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In the present study, titanium oxide-copper oxide/carbon (TiO 2 -CuO/C) nanocomposite particles have been prepared via wet-mixing protocol. The nanocomposite was characterized by using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray powder diffraction (XRD). Subsequently, hybrid nanofluids were prepared by dispersing the nanocomposite in ethylene glycol (EG) as a base liquid. The thermal conductivity and viscosity of the nanofluids was measured in various volume concentrations (0.5, 1.0, 1.5, and 2%) and temperatures ranging from 303.15 K to 333.15 K. The experimental results showed the sensitivity of thermal conductivity and viscosity with respect to variations in volume concentration and temperature. The maximum enhancement of thermal conductivity of TiO 2 -CuO/C hybrid nanofluid is 16.7%, while the viscosity increased nearly by 80% at 2.0% volume concentration compared to base liquid at 313.4 K. The rheological analysis established that the hybrid nanofluid conforms to Newtonian classification of fluids. Finally, correlations for thermal conductivity and viscosity of nanocomposite based hybrid nanofluids were formulated which represent a satisfactory agreement between the experimental and calculated data with average absolute deviation ranging from 1% to 4%.

Thermal conductivity and viscosity of the Al2O3-SiO2/PAG composite nanolubricants for 0.02 to 0.1% volume concentrations at a temperature range of 303 to 353 K were investigated. Al2O3 and SiO2 nanoparticles were dispersed in the Polyalkylene Glycol (PAG 46) lubricant using the two-step method of preparation. Thermal conductivity and viscosity were measured using KD2 Pro Thermal Properties Analyzer and LVDV-III Rheometer, respectively. The result shows that the thermal conductivity and viscosity of composite nanolubricants increase with volume concentration and decreases with temperature. Composite nanolubricants behave as Newtonian in the range of the temperatures and volume concentrations studied. The highest thermal conductivity increment is 2.41% at 0.1% concentration and temperature of 303 K. A maximum value of 9.71% in viscosity at 0.1% concentration is observed at temperature of 333 K. A new correlation model to predict the properties of composite nanolubricants has been proposed for applications in refrigeration systems.

In this paper, laminar nanofluid flow in 3D copper microchannel heat sink (MCHS) with rectangular cross section, and a constant heat flux, has been treated numerically using the computational fluid dynamics software (FLUENT). Results for the temperature and velocity distributions in the investigated MCHS are presented. In addition, experimental and numerical values are compared in terms of friction factors, convective heat transfer coefficients, wall temperature and pressure drops, for various particle volume concentrations and Reynolds numbers. The numerical results show that enhancing the heat flux has a very weak effect on the heat transfer coefficient for pure water, but an appreciable effect for the case of a nanofluid. For all considered volume fractions, the sink friction factor decreases by increasing the Reynolds number and slightly increases by increasing the volume fractions, and, with increasing the volume fractions and the Reynolds number, the pressure drop increases.

Nanofluids are developed to meet the challenges of improving the efficiency of the cooling system subsequently minimizing the energy waste. This paper aims to investigate the forced convection heat transfer for Al2O3 nanofluids in different based ratio of water (W) and ethylene glycol (EG) mixture. The Al2O3 nanofluids are formulated using the two-step method for three based mixture ratio of 60:40, 50:50 and 40:60 (W:EG) by volume. The forced convection experiments are conducted under constant heat flux conditions for operating temperatures of 30–70 °C and Reynolds numbers of 3000–25,000. The heat transfer coefficient of nanofluids is enhanced with concentration compare to its base fluid at all designated temperature. It is observed to be improved further with the increase of temperature. The effect of different base mixture ratio display that nanofluids in 60:40 base mixture have the highest percentage of performance with 24.6% enhancement at 1.0% concentration and temperature of 70 °C. The increment of concentration for nanofluids shows a slight rise in friction factor. As a conclusion, the thermo-physical properties and the forced convection heat transfer for nanofluids in various base mixture is significantly influenced by concentration, temperature and base ratio of mixture.

In the past decade, research on nanofluids has been increased rapidly and reports reveal that nanofluids are beneficial heat transfer fluids for engineering applications. The heat transfer enhancement of nanofluids is primarily dependent on thermal conductivity of nanoparticles, particle volume concentrations and mass flow rates. Under constant particle volume concentrations and flow rates, the heat transfer enhancement only depends on the thermal conductivity of the nanoparticles. The thermal conductivity of nanoparticles may be altered or changed by preparing hybrid (composite) nanoparticles. Hybrid nanoparticles are defined as nanoparticles composed by two or more different materials of nanometer size. The fluids prepared with hybrid nanoparticles are known as hybrid nanofluids. The motivation for the preparation of hybrid nanofluids is to obtain further heat transfer enhancement with augmented thermal conductivity of these nanofluids. This review covers the synthesis of hybrid nanoparticles, preparation of hybrid nanofluids, thermal properties, heat transfer, friction factor and the available Nusselt number and friction factor correlations. The review also demonstrates that hybrid nanofluids are more effective heat transfer fluids than single nanoparticles based nanofluids or conventional fluids. Notwithstanding, full understanding of the mechanisms associated with heat transfer enhancement of hybrid nanofluids is still lacking and, consequently it is required a considerable research effort in this area.

The limitation of the conventional fluids to facilitate cooling/heating rates remains the primary basis for exploring alternative heat transfer nanofluids. Research efforts on nanofluids have evolved over the past two decades in establishing extensive literature. Several models for thermophysical properties were made available to characterize the behaviors of diverse individual nanofluids. However, lack of reasonable agreement between theory and experimental results has been a limiting factor for the development of a unified nanofluid model for thermal conductivity. Existing models for thermo-physical properties of nanofluids such as density, specific heat, thermal conductivity, and viscosity are critically surveyed and appropriate equations are extended for composite nanofluids. Consequently, based on reliable models identified predictions for thermal conductivity and viscosity for composite nanofluids are presented. Overall results show that existing thermophysical models for density and specific heat are valid for all water based oxide nanofluids for both single material and composites whereas models for thermal conductivity and viscosity show selective response but have the versatility for predicting the behavior of single and composite nanofluids within acceptable deviation.

From a regression analysis perspective, this paper focused on literature about TiO2 nano particles. The particles on focus entailed those that had been suspended in ethylene glycol and water – at a ratio of 60:40. Indeed, regression analysis has gained application in contexts such as the turbulent Reynolds number, especially with the aim of establishing the impact of the ratio of the base fluid on heat transfer coefficients, as well as the target materials’ thermal properties. From the findings, this study infers that when the water-ethylene glycol mixture is used at a ratio of 60:40, the rate of heat transfer is higher than that which is obtained when water is used solely. Additional findings established from the examination of the impact of material concentration and temperature on the rate of nanofluids’ heat transfer suggested that as temperature increases, the rate of heat transfer decreases. However, it was noted that an increase in concentration exhibits a positive correlation with the nanofluids’ rate of heat transfer whereby an increase in the former parameter (concentration) leads to an increase in the latter (rate of nanofluids heat transfer).

The objective of the present work is to evaluate the experimental convective heat transfer coefficient and friction factor of the nanofluids flowing through a copper tube under a uniform heat flux of 7962 W/m2. Water-based stable fly ash and fly ash– Cu (80:20% by vol.) hybrid nanofluids were used as working fluids in the concentration range of 0.5 to 2.0 vol%. Experiments in the Reynolds number range of 6800 to 45,200 were performed at fluid inlet temperatures in the temperature range of 30 to 60 °C. The findings suggest that compared to water and fly ash nanofluid, thermal conductivity, viscosity, and the heat transfer rate of hybrid nanofluid is higher. At fluid inlet temperature of 60 °C, the maximum Nusselt number augmentation for fly ash-Cu hybrid nanofluid is 15.6% and 93.5% was observed at a concentration of 2.0% compared to fly ash nanofluid and water, respectively. A maximum thermal performance factor of 1.65 and 1.87 is observed for fly ash and hybrid nanofluid respectively at 60 °C with a 2.0% volume concentration. Correlations for evaluating the Nusselt number and friction factor of hybrid nanofluid were developed with the experimental data.

The current numerical study is aimed to examine the forced convection heat transfer of fly ash-Copper (80:20% by volume) water-based hybrid nanofluids flowing in a horizontal circular copper tube under a constant heat flux of 7962W/m2 using STAR CCM+ software. The volume concentrations of 0.5% and 1% are considered for the analysis within the Reynolds number range of 6900-26500. The findings show that the heat transfer coefficient and the Nusselt number of hybrid nanofluid at a concentration of 1 vol.% are increased by about 66.0% and 36.67% compared to that of water.

STAR CCM+ software is used to investigate the forced convection heat transfer of fly ash/Water nanofluids flowing through a horizontal circular tube in the turbulent flow regime under the constant heat flux of 707 W/m2. The volume concentrations of nanofluid are 0.3, 0.5, 1.0, and 1.5 vol. %, used in this analysis. The results revealed that both the Reynolds number and concentration intensify the Nusselt number of fly ash nanofluids. The highest heat transfer coefficient augmentation is about ∼60% observed at 1.5% concentration in comparison to the water.

The article presents the heat transfer coefficient and the friction factor for the flow of water-base fly ash nanofluid in the concentration range of 0.5 to 2.0 vol%. Experiments are undertaken for flow in a horizontal copper tube subject to uniform heat flux in the Reynolds number range of 7000 to 45,200, for inlet fluid temperatures of 30, 45, and 60°C. The results revealed that in contrast to base fluid, nanofluids exhibit greater heat transfer coefficients which increase with concentration and fluid inlet temperatures due to augmentation in nanofluid thermal conductivity. The maximum amplification in Nusselt number and pressure drop of 67.4% and 11.9% are observed with 2% nanofluid concentration as compared to base liquid, for an inlet fluid temperature of 60°C and 30°C respectively. The values of Efficiency Index (EI) are evaluated for different concentrations and inlet fluid temperatures. Correlations are reported based on the experimental data for the estimation of dynamic viscosity, thermal conductivity, Nusselt number, and the friction factor of fly ash nanofluid.

In the present work, medium density fiberboard (MDF) panels were produced using multiwalled carbon nanotubes (MWCNT) reinforced urea formaldehyde resin. Response surface methodology was employed to optimize the relationship between the three variables, viz. pressing time, percentage of UF resin and percentage of MWCNT, used in the fabrication of MDF, and the influence of variables on the internal bonding (IB) and modulus of rupture (MOR) was studied. The optimum conditions based on the IB strength were determined as 8.18 % of UF resin, pressing time of 232 s, and MWCNT of 3.5 %. Similarly, the optimized conditions for MOR are also reported in this paper.

Nanofluids as a new coolant have overcome the limitations in thermal performance faced by conventional fluids such as water, ethylene glycol (EG) and oil based fluids. The objective of the study is to investigate the properties and heat transfer performance of TiO2 nanofluids in water-EG mixture at different operating temperatures. The study is carried out through experimental determination on heat transfer coefficient of TiO2 nanofluids in a circular tube under turbulent flow. The thermal conductivity and viscosity measurements were undertaken for temperature in the range of 30–80 °C. The maximum enhancement of thermal conductivity achieved was 15.4% at 1.5 vol% concentration and temperature of 60 °C. The relative viscosities fluctuate at a range of 4.6–33.3% with variation of temperature. The Nusselt number showed an enhancement up to 22.8% and 28.9% for temperatures of 50 °C and 70 °C, respectively. The friction factor for the nanofluids is slightly increased with concentration. Thermal conductivity, viscosity and heat transfer coefficient of TiO2 nanofluid are strongly influenced by working temperature and concentration.

This paper introduces the historical background about the development of water based, ethylene glycol (EG) based and EG:water mixture nanofluids for the past 20 years. The primary consideration is to review the salient of research work related to EG:water mixture nanofluids and their applications. Nowadays, the fundamental studies of nanofluids are increasing rapidly for engineering applications. The determination of the forced convection heat transfer and pressure drop was reviewed for nanofluid flow in a tube. The experimental and numerical heat transfers of nanofluids were presented. A review of other relevant research studies is also provided. Substantial heat transfer literature has been studied on water based nanofluids used in the fundamental study for engineering applications. However, there are limited studies that use EG:water mixture nanofluids in evaluation of forced convection heat transfer. A number of research studies have been performed to investigate the transport properties of EG:water mixture nanofluids either in experimental or numerical approach. As the performance of EG:water mixture nanofluids could be verified through experimental studies, researchers have conducted the experimental works using several types of potential nanofluids. As a result, nanofluids have been used in certain engineering applications such as in automotive, transportation, cooling of electronics components, solar, and nuclear reactor coolant.

Nanofluid as a new brand of cooling fluid consisting of nanometer-sized particles dispersed in base fluid. In this study, the thermal conductivity and electrical conductivity of BioGlycol (BG)–water (W) mixed nanofluids containing Al 2 O 3 nanoparticles were studied. Nanofluids with 0.5–2.0% concentrations were prepared by the two-step method. The nanofluids demonstrated excellent stability over the temperature range of 30–80 °C after using the long term sonication process. Comparisons of the experimental data with many existing models illustrated that they do not display good agreement. Therefore, a new nonlinear model has been developed with 5% maximum deviation for the thermal conductivity of nanofluids as a function of temperature and volume concentration. The results of BG:W mixtures have displayed improvement in thermal performance of 7.5% in comparison with propylene glycol (PG):W in similar circumstances. The thermal conductivity of nanofluid increased as a function of volume concentration and temperature. The maximum thermal conductivity enhancement using 40:60% (BG:W) mixture ratio was twice as high as 60:40% in the same conditions. Electrical conductivity was observed to decrease as the volume concentration increased. Thermo-electrical conductivity ratio (TEC) has been evaluated theoretically based on thermal and electrical conductivity results.

The use of nanofluids is essential in heat transfer study due to its effective performance. The performance of nanofluids in mixture based fluids is yet to be explored hence; the study was carried out to provide a wider knowledge and information on heat transfer performance of TiO 2 nanofluids. The forced convection heat transfer is conducted at Reynolds number of 3000 to 24,000 under constant heat flux boundary conditions. The TiO 2 nanofluid is prepared at 0.5 to 1.5% volume concentration and the thermal conductivity and dynamic viscosity were measured for 30 to 70 °C. The heat transfer performance was evaluated at three different bulk temperatures for its heat transfer coefficient and friction factor; 30, 50 and 70 °C. The thermal conductivity and viscosity enhanced with the increase in volume concentration. The heat transfer performance for temperature at 30 °C experienced low enhancement compared to the base fluid when the nanofluid concentration was less than 1.2%. However, at temperatures of 50 and 70 °C for all volume concentrations, the heat transfer performance improved with a value of h ′ greater than 1. As the working temperature increased, the enhancement became more noticeable for higher concentrations. The friction factor of TiO 2 nanofluids is slightly increased with the increase of concentration at approximately 1.1 times of base fluid. The performance factor, h ′ of the TiO 2 nanofluids is significantly influenced by the thermal properties, concentration, temperature, and Reynolds number.

The determination of thermo-physical properties and especially thermal conductivity and viscosity were important for evaluating heat transfer coefficients either for single or two phase flow. The thermo-physical properties measurements and heat transfer observations were mostly obtained with nanoparticles above 10 nm. Various researchers measured and modelled for the determination of thermal conductivity and viscosity of nanofluids. Most of the investigators developed equations for the estimation of thermal conductivity and viscosity as a function of percentage volume concentration, temperature and sometimes with the consideration of particle size valid in their experimental range. Nanofluids are considered to have great potential for heat transfer enhancement and are applied in heat transfer processes. Many studies were carried out to investigate this phenomenon. The main aim of this study is to give a comprehensive review on the research progress on the enhancement of effective thermal conductivity and effective dynamic viscosity of nanofluids.

Nanofluids are a new class of engineered thermal fluids with enhanced thermal properties and heat transfer capabilities exceeding those of the base liquid. Studies related to the effect of temperature on the thermophysical and rheological properties of ethylene glycol and glycerol nanofluids have been documented in various articles. In this paper, the thermal and physio-chemical behavior of SiC nanofluid dispersed in glycerol and ethylene mixture of 60:40 wt.% ratio was determined. The influence of temperature on the p H, viscosity, electrical and thermal conductivity of nanofluid was undertaken for a maximum concentration of 1.0 vol.% in the temperature range of 15-75 o C. It was found that, the base liquid electrical conductivity and p H were unaffected by temperature; whereas the nanofluid electrical and thermal conductivity increased with temperature. The viscosity of the base liquid and nanofluid decreased significantly while the decrease in p H is not significant with temperature.

A numerical model for determining the characteristics of flow and heat has been presented by modifying the eddy diffusivity equation of Sarma et al. The experimental data of thermo-physical properties determined using spherical particles in a wide range of concentration, particle size, materials and operating temperatures are available in the literature. The numerical analysis employed equations, which were developed using the experimental data of thermo-physical properties, friction factor and Nusselt number. Based on the agreement of the numerical results with the experimental data, the influence of concentration and temperature on the turbulent characteristics is presented. It is observed that SiO2 nanofluid attained higher velocity and lower eddy diffusivity compared to Cu nanofluid at a concentration. The temperature gradient increases with concentration and decreases with temperature.

Emerging nanotechnology with solar collector technology has attracted the attention of researchers to enhance the performance of solar systems in order to develop efficient solar thermal systems for future sustainability. This paper chronologically reviews the various research works carried out on the performance enhancement of nanofluid-filled flat-plate solar collectors (FPCs). Gaps in the radiation exergy models and maximum exergy of FPCs, the importance of pressure drops in collector manifolds in exergy analysis, and the economics of nanofluid-laden FPCs have been addressed. The necessity of replacing currently used chemically derived glycol products with a renewable-based glycol has not been reported in the current literature thoroughly, but it is pondered in the current paper. Moreover, the thermophysical properties of all common metal and metal oxide nanoparticles utilized in various studies are collected in this paper for the first time and can be referred to quickly as a data source for future studies. The different classical empirical correlations for the estimation of specific heat, density, conductivity, and viscosity of reported nanofluids and base liquids, i.e., water and its mixture with glycols, are also tabulated as a quick reference. Brief insights on different performance criteria and the utilized models of heat transfer, energy efficiency, exergy efficiency, and economic calculation of nanofluid-based FPCs are extracted. Most importantly, a summary of the current progress in the field of nanofluid-charged FPCs is presented appropriately within two tables. The tables contain the status of the main parameters in different research works. Finally, gaps in the literature are addressed and mitigation approaches are suggested for the future sustainability of nanofluid-laden FPCs.

In previous scholarly studies, the water and ethylene glycol mixtures as base liquids have been considered in the ratio of 40:60 (60EGW), with specific investigations focusing on a nanofluid in the form of Silicon dioxide (SiO2) in relation to its thermo-physical properties, besides its nature of the heat transfer coefficients (HTC). In this study, the main aim lies in SiO2 heat transfer coefficient prediction. With the approach of computational fluid dynamics (CFD) considered, the experimental conditions constitute 40EGW. For SiO2 nanoparticles, their viscosity and thermal conductivity are experimentally assessed, having been dispersed in 60EGW and 40EGW. Also, the existing literature and experimental values are used to conduct regression analysis. With thermal features on the focus, there is also the formulation of correlations. Furthermore, there is the invocation of correlations in heat transfer coefficients and CFD simulations that target Al2O 3 and SiO 2 nanoparticles, with predictions entailing their dispersion in 40EGW and 60EGW base fluids. The inlet temperature is set at 60 to 80 °C, and it is at this stage that there is CFD simulation implementation. For the volume concentration, the ranges include 0.0 percent to 1.5 percent. The existing literature is relied upon relative to the validation of the coefficients of heat transfer, besides previously predicted nanofluids. From the results, compared to the case of 40EGW base fluid, there is 51 percent and 53 percent enhancement when the experimental conditions are set at 1.0 percent volume concentration, with temperatures being 80 °C. From the computational outcomes, Al2O3/40EGW nanofluids tend to be associated with significant heat transfer coefficients. Specifically, the enhancement of heat transfer for these materials stands at 52.9%. On the other hand, the enhancement of heat transfer when the base fluid of SiO2/40EGW is considered stands at 51.0%. These values are obtained when the experimental conditions are considered at 80 °C, as well as a volume concentration of 1.0%. Therefore, when aspects of heat transfer coefficients and thermal conductivity are considered, the superiority of 40EGW is confirmed. As such, the study confirms the impact of the base nanofluids set at 40EGW relative to the coefficients of heat transfer and also the thermal properties of materials.

This paper involves a numerical study of several water – ionic liquids mixtures and nanoparticle enhanced ionic liquids starting from a less studied ionic liquid: 1-Ethyl-3-methylimidazolium Methanesulfonate, [C2mim][CH3SO3]. The research start point was several previous published experimental results in regard to the water – ionic liquid mixtures and alumina based nanoparticle enhanced ionic liquids thermophysical properties. Consequently, all the considered fluids are completely described and can be successfully implemented in a numerical analysis using the single phase approach. The numerical analysis was performed in a cylindrical enclosure considering laminar steady state and results were collected in terms of Nusselt number, convective heat transfer coefficient, pressure drop and temperature on tube exit. Results were discussed in terms of heat transfer enhancement and pumping power requirement variation, as well as field synergy. Concluding, it can clearly say that mixing water with [C2mim][CH3SO3] ionic liquid it gets a decrease in laminar convective heat transfer coefficient, while adding nanoparticles the heat transfer is enhanced by maximum 50%, depending on the alumina mass concentration.

Ethylene glycol and propylene glycol are commonly used as thermal liquids in solar flat-plate collectors (FPCs). They are utilized as base liquid as well as for improving the stability of nanofluids in FPCs. The objective of the present paper is to introduce a renewable-derived bio glycol for use as base liquid in FPCs. The effect of base ratio (BR) of different glycol products on the performance of a conventional FPC and a nanofluidladen FPC is investigated in this paper to determine its suitability. MATLAB programming was employed for modeling the performance of the FPC operating with copper and cerium oxide nanomaterials. The results show that 20:80 bio glycol/water mixture is capable of enhancing the FPC’s energetic efficiency up to 72.1% which is higher than with either ethylene glycol and propylene glycol. The energy efficiency of a glycol-based nanofluid-filled FPC decreases with the base ratio of all three glycol products. Since bio glycol is a non-toxic and safe product, it can be utilized as a safe and environmentally-friend antifreeze and base liquid in nanofluid-filled FPCs.

The solar flat plate collector operating under different convective modes has low efficiency for energy conversion. The energy absorbed by the working fluid in the collector system and its heat transfer characteristics vary with solar insolation and mass flow rate. The performance of the system is improved by reducing the losses from the collector. Various passive methods have been devised to aid energy absorption by the working fluid. Also, working fluids are modified using nanoparticles to improve the thermal properties of the fluid. In the present work, simulation and experimental studies are undertaken for pipe flow at constant heat flux boundary condition in the mixed convection mode. The working fluid at low Reynolds number in the mixed laminar flow range is undertaken with water in thermosyphon mode for different inclination angles of the tube. Local and average coefficients are determined experimentally and compared with theoretical values for water-based Al2O3 nanofluids. The results show an enhancement in heat transfer in the experimental range with Rayleigh number at higher inclinations of the collector tube for water and nanofluids.

Coal is an attractive fuel owing to its low price linked to its worldwide availability but combustion of coal generates very corrosive media especially near the superheater tubes. The present investigation is an attempt to evaluate the hot corrosion behavior of detonation-gun sprayed coatings of Cr3C2–NiCr, NiCrAlY + 0.4 wt% CeO2, and NiCoCrAlYTa on superfer 800H, exposed to low temperature super-heater zone of the coal-fired boiler. The specimens were hanged in the platen super-heater of coal-fired boiler where the gas temperature was around 900 °C ± 10 °C. Hot corrosion experiments were performed for 10 cycles, each cycle consisting of 100 h exposure followed by 1 h cooling at ambient temperature. All three coatings deposited on superfer 800H imparted better hot corrosion resistance than the bare uncoated one. The Cr3C2–NiCr coated superalloy performed better than the other two coatings in the given boiler environment.

Catalyst-free carbon nanospheres were synthesized using simple one-step pyrolysis techniques where biowaste sago bark is used as a carbon precursor. Obtained carbon nanospheres showed a porous nature and revealed that more than 95% carbon is present in the synthesized carbon nanospheres with particle size ranging from 40 to 70 nm. An electrochemical study showed a specific capacitance value of 180 F g–1 at 2 mV s–1 and the cycling stability up to 1700 cycles. Obtained carbon nanospheres are useful in supercapacitor applications. The presented study revealed a waste to wealth approach thereby reducing waste in the environment.

This paper discuss the tool life and wear mechanism in the end-milling of AISI304 stainless steel using a TiN-coated carbide insert with water-soluble coolant and nanoparticle-based coolant (TiO2/EG). The cutting variables are cutting speed, feed rate, and axial depth. The end-milling operation using nanoparticle-based coolant (TiO2/EG) obtains a high tool life compared with the end-milling operation using water-soluble coolant. In general, the tool failure when milling with water-soluble coolant was flank wear, cracking, chipping, and fracture at a cutting distance of 720 mm, but the milling process with nanoparticle-based coolant (TiO2/EG) showed chipping and fracture at a cutting distance of 1200 mm. According to ISO 8688-2-1989 (E), the wear criterion for milling with water-soluble coolant is reached at an average cutting distance of 800 mm, but milling with nanoparticle-based coolant (TiO2/EG) reached the ISO 8688-2-1989 (E) wear criterion at a cutting distance of 1300 mm. The SEM and EDX spectra show that there are nanolayers of Ti nanoparticles from the nanofluid embedded in and filling the holes in the insert, forming a layer which acts as a thermal bridge for the cutting insert. Attrition and oxidation at the cutting edge were the main tool wear mechanisms present during the end-milling operation with nanoparticle-based coolant (TiO2/EG). An oxide layer formed during the oxidation wear which shielded the cutting tool from impact during the milling process.

Cities in Sub-Saharan Africa suffer from widespread disparities in water supply due to depletion in groundwater and global-warming-induced changes in weather patterns. The offset of water head from the design considerations of water pumping systems has increased energy requirements leading to worsening of the situation with respect to availability of energy and water. Consequently, highly capitalized water supply schemes, which have been designed to meet the demand, are underutilized leading to operational inefficiencies. Robust empirical equations can help detect inefficiencies in water pumping systems, and this paper discusses the equations which were developed by analysing data obtained from various water supply utilities facing water scarcity. These equations provide cost-benefit analysis for decision making in water utilities and can bring about energy efficiency in municipal pumping operations.

A single step and simple pyrolysis technique is used to prepare carbon nanospheres (CNSs) from natural biowaste sago hampas in a nitrogen atmosphere without any catalyst. Scanning electron microscope (SEM) images along with transmission electron microscope (TEM) images show evidence of high quality CNSs with a good particle size uniformity. Both X-ray diffraction (XRD) and Raman data show the presence of graphitic characteristic peaks of CNSs. Zeta-potential study reveals that the obtained CNSs can be well dispersed in solution making them suitable for cell imaging applications. The use of biowaste sago hampas is very important from the viewpoint of sustainable synthesis of functional CNSs for the future.

The heat transfer coefficient and friction factor of TiO2 and SiO2 water based nanofluids flowing in a circular tube under turbulent flow are investigated experimentally under constant heat flux boundary condition. TiO2 and SiO2 nanofluids with an average particle size of 50 nm and 22 nm respectively are used in the working fluid for volume concentrations up to 3.0%. Experiments are conducted at a bulk temperature of 30 °C in the turbulent Reynolds number range of 5000 to 25,000. The enhancements in viscosity and thermal conductivity of TiO2 are greater than SiO2 nanofluid. However, a maximum enhancement of 26% in heat transfer coefficients is obtained with TiO2 nanofluid at 1.0% concentration, while SiO2 nanofluid gave 33% enhancement at 3.0% concentration. The heat transfer coefficients are lower at all other concentrations. The particle concentration at which the nanofluids give maximum heat transfer has been determined and validated with property enhancement ratio. It is observed that the pressure drop is directly proportional to the density of the nanoparticle.

A numerical model has been developed for turbulent flow of nanofluids in a tube with twisted tape inserts. The model is based on the assumption that van Driest eddy diffusivity equation can be applied by considering the coefficient and the Prandtl index in momentum and heat respectively as a variable. The results from the numerical analysis are compared with experiments undertaken with SiO 2 /water nanofluid for a wide range of Reynolds number, Re . Generalized equation for the estimation of nanofluid friction factor and Nusselt number is proposed with the experimental data for twisted tapes. The coefficient and the Prandtl index in the eddy diffusivity equation of momentum and heat is obtained from the numerical values as a function of Reynolds number, concentration and twist ratio. An enhancement of 94.1% in heat transfer coefficient and 160% higher friction factor at Re = 19,046 is observed at a twist ratio of five with 3.0% volumetric concentration when compared to flow of water in a tube. A good agreement with the limited experimental data of other investigators is observed with Al 2 O 3 and Fe 3 O 4 nanofluids indicating the validity of the numerical model for use with twisted tape inserts.

The properties such as viscosity, thermal conductivity, specific heat, and density of nanofluids have been determined by various investigators through experiments. An equation developed for specific heat and density employing the law of mixtures is observed to be valid when compared with the experimental data. However, the experimental data of viscosity and thermal conductivity reported by investigators are observed to vary by more than 25 % for certain nanofluids. Theoretical models for the estimation of properties are yet to be developed. The nanofluid properties are essential for the comparison of heat transfer enhancement capabilities. Equations are developed for the estimation of viscosity and thermal conductivity by Corcione and Sharma et al. These equations are flexible to determine the nanofluid properties for a wide range of operating parameters which can predict the experimental data of water-based nanofluids with a maximum deviation of 12 %.

The increasing demand of nanofluids for the industrial applications has led to focus on it from many researchers in the last decade. This thesis includes both experimental study and numerical study to improve heat transfer with slightly pressure drop in the automotive cooling system. The friction factor and heat transfer enhancement using different types of nanofluids are studied. The TiO2 and SiO2 nanopowders suspended to four different base fluids (pure water, EG, 10 %EG + 90 %W, and 20 %EG + 80 %W) are prepared experimentally. The thermophysical properties of both nanofluids and base fluids are measured and validated with the standard and the experimental data available. The test section is setup including car radiator and the effects under the operating conditions on the heat transfer enhancement analyzed under laminar flow condition. The volume flowrate, inlet temperature, and nanofluid volume concentrations are in the range of (1-5LPM) for pure water and (3-12LPM) for other base fluids, (60–80 °C) and (1–4 %), respectively. On the other side, the CFD analysis for the nanofluid flow inside the flat tube of a car radiator under laminar flow is carried out. A simulation study is conducted by using the finite volume technical to solve the continuity, momentum, and energy equations. The processes of the geometry meshing of problem and describing the boundary conditions are performed in the GAMBIT then achieving of FLUENT software to find the friction factor and heat transfer coefficient. The experimental results show the friction factor decreases with the increase of the volume flowrate and increases with the nanofluid volume fraction but slightly decreases with the increase of the inlet temperature. Furthermore, the simulation results show good agreement with the experimental data with deviation, not more than 4 %. The experimental results show that the heat transfer coefficient increases with the increase in the volume flowrate, the nanofluid volume fraction, and the inlet temperature. Likewise, the simulation results show good agreement with the experimental data with deviation not more than 6 %. In addition, the SiO2 nanofluid appears high values of the friction factor and heat transfer coefficient than TiO2 nanofluid. Also, the base fluid (20 %EG + 80 %W) gives high values of the heat transfer coefficient and proper values of friction factor than other base fluids. It seems that the SiO2 nanoparticles dispersed to (20 %EG + 80 %W) base fluid are a significant enhancement of the thermal properties than others. It is observed that the SiO2 nanoparticles dispersed to (20 %EG + 80 %W) base fluid are a significant augmentation of heat transfer in the automobile radiator. The regression equations among input (Reynolds number, Prandtl number, and nanofluid volume concentration) and response (friction factor and Nusselt number) are found. The results of the analysis indicated a significant input parameters to enhance heat transfer with the automotive cooling system. The comparison between experimental results and other researchers’ data is conducted, and there is a good agreement with a maximum deviation approximately 10 %.

Hot corrosion arises when metals are excited in the temperature range 700–900 °C in the existence of sulphate deposits, formed as a result of the reaction among sodium chloride and sulphur mixtures in the gas phase adjoining the metals. No alloy is resistant to hot corrosion occurrence indefinitely even though there are certain alloys that require a prolonged origination time at which the hot corrosion progression from the beginning stage to the circulation stage. Superalloys have been established for high-temperature applications. However, these alloys are not constantly able to meet both the high-temperature strength and high-temperature corrosion resistance simultaneously, so the need is to protect from hot corrosion. The high-temperature guarding system must meet numerous benchmarks, provide satisfactory environment resistance, be chemically and mechanically compatible with the substrate, be practically applicable, reliable and economically viable. This chapter briefly reviews the hot corrosion of some Ni- and Fe-base superalloys to recognise the occurrence. Extensive reviews on the hot corrosion of coatings have looked regularly since early 1970; the purpose of this chapter is not to repeat the published resources but relatively to emphasis on research developments and to point out some research forecasts.

Nanostructured ceramic materials have recently attracted attention as promising heat transfer fluid additives owing to their outstanding heat storage capacities. In this paper, experimental measurements of the specific heats of SiO2–Glycerol, SiO2–Ethylene Glycol, and SiO2–Glycerol/Ethylene Glycol mixture 60:40 ratio (by mass) nanofluids with different volume concentrations of 1.0–4.0% have been carried out using differential scanning calorimeter at temperatures of 25 °C and 50 °C. Experimental results indicate lower specific heat capacities are found with SiO2 nanofluids compared to their respective base fluids. The specific heat was decreasing with the increase of concentration, and this decrement depends on upon the type of the base fluid. It is observed that temperature has a positive impact on the specific heat capacity. Furthermore, the experimental values were compared with the theoretical model predictions, and a satisfactory agreement was established.

Over the recent years, addressing solar energy utilization for different applications has grabbed attention of many research groups around the world. From the past few decades, scientists had made progress in innovating new devices and methods for harnessing solar energy. In this respect, they developed new materials to improve energy efficiency as one of the major focal domain. During twentieth century, scientists engineered the application of nanotechnology in various domains including solar thermal conversion devices. Nanofluids, a homogeneous dispersion and stable suspension of nanoparticles in the base fluids, have made possible progress to achieve higher thermal properties at the smallest possible concentrations. This chapter intends to summarize the research done on the nanofluid applications in different solar thermal conversion systems. This chapter includes comprehensive information about thermophysical properties of nanofluids, the design of solar thermal system at optimum conditions, and the applications of solar collector with nanofluid. Also, challenges and opportunities for future research are identified and reported as well.

The response and energy absorption capacity of cellular sandwich panels that comprises of silk-cotton wood skins and aluminum honeycomb core are studied under quasi-static and low velocity impact loading. Two types of sandwich panels were constructed. The Type-I sandwich panel contains the silk-cotton wood plates (face plates) with their grains oriented to the direction of loading axis and in the case of Type-II sandwich panel, the wood grains were oriented transverse to the loading axis. In both of the above cases, aluminum honeycomb core had its cell axis parallel to the loading direction. The macro-deformation behavior of these panels is studied under quasi-static loading and their energy absorption capacity quantified. A series of low velocity impact tests were conducted and the dynamic data are discussed. The results are then compared with those of quasi-static experiments. It is observed that the energy absorption capacity of cellular sandwich panels increases under dynamic loading when compared with the quasi-static loading conditions. The Type-I sandwich panels tested in this study are found to be the better impact energy absorbers for low velocity impact applications.

Nanofluids have gained extensive attention due to their role in improving the efficiency of thermal systems. The present study reports a further enhancement in heat transfer coefficients in combination with structural modifications of flow systems namely, the addition of tape inserts. Experiments are undertaken to determine heat transfer coefficients and friction factor of TiO2/water nanofluid up to 3.0% volume concentration at an average temperature of 30 °C. The investigations are undertaken in the Reynolds number range of 8000–30,000 for flow in tubes and with tapes of different twist ratios. A significant enhancement of 23.2% in the heat transfer coefficients is observed at 1.0% concentration for flow in a tube. With the use of twisted tapes, the heat transfer coefficient increased with decrease in twist ratio for water and nanofluid. The heat transfer coefficient and friction factor are respectively 81.1% and 1.5 times greater at Re = 23,558 with 1.0% concentration and twist ratio of 5, compared to values with flow of water in a tube. An increase in the nanofluid concentration to 3.0% decreased heat transfer coefficients to values lower than water for flow in a tube and with tape inserts. A thermal system with tape insert of twist ratio 15 and 1.0% TiO2 concentration gives maximum advantage ratio, if pressure drop is considered along with enhancement in heat transfer coefficient.

The car radiator heat transfer enhancement by using TiO2 and SiO2 nanoparticles dispersed in water as a base fluid was studied experimentally. The test rig is setup as a car radiator with tubes and container. The range of Reynolds number and volume fraction are (250–1,750) and (1.0–2.5 %) respectively. Results showed that the heat transfer increases with increasing of nanofluid volume fraction. The experimental data is agreed with other investigator.

article i nfo Available online 5 February 2014 The increasing demand of nanofluids in industrial applications has led to increased attention from many researchers. In this paper, heat transfer enhancement using TiO2 and SiO2 nanopowders suspended in pure water is presented. The test setup includes a car radiator, and the effects on heat transfer enhancement under the operating conditions are analyzed under laminar flow conditions. The volume flow rate, inlet temperature and nanofluid volume concentration are in the range of 2- 8L PM, 60-80 °C and 1-2% respec- tively. The results showed that the Nusselt number increased with volume flow rate and slightly increased with inlet temperature and nanofluid volume concentration. The regression equation for input (volume flow rate, inlet temperature and nanofluid volume concentration) and response (Nusselt number) was found. The results of the analysis indicated that significant input parameters to enhance heat transfer with car radiator. These experimental results were found to be in good agreement with other researchers' data, with a deviation of only approximately 4%.

Experimental determination of heat transfer coefficients of SiO2/water and TiO2/water nanofluid up to 3% volume concentration flowing in a circular tube is undertaken. The investigations are conducted in the Reynolds number range of 5000 to 25000 at a bulk temperature of 30oC. The experiments are undertaken for flow in a circular tube with twisted tapes of different twist ratios in the range of 5 ≤ H/D ≤ 93. The heat transfer enhancement is inversely increased with twist ratio. The heat transfer coefficient of SiO2/water nanofluid at 3.0% volume concentration is 27.9% higher than water flow for the same twist ratio of five. However, the value of heat transfer coefficient of TiO2/water nanofluid evaluated at the same concentration is 11.4% greater than water for twist ratio five. Regression equations for Nusselt number estimation are developed valid for water and nanofluid flow with twisted tape inserts under turbulent flow conditions.

The low thermal properties of liquids have led to investigations into additives of small size (less than 100 nm solid particles) to enhance their heat transfer properties and hydrodynamic flow. To summarise the experimental and numerical studies, this paper reviews these computational simulations and finds that most of them are in agreement with the results of experimental work. Many of the studies report enhancements in the heat transfer coefficient with an increase in the concentration of solid particles. Certain studies with a smaller particle size indicated an increase in the heat transfer enhancement when compared to values obtained with a larger size. Additionally, the effect of the shape of the flow area on the heat transfer enhancement has been explored by a number of studies. All of the studies showed a nominal increase in pressure drop. The significant applications in the engineering field explain why so many investigators have studied heat transfer with augmentation by a nanofluid in the heat exchanger. This article presents a review of the heat transfer applications of nanofluids to develop directions for future work. The high volume fraction of various nanofluids will be useful in car radiators to enhance the heat transfer numerically and experimentally. Correlation equations can expose relationships between the Nusselt number, the Reynolds number, the concentration and the diameter of the nanoparticles. On the other hand, more work is needed to compare the shapes (e.g., circular, elliptical and flat tube) that might enhance the heat transfer with a minimal pressure drop.

The solar radiation study have been undertaken at Pekan campus (3.5oN, 103.4oE), Faculty of Mechanical Engineering, University Malaysia Pahang to utilize solar energy in east coast of Malaysia. The knowledge of the daily variation of global solar radiation is a necessity at the particular locality to consider the feasibility of solar energy utilisation. Hence, the diurnal patterns of global solar radiation were obtained using measured data from weather station which was installed at the site for three years (2011 – 2013). The patterns have been divided into five conditions such as clear sky, partially cloudy, fully cloudy, afternoon rain, and northeast monsoon season day. It was observed that on a clear sky day in Pekan, the maximum solar insolation was 939 W/m 2 and total solar energy received was 6.51 kWhr/m 2 . In contrast, on a fully cloudy day the maximum solar insolation was only 30 W/m 2 and total solar energy received was 0.35 kWhr/m 2 . Besides that, the empirical models were developed to estimate the monthly average daily global solar radiation on a horizontal surface with Pekan meteorological station data. Subsequently, the models were evaluated using statistical analysis. Based on analysis results, Eq. (13) and Eq. (15) models are proposed to estimate monthly average daily global solar radiation for Pekan. The present paper describes on advance understanding of daily variation global solar radiation in east coast Malaysia whereby it has significance for designing a solar system. Lastly, the developed Angstrom’s modified linear models are highly recommended to be used to estimate the monthly average daily global solar radiation in Pekan, Pahang and location with similar solar radiation patterns in east coast Malaysia.

This study deals with the estimation of monthly average daily global solar radiation incident on a horizontal surface at a location using meteorological data for different cities of Andhra Pradesh state. The regression equations of two types of models are developed for various locations of the state having varied climatic regions using measured meteorological parameters obtained from different measuring stations. Parameters such as the latitude and height of the location, maximum and minimum temperature and relative humidity are considered to develop linear and quadratic regression equations to estimate the monthly average daily global radiation. The estimated values are compared with measured data and with other theoretical models in terms of mean percent errors calculated using recognised statistical criteria of MBE, MABE, MPE and RMSE. The proposed quadratic model performs better than the proposed linear models and shows good agreement with the long-term pyranometer data of various locations with a dev...

The heat transfer coefficients and friction factor with SiO2/water nanofluid up to 4% particle volume concentration are determined for flow in a circular tube under constant heat flux boundary condition. Experiments are undertaken in the Reynolds number range of 5000–27,000 at a bulk temperature of 30 °C. The Nusselt number and friction factor at 3.0% nanofluid particle concentration is respectively greater than the values of water by 32.7% and 17.1%. The pressure drop increases with particle concentration up to 3.0% and decreases thereafter. The nanofluid friction factor decreases with increase in Reynolds number at any concentration. The particle concentration at which SiO2 nanofluid gives maximum heat transfer has been experimentally determined.

The effects of the tube specifications on the heat transfer in car radiator are significant to improve cooling system performance. Friction factor and heat transfer enhancement of three types of nanofluids flow through horizontal three shapes of tubes has been evaluated numerically. CFD model by using FLUENT software depending on finite volume method was conducted. TiO 2 nanoparticles with volume fractions (1%, 1.5%, 2% and 2.5%) are suspended in water as a base fluid to be nanofluids is used in this study. On the other hand, three types of tubes (circular, elliptical and flat tube) are chosen with 3 mm hydraulic diameter and 500 mm length. Numerical results show that the increase in volume fraction of nanofluid due to increase in fluid flow characteristics and heat transfer enhancement as compared with base fluid. The results of CFD model are compared with experimental data available in literature, and there is a good agreement with deviation 2%.