Peristaltic activity of thermally radiative magneto-nanofluid with electroosmosis and entropy analysis

The importance of gold and silver nanoparticles in the blood flow has immense applications in biomedicine for the treatment of cancer disease and wound treatment due to their large atomic number and antimicrobial property. The current study deals with the magnetohydrodynamic and electroosmotic radiative peristaltic Jeffrey nanofluid (blood–silver/gold) flow with the effect of slip and convective boundary conditions in the nonsymmetric vertical channel. The nondimensional governing equations have been solved analytically and the exact solutions have been presented for velocity, temperature, shear stress, trapping, entropy generation, pressure gradient and heat transfer coefficient. The pictorial representations have been prepared for the flow quantities with respect to fluid flow parameters of interest. It is noticed from the current study that the gold-based nanofluids exhibit higher velocity than silver-based nanofluids. Enhancement of thermal radiation decreases the total entropy generation. The size of the tapered bolus decreases with the enhancement of magnetic field strength. The present model is applicable in designing pharmacodynamic pumps and drug delivery systems.     

Entropy generation analysis of nanofluid flow in a circular tube subjected to constant wall temperature

Due to their improved thermal conductivity, nanofluids have the potential to be used as heat transfer fluids in thermal systems. However adding particles into nanofluids will increase the viscosity of the fluid flow. This demonstrates that there is a trade-off between heat transfer enhancement and viscosity. It might not be ideal to achieve a heat transfer enhancement along with a relatively high pumping power. This study presents an analytical investigation on the entropy generation of a nanofluid flow through a circular tube with a constant wall temperature. Nanofluid thermo-physical properties are obtained from literature or calculated from suitable correlations. The present study focuses on water based alumina and titanium dioxide nanofluids. Outcome of the analysis shows that titanium dioxide nanofluids offer lower total dimensionless entropy generation compared to that of alumina nanofluids. Addition of 4% titanium dioxide nanoparticles reduces the total dimensionless entropy generation by 9.7% as compared to only 6.4% reduction observed when using alumina. It is also noted that dimension configurations of the circular tube play a significant role in determining the entropy generation.     

Irreversibility analysis of nanofluid flow induced by peristaltic waves in the presence of concentration-dependent viscosity

The present study employs irreversibility analysis for the peristaltic movement of a nanofluid. The viscosity of the nanofluid is assumed to vary with the local concentration of colloidal particles. Impacts of thermophoresis, magnetic field, Brownian motion, Ohmic heating, viscous dissipation, and buoyant forces are considered in the flow analysis. Equations representing the flow and heat/mass transfer are prepared by employing Buongiorno's model for nanofluids. The lubrication approach is used to simplify the governing equations. The resulting system of differential equations is numerically solved with the aid of NDSolve in Mathematica. Results for entropy generation, Bejan number, velocity, temperature, and concentration are graphically presented. Outcomes show that entropy generation and temperature reduce by increasing the values of viscosity parameter. By increasing buoyancy forces due to temperature difference, the entropy generation increases, whereas the concentration profile shows a decreasing behavior. Maximum velocity reduces with an increment in the Hartman number.     

Irreversibility scrutinization on EMHD Darcy–Forchheimer slip flow of Carreau hybrid nanofluid through a stretchable surface in porous medium with temperature-variant properties

The significance of hybrid nanofluids in controlling heat transmission cannot be overemphasized. Therefore, this article scrutinizes the electromagnetized flow of Carreau hybrid nanofluid towards a stretching surface in a Darcy–Forchheimer porous medium with the occurrence of slip conditions. To form the hybrid nanofluid, the amalgamation of silver and alumina nanoparticles (NPs) embedded in water as conventional fluid is assumed. For accurate interception of the rate of heat and mass transport, thermal conductivity and mass diffusion conductance are presumed to be temperature variants. The modeling system of partial differential equations has been translated into a nondimensional form by means of suitable similarity conversions. Then, the subsequent system of ordinary differential equations is handled using overlapping domain decomposition spectral local linearization method to acquire numerical solutions. The choice of the method has been justified through the provision of errors, condition numbers, and computation time. The behavior of distinct fluid parameters on the flow features, quantities of engineering curiosity, and entropy is analyzed. Findings of paramount importance constitute that the superior thermal conductivity, heat transfer efficiency, and low production cost can be achieved through the hybridization of silver and alumina NPs. The role of thermal radiation and temperature-variant thermal conductivity is to enhance the thermal transport performance of Carreau hybrid nanofluids. The velocity, energy, and mass profiles grow with the utilization of injection effects. The principal aspiration of the second law of thermodynamics (minimizing the rate of entropy generation) can be achieved by considering shear-thinning Carreau fluid while reducing the porosity parameter and Brinkman number in the existence of velocity slip conditions in the flow system. Outcomes of the current flow model can play a significant role in biomedical, technological, and various manufacturing processes. The approximation of entropy contributes towards power engineering and aeronautical propulsion to anticipate the smartness of the overall system.     

Heat transfer and entropy generation for laminar forced convection flow of graphene nanoplatelets nanofluids in a horizontal tube

The results are reported of an investigation of the heat transfer characteristics and entropy generation for a graphene nanoplatelets (GNP) nanofluid with specific surface area of 750 m²/g under laminar forced convection conditions inside a circular stainless steel tube subjected to constant wall heat flux. The analysis considers constant velocity flow and a concentration range from 0.025 wt.% to 0.1 wt.%. The impact of the dispersed nanoparticles concentration on thermal properties, convective heat transfer coefficient, thermal performance factor and entropy generation is investigated. An enhancement in thermal conductivity for GNP of between 12% and 28% is observed relative to the case without nanoparticles. The convective heat transfer coefficient for the GNP nanofluid is found to be up to 15% higher than for the base fluid. The heat transfer rate and thermal performance for 0.1 wt.% of GNP nanofluid is found to increase by a factor of up to 1.15. For constant velocity flow, frictional entropy generation increases and thermal entropy generation decreases with increasing nanoparticle concentration. But, the total entropy generation tends to decrease when nanoparticles are added at constant velocity and to decrease when velocity rises. Finally, it is demonstrated that a GNP nanofluid with a concentration between 0.075 wt.% and 0.1 wt.% is more energy efficient than for other concentrations. It appears that GNP nanofluids can function as working fluids in heat transfer applications and provide good alternatives to conventional working fluids in the thermal fluid systems.     

Irreversibility analysis of micropolar nanofluid flow in a vertical channel with the impact of inclined magnetic field and heat source or sink

This article examines the inclined magnetic field effect on the flow of micropolar nanofluids in a vertical channel with convective boundary conditions and heat source or sink. Thermodynamics second law is employed to analyze the aspects of entropy generation. The governing differential equations are modified into dimensionless form by using suitable nondimensional variables. These transformed equations are solved by implementing the differential transform technique. The results are analyzed graphically. Skin friction and Nusselt number values are evaluated at the boundary walls of the channel. The major findings of the study are material parameter enhances the microrotation but suppresses both velocity and temperature. Magnetic parameter and angle of the implication of magnetic field decrease the velocity and microrotation. Material parameter and angle of imposed magnetic field minimize the entropy generation.     

Numerical analysis of entropy generation in mixed convection flow with viscous dissipation effects in vertical channel

A numerical investigation is performed into the entropy generated within a mixed convection flow with viscous dissipation effects in a parallel-plate vertical channel. In performing the analysis, it is assumed that the flow within the channel is steady, laminar and fully developed. The governing equations for the velocity and temperature fields in the channel are solved using the differential transformation method. The numerical results for the velocity and temperature fields are found to be in good agreement with the analytical solutions. The entropy generation number (N_s), irreversibility distribution ratio (Φ) and Bejan number (B_e) of the mixed convection flow are obtained by solving the entropy generation equation using the corresponding velocity and temperature data.     

Second law analysis in a three dimensional lid-driven cavity

Three dimensional analyses of laminar mixed convection and entropy generation in a cubic lid-driven cavity have been performed numerically. Left side of cavity moves in + y (Case I) or −y (Case II) direction. The cavity is heated from left side and cooled from right while other surfaces are adiabatic. Richardson number is the main parameter which changes from 0.01 to 100. Prandtl number is fixed at Pr = 0.71. Results are presented by isotherms, local and mean Nusselt number, entropy generation due to heat transfer and fluid friction, velocity vectors and Bejan number. Total entropy generation contours are also presented. It is found that direction of lid is an effective parameter on both entropy generation and heat and fluid flow for low values of Richardson number but it becomes insignificant at high Richardson number.     

Entropy Generation of Natural Convection Heat Transfer in a Square Cavity Using Al2O3–Water Nanofluid

Entropy generation of an Al₂O₃–water nanofluid due to heat transfer and fluid friction irreversibility has been investigated in a square cavity subject to different side‐wall temperatures using a nanofluid for natural convection flow. This study has been carried out for the pertinent parameters in the following ranges: Rayleigh number between 10⁴ and 10⁷ and volume fraction between 0 and 0.05. Based on the obtained dimensionless velocity and temperature values, the distributions of local entropy generation, average entropy generation, and average Bejan number are determined. The results are compared for a pure fluid and a nanofluid. It is totally found that the heat transfer, and entropy generation of the nanofluid is more than the pure fluid and minimum entropy generation and Nusselt number occur in the pure fluid at any Rayleigh number. Results depict that the addition of nanoparticles to the pure fluid has more effect on the entropy generation as the Rayleigh number goes up.     

Darcy–Forchheimer up/downflow of entropy optimized radiative nanofluids with second-order slip,nonuniform source/sink,and shape effects

This article examines the influence of single-walled carbon nanotube (SWCNT)/multi-walled carbon nanotube (MWCNT) nanoparticles shapes on the radiative up and down flow of nanofluids past a thin needle. This nanofluid flow is considered in the presence of Darcy-Forchheimer effects, thermal radiation, Wu's slip, and non-uniform heat source/sink. Brick, cylinder, platelet, and blade shapes of nanoparticles are considered. Numerical solutions are attained by a well-known shooting technique. A comprehensive discussion regarding the effects of physical parameters on velocity, temperature, skin friction coefficient, and local Nusselt number is carried out. Outcomes reveal that fluid velocities of SWCNT/MWCNT-Water nanofluids behave in the opposite manner in up and down flows of nanofluids in the order of brick, cylinder, platelet and blade-shaped nanoparticles. The porosity parameter regulates the heat transfer rate efficaciously. The surface viscous drag intensifies for the nanofluids involving the nanoparticles in the order of their shapes as brick, blade, cylinder, and platelet.     

Numerical analysis of entropy generation in mixed-convection MHD flow in vertical channel

A numerical analysis is performed of the entropy generation within a combined forced and free convective magnetohydrodynamic (MHD) flow in a parallel-plate vertical channel. The MHD flow is assumed to be steady state, laminar and fully developed. The analysis takes account of the effects of both Joule heating and viscous dissipation. The nonlinear governing equations for the velocity and temperature fields are solved using the differential transformation method (D.T.M.). It is shown that the numerical results are in good agreement with the analytical solutions. The numerical values of the velocity and temperature are used to derive the corresponding entropy generation number (N_s) and Bejan number (B_e) within the vertical channel under asymmetric heating conditions. The results show that the minimum entropy generation number and the maximum Bejan number occur near the centerline of the channel. Overall, the results confirm that the differential transformation method provides an accurate and computationally-efficient means of analyzing the nonlinear governing equations of the velocity and temperature fields for MHD flow.     

Second law analysis of pseudo-plastic nanofluid stream past a stretching sheet with a sliding consequence

The entropy generation (second law of thermodynamics) analysis of gyrotactic microorganism flow of power-law nanofluid with slip effects and combined effect of heat and mass transfer past a stretching sheet has been studied. The flow is maintained with Lorentz force and thermal radiation. The governing nonlinear partial differential equations are transformed into ordinary differential equations using similarity transformations. The impact of different physical parameters, such as convective bouncy parameter, power-law parameter, Brownian motion parameter, thermophoresis parameter, and slip parameter for velocity and temperature on the entropy generation number (Ns) are plotted graphically with the help of MATLAB built in bvp4c solver technique. Further, the uniqueness of this study is to find out the ratios of various irreversibilities due to thermal and mass diffusions, momentum diffusion, and microorganism over the total entropy generation rate. Our results showed that the power-law parameter and Brownian motion parameter influenced entropy generation positively. The slip parameter for velocity and temperature and the thermophoresis parameter helps to reduce the entropy production.     

Effect of maximum and minimum heat capacity rate on entropy generation in a heat exchanger

This paper presents a theoretical analysis of a heat exchanger with a negligible fluid flow pressure drop to determine whether it is better to operate the heat exchanger with the minimum or maximum heat capacity rate of the hot fluid from entropy generation point of view. Entropy generation numbers are derived for both cases, and the results show that they are identical, when the heat exchanger is running at a heat capacity ratio of 0.5 with heat exchanger effectiveness equaling 1. An entropy generation number ratio is defined for the first time, which has a maximum value at ε = 1/(1+R) for any inlet temperature ratio. When R equals 0.1, 0.5 and 0.9, the entropy generation number ratio receives a maximum value at an effectiveness equaling 0.91, 0.67 and 0.526, respectively. When R=0.9, the entropy generation number ratio is the same for all inlet temperature ratios at ε=0.8. The results show that the entropy generation number ratio is far from 1 depending on the inlet temperature ratio of the cold and hot fluid. The results are valid for parallel‐flow and counterflow heat exchangers. Copyright © 2010 John Wiley & Sons, Ltd.     

Analysis of entropy generation using nanofluid flow through the circular microchannel and minichannel heat sink

In this paper, different types of entropy generations in the circular shaped microchannel and minichannel are discussed analytically using different types of nanoparticles and base fluids. In this analysis, Copper (Cu), alumina (Al₂O₃) as the nanoparticle and H₂O, ethylene glycol (EG) as the base fluids were used. The volume fractions of the nanoparticles were varied from 2% to 6%. In this paper, the irreversibility or entropy generation analysis as the function of entropy generation ratio, thermal entropy generation rate and fluid friction entropy generation rate for these types of nanofluids in turbulent flow condition have been analyzed using available correlations. Cu–H₂O nanofluid showed the highest decreasing entropy generation rate ratio (36%) compared to these nanofluids flow through the microchannel at 6 vol.%. The higher thermal conductivity of H₂O causes to generate much lower thermal entropy generation rate compared to the EG base fluid. The fluid friction entropy generation rate decreases fruitfully by the increasing of volume fraction of the nanoparticles. Cu–H₂O and Cu–EG nanofluid gave the maximum decreasing rates of the fluid friction entropy generation rate are 38% and 35% respectively at 6% volume fraction of the nanoparticles. Smaller diameter showed less entropy generation in case of all nanofluids.     

Magnetohydrodynamics Eyring-Powell fluid in a vertical porous microchannel with convective boundary condition subjected to entropy generation

This investigation is concentrated on the second law analysis of a magnetohydrodynamics Eyring-Powell fluid in a vertical microporous channel with the convective boundary conditions under the impacts of heat generation, viscous dissipation, exponential space, temperature dependence, and Joule heating. The reduced form of the governing equations is obtained with the aid of applying nondimensional variables and is resolved using Runge-Kutta-Fehlberg's fourth fifth-order method. The various relevant parameters that affect the heat transfer and entropy have been discussed in detail through graphs. It is found that the impacts of suction/injection, viscous dissipation, and convective conditions are important and the thermal performance can be improved with these factors. The generation of entropy boosts up with the impacts of radiation, space/temperature-dependent, and Biot number and slows down with Eyring-Powel parameters. Furthermore, the heat transfer rate amplifies with the magnetic number and the drag force intensifies with the Brinkman parameters. The comparison of results has been performed and it provides an excellent agreement.     

Salient features of Dufour and Soret effect in radiative MHD flow of viscous fluid by a rotating cone with entropy generation

BackgroundHere physical characteristics of convective magnetohydrodynamic flow of viscous liquid subject to a rotating cone are discussed. Dissipation, Joule heating, thermal flux and heat generation/absorption are scrutinized in energy expression. Physical aspects of diffusion-thermo and thermo diffusion effect are deliberated. Thermo-diffusion is the mechanisms of transportation in which particles are transferred in a multi-factor mixture determined by temperature gradient. Furthermore irreversibility analysis is considered.MethodNonlinear partial differential system are reduced to ordinary one with the help of similarity variables. Here we implemented ND solve technique to get numerical results for given nonlinear system.ResultsCharacteristics of influential variables for entropy optimization, velocity, concentration, Bejan number and temperature are scrutinized. Numerical outcomes of gradient of velocity and Nusselt and Sherwood numbers are examined through tabulated form. Velocity components are declined against higher velocity slip parameters. For larger estimation of heat generation and radiation parameters the temperature is upsurges. Entropy generation and Bejan number are boost up via rising values of diffusion and radiation parameters. For larger estimation of Brinkman number both Bejan number and entropy rate have opposite effect. Comparative studies of the current and previous results are discussed in tabularized form and have a good agreement.     

An analysis of entropy generation through a circular duct with different shaped longitudinal fins for laminar flow

The present study focuses on the entropy generation analysis in a circular duct with internal longitudinal fins of different shape for laminar flow. Three different fin shapes are chosen for the analysis: Thin, triangular and V-shaped fins. Calculations are performed for various dimensionless lengths and number of fins, dimensionless temperature difference and fin angle for triangular and V-shaped fins. It is found that the number of fins and dimensionless length of the fins for both thin fins and triangular fins, and the fin angle for triangular and V-shaped fins have significant effect on both entropy generation and pumping power. Further, both entropy generation and pumping power also are influenced by dimensionless temperature difference.     

Entropy generation on MHD peristaltic flow of Cu‐water nanofluid with slip conditions

The current research explores entropy generation and effect of magnetic field on peristaltic flow of copper‐water nanofluid in an asymmetric configuration saturated with porous medium. Slip conditions are invoked for velocity and temperature. Governing flow problem is constructed under the long wave length assumption. Analytical result for the problem is computed by exploiting homotopy analysis methodology. The influences of involved physical parameters are investigated through plots.     

Thermo-electrokinetic rotating non-Newtonian hybrid nanofluid flow from an accelerating vertical surface

This paper explores the combined effects of Coriolis force and electric force on the rotating boundary layer flow and heat transfer in a viscoplastic hybrid nanofluid from a vertical exponentially accelerated plate. The hybrid nanofluid comprises two different types of metallic nanoparticles, namely silver (Ag) and magnesium oxide (MgO) suspended in an aqueous base fluid. The Casson model is deployed for non-Newtonian effects. An empirical model is implemented to determine the thermal conductivity of the hybrid nanofluid. Rosseland's radiative diffusion flux model is also utilized. An axial electrical field is considered and the Poisson–Boltzmann equation is linearized via the Debye–Hückel approach. The resulting coupled differential equations subject to prescribed boundary conditions are solved with Laplace transforms. Numerical evaluation of solutions is achieved via MATLAB symbolic software. A parametric study of the impact of key parameters on axial velocity, transverse velocity, nanoparticle temperature and Nusselt number is conducted for both the hybrid (Ag–MgO)–water nanofluid and also unitary (Ag)–water nanofluid. With increasing volume fraction of silver nanoparticles, there is a reduction in both axial velocity and temperatures, whereas there is a distinct elevation in transverse velocity for both unitary and hybrid nanofluids. Elevation in the heat absorption parameter strongly decreases axial velocity, whereas it enhances transverse velocity. Increasing the radiation parameter strongly boosts temperatures. Increasing the heat absorption parameter significantly accelerates the transverse flow. Negative values of Helmholtz–Smoluchowski velocity decelerate the axial flow whereas positive values accelerate it; the opposite behavior is observed for transverse velocity. Increasing Taylor number significantly damps both the axial (primary) and transversal (secondary) flow. Increasing thermal Grashof number strongly enhances the axial flow but damps the transverse flow. The unitary nanofluid achieves higher Nusselt numbers than the hybrid nanofluid but these are decreased with greater radiative effect (due to greater heat transport away from the plate surface), Prandtl number and heat absorption. Nusselt number is significantly reduced with greater time progression and values are consistently higher for the unitary nanofluid compared with hybrid nanofluid. The computations provide insight into more complex electrokinetic rheological nanoscale flows of relevance to biomedical rotary electro-osmotic separation devices.     

Generation of entropy during forced convection of heat in nanofluid stagnation-point flows over a cylinder embedded in porous media

Thermodynamics and heat transfer of an impinging nanofluid flow upon a cylinder with constant surface temperature and embedded in porous media are investigated. Numerical solutions reveal the flow velocity and temperature fields as well as the Nusselt number. These are then used to calculate the rate of entropy generation within the system by viscous and heat transfer irreversibilities. It is demonstrated that changes in the concentration of nanoparticles modify the thermal and hydrodynamic boundary layers and hence can alter the Nusselt number and entropy generation considerably. However, the shear stress on the surface of the cylinder is observed to be less affected by the variations in the concentration of nanoparticles. Further, the Reynolds number and non-uniform transpiration are shown to affect the Nusselt number and entropy generation. It is argued that the influences of Reynolds number on the boundary layer thickness can majorly modify the irreversibility and Bejan number.