A critical synthesis of thermophysical characteristics of nanofluids

Khanafer, Khalil; Vafai, Kambiz

doi:10.1016/j.ijheatmasstransfer.2011.04.048

Cited by 940 publications

(252 citation statements)

References 107 publications

(173 reference statements)

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“…On one hand, the correlation gives the viscosity value close to the experimental values when compared with earlier models proposed by Einstein and later modified by Brinkman [40] as well as one also proposed by Batchelor [41]. On the other hand, the expression of correlation is simpler than some recent models [42]. Besides, the correlation can give the viscosity for water-Al 2 O 3 nanofluids with particle concentration up to 6%.…”

Section: Properties Of Nanofluidssupporting

confidence: 82%

Entropy Generation Analysis and Performance Evaluation of Turbulent Forced Convective Heat Transfer to Nanofluids

Zhang

Xie

et al. 2017

Entropy

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Abstract:The entropy generation analysis of fully turbulent convective heat transfer to nanofluids in a circular tube is investigated numerically using the Reynolds Averaged Navier-Stokes (RANS) model. The nanofluids with particle concentration of 0%, 1%, 2%, 4% and 6% are treated as single phases of effective properties. The uniform heat flux is enforced at the tube wall. To confirm the validity of the numerical approach, the results have been compared with empirical correlations and analytical formula. The self-similarity profiles of local entropy generation are also studied, in which the peak values of entropy generation by direct dissipation, turbulent dissipation, mean temperature gradients and fluctuating temperature gradients for different Reynolds number as well as different particle concentration are observed. In addition, the effects of Reynolds number, volume fraction of nanoparticles and heat flux on total entropy generation and Bejan number are discussed. In the results, the intersection points of total entropy generation for water and four nanofluids are observed, when the entropy generation decrease before the intersection and increase after the intersection as the particle concentration increases. Finally, by definition of E p , which combines the first law and second law of thermodynamics and attributed to evaluate the real performance of heat transfer processes, the optimal Reynolds number Re op corresponding to the best performance and the advisable Reynolds number Re ad providing the appropriate Reynolds number range for nanofluids in convective heat transfer can be determined.

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Section: Properties Of Nanofluidssupporting

confidence: 82%

Entropy Generation Analysis and Performance Evaluation of Turbulent Forced Convective Heat Transfer to Nanofluids

Zhang

Xie

et al. 2017

Entropy

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“…This pressure level (p low ) is the saturation pressure for heat rejection temperature level (T hr ). The produced power (P el ) in the electrical generator is calculated according to Equation (32):…”

Section: Orc Modelingmentioning

confidence: 99%

Optimization of a Solar-Driven Trigeneration System with Nanofluid-Based Parabolic Trough Collectors

Bellos

Tzivanidis

2017

Energies

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Abstract:The objective of this work was to optimize and to evaluate a solar-driven trigeneration system which operates with nanofluid-based parabolic trough collectors. The trigeneration system includes an organic Rankine cycle (ORC) and an absorption heat pump operating with LiBr-H 2 O which is powered by the rejected heat of the ORC. Toluene, n-octane, Octamethyltrisiloxane (MDM) and cyclohexane are the examined working fluids in the ORC. The use of CuO and Al 2 O 3 nanoparticles in the Syltherm 800 (base fluid) is investigated in the solar field loop. The analysis is performed with Engineering Equation Solver (EES) under steady state conditions in order to give the emphasis in the exergetic optimization of the system. Except for the different working fluid investigation, the system is optimized by examining three basic operating parameters in all the cases. The pressure in the turbine inlet, the temperature in the ORC condenser and the nanofluid concentration are the optimization variables. According to the final results, the combination of toluene in the ORC with the CuO nanofluid is the optimum choice. The global maximum exergetic efficiency is 24.66% with pressure ratio is equal to 0.7605, heat rejection temperature 113.7 • C and CuO concentration 4.35%.

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“…Nanofluids are suspensions of nano-sized solid particles in base fluids that can have higher thermal properties compared to that of base fluids, making them more efficient for heat transfer applications. Over the past years, many studies have been conducted for nanofluids for showing their better thermal properties and thermal performances as well as for understating the mechanisms of heat transport in nanofluids [13][14][15][16][17][18]. For instance, Eastman and co-authors [13] showed that a significant improvement in thermal conductivity of CuO-water nanofluid with 5% of nanocrystalline CuO particles suspended in water.…”

Section: Introductionmentioning

confidence: 99%

Constructal Design of a Rectangular Fin in a Mixed Convective Confined Environment

et al. 2018

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Extended surfaces or fins offer an efficient solution in many engineering situations that demand a higher heat transfer, including cooling gas-turbine components and electronic chips via internal convective flows. However, fins require a higher active surface area for higher heat transfer, which may not be always feasible in a confined environment. A feasible solution to enhance heat transfer from fins can be the use of nanofluids, which are the combination of a fluid base and nanoparticles. The main purpose of this study is, therefore, to optimize a rectangular fin intruded into the mixed convective confined space filled with a nanofluid and by means of constructal design. Here, a two-dimensional macroscopic numerical model has been developed for Al 2 O 3 -water nanofluid to investigate the heat transfer and fluid flow inside a square confined-space with an intruded rectangular fin and to optimize the fin geometry for maximizing the heat transfer using the constructal design method. The flow fields, temperature fields, heat transfer rates, and the transition from forced to mixed convection are examined for different values of Rayleigh and Reynolds numbers for various fin geometries in order to maximize the heat transfer from the fin to the surrounding nanofluid flow. The outcome of this study provides important insights into the constructal design method for the confined environment, which would be beneficial in developing novel fin geometries with enhanced and controlled heat-transfer for engineering problems, including cooling gas-turbine components and electronic chips.

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A critical synthesis of thermophysical characteristics of nanofluids

Cited by 940 publications

References 107 publications

Entropy Generation Analysis and Performance Evaluation of Turbulent Forced Convective Heat Transfer to Nanofluids

Entropy Generation Analysis and Performance Evaluation of Turbulent Forced Convective Heat Transfer to Nanofluids

Optimization of a Solar-Driven Trigeneration System with Nanofluid-Based Parabolic Trough Collectors

Constructal Design of a Rectangular Fin in a Mixed Convective Confined Environment

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