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Somchai Wongwises - One of the best experts on this subject based on the ideXlab platform.
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performance analysis of a minichannel based solar collector using different Nanofluids
Energy Conversion and Management, 2014Co-Authors: Omid Mahian, Ali Kianifar, Ahmet Z Sahin, Somchai WongwisesAbstract:Abstract In this paper, an analytical analysis has been performed to evaluate the performance of a minichannel-based solar collector using four different Nanofluids including Cu/water, Al2O3/water, TiO2/water, and SiO2/water. The analysis of first and second laws is conducted for turbulent flow by considering the constant mass flow rate of nanofluid. The results are presented for volume fractions up to 4% and nanoparticle size of 25 nm where the inner diameter of the risers of flat plate collector is assumed to be 2 mm. Analysis of the first law of thermodynamics reveals that Al2O3/water Nanofluids show the highest heat transfer coefficient in the tubes while the lowest value belongs to SiO2/water Nanofluids. The highest outlet temperature is provided by Cu/water Nanofluids, and after that TiO2/water, Al2O3/water, and SiO2/water Nanofluids are in ranks of second to fourth. The results of second law analysis elucidate that Cu/water nanofluid produces the lowest entropy generation among the Nanofluids. It is found that although the effective thermal conductivity of TiO2/water Nanofluids is less than Al2O3/water Nanofluids, but the entropy generation of TiO2/water is lower than Al2O3/water. Finally, some recommendations are given for future studies on the applications of Nanofluids in solar collectors.
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measurement of temperature dependent thermal conductivity and viscosity of tio2 water Nanofluids
Experimental Thermal and Fluid Science, 2009Co-Authors: Weerapun Duangthongsuk, Somchai WongwisesAbstract:Nanofluid is an innovative heat transfer fluid with superior potential for enhancing the heat transfer performance of conventional fluids. Many attempts have been made to investigate its thermal conductivity and viscosity, which are important thermophysical properties. No definitive agreements have emerged, however, about these properties. This article reports the thermal conductivity and dynamic viscosity of Nanofluids experimentally. TiO{sub 2} nanoparticles dispersed in water with volume concentration of 0.2-2 vol.% are used in the present study. A transient hot-wire apparatus is used for measuring the thermal conductivity of Nanofluids whereas the Bohlin rotational rheometer (Malvern Instrument) is used to measure the viscosity of Nanofluids. The data are collected for temperatures ranging from 15 C to 35 C. The results show that the measured viscosity and thermal conductivity of Nanofluids increased as the particle concentrations increased and are higher than the values of the base liquids. Furthermore, thermal conductivity of Nanofluids increased with increasing nanofluid temperatures and, conversely, the viscosity of Nanofluids decreased with increasing temperature of Nanofluids. Moreover, the measured thermal conductivity and viscosity of Nanofluids are quite different from the predicted values from the existing correlations and the data reported by other researchers. Finally, new thermophysical correlations are proposed formore » predicting the thermal conductivity and viscosity of Nanofluids. (author)« less
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effect of thermophysical properties models on the predicting of the convective heat transfer coefficient for low concentration nanofluid
International Communications in Heat and Mass Transfer, 2008Co-Authors: Weerapun Duangthongsuk, Somchai WongwisesAbstract:Abstract The term of nanofluid refers to a solid–liquid mixture with a continuous phase which is a nanometer sized nanoparticle dispersed in conventional base fluids. In order to study the heat transfer behavior of the Nanofluids, precise values of thermal and physical properties such as specific heat, viscosity and thermal conductivity of the Nanofluids are required. There are a few well-known correlations for predicting the thermal and physical properties of Nanofluids which are often cited by researchers to calculate the convective heat transfer behaviors of the Nanofluids. Each researcher has used different models of the thermophysical properties in their works. This article aims to summarize the various models for predicting the thermophysical properties of Nanofluids which have been commonly cited by a number of researchers and use them to calculate the experimental convective heat transfer coefficient of the nanofluid flowing in a double-tube counter flow heat exchanger. The effects of these models on the predicted value of the convective heat transfer of nanofluid with low nanoparticle concentration are discussed in detail.
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effect of thermophysical properties models on the predicting of the convective heat transfer coefficient for low concentration nanofluid
International Communications in Heat and Mass Transfer, 2008Co-Authors: Weerapun Duangthongsuk, Somchai WongwisesAbstract:Abstract The term of nanofluid refers to a solid–liquid mixture with a continuous phase which is a nanometer sized nanoparticle dispersed in conventional base fluids. In order to study the heat transfer behavior of the Nanofluids, precise values of thermal and physical properties such as specific heat, viscosity and thermal conductivity of the Nanofluids are required. There are a few well-known correlations for predicting the thermal and physical properties of Nanofluids which are often cited by researchers to calculate the convective heat transfer behaviors of the Nanofluids. Each researcher has used different models of the thermophysical properties in their works. This article aims to summarize the various models for predicting the thermophysical properties of Nanofluids which have been commonly cited by a number of researchers and use them to calculate the experimental convective heat transfer coefficient of the nanofluid flowing in a double-tube counter flow heat exchanger. The effects of these models on the predicted value of the convective heat transfer of nanofluid with low nanoparticle concentration are discussed in detail.
Omid Mahian - One of the best experts on this subject based on the ideXlab platform.
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recent advances in modeling and simulation of nanofluid flows part i fundamentals and theory
Physics Reports, 2019Co-Authors: Patrice Estellé, Js Marshall, Omid Mahian, Lioua Kolsi, Mohammad Amani, Goodarz Ahmadi, Clement Kleinstreuer, Majid SiavashiAbstract:Abstract It has been more than two decades since the discovery of Nanofluids-mixtures of common liquids and solid nanoparticles less than 100 nm in size. As a type of colloidal suspension, Nanofluids are typically employed as heat transfer fluids due to their favorable thermal and fluid properties. There have been numerous numerical studies of Nanofluids in recent years (more than 1000 in both 2016 and 2017, based on Scopus statistics). Due to the small size and large numbers of nanoparticles that interact with the surrounding fluid in nanofluid flows, it has been a major challenge to capture both the macro-scale and the nano-scale effects of these systems without incurring extraordinarily high computational costs. To help understand the state of the art in modeling Nanofluids and to discuss the challenges that remain in this field, the present article reviews the latest developments in modeling of nanofluid flows and heat transfer with an emphasis on 3D simulations. In part I, a brief overview of Nanofluids (fabrication, applications, and their achievable thermo-physical properties) will be presented first. Next, various forces that exist in particulate flows such as drag, lift (Magnus and Saffman), Brownian, thermophoretic, van der Waals, and electrostatic double layer forces and their significance in nanofluid flows are discussed. Afterwards, the main models used to calculate the thermophysical properties of Nanofluids are reviewed. This will be followed with the description of the main physical models presented for nanofluid flows and heat transfer, from single-phase to Eulerian and Lagrangian two-phase models. In part II, various computational fluid dynamics (CFD) techniques will be presented. Next, the latest studies on 3D simulation of nanofluid flow in various regimes and configurations are reviewed. The present review is expected to be helpful for researchers working on numerical simulation of Nanofluids and also for scholars who work on experimental aspects of Nanofluids to understand the underlying physical phenomena occurring during their experiments.
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performance analysis of a minichannel based solar collector using different Nanofluids
Energy Conversion and Management, 2014Co-Authors: Omid Mahian, Ali Kianifar, Ahmet Z Sahin, Somchai WongwisesAbstract:Abstract In this paper, an analytical analysis has been performed to evaluate the performance of a minichannel-based solar collector using four different Nanofluids including Cu/water, Al2O3/water, TiO2/water, and SiO2/water. The analysis of first and second laws is conducted for turbulent flow by considering the constant mass flow rate of nanofluid. The results are presented for volume fractions up to 4% and nanoparticle size of 25 nm where the inner diameter of the risers of flat plate collector is assumed to be 2 mm. Analysis of the first law of thermodynamics reveals that Al2O3/water Nanofluids show the highest heat transfer coefficient in the tubes while the lowest value belongs to SiO2/water Nanofluids. The highest outlet temperature is provided by Cu/water Nanofluids, and after that TiO2/water, Al2O3/water, and SiO2/water Nanofluids are in ranks of second to fourth. The results of second law analysis elucidate that Cu/water nanofluid produces the lowest entropy generation among the Nanofluids. It is found that although the effective thermal conductivity of TiO2/water Nanofluids is less than Al2O3/water Nanofluids, but the entropy generation of TiO2/water is lower than Al2O3/water. Finally, some recommendations are given for future studies on the applications of Nanofluids in solar collectors.
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analysis of entropy generation between co rotating cylinders using Nanofluids
Energy, 2012Co-Authors: Omid Mahian, Shohel Mahmud, Saeed Zeinali HerisAbstract:In this paper, the entropy generation due to flow and heat transfer of Nanofluids between Co-rotating cylinders with constant heat flux on the walls is studied, analytically. The governing equations in cylindrical coordinates are simplified and solved to find the effect of using Nanofluids with different volume fractions on the entropy generation rate in the annulus. The results are presented at various values of Brinkman number (Br), velocity ratio (λ), radius ratio (Π), heat flux on the inner cylinder (Q0), and a parameter (Ψ) which determines the contribution of the fluid friction in the overall entropy generation. The analysis has been done mainly using Al2O3–EG nanofluid, though some comparisons with TiO2–Water nanofluid are made. The thermophysical properties of Nanofluids are calculated using the available relations based on experimental data. From the average entropy generation viewpoint, at different conditions, an optimum volume fraction of nanoparticles is obtained in which the average entropy generation is minimized. Finally, some comparisons between the effects of using Al2O3–EG, and TiO2–Water Nanofluids are made. The results show that TiO2–Water nanofluid is more suitable than Al2O3–EG nanofluid to use as the working fluid at low Brinkman numbers.
Weerapun Duangthongsuk - One of the best experts on this subject based on the ideXlab platform.
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measurement of temperature dependent thermal conductivity and viscosity of tio2 water Nanofluids
Experimental Thermal and Fluid Science, 2009Co-Authors: Weerapun Duangthongsuk, Somchai WongwisesAbstract:Nanofluid is an innovative heat transfer fluid with superior potential for enhancing the heat transfer performance of conventional fluids. Many attempts have been made to investigate its thermal conductivity and viscosity, which are important thermophysical properties. No definitive agreements have emerged, however, about these properties. This article reports the thermal conductivity and dynamic viscosity of Nanofluids experimentally. TiO{sub 2} nanoparticles dispersed in water with volume concentration of 0.2-2 vol.% are used in the present study. A transient hot-wire apparatus is used for measuring the thermal conductivity of Nanofluids whereas the Bohlin rotational rheometer (Malvern Instrument) is used to measure the viscosity of Nanofluids. The data are collected for temperatures ranging from 15 C to 35 C. The results show that the measured viscosity and thermal conductivity of Nanofluids increased as the particle concentrations increased and are higher than the values of the base liquids. Furthermore, thermal conductivity of Nanofluids increased with increasing nanofluid temperatures and, conversely, the viscosity of Nanofluids decreased with increasing temperature of Nanofluids. Moreover, the measured thermal conductivity and viscosity of Nanofluids are quite different from the predicted values from the existing correlations and the data reported by other researchers. Finally, new thermophysical correlations are proposed formore » predicting the thermal conductivity and viscosity of Nanofluids. (author)« less
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effect of thermophysical properties models on the predicting of the convective heat transfer coefficient for low concentration nanofluid
International Communications in Heat and Mass Transfer, 2008Co-Authors: Weerapun Duangthongsuk, Somchai WongwisesAbstract:Abstract The term of nanofluid refers to a solid–liquid mixture with a continuous phase which is a nanometer sized nanoparticle dispersed in conventional base fluids. In order to study the heat transfer behavior of the Nanofluids, precise values of thermal and physical properties such as specific heat, viscosity and thermal conductivity of the Nanofluids are required. There are a few well-known correlations for predicting the thermal and physical properties of Nanofluids which are often cited by researchers to calculate the convective heat transfer behaviors of the Nanofluids. Each researcher has used different models of the thermophysical properties in their works. This article aims to summarize the various models for predicting the thermophysical properties of Nanofluids which have been commonly cited by a number of researchers and use them to calculate the experimental convective heat transfer coefficient of the nanofluid flowing in a double-tube counter flow heat exchanger. The effects of these models on the predicted value of the convective heat transfer of nanofluid with low nanoparticle concentration are discussed in detail.
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effect of thermophysical properties models on the predicting of the convective heat transfer coefficient for low concentration nanofluid
International Communications in Heat and Mass Transfer, 2008Co-Authors: Weerapun Duangthongsuk, Somchai WongwisesAbstract:Abstract The term of nanofluid refers to a solid–liquid mixture with a continuous phase which is a nanometer sized nanoparticle dispersed in conventional base fluids. In order to study the heat transfer behavior of the Nanofluids, precise values of thermal and physical properties such as specific heat, viscosity and thermal conductivity of the Nanofluids are required. There are a few well-known correlations for predicting the thermal and physical properties of Nanofluids which are often cited by researchers to calculate the convective heat transfer behaviors of the Nanofluids. Each researcher has used different models of the thermophysical properties in their works. This article aims to summarize the various models for predicting the thermophysical properties of Nanofluids which have been commonly cited by a number of researchers and use them to calculate the experimental convective heat transfer coefficient of the nanofluid flowing in a double-tube counter flow heat exchanger. The effects of these models on the predicted value of the convective heat transfer of nanofluid with low nanoparticle concentration are discussed in detail.
Amir Menbari - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation of thermal performance for direct absorption solar parabolic trough collector dasptc based on binary Nanofluids
Experimental Thermal and Fluid Science, 2017Co-Authors: Amir Menbari, Ali Akbar Alemrajabi, Amin RezaeiAbstract:Abstract Nanofluids can be utilized to capture and distribute effectively solar radiation due to the capability of their nanoparticles in the liquid medium to scatter and absorb solar radiation. Hence, nanofluid-based solar collectors have the potential to harness solar radiant energy. Proper Nanofluids can be selected for solar applications based on their potential optical properties. Binary Nanofluids as a new class of Nanofluids comprising a base fluid and two different nanoparticles may exhibit a behavior different from any of their components. The behavior of such Nanofluids has not yet been extensively investigated. The present experimental study was, therefore, designed and implemented to investigate the absorption and thermal conductivity of binary Nanofluids and to evaluate the factors involved in their optimal stability. For this purpose, two dissimilar nanoparticles, i.e. CuO (with high absorption properties) and γ-Al2O3 (with high scattering properties) were chosen to prepare a binary nanofluid. Results showed that the thermal conductivity and aggregation of the prepared nanofluid were highest and lowest, respectively, under optimal stability conditions. As another main goal of this study, the effect of the binary nanofluid on the thermal efficiency of direct absorption solar parabolic trough collectors (DASPTCs) was evaluated. Results showed that solar irradiance is absorbed and converted into a significant amount of sensible heat along the length of the receiver pipe. Experiments with the DASTPC collector also revealed that the thermal efficiency of the system could be enhanced by increasing nanoparticle volume fraction and nanofluid flow rate.
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experimental investigation of stability and extinction coefficient of al2o3 cuo binary nanoparticles dispersed in ethylene glycol water mixture for low temperature direct absorption solar collectors
Energy Conversion and Management, 2016Co-Authors: Amir Menbari, Ali Akbar Alemrajabi, Yousef GhayebAbstract:Abstract Binary Nanofluids form a new class of Nanofluids made through the simultaneous dispersion of two dissimilar nanoparticles in a base fluid. Two different nanoparticles may behave differently from their constituent components. Given the wide applications of binary Nanofluids in a variety of fields, it is important to gain an understanding of the best stability conditions for binary Nanofluids. In this work, the effects of such nanofluid properties as pH, surfactant (SHMP) concentration, and ultrasonic time are experimentally investigated on the stability of binary Nanofluids. For this purpose, binary Nanofluids are prepared using the two-step method. Two dissimilar nanoparticles, i.e. CuO and γ-Al 2 O 3 nanoparticles are dispersed in ethylene glycol and in the ethylene glycol–water mixture to form the desired Nanofluids. Results show that at optimal stability conditions, viscosity and absorbency of the Nanofluids are minimum and maximum, respectively. Also, the stability optimal parameters of binary Nanofluids are found to be different from their corresponding values for each individual nanofluid. The extinction coefficient of the binary nanofluid is found to be approximately equal to the sum of those of the constituent components. Finally, the extinction coefficient of the nanoparticles dispersed in the mixture of ethylene glycol–water is determined to be greater than that of ethylene glycol.
W H Azmi - One of the best experts on this subject based on the ideXlab platform.
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an experimental study on the thermal conductivity and dynamic viscosity of tio2 sio2 Nanofluids in water ethylene glycol mixture
International Communications in Heat and Mass Transfer, 2017Co-Authors: M F Nabil, W H Azmi, Abdul K Hamid, Rizalman Mamat, F Y HagosAbstract:The hybrid nanofluid has been thriving among researchers due to its potential to improve heat transfer performance. Therefore, various studies on heat transfer properties need to be carried out to provide a better understanding on hybrid nanofluid performance. In this paper, the experimental work is focused on the thermal conductivity and dynamic viscosity of TiO2-SiO2 Nanofluids in a mixture of water and ethylene glycol (EG) with volume ratio of 60:40. The stable suspension of TiO2-SiO2 prepared at volume concentrations of 0.5 to 3.0%. The measurements of thermal conductivity and dynamic viscosity were performed at a temperature range of 30 to 80 °C by using KD2 Pro Thermal Properties Analyser and Brookfield LVDV III Ultra Rheometer, respectively. The thermal conductivity of TiO2-SiO2 Nanofluids was improved by increasing the volume concentration and temperature with 22.8% maximum enhancement. Besides, the viscosity of TiO2-SiO2 Nanofluids showed evidence of being influenced by nanofluid concentration and temperature. Additionally, the TiO2-SiO2 Nanofluids behaved as a Newtonian fluid for volume concentration up to 3.0%. The properties enhancement ratio suggested that TiO2-SiO2 Nanofluids will aid in heat transfer for concentrations of more than 1.5% and within the range of the temperature studied. A new correlation for thermal conductivity and dynamic viscosity of TiO2-SiO2 Nanofluids were developed and found to be precise.
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heat transfer and friction factor of water based tio2 and sio2 Nanofluids under turbulent flow in a tube
International Communications in Heat and Mass Transfer, 2014Co-Authors: W H Azmi, K V Sharma, P K Sarma, Rizalma Mama, G NajafiAbstract: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.
