Entropy Generation Analysis Research Articles

Partial magnetic field and segmental heating effects on hybrid nanofluidic convection in a tilted porous wavy cavity

The present study investigates the magneto-thermal convective process in an oriented porous wavy-walled geometry filled with Cu–Al2O3/water hybrid nanofluid, which is partially heated from the upper and lower walls under a partially active magnetic field. The sidewalls are cooled, while heating is carried out from the upper or lower walls or both. The flow-physics are greatly affected by the segmental heating and their positions, sidewall curvature, spatially active partial magnetic field, and all the flow-controlling variables. The transport equations are solved using the finite volume technique with SIMPLE and TDMA solver-based computing code. The hydro-thermal behavior of the thermal system is evaluated for several important variables, such as the Darcy-Rayleigh number, Hartmann number, Darcy number, concentration of hybrid nanofluid, partially active magnetic field strength, inclination and positions, geometry orientation, length of segmented heaters, and their position. It is revealed that the overall thermal transport phenomena can be precisely controlled by adjusting the position and dimension of segmented heaters, the active zone and direction of the imposed magnetizing field, and the cavity angle. Both the cavity angle and magnetic field angle of 90° enhance heat transfer. Top wall heating produces weak circulation. In the case of position study for segmental heating, the sidewall position is the best location for maximum heat transfer. The circulation strength and heat transfer are maximum for the bottom heated scenario, and the transfer enhancement goes up to 132.91%. In addition, an entropy generation analysis is conducted to understand the order of thermal, viscous, and magnetic effects on irreversibility production. The results demonstrate the effectiveness of the proposed approach in optimizing the system's performance.

Experimental and numerical analysis of convective heat transfer and entropy generation of graphene/water nanofluid in AEAOT heat exchanger

BackgroundEffective utilization of nanofluid's potential and optimal heat exchanger design is paramount in addition to heat transfer enhancement. A novel alternate elliptical tube is fabricated, and graphene nanofluids are chosen to enhance the convective heat transfer characteristics. MethodsThe experimental setup is validated with circular pipe results before conducting graphene nanofluid experiments. The finite volume method was adopted to conduct simulation results, and its validation was done with the experimental results. The results of numerical simulations are compared with experiments, and the obtained mean percentage error (MPE) is 1.17%, 8.71%, 8.05% and 8.85% for water, G0.05%, G0.1% and G0.2%, respectively. Experiments are conducted at different mass flow rates and inlet temperatures of nanofluid. Significant findingsThe oval tube in an alternate direction improves the secondary flow region with a high swirl, leading to a smaller thermal boundary layer thickness. Nusselt number enhances as an average of 10.3%, 29.2% and 39.1% for graphene nanofluids prepared using weight concentrations 0.05%, 0.1% and 0.2%, respectively, at 80 °C. The effect of inlet temperature reveals heat transfer coefficient and Nusselt number increase and 1.57, 1.88, 2.16 times than water is observed for G0.05%, G0.1% and G0.2%, respectively. Pertinent to entropy generation, Bejan number (Be) decrease with graphene nanoparticle concentration; as inlet temperature increases, corresponding fluid friction irreversibilities are observed as 18.4%, 24.6% and 36.4% for G0.05%, G0.1% and G0.2% nanofluids, respectively. The present work caters for the importance of AEAOT design which prompts heat transfer enhancement; indeed, optimization of transition length and aspect ratio are essential to overcome the pressure loss cost.

A comparative study of plain and enhanced helical microfin evaporator tube with drift flux-based entropy generation model for R32 and R410A refrigerants

In the present paper, a comparative study is carried out to assess the relative thermodynamic performance of plain and helical microfin evaporator tubes with two new emergent refrigerants, R32 and R410A. An entropy generation analysis is performed based on the drift flux model for two-phase forced convective boiling flow, and the comparison of the enhanced tube to the plain one is done quantitatively. A critical value of relevant parameters, i.e., mass flux, tube diameter, length, heat flux, inlet quality, and operating pressure, are identified, below or above which the enhanced tube is observed to be thermodynamically more favourable than the plain tube. The study reveals that by increasing the tube diameter from 8 mm to 14 mm, the critical mass flux increases from 335 kg/m2s to 495 kg/m2s for R32 and 394 kg/m2s to 565 kg/m2s for R410A, respectively, below which the enhanced tube performs better. The helical microfin tube exhibits a better performance below a critical mass flux from 412 kg/m2s to 374 kg/m2s for R32 and 492 kg/m2s to 443 kg/m2s for R410A when tube length increases from 1 m to 5 m. The critical inlet quality, below which the enhanced tube is observed to be superior, shifts to a lower value (0.29 to 0.16 for R32 and 0.44 to 0.26 for R410A), increasing the mass flux from 400 kg/m2s to 500 kg/m2s. However, the enhanced tube shows a better performance above a critical operating pressure, which increases from 11.4 bar to 16.9 bar for R32 and 9.3 bar to 13.4 bar for R410A, with increasing the mass flux from 400 kg/m2s to 500 kg/m2s. The enhanced tube performs better below a critical mass flux which increases from 336 kg/m2s to 461 kg/m2s for R32 and 399 kg/m2s to 489 kg/m2s for R410A when the heat flux is increased from 8 kW/m2 to 15 kW/m2. The overall parametric study with two emergent refrigerants enables one for effective selection of the helical microfin evaporator tube for a suitable range of relevant parameters.

Entropy generation analysis for chemically reactive flow of Sutterby nanofluid considering radiation aspects

Entropy generation analysis for chemically reactive flow of Sutterby nanofluid considering radiation aspects

Analysis of entropy generation in Carreau ternary hybrid nanofluid flow over a stretching sheet

In this study, we consider a steady-state viscous,laminar Carreau ternary-hybrid nanofluid flow over a stretching sheet with first-order slip and Ohmic dissipation.Further, we consider the effects of suction/injection, oblique Lorentz force, and a temperature jump boundary condition. We investigate here how to transport a Carreau ternary hybrid nano-fluid while minimizing the entropy it generates. We analyze in this article the flow of molybdenum disulfide (MoS2), silver (Ag), and multi-wall carbon nanotubes (MWCNT). Carboxymethyl cellulose (CMC-water) is the observed fluid of choice. Several industries could benefit from this research, including those dealing with the equations of the model are converted to a dimensionless form by appropriate similarity transformations. Using a shooting strategy with Runge-Kutta-Fehlberg and Secant methods the velocity and the temperature fields are obtained. The physical quantities such as the fluid flow rate, the temperature, the skin friction, the Nusselt number, the entropy minimization, and the Bejan number are presented graphically and analyzed. In our Carreau ternary hybrid nanofluid model it is found that an increase in the Weissenberg number is to decrease the velocity field. We also noticed a significant effect of the Brinkmann number which has a deleterious effect on the entropy-minimization and Bejan-number profiles.

Entropy Generation Analysis on a Metal Foam in an Automotive Exhaust Line with Thermoelectric Generator

Abstract In the present paper, an entropy generation analysis on a 2-D steady state problem in convective regime of an aluminum foam partially and totally filled channel with an external TEG element is solved in numerical way. The numerical analyses are accomplished with the assumption of the local thermal equilibrium (LTE) hypothesis in order to model the metal foam and heat transfer inside the channel. The working fluid is exhaust gas characterized by the same properties of the air in correspondence to the TEG upper surface temperature. The TEG is considered as a solid component characterized by an internal energy generation. The thermophysical properties are assumed temperature independent. Ansys-Fluent code is employed in order to resolve the governing equations for exhaust gas, metal foam and TEG. Different exhaust gas mass flow rates on the inlet section are assumed. Several thicknesses of aluminum foam values are employed. The porous media are characterized by a porosity from 0.90 to 0.978 and number of pores per inch (PPI) equal to 5, 10, 20, 40. Results are given in terms of global entropy generations related to the thermal and viscous effects. The total global entropy generation increases with increasing of exhaust gas flow rate for all pore density and porosity values. Bejan number decreases with the increment of mass flow rate and thickness. It increases when the porosity value increases whereas at high mass flow rate and for assigned porosity the values present small difference for different pore density values.

Numerical Analysis of Entropy Generation in a Double Stage Triangular Solar Still Using CNT-Nanofluid under Double-Diffusive Natural Convection

The analysis of entropy generation provides valuable information for the design and optimization of thermal systems. Solar stills are used for water desalination and purification. Using renewable energies, they provide a sustainable solution for drinking water supply in remote areas and off-grid situations. This work focuses on the 3D numerical study of entropy generation in a two-stage solar still subjected to the natural double diffusion convection phenomenon in the presence of CNT nanoparticles. The effects of Rayleigh number, buoyancy ratio, and nanofluid concentration on thermal, solutal, and viscous irreversibilities and flow structure were studied. The results show that increasing the buoyancy ratio leads to an increase in thermal and solutal entropy generation. The results of this study also show that total entropy is minimal for positive volume force ratios, N, at a nanoparticle volume fraction of around 3%, and for negative N ratios, at a volume fraction of around 4%.

Numerical investigation of the entropy generation analysis for radiative MHD power-law fluid flow of blood through a curved artery with Hall effect

In the last few decades, mortality rate due to blood vessel diseases has hiked rapidly and it is almost one-third of total mortalities. Identifying the vascular geometry and hemodynamic blood flow inside the artery is essential for preventing vascular disease progression. By motivating vascular diseases effects on the human body, a mathematical model has been developed to discuss the blood flow phenomena and entropy estimation in the stenosed curved artery in the presence of a magnetic field and the Hall effect. The patient-specific condition of elliptic shape stenosis has been considered at the arterial wall. Blood is considered in the artery as two-phases; core and plasma region. Power-law fluid has been considered for core region fluid, while, Newtonian fluid is considered in the plasma region. The non-dimensional governing equations have been discretized using the second-order central difference method. Then, Stone's strongly implicit scheme is used in the ‘MATLAB’ software to solve a system of nonlinear partial differential equations (PDEs). A computing error tolerance of has been set for each iteration step throughout the computing process. The influence of various parameters such Hall parameter (m), Brinkman number (Br), flow behavior index (q), Radiation parameter (N), magnetic field (M), arterial curvature, etc., have been discussed graphically. The present study concludes that the heat transfer rate enhances with the increase in the Hall parameter values while wall shear stress reduces with it. In addition, the chances of stenosis deposition rise for highly curvature arteries, and also blood produces more entropy with the increase in viscous heating and thermal radiation intensity. Results from the current computational study will aid clinical researchers in making more accurate predictions about the prevalence of vascular diseases.

Exploring a novel route for low-grade heat harvesting: Electrochemical Brayton cycle

Efficient technologies to convert huge amounts of low-grade heat to power are urgently desired. Although various electrochemical technologies have been proposed, the low thermal efficiency and power density still limit their practical applications. Starting from the ideal cycle of thermo-chemical engines and the decoupling of heat transfer and charge transport, this study proposes the electrochemical Brayton cycle (EBC) for power generation for the first time, which is realized by flow batteries and heat exchangers. By establishing energy and entropy generation models, the thermal efficiency and power density of ideal and actual EBC systems, as well as the isentropic efficiency and entropy generation are analyzed and discussed. The results indicate the ideal EBC without overpotential performs a maximum power density of 690 W m−2 and a relative efficiency to Carnot efficiency of 52.3% when operated between 25 and 75 °C. With 70% heat regeneration, the relative efficiency and power density of actual EBC could reach 45.3% and 1.6 W m−2 at an electrolyte flow velocity of 0.01 mm s−1, or 23.7% and 6.8 W m−2 at a velocity of 0.1 mm s−1, respectively. Further entropy generation analysis reveals that the main contributors to entropy generation are heat transfer, activation overpotential and ohmic overpotential in order of magnitude. Furthermore, the high efficiency of EBC compared with other technologies, its broad application space, especially its advantages of integration with energy storage indicate its feasibility and potential.

Entropy generation analysis of magnetized radiative Ellis (Cu-TiO2/Engine Oil) nanofluid flow using Cattaneo-Christov heat flux model with viscous dissipation and Joule heating effects

The most recent research looks into the heat-transferring assets of engine oil based on Ellis nanofluid with MHD effects, which contains nanoparticles of copper (Cu) and Titanium oxide (TiO2). The concert of Copper (Cu) and Titanium oxide (TiO2) was seen in the movement of engine oil. Viscous dissipation, thermal radiation, the Cattaneo-Christov heat flux model, joule heating, and heat generation all change the energy equation. Perviousness, entropy creation, and a horizontally flat moving surface with a non-uniform elongating velocity are all represented mathematically in the model. To locate the numerical explanations of the problem, bvp4c, a convincing numerical technique for solving complex differential equations, is used. The flow and heat transferring facets of Cu-TiO2 in the flow are inspected using the most important parameters. Thermal jump conditions and absorbent media have a momentous impact on flow. It is noted that the temperature and heat transferring rate are reduced as a result of the involvement of important limitations. However, such fluids should be employed in controlled volume as caution in applications requiring heat transfer control. Concluding the recent effort will help in studying engine and generator cooling systems, aircraft refrigeration systems, nuclear cooling system, and other technologies.

Analysis of entropy generation of a chemically reactive nanofluid by using Joule heating effect for the Blasius flow on a curved surface

This aim of the current study is to discuss the flow, heat and mass transfer in the Blasius flow of a nanofluid towards a curved surface. The energy equation is formulated by considering the Joule heating effect along with heat generation. For nanofluid model we have considered the Buongiorno model. In addition, the influence of both homogenous and heterogeneous chemical reaction is also incorporated in the nanoparticle concentration equation. For optimization of energy we have used entropy generation method (EGM). For the mathematical development of the flow problem we have used the curvilinear coordinate system. The developed partial differential equations are reduced into ordinary differential equation by employing suitable similarity transformations and then solved numerically by shooting method along with Runge-Kutta integrating scheme. The validity of the obtained numerical results is also verified by Keller-box method. The impacts of multifarious parameter particularly, magnetic parameter, radius of curvature, thermophoresis parameter, Brownian motion parameter, heat source parameter, Brinkman number and homogenous-heterogeneous parameters on velocity, temperature, concentration, entropy generation and Bejan number are given through graphs and are discussed in detail. Furthermore, skin friction coefficient, Nusselt number and Schmidt number are discussed for various involved parameters in form of tables.

The entropy generation analysis of a pin–fin heatsink with Fe3O4 ferrofluid coolant and considering four different pin–fin shapes (circular, square, rhumbas, and triangular) in the presence of the magnetic field

The entropy generation analysis was performed to determine the viscose and thermal irreversibilities (Ṡfr and Ṡth) inside a pin–fin heatsink under the absence (WO) and presence (W) of the magnetic field considering Res of 200, 300, 400, and 500, four different pin–fin shapes, and Fe3O4 ferrofluid coolant. The results demonstrated that Ṡfr and Ṡth escalates and diminishes, respectively, by increasing Re or by applying the magnetic field effects. For instance, the increase in Re from 200 to 500 escalates Ṡfr by 86% and 80% for 4 configurations and under WO and W scenarios of the magnetic field. Besides, the highest Ṡfr (and lowest Ṡth) was observed for the triangular configuration, which is nearly 12.79% (and 8.36%) and 13.89% (and 11.18%) higher than that for the circular configurations with the lowest Ṡfr (and highest Ṡth) among four configurations at Re = 200. Furthermore, the magnetic field escalates Ṡfr by 41.88%, 37.19%, 37.49%, and 34.06% over the base case without the magnetic field for circular, square, rhumbas, and triangular heatsinks, respectively, at Re = 200. These values diminish to 10.50%, 11.46%, 10.51%, and 7.77% as Re increases from 200 to 500. In addition, Ṡth decreases by 21.98% (or 7.39%), 19.18% (or 6.17%), 20.95% (or 7.15%), and 14.00% (or 3.46%) under the W scenario against the WO scenario for circular, square, rhumbas, and triangular configurations, respectively, at Re of 200 (or 500).

Entropy analysis of peristaltic flow over curved channel under the impact of MHD and convective conditions

The analysis of entropy generation is essential in understanding the irreversibility factor of a system in heat transfer processes, particularly in traditional industrial sectors where heat transmission and fluid fluxes are involved. However, the impact of temperature-dependent viscosity over a curved surface on entropy generation analysis remains unexplored with the consideration of MHD and convective conditions. This study aims to investigate the phenomenon of entropy generation caused by a peristaltic process on a curved surface, considering the impact of MHD, variable viscosity, and convective conditions on the governing system of equations, modeled with the assumption of a long λ and a low Re. To analyze the governing system of equations, proper transformations are employed to produce a transformed system of nonlinear ordinary differential equations, which is then numerically studied to examine the impact of the involved parameters. The shooting approach, using the MATHEMATICA NDSolve, is employed to obtain solutions for the obtained system. The results reveal a decrease in the Bejan number due to an increase in the Brownian parameter. Moreover, the velocity and temperature profiles increase for higher values of the Biot number and magnetic parameter, respectively, with the velocity profile increasing due to magnetic effects near the wall. Overall, this study sheds light on the impact of various parameters on entropy generation in a peristaltic process over a curved surface with temperature-dependent viscosity. The findings can serve as a valuable reference for researchers and practitioners in industrial sectors involved in heat transfer processes and fluid fluxes.

Multi-objective topology optimization and thermal performance of liquid-cooled microchannel heat sinks with pin fins

The optimized structures for the liquid-cooled microchannel heat sinks with different pin-fin arrays were designed via using the topology optimization method for the better performance, including minimization of the flow energy dissipation and the average temperature of the bottom surface, aiming to facilitate the more efficient design of microchannel heat sink for electronic chips’ cooling. The heat transfer and flowing performance was simulated with steady-state incompressible Navier-Stokes equation and the energy equation. Based on the rational approximation of material properties (RAMP) method, the mathematical optimization model for heat sink was established according to the multi-objective function. The Galerkin finite element method (GFEM) was employed to calculate the flow and heat transfer system. Furthermore, the globally convergent method of moving asymptotes (GCMMA) was adopted to deal with the mathematical optimization problem as the optimization method. The entropy generation analysis and comprehensive heat transfer factor were employed to evaluate the performance of the conjugate heat transfer problem of 3D microchannel heat sinks with various pin-fin structures. The calculation results reveal that the multi-objective optimal structure has good heat transfer performance, and the temperature distribution of the optimized structure is more uniform. As the same pumping power, the comprehensive heat transfer efficiency of the optimized inline and staggered pin-fin arrays increases by 31.20% and 32.18% compared to the smooth rectangular channel. Compared with the cylindrical pin-fin configuration with the same heat transfer area, the entropy generation rates of the optimized inline and staggered pin-fin configurations decrease by 4.67% and 4.25%, respectively. The results can provide theoretical basis and application support for the electronic chip cooling technology.

Analysis of entropy generation in a fully wet porous moving longitudinal fin exposed to convection and radiation: homogeneous and functionally graded materials

Analysis of entropy generation in a fully wet porous moving longitudinal fin exposed to convection and radiation: homogeneous and functionally graded materials

Entropy generation in viscous flow due to generalized exponential wall velocity and temperature

The study of entropy generation in convective transport processes is of current interest. For the better understanding of this phenomenon it is preferred to investigate it for those flows which admit an exact solution. This is the reason that majority of the published literature, concerning entropy generation analysis, has been done for the self-similar flows. Particular to the stretching sheet flows, which do also have important applications in industry, entropy production analysis is of particular importance. In this regard a two dimensional boundary layer flow due to an exponentially stretching wall (following generalized exponential form) has been considered in this study for the analysis of entropy generation. The stretching wall velocity and the wall temperature function have so properly been chosen that an similarity solution is possible. The modeled, equations are converted to ordinary differential equations by employing appropriate similarity transformations. These equations are solved numerically by using bvp-4c implemented in Matlab. To implement this method, differential equations are converted to set of first order equations and are solved. The problem has been analyzed for the heat transfer phenomenon and the entropy generation. The dimensionless form of entropy generation number requires m ≡ n for a similarity solution to exist. The enhancement is observed in the Nusselt number by enhancing the values of m, n, and Pr. Eventually, the entropy generation at the wall is maximum for increasing values of and However, for such a large values of of and the entropy profile reduces rapidly in the boundary layer thus avoiding a farther speed of entropy in the boundary layer. It is also noticed that to minimize the entropy generation across the boundary layer and also to get an enhanced rate of heat transfer some higher values of and must be chosen.

Analysis of Entropy Generation for Horizontal Heated Cylinder by Natural Convection and Radiation

Analysis of Entropy Generation for Horizontal Heated Cylinder by Natural Convection and Radiation

Influence of Variable Viscosity on Entropy Generation Analysis Due to Graphene Oxide Nanofluid Flow

Conventional investigations on fluid flows are undertaken with an assumption of constant fluid properties. But in reality, the properties such as viscosity and thermal conductivity vary with temperature. In such cases, considering these variabilities aids in modelling the flows with accuracy. Particularly, studying the flow of graphene based nanofluids with variable properties makes the best of both the advantageous thermophysical properties of graphene nanoparticles in heat transfer and the variable fluid properties in accuartely modelling the flow. In this article, the flow of graphene oxide nanofluid along a linearly stretching cylinder under no-slip and convective boundary conditions is investigated, by taking the base fluid viscosity to be a temperature dependant function. Buongiorno model is adapted to develop the flow of graphene nanofluids including the influence of variable heat source, cross-diffusion effects and the effects of nanoparticle characteristics such as thermophoresis and Brownian motion. The modelled equations are transformed and are numerically solved using linearization method. The impacts of embedded parameters including the Dufour and Soret numbers on temperature, concentration and velocity profiles of the chosen nanofluid and their consequent impacts on the predominant cause for the generated entropy are studied. The obtained results are depicted and interpreted in detail. From the tabulated values of skin friction and the values of Sherwood and Nusselt numbers, it is inferred that the conductive heat and mass transfer can be enhanced by variable viscosity parameter and skin friction can be reduced by Soret number. Furthermore, entropy generation is analysed and Bejan number is calculated to be lesser than 0.5, thus demonstrating the dominance of irreversibilty to fluid friction and mass transfer.

Entropy generation analysis on forced and free convection flow in a vertical porous channel with aligned magnetic field and Navier slip

AbstractThe entropy generation rate in a vertical porous channel with injection and suction walls and a uniform magnetic field provided at an angle to the flow direction is studied using an analytical perturbation technique in the presence of Navier slip and buoyancy force. The momentum and energy equations were solved for exemplary values of fluid convection's physical characteristics. Important parameters' impacts on adequate numbers are graphically portrayed and conveyed.

Numerical studies for effect of geometrical parameters on water jet pump performance via entropy generation analysis

This paper presented an implementation of entropy generation analysis in the main flow field of a water jet pump via the CFD method. This study aimed to identify the inefficient location of energy conversion and to analyse entropy generation sources in each region of the water jet pump. The 2D-axisymmetric model and realisable k-ε (RKE) turbulence model at steady-state conditions were performed to validate jet pump performance and to assess the entropy generation. Likewise, the effects of the projection ratio and throat-aspect ratio as independent parameters were investigated. As a result, the throat is the most inefficient part due to the high total entropy generation rate, following by diffuser part. Also, the entropy generation rate was assessed dominant than viscous dissipation due to the turbulent dissipation, which was caused by a turbulent shear stress layer of mixing the streams. In conclusion, the projection ratio influenced the growth of the shear stress layer as well as the entropy generation. Further, the throat-aspect ratio affected the distribution of entropy generation in the throat section. An appropriate combination of both parameters has an impact on the jet pump performance improvements reducing the entropy generation rate in the future.