Heat Transfer Of Water-based Nanofluids Research Articles

MHD Flow and Heat Transfer of Water-Based Nanofluid Passing a Permeable Exponentially Shrinking Sheet with Thermal Radiation

The key objective of the present study is to elaborate the concept of boundary layer flow and heat transfer of magnetohydrodynamics namely Cu-water nanofluid flow towards an exponentially shrinking sheet with aid of mathematical modeling and computation. The present mathematical model is investigated under the influence of thermal radiation and suction. Using exponential form of similarity variables, the system of partial differential equations (PDEs) are converted in to a set of ordinary differential equations (ODEs). The resulting nonlinear ODEs are computationally solved by using a two-point boundary value problem numerical technique, which constitutes with common finite difference method. The influence of physical parameters such as magnetic field parameter, Eckert number, suction parameter, radiation parameter are described in details with the help of graphical demonstration of velocity and temperature distributions, coefficient of skin fiction and rate of heat transfer. Computational results reveal that after suspension of nanoparticles into base fluid as water fluid temperature raised significantly compare to that of pure fluid. It is also observed that for rising values of magnetic field parameter, thermal radiation, particles volume fraction fluid temperature distribution significantly improved; whereas opposite phenomena is true for suction parameter and Prandtl number. The rate of heat transfer accelerated with Eckert number, Prandtl number, while coefficient of skin friction boost with thermal radiation parameter. For verifying purposes, a comparison has been shown between present results and the computational results of previous studies and found a very close agreement.

Multiple solutions for nanofluids flow and heat transfer in porous medium with velocity slip and temperature jump

Fluid flow and heat transfer of water-based nanofluids over a stretching/shrinking permeable sheet with porous environment under velocity slip and temperature jump conditions is investigated. The flow phenomenon is instigated by a two-dimensional boundary layer flow. On exercising suitable similarity variables, the resulting physical system of nonlinear partial differential equations is transformed into a set of ordinary differential equations. The existence and nonexistence of multiple exact solutions in both the stretching and shrinking problems for various parameters domains is shown. The prominency of stretching or shrinking and velocity slip parameters in shaping the flow behavior and resulting in special exact solutions are reported under various parametric values. The shrinking surface flow exhibit different behavior than the stretching case problem and produces physically meaningful dual solutions. The solutions for the flow and temperature equations are obtained in the form of Kummers function, exponential integral and Eulers gamma function. Morover, results are shown for velocity and temperature profiles for inclusive graphical illustration that includes the influence of velocity slip parameter, temperature jump, permeability and Prandtl number. Moreover, the critical values and plotting curves for obtaining single or dual solution are successfully presented.

Numerical duality of MHD stagnation point flow and heat transfer of nanofluid past a shrinking/stretching sheet: Metaheuristic approach

In the present era of Industry 4.0, automation, and nanotechnology, many industrial applications require the simultaneous control of heat and fluid flow for better efficiency of machines. The polymeric excursion process, manufacturing of plastic films, glass, metallic equipment, all need control over friction forces and heat flow rates. Considering the importance of the subject, the present study deals with the stagnation point flow and heat transfer of water-based nanofluid over a stretching/shrinking sheet with a non-aligned axis of symmetry. The permeable sheet is considered in the presence of a uniform magnetic field. The non-linear partial differential equations governing the flow and heat transfer are converted into non-linear coupled ordinary differential equations using similarity transformations. The resultant equations are solved using “Particle Swarm Optimization” and Runge-Kutta method based hybrid shooting technique. Considering the nanoparticle size, concentration and shape-dependence on physical and thermal properties of nanofluid more realistic aggregation based mathematical models are used for both viscosity and thermal conductivity. Numerical results for the velocity profile, non-alignment function, temperature distribution and local skin friction are discussed with respect to the physical parameters like nanoparticle concentration, nanoparticle size, magnetic field, suction, and stretching/shrinking velocity. The existence of dual solutions are observed for the shrinking velocity parameter λ<−1, and the practically realizable and stable solutions are filtered out by computing the eigenvalues for the formulated perturbed Eigen problem. The results for the stable solutions unveiled that, by changing the stretching velocity parameter λ from 0 to 0.5, there is approximately 38% enhancement in heat transfer rate and 42% decrement in skin friction coefficient. Moreover, in the case of shrinking velocity parameter λ=−1.25, with an increase in nanoparticle concentration from 0 to 5%, the skin friction coefficient reduces by 53%, whereas the change in nanoparticle size from 10 nm to 50 nm has a skin friction reduction of only 10%.

Water-based ferrofluid flow and heat transfer over a stretchable rotating disk under the influence of an alternating magnetic field

Flow and heat transfer of water-based nanofluid over a stretchable rotating disk under the influence of an alternating magnetic field is investigated. The external magnetic field creates a hindrance in the flow and depends on the frequency of the alternating magnetic field. The frequency of an alternating magnetic field can increase or decrease the viscosity of the magnetic fluid in the flow. A set of nonlinear differential equations in the present theoretical model is solved numerically using the finite element method. Volume concentration, frequency of the alternating magnetic field, magnetic polarization force, and Prandtl number play an important role in the velocity and temperature distributions of iron/water nanofluid. A comparative study for velocity and heat transfer is presented for iron/water, nickel/water, and cobalt/water ferromagnetic nanofluid. The rotational viscosity enhances the heat transfer in nanofluid provided the magnetic field should be stationary.

An experimental investigation on natural convection of non-covalently functionalized MWCNTs nanofluids: Effects of aspect ratio and inclination angle

Abstract An experimental analysis was conducted to study natural convection heat transfer of water-based nanofluids. Two enclosures with the length × width × height(cm) dimensions of 10 × 10 × 10 and 20 × 10 × 10 and the inclination slopes of 0, 45 and 90° were considered. One of the walls was cooled and the opposite wall was heated. Multi-walled carbon nanotube (MWCNT)/water nanofluids were used as the heat transfer fluid while the MWCNTs were non-covalently functionalized by gum Arabic (GA). The MWCNT-GA/water nanofluids were prepared using 0.005, 0.05 and 0.1 wt% nanoparticles. According to the results, adding MWCNTs to water reduced free convection heat transfer in both enclosures. The effect of increasing MWCNT concentration on Nusselt number was found to be greater than the impact of changing Rayleigh number. Furthermore, free convection heat transfer increased with reducing inclination angle from 90° to 0° at high Rayleigh numbers. It was noticed that changing inclination angle has no considerable influence on Nusselt number at lower Rayleigh numbers. Moreover, free convection heat transfer increased about 8.77% with increasing the aspect ratio from 1 to 2. The highest reduction of Nusselt number was attributed to a system with the aspect ratio, concentration and inclination angle of 1, 0.1 wt% and 90°, respectively.

Experimental study on turbulent convective heat transfer of water-based nanofluids containing alumina, copper oxides and silicon carbide nanoparticles

Nanofluids are obtained by suspending metallic or non-metallic nanoparticles in conventional base liquids and can be employed to increase heat transfer rate in various applications. In this study, the effects of adding three types of nanofluids on turbulent convective heat transfer at the entrance region of a constant wall heat flux tube were experimentally studied. The nanofluids were mixtures of aluminium oxide, copper oxide, and silicon carbide at various nanoparticle volume fractions ranging from 0.0002 to 0.002 in water. The convective heat transfer coefficient was measured at different Reynolds numbers of 10,000–50,000. At these concentrations and Reynolds numbers, a maximum of 11–18% of convection heat transfer coefficient was observed as compared to the base fluid, showing a 6–9% increase on average. In this study, it was observed that changes in the nanoparticle type had no considerable effect on heat transfer coefficient increase. According to the model proposed here, the dimensionless thickness of laminar sub-layer is specified as a functional equation of the volume fraction of nanoparticles for each material.

Couple Stress Effects on Three Dimensional Flow of Magnetite–Water Based Nanofluid Over an Extended Surface in Presence of Non-linear Thermal Radiation

The present study discloses the three dimensional flow and heat transfer of water-based nanofluid tempted by an extendable surface subject to the effects of couple stress and thermal radiation. Fe $$_{3}$$ O $$_{4}$$ nanoparticles in water-based couple stress nanofluid are considered. The consequence of nonlinear thermal radiation is sought. Using appropriate similarity transformations, governing partial differential equations are reduced to ordinary differential equations and these equations are solved numerically by means of shooting technique with the assistance of Runge–Kutta method. Effects of controlling parameters on velocity, temperature, local skin friction coefficient and local Nusselt number are discussed in detail. It is observed that fluid velocities decrease due to increase in couple stress parameter and also with the rise in nanoparticle volume fraction. Thickness of thermal boundary layer increases with the rise in couple stress parameter.

MHD Nanofluid Bioconvection over an Exponentially Stretching Sheet in the Presence of Gyrotactic Microorganisms and Thermal Radiation

In this paper, we have analyzed the effects of thermal radiation on heat transfer of water-based nanofluid containing motile gyrotactic microorganisms over an exponentially stretching sheet. The nanofluid bioconvection is due to the combined effects of magnetic field and buoyancy force on the interaction of motile gyrotactic microorganisms and nanoparticles in the base fluid. In order to stabilize the nanoparticles to suspend, microorganisms are imposed into the nanofluid. The governing partial differential equations are converted into a system of nonlinear ordinary differential equations by the use of similarity transformations which are then solved numerically using fifth order Runge-Kutta-Fehlberg integration scheme with shooting technique. Present results are compared with the previously published results in some limiting cases and the results are found to be in an excellent agreement. The effects of various thermophysical parameters and bioconvection parameters on nanofluid velocity, temperature, nanoparticles concentration, density of motile microorganisms, as well as on the local skin friction coefficient, local Nusselt number, and local Sherwood number are described in detail. It is found that the Lewis number tends to decelerate the concentration distributions of motile microorganisms in the presence of the magnetic field and thermal radiation. Also, it is observed that the effects of increase in the buoyancy ratio parameter and bioconvection Rayleigh number are to increase the nanoparticle concentration and the density of motile microorganisms.

Numerical Study on the Pool Boiling Heat Transfer of Water-Based Nanofluids on a Vertical Surface

Numerical Study on the Pool Boiling Heat Transfer of Water-Based Nanofluids on a Vertical Surface

Heat transfer analysis in natural convection flow of nanofluid past a wavy cone

The problem of natural convective heat transfer of water-based nanofluid along wavy cone surface is investigated numerically. Analysis is performed to study the heat transfer augmentation due to five types of nanoparticles, namely, alumina (Al2O3), copper (Cu), silver (Ag), copper oxide (CuO) and titania (TiO2). The flow has been assumed to be steady and fluid properties have been supposed constant except for the density depending upon temperature giving rise to the buoyancy force. Famous Tiwari and Das model of nanofluid has been utilized in this study. The effects of cone half angle γ and amplitude of the waviness α on the Nusselt number (Nu) and skin friction (Cf) are studied. A comparison is made with the case of pure fluid flow past wavy cone at different values of α. It has been observed that the TiO2-nanoparticle shown to have the maximum cooling performance and Cu-nanoparticle appeared to have maximum heating performance for this study. The results shown in this research arrange for a significant source of reference for taming the natural convection heat transfer enactment along wavy cone. Present results for selected variables are matched with the already published work for pure fluid and are shown to be in good agreement.

Numerical investigation of magnetohydrodynamic flow and heat transfer of copper–water nanofluid in a channel with non-parallel walls considering different shapes of nanoparticles

This article presents the magnetohydrodynamic flow and heat transfer of water-based nanofluid in divergent and convergent channels. Equations governing the flow are transformed to a set of ordinary differential equations by employing suitable similarity transforms. Resulting system is solved using a strong numerical procedure called Runge–Kutta–Fehlberg method. Results are compared with existing solutions available in the literature and an excellent agreement is seen. Three shapes of nanoparticles, namely, platelet-, cylinder-, and brick-shaped particles, are considered to perform the analysis. Influence of emerging parameters such as channel opening, Reynolds number, magnetic parameter, Eckert number, and the nanoparticle volume fraction are heighted with the help of graphs coupled with comprehensive discussions. The magnetic field can be used as a controlling parameter to reduce the backflow regions for the divergent channel case. Temperature of the fluid can be controlled with the help of strong magnetic field. It is also observed that platelet-shaped particles have higher temperature values as compared to cylinder- and brick-shaped particles.

A study on Brinkman number variation on water based nanofluid heat transfer in partially heated tubes

Even if the variation of Nusselt number with Reynolds number has been observed before, little to no studies are concerning nanofluids. The present numerical data in the laminar regime were also found to correlate well with the Brinkman number for the individual sets and much better globally, by combining all the data sets for nanofluids and water.Thus, this work proposes a new correlation between heat transfer rate and Brinkman number which is a nondimensional number of viscosity, flow velocity and temperature. The results showed a good empirical equation that Nu/(Re0.62Pr0.33) is dependent on a power law function to the Brinkman number in laminar flow regime. The proposed correlation can be applied both to water and nanofluid flow, with respect to the nanoparticle loading. It is expected that the equation suggested by this work can be useful to design heating/cooling devices.

Unsteady flow of variable viscosity Cu-water and Al2O3-water nanofluids in a porous pipe with buoyancy force

Purpose – The purpose of this paper is to investigate the combined effects of buoyancy force and variable viscosity on unsteady flow and heat transfer of water-based nanofluid containing copper and alumina as nanoparticles through a porous pipe. Design/methodology/approach – Using the Boussinesq and boundary-layer approximations with Buongiorno nanofluid model. The governing nonlinear partial differential equations for the continuity, momentum and energy balance are formulated. The equations obtained are solved numerically using a semi-discretization finite difference method (know) as method of line coupled with Runge-Kutta-Fehlberg integration scheme. Findings – Numerical results for the skin-friction, heat transfer and for the velocity and temperature profiles are obtained. The results show that with suction, Cu-water produces higher skin friction and heat transfer rate than Al2O3-water. Both nanofluids velocity and temperature increase with a decrease in viscosity and an increase in buoyancy force intensity. Practical implications – Buoyancy-driven flow and heat transfer in porous geometries has many significant applications in industrial and engineering such as, electrical and microelectronic equipments, solar-collectors, geothermal engineering, petroleum reservoirs, thermal buildings insulation. This work provides very important information for researchers on this subject. Originality/value – This paper illustrates the effects of buoyancy force and temperature dependent on heat transfer and fluid flow problem using Cu-water and Al2O3-water nanofluids in a porous pipe.

Heat transfer analysis of unsteady graphene oxide nanofluid flow using a fuzzy identifier evolved by genetically encoded mutable smart bee algorithm

In the current research, the unsteady two dimensional Graphene Oxide water based nanofluid heat transfer between two moving parallel plates is analyzed using an intelligent black-box identifier. The developed intelligent tool is known as evolvable evolutionary fuzzy inference system (EE-FIS) which is based on the integration of low-level fuzzy programming and hyper-level evolutionary computing concepts. Here, the authors propose the use of a modified evolutionary algorithm (EA) which is called hybrid genetic mutable smart bee algorithm (HGMSBA). The proposed HGMSBA is used to evolve both antecedent and consequent parts of fuzzy rule base. Besides, it tries to prune the rule base of fuzzy inference system (FIS) to decrease its computational complexity and increase its interpretability. By considering the prediction error of the fuzzy identifier as the objective function of HGMSBA, an automatic soft interpolation machine is developed which can intuitively increase the robustness and accuracy of the final model. Here, HGMSBA-FIS is used to provide a nonlinear map between inputs, i.e. nanoparticles solid volume fraction (ϕ), Eckert number (Ec) and a moving parameter which describes the movements of plates (S), and output, i.e. Nusselt number (Nu). Prior to proceeding with the modeling process, a comprehensive numerical comparative study is performed to investigate the potentials of the proposed model for nonlinear system identification. After demonstrating the efficacy of HGMSBA for training the FIS, the system is applied to the considered problem. Based on the obtained results, it can be inferred that the developed HGMSBA-FIS black-box identifier can be used as a very authentic tool with respect to accuracy and robustness. Besides, as the proposed black-box is not a physics-based identifier, it frees experts from the cumbersome mathematical formulations, and can be used for advanced real-time applications such as model-based control. The simulations indicate that the gradient of Nu has a direct nonlinear relation with the values of ϕ and Ec. It is also observed that an increase in the value of S decreases the value of Nu.

Numerical study of transient buoyancy-driven convective heat transfer of water-based nanofluids in a bottom-heated isosceles triangular enclosure

A numerical study of transient buoyancy-driven convective heat transfer of water-based nanofluids inside a bottom-heated horizontal isosceles triangular cylinder is presented. Nano-sized copper oxide (CuO) particles suspended in water with two different volume fractions are considered. The thermophysical properties of water in the presence of nanoparticles are predicted using existing models, in which the effects of the Brownian motion of nanoparticles are taken into account. It is shown that pitchfork bifurcation appears for relatively high Grashof numbers and the critical Grashof number is found to be 5.60 × 10 4. The predicted development of convective flow of nanofluids is presented by means of the average Nusselt number over the bottom. Additionally, the flow development time towards a steady/quasi-steady state and the time-averaged Nusselt number are scaled with Grashof number. It is also shown that at constant Grashof numbers the time-averaged Nusselt number is lowered as more nanoparticles are added to the base liquid and will be overestimated if the Brownian motion effects are not considered.

Buoyancy Driven Heat Transfer of Nanofluids in a Tilted Enclosure

Buoyancy driven heat transfer of water-based nanofluids in a differentially heated, tilted enclosure is investigated in this study. The governing equations (obtained with the Boussinesq approximation) are solved using the polynomial differential quadrature method for an inclination angle ranging from 0 deg to 90 deg, two different ratios of the nanolayer thickness to the original particle radius (0.02 and 0.1), a solid volume fraction ranging from 0% to 20%, and a Rayleigh number varying from 104 to 106. Five types of nanoparticles, Cu, Ag, CuO, Al2O3, and TiO2 are taken into consideration. The results show that the average heat transfer rate from highest to lowest is for Ag, Cu, CuO, Al2O3, and TiO2. The results also show that for the particle radius generally used in practice (β=0.1 or β=0.02), the average heat transfer rate increases to 44% for Ra=104, to 53% for Ra=105, and to 54% for Ra=106 if the special case of θ=90 deg, which also produces the minimum heat transfer rates, is not taken into consideration. As for θ=90 deg, the heat transfer enhancement reaches 21% for Ra=104, 44% for Ra=105, and 138% for Ra=106. The average heat transfer rate shows an increasing trend with an increasing inclination angle, and a peak value is detected. Beyond the peak point, the foregoing trend reverses and the average heat transfer rate decreases with a further increase in the inclination angle. Maximum heat transfer takes place at θ=45 deg for Ra=104 and at θ=30 deg for Ra=105 and 106.

Natural convection of water-based nanofluids in an inclined enclosure with a heat source

This study investigates natural convection heat transfer of water-based nanofluids in an inclined square enclosure where the left vertical side is heated with a constant heat flux, the right side is cooled, and the other sides are kept adiabatic. The governing equations are solved using polynomial differential quadrature (PDQ) method. Calculations were performed for inclination angles from 0° to 90°, solid volume fractions ranging from 0% to 20%, constant heat flux heaters of lengths 0.25, 0.50 and 1.0, and a Rayleigh number varying from 10 4 to 10 6. The ratio of the nanolayer thickness to the original particle radius is kept at a constant value of 0.1. The heat source is placed at the center of the left wall. Five types of nanoparticles are taken into consideration: Cu, Ag, CuO, Al 2O 3, and TiO 2. The results show that the average heat transfer rate increases significantly as particle volume fraction and Rayleigh number increase. The results also show that the length of the heater is also an important parameter affecting the flow and temperature fields. The average heat transfer decreases with an increase in the length of the heater. As the heater length is increased, the average heat transfer rate starts to decrease for a smaller inclination angle (it starts to decrease with inclination at 90° for ɛ = 0.25, 60° for ɛ = 0.50, 45° for ɛ = 1.0, respectively).