Friction Irreversibility Research Articles

Entropy generation in Casson nanofluid flow over a lubricated wall in the presence of induced magnetic field and activation energy

ABSTRACT The research on entropy generation in a mechanical system is quite imperative owing to its immense applications in the production of advanced cooling devices and medical appliances. The basic need on this research is how to optimize the irreversibilities within the systems and channelize that energy towards the benefit. This study elucidates the entropy generation analysis of a Casson nanofluid near a stagnation point over a lubricated vertical wall. A thin film of shear-thinning liquid with power law index of 0.5 is employed on the wall to ensure the lubrication. The effect of induced magnetic field and the chemical reaction stimulated by the activation energy is also incorporated within the flow. The non-linear PDEs of the substantive problem along with the compatible interfacial and boundary conditions are reverted into ODEs with the aid of suitable similarity transformation, and then cracked numerically using the sixth-order Runge Kutta method assisted with Nachtsheim–Swigert shooting practice. One of the significant findings reveals that the fluid friction irreversibilities in the entropy generation are diminished with the magnetic parameter and the Casson parameter, whereas the thermal irreversibility predominates over the total entropy generation for the escalating values of the activation energy parameter.

Numerical illustration using finite difference method for the transient flow through porous microchannel and statistical interpretation of entropy using response surface methodology

The current article discloses the influence of the hyperbolic tangent nanofluid on time dependent flow through a microchannel when a magnetic field is applied. The porous medium was incorporated using the Darcy–Forchheimer model. The chemical reaction is explained by Arrhenius activation energy. Temperature is determined by convective boundary conditions. The irreversibility occurring in the flow is analyzed. The modeled problem gives rise to partial differential equations, which are computed by finite difference method. Response surface methodology, an optimization technique, is used to attain the optimal conditions for entropy generated for the flow of fluid. Results of the analysis reveal that concentration decreases with the rise in reaction rate parameter and increases with activation energy parameter. Prandtl and Eckert numbers, with their increase, enhance entropy, and fluid friction irreversibility is at its highest. Perfect co-relation is attained for the model by the response surface methodology, with a co-relation coefficient of 100 %. The Weissenberg number is highly sensitive to change in the present modeling, followed by Darcy and Reynolds numbers. The Reynolds number and Darcy number show positive sensitivity, while the Weissenberg number shows negative sensitivity to the entropy generated.

Buoyancy-driven nano-suspension subject to interstitial solid/nanofluid heat transfer coefficient: Role of local thermal non-equilibrium (LTNE)

BackgroundBecause of the prominent temperature discrepancy between fluid and solid in porous material, local thermal equilibrium (LTE) is not suitable in case of high-conductivity foams and electronic equipment. In view of above situation, Darcy-Brinkman-Forchheimer model subject to local thermal non-equilibrium (LTNE) is implemented. LTNE technique finds real world applications include groundwater pollution, geothermal extraction, microwave heating, industrial separation process, and transpiration cooling featuring with porous structure. The present study aims at the investigation of the entropy and hydrothermal characteristics of buoyancy-driven TiO2-H2O nanofluid inside a cross-shaped domain embodying two hot and cold rings influenced by LTNE. MethodsFinite element method (FEM) has been considered to solve the dimensionless form of governing equations. Significant findingsAmplification of interstitial solid/nanofluid heat transfer coefficient accounts for the intensification of streamlines, velocities, and diminution of isothermal lines in both nanofluid and solid matrix phases under the influence of LTNE. Strengthening of medium porosity whittles down entropy due to thermal effects in both nanofluid and solid phases, and that ameliorates entropy due to fluid friction and porous medium irreversibilities. Local and average Nusselt numbers in nanofluid phase reduce by 29.31 %, 20.72 %, 17.16 %, and 14.78 % while that in solid phase decays by 13.18 %, 7.63 %, 4.9 %, and 2.8 % for rise in εfrom 0.1 to 0.3, 0.3 to 0.5, 0.5 to 0.7, and 0.7 to 0.9, respectively. Introduction of Darcy-Brinkman-Forchheimer model subject to LTNE yielded better results in hydrothermal behavior of TiO2-H2O nanofluid inside a cross-shaped domain emplacing two hot and cold rings than earlier published results.

ENTROPY-OPTIMIZED FLOW OF COUPLE STRESSES IN AN POROUS INCLINED PIPE WITH UNIFORM MAGNETIC FIELD AND MIXED CONVENTION

Abstract The research aims to investigate the entropy-optimized flow of couple stresses in a porous inclined pipe exposed to a transverse constant magnetic field and mixed convection. It focuses on understanding the thermodynamic efficiency and fluid behaviour under convective boundary conditions, contributing to improved designs in engineering applications where such flows are relevant. The aim is to enhance heat transfer efficiency in industrial processes such as chemical reactors, heat exchangers, and geothermal systems, while also improving filtration systems for applications like water purification and oil recovery. By subjecting the flow to a uniform magnetic field and mixed convection, nonlinear governing equations arise due to mixed convection. We linearize these equations using a quasi-linearization approach and solve them using Chebyshev spectral collocation. Our analysis focuses on thermodynamic phenomena like entropy generation and the Bejan number, which have implications for the efficiency and sustainability of industrial processes. We visualize temperature and axial velocity profiles across various parameter ranges to understand the fluid's behaviour under the influence of magnetic fields and porous materials. As the magnetic parameter increases, there is a decrease in fluid velocity and temperature. However, the opposite tendency is seen for the couple stress viscosity ratio parameter. We also observe irreversibility dominating heat transfer at the pipe wall, while fluid friction irreversibility dominates around the pipe's centre. This research contributes to advancing our understanding of thermodynamic processes in complex fluid systems and has practical implications for optimizing industrial processes and developing more efficient filtration systems.

Influence of graphene nanoplatelets dispersion in food graded heat transfer fluid on the performance of Non-Centrifugal cane sugar unit- a CFD approach

Non-centrifugal cane sugar unitusing food-grade heat transfer oils to make excellent jaggery is an emerging technology. Thermophysical characteristics of such fluids are crucial for improving the system’s efficiency. Graphene nanoplatelets with low weight concentrations are dispersed into Sigma-thermic fluid (STF) to prepare nanofluids which is utilized as heat transfer oils in the NCCS unit. To envisage the potential of these fluids a numerical model is developed by validating the experimental results of STF. Firstly, experiments with STF at 20 lpm, 433 K, were conducted in the NCCS unit, which was fabricated in the laboratory. The results are agreed with the error of 1.14 %; further, the developed numerical model is employed to envisage the potential of STF based graphene nanofluids. Morphological graphene studies are conducted, and nanofluids with different weight concentrations are subsequently prepared. Experimentally measured nanofluid thermophysical characteristics are employed in the numerical model. Simulations are run until the bowl inner surface achieves concentrated sugar cane juice temperature. The effect of inlet temperature and concentration of nanoparticles on the sugar cane juice boiling time, bowl inner surface temperature, heat transfer rate, performance index ratio, thermohydraulic performance, and entropy generation is investigated. The results show that the Nusselt number increases with temperature, and the Nusselt number enhanced by 13.48 %, 22.18 %, and 30.09 % at temperatures of 413 K, 423 K, and 433 K, respectively compared to 403 K temperature for GrS0.3 %. Moreover, heat transfer is enhanced by 22.17 % with GrS0.3 % nanofluid compared to base fluid (STF) in the shortest duration, i.e., 7767 s. As the intake fluid temperature rises from 403 K to 413 K, 423 K, and 433 K, fluid friction irreversibilities are 13 %, 20 %, and 25 %.

Numerical investigation of entropy generation and Magnetohydronamic natural convection in a porous square cavity with four embedded cylinders

In this study, we investigated buoyancy-induced convection in a permeable square hollow containing four embedded cylinders and subjected to a magnetic field using numerical methods. The finite element approach was used to solve the governing equations of the system as well as the initial and boundary conditions. We analyzed the effects of the emerging non-dimensional quantities on the flow pattern and thermal field, as well as entropy production, in relation to the thermophysical properties of the obstacles. In the limiting case, we compared our results with already published work and found outstanding concurrence. Our simulations revealed that increasing cylinder spacing leads to higher thermal entropy generation, while fluid friction irreversibility has the opposite effect. Additionally, the imposed magnetic field significantly suppressed temperature distribution and flow field, resulting in low thermal transmission within the cavity.

Thermodynamic optimization of heat exchanger circuitry via genetic programming

In this study, an evolutionary thermodynamic technique was developed for the optimization of heat exchanger circuitry. The proposed technique is capable of handling the unrestrained implementation of genetic operators while ensuring circuitry feasibility and basic manufacturability. The optimization tool was used to clarify the optimal heat transfer features in relation to the characteristics of the refrigerant and to provide a thermodynamic interpretation of the optimization results to extract general design guidelines. Evaporator circuitry optimization was conducted under given cooling capacity, superheating degree, and boundary conditions representative of air-conditioning applications. The consistency between the minimum entropy generation and the maximum coefficient of performance (COP) was demonstrated under these settings. Accordingly, heat exchanger configurations that take maximum advantage of the thermodynamic benefits of each refrigerant are proposed by optimizing the distribution of friction and heat transfer irreversibility. Consequently, the evaporator outlet pressure increases, thus lowering the compression ratio and maximizing the COP. The developed optimization method maximizes the benefits of low-GWP alternative refrigerants and shows that zeotropic mixtures may exhibit performance analogous to that of R32 and higher than that of R410A by approaching a Lorenz cycle operation.

Entropy generation analysis and thermal synergy efficiency in the T-shaped micro-kenics

In this work, three different twist angles of a micro helical insert in a T-shaped are studied numerically in order to evaluate the laminar steady flow behavior of Newtonian fluid in chaotic geometry. In the geometries under consideration, thermal mixing behavior is carried out using fluids having two distinct input temperatures. Under the influence of chaotic advection and low rates of Reynolds number, the second law of thermodynamics is controlled in terms of the entropy generation caused by hydrodynamic and thermal processes. The governing equations are numerically solved using the CFD Fluent code. Thus, the micromixer's configuration demonstrated a very significant improvement in mixing degree while minimizing friction and thermal irreversibilities. The synergy coefficient, which depicts the link between velocity and heat transfer in angle form, is analyzed and the results are provided.

Numerical investigation of the overall thermal and thermodynamic performance of a high concentration ratio parabolic trough solar collector with a novel modified twisted tape insert using supercritical CO2 as the working fluid

Supercritical CO2 (sCO2) is favoured as the next-generation working fluid for advanced high-temperature and high-concentration ratio parabolic trough solar collectors (PTSC) due to the fluid’s low cost, availability and thermal stability at high temperatures. However, the lower thermal transport properties of sCO2 compared to conventional working fluids necessitate heat transfer enhancement of receivers using sCO2. In this study, a combined and extensively validated approach using Monte-Carlo ray tracing for optical analysis and computational fluid dynamics (CFD) for thermal and thermodynamic analysis were used to investigate the overall thermal and thermodynamic performance of a high concentration ratio sCO2-based PTSC with a modified twisted tape (MTT) inserts in the receiver. MTT inserts with twist ratios in the range of 2.0 to 4.0 and width ratios in the range of 0.75 to 0.95 were investigated. Results show enhancement of the heat transfer performance by up to 73% and thermal efficiency by 6%, and reduction of the receiver heat losses and circumferential temperature gradients when the MTT inserts are used. In addition to presenting results using the first law of thermodynamics, this study also considered the second law of thermodynamics by evaluating the entropy generation rates due to heat transfer and fluid friction irreversibilities. Results showed that the use of MTT inserts caused a reduction in the total entropy generation rates, with the lowest irreversibility occurring at a Reynolds number of 1,650,000 for a twist ratio of 2.0 and width ratio of 0.95.

Irreversibility of Al2O3-Ag hybrid nanoparticles in mixture base fluid on microchannel with variable viscosity, buoyancy forces, and suction/injection effects: An analytical study

The development of inherent irreversibility in the system is caused by single phase Poiseuille flow considering hybrid nanoparticles (Al2O3-Ag) and mixture fluid (water and ethylene glycol H2O50%-C2H6O250%) in the upright microchannel with unequal viscosity. Taking into account the buoyancy force, suction/injection at the walls, and the form factor and geometry of the nanoparticles. The modeling is based on nonlinear PDEs such as continuity, momentum, and heat equations, which are then transformed to a system of nonlinear ODEs using similarity transformations and solved numerically and analytically. The analytical solution was built using the Differential Transform Method (DTM), and the current results in specific cases are compared to results obtained by the HAM-based Mathematica package, the Runge-Kutta Fehlberg 4th-5th order (RKF45), and those available in literature. The effects of active parameters are investigated on the velocity and temperature, entropy generation and Bejan number. The outcomes of the present analysis reveal that the nanoparticles volume fraction, thermal radiation and Biot number acts to enhance the cooling of the system through the release of thermal energy. in addition, the enhancement in variable viscosity parameter, causes a rise in the irreversibility rate, which in turn boosts the rates of entropy generation and Bejan number. On the other hand, Irreversibility due to heat transfer is dominant in the centerline of the microchannel, while fluid friction irreversibility dominates its walls.

The numerical analysis in heat transfer, fluid flow, and irreversibility of a pin-fin heatsink under the ultrasonic vibration with different transducer power assignment scenarios

The hydrothermal performance and entropy generation rate in a pin–fin heatsink were numerically investigated under different vibration transducer power distribution scenarios between 11 transducers located at 3 walls of the heatsink. Two cases were investigated; Case#A and Case#B which are different in 3 transducer locations on one wall of the heatsink. The highest convection coefficient (h) in Case#A was obtained for a variable power scenario, which escalated pressure drop (ΔP) by 91.94%. However, the highest h in Case#B was obtained for the constant power scenario. In addition, h, average temperature of CPU, and thermal resistance factor in Case#A are 5.84% higher than, 0.41% lower than, and 5.34% lower than those in Case#B. The PEC factor for Case#A is higher than unity (1.31) only under the constant power scenario, while the PEC of Case#B is higher than unity under different studied scenarios. Frictional irreversibility (Ṡfr) for Case#A was obtained as 1.45–74.56% higher than that for Case#B due to the swirl flow generated by the high-power transducers and creating the huge velocity gradients in Case#A. Nevertheless, the high flow mixing in Case#A leads to reducing the temperature gradients against Case#B, thereby thermal irreversibility (Ṡth) in Case#A is almost 7.05–19.69% lower than that of Case#B.

Computational investigation of aspect ratio and inclination effects on natural convection heat transfer in nanofluid-filled rough wall cavities

Numerical analysis is performed to deduce the effect of aspect ratio (AR) and inclination of a rough-walled cavity on heat transfer, fluid flow, and entropy generation due to natural convection for Rayleigh number (Ra = 105). The cavity is filled with Al2O3-water nanofluid of 0.05 solid volume fraction. The natural convection process is caused by the temperature difference between the left hot wall and the right cold wall of the cavity. The walls are subjected to slip boundary conditions and the slip velocity is characterized by the Knudsen number (Kn = 0.5). The profile of the rough surface is generated by Weierstrass-Mandelbrot (W-M) function. Numerical simulations have been performed using Finite Element based software COMSOL Multiphysics 6.0. The AR is varied in the range of 0.5 to 4, and the inclination of the cavity is kept at 0°, 30°, and 60°. The numerical results are exhibited in terms of isotherms, streamlines, entropy generation due to heat transfer, and fluid friction irreversibilities. It is observed that the slip velocity on the walls has a strong influence on the fluid flow. Entropy generation due to fluid friction is found to increase with the rise in AR up to 2 and then it starts declining. The entropy generation due to fluid friction irreversibility at the center of the cavity is minimal, so the Bejan number is close to unity. Cavity with an inclination of 30° gives the maximum Nusselt number at any value of AR. Notably, the total entropy generation is observed to reach its maximum at α = 60° and minimum at α = 30°, offering comprehensive insights into the interplay of geometric and flow parameters within the cavity.

Predication of entropy generation rate in a concentrating photovoltaic thermal system with twisted tube turbulator using Boosted regression tree algorithm

Efficient energy conversion and utilization remain paramount in addressing the growing energy demand and environmental concerns. Concentrating photovoltaic thermal (CPVT) systems have emerged as promising solutions by integrating photovoltaic (PV) cells with thermal components for simultaneous electricity and heat generation. In this paper, we propose the application of the Boosted Regression Tree (BRT) algorithm to predict the entropy generation rate in a CPVT system equipped with a perforated twisted tube turbulator. Brief introduction of numerical analysis of local and global rates of frictional (S˙fr) and thermal (S˙th) irreversibilities in a CPVT system equipped with a perforated twisted tube turbulator. The results approve the efficacy of the BRT algorithm in predicting the entropy generation rate. Through comprehensive simulations and data analysis, we establish a predictive model that considers factors such as solar irradiance, fluid flow rate, tube geometry, and turbulator characteristics. The BRT model exhibits remarkable accuracy in capturing the nuanced interplay of these factors, enabling reliable estimations of entropy generation rate.

Outlining the impact of discrete filling of metal foams on thermodynamic performance

The desire of this paper is to present the numerical analysis of thermodynamic performance of high porosity metal foams with discrete filling inside the horizontal pipe. The heater is embedded on the pipe’s circumference and is assigned with known heat input. To enhance heat transfer, aluminum metal foam of 10 PPI (pores per inch) with porosity 0.95 is filled into the pipe. In filling, two kinds of arrangements are made. In the first arrangement, the metal foam is filled adjacent to the inner wall of the pipe (Model (1–3)), and in the second arrangement, the metal foam is located at the center of the pipe (Model (4–6)). So, six different models are inspected for different fluid velocities (0.7–7 m/s) under turbulent flow conditions. Darcy Extended Forchheimer (DEF) is combined with local thermal non-equilibrium (LTNE) models for estimating the flow features and heat transfer via metal foams and initially validated with experimental outcomes. The application of the second law of thermodynamics via metal foams is the novelty of current investigation. In the study, the thermal performance is assessed in terms of heat transfer enhancement ratio and heat transfer performance ratio, and the thermodynamic performance is evaluated based on exergy and irreversibility analysis. In the analysis, the parameters like mean exergy based Nusselt number (Nue), heat transfer and flow frictional irreversibility are considered for the evaluation. The overall thermal performance and exergy transfer found higher in Model (1–3) than the Model (4–6) respectively. The flow and heat transfer irreversibility found less in Model (1–3) than the Model (4–6) respectively. The superior thermodynamic performance is obtained from the metal foam filled cases than from the clear pipe. In that, Model-2 suits the best configuration for designing the thermal system.

Optimizing geometrical structure of a residential parabolic solar collector relying on hydrothermal assessment and second law analysis

Researchers are interested in the optimization of thermal systems due to the rising demand towards renewable and green energy to reduce greenhouse gasses and expenses. To achieve this, the present work aims to conduct the numerical modeling on the residential scale trough solar collector. For this purpose, the lattice Boltzmann method is employed with special treatment for the curved physical boundaries. To enhance the thermal capability of the solar collector, the CuO-water nanofluid is utilized, which its thermal conductivity is estimated using Koo–Kleinstreuer and Li (KKL) model. Furthermore, the Brownian motion effect on the dynamic viscosity is taken into account. In addition, the local and volumetric second law analysis is performed. Besides, the heat line visualization is done to capture the path-line of heat energy within the solar collector. The thermal distribution, flow field, local entropy production (i.e. fluid friction irreversibility and heat transfer irreversibility maps), volumetric entropy generation, Bejan number, and average Nusselt number are the studied items in terms of the governing parameters. The Rayleigh number (103 ≤ Ra ≤ 106), CuO nanoparticle concentration (φ = 0, 0.01, 0.02, 0.03, 0.04) and four structural design of the solar collector (Single-pipe, Double-pipe, Triple-pipe, Quadruple-pipe) are assumed as the governing parameters.

Thermally developing combined electroosmotic and pressure-driven flow of Phan–Thien–Tanner fluids in a microchannel

We present semi-analytical solutions for the hydrodynamically developed and thermally developing flow of a non-Newtonian fluid through an isothermal rectangular microchannel. The fluid motion is actuated by the combined consequences of the electroosmotic and pressure-gradient forces. For the rheological behavior of the non-Newtonian fluid, we have used the simplified Phan–Thien–Tanner viscoelastic model. Going beyond the Debye Hückel linearization approximation, we have used the full-scale solution for the electrical double-layer potential equation to obtain the exact analytical solutions for the velocity, flow rate, and shear rate parameters. In contrast, the temperature distribution and heat transfer for the thermally developing flow have been obtained by solving the energy equation numerically considering the effects of volumetric heat generation due to Joule heating and viscous dissipation. We find that a larger value of the viscoelastic set ε̃Wĩk2 contributes toward the net gain in flow rate. Both the normal and shear stress increase for increasing ε̃Wĩk2, while the shear viscosity reduces with a degree of surface charging. The average shear viscosity reduces with the degree of surface charging and at higher ε̃Wĩk2 values. The heat transfer is enhanced for augmenting ε̃Wĩk2, although the thermal entrance region gets contracted for a pure electroosmotic flow at higher Peclet numbers. Our study reveals that the heat transfer rate can be amplified by effectively modulating the degree of surface charging and ε̃Wĩk2. We have also carried out an entropy generation analysis, which shows the dominance of heat transfer irreversibility over fluid friction irreversibility. We believe that the present research will offer essential approaches for designing advanced energy-efficient microchannels appropriate to modern industrial applications using viscoelastic fluids.

Evolution of Entropy Generation on Mixing Process Using a Novel Chaotic Micromixer

This study aims to compare numerically the laminar steady flow of shear-thinning non Newtonian fluids in novel chaotic micromixer. The process is verified for non-Newtonian flow in a complex geometry that is heated with a constant flux. The selected geometry produce secondary flow structures that greatly improve fluid dynamic performance. To measure this performance, the Poincaré map method is used for various cases of fluid power-law index in different geometries. In addition, thermal mixing behavior is studied for shear-thinning fluids in the chosen geometry with two different inlet temperatures.In different cases of fluid power-law indexes, the novel geometry resulted in an 82% increase in thermal mixing degree relative to the thermal mixing degree observed in the C-shaped and serpentine channels. The second law of thermodynamics is examined in terms of entropy generation caused by thermal and hydrodynamic processes, as a function of low rates of generalized Reynolds number and power-law index, while taking into consideration the effects of chaotic advection. As a result, the new configuration showed a significant improvement in the degree of mixing compared to other geometries considered, while also minimizing friction and thermal irreversibilities.

Effect of a Sinusoidal Temperature Profile on Entropy Generation Due to Double-Diffusive Natural Convection in a Square Partly Porous Cavity

Abstract In this paper, entropy generation due to double-diffusive natural convection inside a partly porous enclosure under sinusoidal wall heating is numerically analyzed. The resulting dimensionless coupled partial differential equations are discretized using the finite volume method (FVM), while the pressure–velocity coupling is handled using the SIMPLE algorithm. To ensure the validity of the results obtained from the in-house FORTRAN code, a comparison is made with previous numerical and experimental works. The results of the study indicate that the dimensionless thickness of the porous layer (Δ), the thermal conductivity ratio (Rk), the angle of inclination of the cavity (α), and the buoyancy ratio (N) are critical factors in determining local distribution and global maximum value of entropy generation due to heat transfer and fluid friction. In contrast, their effect on entropy generation induced by concentration is insignificant, except for the buoyancy ratio parameter, where an enhancement of the global maximum of entropy generation is observed by increasing N. Moreover, it is found that Sψ (max) experiences a sharp decline as Δ varies from 0.2 to 0.8, resulting in a reduction of about 67% for the case with N=10 and 83% for the case with N=1. These results highlight the importance of carefully controlling system parameters to minimize energy losses and maximize system efficiency in heat transfer and fluid flow systems.

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.

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.