Effects Of Nanoparticle Volume Fraction Research Articles

Investigation of engines radiator heat recovery using different shapes of nanoparticles in H2O/(CH2OH)2 based nanofluids

In this paper, a flat tube of an engine radiator is modeled numerically for improving the cooling process or heat recovery of the engine using nanofluids. Two hydrogen based fluids (water (H2O) and ethylene glycol or EG ((CH2OH)2) and four nanoparticles (CuO, TiO2, Al2O3 and Fe3O4) in different shapes (Brick, Cylindrical, Platelet and Spherical) are considered for modeling the nanofluids in four different Reynolds numbers (500, 1000, 1500 and 2000). Hamilton correlation is used to calculate the thermal conductivity of nanofluids in different shapes of nanoparticles. Furthermore, the effect of nanoparticles volume fraction on the Nusselt number for all nanoparticle shapes is discussed in this study. Results show that EG-TiO2 with platelet shape and larger volume fraction of nanoparticles has the best cooling performance for the engine among other modeled nanofluids.

Three-dimensional computational fluid dynamics modeling of TiO2/R134a nanorefrigerant

In this study, numerical investigations were carried out for R134a based TiO2 nanorefrigerants. Forced laminar flow and heat transfer of nanorefrigerants in a horizontal smooth circular cross-sectioned duct were investigated under steady-state condition. The nanorefrigerants consist of TiO2 nanoparticles suspended in R134a as a base fluid with four particle volume fractions of 0.8, 2.0 and 4.0%. Numerical studies were performed under laminar flow conditions where Reynolds numbers range from 8?102 to 2.2?103. Flow is flowing in the duct with hydrodynamically and thermally developing (simultaneously developing flow) condition. The uniform surface heat flux with uniform peripheral wall heat flux (H2) boundary condition was applied on the duct wall. Commercial CFD software, Ansys Fluent 14.5, was used to carry out the numerical study. Effect of nanoparticle volume fraction on the average convective heat transfer coefficient and average Darcy friction factor were analyzed. It is obtained in this study that increasing nanoparticle volume fraction of nanorefrigerant increases the convective heat transfer in the duct; however, increasing nanoparticle volume fraction does not influence the pressure drop in the duct. The velocity and temperature distribution in the duct for different Reynolds numbers and nanoparticle volume fractions were presented.

Evaluation of wavy direct absorption solar collector (DASC) performance using different nanofluids

Abstract In this paper, thermal performance of a wavy nanofluid-based direct absorption solar collector (DASC) is evaluated using finite element method (FEM) by FlexPDE commercial package software. After presenting the governing equations and solving them by FEM, TiO2, Al2O3 and CuO nanoparticles are considered to make water-based nanofluid in the collector. Due to three different wall types in the problem (bottom wavy wall, flat top wall and vertical side walls) and three different boundary condition types (insulated, constant heat flux and constant temperature), the problem is solved for the more appropriate conditions. For all tested nanofluids, the effect of nanoparticles volume fraction is also investigated on the local/average Nusselt numbers. Results show that wavy collectors have larger maximum Nusselt number compared to flat plate collectors. Furthermore, the most Nusselt numbers are reported for TiO2 nanoparticles in the little volume fractions.

A Micromechanical Model for Effective Thermo-elastic Properties of Nanocomposites with Graded Properties of Interphase

In this study, a micromechanics-based analytical model is proposed to evaluate the effective thermo-elastic properties of polymer matrix nanocomposite materials. Accuracy, simplicity and efficiency are the main features of this micromechanical model. The constituents of representative volume element of nanocomposites are treated as three distinct phases, consisting of nanofiller, polymer matrix and interphase around the nanofiller. Young’s modulus and coefficient of thermal expansion of the interphase are continuously graded from those of the nanofiller to those of the polymer matrix. The effects of nanoparticle volume fraction, nanoparticle size, interphase thickness, nanofiller aspect ratio and number of layers in the interphase on the thermo-elastic properties of nanocomposites are studied. The comparison of results of the presented model with experimental data and other available micromechanical analysis demonstrates the validity of the proposed micromechanical model in the case of response of nanocomposites with graded properties of interphase.

Numerical investigation of nanofluid flow and conjugated heat transfer in a micro-heat-exchanger using the lattice Boltzmann method

ABSTRACTIn this article, simulation of nanofluid flow and conjugated heat transfer in a micro-heat-exchanger is studied using the lattice Boltzmann method. Hot and cold streams enter the heat exchanger in opposite directions and heat transfer occurs between the two streams through a wall. The effect of nanoparticles volume fraction and diameter on the heat transfer and also the effect of viscous dissipation on the heat transfer performance are studied. Results show that increasing the nanoparticles volume fraction to φ = 5% causes 18% enhancement in the Nusselt number compared to the pure water. Also, increasing the nanoparticles diameter from 11 nm to 100 nm for φ = 5% results in 13.33% decrease in the Nusselt number. Finally, considering the viscous dissipation effect, reduction in the Nusselt number is observed.

Al2O3/water nano-fluid forced convective flow in a rectangular curved micro-channel: first and second law analysis, single-phase and multi-phase approach

Al2O3/water nano-fluid flow is investigated in a rectangular curved micro-channel using computational fluid dynamics and a comparative study has been conducted between single-phase and multi-phase approaches for modeling of nano-particles addition. The effects of nano-particles volume fraction and Reynolds number on pressure drop, Nusselt number and entropy generation are assessed. Results showed that, increasing nano-particles volume fraction raises Nusselt number, in addition to pressure drop enhancement. Entropy generation due to fluid friction, heat transfer and total entropy generation are also analyzed and the effects of different parameters are investigated. According to the results, nano-particles volume fraction decreases entropy generation due to heat transfer and enhances entropy generation due to fluid friction. It is also noted that nano-particles volume concentration and Reynolds number can alter the dominant source of irreversibility on total irreversibility. Furthermore, Eulerian multi-phase mixture model is compared with single-phase model in curved rectangular micro-channel.

Entropy generation analysis of MHD nanofluid flow in a porous vertical microchannel with nonlinear thermal radiation, slip flow and convective-radiative boundary conditions

The heat transfer and entropy generation in a magnetohydrodynamic flow of Al2O3–water nanofluid through a porous vertical microchannel with nonlinear radiative heat flux were investigated numerically. Then, combined effects of nanoparticle volume fraction, hydrodynamic slip, magnetic field, suction/injection and thermal radiation on heat transfer and entropy generation were studied. The dimensionless governing equations were solved numerically by applying Runge–Kutta integration method together with shooting technique. In this study, the accuracy of the numerical results was verified by comparing its predictions with exact solutions of model without both radiation effects and buoyancy force. Here, different from previous literature, heat transfer subject to nonlinear thermal radiation, Joule heating and viscous dissipation was solved and analyzed using conjugate convective-radiative heat transfer on the boundary surfaces. Moreover, influences of pertinent parameters on nanofluid velocity, temperature, local and global entropy generation and Nusselt number were discussed in detail and illustrated graphically. Based on the numerical results, it was proved that the global entropy generation decreased with both nanoparticle volume fraction and suction/injection Reynolds number while it increased with Grashof number (Buoyancy force intensity), radiation parameter and conduction-radiation parameter. In addition, it was possible to determine optimum values of slip flow with minimum values of global entropy generation rate. The Nusselt number was also calculated and explored for different conditions. In this way, optimum values of Grashof number with maximum heat transfer on the heated left plate were derived.

Thermal performance analysis of solar parabolic trough collector using nanofluid as working fluid: A CFD modelling study

In this work, forced convection heat transfer turbulent fluid flow inside the receiver tube of solar parabolic trough collector is numerically simulated. The CuO-water and Al2O3-water nanofluids are used in this study as working fluid. The Computational Fluid Dynamics (CFD) commercial code is employed to find hydrodynamic and heat transfer coefficients by means of Finite Volume Method (FVM). This analysis is carried out based on k–ε RNG turbulent model for different heat flux conditions. The effect of nanoparticles volume fraction (ϕ) on thermal performance of the solar parabolic collector is studied. Results show that nanofluid enhances the heat transfer characteristics of the parabolic trough collector in comparison with pure water. Also, the results indicate that by increasing of the nanoparticle volume fraction, the average Nusselt number increases for both nanofluids. Furthermore, the heat transfer coefficient was found to be enhanced up to 28% and 35% by using Al2O3-water and CuO-water nanofluids (ϕ=3%), respectively.

Numerical analysis of discharging process acceleration in LHTESS by immersing innovative fin configuration using finite element method

Discharging process of Latent Heat Thermal Energy Storage Systems (LHTESS) containing Phase Change Material (PCM) has been discussed in the present paper. In these systems, thermal energy storage and retrieval occur during solid-liquid phase change. They are used to establish balance between energy supply and demand, but the main restriction for these systems is the weak thermal conductivity of working fluid. In recent years, several enhancement techniques have been employed in order to overcome this problem. In the present study, the method of nanoparticles dispersion in pure PCM to make Nano-Enhanced Phase Change Material (NEPCM) and adding fins with innovative configuration are applied to accelerate solidification process. The abovementioned techniques are analyzed separately. First the geometry parameters of the fin are changed to find the best fin array. Then the effect of nanoparticles volume fraction on solidification rate is studied. The numerical approach in this paper is Standard Galerkin Finite Element Method. In this work, an innovative fin configuration, based on snowflake crystal structure, has been employed to enhance the performance of LHTESS during the discharging process, also the efficiency of nanoparticle dispersion in PCM and adding fin with different structures on LHTESS performance has been examined from the viewpoint of either discharging expedition or maximum energy storage capacity, which are proposed as the novelties here. Results indicate that enhancement of discharging process in LHTESS by applying Snowflake shaped fin structure in comparison with nanoparticle dispersion is higher significantly, although it doesn’t reduce maximum energy storage capacity considerably.

3D Buoyancy-Induced Flow and Entropy Generation of Nanofluid-Filled Open Cavities Having Adiabatic Diamond Shaped Obstacles

A three dimensional computational solution has been obtained to investigate the natural convection and entropy generation of nanofluid-filled open cavities with an adiabatic diamond shaped obstacle. In the model, the finite volume technique was used to solve the governing equations. Based on the configuration, the cavity is heated from the left vertical wall and the diamond shape was chosen as adiabatic. Effects of nanoparticle volume fraction, Rayleigh number (103 ≤ Ra ≤ 106) and width of diamond shape were studied as governing parameters. It was found that the geometry of the partition is a control parameter for heat and fluid flow inside the open enclosure.

Mixed convection squeezing three-dimensional flow in a rotating channel filled with nanofluid

Purpose – The purpose of this paper is to numerically solve the problem of an unsteady squeezing three-dimensional flow and heat transfer of a nanofluid in rotating vertical channel of stretching left plane. The fluid is assumed to be Newtonian, incompressible and electrically conducting embedded with nanoparticles. Effect of internal heat generation/ absorption is also considered in energy equation. Four different types of nanoparticles are considered, namely, copper (Cu), alumina (Al2O3), silver (Ag) and titanium oxide (TiO2) with the base fluid as water. Maxwell-Garnetts and Brinkman models are, respectively, employed to calculate the effective thermal conductivity and viscosity of the nanofluid. Design/methodology/approach – Using suitable similarity transformations, the governing partial differential equations are transformed into set of ordinary differential equations. Resultant equations have been solved numerically using Runge-Kutta-Fehlberg fourth fifth order method for different values of the governing parameters. Effects of pertinent parameters on normal, axial and tangential components of velocity and temperature distributions are presented through graphs and discussed in detail. Further, effects of nanoparticle volume fraction, squeezing parameter, suction/injection parameter and heat source/sink parameter on skin friction and local Nusselt number profiles for different nanoparticles are presented in tables and analyzed. Findings – Squeezing effect enhances the temperature field and consequently reduces the heat transfer rate. Large values of mixed convection parameter showed a significant effect on velocity components. Also, in many heat transfer applications, nanofluids are potentially useful because of their novel properties. They exhibit high-thermal conductivity compared to the base fluids. Further, squeezing and rotation effects are desirable in control the heat transfer. Originality/value – Three-dimensional mixed convection flows over in rotating vertical channel filled with nanofluid are very rare in the literature. Mixed convection squeezing three-dimensional flow in a rotating channel filled with nanofluid is first time investigated.

Numerical study of forced convection flow and heat transfer of a nanofluid flowing inside a straight circular pipe filled with a saturated porous medium

In this paper, the problem of developing forced convection flow of a nanofluid in a constant-wall-temperature circular tube filled with a porous medium is considered. The flow is steady and Brinkman-Forchheimer-extended Darcy equation model is employed. The thermal-equilibrium model is assumed between nanofluid and solid phase. It is also assumed that nanoparticles are distributed non-uniformly inside the pipe, hence the particles volume fraction equation is also coupled with the governing equations. A numerical study has been performed using the Finite-Volume method to analyze heat transfer coefficient of Al2O3 -water nanofluid. The effects of nanoparticles volume fraction and porosity on fluid flow and heat transfer of nanofluids are studied. The results show that the Nusselt number is increased with increasing particles volume fraction. Moreover, the wall shear stresses are increased. Finally, the effect of porosity on particle volume fraction distribution is studied and discussed in detail. We are confident that the reported results are new and original.

Flow and Heat Transfer in Micro Pin Fin Heat Sinks With Nano-Encapsulated Phase Change Materials

In this paper, a 3D-conjugated heat transfer model for nano-encapsulated phase change materials (NEPCMs) cooled micro pin fin heat sink (MPFHS) is presented. The governing equations of flow and heat transfer are solved using a finite volume method based on collocated grid and the results are validated with the available data reported in the literature. The effect of nanoparticles volume fraction (C = 0.1, 0.2, and 0.3), inlet velocity (Vin = 0.015, 0.030, and 0.045 m/s), and bottom wall temperature (Twall = 299.15, 303.15, 315.15, and 350.15 K) is studied on Nusselt and Euler numbers as well as temperature contours in the system. The results indicate that significant heat transfer enhancement is achieved when using the NEPCM slurry as an advanced coolant. The maximum Nusselt number when NEPCM slurry (C = 0.3) with Vin = 0.015, 0.030, and 0.045 (m/s) is employed is 2.27, 1.81, and 1.56 times higher than the ones with base fluid, respectively. However, with increasing bottom wall temperature, the Nusselt number first increases then decreases. The former is due to higher heat transfer capability of coolant at temperatures over the melting range of phase change material (PCM) particles due to partial melting of nanoparticles in this range. However, the latter phenomenon is due to the lower capability of the NEPCM particles and consequently coolant in absorbing heat at coolant temperatures is higher than the temperature correspond to fully melted NEPCM. It was observed that the NEPCM slurry has a drastic effect on the Euler number, and with increasing volume fraction and decreasing inlet velocity, the Euler number increases accordingly.

Numerical investigation of flow and thermal pattern in unbounded flow using nanofluid - Case study: Laminar 2-D plane jet

In this article, a numerical study is carried out to analyze the effect of nanoparticle volume fraction over flow and thermal characteristics of laminar 2-D plane jet. Al2O3-water and TiO2-water nanofluids are considered in this investigation with lowest and highest values of particle volume concentration equals to 0 and 0.02 respectively. This paper propose four correlations for describing the relation between the solid volume fraction, ?t and ?u. The results show that the cross stream thermal diffusion depth and cross stream hydraulic diffusion depth are increased when particles volume concentration is increased and mean temperature and mean velocity decreases when the solid volume fraction is increased. The effects of nanoparticle volume fraction in velocity and temperature time histories are also studied and discussed.

Numerical investigation of flow and thermal pattern in unbounded flow using nanofluid - Case study: Laminar 2-D plane jet

In this article, a numerical study is carried out to analyze the effect of nanoparticle volume fraction over flow and thermal characteristics of laminar 2-D plane jet. Al2O3-water and TiO2-water nanofluids are considered in this investigation with lowest and highest values of particle volume concentration equals to 0 and 0.02 respectively. This paper propose four correlations for describing the relation between the solid volume fraction, δt and δu. The results show that the cross stream thermal diffusion depth and cross stream hydraulic diffusion depth are increased when particles volume concentration is increased and mean temperature and mean velocity decreases when the solid volume fraction is increased. The effects of nanoparticle volume fraction in velocity and temperature time histories are also studied and discussed.

Statistical Analysis of the Effect of Nanoparticles Volume Fraction on Turbulent Forced Convective Heat Transfer Coefficient of Nanofluid in a Circular Tube

In this paper, the statistical analysis of the effect of nanoparticles volume fraction on one of the most important thermal characteristics turbulent flow of nanofluid i.e. convection heat transfer coefficient, inside a circular tube with uniform wall heat flux is investigated numerically. Also, water as a base fluid and Al2O3 as suspended particles with a diameter of 36 nm are considered. Heat transfer characteristics are computed using the solution of elliptic equations based on discrete the finite volume method and the second order upwind. The relationship between pressure and velocity using SIMPLEC algorithm is established. In this study, the variation of volume fraction of nanoparticles is assumed in the range of 0 to 6%. The best probability distribution function of the heat transfer parameters are selected using chi square test that various probability distribution such as: Gamma, Normal, Lognormal, Gumbel, and Frechet are evaluated based on numerical analysis of tube flow. After reviewing the results, it was found that with increasing volume fraction of nanoparticles, the convective heat transfer coefficient increases. On the other hand, the convective heat transfer coefficients with regard to variation of volume fraction of nanoparticles follow Gumbel Max probability distribution function.

Lattice Boltzmann simulation of nanofluid heat transfer enhancement and entropy generation

In the framework of this paper, nanofluid flow and heat transfer in a square enclosure containing a rectangular heated body is investigated computationally. The fluid in the cavity is a water-based nanofluid containing four different types of metal and metal-oxide nanoparticles: alumina (Al2O3), copper (Cu), silver (Ag) and titania (TiO2). The effective viscosity and thermal conductivity of the nanofluid are calculated by the Brinkman model and Maxwell–Garnett (MG), respectively. The Lattice Boltzmann Method (LBM) has been adopted to solve this problem. The effects of various governing parameters such as nanofluid type, Rayleigh number, volume fraction of nanoparticles and height of the rectangular heated body contained in the cavity on hydrothermal characteristics are studied. The results indicate that both the Nusselt number and dimensionless entropy generation are increasing functions of the Rayleigh number and nanoparticle volume fraction of the nanofluid. Furthermore, the effect of nanoparticle volume fraction is found to be more pronounced for a low Rayleigh number as compared to a high Rayleigh number. Excellent accuracy is achieved with the LBM code.

Numerical study on performance enhancement of solid–solid phase change materials by using multi-nanoparticles mixtures

Innovative methods for enhancing storage performance of phase change materials (PCMs) have become the main concern of many scientists. In this numerical study, heat transfer characteristics and thermal storage performance of enhanced neopentyl-glycol (NPG) in a cylindrical container are investigated. Enhancement of phase change material has been done by using a mixture of multi-nanoparticles (Cu, Al, TiO2 and SiO2). Binary and triple mixtures of nanoparticles have been employed to assess the improvement in storage capacity of phase change material. The effect of nanoparticles volume fraction on the thermal behavior of NPG composites has been presented and discussed. It has been found that NPG composite containing (6% SiO2+6% Al) is more effective in heat storage than the composition containing (6% Al+6% Cu). Also, the best performance in heat storage is achieved by the composition (6% Al+3% SiO2+3% TiO2), within the NPG, compared to the other compositions.

Numerical analysis of convective heat transfer of nanofluids in circular ducts with two-phase mixture model approach

Computational fluid dynamics simulations for initially hydro-dynamically fully developed laminar flow with nanofluids in a circular duct under constant wall temperature condition are performed with two-phase mixture model by using Fluent software. Thermal behaviors of the system are investigated for constant wall temperature condition for Al2O3/water nanofluid. Hamilton–Crosser model and the Brownian motion effect are used for the thermal conductivity model of nanofluid instead of the Fluent default model for mixtures which gives extraordinary high thermal conductivity values and is valid for macro systems. Also, thermal conductivity and viscosity of the base fluid are taken as temperature dependent. The effects of nanoparticle volume fraction, nanoparticle size, and inlet Peclet number on the heat transfer enhancement are investigated. The results are compared with single-phase results which give slightly lower heat transfer coefficient values than the results of two-phase mixture model.

Energy Harvesting Through Optical Properties of TiO2 and C- TiO2 Nanofluid for Direct Absorption Solar Collectors

Nanofluids are tailored suspensions of nanoparticles in a suitable base fluid. The discovery of nanofluids by Stephen choi opened a new heat transfer mechanism. Since then several research has taken place to explore thermal, electrical and magnetic property of nanofluids. Nanofluids showed enhanced electrical and thermal conductivities. The nanofluids are also proved as a potential candidate for direct absorption solar collectors (DASC). The present work investigates the effect of nanoparticle volume fraction and the associated optical intensity attenuation with a semiconductor laser diode of wavelength 670 nm. Nanoparticles of Titanium dioxide (TiO 2 ) and Carbon doped Titanium dioxide (C-TiO 2 ) are prepared by sol gel and characterized by powder XRD, SEM and UV. Since carbon is a good absorption material, TiO 2 are doped with carbon (C-TiO 2 ) to increase the absorption of incident radiation. Nanoparticles of TiO 2 and C-TiO 2 with two weight fractions such as 0.04 and 0.08 are dispersed in water and ethylene glycol to obtain TiO 2 and C-TiO 2 nanofluids. The nanofluids are investigated for their sedimentation time. Stability of TiO 2 nanofluid is nine times more than C-TiO 2 nanofluid but C-TiO 2 nanofluid are found to be efficient absorbers than TiO 2 nanofluid. A low volume fraction of C-TiO 2 nanofluid can ensure high stability, low pumping power and good absorption for a DASC. Keywords- : Nanofluid, TiO 2 C-TiO 2, optical absorption, Laser.DASC 1. Introduction Increasing consumption and growing demands of electrical appliances across the globe have posed a threat on the non renewable energy resources and has made us exploit the maximum of renewable energy resources, in which solar energy is the ultimate choice. Solar energy has been investigated for photovoltaic and thermal applications (Duffie, 1980) [1]. A major thrust in materials development is to identify new materials in order to increase the efficiency of solar cells. Materials with ultra fine grain size and nanomaterials have provided an opportunity to tune the band gap and absorption of the existing solar energy. Conventional solar cells transfer the heat from the flat plate to the working fluid and it suffers from the large heat loss. The concept of direct absorption solar collectors in which working fluid acts as absorber and carrier of heat started replacing the conventional solar cells (Otanicar TP,2009) [2]. Since thermal conductivity of pure liquids are extremely less than solid particles, suspension of microparticles gained prominence. But micro-colloidal suspensions has drawbacks like abrasion and sedimentation. Nanofluids were substituted by Robert Taylor (2009) to overcome the above problems [3].The term Nanofluid was coined by Stephen Choi in 1995.[4] Nanofluids are suspensions of nanosized solid particles (1-100nm) in suitable base fluids. Since 1995, nanofluids have been explored as a heat transfer fluid and the best results have been reported by Eastman and Stephen Choi in ( 2001). In the past five years nanofluids have been also explored for their electrical (Suvankar Ganguly 2009)[5] and magnetic properties( John Philip,2009).[6] Nanofluids can be prepared by two ways, single step method (H Zhu 2004 )[7] or two step method (Eastman 1997) [8]. Single step method is based on simultaneous synthesis of nanoparticle and nanofluid and two step methods involve; the synthesis of nanoparticles in the first step followed by dispersion in a suitable base fluid in the second step. The success of nanofluid for DASC depends on suitable choice of base fluid and nanoparticles. The best nanofluids have high stability, high absorption of sun light and minimum abrasion. In the present work an attempt has been made to identify the best absorption nanofluid.