Numerical Assessment of Nanofluids in Recharging Microchannel: Thermo-Hydrodynamic and Entropy Generation Analysis

2021 ◽  
pp. 1-45
Author(s):  
Sangram Kumar Samal ◽  
Manoj K. Moharana
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Entropy Generation ◽  
Volume Concentration ◽  
Particle Diameter ◽  
Hydrodynamic Performance ◽  
Water Based ◽  
Effectiveness Parameter ◽  
Al2o3 Nanofluid

Abstract In this work three-dimensional numerical study is presented that deals with thermo-hydrodynamic performance and entropy generation in recharging microchannel using water-based nanofluids. Four different water-based nanofluids (Al2O3, CuO, SiO2, and ZnO) are considered with volume concentration and nanoparticle diameter varied in the range of 1% to 5%, and 10 nm to 50 nm respectively to understand their effect on thermo-hydrodynamic performance and entropy generation. Constant wall heat flux of 100 W/cm2 is applied on the substrate bottom surface while coolant flows through recharging microchannel with Reynolds number Re = 100 to 500. It is revealed that among all the nanofluids under investigation, water/Al2O3 provides enhanced thermal performance with higher effectiveness parameter (η), and it also shows reduced entropy generation in recharging microchannel. With increasing volume concentration of water/Al2O3 nanofluid, heat transfer coefficient increases, effectiveness parameter increases, and entropy generation reduces. Water/Al2O3 nanofluid with smaller particle diameter shows enhanced heat transfer coefficient, and reduced entropy generation, whereas it shows decreased effectiveness parameter. This is attributed to increased pressure drop with decreasing particle diameter. This study suggest that optimized combination of particle diameter and volume concentration should be chosen for using nanofluid based coolants for high heat flux removal.

Energy and Exergy Analysis of Shell and Coil Heat Exchanger Using Water Based Al2O3 Nanofluid Including Diverse Coil Geometries: An Experimental Study

2020 ◽  
Vol 9 (1) ◽  
pp. 13-23
Author(s):  
Samir M. Elshamy ◽  
Mohamed T. Abdelghany ◽  
M. R. Salem ◽  
O. E. Abdellatif
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Exergy Analysis ◽  
Volume Concentration ◽  
Pure Water ◽  
Cone Angle ◽  
Particle Volume ◽  
Water Based ◽  
Coil Heat

The aim of this research is to investigate experimentally the characteristics of the convective heat transfer and exergy analysis of pure water and water based Al2O3 nanofluid through helical coiled tubes (HCTs) and conical coiled tubes (CCTs) inside shell and coil heat exchangers. HCT and CCT fabricated with different coil torsions (λ) ranges from 0.0202 to 0.052 with different two angles (0° and 45°) while have the same curvature ratio (δ = 0.0564). The effects of mean coil torsion, the cone angle and nanoparticles volume concentration on the thermal performance were investigated. Results indicated that the overall heat transfer coefficient (Uov), convection heat transfer coefficient (ht), the tube side Nusselt number (Nut), effectiveness (ɛ) and exergy efficiency (ηex) of nanofluids are higher than those of the pure water at same flow condition, and this increase goes up with the increase in particle volume concentration (ϕ). The results also showed that Uov, ht, Nut, ɛ and ηex increases by decreasing the coil torsion from 0.052 to 0.0202. Correlations for Nut as a function of the investigated parameters are obtained.

Effect of Wall Heat Flux on Entropy Generation in Turbulent Mixed Convection Heat Transfer of a Pipe Flow With Highly Variable Properties

2010 ◽  
Author(s):  
Majid Bazargan ◽  
Mahdi Mohseni
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Entropy Production ◽  
Entropy Generation ◽  
Convection Heat Transfer ◽  
Wall Heat Flux ◽  
Convection Heat ◽  
The Heat Transfer Coefficient

There are many engineering systems with working fluids which have properties varying significantly with temperature. This causes the effect of the wall heat flux on the velocity and temperature fields to become larger with respect to the constant property flows. In this study the effect of the wall heat flux on the entropy generation in the mixed turbulent convection heat transfer of a fluid flow with high property variations has been investigated. The local and total entropy generation is calculated. In addition, the region in which the entropy production is larger has been determined. Furthermore, the contribution of each of the mechanisms of entropy production which is depended on the wall heat flux is determined. It should be noted that the implementation of different heat fluxes at the tube wall affects all mechanisms of entropy generation. The results show that the bulk entropy generation reaches a minimum value when the heat transfer coefficient has a maximum value. The wall heat flux also has an opposite effect on the heat transfer coefficient and entropy generation which is a favorable result.

Numerical Study on Conjugated Laminar Mixed Convection of Alumina/Water Nanofluid Flow, Heat Transfer, and Entropy Generation Within a Tube-on-Sheet Flat Plate Solar Collector

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Mohammad Charjouei Moghadam ◽  
Mojtaba Edalatpour ◽  
Juan P. Solano
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Entropy Generation ◽  
Solar Collector ◽  
Richardson Number ◽  
Volume Concentration ◽  
Volume Fraction ◽  
Flat Plate Solar Collector

In this research, an inclined three-dimensional nanofluid-based tube-on-sheet flat plate solar collector (FPSC) working under laminar conjugated mixed convection heat transfer is numerically modeled. The working fluid is selected to be alumina/water (Al2O3/water) and results from heat transfer, entropy generation, and pressure drop points of view are being presented for various prominent parameters, namely volume fraction, nanoparticles diameter, Richardson and Reynolds numbers. According to the simulations, Nusselt number decreases as the Richardson number or volume fraction of the nanofluid rises, whereas heat transfer coefficient experiences an augmentation when volume concentration and the Richardson number surge. Also, data reveal that total entropy generation rate of the system declines when the alumina/water nanofluid is utilized inside the system as the volume fraction or the Richardson number increases. Additionally, it is found that increasing the nanoparticle volume concentration or the Richardson number diminishes the pressure drop considerably, whereas friction factor substantially proliferates as the Richardson number or volume fraction rises. Eventually, employment of larger alumina nanoparticles mean diameter eventuates in providing lower Nusselt number and apparent friction factor while it increases the pressure drop and heat transfer coefficient. Finally, comparing the efficiency of the presented FPSC design with those available in the literature shows a superior performance by the present design with its maximum occurring at 2 vol %.

scholarly journals Numerical Study of Laminar Flow Forced Convection of Water-Al2O3Nanofluids under Constant Wall Temperature Condition

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Hsien-Hung Ting ◽  
Shuhn-Shyurng Hou
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Volume Concentration ◽  
Numerical Study ◽  
Pure Water ◽  
Particle Volume ◽  
Constant Wall Temperature ◽  
Water Based

This numerical study is aimed at investigating the forced convection heat transfer and flow characteristics of water-based Al2O3nanofluids inside a horizontal circular tube in the laminar flow regime under the constant wall temperature boundary condition. Five volume concentrations of nanoparticle, 0.1, 0.5, 1, 1.5, and 2 vol.%, are used and diameter of nanoparticle is 40 nm. Characteristics of heat transfer coefficient, Nusselt number, and pressure drop are reported. The results show that heat transfer coefficient of nanofluids increases with increasing Reynolds number or particle volume concentration. The heat transfer coefficient of the water-based nanofluid with 2 vol.% Al2O3nanoparticles is enhanced by 32% compared with that of pure water. Increasing particle volume concentration causes an increase in pressure drop. At 2 vol.% of particle concentration, the pressure drop reaches a maximum that is nearly 5.7 times compared with that of pure water. It is important to note that the numerical results are in good agreement with published experimental data.

scholarly journals Effect of Low Volume Concentration on Heat Transfer Enhancement of EG-Water Based Fe3O4 Nanofluid

2020 ◽  
Vol 9 (4) ◽  
pp. 1796-1802
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Transfer Enhancement ◽  
Friction Factor ◽  
Base Fluid ◽  
Volume Concentration ◽  
Transfer Enhancement ◽  
Water Based ◽  
The Heat Transfer Coefficient

Customization of thermophysical properties of the working fluids has tremendous potential in heat transfer enhancement. In the present paper, experimentation is conducted to determine the heat transfer coefficient and friction factor of 20:80 Ethylene Glycol-Water(20:80 EG-Water) based Fe3O4 nanofluid in a Double Pipe Heat Exchanger with U Bend (DPHE). Experiments are performed in the turbulent flow regime at an operating temperature of 47.5°C. Fe3O4 nanoparticles of size less than 50 nm are mixed with 20:80 EG-Water solution in the volume concentration range of 0.02% to 0.08%. Results indicate that as the concentration of nanoparticles increase, the heat transfer coefficient of the nanofluid increases up to 0.04% concentration and then decreases, while the friction factor is observed to increase with the increase of volume concentration. Within the Reynolds number range considered in the analysis, the average enhancement in the heat transfer coefficient is 24.1% at 0.04% concentration compared to that of the base fluid. The average enhancement in the friction factor is observed to be 25.58% at 0.08% concentration of Fe3O4 / 20:80 EG-Water nanofluid compared to that of base fluid.

scholarly journals Experimental Determination of the Heat Transfer Coefficient of Real Cooled Geometry Using Linear Regression Method

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 180
Author(s):  
Asif Ali ◽  
Lorenzo Cocchi ◽  
Alessio Picchi ◽  
Bruno Facchini
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Linear Regression ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
External Surface ◽  
Internal Surface ◽  
Regression Method ◽  
Thermal Transient

The scope of this work was to develop a technique based on the regression method and apply it on a real cooled geometry for measuring its internal heat transfer distribution. The proposed methodology is based upon an already available literature approach. For implementation of the methodology, the geometry is initially heated to a known steady temperature, followed by thermal transient, induced by injection of ambient air to its internal cooling system. During the thermal transient, external surface temperature of the geometry is recorded with the help of infrared camera. Then, a numerical procedure based upon a series of transient finite element analyses of the geometry is applied by using the obtained experimental data. The total test duration is divided into time steps, during which the heat flux on the internal surface is iteratively updated to target the measured external surface temperature. The final procured heat flux and internal surface temperature data of each time step is used to find the convective heat transfer coefficient via linear regression. This methodology is successfully implemented on three geometries: a circular duct, a blade with U-bend internal channel, and a cooled high pressure vane of real engine, with the help of a test rig developed at the University of Florence, Italy. The results are compared with the ones retrieved with similar approach available in the open literature, and the pros and cons of both methodologies are discussed in detail for each geometry.

scholarly journals Darcy-Brinkman free convection about a wedge and a cone subjected to a mixed thermal boundary condition

1992 ◽  
Vol 15 (4) ◽  
pp. 789-794 ◽  
Author(s):  
G. Ramanaiah ◽  
V. Kumaran
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Flux ◽  
Porous Medium ◽  
Heat Transfer Coefficient ◽  
Free Convection ◽  
Transformation Group ◽  
Darcy Number ◽  
Thermal Boundary Condition ◽  
High Porosity

The Darcy-Brinkman free convection near a wedge and a cone in a porous medium with high porosity has been considered. The surfaces are subjected to a mixed thermal boundary condition characterized by a parameterm;m=0,1,∞correspond to the cases of prescribed temperature, prescribed heat flux and prescribed heat transfer coefficient respectively. It is shown that the solutions for differentmare dependent and a transformation group has been found, through which one can get solution for anymprovided solution for a particular value ofmis known. The effects of Darcy number on skin friction and rate of heat transfer are analyzed.

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