Search

To develop a green drilling fluid additive, the modification and application of persimmon peel in a water-based drilling fluid was studied in this work. A natural product derivative, aluminium chloride–persimmon peel (ACPP), was prepared from aluminium chloride and persimmon peel and was assessed as a shale inhibitor. The clay-swelling ratio in 0.30% ACPP-3 solution was reduced to 28.10% from 69.50%. The rolling recovery tests and rheological evaluation of drilling fluids concluded that ACPP-3 has a high inhibition property to montmorillonite-hydrated expansion. ACPP-3 can adjust the particle size of montmorillonite to a large degree. ACPP-3 effectively reduces the apparent viscosity of carboxymethyl cellulose drilling fluids and the volume of filtration; furthermore, ACPP-3 can reduce the viscosity and the volume of filtration under high temperature, which means it can be used as an additive for deep drilling. The inhibition mechanism of ACPP-3 was investigated by thermogravimetric analysis and scanning electron microscopy. The results of this scientific research will be beneficial to the eco-friendly drilling fluid materials.

Thermal energy storage system is one type of the system used to store the energy in different industrial applications. Thermal performance of the system is important to analyze when it has been operated with nanofluids. There is lot of energy is wasted from many process which can be utilized for the another process such as to preheat the water. In the present paper, the effect of water based nanofluids is studied to store the energy and results have been compared with base fluid. It was observed the nanofluid have more capacity to store the energy as compared to the base fluid because of it superior thermal transport properties. The pressure drop is also slightly higher than of base fluid. The thermal storage capacity of the system is significantly increased when it has been used with nanofluids as compared to base fluid under the same operating condition.

In this study, the flow and heat transfer characteristics of the forced pulsating Al2O3-water nanofluid were numerically studied. The pulsating excitation of the nanofluid is provided by the Helmhertz self-excited oscillating cavity. The large eddy simulation method is used to solve the equation, and the local Nusselt number and heat transfer performance index are used to analyze the heat transfer characteristics of the nanofluid in the self-excited oscillation heat exchange tube. In addition, the effect of different downstream tube diameters on heat transfer enhancement is discussed. The research results show that the existence of the countercurrent vortex can increase the disturbance of the near-wall fluid, thereby improving the mixing degree of the near-wall fluid and the central mainstream. As the countercurrent vortex migrates downstream, pulse enhanced heat transfer is realized. Furthermore, it was also found that when the downstream tube diameter d2 = 1.8d1, the periodic effect of the local Nusselt number of the wall is the best and the heat transfer performance index has the most stable pulsation effect within a pulsation cycle. But when d2 = 2.0d1, the change curve of heat transfer performance index in a pulsating period is the highest, the maximum value is 3.95.

The present work is an attempt to carry on analytical work on a biodegradable cellulosic material obtained from the fibre of a plant which is scientifically known as Grewia Optiva. In this study, 125 µm particle size of Grewia optiva fibres was used as a filtration loss controlling agent in drilling fluid. The Grewia Optiva mud samples were hot rolled at 100 °C for 16 h and it was observed that the said fibre at 5% concentration (w/v) has reduced the low pressure–low temperature (LPLT) filtration loss of drilling mud by 72.5% under the differential pressure of 100 psi. On further assessment vis a vis comparative analysis with available market products like carboxy methyl cellulose-low viscosity grade (CMC-LVG) and polyanionic cellulose-low viscosity grade (PAC-LVG), it was found that addition of CMC and PAC-dLVG at 1.4% (w/v) in reference mud, the LPLT filtration loss was reduced by 70% and 70.6%, respectively. Use of 5% GOFP in the reference mud, the high pressure-high temperature (HPHT) filtration loss of drilling fluids was reduced by 69.2% at 100 °C temperature and 500 psi pressure. The thickness of filter cake was reduced by 41.1% after the addition of 5% GOFP in the reference mud. While the conventional fluid loss reducing agents such as CMC and PAC, both at 1.4% concentration have reduced the HPHT filtration loss by 63.46% and 64.6%, respectively, as compared to reference mud. This is indicative of a valid filtration loss control potential of Grewia optiva fibre powder.

This article investigates the natural convection heat transfer and inclined magnetic-field effects of a nanofluid past a vertical stretching sheet embedded in a porous medium with a non-uniform hea...

Purpose In flexible electronics applications, organic inks are mostly used for inkjet printing. Three-dimensional (3 D) printing technology has the advantages of low cost, high speed and good precision in modern electronic printing. The purpose of this study is to solve the high cost of traditional printing and the pollution emissions of organic ink. It is necessary to develop a water-based conductive ink that is easily degradable and can be 3 D printed. A nano-silver ink printed circuit pattern with high precision, high conductivity and good mechanical properties is a promising strategy. Design/methodology/approach The researched nano-silver conductive ink is mainly composed of silver nanoparticles and resin. The effect of adding methyl cellulose on the ink was also explored. A simple 3 D circuit pattern was printed on photographic paper. The line width, line length, line thickness and conductivity of the printed circuit were tested. The influence of sintering temperature and sintering time on pattern resistivity was studied. The relationship between circuit pattern bending performance and electrical conductivity is analyzed. Findings The experimental results show that the ink has the characteristics of low silver content and good environmental protection effect. The printing feasibility of 3 D printing circuit patterns on paper substrates was confirmed. The best printing temperature is 160°C–180°C, and the best sintering time is 30 min. The circuit pattern can be folded 120°, and the cycle is folded more than 60 times. The minimum resistivity of the circuit pattern is 6.07 µΩ·cm. Methyl cellulose can control the viscosity of the ink. The mechanical properties of the pattern have been improved. The printing method of 3 D printing can significantly reduce the sintering time and temperature of the conductive ink. These findings may provide innovation for the flexible electronics industry and pave the way for alternatives to cost-effective solutions. Originality/value In this study, direct ink writing technology was used to print circuit patterns on paper substrates. This process is simple and convenient and can control the thickness of the ink layer. The ink material is nonpolluting to the environment. Nano-silver ink has suitable viscosity and pH value. It can meet the requirements of pneumatic 3 D printers. The method has the characteristics of simple process, fast forming, low cost and high environmental friendliness.

An all-dielectric metamaterial absorber based on water resonator encapsulated in resin container is proposed. The absorber can afford the maximum absorption up to 98% at 190 GHz, as well as the wid...

The current research demonstrates the revolving flow of water-based Fe3O4 nanofluid due to the uniform rotation of the disc. This flow of nanofluid is investigated using CFD Module in COMSOL Multiphysics. However, the similarity solution for this flow is also obtained after transforming the given equation into a non-dimensional form. In the CFD Module, streamlines and surface plots are compared with the similarity solution for the magnitude of the velocity, radial velocity, tangential velocity, and axial velocity. The results from the direct simulation in the CFD Module and the solution of dimensionless equations represent a similar solution of velocity distribution. The derived results show that increasing the volume concentration of nanoparticles and effective magnetic parameters decrease the velocity distribution in the flow. Results in the CFD Module are important for monitoring the real-time particle tracing in the flow and, on the other hand, the dimensionless solution is also significant for the physical interpretation of the problem. Both methods of solution empower each other and present the physical model without sacrificing the relevant physical phenomena.

This paper aims at assessing the use of nanomaterials in painting conservation and in cleaning practices that could be alternative to the traditional ones to overcome the limits of new green materials. Titanium dioxide nanoparticles have been spread and studied on historical painting surfaces with good results. In particular, the properties of TiO2 nanoparticles have been considered useful for self-cleaning and protective purposes against the accumulation of dirt and dust that represents the first phase in deterioration of historical painting surfaces. TiO2 nanoparticles, prepared in distilled water by Pulsed Laser Ablation in Liquids, were applied on painting mock-ups realized in the laboratory according to old recipes and using historical binders and pigments. The surface characteristics of the painting were investigated by contact angle measurement and by Atomic Force Microscopy. The optical and aesthetical compatibility of the colloidal dispersions with the painting was assessed by spectrophotometry, and then the cleaning efficiency was evaluated by discoloration of a dye under ultraviolet irradiation, at fixed time intervals, using colorimetric technique. Because of the high reactivity of nanoparticles, the possibility of degrading the painting surface, together with the chromatic marker, was examined by colorimetric measurements. The evaluation of the color changes is important for all the materials belonging to cultural heritage, especially painting, for which the color modification induced by protective and/or cleaning interventions could irremediably compromise the work of art.

Purpose The aims of this study is to numerically investigate the thermal phenomena during magnetohydrodynamic (MHD) free convection in an oblique enclosure filled with porous media saturated with Cu–Al2O3/water hybrid nanofluid and heated at the left wavy wall. The thermophysical phenomena are explored thoroughly by varying the amplitude (λ) and undulation (n) of the wavy wall and the inclination of the enclosure (γ) along with other pertinent physical parameters. Darcy–Rayleigh number (Ram), Darcy number (Da), Hartmann number (Ha) and nanoparticle volumetric fraction (ϕ). The effect of all parameters has been analyzed and represented by using heatlines, isotherms, streamlines, average Nusselt number and local Nusselt number. Design/methodology/approach The finite volume method is used to work out the transport equations coupled with velocity, pressure and temperature subjected to non-uniform staggered grid structure after grid-sensitivity analysis by an indigenous computing code and the semi-implicit method for pressure linked equations (SIMPLE) algorithm. The solution process is initiated following an iterative approach through the alternate direction implicit sweep technique and the tridiagonal matrix algorithm (TDMA) algorithm. The iterative process is continued until successive minimization of the residuals ( Findings This study reveals that the increase in the heating surface area does not always favor heat transfer. An increase in the undulation amplitude enhances the heat transfer; however, there is an optimum value of undulation of the wavy wall for this. The heat transfer enhancement because of the wall curvature is revealed at higher Ram, lower Da and Ha and lower volume fraction of nanoparticles. In general, this augmentation is optimum for four undulations of the wavy wall with an amplitude of λ = 0.3. The heat transfer enhancement can be more at the cavity inclination γ = 45°. Research limitations/implications The technique of this investigation could be used in other multiphysical areas involving partial porous layers, conducting objects, different heating conditions, wall motion, etc. Practical implications This study is to address MHD thermo-fluid phenomena of Cu–Al2O3/water-based hybrid nanofluid flow through a non-Darcian porous wavy cavity at different inclinations. The amplitude and number of undulations of the wavy wall, permeability of the porous medium, magnetic field intensity, nanoparticle volumetric fraction and inclinations of the enclosure play a significant role in the heat transfer process. This analysis and the findings of this work can be useful for the design and control of similar thermal systems/devices. Originality/value Many researchers have examined the problem of buoyancy-induced free convection in a wavy-porous cavity packed with regular fluids or nanofluids. However, the effect of magnetic fields along with the amplitude (λ) at different undulations (n) of the heated wavy wall of an inclined enclosure is not attended so far to understand the transport mechanisms. Most often, the evolutions of the thermo-fluid phenomena in such complex geometries invoking different multiphysics are very intricate. Numerical implementations for simulations and subsequent post-processing of the results are also challenging.

Traditional actuators, such as motors as well as hydraulic or pneumatic artificial muscles, demonstrate excessive noise, a heavy weight, and a large size, which limit their practical application in many areas. Therefore, for many decades, scientists have worked to develop new types of silent, small, and light actuators. In this article, a novel soft actuator (actuator

The heat transfer characteristic of nanofluids is tremendously improved by suspending a nano-sized solid particles with a diameter below 20 nm and are considered as prospective working fluids for m...

The present analysis deals with the heat transfer of chemically reactive magnetic-nanofluid over a stretching surface by considering the aligned magnetic field in a porous medium under the influenc...

In recent times, with the advent of exploSration activities in deeper hydrocarbon reserves, drilling of wells in HPHT conditions is one of the most studied field in the upstream oil and gas industry. Water-based fluids are the most common and frequently used drilling fluids oil and gas well construction. Although, water-based drilling fluids are environment friendly and relatively in-expensive, it is often associated with many problems when used in HPHT conditions. In order to overcome these problems in such viable conditions, modified surfactants are used with the mud to counteract the problems associated with it. This paper discusses the different applications of anionic and non-ionic surfactants in water-based drilling fluids both in laboratory and field scales. The paper also discusses the mechanisms of the surfactants and the effect on various mud properties to overcome hole problems like wellbore instability, rheology and filtration loss, foaming and flocculation of mud.

The present study investigates the efficiency of a novel 3D artificially illuminated sono-photocatalytic reactor filled with the suspension of Ti+4 coated Al(OH)3-MWCNT's hybrid nanofluid in removing toxic fragments from the industrial wastewater. Within 40 min of reaction time, the synergistic effect of sonication induced photocatalysis achieved 99 percent dye degradation. Using response surface methodology (RSM-CCD) and artificial neural network (ANN) methods, the behaviour of the process in terms of reactor independent variables on dye removal was investigated and optimised. Both approaches proved to have a very good performance in modelling of the process and from RSM model, the optimum experimental conditions were at 0.5 vol% nanofluid concentration, 60 °C nanofluid temperature, and 60 min reaction time. Besides that, a quadratic polynomial equation (R 2 = 0.984) well describes the equilibrium data. Furthermore, the study of variance (ANOVA) approach revealed that the input parameters and their interactions had a substantial impact on the response variable. With an R 2 value of 0.999, the engineered multilayer perceptron ANN successfully validated the experimental findings. Given the significant improvement in photocatalytic degradation of industrial wastewater, the current research can be viewed as a promising pre-treatment step for producing low toxic intermediates.

The wear behaviors of 4145H drilling tool steel in water-based slurries were investigated under the conditions of various concentrations of SiO2, Al2O3, and SiC sands using a modified ASTM B611 rub...

In the majority of rechargeable batteries including lithium‐ion batteries, polyvinylidene fluoride (PVdF) binders are the most commonly used binder for both anode and cathode. However, using PVdF binder requires the organic solvent of N‐methyl‐2‐pyrrolidone which is expensive, volatile, combustible, toxic, and has poor recyclability. Therefore, switching to aqueous electrode processing routes with non‐toxic binders would provide a great leap forward towards the realization of ideally fully sustainable and environmentally friendly electrochemical energy storage devices. Various water‐soluble binders (aqueous binders) were characterized and compared to the performance of conventional PVdF. Our study demonstrates that the electrochemical performance of Zn/MnO2 aqueous batteries is significantly improved by using sodium carboxymethyl cellulose (CMC) binder. In addition, CMC binders offer desirable adhesion, good wettability, homogeneous material distribution, and strong chemical stability at certain pH levels (3.5–5) without any decomposition for long‐cycle life.

Simulation of Computational Fluid Dynamic is applied to present the thermal performance of water-based Yttrium oxide nanofluid in subchannel of pressurized water reactor (PWR) system. Thermal hydraulic aspect such as pressure drop and heat transfer are estimated in typical conditions of pressurized water with flow rates ranged (20×103≤Re≤80×103) using fresh water (0 %vol.) and different volume fraction of water-Yttrium oxide nanofluid (2 and 4% vol.) as coolant fluid. Results were obtained and compared with correlations of single-phase pressure drop and convective heat transfer for the case of fully developed turbulent flow. The addition of Yttrium oxide nanoparticles to the coolant fluid in pressurized water reactor led to increase in convective heat transfer coefficient and pressure drop. Increasing the nanoparticle volume fraction of (2 and 4% vol.) causing an increase in the average Nu by 3.46% and 7.61%, respectively. The CFD model established in ANSYS software was validated by comparing the pressure drop of CFD results with Blasius correlation and Nu with Ma¨ıga et al. correlation and gave a good agreement.

In this contribution, the investigation conducted on alternative fuels includes methanol 20% blended with gasoline 80% and emulsion-based fuel with the composition of gasoline 80%, ethanol 15%, and H2O 5% are compared with 100% conventional gasoline fuel. These fueled single-cylinders spark ignition engine is studied for checking their performance and emission characteristics as per future emission norms. This work is performed on One-dimensional AVL Boost Simulation Software. The simulations predicted the performance and emission characteristics were far lesser than conventional 100% gasoline. These fuels meet the strict emission regulations of Euro VII. The main purpose of this investigation is to use alternative fuels to improve the performance and emission characteristics of the single- cylinder spark ignition engine and reduce the consumption of fossil fuel reserves. This investigation led to the conclusion that by using methanol 20% in 80% gasoline and micro-emulsion, fuel improves the power, BSFC (brake specific fuel consumption), thermal efficiency and combustion properties of the single-cylinder spark-ignition engine. The CO, HC and NOx emissions were also reduced for alternative fuel than 100% gasoline fuel. The novel water-based emulsion fuel showed the lowest value of NOx emissions as compared to blended 20% methanol with 80% gasoline and 100% gasoline fuel.

Purpose This study aims to deal with the optimization of experimental parameters to obtain maximum heat transfer rate in a Rayleigh–Bénard enclosure filled with the water-based Al2O3 nanofluids using the Taguchi method. Design/methodology/approach The particle size and particle concentration of the Al2O3 nanoparticles are 40 nm and 0.01 Vol. %, respectively. A two-step approach has been used to prepare the nanofluids of the required concentration by mixing the nanoparticles in the distilled water (DW). A Rayleigh–Bénard enclosure, having a hot bottom and a cold top copper plate with insulated side walls, is used for the experiments. Experiments have been conducted first with the DW, for the validation of experimental facility, and second with nanofluid (Al2O3 + DW), for the heat transfer improvement, at three different values of enclosure aspect ratios (ratio of height to width of an enclosure), i.e. 0.5, 1.0 and 1.5. Findings Signal-to-noise ratio (SNR) analysis has been used to determine the optimal levels of design parameters and their contribution toward heat transfer augmentation. The heat transfer, i.e. Nusselt number, is determined for L9 (33) orthogonal array designed by Taguchi method along with corresponding SNR values. The SNR values are plotted for DW and nanofluid to study the effect of different parameters and to identify their optimal levels. It was found that the aspect ratio has the maximum contribution ratio of 78% for the nanofluid and 76.12% for the DW, followed by the heat flux and the height. Originality/value The present results demonstrated the great reliability of the Taguchi method in the optimization of the thermal system to save the time and cost of experiments.

In this study, the optimization of flexographic water-based ink formulation was carried out. The aim is to minimize the contact angle of the ink on polymer substrates. A factorial design was used to evaluate the effects and interactions of three factors, which are dispersant, wetting agent and antifoam concentration on the wettability of ink. The optimal conditions obtained from the desirable response are dispersant of 9.65%, wetting agent of 0.58% and antifoam of 0.55 %. Under these conditions, about 15O of contact angle is obtained. The validity of the statistical experimental strategies was verified by the ink samples prepared under the optimized conditions.

Reasoning of particular mechanism of anomalous thermal transport behaviors is not identified yet for the nanofluids. In this research, the thermal conductivity of maghemite (MH) nanoparticles dispersed deionized water (DW) nanofluids (MH/DW) has been evaluated for the first time using the modified effective medium theories (EMTs). EMTs have been modified with the consideration of static and dynamic effects combinedly for the analysis of anomalous behaviors of thermal conductivity enhancements of the spherical nanoparticles dispersed nanofluids. MH nanoparticles (~20 nm) were synthesized using chemical co-precipitation techniques. MH/DW nanofluids were prepared with the varying MH nanoparticles loading in DW and thermal conductivity was measured using KD2 pro device. The thermal conductivity enhancement (~32 %) was found to be increased linearly with the increasing MH nanoparticle concentration and nonlinearly with the increasing temperature. Existing Maxwell and Maxwell Gantt EMA (MG-EMA) models exhibited awful under-prediction from experimental thermal conductivities of MH/DW nanofluids. Modified model with considering static and dynamic mechanisms of MH nanoparticles combinedly showed reasonably very good agreement with the experimental thermal conductivities of MH/DW nanofluids at elevated temperature. This modified model opens the new windows to analyze the insight of the thermophysical properties of various types of nanofluids by introducing potential parameters.

The thermophysical properties as well as the thermal performance of a nanofluid can be altered upon varying the nanoparticle type and/or nanoparticle volume concentration. Herein, the effects of variable nanoparticle concentration on water-based TiO2, SiO2, TiC, and SiC nanofluids have been studied analytically. The dispersion effects of 1-4% nanoparticle on the single-phase forced convection heat transfer performance of the nanofluids have been investigated. The effective thermophysical properties of the nanofluids are determined adopting the general correlations. The flow velocities of the nanofluids relative to their base fluids are assumed to be constant. Mouromtseff number has been employed as a convenient figure of merit to compare the nanofluids under fully developed internal laminar and turbulent flow conditions. The results indicate an increase in effective density, thermal conductivity, and dynamic viscosity of the nanofluids. Nanofluids containing carbide suspensions exhibit superior heat transfer properties compared to those having oxide suspensions.

The magnetohydrodynamic nanofluid flow comprised of dust particles is carried out in the current investigation. The role of dust nanoparticles on the flow characteristics is vital. The radiative heat phenomena for the interaction of Cu nanoparticle are deliberated in this discussion. However, both water and oil (kerosene) are treated as conventional fluids. Regarding the current applications on nanofluid in industries for the production of several materials, it is important to use the nanoparticles as a coolant. In recent applications, for the CPU cooler Cu-nanoparticle is used because of its high thermal conductivity and as a good conductor of heat. The governing flow characteristics involved with nonlinear properties of partial differential equations are transformed into ordinary differential equations using suitable similarity variables. Further, numerical treatment is imposed using the in-build Matlab code bvp5c. The imitation is carried out for the various profiles using physical parameters and presented graphically. The numerical values for the rate coefficients are presented via tables and deliberated briefly.

Summary In wellbore drilling, it is appreciable to devise methods to study the rheology of high-speed annulus fluid flows. In this paper, a high-speed Taylor-Couette system (TCS) was devised to explore non-Newtonian fluid flow behavior appraised by SiO2 nanoparticles toward friction reduction, power saving, and rheology modeling of nanofluids. Water-based mud (WBM) as an environmentally friendly drilling fluid is investigated by adding SiO2 nanoparticles at four low-volume concentrations of 0.05, 0.1, 0.5, and 1% at speeds from 0 to 1,600 rev/min with 200 rev/min intervals in the TCS. Five rheology models based on the Herschel-Bulkley-Extended (HBE) model and a generalized Reynolds number were optimized to fit with the experimental data. All models except the Newtonian model have fitted all nanofluids with high accuracy, especially Bingham and HBE models. Negative deviation from Darcy friction was avoided for power-law (PL) and Herschel-Bulkley (HB) models using the modification to the generalized Reynolds number. Higher energy saving and enhanced rheology is reported particularly at lower volume concentrations of SiO2 WBM nanofluids. The Darcy friction factor deviated from laminar flow at the generalized Reynolds number beyond 2,000 into turbulent, which is a good indicator for the flow condition of complex non-Newtonian nanofluids in real-life application.

In this research, the effect of nanofluids including graphite and water on the heat transfer enhancement in heat Exchangers with both straight and rotational inner tube were examined. Nano-fluids including graphite and water were obtained at 0.01, 0.02 and 0.03 %volume concentrations by means of pure water as a base fluid. The aim of the study is to experimentally investigate and compare the influence of straight inner tube on the performance of a double tube heat exchanger at different flow rates, different capacity ratios (0.25, 0.5, 0.75, 1), different rotation rates (0 RPM, 100 RPM, 150 RPM, 200 RPM, 300 RPM, 500 RPM and 750 RPM) and by using nanofluid including graphite and water volume at values of 0.01, 0.02, 0.03%. In the experiments the flow is turbulent. In order to determine the heat transfer enhancement, the experimental datas were compared for pure water and nano-fluids. According to the results, Nusselt number, pressure loss, efficiency of heat exchanger were gauge. By the results achieved from experiments, correlations for Nusselt number have been reproduce and experimental data have been compared with ones in the literature by drawing graphics. The experiment that provides the best increase in heat transfer is the nanofluid including 0.02% volume concentrations of graphene/water at 500RPM speed.

Waterborne polyurethane (WBPU) has the advantages of environmental, excellent film‐forming property and high bonding strength. However, the mechanical strength of waterborne polyurethane in coating products is not enough, and its wear resistance and softness are poor. In this paper, the Cellulose Nanocrystals (CNC) AQ3 obtained by acid hydrolysis of microcrystalline cellulose was successfully dispersed in the waterborne polyurethane matrix to prepare nanocomposite films with different contents. The mechanical properties, thermal properties, wear resistance and softness of the nanocomposite films were studied by Thermogravimetric (TG), tensile test, dry friction test and KES test. The morphology of CNC dispersed in waterborne polyurethane matrix was studied by Scanning electron microscope (SEM). The results show that the lower content of CNC was uniformly dispersed in the waterborne polyurethane matrix and the interaction between the two forms hydrogen bonds. Compared with waterborne polyurethane, the initial degradation temperature of the nanocomposite films made by adding only 1 wt% CNC increased by 50°C, the tensile strength increased by 179.3%, the wear resistance increased by 19%, and the minimum bending stiffness B reached 0.161 (gf·cm2). The results of this study can be used for textile coating applications, such as polyurethane synthetic leather.

The natural convection heat tranfer in annulate region confined between two homocentric cylinders were numerically studied in the present work. The annulus was filled by ethylene glycol / water based Titania nanofluid. Both internal and external cylinders are presereved at an isothermal hot and cold temperatures respectively, whereas, the upper and lower walls are adiabatic. The numerical solution is obtained by applying the finite volume method along with the SIMPLER, and TDMA algorithms. In the current study, the solid volumetric fraction is varied as (0 % ? ? ? 3 %), the volume ratios of EG to water are varied as (0:100 %, 40 : 60 %, 100:0 %), while both the Rayleigh number and radii ratio are considered fixed at (Ra = 104 and ? = 2). The obtained results indicated that, the average Nusselt number increases as the solid volumetric fraction and the volume ratio of ethylene glycol in the base fluid increase. Moreover, the velocity profiles reach their maximum value in the half region adjacent the internal hot wall when TiO2 – water nanofluid is used. Also, the temperature profiles decrease along the radial distance for all considered values of volume ratios of EG to water.

Background: Researchers working in the field of nanofluid have done many studies on the thermophysical properties of nanofluids. Among these studies, the number of studies on specific heat is rather limited. In the study of the heat transfer performance of nanofluids, it is essential to raise the number of specific heat studies, whose subject is one of the important thermophysical properties. Objective: The authors aimed to measure the specific heat values of Al2O3/water, Cu/water nanofluids and Al2O3-Cu/water hybrid nanofluids using the DTA procedure, and compare the results with those frequently used in the literature. In addition, this study focuses on the effect of temperature and volume concentration on specific heat. Methods: The two-step method was tried to have nanofluids. The pure water selected as the base fluid was mixed with the Al2O3 and Cu nanoparticles and Arabic Gum as the surfactant, firstly mixed in the magnetic stirrer for half an hour. It was then homogenized for 6 hours in the ultrasonic homogenizer. Results: After the experiments, the specific heat of nanofluids and hybrid nanofluid were compared and the temperature and volume concentration of specific heat were investigated. Then, the experimental results obtained for all three fluids were compared with the two frequently used correlations in the literature. Conclusion: Specific heat capacity increased with increasing temperature, and decreased with increasing volume concentration for three tested nanofluids. Cu/water has the lowest specific heat capacity among all tested fluids. Experimental specific heat capacity measurement results are compared by using the models developed by Pak and Cho and Xuan and Roetzel. According to experimental results, these correlations can predict experimental results within the range of ±1%.