scholarly journals Empirical correlations to predict thermophysical and heat transfer characteristics of nanofluids

2008 ◽  
Vol 12 (2) ◽  
pp. 27-37 ◽  
Author(s):  
Vasu Velagapudi ◽  
Krishna Konijeti ◽  
Kumar Aduru
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Ethylene Glycol ◽  
Volume Fraction ◽  
Solid Particles ◽  
Engine Oil ◽  
Fluid Temperature ◽  
Flow Conditions ◽  
Thermophysical Characteristics ◽  
Laminar And Turbulent Flow

Nanofluids exhibits larger thermal conductivity due to the presence of suspended nanosized solid particles in them such as Al2O3, Cu, CuO,TiO2, etc. Varieties of models have been proposed by several authors to explain the heat transfer enhancement of fluids such as water, ethylene glycol, engine oil containing these particles. This paper presents a systematic literature survey to exploit the thermophysical characteristics of nanofluids. Based on the experimental data available in the literature empirical correlation to predict the thermal conductivity of Al2O3, Cu, CuO, and TiO2 nanoparticles with water and ethylene glycol as base fluid is developed and presented. Similarly the correlations to predict the Nusselt number under laminar and turbulent flow conditions is also developed and presented. These correlations are useful to predict the heat transfer ability of nanofluids and takes care of variations in volume fraction, nanoparticle size and fluid temperature. The improved thermophysical characteristics of a nanofluid make it excellently suitable for future heat exchange applications. .

Pool Boiling Characteristics of Metallic Nanofluids

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
K. Hari Krishna ◽  
Harish Ganapathy ◽  
G. Sateesh ◽  
Sarit K. Das
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Boiling Heat Transfer ◽  
Volume Fraction ◽  
Pool Boiling ◽  
Heat Fluxes ◽  
Solid Particles ◽  
Heater Surface ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

Nanofluids, solid-liquid suspensions with solid particles of size of the order of few nanometers, have created interest in many researchers because of their enhancement in thermal conductivity and convective heat transfer characteristics. Many studies have been done on the pool boiling characteristics of nanofluids, most of which have been with nanofluids containing oxide nanoparticles owing to the ease in their preparation. Deterioration in boiling heat transfer was observed in some studies. Metallic nanofluids having metal nanoparticles, which are known for their good heat transfer characteristics in bulk regime, reported drastic enhancement in thermal conductivity. The present paper investigates into the pool boiling characteristics of metallic nanofluids, in particular of Cu-H2O nanofluids, on flat copper heater surface. The results indicate that at comparatively low heat fluxes, there is deterioration in boiling heat transfer with very low particle volume fraction of 0.01%, and it increases with volume fraction and shows enhancement with 0.1%. However, the behavior is the other way around at high heat fluxes. The enhancement at low heat fluxes is due to the fact that the effect of formation of thin sorption layer of nanoparticles on heater surface, which causes deterioration by trapping the nucleation sites, is overshadowed by the increase in microlayer evaporation, which is due to enhancement in thermal conductivity. Same trend has been observed with variation in the surface roughness of the heater as well.

scholarly journals Implicit Finite Difference Simulation of Prandtl-Eyring Nanofluid over a Flat Plate with Variable Thermal Conductivity: A Tiwari and Das Model

Mathematics ◽  
2021 ◽  
Vol 9 (24) ◽  
pp. 3153
Author(s):  
Nidal H. Abu-Hamdeh ◽  
Abdulmalik A. Aljinaidi ◽  
Mohamed A. Eltaher ◽  
Khalid H. Almitani ◽  
Khaled A. Alnefaie ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Finite Difference ◽  
Differential Equations ◽  
Ordinary Differential Equations ◽  
Variable Thermal Conductivity ◽  
Solid Particles ◽  
Engine Oil ◽  
Working Fluid ◽  
Implicit Finite Difference

The current article presents the entropy formation and heat transfer of the steady Prandtl-Eyring nanofluids (P-ENF). Heat transfer and flow of P-ENF are analyzed when nanofluid is passed to the hot and slippery surface. The study also investigates the effects of radiative heat flux, variable thermal conductivity, the material’s porosity, and the morphologies of nano-solid particles. Flow equations are defined utilizing partial differential equations (PDEs). Necessary transformations are employed to convert the formulae into ordinary differential equations. The implicit finite difference method (I-FDM) is used to find approximate solutions to ordinary differential equations. Two types of nano-solid particles, aluminium oxide (Al2O3) and copper (Cu), are examined using engine oil (EO) as working fluid. Graphical plots are used to depict the crucial outcomes regarding drag force, entropy measurement, temperature, Nusselt number, and flow. According to the study, there is a solid and aggressive increase in the heat transfer rate of P-ENF Cu-EO than Al2O3-EO. An increment in the size of nanoparticles resulted in enhancing the entropy of the model. The Prandtl-Eyring parameter and modified radiative flow show the same impact on the radiative field.

A Study on Uncertainties in Estimations of Thermal Conductivity of Alumina Nanofluids

2015 ◽  
Vol 809-810 ◽  
pp. 525-530 ◽  
Author(s):  
Madalina Georgiana Moldoveanu ◽  
Alina Adriana Minea
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Performance ◽  
Unsolved Problem ◽  
Volume Fraction ◽  
Solid Particles ◽  
Two Phase ◽  
Polymeric Particles ◽  
Semi Empirical ◽  
Thermal Conductivities

An innovative way of improving the thermal conductivities of fluids is to suspend small solid particles in the fluids. Various types of powders such as metallic, non-metallic and polymeric particles can be added into fluids to form slurries. The thermal conductivities of fluids with suspended particles are expected to be higher than that of common fluids. Application of nanoparticles provides an effective way of improving heat transfer characteristics of fluids. By suspending nanophase particles in heating or cooling fluids, the heat transfer performance of the fluid can be significantly improved. Moreover, the thermal conductivity of nanofluid is strongly dependent on the nanoparticle volume fraction. So far it has been an unsolved problem to develop a sophisticated theory to predict thermal conductivity of nanofluids, although there are some semi empirical correlations to calculate the apparent conductivity of two-phase mixture. In this article few correlations were considered and differences were noted between different theories. In conclusion, a lot of uncertainties in determining thermal conductivity were noticed.

scholarly journals AL2O3 Nanofluids as Heat Transfer Liquids in Automotives

2014 ◽  
pp. 206-212
Author(s):  
M. YASASWI ◽  
R.V. PRASAD ◽  
T.JAYANDA KUMAR
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Ethylene Glycol ◽  
Energy Efficient ◽  
Solid Particles ◽  
Al2o3 Nanoparticles ◽  
Particle Volume ◽  
Heat Transfer Fluids ◽  
Potential Impact ◽  
Efficient Heat Transfer

The thermal conductivity of heating or cooling fluids is a very important property in the development of energy efficient heat transfer systems, which is one of the important needs of many industries. However, low thermal conductivity is a primary limitation in developing energy-efficient heat transfer fluids that are required for cooling purposes. Nanofluids are nanotechnology-based heat transfer fluids that are engineered by stably dispersing nanometer-sized (below 100nm) solid particles (such as ceramics, metals, alloys, semiconductors, nanotubes, and composite particles) in conventional heat transfer fluids (such as water, oil, diesel, ethylene glycol and mixtures) at relatively low particle volume concentrations. These suspended nanoparticles can change the transport and thermal properties of the base fluid. Adding to ethylene glycol, it has been observed that an enhancement of nearly 36 % with al2o3 nanoparticles and 40% enhancement with copper nanoparticles in the thermal conductivity. This paper focuses on some of the automotive applications such as coolant for automobiles, showcases a few of them that are believed to have the highest probability of success in this highly competitive industry and to raise the awareness on the promise of nanotechnology, its potential impact on the future of the automotive industry.

Numerical Investigation for Convective Heat Transfer of CNT Nano-Fluids over a Stretching Surface

2019 ◽  
Vol 961 ◽  
pp. 148-155
Author(s):  
Muhaimin Ismoen ◽  
Radiah Bte Mohamad ◽  
R. Kandasamy ◽  
Suliadi Firdaus Sufahani ◽  
Fazlul Karim ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Ethylene Glycol ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Engine Oil ◽  
Magnetic Field Effects ◽  
Conductivity Enhancement ◽  
Similarity Transformations ◽  
Nano Fluids

The performance of carbon nanotube (CNT) nanofluids on convective heat transfer over a stretching sheet was investigated under thermal stratification and magnetic field effects. Water, engine oil and ethylene glycol are used as the base fluids. The governing equations are transformed into a system of coupled nonlinear ordinary differential equations using similarity transformations and solved numerically using the fourth-order Runge–Kutta–Fehlberg in conjunction to shooting method. The CNT nanofluids with an engine oil base fluid shows the highest thermal conductivity in comparison to ethylene glycol and water, respectively. Potential application of the thermal conductivity enhancement of CNT nanofluid is to increase the energy-efficient mechanical systems in heating, cooling and ventilation of the indoor environment.

scholarly journals Performance evaluation of Al2O3 nanofluid as an enhanced heat transfer fluid

2020 ◽  
Vol 12 (8) ◽  
pp. 168781402095227
Author(s):  
Minsuk Kong ◽  
Seungro Lee
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Pressure Drop ◽  
Volume Fraction ◽  
Experimental Results ◽  
Heat Transfer Fluid ◽  
Fluid Temperature ◽  
Overall Performance ◽  
C 30 ◽  
The Heat Transfer Coefficient

Thermal performance of Al2O3 nanoparticles dispersed in water was evaluated experimentally in a fully instrumented circular tube under turbulent flow conditions. Thermophysical properties of Al2O3 nanofluids at three different volumetric concentrations (0.38%, 0.81%, and 1.30%) were determined as a function of temperature. Pressure drop and heat transfer experiments were carried out at different volumetric concentrations and inlet fluid temperatures (10°C–30°C). The overall performance of the Al2O3 nanofluids was evaluated by considering both their hydraulic and heat transfer characteristics. The experimental results showed that the use of Al2O3 nanofluids increases the pressure drop by up to about 13% due to the greater viscosity. In addition, the heat transfer coefficient of nanofluids increased with the volumetric concentration by up to approximately 19% induced by the enhanced thermal conductivity. Furthermore, the experimental results indicated that the nanofluid with a volume fraction of 0.81% at the highest inlet fluid temperature increases the overall performance by up to around 8% and performs better than the other volume fractions. Enhancement in the overall performance increases with increasing inlet fluid temperature because of both the enhanced effective thermal conductivity and the decreased viscosity, which increases the energy exchange and decreases the pressure loss, respectively.

scholarly journals A sensitivity study on carbon nanotubes significance in Darcy–Forchheimer flow towards a rotating disk by response surface methodology

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Anum Shafiq ◽  
Tabassum Naz Sindhu ◽  
Qasem M. Al-Mdallal
Keyword(s):  
Heat Transfer ◽  
Carbon Nanotubes ◽  
Ethylene Glycol ◽  
Biot Number ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Rotating Disk ◽  
Sensitivity Study ◽  
Basic Fluid ◽  
Walled Cnts

AbstractThe current research explores incremental effect of thermal radiation on heat transfer improvement corresponds to Darcy–Forchheimer (DF) flow of carbon nanotubes along a stretched rotating surface using RSM. Casson carbon nanotubes’ constructed model in boundary layer flow is being investigated with implications of both single-walled CNTs and multi-walled CNTs. Water and Ethylene glycol are considered a basic fluid. The heat transfer rate is scrutinized via convective condition. Outcomes are observed and evaluated for both SWCNTs and MWCNTs. The Runge–Kutta Fehlberg technique of shooting is utilized to numerically solve transformed nonlinear ordinary differential system. The output parameters of interest are presumed to depend on governing input variables. In addition, sensitivity study is incorporated. It is noted that sensitivity of SFC via SWCNT-Water becomes higher by increasing values of permeability number. Additionaly, sensitivity of SFC via SWCNT-water towards the permeability number is higher than the solid volume fraction for medium and higher permeability levels. It is also noted that sensitivity of SFC (SWCNT-Ethylene-glycol) towards volume fraction is higher for increasing permeability as well as inertia coefficient. Additionally, the sensitivity of LNN towards the Solid volume fraction is higher than the radiation and Biot number for all levels of Biot number. The findings will provide initial direction for future device manufacturing.

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.

Quantitative Experimental Study of SiO2-Water Nanofluids on Backward-Facing Step Flow under Low Reynolds Number

2018 ◽  
Vol 916 ◽  
pp. 221-225
Author(s):  
Ji Zu Lv ◽  
Liang Yu Li ◽  
Cheng Zhi Hu ◽  
Min Li Bai ◽  
Sheng Nan Chang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Reynolds Number ◽  
Volume Fraction ◽  
Pure Water ◽  
Experimental Studies ◽  
Flow Characteristics ◽  
Thermal Engineering ◽  
Heat Transfer Medium ◽  
Step Flow

Nanofluids is an innovative study of nanotechnology applied to the traditional field of thermal engineering. It refers to the metal or non-metallic nanopowder was dispersed into water, alcohol, oil and other traditional heat transfer medium, to prepared as a new heat transfer medium with high thermal conductivity. The role of nanofluids in strengthening heat transfer has been confirmed by a large number of experimental studies. Its heat transfer mechanism is mainly divided into two aspects. On the one hand, the addition of nanoparticles enhances the thermal conductivity. On the other hand, due to the interaction between the nanoparticles and base fluid causing the changes in the flow characteristics, which is also the main factor affecting the heat transfer of nanofluids. Therefore, a intensive study on the flow characteristics of nanofluids will make the study of heat transfer more meaningful. In this experiment, the flow characteristics of SiO2-water nanofluids in two-dimensional backward step flow are quantitatively studied by PIV. The results show that under the same Reynolds number, the turbulence of nanofluids is larger than that of pure water. With the increase of nanofluids volume fraction, the flow characteristics are constantly changing. The quantitative analysis proved that the nanofluids disturbance was enhanced compared with the base liquid, which resulting in the heat transfer enhancement.

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