scholarly journals MHD Mixed Convection and Entropy Generation in a Lid-Driven Triangular Cavity for Various Electrical Conductivity Models

Entropy ◽  
2018 ◽  
Vol 20 (12) ◽  
pp. 903 ◽  
Author(s):  
Ali Chamkha ◽  
Fatih Selimefendigil ◽  
Hakan Oztop
Keyword(s):  
Heat Transfer ◽  
Electrical Conductivity ◽  
Entropy Generation ◽  
Richardson Number ◽  
Hartmann Number ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Entropy Generation Rate ◽  
Particle Volume ◽  
Conductivity Models

In this study, effects of different electrical conductivity models for magneto- hydrodynamic mixed convection of nanofluids in a lid-driven triangular cavity was numerically investigated with a finite element method. Effects of Richardson number and Hartmann number on the convective heat transfer characteristics were analyzed for various electrical conductivity models of nanofluids. Average Nusselt number decreases for higher Hartmann and Richardson numbers. Discrepancies in the local and average heat transfer exist between different electrical conductivity models, which is higher for higher values of Richardson number and Hartmann number. The total entropy generation rate was found reduced with higher values of Richardson number and Hartmann number while discrepancies exist between various electrical conductivity models. When the magnetic field is imposed, different behaviors of entropy generation rate versus solid particle volume fraction curve is obtained and it is dependent upon the range of solid particle volume fraction.

scholarly journals Effects of magnetic field inclination and internal heat sources on nanofluid heat transfer and entropy generation in a double lid driven L-shaped cavity

2019 ◽  
pp. 325-325 ◽  
Author(s):  
Ali Chamkha ◽  
Zeinab Abdelrahman ◽  
Mohamed Mansour ◽  
Taher Armaghani ◽  
Ahmed Rashad
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Heat Source ◽  
Mixed Convection ◽  
Entropy Generation ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Internal Heat ◽  
Performance Criteria ◽  
Particle Volume

Mixed convection has been one of the most interesting subjects of study in the area of heat transfer for many years. The entropy generation due to MHD mixed convection heat transfer in L-shaped enclosure being filled with Cu-water nanofluid and having an internal heating generation is explored in this investigation by the finite volume technique. Lid-motion is presented by both right and top parts of walls to induce forced convection and the cavity is under an inclined uniform magnetic field along the positive horizontal direction. The statistics concentrated specifically on the impacts of several key parameters like as the aspect ratio of the enclosure, Hartmann number, nano-particle volume fraction, and heat source length/location on the heat transfer inside the L-shaped enclosure. Outcomes have been manifested in terms of isotherm lines, streamlines, local and average Nusselt numbers. The obtained results show that addition of nanoparticles into pure fluid leads to increase of heat transfer. The maximum value of local Nusselt pertaining to the heat source occurs when L=0.1. Impacts of heat source size and location, internal heat generation absorption, angle of magnetic field on heat transfer and entropy generation are completely analyzed and discussed. The best configuration and values of important parameters are also presented using thermal performance criteria.

Experimental Investigation of Submerged Impinging Jet Using Cu-Water Nanofluid

2010 ◽  
Author(s):  
Qiang Li ◽  
Yimin Xuan ◽  
Feng Yu ◽  
Junjie Tan
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Volume Fraction ◽  
Cooling System ◽  
Heated Surface ◽  
Particle Volume Fraction ◽  
Jet Impingement ◽  
Particle Volume ◽  
Impingement Cooling ◽  
System Pressure

An experimental investigation was performed to study the heat transfer and flow features of Cu-water nanofluids (Cu particles with 26 nm diameter) in a submerged jet impingement cooling system. Three particular nozzle-to-heated surface distances (2, 4 and 6 mm) and four particle volume fractions (1.5%, 2.0%, 2.5% and 3.0%) are involved in the experiment. The experimental results reveal that the suspended nanoparticles increase the heat transfer performance of the base liquid in the jet impingement cooling system. Within the range of experimental parameters considered, it has been found that highest surface heat transfer coefficients can be achieved using a nozzle-to-surface distance of 4 mm and the nanofluid with 3.0% particle volume fraction. In addition, the experiments show that the system pressure drop of the dilute nanofluids is almost equal to that of water under the same entrance velocity.

scholarly journals Numerical analysis of heat transfer enhancement with the use of γ-Al2O3/water nanofluid and longitudinal ribs in a curved duct

2012 ◽  
Vol 16 (2) ◽  
pp. 469-480 ◽  
Author(s):  
Hosseinali Soltanipour ◽  
Parisa Choupani ◽  
Iraj Mirzaee
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Base Fluid ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Transfer Enhancement ◽  
Dean Number ◽  
Particle Volume ◽  
The Heat Transfer Coefficient

This paper presents a numerical investigation of heat transfer augmentation using internal longitudinal ribs and ?-Al2O3/ water nanofluid in a stationary curved square duct. The flow is assumed 3D, steady, laminar, and incompressible with constant properties. Computations have been done by solving Navier-Stokes and energy equations utilizing finite volume method. Water has been selected as the base fluid and thermo- physical properties of ?- Al2o3/ water nanofluid have been calculated using available correlations in the literature. The effects of Dean number, rib size and particle volume fraction on the heat transfer coefficient and pressure drop have been examined. Results show that nanoparticles can increase the heat transfer coefficient considerably. For any fixed Dean number, relative heat transfer rate (The ratio of the heat transfer coefficient in case the of ?- Al2o3/ water nanofluid to the base fluid) increases as the particle volume fraction increases; however, the addition of nanoparticle to the base fluid is more useful for low Dean numbers. In the case of water flow, results indicate that the ratio of heat transfer rate of ribbed duct to smooth duct is nearly independent of Dean number. Noticeable heat transfer enhancement, compared to water flow in smooth duct, can be achieved when ?-Al2O3/ water nanofluid is used as the working fluid in ribbed duct.

A Comparison on the Heat Transfer and Flow Characteristics of TiO2-Water Nanofluids Having Two Different Chemical Agents

2010 ◽  
Author(s):  
Weerapun Duangthongsuk ◽  
Somchai Wongwises
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Flow Characteristics ◽  
Average Diameter ◽  
Transfer Performance ◽  
Particle Volume ◽  
Tube Heat Exchanger ◽  
Two Samples

Heat transfer performance and flow characteristics of aqueous TiO2 nanofluids with particle volume fraction of 0.2% flowing under turbulent flow regime are investigated. The test section is a 1.5 m long counter-flow double tube heat exchanger. Two different nanofluids are used as working fluids at the same concentration. Firstly, TiO2 nanoparticles with mean diameters of 21 nm mixed with small amount of CTAB (about 0.01%) named “SAM 1”. Secondly, VP Disp. W740x provided by DEGUSSA AG Company is used and called “SAM 2”. The latter mixture is composed of TiO2 nanoparticle with average diameter of 21 nm dispersed in water. The pH values of nanofluid SAM 1 and SAM 2 are 7.6 and 7.5, respectively. The heat transfer performance and friction characteristics of two samples of nanofluid were presented. In addition, the Nusselt numbers predicted from the published correlation for nanofluids are compared with the present experimental data.

Laminar Convective Nanofluid Flow Over a Backward-Facing Step With an Elastic Bottom Wall

2018 ◽  
Vol 10 (4) ◽  
Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Öztop
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Elastic Modulus ◽  
Solid Particle ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Bottom Wall ◽  
Backward Facing Step ◽  
Particle Volume ◽  
Flexible Wall

In the present study, laminar forced convective nanofluid flow over a backward-facing step was numerically investigated. The bottom wall downstream of the step was flexible, and finite element method was used to solve the governing equations. The numerical simulation was performed for a range of Reynolds number (between 25 and 250), elastic modulus of the flexible wall (between 104 and 106), and solid particle volume fraction (between 0 and 0.035). It was observed that the flexibility of the bottom wall results in the variation of the fluid flow and heat transfer characteristics for the backward-facing step problem. As the value of Reynolds number and solid particle volume fraction enhances, local and average heat transfer rates increase. At the highest value of Reynolds number, heat transfer rate is higher for the case with the wall having lowest value of elastic modulus whereas the situation is reversed for other value of Reynolds number. Average Nusselt number reduces by about 9.21% and increases by about 6.1% for the flexible wall with the lowest elastic modulus as compared to a rigid bottom wall for Reynolds number of 25 and 250. Adding nano-additives to the base fluid results in higher heat transfer enhancements. Average heat transfer rates enhance by about 35.72% and 35.32% at the highest solid particle volume fraction as compared to nanofluid with solid volume fraction of 0.01 for the case with wall at the lowest and highest elastic modulus. A polynomial type correlation for the average Nusselt number along the flexible hot wall was proposed, which is dependent on the elastic modulus and solid particle volume fraction. The results of this study are useful for many thermal engineering problems where flow separation and reattachment coupled with heat transfer occur. Control of convective heat transfer for such configurations with wall flexibility and nanoparticle inclusion to the base fluid was aimed in this study to find the effects of various pertinent parameters for heat transfer enhancement.

scholarly journals Improved Heat Transfer in Guar Gel Composites Reinforced with Randomly Distributed Glass Microspheres

2021 ◽  
Author(s):  
Ruifeng CAO ◽  
Taotao WANG ◽  
Yuxuan ZHANG ◽  
Hui WANG
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Particle Size ◽  
Composite Materials ◽  
Effective Thermal Conductivity ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Glass Microspheres ◽  
Particle Volume ◽  
Number Of Particles

Improved heat transfer in composites consisting of guar gel matrix and randomly distributed glass microspheres is extensively studied to predict the effective thermal conductivity of composites using the finite element method. In the study, the proper and probabilistic three-dimensional random distribution of microspheres in the continuous matrix is automatically generated by a simple and efficient random sequential adsorption algorithm which is developed by considering the correlation of three factors including particle size, number of particles, and particle volume fraction controlling the geometric configuration of random packing. Then the dependences of the effective thermal conductivity of composite materials on some important factors are investigated numerically, including the particle volume fraction, the particle spatial distribution, the number of particles, the nonuniformity of particle size, the particle dispersion morphology and the thermal conductivity contrast between particle and matrix. The related numerical results are compared with theoretical predictions and available experimental results to assess the validity of the numerical model. These results can provide good guidance for the design of advanced microsphere reinforced composite materials.

The Effect of Using Nanofluids on Triangular Microchannel Heat Exchanger Performance

2010 ◽  
Author(s):  
G. Bhaskaran ◽  
H. A. Mohammed ◽  
N. H. Shuaib
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Volume Fraction ◽  
Numerical Study ◽  
Particle Volume Fraction ◽  
Three Dimensional ◽  
Hydrodynamic Performance ◽  
Particle Volume ◽  
Microchannel Heat Exchanger

A numerical study is performed to study the effects of using various types of nanofluids on a triangular shaped microchannel heat exchanger (MCHE). The performance of an aluminum MCHE with various types of nanofluids such as Al2O3, CuO, SiO2, Ag and TiO2 and diamond particles with particle volume fraction of 2% using water as base fluid is comprehensively analyzed. The three-dimensional steady, laminar developing flow and conjugate heat transfer of a balanced MCHE were solved using finite volume method. In order to maintain laminar flow in the microchannels, Re number was ranged from 100 to 800. The other parameters tested in this study include the effects of Reynolds number towards the temperature, effectiveness and pressure drop of the MCHE. It is found that nanofluids have improved the temperature profile and heat transfer rate of the MCHE. The increase in pressure drop was minimal while the thermal and hydrodynamic performance of the heat exchanger was enhanced.

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 %.

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