Water-based Fluids Research Articles

An impact of Richardson number on the inclined MHD mixed convective flow with heat and mass transfer

AbstractThe two‐dimensional mixed convective MHD flow with heat and mass transfer is investigated for its behavior with Dufour and Soret mechanisms over the porous sheet. The copper–alumina (Cu–Al2O3) hybrid nanoparticles are used in the base fluid water. The governing system of partial differential equations is converted into a system of ordinary differential equations via similarity transformations, obtaining the solution for velocity, temperature, and concentration fields in exponential form. The problem is demonstrated in the Darcy–Brinkman model, the impact of included parameters such as Richardson number, magnetic field, and Dufour numbers are studied for the obtained solution with the help of graphs. Increasing the magnetic field decreases both transverse and axial velocity profiles. Increasing the magnetic field and Richardson's number decreases the solution (Al2O3–H2O). Increasing the values magnetic field and Richardson's number decreases both transverse and axial velocity profiles. Increasing the values of the Dufour effect increases the axial and transverse velocity boundary layer. The magnetohydrodynamic hybrid nanofluid flow over porous media works efficiently in liquid cooling and, therefore, has significant applications in industrial heating and cooling systems, solar energy, magnetohydrodynamic flow meters and pumps, manufacturing, regenerative heat exchange, thermal energy storage, solar power collectors, geothermal recovery, and chemical catalytic reactors.

A State of the Art on Sustainable Metal Working Fluids in Machining Applications

Metalworking fluids (MWFs) play a crucial role in machining processes by lubricating and cooling cutting tools, reducing friction, and improving overall machining efficiency. These fluids can be classified into various types, including cutting oils, water-based fluids, and semi-synthetic or synthetic fluids. Cutting oils are often mineral-based, providing excellent lubrication in heavy-duty applications. Water-based fluids, on the other hand, are more environmentally friendly and commonly used in light to moderate machining operations. Semi-synthetic and synthetic fluids offer a balance between performance and eco-friendliness, incorporating additives to enhance their properties. Proper selection and management of MWFs are essential for optimizing tool life, surface finish, and overall productivity in metal machining applications. Research has shown that the cost of cutting fluid in machining constitutes 17% of the total production cost. In the same research, it was stated that the cutting tool cost was around 4%. This review provides an overview of the current advancements in sustainable MWFs within machining applications. It explores state-of-the-art technologies, formulations, and practices aimed at minimizing environmental impact while maintaining optimal performance in metalworking processes. The review encompasses eco-friendly additives, recycling methods, and emerging trends in the development of MWFs, emphasizing the importance of sustainable practices in the manufacturing industry.

Further Investigation of CO2 Quasi-Dry Fracturing in Shale Reservoirs—An Experimental Study

The physical properties of shale reservoirs are typically poor, necessitating the use of fracturing technology for effective development. However, the high clay content prevalent in shale formations poses significant challenges for conventional hydraulic fracturing methods. To address this issue, CO2-based fracturing fluid has been proposed as an alternative to mitigate the damage caused by water-based fracturing fluids. In this paper, the applicability of quasi-dry CO2 fracturing in shale reservoirs is examined from three key perspectives: the viscosity of CO2 fracturing fluid, the fracture characteristics induced by the CO2 fracture fluid, and the potential reservoir damage caused by the fracturing fluid. Firstly, the viscosity of CO2 fracturing fluid was determined by a rheological experiment. Rheological tests revealed that the viscosity of CO2 fracturing fluid was significantly influenced by the water–carbon ratio. Specifically, when the water–carbon ratio was 30:70, the maximum viscosity observed could reach 104 mPa·s. Moreover, increasing reservoir temperature resulted in decreased fracturing fluid viscosity, with a 40 °C temperature rise causing a 20% viscosity reduction. Secondly, matrix permeability tests were conducted to investigate permeability alteration during CO2 fracturing fluid invasion. Due to the weak acidity of CO2-based fracturing fluid, the permeability reduction induced by clay hydration was inhibited, and an increase in permeability was observed after a 3-day duration. However, the matrix permeability tends to decrease as the interaction time is prolonged, which means prolonged soaking time can still cause formation damage. Finally, triaxial fracturing experiments facilitated by a three-axis servo pressure device were conducted. The fracture properties were characterized using computed tomography (CT), and 3D reconstruction of fractured samples was conducted based on the CT data. The results demonstrate that CO2 fracturing fluid effectively activates weak cementation surfaces in the rock, promoting the formation of larger and more complex fractures. Hence, CO2 quasi-dry fracturing technology emerges as a method with significant potential, capable of efficiently stimulating shale reservoirs, although a reasonable soaking time is necessary to maximize hydrocarbon production.

Computational study of aspect ratio and undulation effect on natural convection in an inverted T-shaped porous enclosure

This numerical study aims to enhance the convective thermal and fluid flow characteristics in an inverted T-shaped porous enclosure saturated with a water-based special fluid. Moreover, a Darcy-extended Brinkman-Forchheimer-based mathematical model is numerically simulated with a penalty finite element approach to analyze the influence of aspect ratio and undulation effect on the developed mathematical model. Firstly, the various aspect ratios ( Ar = 0.25 , 0.50 , and 0.75 ) of the mathematical model are numerically simulated at the varying range of Rayleigh number (Ra), which reveals that the increasing aspect ratios reinforce the convective heat and fluid flow phenomena. Moreover, it confirms the most pertinent aspect ratios (Ar = 0.50) that get superior results in reinforcing the convective flow among other aspect ratios. Furthermore, the optimal aspect ratio (Ar = 0.50) is further fixed to explore the parametric influences, including Rayleigh number ( Ra = 10 3 − 10 6 ), porosity value ( ϵ = 0.1 − 0.9 ), Darcy number ( Da = 10 − 5 − 10 − 2 ), and various undulation parameters such wave number ( n a = 5 , 9 , 15 ) and amplitude of wavy surface ( a = 0 , 0.050 , 0.125 , 0.250 ). The results reveal that augmenting Ra, Da, and ϵ reinforces the convective thermal and fluid transport characteristics. Moreover, a combined effect of undulation factors ( n a , a ) is also reported, indicating that decreasing na and increasing a magnitude strengthen the natural convection process. It is analyzed that the optimal combination of undulation parameters ( n a = 5 , a = 0.25 ) results in a 16.15% in heat transfer enhancement. Additionally, maximum enhancements of 32.55%, 6.63%, and 41.47% in Num are reported while comparing between na = 5 and na = 15 for Ra, Da, and ϵ. Similarly, maximum enhancements of 17.87%, 16.10%, and 37.77% in Num are reported when comparing between a = 0.05 with a = 0.25 for Ra, Da, and ϵ. The research contributes valuable insights into improving thermal transport processes in real-world applications, especially in industrial solar power collectors, thermal exchangers, and heat storage industries that utilize the T-shaped configuration.

A Comprehensive Review of Screen Plugging during Openhole Sand Control Completions Installation: Causes, Consequences, and Best Practices

Summary In openhole completions, screens are one of the very common equipment used to control production of solids. Screens could get plugged during installation in case of improper wellbore fluid conditioning and displacement. Awareness of screen plugging is not widely spread, and many practicing engineers do not pay enough attention to its implications. In this paper, we discuss the causes, consequences, and ways of determining plugging and recommend best practices to reduce the risk of screen plugging. First, we review the various reasons for screens to get plugged during openhole completion installations and explain in detail undesirable events caused by screen plugging such as: Inability to properly displace wellbore fluids Inability to fully pack the screen annulus Damage to screens during displacement and gravel packing We also review downhole gauge data of several jobs to identify and discuss screen plugging signatures and their outcomes. Additionally, we discuss potential preventive measures. In openhole completions, it is very common to run screens in wellbores containing solids-laden fluids intentionally or unintentionally. Poor wellbore displacement or improper fluid conditioning can result in leaving some bigger size solids in the screen-running fluid (SRF), which could plug the screens. Also, the exposure of reactive shales to water-based fluids can destabilize the shales and lead to plugging. In some cases, the SRF quality control is not properly accounting for the actual flow inside the screen while running in hole, resulting in a false pass. We present several case histories of downhole gauge data analysis, showing evidence of screen plugging leading to excessive treating pressure, incomplete gravel pack, and, in a few cases, screen erosion during gravel pack operations. To prevent screen plugging, it is necessary to properly model all the displacement stages, pay attention to proper conditioning and quality control of the fluid, and ensure compatibility of the fluids with shales. A comprehensive review of screen plugging during sand control installation phase and its potential consequences supported with extensive downhole gauge data has not been published previously. This paper will be a valuable source of knowledge for completion engineers and help them better design and execute future operations.

Experimental Analysis of Nanofluids in PEMFC Cooling Plate Integrated with Thermoelectric Generator

A thermoelectric generator (TEG) is considered a feasible option to recover waste heat from a Proton exchange membrane fuel cell (PEMFC) into electrical energy. However, its application is limited due to its low efficiency. Meanwhile, nanofluids have emerged as an alternative coolant in heat transfer due to their superior thermal conductivity characteristics. Thus, this study aims to improve the efficiency of the TEG using nanofluids. The experimental study was conducted on a test bench that coupled a PEMFC cooling plate and TEG which was subjected to a 0.5% volume concentration of 𝐴𝑙2𝑂3∶𝑆𝑖𝑂2 hybrid nanofluids at a flow rate of Re 300 to 1000. The mixture ratio of 𝐴𝑙2𝑂3∶𝑆𝑖𝑂2 hybrid nanofluids studied was 10:90 ratio, single nanofluids of 𝐴𝑙2𝑂3 and 𝑆𝑖𝑂2 and also the base fluid of water. Upon completion, the improvement in power output due to an improved temperature difference of the thermoelectric generator (TEG) is observed. The highest TEG performance was shown by hybrid nanofluids of 10:90 (𝐴𝑙2𝑂3∶𝑆𝑖𝑂2) with a 17% improvement as compared to the base fluid of water. This is due to the bigger temperature difference which is caused by better thermal conductivity of hybrid nanofluids as compared to the base fluid.

Aqueous Theta-Phase Aluminum Oxide Nanofluid for Energy Applications: Experimental Study on Thermal Conductivity

The use of nanofluids in energy systems allows for increasing efficiency and developing more economic systems. Alumina-water is one of the most common nanofluids used but little information is available about the aqueous theta-phase aluminum oxide. Given the lack of thermal conductivity data for this nanofluid, in this research, this property is experimentally evaluated. Nanofluid is prepared using the two-step method, employing a magnetic stirrer and a sonication bath. A high-precision sensor is employed for measuring thermal conductivity, using the method of transient hot wire. The thermal conductivity measurements for the base fluid (water) are compared with data provided by NIST. Nanoparticle mass fraction in the nanofluid is increased from 1 to 10% and the temperature from 22.1 to 59.3 °C. Three sonication times (1.5, 4 and 16.5 h) are used. A strong dependence between the thermal conductivity and the temperature and nanoparticles concentration has been found, while the sonication time has a negligible influence on the thermal conductivity in the range of times tested. A correlation to obtain the thermal conductivity of the water-based nanofluid using theta-phase aluminum oxide has been developed, including nanoparticle volume concentration and temperature. An excellent agreement is obtained between predicted and experimental data.

Impact of length and radius of carbon nanotubes on flow and heat transfer in converging and diverging channels with entropy generation

This research examines the complex interplay between the carbon nanotubes' length and radius and how that affects flow patterns, heat transfer properties, and entropy creation in both convergent and divergent channels. Our research elucidates the mechanisms at play by revealing a crucial link between carbon nanotube dimensions and the efficacy of heat transfer processes. In particular, carbon nanotubes with a longer length have better heat transmission properties, while carbon nanotubes with a smaller radius generate less entropy. From microfluidics to energy-efficient materials, these results show significant promise for optimizing thermal systems and improving performance. This research looks on the differences between the thermal transports of single- and multi-walled carbon nanotubes in water. Thermo physical characteristics of carbon nanoparticles are one of a kind and essential for this purpose. The fluid is assumed to be incompressible and to flow steadily a two-dimensional plane. The effects of thermal radiation on the heat transfer of a water-based fluid in convergent and divergent channels with decreasing and expanding walls have been studied. In order to quickly sketch the equations, the RK-4 method with shooting approach is used, and similarity transformation is employed to reduce their dimensionality. The key factors influencing hydrothermal performance have been visualized through the use of graphs. The production numbers of entropy are also shown and explained at length. The obtained data supports the reliability of the approach used. Surface heat transport was found to be negatively impacted by elongation. Colloidal single-walled carbon nanotube (SWCNT) suspensions in water had higher thermal conductivity than water itself.

Heat transfer model analysis of fractional Jeffery-type hybrid nanofluid dripping through a poured microchannel

This study investigates the impact of coupled heat and mass transfer on the peristaltic migration of a magnetohydrodynamic (MHD) stress-strain Jeffery-type hybrid nanofluid flowing through an inclined asymmetric micro-channel with a porous medium. The fundamental two-dimensional momentum and energy transport equations are simplified under the assumptions of long wavelength and low Reynolds number. To solve the momentum and heat transfer problems, two advanced fractional derivative approaches are employed: the fractal integral and the Prabhakar fractional derivative. The pressure difference is determined using numerical integration techniques, such as the Stehfest and Tzou's algorithms. The results are presented through graphs and tables, which illustrate the effects of various parameters on the velocity, heat transfer, and trapping phenomena. As a result, we concluded that, pressure gradients grow with higher Reynolds numbers and channel-inclined angles. The heat transfer rate is observed to decrease as the Darcy number and the orientation of the electromagnetic field increase. When comparing the fractional derivative approaches, the fractal operator exhibits a more significant impact on the momentum profiles compared to the Prabhakar fractional operator. This difference is attributed to the distinct characteristics of the integral kernels associated with each fractional derivative definition. Furthermore, when comparing hybrid nanofluids, water-based (H2O + Ag + TiO2) hybrid fluids have a somewhat more significant effect than (C6H9NaO7 + Ag + TiO2) hybrid nanofluids.

Thermal analysis for SWCNTs and MWCTs due to coaxially stretchable disks with applications of viscous dissipation and thermal radiation: Artificial neural network analysis

Owing to exclusive thermal prospective of nanoparticles, diverse applications of such materials have been reported in heat transfer systems. The carbon nanotube (CNTs) is the modified class of nanoparticles which is preserve more stable thermal properties. The decomposition of CNTs with base materials offer special applications in enhancing thermal efficiency of energy systems, nuclear processes, sensors, diagnostic imaging etc. Following to such motivations in mind, the objective of current work is to present artificial neural network analysis for heat transfer problem due to suspension of carbon nanotubes-based nanofluid. Both single-walled and multi-walled carbon nanotubes are utilized to analyse the thermal impact of water base fluid. The source of flow is coaxially stretchable disks. The applications of porous medium phenomenon are reported to inspect the inertial effects. The problem is further updated by utilizing the radiative phenomenon, external heat generation and dissipation and slip constraints. The transport system is expressed via coupled nonlinear equations which are tackled via numerical computations.

Enhancement of solar evacuated tube unit filled with nanofluid implementing three lobed storage unit equipped with fins

This study discusses an evacuated tube collector-type solar water heater (ETCSWH) using a phase change material (PCM) chamber with fins, nanofluid, and nano-enhanced phase change material (NEPCM). First, the charging phenomena in a horizontal triplex tube heat exchanger (TTHX) equipped with fins, natural convection, and an ETCSWH system without PCM is simulated to validate the solution. The impact of adding fins and nanoparticles with a volume fraction of 3% of Al2O3 and Cu to paraffin wax and water-based fluid, respectively, on the unit's efficiency has been examined. The proposed system for the PCM melting process, heat storage, fluid flow behavior in the system, and velocity distribution and temperature contour in the storage tank and three parts of the absorber tube have been evaluated using ANSYS FLUENT software in a three-dimensional and transient simulation. The results show that Case 8 has improved by 39.7% compared to Case 1 and Case 4 by 5.2% compared to Case 1 within 4 h of the melting process. Also, Case 8 with a 43% and 6.4% shorter melting time than Cases 1 and 5 has the best performance and the greatest heat transfer rate. The productivity of the ETCSWH system is considerably enhanced by the use of fins, NEPCM, and nanofluid.

Micropolar (copper–water) nanofluid flow past a stretching sheet with nanosized particles shape impact

Nanosized particles can be administered via distinct routes involving intraperitoneal and intravenous injection, pulmonary inhalation, and oral administration. Nanosized particles have been advanced as efficient target-specific strategies for the treatment of cancer, acting as agents and also acting as nanocarriers. Over the last few years, various kinds of nanosized particles have been developed based on several components involving silica oxides, nanocrystals, carbon, metal oxides, polymers, quantum dots, lipids, and dendrimers, together with enhancing a variety of newly developed materials. The focus of this study is to analyze the effect of dissimilar shapes of nano-sized particles on fluid flow past a stretching surface that is permeable. For this purpose, a micropolar nanofluid with a base fluid of water is considered. Both spherical (sphere) and nonspherical (lamina)-shaped nanoparticles of copper are used to study the enhancement of thermal conductivity. The highly complex governing partial differential equations of the problem are converted into ODEs via similarity transformations. The converted ODEs are tackled with the help of the homotopy analysis method. Our study shows that the performance of nonspherical(lamina) nanoparticles is better than spherical(sphere) nanoparticles in the disturbance of fluid motion, microrotation, and energy.

Neural network architecture to optimize the nanoscale thermal transport of ternary magnetized Carreau nanofluid over 3D wedge

SignificanceIncorporation of nanoparticles in base fluid water is significant for analysis of thermal behavior of nanofluid mixtures, which has various applications in materials science and thermal engineering, and supervised neural scheme predicts the thermal behavior by solving Carreau nanofluid model. MotiveThis article brings the investigation related to prediction of thermal transport of a ternary magnetized hybrid nanofluid [(Al2O3, CuO, TiO2)/H2O] with a three-dimensional Carreau nanofluid model over a wedge. Three nanoparticles dispersed in water (H2O). Inclined magnetic field is considered for judgement of velocity profile and thermal radiation is utilized to scrutinize the temperature distribution of nanofluid. The Carreau mathematical model is chosen to depict the rheological characteristics of non-Newtonian fluids at very high and very low shear rate. MethodologyPhysical assumptions creates the system of Partial differential equations (PDEs) and these are converted into ordinary differential equations (ODEs) by similarity tool. Further ODEs are dealt with bvp4c scheme and further prediction of solution is made by Levenberg-Marquardt neural network (LM-NN) supervised neural scheme. FindingsIncreased volume friction coefficients of nanoparticles increases the transport of heat. High inclined magnetic effect, thermal radiation, pressure gradient and shear strain parameter predict higher thermal transport.

Effects of nanoparticle shape factor on radiative ternary hybrid nanofluid flow over a wedge in presence of induced magnetic field

PurposeSeveral graphs, streamlines, isotherms and 3D plots are illustrated to enlighten the noteworthy fallouts of the investigation. Embedding flow factors for velocity, induced magnetic field and temperature have been determined using parametric analysis.Design/methodology/approachTernary hybrid nanofluids has outstanding hydrothermal performance compared to classical mono nanofluids and hybrid nanofluids owing to the presence of triple tiny metallic particles. Ternary hybrid nanofluids are considered as most promising candidates in solar energy, heat exchangers, electronics cooling, automotive cooling, nuclear reactors, automobile, aerospace, biomedical devices, food processing etc. In this work, a ternary hybrid nanofluid flow that contains metallic nanoparticles over a wedge under the prevalence of solar radiating heat, induced magnetic field and the shape factor of nanoparticles is considered. A ternary hybrid nanofluid is synthesized by dispersing iron oxide (Fe3O4), silver (Ag) and magnesium oxide (MgO) nanoparticles in a water (H2O) base fluid. By employing similarity transformations, we can convert the governing equations into ordinary differential equations and then solve numerically by using the Runge–Kutta–Fehlberg approach.FindingsThere is no fund for the research work.Social implicationsThis kind of study may be used to improve the performance of solar collectors, solar energy and solar cells.Originality/valueThis investigation unfolds the hydrothermal changes of radiative water-based Fe3O4-Ag-MgO-H2O ternary hybrid nanofluidic transport past a static and moving wedge in the presence of solar radiating heating and induced magnetic fields. The shape factor of nanoparticles has been considered in this study.

Thermal Performance Analysis of an Indirect Solar Cooker Using a Graphene Oxide Nanofluid

Solar energy has become an energy source for a wide range of uses, including in solar cookers, due to its availability, cleanliness, environmental friendliness, and sustainability. In this study, an indirect solar cooker was investigated by measuring its thermal performance using a Graphene Oxide (GO) nanofluid. Water, GO (250 ppm)-water, and GO (500 ppm)-water were used as heat transfer fluids. The experimental set-up consisted of the cooking part and a solar collector, which are the two essential elements in indirect solar cookers. The cooking part was a wooden box solar cooker, and the parabolic trough solar collector was a polished stainless steel structure. The solar cooker was assessed using the stagnation test and load test as well as energy and exergy measurements. According to the test results, the averaged F1 was 0.1 for the base fluid water, 0.11 for GO (250 ppm)-water, and 0.13 for GO (500 ppm)-water. In addition, using a GO nanofluid instead of water in the solar cooker, the system’s thermal performance, energy, and exergy efficiency were improved. The use of the GO (250 ppm)-water and GO (500 ppm)-water nanofluids instead of water in the system improved the overall energy efficiency of the system by 3.3 and 4.2%. Moreover, using GO (500 ppm)-water allowed for achieving superior performance.

Synergistic Effect of Carbon Nanotubes, Zinc, and Copper Oxides on Rheological Properties of Fracturing Fluid: A Comparative Study

Nanomaterials play a beneficial role in enhancing the rheological behavior of fracturing (frac) fluid by reacting with intermolecular structures. The inclusion of these materials into the fluid improves its stability, increases the viscosity of polymers, and enhances its resistance to high temperature and pressure. In this investigation, multi-walled carbon nanotubes (CNTs), nano-zinc oxides (N-ZnO), and nano-copper oxides (N-CuO) have been utilized to ameliorate the rheological properties of water-based fracturing fluid. Different concentrations of these aforementioned nanomaterials were prepared to determine their effects on the rheological behavior of the fluid. The results revealed that the size of nanoparticles ranged from 10 to 500 nm, 300 nm, and 295 nm for CNTs, N-ZnO, and N-CuO, respectively. Moreover, employing CNTs exhibited a resistance of 550 cp at 25 °C and reached 360 cp at 50 °C with a CNT concentration of 0.5 g/L. In contrast, N-CuO and N-ZnO showed a resistance of 206 cp at 25 °C and significantly decreased to 17 cp and 16 cp with higher concentrations of 10 g/L and 1 g/L, respectively. Based on these findings, this study recommends utilizing CNTs to enhance fracking fluid’s chemical and physical properties, which need to be highly viscous and stable under reservoir conditions.

Tribological performance of fatty acid ammonium ionic liquids as anti-wear additives in water-based fluids

In this study, we synthesized eight water-soluble ionic liquids (ILs) and investigated their tribological performance as additives in water-diethylene glycol (WDG) base fluids. The results of the tribological test suggested that these ILs additives demonstrate promising capabilities in friction reduction and anti-wear for water lubricated contacts. The ILs with the longest carboxylic chain length, namely C10MIPA and C10DIPA in this work, displayed superior tribological performances. Observations on the abraded surfaces showed that the IL forms a monolayer adsorption through self-assembly, and upon rubbing it creates a continuous and stable tribo-film with an uneven thickness of 30–60 nm through tribo-chemical reactions. The tribo-film mainly consists of iron oxides. The proposed lubrication mechanisms include adsorbed film and formed tribo-films, which work effectively to reduce the shear stress and thus sliding friction.

MHD radiative Gr-Ag-TiO2/H2O ternary hybrid nanofluid flow upon a permeable movable wedge with irreversibility analysis

ABSTRACT The mass-based ternary hybrid nanofluid model is applied for the magnetohydrodynamic (MHD) flow over a moving wedge with wall permeability, thermal radiation, and convective boundary condition. The masses of the nanoparticles and the base fluid are considered instead of the volumetric concentration of the first, the second, and the third nanoparticles. In the base fluid of water, three types of nanoparticles such as titania, silver, and graphene have been embedded. A similarity method is used to reduce variables and also to turn prominent equations of ternary hybrid nanofluid flow into a simplified form. The shooting technique with the Runge-Kutta-Felhberg method has been used to numerically solve the converted boundary layer equations. The largest Nusselt number is related to the ternary hybrid nanofluid, in which a heat transfer enhancement of 6.55% has been obtained in comparison with regular fluid. The Nusselt number for five shapes of the third nanoparticles is obtained (when both the first and second nanoparticles are spherical), and when the third nanoparticle has the shape of the disk, the most heat transfer has occurred. The highest entropy generation is related to the stagnation point case (m = 1) and the lowest belongs t the downhill case (m = –0.0825).

Ionic liquid as a cosurfactant for critical heat flux enhancement during boiling with aqueous surfactant solutions

Surfactants are often used to improve boiling heat transfer due to the ease of their implementation. While aqueous surfactant solution significantly increases the heat transfer coefficient (HTC), it is known to deteriorate the critical heat flux (CHF) relative to the base fluid water. The high foamability of most surfactant solutions causes vapor crowding on the heater surface, making surface modification techniques ineffective for CHF enhancement. Here, we address the issue of relative degradation of CHF due to surfactant by using an ionic liquid as a cosurfactant. We employ a unique boiling fluid, where 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]), a low-foaming ionic liquid, is introduced as a co-surfactant in aqueous sodium dodecyl sulfate (SDS) solution. Motivated by the synergistic increase in foamability of the aqueous surfactant solution due to the addition of ionic liquid, we examine the boiling performance at various combinations of concentrations of the two additives in the solution. The mixture consistently exhibits higher CHF and HTC than an SDS only solution, with the best enhancement observed for a mixture of ≈ 30 ppm SDS and ≈ 750 ppm [C2mim][Cl], resulting in ≈1.6× and ≈1.5× enhancements in CHF and HTC, respectively, compared to the SDS only solution (≈ 30 ppm). We next fine-tune the concentration of cosurfactant to demonstrate an exceptionally high HTC of ≈93 kW/(m2 – ℃) with a CHF value comparable to that of pure water. Enhanced foamability and in-situ improvement in the wettability of the heater surface enhance the HTC and the CHF, respectively. This facile technique for enhancing HTC with water as the base fluid, without compromising on CHF, holds promise for high heat flux thermal management applications.

Promotion of CO2 fracturing for CCUS—the technical gap between theory and practice

CO2, used as an environmentally friendly fracturing fluid, has encountered a bottleneck in development in recent years. Despite great efforts in research work, limited progress has been made in field applications. In this study, an extensive literature review of research work and field cases was performed to summarize the technical issues and challenges of CO2 fracturing. The key issues of CO2 fracturing were analyzed to reveal the gap between fundamental research and field operations. The effects of CO2 properties on fracture creation and proppant transport were synthetically analyzed to extract new common research orientations, with the aim of improving the efficiency of CO2 injection. The hydraulic parameters of CO2 fracturing were compared with those of water-based fracturing fluids, which revealed a theory-practice gap. By studying the developing trends and successful experiences of conventional fluids, new strategies for CO2 fracturing were proposed. We identified that the major theory-practice gap in CO2 fracturing exists in pump rate and operation scale. Consequently, the friction reducer, effects of flow loss (due to leak-off) and distribution (within fracture networks), and shear viscosity of thickened CO2 are key factors in improving both fracture propagation and proppant transport. By increasing the scale of injected CO2, the CO2 fracturing technique can be enhanced, making it an essential option for carbon capture, utilization, and storage (CCUS) to reduce carbon emissions and mitigate climate change.