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In the current work, authors have performed extensive spray cooling experiments on a 6 mm thick hot stainless steel plate (>900 °C). The work has been separated into two distinctive parts. The first part involves optimization of water flow rate and spray impingement height based on maximum surface cooling rate and heat flux value. The highest cooling rate and heat flux of 133.7 °C/s and 2.21 MW/m2 were attained for a water flow rate of 16 lpm and impingement height of 6 cm. In the second part, different surfactants (cationic, CTAB; anionic, SDS; non-ionic, Tween 20), and polymer (PVP, water soluble) were added in to the water to study its impact on heat transfer parameters such as surface cooling rate, heat flux, and heat transfer coefficient. Amongst all the additives, the maximum enhancement in cooling rate and critical heat flux was achieved for non-ionic (Tween 20) based water solution which is 25.6% (168.2 °C/s) and 19.91% (2.65 MW/m2) higher than what had been attained by water spray. High speed photography was used at a lower temperature to visualize a single droplet impact and to understand the effect of surface tension and underlying physics on the heat transfer phenomenon. This study revealed that upon impingement, surfactant and polymer added drops disintegrate into multiple drops, increasing the overall contact area, and thereby enhancing the heat transfer rate.

The focus of the present study is to investigate the effect of surfactant addition on thermo-physical properties, stability, and heat transfer performance of Cu-Zn-Al LDH nanofluid. For this purpose, both an anionic (Sodium dodecyl Sulfate (SDS), concentration: 200–800 ppm) and a non-ionic surfactant (Tween 20, concentration: 28–70 ppm) have been used at different concentrations with Cu-Zn-Al LDH nanofluid at a fixed concentration. Among both the surfactants, SDS displayed better compatibility and thermo-physical properties when combined with Cu-Zn-Al LDH nanofluid compared to LDH-Tween 20 combination. The addition of both the surfactants into the nanofluid suspension has led to reduced surface tension and viscosity value which is highly desired for better wettability and improved contact between the coolant and the hot surface. The maximum increment in thermal conductivity value was attained in the case of Cu-Zn-Al LDH at 600 ppm SDS concentration which is 20.9% higher than the water. In terms of stability analysis, the highest zeta potential value of −52.7 mV was also observed for Cu-Zn-Al LDH at 800 ppm SDS loading. The highest cooling rate of 174.8 °C/s was attained by Cu-Zn-Al LDH-SDS (600 ppm) nanofluid which is 30.7% higher than what had been achieved by water based cooling. However, the use of Tween 20 in LDH nanofluid has displayed detrimental impact on poor thermal conductivity, zeta potential, and heat transfer results for the LDH nanofluid.

Among various methods used for the reduction of graphene oxide (GO) into a purer form of graphene, the thermal reduction method provides a simpler, safer, and economic alternative, compared to other techniques. Thermal reduction of GO causes significant weight loss and volume expansion of the material. Current work investigates the onset temperature where reduction in terms of exfoliation takes place, which is determined to be 325 °C at standard atmospheric pressure. Reduction temperature plays the most crucial role as it controls the quality of reduced graphene oxide in terms of weight percentage of carbon and lattice defect. The study leads to achieving highest content with a minimum defect in the graphene lattice at the optimum temperature, which is found to be 350 °C at standard atmospheric pressure. The thermal reduction process has been analyzed with the help of Fourier transform infrared spectroscopy, thermogravimetric analysis, and thermal degradation kinetics. From thermal degradation kinetics of GO, the rate of reaction has been found to be independent of concentration and is a sole function of temperature.

Cooling rate in Run Out Table (ROT) in steel industries tailors microstructure which lead to improved mechanical properties. The current work aims to increase cooling performance of steel using TiO...

The current experimental investigation deals with the thermo-physical attributes of Cu-Zn-Al LDH nanofluid its use in high temperature steel cooling. Here, authors used three metals (Copper, Aluminium, and Zinc) having high thermal conductivity to synthesize a brand new nanofluid for heat transfer application. Authors have achieved moderate increment (13.9%) in thermal conductivity value compared to water. A section of this work also aims to maximize the cooling rate which aids in improving mechanical properties of quenched steel plate. The maximum cooling rate of 158.4 °C/s was attained at 160 ppm of nanofluid concentration which is 18.5% higher than that attained by water. In addition to enhanced thermal conductivity, nanoparticle deposition on the cooling surface also contributes to the heat transfer enhancement by providing additional nucleation site. It is also to be considered that above an optimum nanofluid concentration both thermal conductivity and cooling rate values decline. Such trend is owed to several factors namely poor suspension stability, high agglomeration tendency and formation of nanoparticle layer on steel surface which prevents contact between coolant and surface.

In the current study, authors have synthesized Cu-Al Layered Double Hydroxide nanofluid at different molar ratios of Cu and Al by using co-precipitation technique and utilized this as a coolant in a pressure atomized spray to achieve high cooling rates in the temperature range of 900–600 °C for a 6 mm thick steel plate. The study initially focuses on the effect of Cu: Al molar ratio variation on thermal conductivity, stability as well as its heat transfer potential in steel quenching. Post thermal conductivity and stability analysis, spray cooling experiments were conducted in two parts. The first part involves optimization of Cu: Al molar ratio by varying the ratio (Cu: Al = 2:1, 4:1 and 6:1) at a fixed nanofluid concentration (120 ppm) to select the best Cu: Al molar ratio based on heat transfer results. The results show that the highest cooling rate and average heat flux were achieved at a Cu and Al molar ratio of 4:1 among all molar ratio combinations. Once, the optimized molar ratio is selected, the second part of the spray cooling experiments was performed to study the effect of nanofluid concentration variation (40–240 ppm, at an optimized molar ratio of Cu: Al = 4:1) on spray cooling results. With respect to concentration optimization, the maximum cooling rate of 168.6 °C/s was attained at a concentration of 160 ppm which is 26% higher than what was achieved by normal water spray. Results obtained from the spray cooling experiments were further verified by the thermal conductivity analysis where highest enhancement of 15.17% was also observed at 160 ppm nanofluid concentration.

The current work aims to investigate the efficiency of a jet array in cooling of a hot steel plate having surface temperature above 900 °C. The entire study has been divided into two phases. The first phase consists of experiments which are aimed to optimize the jet array impingement height and the water flow rate. It has been found that the cooling rate is enhanced by 60% in case of a jet array compared to a single jet at the same water flow rate and impingement height. In both the single jet and the jet array used in the present work, free falling flow occurs under gravity. In the second phase, the effect of seven different additives on heat transfer performance during cooling has been studied at the optimized values of water flow rate and impingement height. Sodium Dodecyl Sulphate (SDS), Cetyltrimethyl Ammonium Bromide (CTAB) and Tween 20 have been used as surfactant additives, Polyvinylpyrrolidone (PVP) as a polymer additive, Titanium dioxide (TiO2), Cu-Al layered double hydroxide (LDH) and PVP dispersed in TiO2 have been used as nanofluid additives. The results indicate that a maximum cooling rate of 143 °C/s has been achieved for PVP based coolant which is 28% more than that obtained for pure water. The results also prove that ultrafast cooling can be attained by using additive based jet array impingement.

Enhancement of thermal conductivity by the addition of nanofluid is found to improve the rate of cooling of a steel plate. In the present research work, alumina nanofluid at the previously optimized concentration of 10 ppm along with a non–ionic surfactant is employed for jet impingement cooling. The steel plate (100 × 100 × 6 mm) is cooled from an initial surface temperature of 900 °C. The concentration of non-ionic surfactant polyoxyethylene (20) sorbitan monolaurate (Tween 20) is optimized, and the surfactant is characterized based on its thermal properties. A maximum thermal conductivity enhancement of 21% and a minimum contact angle of 40.48° were exhibited by surfactant added nanofluid at 55 ppm. Inverse heat conduction method was employed to estimate the heat flux and temperature at the plate surface based on the internal thermocouple data. A maximum heat transfer rate of 139 °C/s with a critical heat flux (CHF) of 2.93 MW/m 2 was attained at a surfactant concentration of 55 ppm. SEM and EDAX analysis of the plate surface after jet impingement confirmed the presence of the nanoparticles.

The current study comprises of the synthesis and characterization of Zn-Al layered double hydroxide (LDH) nanofluid for use as a potential coolant in the steel industry. Coprecipitation method was used in the preparation of Zn-Al LDH nanoparticles by using the nitrate salts of Zn, Al and Na, in the ratio of 2:1:2. The nanofluids were characterized based on their particle size, stability, surface tension, thermal conductivity and viscosity. TEM analysis revealed that the nanoparticles were needle-shaped with an average particle size of 45.61 nm and aspect ratio of 7.3. Different concentrations of the nanofluid, from 40 ppm to 240 ppm, were used to analyze the effect of particle concentration on the enhancement in thermal conductivity and viscosity. Stability analysis of the nanofluid exhibited good results, even without any stabilizer. An optimum cooling rate of 125 °C/s was obtained for a nanofluid concentration of 160 ppm, which is 1.29 times when compared to water.

The current work contains a detailed experimental investigation on the alteration of heat transfer characteristics during jet impingement cooling of a hot steel plate using Copper-Aluminium layered double hydroxide (Cu-Al LDH) nanoparticle as an additive. The experiments have been performed on steel plate having initial surface temperature well above the Leidenfrost point. A new breed of nanoparticle named Cu-Al LDH has been prepared via co-precipitation method and the effect of its concentrations on surface tension, thermal conductivity and viscosity have been studied. The results show that the cooling rate increases with the increasing concentration of nanoparticle in coolant upto an optimum level beyond which it declines. A maximum cooling rate of 154 °C/s has been achieved at a nanoparticle concentration of 120 ppm which is 41% higher than that obtained with pure water. The study reveals that ultrafast cooling rate can be achieved by Cu-Al LDH nanofluid jet which is essential for the production of high strength steel for various industrial applications.

The current research is focused on the cooling of a hot moving steel plate by using air atomized spray cooling technique. A new type of coolant, Cu-Al LDH nanofluid, has been prepared and used for heat flux removal. Preparation method of nanofluid and its characteristics has been reported. The cooling effectiveness is reported in terms of cooling rate by varying the concentration of nanofluid in five levels. The results indicate that the cooling rate increases at very low concentration of LDH with respect to base fluid. However, beyond a certain concentration a decreasing trend of cooling rate has been observed.Abbreviations: CHF: Critical heat flux; HTC: Heat transfer coefficients; LDH:Layered double hydroxide; TEM: Transmission electron microscopy.

In the current work, TiO2 nanofluid has been synthesized via two-step co-precipitation method. TEM analysis has been carried out to measure the average particle size and to check the particle distributions which confirm the formation of a suspension having an average particle size of

The research work was achieved to optimize the experimentally determined thermophysical properties of water based nanodiamond nanofluids using the Adaptive network-based fuzzy inference system model. The thermophysical properties were determined at various temperatures (20 °C to 60 °C) and various particle volume concentrations (0.2% to 1.0%). The stability of nanodiamond nanofluids was measured based on the dynamic light scattering method. Results indicated that the zeta potential of all the prepared nanodiamond/water nanofluids is above −30 mV. The thermophysical properties like thermal conductivity and viscosity augments are 22.86% and 79.16% at ϕ = 1.0 vol% compared to the water data at a temperature of 60 °C. Fuzzy logic is one of the artificial intelligence tools that have been used to analyze the optimized property value. The optimization process was applied in a single objective and a multi-objective procedure using a new and efficient optimizer, namely, the marine predators' algorithm. In a single objective, the lowest density and highest thermal conductivity values were found at 0.23% with 54.81o C and 1% with 60 °C, respectively. However, the viscosity and specific heat showed improvements only in the absence of the nanodiamond material and temperatures of 35.99 and 60 °C, respectively. In the multi-objective process, the optimizer confirmed that the thermophysical properties' optimal values could be obtained when no nanomaterial was added, and the best values were found at a temperature of 59.48 °C. This optimal point is found as close to the experimental data.

Droplet impact dynamics on super-hydrophobic micro-structured surfaces is vital in a multitude of processes such as spray coating, cooling, and inkjet printing etc. Majority of the research has been focused on the rebound phenomena while partial rebound is relatively underreported. Recent studies indicate that partial rebound is encountered where transition of wetting state may take place on super-hydrophobic surfaces. Herein, we report that satellite drops are formed during partial rebound of droplets even on hydrophobic surfaces with unidirectional topography created using a mask-less and stamp-less fabrication process. The simultaneous capillary driven retraction along the wrinkles and the strong contact line pinning across these anisotropic substrates leads to formation of satellite drops on hydrophobic surfaces. Excess rebound energy has been evaluated as functions of contact angle, contact angle hysteresis and the maximum spreading diameter to explain partial rebound on such surfaces with potential applications in the design of novel, functional surfaces.

Low thermal conductivity has been found to be a major constraint in developing energy efficient heat transfer fluids in several industrial applications. Nanofluids, prepared by the suspension of nanoparticles in water, have been found to enhance the thermal conductivity of the base fluid, and thereby the cooling rate of the steel surface. In this study, alumina nanofluid has been used to enhance the rate of cooling of a steel surface of dimension 100 mm × 100 mm × 6 mm, from an initial surface temperature of 900 °C. The sub-surface temperature data collected through thermocouple was used for inverse heat conduction calculation in order to estimate the temperature histories and heat flux at the surface. TEM analysis revealed that the nanoparticles were spherical in shape, having an average size of 14 nm. The concentration of the nanofluids was varied from 1 to 20 ppm in this study. A maximum cooling rate of 104 °C/s and critical heat flux (CHF) of 2.10 MW/m2 was obtained for a concentration of 10 ppm, which was 1.2 times and 1.5 times that attained in case of pure water, as depicted by the enhancement in thermal conductivity. Lower concentrations are used in order to strike a balance between surface roughness study and cooling applications. The surface roughness of the plate after the nanofluid jet impingement depicted an enhancement of 7.74%, thereby enhancing the number of nucleation sites and augmenting the value of CHF.

The cooling rate of steel strips on a Run-out Table (ROT) in a hot strip mill affects both the metallurgical microstructure and mechanical properties. The current study focuses on the enhancement of heat transfer rate of an AISI 304 steel plate in both transition and nucleate boiling regimes by jet impingement methodology. The heat transfer studies during jet impingement have been carried out in the case of a steel plate (100 mm × 100 mm × 6 mm) from an initial temperature of around 900 °C at the surface. Nanofluid is used along with the base fluid in order to improve the thermal properties which affect the rate of heat transfer. The nanofluid employed here is Cu–Al layered double hydroxide (LDH) at 120 ppm along with different additives at their optimized concentrations, namely sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), polyoxyethylene (20) sorbitan monolaurate (Tween 20) and polyvinylpyrrolidone (PVP). The nanofluid based additives have been characterized based on the thermo physical properties. The maximum rate of cooling was attained in the case of Cu–Al LDH/Tween 20 nanofluid, as supported by the enhancement of thermal conductivity and reduction in surface tension.

This article addresses the synthesis of organically tailored Ni-Al layered double hydroxide (ONi-Al LDH) and its use in the fabrication of exfoliated poly(methyl methacrylate) (PMMA) nanocomposites. The pristine Ni-Al LDH was initially synthesized by co-precipitation method and subsequently modified using sodium dodecyl sulfate to obtain ONi-Al LDH. Nanocomposites of PMMA containing various amounts of modified Ni-Al LDH (3 wt%-7 wt%) were synthesized via solvent blending method to investigate the influence of LDH content on the properties of PMMA matrix. Several characterization methods such as X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), rheological analysis, differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA), were employed to examine the structural, viscoelastic and thermal properties of PMMA/OLDH nanocomposites. The results of XRD and TEM examination confirm the formation of partially exfoliated PMMA/OLDH nanocomposites. The FTIR results elucidate that the characteristic bands for both pure PMMA and modified LDH are present in the spectra of PMMA/OLDH nanocomposites. Rheological analyses were carried out to examine the adhesion between polymer matrix and fillers present in the nanocomposite sample. The TGA data indicate that the PMMA nanocomposites exhibit higher thermal stability when compared to pure PMMA. The thermal decomposition temperature of PMMA/OLDH nanocomposites increases by 28 K compared to that of pure PMMA at 15% weight loss as a point of reference. In comparison with pure PMMA, the PMMA nanocomposite containing 7 wt% LDH demonstrates improved glass transition temperature (Tg) of around 3 K. The activation energy (Ea), reaction orders (n) and reaction mechanism of thermal degradation of PMMA/OLDH nanocomposites were evaluated using different kinetic models. Water uptake capacity of the PMMA/OLDH nanocomposites is less than that of the pure PMMA.

Nanofluid is a suspension of nanoparticles (at least one dimension less than 100 nm) in a basefluid having superior thermal, rheological and wettability properties, which improves the performance of several applications i.e. heat transfer, lubrication, drug delivery and enhanced oil recovery etc. However, the critical bottleneck for widespread use of nanofluid is its stability. The instability of nanofluid leads to reduction in system performance with passage of time. Addressing the long term stability of nanofluid and its reusability are essential requirements for successful industrial use. This article focuses on different aspects of nanofluid stability starting from the preparation stage till implementation in practical applications. Specific attention has been given on nanofluid stability as a function of operating conditions i.e. high temperature, pressure, confinement, composition, salinity, external magnetic field and shear rate etc. in several applications i.e. heat transfer, microfluidics, lubrication, enhanced oil recovery and drag reduction etc. It is expected that the present review will provide guidance and contribute towards wider adoption of nanofluid in practical applications. Future research on stability issues related to techno-economic performance, hybrid nanofluid, quantum dot, hybrid stabilization technique, wall effect in microfluidics and porous media will further enhance the usability of nanofluid in widespread practical systems.

Synthesis of pristine Cu–Al layered double hydroxide (LDH) nanofluid via one step method and study of its thermal properties are the core essence of the current work. Nitrate salts of Cu, Al and Na were mixed in a particular molar ratio at constant pH to produce desired Cu–Al LDH. Different dispersion techniques were utilized to uniformly disperse Cu-Al LDH in water to obtain Cu–Al LDH nanofluids. Broadly used characterization techniques were implemented to identify and characterize pristine Cu–Al LDH nanoparticle. These techniques were used to determine crystallite size, composition, morphology and characteristics vibration of interlayer anion present in the nanoparticle. The nanofluids were characterized for particle size, cluster size, surface tension and thermal conductivity. Particle size analysis was carried out to confirm the formation of nanofluid. Dynamic light scattering (DLS) method had been employed to measure the clustering tendency of nanofluid. Effect of nanofluid loading on thermal conductivity was studied in depth. Influence of particle size, shape and composition on thermal conductivity of nanofluid had also been selected as an essential topic of investigation. Zeta potential and visual phase separation study were carried out to measure the stability of concerned nanofluid.

This work deals with the synthesis of organically modified Ni Al layered double hydroxide (LDH) and the effect of Ni Al LDH loading on the rheological behavior of PMMA/Ni Al LDH blends prepared by solvent blending method. Firstly, Ni Al LDH was synthesized by co-precipitation method at constant pH using their nitrate salts and subsequently modified using sodium dodecyl sulfate (SDS). Then, PMMA blends with various LDHs content (3 and 5 wt.% with respect to PMMA) were prepared by solvent blending method using methylene chloride as a solvent. The structural properties of the modified Ni Al LDH were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and FTIR analysis. The XRD analysis reveals that the d-spacing value of the modified LDH increases to 1.35 nm from 0.80 nm for the unmodified LDH, which confirms the insertion of SDS molecules into the Ni Al LDH interlayers. The presence of sulfate groups in the modified LDH is confirmed by FTIR analysis. The rheological characteristics of PMMA/Ni Al LDH blends were performed on rotational rheometer using HAAKE Rheostress RS1 with cup and cylinder geometry at room temperature. It is observed that the rheology of PMMA blends is affected by increasing LDH loading as well as shear rate. All the PMMA/LDH blends exhibit enhanced shear viscosity as compared to neat PMMA. In addition, the obtained rheological data are fitted with various models, like Power law, Herschel–Bulkley, Casson, Sisko, Cross, and Carreau models to explain the rheological behavior. The results clearly indicate that the Herschel–Bulkley model fits the rheological data better than other models.

The focus of the current study is to investigate the influence of Co–Al layered double hydroxide (LDH) on the morphological, thermal, and mechanical features of poly(methyl methacrylate) (PMMA)-based nanocomposites. Sodium dodecyl sulfate modified Co–Al LDH was synthesized by single step coagulation method. The PMMA nanocomposites containing different loadings of nanofiller (1–7 wt %) and polystyrene-grafted maleic anhydride compatibilizer (5 wt %) were melt intercalated via twin screw extruder and later subjected to injection molding to prepare mechanical testing samples. The different properties of PMMA nanocomposites were studied by using XRD, TEM, FTIR, DSC, TGA, tensile, flexural, impact, and flammability analysis. The result of XRD analysis suggested the exfoliated morphology of the nanocomposite while the TEM demonstrated the intercalated structure at higher loading of LDH. The thermal characterization results revealed that thermal properties were improved by the addition of Co–Al LDH, whereas the flammability test exposed that dripping was minimum at 7 wt % loading. The mechanical properties exhibited that optimum results were obtained at 1 wt % loading of Co–Al LDH. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45774.