluid with lower activation overpotential of −0.305 and −0.460 V vs Ag/AgCl, respectively. In contrast, the conversion of O2 and CO2 in the IL required higher activation overpotential of −0.826 and −1.013 V vs Ag/AgCl, respectively. The electrolysis of O2/CO2 in the nanofluid containing diethanolamine at −1.564 V vs Ag/AgCl, 60 °C and 1.0 h produced methyl 2-hydroxyethyl (methyl) carbamate as the primary product. The heteronuclear multiple bond correlation spectroscopy analysis finally elucidated the carbamate structure by two strong correlations between the protons and carbons in the vicinity of three and four bonds apart. Therefore, this study highlights the control design of electrochemically stable IL-based nanofluids robust for reactive oxygen species, energy storage and conversion.

Mechanism of using liquid nanofluid to enhance oil recovery in tight oil reservoirs

Liquid nanofluid (LNF) has been widely used for enhanced oil recovery (EOR) in tight oil reservoirs in recent years. However, the mechanism of oil recovery by LNF flooding is still unclear. In this study, a series of experiments were conducted to explore this problem. The properties of LNF were first evaluated by testing contact angles and particle size distributions. Then, the blocking and adsorption in the matrix were investigated. After that, the imbibition with nuclear magnetic resonance (NMR) was conducted to evaluate the imbibition recovery and process. Finally, the retained permeability was studied through pressure transmission tests. Our results showed that the LNF can be transported in the nano-scale pores and pore throats without bridging in the formation. This increased sweep volume and efficiency while maintaining low adsorption. During the imbibition process, with the wettability alteration and proper interfacial tension, the LNF entered small pores first to displace oil. Moreover, when injected into the reservoir, LNF in pores could avoid the exhaustion of formation pressure to prolong the effective production period. Finally, the higher retained permeability could reduce the flow resistance and energy consumption while increasing the production indirectly. Our study has not only provided a method to evaluate a chemical fracturing fluid additive but also revealed a new mechanism of LNF flooding in tight oil reservoirs.

Enhanced fossil hydrogen energy recovery through liquid nanofluid huff-n-puff in low permeability reservoirs

Surfactant huff-n-puff can enhance fossil hydrogen energy recovery from low permeability reservoirs. However, due to the high cost and adsorption of surfactant, its commercial application is limited. Liquid nanofluid (LNF) has been widely used in hydraulic fracturing since it can significantly reduce the adsorption. In this study, a series of experiments were conducted to investigate the potential of LNF huff-n-puff. First, the spontaneous and dynamic imbibition with NMR was conducted to study the imbibition oil recovery for the LNF. The results showed that the spontaneous imbibition recovery of LNF is 1.43 folder than brine. Besides, the LNF enters the small pores first in spontaneous imbibition. In the process of dynamic imbibition, the LNF enters the larger pore with smaller resistance first, then enters the small pore around the flow path. After dynamic imbibition, the imbibition recovery in small pores increased 54%. Moreover, pressure transmission tests (PTT) were conducted to evaluate the increasing rate of reservoir pressure. This work provides a new view of how surfactant or LNF functions in the process of huff-n-puff.

Impacts of pore structure and wettability on distribution of residual fossil hydrogen energy after imbibition

Due to the heterogeneity of the pore structure, there is still much residual fossil hydrogen energy in the pore space. In this study, the distribution of residual fossil hydrogen energy after imbibition with liquid nanofluid (LNF) has been studied through the. Firstly, relevant properties of the LNF were tested, including particle size, wettability alteration, and interfacial tension (IFT). Then, one micromodel under both oil-wet and water-wet conditions was used to elucidate the difference of residual oil after imbibition. Moreover, the difference of imbibition processes with oil-wet and water-wet models was further studied. Finally, the influence of dimensions and coordination numbers of pores was investigated. Besides, the impact of fluid type on imbibition efficiency was also compared through microfluidic experiments. Results show that the residual oil saturation is significantly higher in the oil-wet micromodel than in the water-wet micromodel, even the wettability alteration additive was used. There are four kinds of locations for residual oil after imbibition in water-wet micromodel, while only three kinds of locations for residual oil in oil-wet micromodel. The imbibition rate and residual oil saturation in small pores are higher than the larger ones. Due to the unbalanced force at pore throats, a micromodel with a high coordination number has lower residual oil saturation. Besides, the lower residual oil saturation is obtained by adding the LNF. This paper provides a micro-visual method to understand the imbibition process under different wettability and pore structures in fossil hydrogen reservoirs.

Application of graphene oxide IoNanofluid as a superior heat transfer fluid in concentrated solar power plants

This study presents the fabrication of a highly stable Ionic liquid nanofluid (IoNanofluid) without any surfactant application by dispersing 0.5%, 1% and 2% mass fractions of functionalized graphene oxide (GO) nanoparticles in 1-butyl-3-methylimidazolium-bis(trifluoromethylsulfonyl)imide ([Bmim][NTf2]). Various analyses were employed to investigate the chemical structure and morphology of the synthesized nanoparticles. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) results were taken into account to assess the stability of IoNanofluid. Thermophysical properties of the IoNanofluid including density, viscosity, thermal conductivity and specific heat capacity were measured experimentally, and compared with the base fluid's experimental data. The results showed the dramatic improvement of thermal conductivity and specific heat capacity of up to 6.5% and 27%, respectively. Therefore, application of the prepared IoNanofluid in concentrated solar power (CSP) plants as heat transfer fluid (HTF) could lead to enhancement of the overall efficiency of the system. Accordingly, in order to estimate the heat transfer performance of IoNanofluid, Dittus-Boelter, the correlation commonly used for turbulent flow was applied. Compared to the base fluid, the maximum heat transfer coefficient enhancement was 7.2% via application of 0.5% mass fraction of GO nanoparticles. Thus, it seems that GO IoNanofluid at low mass fractions has desirable advantages for using as HTF in CSP plants.

Integrated hydraulic fracturing techniques to enhance oil recovery from tight rocks

Two main challenges exist in enhancing oil recovery rate from tight oil reservoirs, namely how to create an effective complicated fracture network and how to enhance the imbibition effect of fracturing fluid. In response to the challenges, through modeling experiment in laboratory and evaluation of field application results, a set of integrated efficient fracturing and enhanced oil recovery (EOR) techniques suitable for tight oil development in China has been proposed. (1) Fracturing with temporary plugging agents to realize stimulation in multiple clusters, to form dense fracture network, and thus maximizing the drainage area; (2) Supporting induced fractures with micro-sized proppants during the prepad fluid fracture-making stage, to generate dense fracture network with high conductivity; (3) Using the liquid nanofluid as a fracturing fluid additive to increase oil-water displacement ratio and take advantage of the massive injected fracturing fluid and maximize the oil production after hydraulic fracturing.

Numerical study of entropy generation and natural convection heat transfer in trapezoidal enclosure with a thin baffle attached to inner wall using liquid nanofluid

Numerical study of entropy generation and natural convection heat transfer in trapezoidal enclosure with a thin baffle attached to inner wall using liquid nanofluid

Heat transfer analysis of Prandtl liquid nanofluid in the presence of homogeneous-heterogeneous reactions

Abstract The objective of present research work is to analyze the homogeneous-heterogeneous reactions on the MHD two-dimensional stagnation-point flow of non-Newtonian Prandtl fluid flow and heat transfer towards horizontal linear stretching sheet. The governing boundary layer equations using similarity transformation are reduced to ordinary differential equations suitable to be solved using Finite Difference Method. The quantities of interests are thoroughly analyzed under the effects of various emerging parameters. Comparison of the results obtained from limiting case of present model with already existing literature is in good agreement which shows the validity of the present numerical solution. The study concludes that homogeneous and heterogeneous reaction strength decreases the heat transfer rate. On the other hand, Prandtl fluid parameter and elastic parameter increases heat transfer rate.

Evaluation of liquid nanofluid as fracturing fluid additive on enhanced oil recovery from low-permeability reservoirs

Hydraulic fracturing creates a complex fracture network that makes the oil production from low-permeability reservoirs economical. However, significant amount of water is likely lost into the rock matrix during hydraulic fracturing. This can cause formation damage due to multiphase flow, thus hindering the oil production rate. Surfactants can alter rock wettability and/or reduce oil-water interfacial tension (IFT), and it has been proposed to be used to mitigate such water blockage and enhance oil recovery. Among different approaches of using surfactants, forming liquid nanofluid (LNF) can minimize the adsorption of surfactants on rock surface, and it is likely to be one of the best options for low-permeability rocks with extensive surface area. In this study, the key properties of a well-screened LNF are evaluated, and then compared with a commercial flowback surfactant (CFS) that is widely used in the field. Pressure transmission test is further applied, which can determine the change of rock permeability due to different fluids and the potential formation damage due to multiphase flow. A systematic evaluation method is thus established to screen fracturing fluid additives to enhance oil production from low-permeability reservoirs both effectively and efficiently.

Natural convection heat transfer utilizing ionic nanofluids with temperature-dependent thermophysical properties

Ionic liquid based nanofluids are a very new and novel class of fluids used for heat transfer. The thermophysical properties of these new fluids are extremely encouraging in comparison to base ionic liquids and recommend these new fluids for solar applications. This paper deals with a numerical implementation of an ionic liquid nanofluid in a square enclosure considering two heating situations; bottom heating and lateral heating of the enclosure. Comparison with a regular alumina nanofluid in terms of Nusselt number is inserted. Thermophysical properties of these Ionic liquid based nanofluids were considered variable with temperature and the numerical results are correlated asa function of Ra and volume concentration (ϕ) for the two studied cases in the range of 104≤Ra≤106 and 0%≤ϕ≤2.5%. As an overall conclusion, this innovative class of heat transfer fluids reveals great potential in advanced heat transfer applications.

An investigation into the thermophysical and optical properties of SiC/ionic liquid nanofluid for direct absorption solar collector

The ionic liquids (ILs) as heat transfer fluids (HTFs) are limited for lack of strong ability in absorption of sunlight. Hence, nanoparticles are added in pure ILs to improve their thermal and optical properties. In this study, a highly stable ionic liquid nanofluid (Ionanofluid) was first prepared by dispersing SiC nanoparticles in [HMIM]BF4 and their thermophysical and optical properties were thoroughly investigated as HTFs application in direct absorption solar collectors (DACs). An enhancement in thermal properties in Ionanofluids was observed. 0.06wt% SiC Ionanofluids could increase the TC and specific heat of pure [HMIM]BF4 about 10.2% and 5% at 25°C, respectively. With the increase of temperature, the thermal properties increase, while the viscosity and density decreased. It was indicated that SiC Ionanofluids were more suitable in medium-high temperature application. Additionally the results of optical properties showed that SiC Ionanofluids were a superior solar absorption material, where the extinction coefficient of 0.03wt% SiC Ionanofluids could increase about 5.8cm−1. In summary, the advantageous performance ensured the potential of SiC Ionanofluids as advanced HTFs in solar energy system. We believed that this information have guide meaning to the practical design of DAC system.

A combined numerical and experimental study on graphene/ionic liquid nanofluid based direct absorption solar collector

Novel heat transfer fluids with very low vapor pressure and high thermal stability are highly desirable for both high temperature direct solar collectors and concentrated solar collector. Herein a combined analytical and experimental study has been conducted on high temperature direct solar thermal collectors using graphene/ionic liquid nanofluids as the absorbers. A one-dimensional transient heat transfer model has been used to predict the receiver temperature and efficiency with varying parameters such as solar and graphene concentration and receiver height. The results show that the experimental temperature is in good agreement with numerical results under the same conditions. Based on the model, it is shown that the receiver efficiency increases with the solar concentration and receiver height, but decreases with the graphene concentration. The receiver efficiency could be maintained 0.7 under the conditions of 0.0005wt% of graphene in 5cm receiver under 20×1000Wm−2 at 600K. This work provided an important perspective to the graphene/ionic liquid nanofluids for use as a kind of novel heat transfer fluid in direct solar thermal collectors under concentrated solar incident radiation.

Molecular Dynamics Simulation of Heat Transfer during Quenching in CNT Nanofluids

Abstract Nanofluids exhibit superior thermal properties to conventional fluid and particle-fluid suspensions and show a great potential as quenching media for quench hardening of steel components. The heat transfer mechanism in nanofluid is very complex and unclear. In this paper, molecular dynamics (MD) simulation method is used to theoretically study the heat transfer from a metal surface at different temperatures to a water-based nanofluid with functionalized carbon nanotubes (FCNTs). To model the quenching process, an initial temperature jump between the nanofluid and an iron slab is employed, and non-equilibrium molecular dynamics (NEMD) simulations are performed. The MD results reveal the heat transfer process in the initial stage of quenching and at the first moment of contact of a liquid nanofluid with a hot metal surface. The thermodynamics and transport properties of the nanofluid and the heat transfer characteristics are discussed with the atomistic details of the interactions of the FCNT with the iron atoms and the water molecules.

Laminar nanofluid flow in microheat-sinks

In response to the ever increasing demand for smaller and lighter high-performance cooling devices, steady laminar liquid nanofluid flow in microchannels is simulated and analyzed. Considering two types of nanofluids, i.e., copper-oxide nanospheres at low volume concentrations in water or ethylene glycol, the conjugated heat transfer problem for microheat-sinks has been numerically solved. Employing new models for the effective thermal conductivity and dynamic viscosity of nanofluids, the impact of nanoparticle concentrations in these two mixture flows on the microchannel pressure gradients, temperature profiles and Nusselt numbers are computed, in light of aspect ratio, viscous dissipation, and enhanced temperature effects. Based on these results, the following can be recommended for microheat-sink performance improvements: Use of large high-Prandtl number carrier fluids, nanoparticles at high volume concentrations of about 4% with elevated thermal conductivities and dielectric constants very close to that of the carrier fluid, microchannels with high aspect ratios, and treated channel walls to avoid nanoparticle accumulation.