Conventional Fluid Research Articles

Maximizing heat transfer and minimizing entropy generation in concentric cylinders with CuO[sbnd]MgO[sbnd]TiO2 nanoparticles

Heat transfer is crucial because it has industrial uses. A novel type of nanofluids dubbed “ternary nanofluid” is being utilized to boost the ability of conventional fluids to transmit heat since it has a greater heat transfer capacity than solo and hybrid nanofluids. This work investigates the heat transfer capabilities and entropy generation in the cylindrical flow of a ternary nanofluid in the presence of a magnetic field. Minimizing the entropy generation and maximizing the heat transfer of a fluid using ternary nanoparticles (CuOMgOTiO2) is the aim of this work. The finite difference method is used by the MATLAB computer program to solve the problem numerically. The results reveal that the entropy generation minimizes in the presence of CuOMgOTiO2. The heat transfer rate of the fluid increased by 9.9%, 10.8%, and 11.2% on adding TiO2, MgOTiO2, and CuOMgOTiO2 nanoparticles, respectively.

Implicit finite difference simulation of non-similar conduction–convection interaction of magnetohydrodynamics water-Cu nanofluid flow along a vertical surface

Heat-exchanging devices equipped with conventional thermal fluids are failing to meet the standard in terms of thermal efficiency. The inclusion of nanoparticles within a base fluid to improve thermal efficiency can be a great alternative but a proper understanding on the interactions during the heat transfer phenomena is required. This work examines the interactions between conduction and convection in a nanofluid of water and copper (Cu) particles. The investigation focuses on the behavior of the nanofluid, considering the impact of magnetohydrodynamics (MHDs) flow over a vertical surface. The governing equations were non-dimensionalized by the suitable transformation and then were solved numerically by the implicit finite difference method (FDM). The key findings suggested that increasing magnetic parameter plummeted skin friction coefficient and accelerated the heat dissipation up to by augmenting the peaks of fluid velocity as well as the temperature under a constant volume fraction of nanoparticles. In addition, the thermal boundary layer thickness also increased concurrently. Alternatively, when a constant non-zero magnetic parameter was considered, and volume fraction of nanoparticles was allowed to vary, the convective heat transfer got enhanced. The findings from this study will assist the relevant industry to identify the suitable fraction of Cu nanoparticles in the presence of magnetic field in order to achieve the best thermal efficacy of a heat-exchanging unit.

Darcy-Forchheimer flow of MHD free convective CNTs Casson nanoliquid via a cosinusoidally fluctuating heated plate

ABSTRACT This study explores the influence of carbon nanotubes (CNTs), spanwise cosinusoidally fluctuating thermal and mass diffusion on unsteady MHD free convective flow of Casson nanoliquid via an infinite hot vertical porous plate in a Darcy-Forchheimer porous medium. The overlapping grid multi-domain trivariate spectral collocation method is used to solve the non-dimensional equations. The impact of varying physical estimators on profiles alongside skin friction factor, rate of heat, and mass transport is contemplated. It was disclosed that the velocity and skin friction factors can be maximized via strong buoyancy forces and porous permeability but minimized through strong magnetic field and the Darcy–Forchheimer relation. The temperature and rate of heat transport can be increased by higher levels of heat generation, viscous dissipation, diffusion-thermo, and radiation absorption. Conversely, these factors can be minimized with higher thermal radiation. The introduction of activation energy and nonlinear chemically reactive species is responsible for the increase in species concentration and the rate of mass transport. The velocity and temperature are enhanced with increasing CNTs volume fraction, which leads to an increment in skin friction factor and thermal transport rate. Therefore, the suspension of CNTs in conventional fluids to control the coolant level in industrial apparatuses is absolutely practical.

Development and mechanistic study of hydrophobic shale inhibitors for water-based drilling fluids

Maintaining wellbore stability is a constant and hot issue in the drilling industry. The hydrophilic nature of rocks makes them susceptible to destabilization by physicochemical reactions with water-based drilling fluids. Amine-based inhibitors have been widely studied because of their effectiveness in inhibiting rock hydration. On the basis of maintaining the original inhibition mechanism of amine-based inhibitors, a hydrophobic amine-based inhibitor [(named hydrophobic organic amine (HOA)] was prepared by hydrophobically modifying the amine-based inhibitor. It has the ability to change the hydrophilicity of rocks, which is expected to further enhance the inhibition performance of amine-based inhibitors. The inhibition performance of the HOA was evaluated through experiments measuring the relative inhibition ratio, rolling recovery ratio, linear expansion rate, and water absorption rate. The performance of HOA in conventional drilling fluid systems was also systematically evaluated. HOA exhibited exceptional temperature resistance and the ability to suppress clay swelling. At an HOA dosage of 1.0%, bentonite exhibited relative inhibition ratios of 92.9% and 87.5% before and after aging at 150 °C, respectively, along with a rock fragment rolling recovery ratio of 75.1% (compared to 11.4% in pure water). The inhibition mechanism of HOA was investigated through contact angle, zeta potential, particle size distribution, and surface tension experiments. HOA had the inhibition mechanism of traditional amine-based inhibitors, that is, it could neutralize the negative charge on the surface of the clay, reduce the hydration repulsion between the clay layers, and effectively inhibit the clay hydration. Furthermore, HOA could also electrostatically adsorb onto the shale surface to form a hydrophobic layer, thereby reversing the wetting of hydrophilic rocks and reducing their water intake capacity. In addition, HOA could significantly reduce the surface tension of aqueous solutions. HOA, which can change the hydrophilicity of rocks, has better inhibition performance on rock hydration and is expected to become the next generation of amine-based inhibitors.

A review of experimental investigations to attain productive and sustainable micro-electrical discharge machining process on metals and superalloys

Purpose This study aims to understand the current production scenario emphasizing the significance of green manufacturing in achieving economic and environmental sustainability goals to fulfil future needs; to determine the viability of particular strategies and actions performed to increase the process efficiency of electrical discharge machining; and to uphold the values of sustainability in the nonconventional manufacturing sector and to identify future works in this regard. Design/methodology/approach A thorough analysis of numerous experimental studies and findings is conducted. This prominent nontraditional machining process’s potential machinability and sustainability challenges are discussed, along with the current research to alleviate them. The focus is placed on modifications to the dielectric fluid, choosing affordable substitutes and treating consumable tool electrodes. Findings Trans-esterified vegetable oils, which are biodegradable and can be used as a substitute for conventional dielectric fluids, provide pollution-free machining with enhanced surface finish and material removal rates. Modifying the dielectric fluid with specific nanomaterials could increase the machining rate and demonstrate a decrease in machining flaws such as micropores, globules and microcracks. Tool electrodes subjected to cryogenic treatment have shown reduced tool metal consumption and downtime for the setup. Practical implications The findings suggested eco-friendly machining techniques and optimized control settings that reduce energy consumption, lowering operating expenses and carbon footprints. Using eco-friendly dielectrics, including vegetable oils or biodegradable dielectric fluids, might lessen the adverse effects of the electrical discharge machine operations on the environment. Adopting sustainable practices might enhance a business’s reputation with the public, shareholders and clients because sustainability is becoming increasingly significant across various industries. Originality/value A detailed general review of green nontraditional electrical discharge machining process is provided, from high-quality indexed journals. The findings and results contemplated in this review paper can lead the research community to collectively apply it in sustainable techniques to enhance machinability and reduce environmental effects.

Low-temperature gel breaking fracturing fluid for marine hydrate reservoir fracturing and its effect on phase equilibrium of methane hydrates

Hydraulic fracturing has been proven useful for improving the gas production efficiency of low-permeability hydrate reservoirs. However, no specific fracturing fluid system exists for marine hydrate reservoirs. Applying conventional water-based fracturing fluids in low-temperature (<293.2 K) marine hydrate reservoirs can lead to difficulties in gel-breaking and hydrate instability caused by external additives. In this study, we developed two water-based fracturing fluid systems that exhibited good gel-breaking performance at low temperatures (278.2–288.2 K), one comprising ammonium persulfate (APS), ferrous sulfate (FeSO4), and citric acid (CA), the other APS and triethanolamine (TEA). In addition, we investigated the influence of crosslinking and gel-breaking reactions of the fracturing fluids on the methane hydrate phase equilibrium. The breaking time of the APS-FeSO4-CA system at 278.2K, 283.2K, and 288.2K was 30 min, 75 min, and 120 min respectively. On the other hand, the APS-TEA system accomplished the same task in 3 h, 6 h, and 10 h respectively. Furthermore, methane hydrate phase-equilibrium data showed that the fracturing fluid's three states, base fluid (BF), fracturing fluid gel (FFG), and gel-breaking liquid (GBL), all exerted an inhibitory effect on the phase equilibrium, with the hydrate suppression temperature (ΔT) ranging from 0.4 to 1.0 K. The differences in their inhibitory effect were primarily related to the micromorphology of the hydroxypropyl guar gum (HPG) molecules and the number of active hydroxyl (-OH) groups in the solution. Cryo-scanning electron microscopy (SEM) measurements revealed that the micromorphology of HPG in BF, FFG, and GBL transformed from regular ribbon-like structures to 3-D network structures and then to hole-containing, short ribbon-like structures. FFG formed a regular 3-D network structure after adding crosslinking agents to the BF. The ΔT values reversed from FFG < BF to FFG > BF when the HPG concentration increased from 0.3 wt% to 0.5 wt%, possibly due to the difference in the HPG molecules' water adsorption capacity before and after crosslinking. The broken HPG molecules with OH− groups in the solution were transformed into residues after gel-breaking, decreasing the GBL's inhibitory effect. Therefore, our results indicated that micromorphology variations could cause differences in the HPG molecules' water adsorption capacity, ultimately leading to ΔT differences. Based on our findings, the gel-breaking fracturing fluid systems we developed demonstrated potential for optimizing hydraulic fracturing in marine hydrate reservoirs.

Fourier's and Fick's laws analysis of couple stress MHD sodium alginate based Casson tetra hybrid nanofluid along with porous medium and two parallel plates

Scientists from around the world are engaged in the investigation of non-Newtonian fluids containing both mono and dihybrid nanoparticles. The primary aim is to gain a deeper understanding of the heat transfer properties of these fluids, with potential implications for treating various physical phenomena. Specifically, researchers are focusing on the effects of unique tetra hybrid Tiwari and Das nanofluid models on the flow. By delving into the intricate behavior of fluids containing numerous nanoparticles, the researchers aim to explore the applications of these fluids. One aspect of this investigation is an examination of the flow of a Sodium Alginate (SA)-based Casson tetra hybrid nanofluid through a porous medium and between two parallel plates, taking into consideration the influence of couple stress. This particular exploration adds to the comprehensive understanding of these unique fluids and their potential application in medical and engineering contexts. The motion W0H(t)cos(wt) of the plate at rest of plate drives the flow, whereas the plate at y = d remains motionless. Physical phenomena are described using partial differential equations, which are then dimensionless by using variables with no dimensions. By utilizing Fourier's and Fick's equations, the conventional model has been enhanced to incorporate a time fractional model, which provides a dimensionally stable solution. One can effectively solve the generalized fractional model by utilizing the powerful techniques of the Fourier and Laplace integral transforms. These methods allow us to simplify complex equations and enable us to analyze and solve them with greater ease. The Casson parameter, coupling stress parameter, porosity parameter, and magnetic parameter's parametric effects are also studied. The values for Grashof, Schmidt, and Prandtl are shown in a table format. Skin friction, heat conduction, and Sherwood numbers are all computed and summarized. Based on the findings of the graphics, it can be concluded that the fractional Casson fluid model described a more accurate aspect of the fluid velocity profile, temperature profile, rate of skin friction and heat transfer than the conventional Casson fluid model.

Heat transfer performance of magnetohydrodynamic multiphase nanofluid flow of Cu–Al2O3/H2O over a stretching cylinder

Abstract This study examines the heat transfer properties of a recently created hybrid nanofluid in contrast to a traditional nanofluid. The aim is to improve the transfer of heat in the flow of the boundary layer by employing this novel hybrid nanofluid. Our study investigates the impact of the Lorentz force on a three-dimensional stretched surface. We utilize a new model that incorporates thermo-physical factors. A quantitative parametric study is performed to investigate the influence of different physical parameters, enabling meaningful comparisons. The results demonstrate that the hybrid nanofluid exhibits a higher heat transfer rate compared to the conventional fluid, even in the presence of a magnetic field. Moreover, the efficiency of heat transfer can be enhanced by modifying the concentration of nanoparticles in the hybrid nanofluid.

Goal-directed fluid therapy using stroke volume variation on length of stay and postoperative gastrointestinal function after major abdominal surgery-a randomized controlled trial

Background and objectiveThe effectiveness of goal-directed fluid therapy (GDFT) in promoting postoperative recovery remains unclear, the aim of this study was to evaluate the effect of GDFT on length of hospital stay and postoperative recovery of GI function in patients undergoing major abdominal oncologic surgery.MethodsIn this randomized, double- blinded, controlled trial, adult patients scheduled for elective major abdominal surgery with general anesthesia, were randomly divided into the GDFT protocol (group G) or conventional fluid therapy group (group C). Patients in group C underwent conventional fluid therapy based on mean arterial pressure (MAP) and central venous pressure (CVP) whereas those in group G received GDFT protocol associated with the SVV less than 12% and the cardiac index (CI) was controlled at a minimum of 2.5 L/min/m2. The primary outcomes were the length of hospital stay and postoperative GI function.ResultsOne hundred patients completed the study protocol. The length of hospital stay was significantly shorter in group G compared with group C [9.0 ± 5.8 days versus 12.0 ± 4.6 days, P = 0.001]. Postoperative gastrointestinal dysfunction (POGD) occurred in two of 50 patients (4%) in group G and 16 of 50 patients (32%) in the control group (P < 0.001). GDFT significantly also shorten time to first flatus by 11 h (P = 0.009) and time to first tolerate oral diet by 2 days (P < 0.001).ConclusionsGuided by SVV and CI, the application of GDFT has the potential to expedite postoperative recovery of GI function and reduce hospitalization duration after major abdominal surgery.Trial registrationThis study was registered on www.clinicaltrials.gov on 07/05/2019 with registration number: NCT03940144.

Nanoakışkanların Isıl Sistemlerde Enerji Verimliliğine Etkisi: Deneysel Verilerin Isıl ve Hidrodinamik Performans Ölçütleri ile Değerlendirilmesi

The energy efficiency of heat exchangers has become crucial in industrial applications due to ever-increasing energy costs. Therefore, various methods have been developed to enhance heat transfer and accelerate the process (shortening the time), reduce the size of heat exchangers, and increase energy (fuel) efficiency. In recent years, researchers have recommended nanofluid suspensions in place of common heat transfer fluids to improve energy efficiency. Nanofluid suspensions are obtained by adding nanometer-sized particles (less than 100 nm in at least one dimension) to heat transfer fluids. This study focused on experimental data in the literature to investigate the effects of nanofluids on transferred thermal power and required pumping power in heat exchangers. The relationship between the transferred thermal power and the pumping power was defined by two different performance criteria (Performance Evaluation Criterion-PEC and Energy Efficiency Criterion-EEC), allowing us to scrutinize the effects of nanofluids in thermal systems on energy efficiency (energy consumption) from a more realistic perspective. The results show that nanofluids are more disadvantageous than conventional heat transfer fluids in terms of the energy budget in industrial applications. It is concluded that nanofluids can be used in special applications where those disadvantages are insignificant.

Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Nanofluids: An Experimental Study for MQL Grinding

In the course of grinding, conventional grinding fluid is frequently utilised, which leads to excessive consumption and negative environmental effects. MQL, or minimum quantity lubrication, is a possible replacement for traditional dry and fluid coolant application. It is well known that the MQL grinding process's effectiveness depends on the lubricating and cooling capabilities of fluid. A water-based Al2O3 nanofluid was used in this work to grind materials due to its outstanding convective heat transfer and thermal conductivity qualities. Hardened steel's grinding properties are examined and contrasted with those of MQL grinding done in wet, dry, and pure water. Al2O3 nanofluid MQL grinding using water dramatically lower the grinding temperatures, minimise grinding forces, and enhance the ground surface finish.

Direct numerical simulation of supercritical CO2 near the critical point flowing over a single Stefan flow-affected spherical particle

scCO2 (supercritical CO2) is now an efficient, clean, and pollution-free solvent widely used in industrial productions, such as extraction, printing and dyeing, as well as pharmaceutical productions. In general, a radial mass flux will exist on the surface of active component particles or drug particles during the process of particle dissolution or re-forms due to variations in operating condition of scCO2, which is called Stefan flow. Comparing with the conventional fluids (0.744 < Pr(Prandtl number) < 1.5), typical high-Pr characteristic (Pr > 10) of scCO2 near critical point will present a unique heat transfer performance, while the relative variations of density and viscosity near critical point affect the mechanics characteristic of particle and distribution details of flow field near particle surface, especially considering the effect of different intensities and directions of Stefan flow. To this, based on the PR-DNS (Particle Resolve-Direct Numerical Simulation) method, this work investigates the Stefan flow-affected drag of the sphere, the flow and temperature field near sphere surface, as well as the interphase heat transfer on the sphere surface. We pay more attention to the high-Pr characteristic and relative variations of density and viscosity of scCO2 near critical point. Results point out that the correlation of Nu (Nusselt number) vs. Resf (Stefan Reynolds number) is no longer linear compared with the cases of conventional fluids, and variable physical properties lead larger drag coefficient while worse heat transfer performance.

Challenges, limitations, and applications of nanofluids in solar thermal collectors-a comprehensive review.

The daily increase in the demand for energy consumption is partly caused by the global population explosion and advancements in technology. Humanity relies on energy to fulfil its daily routines, such as electricity for lighting, heating, cooling, and running electronic devices. There are continuous attempts by researchers and industry experts to optimize and enhance the efficiency of various sustainable energy generation devices. Solar collectors play a critical role in the renewable energy sector, which is vital in helping the world achieve a clean, green, and sustainable environment. Over the last two decades, researchers have made significant efforts to explore various techniques for enhancing the effectiveness of solar thermal collectors. Their effort has been centered around improving the fluid thermal properties, which act as the heat transfer medium in solar collectors. The discovery of nanofluids will help resolve some of the challenges associated with conventional fluid used in solar collectors. Enhancement through nanofluids is influenced by several factors, which include nanoparticle types, nanoparticle concentration, base fluid, and the purpose of its application. This review provides a technical summary of the application of nanofluids in the two main types of collectors: non-concentrating and concentrated thermal collectors. Findings from this study showed that TiO2 + Cu hybrid nanofluids with a mass fraction of 0.03 augment heat transfer coefficient by 21% in parabolic trough collectors. The merits of employing nanofluids as heat transfer fluids in solar collectors are examined, while also outlining the obstacles and areas where further research is needed.

Thermodynamic Investigation and Economic Evaluation of a High-Temperature Triple Organic Rankine Cycle System

Triple organic Rankine cycle (TORC) is gradually gaining interest, but the maximum thermal efficiencies (around 30%) are restricted by low critical temperatures of common working fluids (&lt;320 °C). This paper proposes a high-temperature (up to 400 °C) TORC system to ramp up efficiency. A near-azeotropic mixture biphenyl/diphenyl oxide (BDO), which has a stellar track record in the high-temperature ORC applications, is innovatively adopted as the top and middle ORC fluid simultaneously. Four conventional organic fluids are chosen for the bottom ORC. A mixing heat exchanger connects the top and middle ORCs to reduce irreversible loss. Thermodynamic analysis hints that the optimal performance is achieved on the use of benzene as the bottom fluid. The maximum thermal and exergy efficiencies are respectively 40.86% and 74.14%. The largest exergy destruction occurs inside the heat exchanger coupling the middle and bottom ORCs, accounting for above 30% of the total entropy generation. The levelized energy cost (LEC) is 0.0368 USD/kWh. Given the same heat source condition, the TORC system can boost the efficiency by 1.02% and drive down LEC by 0.0032 USD/kWh compared with a BDO mixture-based cascade ORC. The proposed system is promising in solar thermal power generation and Carnot battery applications using phase change materials for storage.

Electroosmosis‐modulated Darcy–Forchheimer flow of Casson nanofluid over stretching sheets in the presence of Newtonian heating

A review of the literature revealed that nanofluids are more effective in transferring heat than conventional fluids. Since there are significant gaps in the illumination of existing methods for enhancing heat transmission in nanomaterials, a thorough investigation of the previously outlined models is essential. This study’s main objective is to examine the Casson nanofluid’s Darcy-Forchheimer flow across a stretching sheet. Investigations are being conducted on the viscous and Joule dissipations that the electroosmosis forces (EOF) have on the casson nanofluid boundary layer. The method transforms partial differential equations originating in nanofluidic systems into nonlinear differential equation systems with the proper degree of similarity. With a precision of order 4 to 5, the nonlinear nanofluid problem is solved using the (FDM) finite difference approach (Lobatto IIIA), which is accomplished using a number of collocation locations. The ability of Lobatto IIIA to handle coupled differential equations that are very nonlinear is one of its strengths. The boundary value dilemma (bvp4c) solver, which is a component of the MATLAB software programme, is used to reduce the higher order differential equations into a first order technique and computationally analyze the simplified mathematical model. When compared to previously published studies, the data acquired showed a high degree of accuracy and symmetry. The study’s primary results included that when the Casson fluid expands, the velocity field decreases, but the electric parameter, Forchheimer number, local Reynolds number, and permeability parameter show the opposite trend. Furthermore, High temperature is connected with the non-Newtonian heating parameter and the electric parameter. This work provides insights into practical applications such nanofluidic, energy conservation, friction reduction, and power generation. However, the work makes a significant point that the flow of a Casson fluid including nanoparticles can be regulated by appropriately modifying the Casson parameter, thermophoresis parameter, and Brownian motion parameter.

Optimization of gaseous working fluid and internally finned absorber tube for enhancing the thermal performance of parabolic trough solar collector

The current study examined the effect of various types of longitudinal finned absorber tubes with the gaseous working fluid on the performance of the parabolic trough collector. Conventional heat transfer fluids, such as water, thermal oils, molten salts, etc., have been limited when the parabolic trough collector works at very high temperatures. Gas may be used as heat transfer fluid when this collector may operate at very high temperatures. However, the heat transfer coefficient of gas is smaller than the conventional heat transfer fluid. Therefore, fins may be used to improve the parabolic trough collector's thermal performance when gas is used as heat transfer fluid. Hence, selecting the best suitable gas as heat transfer fluid and the optimum fin structure is essential to improve this collector's thermal performance. In this context, the current study has considered seven different gases, namely air, carbon dioxide, helium, nitrogen, oxygen, methane, and neon, and six longitudinal finned absorber tubes with different profiles, namely, rectangular, triangular, trapezoidal, T-shaped, and Y-shaped to select the best suitable heat transfer fluid and optimum fin structure. The best suitable gas and optimum fin profile have been chosen based on specific criteria (multi-objective optimization technique or the performance enhancement factor index). This problem has been simulated using commercial software ANSYS Fluent 2020 R2. The experimental and numerical data discovered in the literature are used to validate the results of the current investigation and found in good accuracy between them. The methane gas is found to be the most suitable heat transfer fluid based on both criteria. Then, the effect of mass flow rate and inlet temperature of methane gas on the average friction factor and Nusselt number have been investigated. It is found that the average friction factor decreases with the mass flow rate for the given inlet temperature, while the opposite trend has been observed for the average Nusselt number. For the first time, the T-shaped and Y-shaped finned absorber tube has been proposed in the present study and compared with earlier fin profiles utilized by the researcher. It is found that the increment in thermal efficiency for T-shaped and Y-shaped finned absorber tubes with methane gas is 8.9338 % and 10.1360 %, respectively. In contrast, the increment in exergy efficiency for T-shaped and Y-shaped finned absorber tubes is 8.942 % and 11.622 %, respectively. There is a significant improvement in the thermal and exergy efficiency of the proposed model compared to the models considered in the literature (air flow through absorber tube with the rectangular fin profile). Furthermore, the highest average Nusselt number of 480.4651 is found for the T-shaped finned absorber tube than other examined cases. However, the friction factor is also high for these fin profiles. As a result, the value of the performance enhancement factor for this fin profile is reduced, and the maximum value of the performance enhancement factor is obtained for rectangular fin profiles. Generally, increasing fin height and width increases thermal performance and pressure loss. Therefore, six different dimensions of rectangular fin have been studied and compared with smooth tubes. It is found that the optimum fin dimension of the rectangular fin is a height of 5 mm and a width of 4 mm. The present results can be utilized for designing an internally finned absorber tube to improve the collector's thermal performance with gas as heat transfer fluid.

Effect of viscous dissipation due to magnetohydrodynamic flow in an inclined channel

Graphene oxide nanoparticles with higher thermal conductivity aid in enhancing the flow and heat transport in magnetohydrodynamic (MHD) devices such as MHD pumps. Modelling such devices with promising applications inherently necessitates the entropy studies to ensure efficient models. In conventional fluids, Lorentz force controls the fluid velocity in the presence of magnetic field. Whereas, the use of graphene oxide hypothesized the enhancement of flow, despite the impacts of Lorentz force, due to high thermal conductivity. This paper is an investigation to computationally study the hypothesis and to analyse the entropy generation in magnetohydrodynamic flow of graphene oxide (GO) in an inclined channel. Buongiorno nanofluid model is used including the impacts of nanoparticle attributes namely thermophoretic and Brownian diffusion along with viscous dissipation effects. Spectral quasilinearization method with Chebyshev's polynomials is adapted to solve the differential equations under convective conditions. On studying the effects of implanted parameters, it is concluded that the flow velocity enhancement by Hartmann number is remarked and is proved to be achieved from the thermal conductivity of graphene oxide particles. A quantitative analysis is made with the previously published results for special cases. Furthermore, investigations conclude that the entropy is contributed primarily from the heat transfer.

Stability study of aqueous foams under high-temperature and high-pressure conditions relevant to Enhanced Geothermal Systems (EGS)

In Enhanced Geothermal System (EGS) hydraulic fracturing is carried out by injecting cold water into deep Hot Dry Rocks (HDR) under carefully controlled conditions to create new or reopen existing fractures. Water-based fracturing fluids demonstrate some challenges including immense quantity of water usage, water sensitivity of the formations, water blocking, and lack of proppant carrying capacity and transportation. Thus, an alternative is to use foam-based fracturing fluid which offers potential advantage over conventional water-based fracturing fluid such as minimum water usage, reduced wellbore damage, high proppant carrying capacity, and less environmental damage. However, foams are complex mixture of gaseous phase and liquid phase which are thermodynamically unstable at downhole conditions, and their stability can decrease over time due to liquid drainage, bubble coarsening, and coalescence. This paper shows laboratory experiments executed to study foam stability at high temperature (200 °C) and high pressure (6.9 MPa) conditions which simulates the geothermal environment. Foam stability was characterized by half-life of foam, which is defined as the time taken by the foam to decreases by 50% of its original height due to drainage. In this paper, two types of gaseous phases, nitrogen (N2) and carbon dioxide (CO2) were investigated. Also, based on successful practice of foam-based fracturing fluid in oil and gas industries, four surfactants, including Alpha olefin sulfonate (AOS), Sodium dodecyl sulfonate (SDS), Tergitol™ (NP – 40), and Cetyltrimethylammonium chloride (CTAC) at optimum concentration of 1 wt.% were tested for best stability performance. In addition, different stabilizing agents including guar gum, bentonite clay, crosslinker, silicon dioxide nanoparticles (SiO2), graphene oxide (GO) were also studied. Experimental results showed that N2 foams were more stable than CO2 foams. It was observed that foam half-life decreased with the increase in temperature. Among all the surfactants, AOS foams showed the most promising thermal stability at high temperatures. Moreover, with the addition of stabilizing agents, foam's half-life was enhanced. Stabilizing agents such as crosslinker and GO dispersion showed the most stable foams with half-life recorded at 20 min and 17 min, respectively, at 200 °C and 6.9 MPa. Finally, pressure also showed a positive effect on foam stability; with increased pressure, foam half-life was increased. Based on the experimental data, analytical models for the effect of temperature and pressure were developed, considering foam degradation is a first-order kinetic reaction that linearly depends on the foam drainage mechanism. The effect of temperature on foam half-life was studied as an exponential decay model. In this model, foam half-life is a function of drainage rate constant (DA) and activation energy (Ea) of the foam system. The effect of pressure on foam half-life was found to obey a power-law model where an increase in pressure showed an increase in foam half-life. Furthermore, a linear relation was studied for the effect of pressure on foam activation energy and drainage rate. Then the combined effects of temperature and pressure were studied, which yielded an analytical model to predict the foam stabilities in terms of half-life for different foam compositions. This research indicates that with an appropriate selection of surfactants and stabilizing agents, it is possible to obtain stable foams, which could replace conventional water fracturing fluid under EGS conditions.

Thermal impacts of electromagnetic trihybrid nanofluid flow through a porous expanding sheet with chemical amalgamation: Entropy analysis

The challenge arises from the inadequacy of conventional fluids to facilitate effective heating and cooling processes in industries. Trihybrid nanofluids, consisting of a combination of three distinct types of nanoparticles suspended in base fluids, emerge as the upcoming generation of heat transfer mediums. This innovative category of fluids can be attributed to their broad potential applications in a multitude of nanotechnology and heat transfer devices. The aim of the present study is to analyse the generation of entropy resulting from the changes in temperature-dependent viscosity in the motion of an electromagnetic trihybrid nanofluid over a porous stretched surface. This investigation considers the impact of radiation, heat sources, and chemical reactions. The nonlinear partial differential equations that govern the system are converted into ordinary differential equations using a similarity substitution. The resulting ODEs are subsequently resolved by means of the shooting mechanism in conjunction with the Runge-Kutta-Fehlberg methodology. The findings of the study have been elucidated via the execution of a comparative analysis involving three types of nanofluids. The velocity of the nanofluids decreased by 13.12% and 15.8% due to changes in viscosity and porousness, while it exhibited a 13.12% increase in trihybrid nanofluids with enhanced convection.The velocity demonstrates an inverse relationship with electric and magnetic fields, leading to a 2% variation in nanoparticle behavior. However, the temperature increases by 8.24% in trihybrid nanofluids subjected to the same fields. The Eckert number, radiation, and heat source parameters enhance the temperature in trihybrid nanofluids by 8.12%. The electric and magnetic field intensities result in a reduction of entropy production in nanofluids by 4.92%, while the Bejan number experiences a 14.48% increase in trihybrid nanofluids under the same fields. Moreover, Eckert number, heat generation, and electric and magnetic fields lead to accelerated heat transfers. The findings suggest that trihybrid nanofluids transfer heat 9.24% faster than regular or hybrid nanofluids.

Novel Environmentally Friendly Nanomaterials for Drag Reduction of the Emulsified Acid System.

Matrix acidizing is a technique that is widely used in the petroleum industry to remove scales and create channels in the rock. Removal of scales and creation of channels (wormhole) enhance productivity. Conventional acidizing fluids, such as hydrochloric acid (HCl) for carbonate and a mixture of hydrofluoric acid (HF) and HCl acid, are used for the matrix acidizing process. However, these fluids have some drawbacks, including strong acid strength, corrosion at high temperatures, and quick reactions with scale and particles. Emulsified acid systems (EASs) are used to address these drawbacks. EASs can create deeper and narrower wormholes by reducing the reaction rate of the acid due to the external oil phase. However, EASs have a much higher viscosity compared to conventional acidizing fluids. The high viscosity of EASs leads to a high drag that restricts pumping rates and consumes energy. This study aims to utilize environmentally friendly and widely available nanomaterials as drag-reducing agents (DRAs) of the EAS. The nanomaterials used in this study are carbon nanodots (CNDs). CNDs have unique properties and are used in diverse applications in different industries. The size of these CNDs is usually smaller than 10 nm. CNDs are characterized by their biocompatibility and chemical stability. This study investigates the use of CNDs as DRAs for EAS. Several experiments have been conducted to investigate the CNDs as a DRA for the EAS. The developed EAS was initially tested for conductivity and drop-test analysis to ensure the formation of an inverted emulsion. Thereafter, the thermal stability for the range of temperatures and the rheological properties of the EAS were evaluated to meet the criteria of field operation. Then flow experiments with EASs were conducted before and after adding the CNDs to investigate the efficacy of drag reduction of EASs. The results revealed that CNDs can be used as viscosity reducers for the EAS, where adding the CNDs to the EAS reduces the viscosity at two different HCl concentrations (15 and 20%). It reduces the viscosity of the EAS in the presence of corrosion inhibitors as well as other additives to the EAS, showing its compatibility with the field formulation. The drag reduction was observed at the range of temperatures investigated in the study. The conductivity, stability, and rheology experiments for the sample taken after the flow experiment are consistent, ensuring CNDs work as a DRA. The developed EAS with CNDs is robust in terms of field mixing procedures and thermally stable. The CNDs can be used as a DRA with EAS, which will reduce drag in pipes, increasing pumping rates and saving energy.