scholarly journals Determination and measurement of some thermophysical properties of nanofluids and comparison with literature studies

2020 ◽  
pp. 239-239
Author(s):  
Adnan Topuz ◽  
Beytullah Erdoğan ◽  
Osman Aycan
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermophysical Properties ◽  
Convection Heat Transfer ◽  
Conductivity Measurement ◽  
Pumping Power ◽  
Transfer Enhancement ◽  
Convection Heat Transfer Coefficient ◽  
Volumetric Concentration ◽  
Wire Method

The thermophysical properties of nanofluids must be determined to evaluate their thermal performances like heat transfer, convection heat transfer coefficient, Nusselt number. The purpose of this study is to obtain the thermophysical properties of nanofluids. Al2O3, TiO2, and ZnO are used as a nanoparticle, while deionized water is used as base fluid. The solutions included nanoparticles in a way to be each with 0.5%, 0.7%, and 1.0% volumetric concentration were prepared. SDS was added to the solutions as a surfactant to prevent instability that occurred due to agglomeration and sedimentation. For thermal conductivity measurement, the device that works by the transient hot-wire method was used between 30-60?C temperatures. Also, for viscosity measurement, the device that works as based on the vibrating plate method was used between 20-50?C temperatures. Density and specific heat values are obtained with the help of the well-known equations while thermal conductivity and viscosity are measured. Thanks to this study, it is emphasized how thermophysical properties of nanofluids change according to temperature and volumetric concentration. Moreover, their curve fitting equations are obtained. All of the thermophysical properties compared with the studies in the literature. It is established that the thermal conductivity of nanofluids is proportional to temperature, and viscosity of it is proportional to volumetric concentrations but inversely with temperature. Finally, the effects of the augmentation in dynamic viscosity on pumping power were considered as well as the increase in thermal conductivity; thus, no abnormal heat transfer enhancement was observed.

Lattice Boltzmann Simulation of Mixed Convection Heat Transfer in a Lid-Driven Square Cavity Filled With Nanofluid: A Revisit

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Özgür Ekici
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Mixed Convection ◽  
Thermophysical Properties ◽  
Lattice Boltzmann ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Transfer Enhancement ◽  
Square Cavity ◽  
Mixed Convection Heat Transfer

Mixed convection heat transfer of Al2O3 nanofluid in a lid-driven square cavity with differentially heated vertical walls is studied numerically with lattice Boltzmann method (LBM). In order to understand the reasons for the conflicting results on heat transfer enhancement in cavity problems, formulation of nondimensional properties and modeling thermophysical properties, in accordance with the relative effects of natural and forced convection flows, are examined. In addition to gain more insight into the physics, one of the goals of the study is to identify the reasons of existing contradictory findings; therefore, a single-phase formulation is adopted as has been the case in the majority of related literature to date. To isolate the effects of thermophysical properties on the results and to maintain the same natural and forced convection effects, all nondimensional parameters are defined using the corresponding thermophysical properties of the fluid under examination. Two different effective thermal conductivity and viscosity models are tested for a range of Reynolds and Rayleigh numbers to investigate their effects on the nanofluid behavior. Depending on the effective viscosity model, an increase or decrease is obtained in the average Nusselt number. It is also illustrated that the relative magnitudes of effective thermal conductivity values for different models do not translate into the heat transfer enhancement due to convective effects. Moreover, it is shown that thermal behavior of nanofluid approaches to the one of base fluid's as the buoyancy driven flow gets stronger, which is independent of the employed effective property models.

scholarly journals Improved Thermophysical Properties and Energy Efficiency of Aqueous Ionic Liquid/MXene Nanofluid in a Hybrid PV/T Solar System

Nanomaterials ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 1372 ◽  
Author(s):  
Likhan Das ◽  
Khairul Habib ◽  
R. Saidur ◽  
Navid Aslfattahi ◽  
Syed Mohd Yahya ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Ionic Liquid ◽  
Palm Oil ◽  
Thermophysical Properties ◽  
Conductivity Measurement ◽  
Optimum Concentration ◽  
Heat Transfer Fluid ◽  
Solar Pv ◽  
T System

In recent years, solar energy technologies have developed an emerging edge. The incessant research to develop a power source alternative to fossil fuel because of its scarcity and detrimental effects on the environment is the main driving force. In addition, nanofluids have gained immense interest as superior heat transfer fluid in solar technologies for the last decades. In this research, a binary solution of ionic liquid (IL) + water based ionanofluids is formulated successfully with two dimensional MXene (Ti3C2) nano additives at three distinct concentrations of 0.05, 0.10, and 0.20 wt % and the optimum concentration is used to check the performance of a hybrid solar PV/T system. The layered structure of MXene and high absorbance of prepared nanofluids have been perceived by SEM and UV–vis respectively. Rheometer and DSC are used to assess the viscosity and heat capacity respectively while transient hot wire technique is engaged for thermal conductivity measurement. A maximum improvement of 47% in thermal conductivity is observed for 0.20 wt % loading of MXene. Furthermore, the viscosity is found to rise insignificantly with addition of Ti3C2 by different concentrations. Conversely, viscosity decreases substantially as the temperature increases from 20 °C to 60 °C. However, based on their thermophysical properties, 0.20 wt % is found to be the optimum concentration. A comparative analysis in terms of heat transfer performance with three different nanofluids in PV/T system shows that, IL+ water/MXene ionanofluid exhibits highest thermal, electrical, and overall heat transfer efficiency compared to water/alumina, palm oil/MXene, and water alone. Maximum electrical efficiency and thermal efficiency are recorded as 13.95% and 81.15% respectively using IL + water/MXene, besides that, heat transfer coefficients are also noticed to increase by 12.6% and 2% when compared to water/alumina and palm oil/MXene respectively. In conclusion, it can be demonstrated that MXene dispersed ionanofluid might be great a prospect in the field of heat transfer applications since they can augment the heat transfer rate considerably which improves system efficiency.

Convective Heat Transfer Enhancement With Nanofluids: The Effect of Temperature-Variable Thermal Conductivity

2010 ◽  
Author(s):  
Sezer O¨zerinc¸ ◽  
Almıla G. Yazıcıog˘lu ◽  
Sadık Kakac¸
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermal Conductivity ◽  
Heat Transfer Enhancement ◽  
Forced Convection ◽  
Convection Heat Transfer ◽  
Thermal Dispersion ◽  
Convection Heat ◽  
Transfer Enhancement ◽  
Experimental Values

A nanofluid is defined as the suspension of nanoparticles in a base liquid. Studies in the last decade have shown that significant amount of thermal conductivity and heat transfer enhancement can be obtained by using nanofluids. In the first part of this study, classical forced convection heat transfer correlations developed for pure fluids are used to predict the experimental values of heat transfer enhancement of nanofluids. It is seen that the experimental values of heat transfer enhancement exceed the enhancement predictions of the classical correlations. On the other hand, a recent correlation based on the thermal dispersion phenomenon created by the random motion of nanoparticles predicts the experimental data well. In the second part of the study, in order to further examine the validity of the thermal dispersion approach, a numerical analysis of forced convection heat transfer of Al2O3/water nanofluid inside a circular tube in the laminar flow regime is performed by utilizing single phase assumption. A thermal dispersion model is applied to the problem and variation of thermal conductivity with temperature and variation of thermal dispersion with local axial velocity are taken into account. The agreement of the numerical results with experimental data might be considered as an indication of the validity of the approach.

Natural Convection in Rectangular Cavity With Nanoparticle Enhanced Ionic Liquids (NEILs)

2012 ◽  
Author(s):  
Titan C. Paul ◽  
A. K. M. M. Morshed ◽  
Elise B. Fox ◽  
Ann E. Visser ◽  
Nicholas J. Bridges ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Capacity ◽  
Ionic Liquid ◽  
Ionic Liquids ◽  
Natural Convection ◽  
Thermophysical Properties ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat

A systematic natural convection heat transfer experiment has been carried out of nanoparticle enhanced ionic liquids (NEILs) in rectangular enclosures (lengthxwidthxheight, 50×50×50mm and 50×50×75mm) heated from below condition. In the present experiment NEIL was made of N-butyl-N-methylpyrrolidinium bis{(trifluoromethyl)sulfonyl} imide, ([C4mpyrr][NTf2]) ionic liquid with 0.5% (weight%) Al2O3 nanoparticles. In addition to characterize the natural convection behavior of NEIL, thermophysical properties such as thermal conductivity, heat capacity, and viscosity were also measured. The result shows that the thermal conductivity of NEIL enhanced ∼3% from the base ionic liquid (IL), heat capacity enhanced ∼12% over the measured temperature range. The natural convection experimental result shows consistent for two different enclosures based on the degrading natural convection heat transfer rate over the measured Rayleigh number range. Possible reasons of the degradation of natural convection heat transfer may be the relative change of the thermophysical properties of NEIL compare to the base ionic liquid.

One-Dimensional Numerical Investigation of a Cylindrical Micro Combustor

2009 ◽  
Author(s):  
A. Irani R. ◽  
M. Saediamiri ◽  
M. S. Saidi ◽  
M. H. Saidi ◽  
M. B. Shafii
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convection Heat Transfer ◽  
Diffusion Reaction ◽  
Convection Heat ◽  
Convection Heat Transfer Coefficient ◽  
One Dimensional ◽  
Micro Combustor

In this paper, a one-dimensional numerical approach is used to study the effect of various parameters such as micro combustor diameter, mass flow rate and external convection heat transfer coefficient on the temperature and species mass fraction profiles. A premixed mixture of H2-Air with a multi-step chemistry (9 species and 19 reactions) is used and thermal conductivity of the mixture is considered as a function of species thermal conductivity and temperature by using a set of new relations. The transient gas phase energy and species conservation equations result in an Advection-Diffusion-Reaction system (A-D-R) that leads to two stiff systems of PDEs, which can not be solved by conventional Computational Fluid Dynamics (CFD) methods. In the present work, Strang splitting method, which is suitable for nonlinear stiff system of PDEs, is used. The results show that both convection heat transfer coefficient and micro combustor diameter have a significant effect on the combustion and heat transfer rates in the micro scales. Also, increasing the convective heat transfer coefficient and decreasing the diameter and inlet mixture velocity, decreases the temperature and active radicals along the micro combustor.

Characterization and Convective Heat Transfer With Nanofluids

2011 ◽  
Author(s):  
Yijun Yang ◽  
Alparslan Oztekin ◽  
Sudhakar Neti ◽  
Satish Mohapatra
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Particle Size ◽  
Convective Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Convective Heat ◽  
Al2o3 Nanoparticles ◽  
Pumping Power ◽  
Transfer Enhancement ◽  
Low Concentrations

Heat transfer and flow dynamics of nanofluids are investigated in developing laminar pipe flows. Characterization of nanofluids is examined by measuring resultant effective particle size, thermal conductivity and viscosity for various values of particle concentrations and temperatures. Nanofluids considered in this study are diamond-graphene (ND-50) nanoparticle in silicone oil (Syltherm 800), and Al2O3 nanoparticles in DI water with and without dispersers/stabilizers. The particle size of various nanofluids is determined quantitatively from measurements using Dynamic Light Scattering device (DLS) and also determined qualitatively from SEM images. Thermal conductivity measurements are conducted by using nano-flash LFA447 device for particle volume fractions ranging from 0.8% to 5.1%. Measured values of thermal conductivity of all fluids at low concentrations agree well with the results predicted by Maxwell model. Viscosity measurements are conducted using parallel plate geometry Rheometrics viscometer at different concentration and temperature as a function of shear rate. At low shear rates the fluid behaves as a Newtonian fluid while it becomes a shear thinning fluid at higher particle concentration of the same nanofluid. There is a significant increase in the viscosity at even low concentrations. Viscosity of nanofluids is also a strong function of temperature at all values of concentration considered in this study. The significant increase in viscosity may diminish nanofluids’ application as an advanced heat transfer fluid. The effects of nanofluid on the drag reduction and heat transfer enhancement are determined and compared with the pressure drop and heat transfer coefficient measurements with the base fluids at the same flow conditions. Our experimental measurements indicate that the pumping power to flow nanofluids is nearly the same as the pumping power required to flow the same amount of base fluid although the viscosity of nanofluids are significantly higher. Convective heat transfer enhancement with the nanofluids is limited to 5% or slightly higher as has also been reported by other workers. Hence addition of nanoparticles into heat transfer fluids could have the potential for heat transfer enhancement in pipe flow without paying the penalty of increasing pumping power.

Study of the boundary layer heat transfer of nanofluids over a stretching sheet: Passive control of nanoparticles at the surface

2015 ◽  
Vol 93 (7) ◽  
pp. 725-733 ◽  
Author(s):  
M. Ghalambaz ◽  
E. Izadpanahi ◽  
A. Noghrehabadi ◽  
A. Chamkha
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Boundary Layer ◽  
Nusselt Number ◽  
Heat Transfer Enhancement ◽  
Base Fluid ◽  
Stretching Sheet ◽  
Volume Fraction ◽  
Enhancement Ratio ◽  
Transfer Enhancement

The boundary layer heat and mass transfer of nanofluids over an isothermal stretching sheet is analyzed using a drift-flux model. The relative slip velocity between the nanoparticles and the base fluid is taken into account. The nanoparticles’ volume fractions at the surface of the sheet are considered to be adjusted passively. The thermal conductivity and the dynamic viscosity of the nanofluid are considered as functions of the local volume fraction of the nanoparticles. A non-dimensional parameter, heat transfer enhancement ratio, is introduced, which shows the alteration of the thermal convective coefficient of the nanofluid compared to the base fluid. The governing partial differential equations are reduced into a set of nonlinear ordinary differential equations using appropriate similarity transformations and then solved numerically using the fourth-order Runge–Kutta and Newton–Raphson methods along with the shooting technique. The effects of six non-dimensional parameters, namely, the Prandtl number of the base fluid Prbf, Lewis number Le, Brownian motion parameter Nb, thermophoresis parameter Nt, variable thermal conductivity parameter Nc and the variable viscosity parameter Nv, on the velocity, temperature, and concentration profiles as well as the reduced Nusselt number and the enhancement ratio are investigated. Finally, case studies for Al2O3 and Cu nanoparticles dispersed in water are performed. It is found that increases in the ambient values of the nanoparticles volume fraction cause decreases in both the dimensionless shear stress f″(0) and the reduced Nusselt number Nur. Furthermore, an augmentation of the ambient value of the volume fraction of nanoparticles results in an increase the heat transfer enhancement ratio hnf/hbf. Therefore, using nanoparticles produces heat transfer enhancement from the sheet.

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