Entropy Generation Analysis Research Articles

Thermodynamic performance of Al2O3-Cu-CuO/water (W) ternary nanofluids in the full-flow regime of convective heat transfer

To explore the convection mechanisms of ternary nanofluids in the full-flow regime (laminar-transition-turbulent regime), the thermodynamic performance of Al2O3-Cu-CuO/W ternary nanofluids (with a volume fraction of 0.02 vol%) and their corresponding mono nanofluids was investigated in Reynolds number (Re) range of 800–8000 in a cylindrical tube. The results showed that the presence of suspended particles in the Al2O3-Cu-CuO/W nanofluids caused the transition regime to shift to a lower Re value of ∼ 1900. As Re was increased, the heat transfer performance exhibited a fluctuating upward trend, with a maximum at Re = 5250. Further, the ternary nanofluid with a mixing ratio of 30:30:40 showed a Nu 1.73 times that of the base fluid, with the corresponding values for the CuO/W and Al2O3/W nanofluids being only 1.36 and 1.39 times, respectively. Moreover, the thermal conductivity of the ternary nanofluids had a substantial impact on heat transfer performance in the laminar regime, with a correlation coefficient, r, of 0.6429, but less of an influence in the turbulent regime, with an r value of only 0.5. Finally, the optimum mixing ratio for the convective heat transfer process was determined to be 30:50:20 based on the values of Nusselt number enhancement rate and enhanced heat transfer factor, as well as on thermodynamic analysis of the system entropy generation and exergy.

Numerical analysis of entropy generation in a solar desalination plant with nanofluid and a layer of phase change material in its reservoir

The acquisition of drinking water is discussed in this paper by three-dimensional modeling of a solar desalination plant focusing on renewable energies. The reservoir of the desalination plant contains aluminum nanoparticles with a constant weight percent. A layer of n-Eicosane phase change material (PCM) with various thicknesses is used at the bottom of the desalination plant reservoir. The objective of the present paper is to examine the entropy generation, including frictional, thermal, and total entropy generation in the flow of steam and air inside the desalination plant and the use of the PCM layer. The angle of the glass changes from 10 to 45°, and the thickness of the PCM layer varies during the day. The nanofluid flow is assumed to be two-phase, and the finite element method (FEM) is employed to solve the equations using COMSOL software. The results show that increasing the glass angle enhances the frictional entropy generation, and decreases the thermal entropy generation. Using PCM with a thickness of 50 mm reduces the thermal entropy generation in the steam, especially in the afternoon. The amount of PMC thickness changes the total entropy generation in the PMC.

Entropy generation analysis of hybrid nanofluid through flexible tube with convective conditions

Entropy generation analyses of hybrid nanofluids via compliant wall tubes are performed with peristalsis effects in this study. Thermophysical properties of nanofluid are incorporated in mathematical formulations for various shapes of nanoparticles. Convective conditions on the boundary are considered. Momentum and energy equations are modeled and simplified under the lubrication approach. Solutions are calculated numerically using MATHEMATICA. The impact of various related parameters on flow quantities is observed via graphs. The study reveals greater entropy generation for blade-shaped nanoparticles.

Application of nanofluid flow in entropy generation and thermal performance analysis of parabolic trough solar collector: experimental and numerical study

Application of nanofluid flow in entropy generation and thermal performance analysis of parabolic trough solar collector: experimental and numerical study

Entropy generation analysis for hydromagnetic two-layered pulsatile immiscible flow with Joule heating and first-order chemical reaction

The current research deals with the MHD pulsating flow of two immiscible liquid layers with joule heating and first-order chemical reaction. The channel is partitioned into two regions with different fluid widths. The governing flow equations are transformed using a perturbation approach into a system of ODEs. The R-K 4th-order approach is used with the shooting technique to solve the resulting ODEs. The effect of several emerging parameters on flow characteristics is depicted graphically and explained. The impact of liquid widths on velocity distribution, temperature and concentration are also presented for the cases: (i) when kerosene dominates the fluid flow, (ii) when water dominates the fluid flow, (iii) when both fluids occupy equal space in the channel. Moreover, the Nusselt and Sherwood numbers are calculated at the boundaries of the channel and presented through 3-D graphs. Further, shear stress for both channel walls and mass flux results are presented in tabular form. The outcome predicts that stress at the lower boundary is always greater than at the upper boundary. And, when the rate of heat transfer is measured over time, it has an oscillatory nature and is higher at the lower boundary than at the upper boundary.

Field synergy and thermodynamic evaluation of a mini-duct with several protrusions utilizing the cross-flow method: A numerical exercise

The field synergy and entropy generation analysis of turbulent flow in a mini rectangular duct featuring surface protrusions has been numerically explored in a finite volume approach. The governing differential is solved iteratively using adequate numerical boundary conditions and a second-order upwind technique. In the post-processing, entropy generation, and irreversibilities are measured. The duct Reynolds number (ReDh, duct) has been varied from 17,831 to 53,492 at a fixed nozzle Reynolds number (ReDh, nz) of 5104. The effects of the duct Reynolds number on the thermal and frictional irreversibility have been quantified. Thermal, frictional, and total irreversibilities have been reported to rise with ReDh, duct. Furthermore, it is discovered that thermal irreversibility dominates over frictional irreversibility. It has been found that conducting triangular protrusions creates more entropy than conducting rectangular protrusions. Filed synergy analysis has also been carried out by integrating the energy equation. Heat transfer rate has been seen to increase with synergy angle (α). Triangular protrusions have a greater field synergy angle (α) than rectangular protrusions.

Entropy generation analysis of electroosmotic mixed convection flow in vertical microannulus with asymmetric heat fluxes

Flow formations and heat transfer of electroosmotic flow have significant applications in area of heat exchanger and recently for chemical separation at microlevel. Therefore in this article, exact solutions for entropy generation rate of electroosmotic mixed convection flow in a vertical microannulus subject to asymmetric heat fluxes are presented. Closed form solutions in terms of Bessel's functions are obtained for electric potential, fluid velocity, temperature, skin-friction, Nusselt number and entropy generation after transforming the governing equations into their corresponding dimensionless forms. The obtained solutions are graphically represented using MATLAB software in order to ascertain the role of various pertinent parameters entering flow formation and heat transfer. Results obtained showed that entropy generation rises with increase in radius ratio and electroosmotic force but decreases with increase in slip and buoyancy parameters. Also, irreversibility due to fluid friction or applied electric field is sufficient to dominant the overall entropy generation rate in the presence of strong buoyancy force. On application point of view, fluid velocity, temperature distributions, skin-friction, volumetric flow rate, Nusselt number and entropy generation rate can be optimized by careful selection of governing parameters.

Entropy Generation Analysis in Magnetohydrodynamic Couple Stress Nanofluid Flow Through an Oblique Microchannel in a Permeable Medium with Thermal Radiation

The present work examines the flow and thermal energy process in conducting couple stress nanofluid flows through an oblique microchannel. The microchannel is embedded with permeable medium and thermal radiation is implemented. The microchannel boundaries retain the slip boundary conditions. The impact of buoyancy force and magnetic field are incorporated. The temperature dependent heat source effect was also taken into account. The momentum equation has been made by the permeability of the porous medium. The equations are modeled and non-dimensionalized using non-dimensional entities and further solved with the aid of the Runge-Kutta Fehlberg method and the shooting procedure. The detailed discussions about the importance of the effective parameters on entropy generation, the Bejan number have been observed through graphs. The findings of the examination depict that rise in radiation parameter augments the entropy generation and the Bejan number in the channel. The entropy generation and Bejan number diminishes with inflation of the permeability parameter.

Numerical investigation for entropy‐based magneto nanofluid flow over non‐linear stretching surface with slip and convective boundary conditions

AbstractThe nanoliquid flows place a significant role in modern research due to the vast number of applications in the Food industry, manufacturing, thermal management, enhanced oil recovery, biomedical applications, and so on. This article presents the analysis of entropy generation on convective nanofluid flow in a three‐dimensional nonlinear stretching sheet with slip effects. Brownian motion and thermophoresis impacts are adopted by the nanoparticle concentration and temperature profiles. The PDEs are remodeled into ODEs by employing the appropriative simulated alternations, and the ODEs are solved by utilizing the R–K–F scheme along with the shooting technique. The main contributions of physical stream factors on the nanofluid concentration, heat, and speed profiles are displayed and explored via plots. Moreover, the rate of heat transfer and surface drag force are examined through tabular structures. In view of this, the nanofluids have more heat transfer capability and improve thermal properties. The slip factors are used in the boundary conditions of the velocity, and the limit conditions are utilized for the hotness and speed of the nanoparticles. The rate of heat transfer in a non‐linear stretching sheet is 1%–2% more than linear stretching sheet for varying values of Prandtl number Pr and Magnetic field M.

Convective Heat Transfer and Entropy Generation for Nano-Jet Impingement Cooling of a Moving Hot Surface under the Effects of Multiple Rotating Cylinders and Magnetic Field

In this study, confined slot nano-jet impingement cooling of a hot moving surface is investigated under the combined utilization multiple rotating cylinders and magnetic field. Both convective heat transfer and entropy generation analysis are conducted using a finite element method. Parametric variation of the rotational Reynolds number (Rew between −500 and 500), velocity ratio (VR between 0 and 0.25), Hartmann number (Ha between 0 and 20) and the horizontal location of cylinders (Mx between −8 and 8) are considered. Rotation of the cylinders generally resulted in the degradation of cooling performance while increasing the wall velocity, and the horizontal location of the cylinder was found to positively contribute to this. Heat transfer rate reductions of 20% and 12.5% are obtained using rotations at the highest Rew for the case of stationary (VR = 0) and moving wall (VR = 0.25). When magnetic field at the highest strength is imposed in the rotating cylinder case, the cooling performance is increased by about 18.6%, while it is reduced by about 28% for the non-rotating cylinder case. The hot wall movement contributes, by about 14%, to the overall cooling performance enhancement. Away from the inlet location of the rotating cylinders, thermal performance improvement of 12% is obtained. The entropy generation rises with higher hot wall velocity and higher horizontal distances of the rotating cylinders, while it is reduced with a higher magnetic field for non-rotating cylinders. The best configurations in terms of cooling performance provide 8.7% and 34.2% enhancements for non-rotating and rotating cylinders compared with the reference case of (Rew, VR, Ha, Mx) = (0, 0, 0, 0), while entropy generation becomes 1% and 15% higher.

Entropy generation analysis of turbulent flow in conical tubes with dimples: a numerical study

Minimizing the entropy generation rate is one of the key performance indicators for enhancing the thermal design of heat exchangers. This paper introduces a comprehensive numerical entropy generation analysis of turbulent water flow inside—newly proposed—conical tubes with dimples subjected to a constant heat flux. The effect of different tube diameter ratios (DR = 1, 1.5, 2, 3, and 5) and flow modes (convergent and divergent tube configurations) on the thermal, viscous, and total entropy generation rates is investigated within Reynolds number (Re) range of 3 × 103–40 × 103 using ANSYS-Fluent package. Realizable k-ε (RKE) turbulence model is adopted in this study. A well-validated 3D model was adopted to estimate the dimensionless indices: Bejan number (Be), enhanced entropy generation ratio (Ns,en), and the irreversibility distribution ratio ({phi }_{mathrm{s}}) to characterize the entropy generation performance and to compare conical dimpled tubes to smooth ones. The results showed that total entropy production rate values for dimpled tube geometries are lower than those for the corresponding smooth ones, especially for convergent dimpled tubes. Convergent dimpled tubes with DR in the range of 1.5–3 achieved the lowest total entropy production values over the whole Re range, with an average value of 0.20 W K−1, as compared to an average value of 0.34 W K−1 for the smooth configurations. The average Ns,en values for dimpled convergent tubes with DR = 1.5–3 are 0.46 and 0.80 at Re = 3000 and 40,000, with reductions of 50.54% and 3.61% at both Re values, respectively. The study also showed that the entropy generation analysis could provide an effective tool to highlight the optimal design of tube heat exchangers based on the minimum entropy generation and the enhanced entropy generation ratio.

Analysis of internal flow characteristics and entropy generation of low head bulb tubular pump

To study the internal flow characteristics and energy characteristics of a large bulb perfusion pump. Based on the CFX software of the ANSYS platform, the steady calculation of the three-dimensional model of the pump device is carried out. The numerical simulation results obtained by SST k-ω and RNG k-ε turbulence models are compared with the experimental results. Finally, SST k-ω is selected for subsequent calculation. With the help of the flow line diagram and turbulent kinetic energy table of the whole flow channel of the pump device, the flow components of the pump device under different working conditions are analyzed, and the pressure and velocity distribution at the impeller and guide vane are analyzed by pressure cloud diagram and velocity cloud diagram. It is found that there are three high-pressure areas in the impeller and guide vane section, and the high-pressure regions are mainly distributed in the middle of the impeller channel. As the head decreases, the pressure at the impeller and guide vane positions decreases gradually, and the flow rate increases. Based on the entropy production principle, the wall entropy production and the distribution of mainstream entropy production at the impeller and guide vane parts are analyzed.

Entropy generation and thermohydraulics of mixed convection of hybrid-nanofluid in a vertical tube fitted with elliptical‑cut twisted tape inserts - a computational study

ABSTRACT A numerical investigation is carried out to study the mixed convection of Al2O3-Cu/water hybrid-nanofluid in a vertical tube fitted with elliptical-cut twisted tape inserts (TECT). Thermodynamic irreversibilities are evaluated by calculating the Bejan number, as well as the system’s local and total entropy generation. Heat transfer, friction factor, thermal performance factor, and entropy generation analyses are conducted for a range of volumetric concentrations of nanoparticles and flow Reynolds numbers between 7000 and 15,000. The realizable k- model is employed to simulate the turbulent and heat transferring flow computationally. The results clearly demonstrate the influence of mixed convection on heat transfer and entropy generation. In particular, mixed convection simulations predict greater Nusselt number, friction factor, and thermal performance factor than the corresponding forced convection simulations. Further, it is shown that the Nusselt number and the thermal performance factor for mixed convection are 4.6% and 5.5% higher than those for forced convection, respectively. The results also reveal that at Reynolds numbers of 7000, 9000, and 11,000, the thermal entropy production dominates the total irreversibility of the system. Likewise, frictional entropy production is the dominant mode of total irreversibility in the system at high Reynolds numbers of 13,000 and 15,000.

Entropy Generation and Radiation Analysis on Peristaltic Transport of Hyperbolic Tangent Fluid with Hybrid Nanoparticle Through an Endoscope

The current study explores the impact of entropy generation, thermal jump, radiation, and inclined magnetic field on the peristaltic transport of hyperbolic tangent fluid containing molybdenum disulfide and silver nanoparticles through an endoscope with a long wavelength and low Reynolds number assumptions. Between two coaxial tubes, a non-Newtonian hyperbolic tangent fluid with silver nanoparticles is considered. The Second law of thermodynamics is used to examine the entropy generation. The Homotopy perturbation method (HPM) is applied to describe the solution of nonlinear partial differential equations. We were able to arrive at analytical solutions for velocity, temperature, and nanoparticle concentration. In the end, the impact of various physical parameters on temperature, nanoparticle concentration, velocity, entropy generation, and Bejan number was graphically depicted. The significant outcome of the present study is that the impact of Hartmann number and Brownian motion parameter declines the velocity profile, but the thermal Grashoff number enhances velocity, whereas Platelet-shaped nanoparticles achieve a higher speed as compare to Spherical-shaped nanoparticles.

Thermal Management of Lithium-ion Battery based on Flow and Heat Transfer Entropy Generation Analysis

In order to realize the problem of efficient heat dissipation management of lithium battery modules, the thermal management model of liquid cooled lithium-ion battery modules is studied in this paper. The entropy increase characteristics caused by the flow process and heat transfer process of the lithium-ion battery module under three liquid cooling inlet and outlet modes are analyzed by numerical simulation, and the internal mechanism of the local entropy generation characteristics of the lithium-ion battery module is clarified. The numerical results show that the 3×3 MIMO is the best model considering the heat dissipation and fluidity of the protective fluid. In addition, the results of this study can provide effective design guidance for thermal management of lithium-ion batteries.

Entropy generation analysis of a three-dimensional coal-fired furnace: A realistic study

An analysis of the entropy generation by radiative heat transfer in a three-dimensional virtual coal-fired furnace is performed. The gases, including CO2 and H2O, and particles, including soot, unburnt char and ash, are considered as a participating medium. The radiative transfer equation for a non-grey medium was solved by the discrete ordinate method, in which the radiative properties of the gases, soot, unburnt char and ash were obtained by using the statistical narrow-band correlated-k model, Rayleigh's theory, and Mie theory, respectively. The distributions of the local volumetric rate of entropy generation and the local rate of entropy generation at the wall are calculated. The contributions of various media in coal-burning furnaces to the radiative entropy generation rate (REGR) are evaluated, and the effects of several important factors, such as the oxidizer atmosphere, burnout rate, and the volume fraction of soot, unburnt char and ash on the REGR and dimensionless entropy generation were also investigated. The numerical results show that the irreversibility of the particle radiation contributes more than 80% of the volumetric radiative entropy generation. The concentration of particles also has an important effect on REGR, which decreases by 41% when the concentration of unburnt char and ash increases from 10 ppm to 50 ppm and decreases by 70% when the concentration of soot increases from 1 ppm to 6 ppm in a real-size furnace such as an optically thick furnace.

Numerical and experimental investigation of irreversible energy losses in a two-stage radial turbine under asymmetric inflow conditions

In a two-stage turbocharger, the coupling between stages and the structure of the inter-stage duct may lead to severe flow distortions, which have a destructive impact on turbine performance. In this paper, the aerodynamics and energy loss mechanisms of two-stage turbines matched with a V-6 diesel engine are experimentally and numerically investigated. To reveal the formation mechanism of the asymmetric inter-stage flow, the vortex transportation in the high-pressure turbine is first analyzed. Entropy generation analysis is applied to quantify the irreversible losses while considering the coupling influence of the asymmetric inflow conditions, and two types of curved inter-stage ducts are studied. The sources of the dominant irreversible losses are revealed and origin of the corresponding energy loss is localized. The results show that the entropy generation rates associated with viscous dissipation, turbulent dissipation, and heat conduction account for about 30% each in the low-pressure turbine. Compared to uniform inflow conditions, the entropy generation rates increase by an average of 43.8%, 196.9%, and 19.2%, respectively under asymmetric inflow conditions. The pivotal turbulent dissipation is primarily concentrated in the inter-stage duct, the impeller inlet, and the volute tongue. The peak value for the difference in the cumulative entropy generation rates from turbulent dissipation is mainly caused by the mixing of the leakage vortex and the separation flow. The novelty of the present study lies in revealing the source of irreversible losses in two-stage turbines, which may provide a fundamental basis for the optimal design of a two-stage turbocharger.

Applications of extended surfaces for improvement in the performance of solar air heaters-a detailed systematic review.

The objective of this research article is to present a comprehensive review of the work carried out to improve the thermal as well exergetic performance of the conventional smooth absorber plate solar air heater (SAH) duct by the use of the various configurations and arrangements of extended surfaces (fins) for the forced convection. In the SAH duct, these extended surfaces are attached along the air-flow path on the top absorber, on the bottom plate, or on the both plate surfaces. It enhances the performance of the conventional SAH by increasing the surface area and makes flow turbulent by their presence. Several experimental, theoretical, and simulation works, which have been performed by the researchers by utilizing the extended surfaces to improve the thermal efficiency based on first law of thermodynamics, exergy, and entropy generation analysis on the basis of the second law of thermodynamics for SAH ducts, have been included in the present article. Subsequently, an effort has been made to calculate the Nusselt number and friction factor by using the correlations reported by the researchers for comparing the performance of different configurations of fin SAHs. This comprehensive review article will be useful for the investigators and researchers who are working in the area of extended surface SAHs.

Entropy generation on MHD Casson and Williamson hybrid nanofluid over a curved stretching sheet with the Cattaneo–Christov heat flux model: semi-analytical and numerical simulations

This study demonstrates the results of a non-Newtonian comparative analysis of entropy generation on the MHD flow of a permeable curved stretching sheet with thermal radiation using the Cattaneo-Christov heat flux model. Mathematical modelling of hybrid nanofluid flow containing titanium dioxide (TiO2 ) and silver (Ag) as nanoparticles and blood as a base liquid through a curved stretching sheet has been investigated, which has vital application in the field of drug delivery. The controlling non-linear coupled PDEs are transformed into ODEs with similarity variables and then solved using the Homotopy Perturbation Method (HPM) and shooting technique (Runge Kutta fourth order). The velocity, temperature, entropy production, and Bejan number on various physical parameters like curvature, magnetic field, thermal relaxation, mixed convection, and thermal radiation parameters are discussed and explored through graphs. The heat transfer and skin friction coefficients are also studied and portrayed via graphs. The velocity profile decreases for Casson and Williamson fluids, as the magnetic field parameter and porosity parameters are increased. When the thermal relaxation parameter increases, the temperature profile decreases. The impact of the Titanium dioxide (TiO2 ) nanoparticle in volume fraction and silver (Ag) nanoparticles in volume fraction enhanced the temperature profile for Casson and Williamson fluids.

Entropy generation analysis in MHD hybrid nanofluid flow: Effect of thermal radiation and chemical reaction

The current study computationally investigates the thermally radiative incompressible flow of hybrid nanofluid induced by a radially stretchable rotating disk with entropy generation analysis. The temperature-dependent viscosity of hybrid nanofluid, stretching of the disk, chemical reaction, Joule, and viscous dissipation effects are incorporated in the formulation of the mathematical flow model. In this study, Karman’s transformations are used to convert the governing equations of partial derivative form into their ordinary derivative form, which is evaluated numerically together with boundary conditions using the BVP Midrich technique built-in Maple software. The impacts of variable viscosity parameter, magnetic field parameter, radiation parameter, Eckert number, Prandtl number, Biot Number, and chemical reaction parameter on flow-field factors and entropy generation rate are presented graphically. The outcomes indicate that higher estimations of magnetic field parameter and entropy generation rate increase the velocity distribution. Also, an increment in Schmidt number and chemical reaction parameter diminishes hybrid fluid concentration, and a higher magnetic field parameter maximizes the same. This study is significant in industrial thermal management and heat transport increment in renewable energy systems.