Heat Transfer Entropy Generation Research Articles

Local entropy generation optimization and thermodynamic irreversibility analysis of oval-shaped coaxial ground heat exchangers: A detailed numerical investigation

Optimizing the heat transfer and thermodynamic efficiency of Ground Heat Exchangers (GHE) is crucial for maximizing the energy efficiency of Ground-coupled Heat Pump (GCHP) systems utilized in building heating and cooling applications. This study pioneers an effective approach of both the first and second laws of thermodynamics of the newly oval-shaped coaxial GHEs (oval-CGHEs), assessing heat transfer, thermohydraulic performance, and local entropy generation rate to explore the optimum design and operational conditions for heat exchange maximization and entropy generation minimization. Utilizing a three-dimensional numerical model validated by experimental results, this study examines the trade-offs between heat transfer improvements and entropy generation rate intensification of the oval-CGHEs in comparison to the typical circular-shaped CGHE (circle-CGHE) further than exploring the effect of key operational and design parameters and performing sensitivity analysis. The results reveal that oval-CGHEs exhibit higher irreversibility as a penalty for their superior heat transfer capabilities compared to traditional circular-shaped CGHEs (circle-CGHE), which can be mitigated by optimizing the position of the inner tube. Moreover, the study underscores the criticality of maintaining a balance between enhanced heat transfer and the associated rise in irreversibility, particularly concerning the factors of mass flow rates and installation depths.

Heat transfer augmentation and entropy generation minimization by employing synergistic aspects of hybrid (Fe3O4 + MWNTs) nanoliquid in star shaped enclosure with thermally conductive cylinder and inclined magnetic field aspects

This article aims to simulate optimum thermal convection and minimization in entropy generation in viscous hybrid nanofluid (Fe3O4-MWNTs/H2O) flow in thermally cold star shaped enclosure and containing heated cylinder. Shape effect of cylinder in managing associated hydrothermal attributes is also interrogated. Physical aspect of magnetic field making angle of inclination with domain is accounted. Formulation of transport equations is expressed in the form of dimensionless partial differential setup containing the thermophysical relations of induced hybrid nanoparticles. The constructed flow issue has been simulated by using Galerkin finite element method (G-FEM) with appliance of COMSOL Multiphysics®software computer package.Results and grid convergence assessment tests are also executed in the study. Significant impact of flow controlling parameters on velocity, temperature and entropy generation profiles has been presented in graphical and tabular manner. Variation is three different types of entropies namely, viscous, thermal and magnetic are estimated. Quantities of interest like, total entropy, average Nusselt and Bejan numbers are also calculated against the sundry parameters. Ecological coefficient of performance which measures the efficiency of physical systems is interrogated which is important physical quantity in practical problems. It is inferred from the outcomes that induction of hybrid nanoparticles (Fe3O4 − MWCNT) produces considerable augmentation of thermal attributes of base fluid. Moreover, it is depicted that average Nusselt number exceeds up to 26.5 % for star shaped inner cylinder in comparison to the square cylinder. Increment up to 6 % in average Nusselt number and 2.19 % decrease in entropy is depicted when hybrid nanoparticles are added in the base fluid (ϕ≠0) in comparison to the situation when nanoparticles are not induced (ϕ=0).

Numerical investigation on mixed convection for laminar molten salt in horizontal square tubes

Molten salts are the key working media in nuclear and new energy fields. However, the mixed convection of molten salt is rarely investigated. The mixed convection of laminar flow in horizontal square tubes with constant heat flux is analyzed using Fluent software for the first time. The effects of heat flux, inlet temperature and Reynolds number on the flow and heat transfer performances are evaluated. It is found that as the buoyancy force increases, the friction factor, flow entropy generation rate, Nusselt number, and exergy efficiency increase, while the heat transfer entropy generation rate and exergy loss decrease. Compared to the forced convection, the maximum local friction factor, flow entropy generation rate, mean Nusselt number and mean exergy efficiency for mixed convection increase by 25.8%, 50.5%, 109.0% and 7.6%, respectively. Moreover, the maximum mean heat transfer entropy generation rate and exergy loss decrease by 56.1% and 57.3%, respectively. In addition, approximately 42% of the friction factor predicted by Fluent and 30% of the heat transfer predicted by Fluent exceed 20.0% uncertainties of conventional correlations. Therefore, an accurate friction factor correlation with 12.9% uncertainty and an accurate heat transfer correlation with 9.1% uncertainty are proposed.

Expression of Concern: Numerical study of entropy generation in the convection heat transfer of nanofluid inside a tilted closed compartment with five constant-temperature heat sources in the presence of a magnetic field

Expression of Concern: Numerical study of entropy generation in the convection heat transfer of nanofluid inside a tilted closed compartment with five constant-temperature heat sources in the presence of a magnetic field

Computational analysis of entropy generation minimization and heat transfer enhancement in magnetohydrodynamic oscillatory flow of ferrofluids

Improvements in heat transfer rate and entropy generation minimisation are critical issues in many engineering and industrial applications where efficient heat transfer is essential to achieve optimal performance and lower energy consumption. This study investigates the entropy generation of the mixed convection flow of ferrofluids in the presence of viscous and Joule dissipation. The flow is oscillatory and induced by the sinusoidal oscillations of a flat plate in its plane. Two Newtonian fluids, namely, kerosene oil C12H26C15H32 and methanol CH3OH are considered base fluids containing magnetite Fe3O4 nanoparticles. Governing equations are first modelled by employing the fundamental laws of transport phenomena. Then, using scaling analysis, these equations are transformed into a dimensionless system of partial differential equations. Numerical simulations are performed using the Gear-Generalized Differential Quadrature Method (GGDQM), and the model is validated with special cases from the literature. It has been found through numerical analysis that the convergence of GGDQM can be guaranteed by using only a small number of grid points. The thermal boundary layer of methanol-based nanofluid is thicker than that of kerosene. It has been observed that the skin friction coefficient increases for both categories of nanofluids as the values of the Eckert number, solid volume fraction, and Grashof number increase. The Nusselt number increases as the solid volume fraction increases, while the opposite trend is observed when the values of the Hartman, Eckert, and Grashof numbers rise. With increasing values of the Grashof number, the rise in the velocity of methanol-based nanofluids is higher than that of kerosene oil-based nanofluids. The maximum percentage difference between the velocities is identified to be 22.2177% at Gr=4.0. The temperature of methanol-based nanofluids rises more quickly than that of kerosene oil-based nanofluids with increasing values of the Grashof number. It is determined that the largest percentage difference between the temperatures is 20.5968% at Gr=4.0. When Ec=0, the percentage difference between velocities is 29. 1721 %, while the percentage difference between temperatures is 78.7155%. Compared to methanol-based ferrofluid, the volumetric entropy production is more extensive in kerosene-based ferrofluid. On the other hand, in comparison to a kerosene-based nanofluid, thermal irreversibility predominates in a methanol-based nanofluid. The novelty of this study lies in the computational treatment of coupled partial differential equations (momentum and energy) that incorporate buoyancy force, Joule heating and viscous dissipation effects, complementing the underlying physics and mathematical modelling of the research problem.

Heat transfer and surface roughness analysis via peristaltic pumping of viscous fluids through diverging tube

Peristalsis is natural pumping mechanism which is propelling the natural fluids through physiological systems, and it’s important to note that surfaces are rarely perfectly smooth in these contexts. Surface roughness is key factor of the most of the surfaces/medium which affects the fluid flow and heat transfer through surface/medium. This study is primarily concerned with investigating the impact of surface roughness and heat transfer through peristaltic pumping of viscous fluids through a divergent tube. The governing equations used in this study are based on the suitable assumption for physiological transport, i.e. low Reynolds numbers and long wavelengths. To understand the physical behaviors related to velocity, pressure difference, stream function, heat transfer rates, entropy generation and isotherms with different levels of surface roughness, an analytical approach followed by the MATLAB coding has been adopted and graphical results have been illustrated. It is revealed that surface roughness reduces the fluid velocity however the entropy generation increases with high surface roughness. This research contributes to better understanding of fluid dynamics and heat transfer within biological organisms and has significant implications for a wide range of industrial and medical applications.

Entropy generation for thermo-magnetic fractional order convective flow in complex porous enclosures: a numerical study

PurposeThis study aims to analyze the impact of fractional derivatives on heat transfer and entropy generation during transient free convection inside various complex porous enclosures, such as triangle, L-shape and square-containing wavy surfaces. These porous enclosures are saturated with Cu-water nanofluid and subjected to the influence of a uniform magnetic field.Design/methodology/approachIn the present study, Darcy’s model is used for the momentum transport equation in the porous matrix. Additionally, the Caputo time fractional derivative is introduced in the energy equation to assess the heat transfer phenomenon. Furthermore, the total entropy generation has been computed by combining the entropy generation due to fluid friction (Sff), heat transfer (Sht) and magnetic field (Smf). The complete mathematical model is further simulated using the penalty finite element method, and the Caputo time derivative term is approximated using the L1 scheme. The study is conducted for various ranges of the Rayleigh number (102≤Ra≤104), Hartmann number (0≤Ha≤20) and fractional order parameter (0<α<1) with respect to time.FindingsIt has been observed that the fractional order parameter α governs the characteristics of entropy generation and heat transfer within the selected range of parameters. The Bejan number associated with heat transfer (Beht), fluid friction (Beff) and magnetic field (Bemf) further demonstrate the dominance of flow irreversibilities. It becomes evident that the initial evolution state of streamlines, isotherms and local entropy varies according to the choice of α. Additionally, increasing Ra values from 102 to 104 shows that the heat transfer rate increases by 123.8% for a square wavy enclosure, 7.4% for a triangle enclosure and 69.6% for an L-shape enclosure. Moreover, an increase in the value of Ha leads to a reduction in heat transfer rates and entropy generation. In this case, Bemf→1 shows the dominance of the magnetic field irreversibility in the total entropy generation.Practical implicationsRecently, fractional-order models have been widely used to express numerous physical phenomena, such as anomalous diffusion and dispersion in complex viscoelastic porous media. These models offer a more accurate representation of physical reality that classical models fail to capture; this is why they find a broad range of applications in science and engineering.Originality/valueThe fractional derivative model is used to illustrate the flow pattern, heat transfer and entropy-generating characteristics under the influence of a magnetic field. Furthermore, to the best of the author’s knowledge, a fractional-derivative-based mathematical model for the entropy generation phenomenon in complex porous enclosures has not been previously developed or studied.

Numerical study on the heat transfer performance evaluation, flow characteristics, exergy efficiency, and entropy generation analysis of a novel coaxial geothermal heat exchanger

In order to improve the geothermal heating capacity of buildings, this paper proposes a coaxial geothermal heat exchanger (CGHE) with an inner tube assembled with continuous spiral fins (CSF). The thermal performance and flow characteristics of a CGHE with inner tubes assembled with different widths of CSF were numerically investigated at different rotational directions and rotational speeds (rpm = −30, −60, −90, −120, 30, 60, 90 and 120). The heat transfer mechanism in different rotational directions and rotational speeds was revealed and the heat transfer performance 、exergy efficiency and entropy generation were analyzed. The results of the study showed that the assembly of different width CSF on the inner tube of the CGHE exhibited completely different thermal performance and flow characteristics in the case of clockwise and counterclockwise rotation. Nu decreases in clockwise rotation and increases in counterclockwise rotation, but with small changes. The f of each H is always greater than the static f when rotating clockwise, and each width f increases as the clockwise rotation speed increases. And the f of each H in counterclockwise rotation is opposite to that in clockwise rotation. The PEC of each H decreases as the clockwise rotation speed increases and increases as the counterclockwise rotation speed increases, with a maximum PEC = 1.813 for H = 11 mm and rpm = 120. And counterclockwise rotation can improve the exergy efficiency of CGHE. The entropy generation rate is significantly higher than that of smooth tubes when Re exceeds 12,639.

Entropy optimization and stability analysis in flow of quadratic radiative Ag−MgO/water hybrid micropolar nanofluid over an exponentially contracting permeable Riga surface

ABSTRACT Driven by the significant thermal relevance of low-conductivity electrically active fluids and their impact on controlling flows across multiple industrial and engineering domains, this study aims to thoroughly investigate the primary behavior of electro-magneto-non-Newtonian micropolar A g − M g O / H 2 O hybridized nanofluid, specifically focusing on its flow dynamics and heat transfer characteristics over an exponentially contracting porous Riga surface. The Riga surface, an exceptional electromagnetic sensor surface, holds potential applications in micro-coolers, submarines, and nuclear reactor heat management systems. These findings hold significant relevance due to the prevalent use of micropolar hybridized nanofluids in cooling minute electronic components such as microchips and associated equipment. Our innovative objective is to emphasize the influence of an electromagnetic Riga plate in conjunction with micropolar characteristics, quadratic thermal radiant energy, convective conditions, and velocity slip at the boundary on various key parameters. These parameters include the coefficient of shear stress, coefficient of couple-stress, heat transfer factor (Nusselt number), entropy generation, velocity distribution, micro-rotation or angular velocity, and temperature profiles. We successfully tackled the highly intricate coupled partial differential equations by employing numerical techniques within the MATLAB programming platform. Specifically, we utilized a fourth-order method known as bvp4c to address the challenging boundary value problem. The outcomes revealed the existence of dual solutions characterized by a stable upper solution branch and an unstable lower solution branch within the region of the contracting sheet. Notably, this observation occurred under specific conditions related to the mass suction parameter. The identification of critical values in cases with dual solutions prompted a subsequent stability analysis to discern the nature and characteristics of these solutions. Two distinct solutions have been identified for λ S < λ , reaching termination at λ = λ S within the contracting region. Notably, the first solution yields a positive minimum eigenvalue ( β 1 > 0 ), indicating its stability, while the second solution results in a nonpositive eigenvalue ( β 1 < 0 ), implying instability. Graphical representations illustrate a substantial enhancement in nanofluid temperature for both solution branches, notably influenced by the quadratic thermal radiating parameter, Eckert number, and Biot number. Moreover, the magnetic interaction number and velocity slip parameter notably affect nanofluid motion within the first solution branch. Interestingly, it has been observed that the shear stress and couple stress coefficients exhibit an upward trend with increasing suction value. However, the heat transfer factor (Nusselt number) might decrease in the case of a stable solution. This research direction aims to optimize nanofluid compositions, aiming to minimize entropy generation while maximizing desired thermal properties. Such endeavors are crucial steps towards fostering more efficient and sustainable industrial practices, aligning with the overarching objectives of enhancing energy utilization and promoting industrial growth.

Peristalsis of Carreau–Yasuda nanofluid possessing variable thermal conductivity regulated by electroosmosis via an expanding asymmetric channel

Peristalsis of non-Newtonian nanofluid via a non-uniform conduit has several applications in physiology and industry. This study proposes a mathematical model as well as exploration of the impacts of entropy generation for peristalsis of magneto nanofluid with temperature-dependent thermal conductivity via an expanding asymmetric channel. Buongiorno’s model for study of nanofluid flow has been adopted. Rheological aspects are accounted using the Carreau–Yasuda model due to its experimentally validated significance. Impacts of applied electric and magnetic fields have been taken into account. Thermophoresis, ohmic heating, viscous heating and Brownian motion effects are incorporated in the model. Numerical method is used via NDSolve in Mathematica after implementing the lubrication approach and Debye–Huckel linearization. The effects of embedded parameters on the flow, heat transfer, entropy generation and Bejan number are studied using graphical depictions. Outcomes indicate that a rise in electroosmotic parameter enhances heat transfer rate, whereas it reduces entropy generation and mass transfer rate at the boundary. Therefore, this study can provide basics to study nanofluidic systems which has applications in drug delivery. Increasing trends for temperature, heat transfer rate and entropy generation, while declining trends in the concentration of the particles are noted for higher joule heating.

Hybrid-nanofluid magneto-convective flow and porous media contribution to entropy generation

PurposeThis paper aims to present a numerical study that investigates the flow of MgO-Al2O3/water hybrid nanofluid inside a porous elliptical-shaped cavity, in which we aim to examine the performance of this thermal system when exposed to a magnetic field via heat transfer features and entropy generation.Design/methodology/approachThe configuration consists of the hybrid nanofluid out layered by a cold ellipse while it surrounds a non-square heated obstacle; the thermal structure is under the influence of a horizontal magnetic field. This problem is implemented in COMSOL multiphysics, which solves the related equations described by the “Darcy-Forchheimer-Brinkman” model through the finite element method.FindingsThe results illustrated as streamlines, isotherms and average Nusselt number, along with the entropy production, are given as functions of: the volume fraction, and shape factor to assess the behaviour of the properties of the nanoparticles. Darcy number and porosity to designate the impact of the porous features of the enclosure, and finally the strength of the magnetic induction described as Hartmann number. The outcomes show the increased pattern of the thermal and dynamical behaviour of the hybrid nanofluid when augmenting the concentration, shape factor, porosity and Darcy number; however, it also engenders increased formations of irreversibilities in the system that were revealed to enhance with the permeability and the great properties of the nanofluid. Nevertheless, this thermal enhanced pattern is shown to degrade with strong Hartmann values, which also reduced both thermal and viscous entropies. Therefore, it is advised to minimize the magnetic influence to promote better heat exchange.Originality/valueThe investigation of irreversibilities in nanofluids heat transfer is an important topic of research with practical implications for the design and optimization of heat transfer systems. The study’s findings can help improve the performance and efficiency of these systems, as well as contribute to the development of sustainable energy technologies. The study also offers an intriguing approach that evaluates entropy growth in this unusual configuration with several parameters, which has the potential to transform our understanding of complicated fluid dynamics and thermodynamic processes, and at the end obtain the best thermal configuration possible.

Maximizing heat transfer and minimizing entropy generation in concentric cylinders with CuO[sbnd]MgO[sbnd]TiO2 nanoparticles

Heat transfer is crucial because it has industrial uses. A novel type of nanofluids dubbed “ternary nanofluid” is being utilized to boost the ability of conventional fluids to transmit heat since it has a greater heat transfer capacity than solo and hybrid nanofluids. This work investigates the heat transfer capabilities and entropy generation in the cylindrical flow of a ternary nanofluid in the presence of a magnetic field. Minimizing the entropy generation and maximizing the heat transfer of a fluid using ternary nanoparticles (CuOMgOTiO2) is the aim of this work. The finite difference method is used by the MATLAB computer program to solve the problem numerically. The results reveal that the entropy generation minimizes in the presence of CuOMgOTiO2. The heat transfer rate of the fluid increased by 9.9%, 10.8%, and 11.2% on adding TiO2, MgOTiO2, and CuOMgOTiO2 nanoparticles, respectively.

Thermohydraulic and Irreversibility Analyses of Swirl Flows Utilizing Distorted Radial Fins: Entropy Generation and Entransy Dissipation Evaluation

The current investigation analyses the convective heat transfer performance, entropy generation, and entransy evaluation of swirl flows generated by distorted radial fins (DRF). As swirl flows and various vortical structures induce large temperature gradients, second law and entransy analyses are necessary to thoroughly evaluate their true thermodynamic influence on heat transfer enhancement. The results indicated that due to the influence of swirl flows and vortices, all angles of the DRF were capable of inducing intense fluid mixing, thinner thermal boundary layers, and turbulent eddies. It was found that overaggressive swirl flows may hinder local heat transfer performances, by enclosing low-velocity heated fluids within the thermal boundary layers. However, as these overaggressive swirl flows and strong vortices propagate downstream, beneficial fluid mixing was eventuated, favouring heat transport over large regions. In terms of thermal performances, the maximum heat transfer enhancement was exhibited by the α=45° DRF, improving the Nusselt numbers up to 59.3%. Accordingly, the highest performance evaluation criterion (PEC) of 1.269 was obtained by the α=45° DRF at the Reynolds number 2389, attributed to the centrifugal effects of the swirl flows. Optimal entropy generation numbers were also exhibited by the α=45° DRF at the highest studied Reynolds number, reducing total entropy generation by 36.81%. Lower entransy thermal resistances were also accredited to greater DRF angles due to the intense swirl effects. In essence, the study concludes that the effects of swirl flows and vortices significantly enhance heat transfer, whilst reducing both entropy generation and entransy dissipation rates, leading to optimal thermal performances.

Numerical Analysis of the Unsteady Mixed Convection of a Nanofluid in a Concentric Tube Heat Exchanger

In the present work, a numerical investigation of the unsteady mixed convection and entropy generation of a nanofluid in an annular cylindrical space is presented using the Buongiorno’s two-phase flow model. It deals with a concentric tube heat exchanger where the inner cylinder rotates with a constant frequency and is maintained at hot temperature, while the outer cylinder is cold. The aim of the present investigation is to highlight the effects of some parameters on the hydrodynamic, thermal and mass behavior of the considered nanofluid as well as on the system irreversibility, namely: the inertia (1 ⩽ Re ⩽ 20), the buoyancy (0 ⩽ Ri ⩽ 5), the mass diffusion (0.1 ⩽ Le ⩽ 10) and the vertical positions of the inner cylinder (-0.4 ⩽ H ⩽ 0.4). Moreover, at specific parameters, an optimal position in terms of heat transfer has been determined. The flow of the nanofluid is two-dimensional and governed by the equations of continuity, momentum, energy as well as volume fraction conservation. After performing a finite element method mesh test and validation with the literature, the Nusselt number and the entropy generation are discussed. The results show that the heat transfer rate and entropy generation increase with increasing values of Richardson and Reynolds number, especially when positioning the inner cylinder in the lower part. On the other hand, the nanoparticles migration under the thermophoretic diffusion decrease with the increase of the Lewis number, which consequent decrease of the heat transfer rate.

Significance of dust particles volume fraction to optimization of entropy in magnetohydrodynamic mixed convection flow via inclined surface

The main purpose of this study is to assessment the rate of entropy generation in magneto-hydrodynamic free convection with flow through the boundary layers of a fluid that is viscous and dusty fluid flow subject to dispersed dust particles across the stretching surface. Dusty fluids are utilized in a wide range of construction and manufacturing sectors, included the transportation of petroleum, gas purification, auto exhaust fumes, power station piping, sedimentation process, and many more. The primary objective of this elaborated fluid problem is to observe the influence of dust particles volume fraction on the heat transfer rate and entropy generation. By using appropriate similarity transformation, for first fluid phase and second dust phase simulations, the governing partial differential equations are transfigured into nonlinear non-dimensional ordinary differential equations. The final forms of obtained equations are solved numerically via MATLAB built-in bvp4c solver scheme. When the scientific validity of the findings is analyzed, it is found that there is substantial agreement among the latest results and the existing research. The entropy generation and thermal performance in fluid is influenced by the growing volume fraction of dust particles and significance variation is noted. As volume fraction of dust particles increased, causes a decrease in fluid flow, and reduced the velocity of both fluid and dusty fluid phases. But, it plays remarkable improvement in fluid temperature and entropy generation, and cause a decline in Bejan number. In fluid phase and dust fluid phase, temperatures are increased while inclined angle fluid parameter strength increases while the fluid velocity is decreased. Additionally, dimensionless variable expressions for Bejan number (Be) and entropy generation (Ns) are produced. It is noticed how several physical attributes influence entropy generation values.

Heat transfer performance and entropy generation analysis of Taylor–Couette flow with helical slit wall

The turbulent flow between concentric cylinders and its heat transfer performance is studied by the large eddy simulation. The models with longitudinal slit and helical slit spacing in the range from 168 to 672 mm on the outer cylinder are investigated to compare their heat transfer ability. Further, the notion of field synergy and entropy formation serves as the foundation for evaluating heat transfer qualities. According to the results, the enhancement effect of helical slits on heat transfer is better than that of longitudinal slits. Helical slits are more effective in promoting fluid mixing at different temperatures within the annulus. In terms of field synergy, the helical slit models exhibit a smaller field synergy angle compared to the longitudinal slit model at various Reynolds numbers from 3061 to 4592. Results of using helical slits indicate an improved coordination between the velocity and temperature fields. Thermodynamic analysis reveals that the helical slit models have lower entropy generation as compared to the longitudinal slit models. Higher efficiency in energy utilization and superior heat transfer properties of the helical slit models are noticed. Findings of this study provide valuable insights for the optimal design of various rotating machinery applications.

The Impacts of Various Base Fluids and Nanofluids on Heat Transfer Enhancement and Entropy Generation in a Rotating Microchannel

The Impacts of Various Base Fluids and Nanofluids on Heat Transfer Enhancement and Entropy Generation in a Rotating Microchannel

Entropy generation and exergy loss of R123-MWCNTs nanorefrigerant in flow condensation

This experimental study examines the entropy generation due to heat transfer and frictional pressure and the exergy destruction during the condensation of an R123-MWCNTs nano-refrigerant within a horizontal tube. The effects of entropy production, Bejan number, and exergy loss are studied, together with the roles played by vapour quality, mass flux, and multi-wall carbon nanotubes (MWCNTs) concentration. The results show that the heat transfer entropy generation reduces as the vapour quality or mass flux and concentration of MWCNTs rises. In contrast, the entropy production due to frictional pressure during condensation increases with the rise in mass flux, vapour quality, and the MWCNTs fractions. The reductions in heat transfer entropy generation are high compared to the increment in frictional entropy generation, thus reducing the total entropy generation of the system. Further, nanofluid minimizes the system's Bejan number and exergy loss. The highest reduction in entropy generation and exergy loss of about 30 % and 29 %, respectively, was observed using the proposed nanofluid at a MWCNTs fraction of 0.1 % and mass velocity of 400 kg/m2s.

Entropy generation analysis on heat transfer characteristics of Twisted corrugated spiral heat exchanger utilized in solar pond

In the present study, heat transfer and entropy generation in the spiral corrugated heat exchanger used in the solar pond have been numerically studied. The thermal boundary condition of the third type has been selected for simulation and different geometric parameters have been studied to improve heat transfer and reduce entropy generation. New correlations based on experimental data have been used to validate the simulation. The results were obtained by changing the parameters such as the number of corrugations, the twist number of the corrugations, and the change of the Reynolds number. Also, dimensionless parameters have been defined to investigate the increase of heat transfer and decrease of entropy generation based on the first and second laws of thermodynamics, and finally, the optimal geometries have been introduced by the NH multi-criteria parameter. The simulation results showed that the corrugation creation on the tube will increase heat transfer and decrease entropy generation. Therefore, it was found that the twist number of the corrugation has a greater effect than the number of corrugations. In the best case, when the number of corrugations and their twist is high, the heat transfer improvement number (NH) can grow up to 89%, which will decrease with the increase of Reynolds number.

On Entropy Generation and Heat Transfer Due to Magneto-Marangoni Convective γ Al2O3-H2O/C2H6O2 Nanofluid Flow Over a Porous Surface

A numerical analysis is carried out for water/Ethylene Glycol based γ Al2O3 nanofluid movement over a horizontal permeable sheet placed within a porous medium using MATLAB package Bvp4c solver. Other flow controlling conditions like Non-linear thermal radiation and uniform Magnetic field are also considered for this study. The present study is novel in terms of entropy generation and heat transfer rate investigation for mentioned fluid system in the existence of dissipation (an irreversible process) and heat generation/absorption impact. First, a mathematical pattern is prepared in the form of partial differential equations to represent the Marangoni convection flow and temperature, considering suitable boundary conditions. Using similarity parameters, we convert our mathematical model in dimensionless form and then solved it. Accuracy of obtained data is also cross-checked with another numerical technique “Runge-Kutta fourth order” along with shooting process. Using velocity and temperature fields, entropy is measured for present system. From the plots, it is noted that entropy as well as Bejan number is qualitatively changed for parameters namely, volume fraction parameter, radiation parameter, Brinkmann number and heat generation/absorption parameter. It is noticed that heat transfer rate and entropy generation number is higher for γ Al2O3-C2H6O2 nano fluid then γ Al2O3-H2O nano fluid.