Browsing by Author "Al-Gebory, Layth Wadhah Ismael"

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Effect of electrostatic stabilization on thermal radiation transfer in nanosuspensions: Photo-thermal energy conversion applications
(Elsevier, 2018-04) Al-Gebory, Layth Wadhah Ismael; Mengüç, Mustafa Pınar; Koşar, A.; Şendur, K.; Mechanical Engineering; MENGÜÇ, Mustafa Pınar; Al-Gebory, Layth Wadhah Ismael
Solar thermal collectors are among the most important photo-thermal energy conversion systems. Effectiveness of these systems is measured by the ability of working fluid to absorb incident radiative energy. Although nanosuspensions are considered very promising for this purpose, there is a concern about their stability and their long-term use. Electrostatic and steric stabilization methods are among the two approaches used for colloidal suspensions. In thermal applications, electrostatic stabilization is usually preferred; especially in high temperature applications. The aim of this study is to investigate, both experimentally and numerically, the effect of electrostatic stabilization on the thermal radiation transfer mechanisms in TiO2 and Al2O3 nanosuspensions. The experimental section covers nano suspensions preparation and characterization, where the effects of electrostatic stabilization (pH and zeta potential values) on the increasing effective particle size due to agglomeration behaviour are explored. The numerical part covers the estimation of radiative properties and thermal radiation transfer based on the average particle agglomerate size obtained from the particle size distributions in the experimental part. The radiative properties are assessed using the single scattering approximation technique based on the Lorenz-Mie theory. The thermal radiation transfer is obtained by solving the radiative transfer equation by the discrete ordinate method. The results show remarkable stability behaviour under the effect of the pH value for the two nanosuspensions types. The effect of the different particle agglomerate size shows a considerable enhancement in the radiative properties specifically in the UV/Vis spectrum, which has a significant impact on the thermal radiative transfer phenomena, due to the solar spectrum. It is also shown that nanosuspensions with different particle agglomerate sizes have a significant effect on the volumetric radiative heat flux, where the radiative energy losses decrease in comparison to those of pure water. (C) 2017 Elsevier Ltd. All rights reserved.
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The effect of pH on particle agglomeration and optical properties of nanoparticle suspensions
(Elsevier, 2018-11) Al-Gebory, Layth Wadhah Ismael; Mengüç, Mustafa Pınar; Mechanical Engineering; MENGÜÇ, Mustafa Pınar; Al-Gebory, Layth Wadhah Ismael
Nanoparticle suspensions (NPSs) are used extensively to improve the thermal efficiency of different engineering systems because of their unique thermo-optical properties. NPSs have also been uses in coatings as they improve or alter the appearance of objects, where radiative and optical properties play a significant role. In all these applications, pH of a suspension has a significant impact on the particle agglomeration behaviour, and consequently on optical properties and then on radiative heat transfer. In the present study, the effect of pH on the agglomeration of TiO2 NPSs is investigated. For this purpose, both the experimental and theoretical studies were carried out. In the experiments, the particle size distribution and the average (effective) particle size for the NPSs in different conditions (the pH and particle volume fraction) were measured using the dynamic light scattering (DLS) technique. The effects of different particle agglomerates under different pH values on the dependent/independent scattering are explored and the corresponding regimes are demarked for different conditions. The effects of particle agglomeration, particle size distribution and their contributions to the scattering coefficients are obtained using the UV–Vis-NIR spectroscopy technique. The results show that pH may have significant effect on the optical properties involving NPSs. Adjusting the pH value based on the isoelectric point of the nanoparticle is an efficient method when specific radiative properties are required for specific applications. Different regimes of the dependent/independent scattering can be obtained by changing the pH of a particular nanoparticle suspension.
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Effect of pH on particle agglomeration and radiative transfer in nanoparticle suspensions
(2018-08) Al-Gebory, Layth Wadhah Ismael; Mengüç, Mustafa Pınar; Mengüç, Mustafa Pınar; Başol, Altuğ; Ertunç, Özgür; Koşar, A.; Şendur, K.; Department of Mechanical Engineering; Al-Gebory, Layth Wadhah Ismael
Nanoparticle suspensions (NPSs) are solid-fluid mixtures where small dielectric or metallic particles (with sizes <100 nm) used in a base fluid. NPSs have unique and tunable thermo-optical properties, and for that reason they can be used extensively to improve the thermal efficiency of different systems where they show remarkable enhancement in heat transfer compared with those of a base fluid. The effectiveness of solar thermal systems used for photo-thermal energy conversion is measured by their ability of absorb radiative energy by the working medium; for such applications NPSs are much better choice than traditional fluids. NPSs have also been used in coatings as they can be tuned to improve or alter the appearance of an object, as radiative and optical properties play significant roles. Although NPSs are considered very promising for these applications, there is some concern about their stability and their long-term use. Particle agglomeration in NPSs remains one of the most important challenges faced in terms of their usage. In all of these applications, the pH value and its effects on the particle agglomeration may have significant impact on the nanoparticles stability behavior, and consequently on the radiative transfer of energy. Steric and electrostatic stabilization methods are among the two approaches used for particulate suspensions to avoid such problems. In thermal applications, especially in high temperature ones, electrostatic stabilization method is usually preferred. In this dissertation, both experimental and theoretical investigations were carried out to determine the stability and optical properties of individual (water/TiO2 and water/Al2O3) and hybrid (water/TiO2+Al2O3) nanoparticle suspensions. The experimental studies include the preparation, characterization, and optical property measurements of the nanoparticle suspensions. The impact of the electrostatic stabilization (zeta potential and pH values) on the size and structure of particles due to agglomeration behavior are explored. The particle size distribution and the average (effective) particle agglomerate size for the nanoparticle suspensions in different conditions (the pH and particle volume fraction) were measured by using the dynamic light scattering (DLS) technique. The effects of the different particle agglomerates under different pH values on the dependent and independent scattering and their boundaries are investigated and demarcated for different conditions, where the relationship between the distance between particle to particle surface and the incident wavelength for different particle types are explored. The effects of particle agglomeration (similar and dissimilar particle agglomerations), particle size distribution and their contributions to the radiative properties of the nanoparticle suspensions are determined using the UV-Vis spectroscopy technique. The numerical part included the study of the optical and radiative properties and thermal radiation transfer based on the average (effective) particle agglomerate size obtained from the experimental studies. The optical and radiative properties of nanoparticle suspensions are calculated based on the Lorenz-Mie theory applying the single-scattering approximation technique. The influence of the particle size distribution on the scattering coefficient of nanoparticle suspensions is studied theoretically to account for the effect of compact particle agglomerates. The thermal radiation transfer in the nanoparticle suspensions is assessed by solving the radiative transfer equation using the discrete ordinates method, where the volumetric radiative heat flux and the thermal flux efficiency are calculated. The results show the impact of pH value on the stability of individual and vi hybrid nanoparticle suspensions. The different particle agglomerate types, sizes, and shapes yield different behavior of suspensions, including their stability or sedimentation rates, which help formation of optically thicker media. Light scattering in such media is significantly different as a function of the proximity of particles to each other. If they are closer to each other roughly less than dominant wavelength of the radiation, then their behavior is defined as dependent scattering, which is explored in this study. It is shown that a significant enhancement in the radiative properties, specifically in the UV/Vis spectrum, can be observed , which has an important effect on the thermal radiation transfer of the incident solar radiation. The demarcation of dependent and independent scattering regimes is explained for the individual and hybrid nanoparticle suspensions based on their pH value. NPSs with different effective particle agglomerate sizes have a considerable effect on the volumetric radiative heat flux, where the losses in radiative energy were decrease in comparison to those of pure water. The results also show the effects of composite particle agglomerates in the hybrid nanoparticle suspensions on the radiative properties, which are produced from dissimilar suspended particles. The results of this dissertation show that the pH value has a dominant effect on the radiative transfer involving nanoparticle suspensions, compared to other parameters. Adjusting the pH value based on the isoelectric point of the nanoparticle is an efficient method when specific radiative properties are required for specific applications. Such impact of pH value on optical and radiative properties of NPSs is studied for the first time in the literature.
Open Access
Investigation of corrosion behavior of carbon steel for petroleum pipeline applications under turbulent flow conditions
(Institute of Information Science, 2020) Ahmed, Mohammed Salih; Talib, Nayyef Ahmed; Al-Gebory, Layth Wadhah Ismael; Ahmed, Mohammed Salih; Talib, Nayyef Ahmed; Al-Gebory, Layth Wadhah Ismael
This study investigates the corrosion of steel samples immersed in water with a dynamic corrosion setup at different pH values for three different velocities and three different exposure time. The characteristics of material surface were observed by utilizing Atomic Force Micrographs (AFM). Under the dynamic and static conditions, the rate of corrosion of the steel samples in deionized water (DIW) was calculated through the weight loss measurements. It has been found that the corrosion rate of steel samples under static conditions was higher with the lower pH values. It was observed that the corrosion rate was maximum at pH = 4 and the minimum at pH = 6. The static corrosion tests suggest that the corrosion rate was high in the first two days then decreased with the increasing of time of tests. The effect of wall shear stress and time of immersion was evaluated under the dynamic corrosion tests. The results suggest that increased wall shear stress lead to an increase the corrosion rate specially at pH = 4.
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Investigation of the effect of particle stability on the transport properties and thermal behavior of ethylene glycol-water/SiO2 binary nanofluids
(IOP Publishing, 2020-04-09) Al-Gebory, Layth Wadhah Ismael; Al-Gebory, Layth Wadhah Ismael
Nanofluids (Nfs) are considered as an effective working media in different thermal processes. Over the years, much attention has been paid to the problem of nanoparticle stability in base fluids in an unconfined area of research, especially in the field of thermal applications. There is still concern about the stability of nanoparticles and their effects on the transport properties and thermal performance in thermal systems. In the present paper, the transport properties and thermal behavior of ethylene glycol-water/ SiO2
Open Access
Micro-hydrodynamic interaction mechanisms in tio2 nano-colloidal suspensions with different particle size distributions: the effects of electrostatic and steric stabilization
(Bangladesh University of Engineering and Technology, 2020) Al-Gebory, Layth Wadhah Ismael; Al-kaisy, H. A.; Mahdi, M.; Al-Gebory, Layth Wadhah Ismael
Micro-hydrodynamic interaction mechanisms of colloidal particles have important effects on the intrinsic properties and behavior of nano-colloidal suspensions, which in turn affect their different potential applications. Particle stability and size distribution are among the important parameters that influence the micro-hydrodynamic interaction mechanisms. The aim of this research is to investigate, both experimentally and theoretically, the effect of stabilization methods on the micro-hydrodynamic interaction mechanisms in TiO2 nano-colloidal suspensions considering the different particle size distributions. The effect of the two stability methods (electrostatic and steric) on the distribution of particle size are experimentally investigated. The effect of different particle size distributions on the motion and net forces (Brownian, gravitational, lift, and drag) acting on colloidal particles is theoretically estimated based on the correlation formula. The interactions between the particle-fluid molecules and colloidal particles themselves are considered in the calculations. The results show that the stability of colloidal particles has a significant effect on the micro-hydrodynamic interaction mechanisms in nano-colloidal suspensions, where different particle size and size distribution can be obtained. Low particle sedimentation is observed in the case of steric stabilization and with low particle concentration, which enhances the particle diffusion coefficient. The laminar motion of the TiO2 particles can be achieved in the case of high stability nano-colloidal suspension. In this case, the flow of particles occurs in the Stock’s regime. The investigation of the micro-hydrodynamic interaction mechanisms in nano-colloidal suspensions in different conditions gives clear information on the possibility of their usage in different applications.
Open Access
Optical and radiative properties of individual and hybrid nanosuspensions: The effects of similar and dissimilar particle agglomerates on thermal radiation
(Yildiz Technical University, 2021-02) Al-Gebory, Layth Wadhah Ismael; Al-Gebory, Layth Wadhah Ismael
Nanosuspensions are proposed for use in improving the thermal efficiency of different thermal systems; including solar thermal power plants. Because of their excellent and unique thermo-optical properties, which are the basis of thermal transfer phenomena, they are used as working fluids in solar thermal collectors for photothermal energy conversion. However, particle agglomeration in nanosuspensions remains one of the most important challenges faced in terms of their usage. The purpose of this study is to investigate the particle agglomeration behavior of water-based Al2O3 and TiO2 individual and hybrid nanosuspensions and observe their effects on spectral radiative properties. By carrying out number of experiments, the effects of similar and dissimilar particle agglomerations on radiative properties are clarified. The results show that pH have significant effect on the particle agglomeration which in turn affects the optical and radiative properties involving individual and hybrid nanosuspensions. Particle agglomerates (similar and dissimilar) plays an important role when specific radiative properties are required for specific applications. Different regimes of the dependent/independent scattering can be obtained from the effect of similar and dissimilar particle agglomerates of a particular nanosuspension.
Open Access
Participating media for volumetric heat generation
(Yıldız Teknik Üniversitesi, 2019-01) Al-Gebory, Layth Wadhah Ismael; Al-Gebory, Layth Wadhah Ismael
When an electromagnetic wave interacts with participating media (e.g. particulate media); the intensity of the radiation may be changed by the absorption, emission and scattering phenomena. Subsequently, the incident radiation will be attenuated and/or augmented under the effect of these phenomena. Light scattering and absorption by small particles are quite important in a wide range of applications such as meteorology, biomedicine, biophysics, astronomy, combustion, fire and flame, and solar thermal applications. Particulate media have been introduced as a working medium to improve the efficiency of thermal systems such as solar thermal power plants. The efficiency of the direct absorption solar thermal collectors (DASC) can be improved by using particulate media because of the unique thermo-optical properties, which in turn leads to enhance the thermal performance. The main objective of the present study is to investigate the effect of the participating media in the volumetric heat generation under the concept of photo-thermal energy conversion.
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A review of optical and radiative properties of nanoparticle suspensions: effects of particle stability, agglomeration, and sedimentation
(Begell House Inc., 2020) Al-Gebory, Layth Wadhah Ismael; Mengüç, Mustafa Pınar; Mechanical Engineering; MENGÜÇ, Mustafa Pınar; Al-Gebory, Layth Wadhah Ismael
Nanoparticle suspensions (NPSs) are suspensions of nanosize particles in base fluids in the form of a solid-liquid mixture. They are used extensively in a wide range of industrial and engineering applications, and show considerably different and tunable, physiochemical, thermal, and radiative properties compared to other solutions. It has been demonstrated that added nanoparticles can significantly alter and enhance the optical and radiative properties of the base fluids. There is still a concern about the particle agglomeration and sedimentation behaviors and the long-term stability of NPSs under different conditions, which may limit their potential reliable applications. There is a close relationship between the particle agglomeration and the optical and radiative properties of nanoparticle suspensions. In this review, the relationship between these fundamental properties with the emphasis on the procedural stability of nanoparticle suspensions is explored. Different issues related to the preparation and the characterization of NPSs, their sedimentation, the effects of particle types, sizes on individual, hybrid, and agglomerated nanoparticle suspensions, as well as the effect of pH values, are discussed. Their effects on the optical and spectral radiative properties are also discussed. Simplified analyses are outlined based on dependent-independent scattering demarcation and effective properties of NPSs.
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Temperature-dependent particle stability behavior and its effect on radiative transfer in water/SiO2 nanofluids
(Yildiz Technical University, 2021-09) Al-Gebory, Layth Wadhah Ismael; Al-Gebory, Layth Wadhah Ismael
Radiative transfer is one of the methods of energy transport that includes in a wide range of applications and we feel it in our daily lives. Thermal radiation transfer plays an effective role in the utilization of renewable energy. The radiative and optical properties, as well as the nature of the radiative scattering, are the basic principles of the thermal radiation transfer. The unique properties of nanofluids offer the unmatched potential for use in energy utilization, the working temperature has a dominant effect on the stability and radiative properties of such type of suspensions. In this research, the radiative transfer (optical properties, the independent and dependent scattering, and radiative properties) in water/SiO2 nanofluids are investigated; taking into consideration the effect of working temperature on the stability of the particles. The effect of the temperature on the stability ratio and particle agglomeration is determined by estimating the radius of gyration of particle agglomerates using the scaling law based on the stability (DLVO) method. The single-scattering approximation (SSA) is used to calculate the radiative properties in the case of independent scattering, while the quasi-crystalline approximation (QCA) is used for this purpose in the case of dependent scattering. The results show that the temperature has a significant effect on the stability of particles and radiative transfer in nanofluids. It was observed by comparing the results from the two approximation methods in the Rayleigh regime. Particle size affects the physical and scattering cross-sectional areas which give a general understanding of the scattering mechanism from small to large particles.