Entropy Transfer Research Articles

Entropy and radiative heat transfer analysis in water-based nanofluid flow with Catteneo-Christov heat flux

Entropy and radiative heat transfer analysis in water-based nanofluid flow with Catteneo-Christov heat flux

Effects of sinusoidal wall temperature on thermal dynamics and irreversibility around an inclined plate embedded in a square cavity

Abstract Effective thermal and flow control within complex geometries is essential for engineering applications. In this study, an in-depth examination of flow dynamics, entropy, and thermal regulation is undertaken within a square cavity featuring sinusoidal wall temperature. To introduce complexity, an inclined plate obstacle is strategically positioned within the cavity with an inclination angle of 45o, and the investigation spans three distinct scenarios: adiabatic, cold, and hot conditions. The initial physical model is developed by formulating a system of partial differential equations, which are then transformed into a dimensionless representation using relevant variables. Subsequently, the Galerkin method is employed for approximated analysis of the simplified fluid flow model, and the computational code is verified in tabular format. The embedded physical parameters are constrained to specific numerical values to ensure the convergence of the physical model in each scenario. The physical characteristics of isotherms, streamlines, Nusselt numbers, entropy, and Bejan numbers are investigated. Notably, the results demonstrate that the introduction of a cold inclined plate leads to peak values in generating the entropy and average heat transfer rates. When comparing the cold inclined plate to the heated inclined plate, an increase of approximately 20% in the average heat transfer rate and a 15% rise in the entropy generation rate was found for the cold inclined plate. Furthermore, the Bejan number showed a 10% decrease for the cold inclined plate compared to the heated inclined plate. Additionally, increasing the amplitude and wavenumber led to a rise in average heat transfer and entropy generation rates, with 25% and 30% increases, respectively.

Optimization of entropy and heat transfer in a magnetohydrodynamic marangoni convection flow of biviscosity bingham hybrid nanofluid through convergent channel

This study examines the entropy generation and heat transfer performance in a Jeffrey-Hamel flow of biviscosity Bingham fluid with the addition of Al2O3 and Cu nanomaterials in the presence of a thermal Marangoni convective process. An emerging Jeffrey-Hamel problem is extended with the implementation of the Bingham fluid stress tensor in a Naiver Stokes equation. The governing equations with Marangoni boundary conditions due to surface tension are solved computationally utilizing the Keller-Box methodology. The findings demonstrate the complex interplay of entropy production processes, fluid-solid interfaces, and thermal Marangoni convection. Findings demonstrated that increasing Marangoni, Bingham parameters, and thermal radiation enhances the rate of heat transmission. The influence of the Marangoni and Bingham parameters on skin friction is conflicting in a narrow channel. System entropy and flow field uplift with a higher Marangoni convection parameter. Increasing the Reynolds number significantly increases the drag force, whereas the effect of the magnetic variable is the reverse. Velocity is an increasing function of the Reynolds and Bingham parameters and deteriorates with the load of nanomaterials. Temperature is a rising function of nanomaterial load, Eckert, and Bingham parameter. The results of this investigation have important ramifications for improving heat transfer, coolant systems, and nozzles design.

An investigation of heat transfer and optimization of entropy in bio-convective flow of Eyring-Powell nanomaterial with gyrotactic microorganisms

Entropy generation in nanofluid flows is a critical parameter that influences the performance, efficiency, and sustainability of thermal systems. Understanding and optimizing entropy creation can lead to noteworthy advancements in numerous engineering applications, from renewable energy systems to industrial processes and biomedical equipments. The purpose of this article is to examine the entropy produced in the bioconvection flow of Eyring-Powell nanomaterial with gyrotactic microorganisms. The mathematical equations representing the flow are modeled considering the flow towards a porous surface of a cylinder. Together with the effects of the governing parameters, the mass and heat transfer components of the problem are discussed. The thermal effects of different natures are used in a new way. Overall, entropy creation is designed with regard to the second law of thermodynamics. Activation energy, chemical reaction, thermal radiation, and internal friction force effects are accounted for the development of the mathematical model. Coupled non-linear dimensional equations have been altered into ordinary differential equations (ODEs) and then treated using the MATLAB Finite Difference Method (FDM). Consequence of diverse sundry parameters on entropy production, thermal field, mass concentration profile, Bejan quantity, and motile density of microorganisms is deliberated via plots. Through tables, engineering quantities are analyzed. According to the findings, the velocity profile rises as the curvature and Eyring-Powell fluid parameters rise, while it falls when the magnetic parameter is enhanced. Additionally, it is noted that as the curvature variable enhances, the rate of heat transfer and skin friction coefficient decays.

A transient formulation of entropy and heat transfer coefficients of Newton's cooling law with the unifying entropy potential difference in compressible flows

The original Newton's law of cooling is considered an ideal convection model of a point source ignoring conduction, but its unknown convection conductance and inconsistent thermal potential difference make it difficult to further elucidate the transient heat transfer mechanism of convection because of the no-slip condition at the interface between a body and a fluid. For this purpose, both the convective entropy transfer theory and the hypothesis of the isothermal velocity sublayer are developed to recast Newton's law of cooling into a standard Ohm's law form via the unified entropy driving force and the unambiguous entropy transfer coefficient. An explicit expression for the transient heat transfer coefficient is presented theoretically and experimentally in compressible flows by virtue of the product of the free-stream velocity, the volumetric thermal capacity of the fluid, and the near-wall velocity constant. The unified thermal potential difference is established between the body temperature and the total temperature (reduced to the ambient temperature for incompressible fluids). The physical mechanism of convection mode in the original Newton's cooling law is reasonably explained by the entropy transfer theory and entropy transfer efficiency, and the formulae for the entropy flux vector driven by the standard entropy potential difference and the rate of entropy generation are obtained. The analytical heat transfer coefficients as well as the standard thermal driving forces are validated by comparison with the forced convection experiment with a maximum error of 4.6 % in incompressible flows and the previous Newton's benchmark cooling experiments with the maximum error of 6.7 % in compressible flows. The effects of radiation on the total heat transfer coefficient are also analyzed quantitatively.

Coherent Transfer of Lattice Entropy via Extreme Nonlinear Phononics in Metal Halide Perovskites

Entropy transfer in metal halide perovskites, characterized by significant lattice anharmonicity and low stiffness, underlies the remarkable properties observed in their optoelectronic applications, ranging from solar cells to lasers. The conventional view of this transfer involves stochastic processes occurring within a thermal bath of phonons, where the lattice arrangement and energy flow from higher- to lower-frequency modes. Here, we unveil a comprehensive chronological sequence detailing a conceptually distinct coherent transfer of entropy in a prototypical perovskite CH3NH3Pbl3. The terahertz periodic modulation imposes vibrational coherence into electronic states, leading to the emergence of mixed (vibronic) quantum beat between approximately 3 and 0.3 THz. We highlight a well-structured bidirectional time-frequency transfer of these diverse phonon modes, each developing at different times and transitioning from high to low frequencies from 3 to 0.3 THz, before reversing direction and ascending to around 0.8 THz. First-principles molecular dynamics simulations disentangle a complex web of coherent-phononic coupling pathways and identify the salient roles of the initial modes in shaping entropy evolution at later stages. Capitalizing on coherent entropy transfer and dynamic anharmonicity presents a compelling opportunity to exceed the fundamental thermodynamic (Shockley-Queisser) limit of photoconversion efficiency and to pioneer novel optoelectronic functionalities. Published by the American Physical Society 2024

Entropy transfer efficiency-effectiveness method for heat exchangers, part 1: Local entropy generation number and operation performance limits

Here, to resolve the open problem of the second-law efficiency evaluation for heat exchangers, an efficiency-effectiveness method is developed from pure convection theory, where the entropy transfer efficiency defined as the outlet temperature ratio of cold and hot fluids exchanging entropy and local entropy generation number can measure the global and local irreversibilities of heat transfer. The efficiency and effectiveness are related by the inlet temperature ratio τ and capacity rate ratio φ, and their maxima subject to the local entropy generation number are determined for different flow arrangements. When τ = φ2, the effectiveness maxima are 0.5/(1 + φ) and 1/(1 + φ) while the highest efficiencies are φ and unity for parallelflow and counterflow arrangements, respectively. The optimum operating points of counterflow exchangers, at which the equal outlet temperature τT1∞ (T1∞ represents the hot inlet temperature) of two fluids with a critical capacity rate ratio τ induces uniform irreversibility, the effectiveness limit of 1/(1+τ), and the efficiency limit of unity, are obtained. A linear temperature difference method is also developed based on the redefined convective and overall heat transfer coefficients, invariably yielding an effectiveness equal to the number of heat transfer units. This method has potentials to be extended to wet heat exchangers with phase-change flows.

Entropy and melting heat transfer assessment of tangent hyperbolic fluid flowing over a rotating disk

Entropy and melting heat transfer assessment of tangent hyperbolic fluid flowing over a rotating disk

Fundamental heat and entropy transfer mechanisms of convection underlying the first and second laws for an unsteady multiport system and their applications in parallel flow heat exchangers

Although thermal convection is ubiquitous in nature and technology, it has long been argued whether convection can be considered as an independent mode of heat transfer. Here, we show that pure convection mode is generally recognized from the classical first and second laws via mass flow by rooting the unsteady mass conservation relation through an equivalent multiport system. The fundamental distinction is made between convection driven by the thermal and entropy potential differences and mass flow accompanied by zero potential difference. The constitutive relations of the convective heat and entropy fluxes and their thermodynamic relationship are developed in terms of their potential differences with the exponential distribution of temperature difference in a compressible flow. In the absence of work transfer, the first and second laws are simply expressed by the standard Maxwell’s electromagnetic type equations via the total heat and entropy flux vectors. The pure convection theory is applied to a parallel-flow heat exchanger and the linear temperature difference distribution is obtained for both streams via the first-law definitions of the convective and overall heat transfer coefficients in an internal flow. The entropy generation rate inside a heat exchanger is recalculated and indicated to be driven by the difference between the reciprocal of outlet temperatures of two streams, from which the entropy generation number between outlets is developed to eliminate the entropy generation paradox. The present linear temperature difference profiles agree well with the experimental data, and the outlet entropy generation number is also justified by comparing with the previous nondimensionalizing entropy generation numbers.

Hunting WIMPs with LISA: correlating dark matter and gravitational wave signals

The thermal freeze-out mechanism in its classical form is tightly connected to physics beyond the Standard Model around the electroweak scale, which has been the target of enormous experimental efforts. In this work we study a dark matter model in which freeze-out is triggered by a strong first-order phase transition in a dark sector, and show that this phase transition must also happen close to the electroweak scale, i.e. in the temperature range relevant for gravitational wave searches with the LISA mission. Specifically, we consider the spontaneous breaking of a U(1)′ gauge symmetry through the vacuum expectation value of a scalar field, which generates the mass of a fermionic dark matter candidate that subsequently annihilates into dark Higgs and gauge bosons. In this set-up the peak frequency of the gravitational wave background is tightly correlated with the dark matter relic abundance, and imposing the observed value for the latter implies that the former must lie in the milli-Hertz range. A peculiar feature of our set-up is that the dark sector is not necessarily in thermal equilibrium with the Standard Model during the phase transition, and hence the temperatures of the two sectors evolve independently. Nevertheless, the requirement that the universe does not enter an extended period of matter domination after the phase transition, which would strongly dilute any gravitational wave signal, places a lower bound on the portal coupling that governs the entropy transfer between the two sectors. As a result, the predictions for the peak frequency of gravitational waves in the LISA band are robust, while the amplitude can change depending on the initial dark sector temperature.

Entropy and energy transfer analysis of a Maxwell thin‐film fluid over an inclined surface with viscous dissipation effect

AbstractNon‐Newtonian fluid plays a vital role in the field of manufacturing and engineering sector, because of its immense heat transfer rate. The two‐dimensional incompressible unsteady Maxwell nanofluid thin‐film flow with MHD and viscous dissipation over an inclined surface is investigated. One of the mechanisms in the second law of thermodynamics, that is irreversibility which also analyzed. The Maxwell nanofluid thin film energy and motion equations in the additional information have been turned into a coupled differential system of the third order. The transformed ODE equations are further evaluated by using the Homotopy Analysis Method (HAM). The variations of entropy rate, velocity, Bejan number and temperature field with the various emerging parameters are analyzed. This could potentially lead to the development of solar energy systems that are both affordable and highly efficient, so enabling the more efficient use of renewable energy sources and reducing our dependence on fossil fuels.

Relativistic electron ([formula omitted]) flux driving parameters over geostationary orbit using 30 years of data

The relativistic electron population at MeV energy in the Earth’s outer radiation belt at geostationary (GOE) orbit largely varies in association with solar wind disturbances. Although more researches have been done to understand the influence of different mechanisms that cause the variations in the relativistic electron flux in the region, but still the underlying physics is often complex and unclear. The present study uses relativistic electron (E>2MeV) fluxes data of Los Alamos National Laboratory (LANL) geosynchronous satellites to understand the variations and its relationship with the driving parameters. The study examines the relativistic electron fluxes variations associated with the interplanetary magnetic field (IMF) and solar wind parameters using daily averaged data from 01 January 1990 to 31 December 2018. The results indicated that the information transfer from solar wind and IMF parameters into relativistic electrons flux is dependent on the kind of driving parameter. The result identifies the rank of driving parameters based on their maximum values in the cross correlation and information transfer analysis. Thus, AE index and vsw are the dominant driving parameters for the dynamics of relativistic electrons flux at GEO orbit. The peak values of coefficient (correlation coefficients, mutual information and entropy transfer) are observed at similar lag times (τpeak). For instance, in the case of AE and Je, we have observed the maximum coefficient (associated with lag time) as follows; maximum correlation coefficient; CCmax=0.846(5days), maximum mutual information; MImax=0.803(5days), maximum transfer entropy; TEmax=0.892(5days). Such dependency analysis can help to select the model parameters that influence the relativistic electrons fluxes and improve the existed models of the dynamical system.

Persistence of Basal Ganglia Oscillatory Activity During Tremor Attenuation by Movement in Parkinson's Disease Patients.

One of the characteristics of parkinsonian tremor is that its amplitude decreases with movement. Current models suggest an interaction between basal ganglia (BG) and cerebello-thalamo-cortical circuits in parkinsonian tremor pathophysiology. We aimed to correlate central oscillation in the BG with electromyographic activity during re-emergent tremor in order to detect changes in BG oscillatory activity when tremor is attenuated by movement. We performed a prospective, observational study on consecutive parkinsonian patients who underwent deep brain stimulation surgery and presented re-emergent tremor. Coherence analysis between subthalamic nucleus/globus pallidus internus (STN/GPi) tremorous activity measured by microrecording (MER) and electromyogram (EMG) from flexor and extensor wrist muscles during rest, posture, and re-emergent tremor pause was performed during surgery. The statistical significance level of the MER-EMG coherence was determined using surrogate data analysis, and the directionality of information transfer between BG and muscle was performed using entropy transfer analysis. We analyzed 148 MERs with tremor-like activity from 6 patients which were evaluated against the simultaneous EMGs, resulting in 296 correlations. Of these, 26 presented a significant level of coherence at tremor frequency, throughout rest and posture, with a complete EMG stop in between. During the pause, all recordings showed sustained MER peaks at tremor frequency (±1.5 Hz). Information flows preferentially from BG to muscle during rest and posture, with a loss of directionality during the pause. Our results suggest that oscillatory activity in STN/GPi functionally linked to tremor sustains firing frequency during re-emergent tremor pause, thus suggesting no direct role of the BG circuit on tremor attenuation due to voluntary movements. © 2024 International Parkinson and Movement Disorder Society.

Comparative characterization of entropy and heat transfer in carbon-based magnetohydrodynamic Cross nanofluids flowing through PTSCs: advancing thermal applications for solar-powered aircraft

ABSTRACT The integration of solar energy into aero-technology has emerged as a pivotal solution to meet the escalating energy demands of contemporary societies. This study explores the potential of solar power in aerospace, aiming to reduce carbon dioxide emissions, diminish reliance on environmentally harmful energy sources, and enhance overall industry energy efficiency. The investigation focuses on the integration of solar energy into aero-technology using parabolic trough solar collectors (PTSCs) embedded in aircraft. Particularly, the study delves into the flow and thermal aspects of ethylene glycol magnetohydrodynamic (MHD) Cross nanofluids, in combination with three distinct carbon-based nanoparticles – namely graphene, multi-walled carbon nanotubes (MWCNTs), and single-walled Carbon NanoTubes (SWCNTs) – within the PTSC, which are situated in various sections of the aircraft. Evaluating heat efficiency and heat transfer involves considering various physical phenomena. The results reveal significant enhancements, as observed in the magnetohydrodynamic flow of Cross nanofluids incorporating graphene, MWCNTs, and SWCNTs, where we demonstrate relative increases in maximum heat performance by 35.1009%, 49.9765%, and 67.6678%, respectively. Additionally, the absolute value of the skin friction coefficient showed respective relative increases of 65.2767%, 58.31438%, and 66.4392%. Furthermore, the heat transfer exhibited respective relative increases of 58.3686%, 51.3771%, and 43.0085%.

Entropy and heat transfer analysis of magnetic hybrid nanofluid inside a porous square cavity with thermal radiation

Entropy and heat transfer analysis of magnetic hybrid nanofluid inside a porous square cavity with thermal radiation

Entropy and Memory Aware Active Transfer Learning in Smart Sensing Systems

Entropy and Memory Aware Active Transfer Learning in Smart Sensing Systems

Numerical study for trihybrid nanomaterial flow by convectively heated curved sheet

Trihybrid nanofluid has vast applications including cooling systems, heat exchangers, electronic chips, automobile radiators, slurries, and biomedicine. Flow of MHD hybrid nanomaterial by convectively heated surface with entropy formulation is explored. The trihybrid nanofluid model is composed of three distinct nano-sized particles along with base material. Here 2 % of ferric oxide (Fe3O4), 2 % of silver (Ag) and 2 % of copper (Cu) nanoparticles are taken with ethylene glycol (C2H6O2) as base fluid. Nonlinear differential system is constructed. Adequate transformation is employed in order to compute the problem numerically by applying the finite difference method. When compared to regular fluid, nanofluid and hybrid fluid, the trihybrid nanofluid exhibits superior thermal properties. It is perceived that adding nanoparticles in traditional fluids improve the ability to transmit heat. The temperature field and velocity are shown visually in relation to a number of emerging parameters. The coefficient of skin friction, Bejan number and rates of entropy and heat transfer have been explored physically. The results revealed that with magnetic effects the velocity field reduces while temperature improves when volume fraction for trihybrid nanoparticles is taken as 2 %. Moreover, the Bejan number is also improved by altering the radiation parameter. Excellent agreement is found when current numerical results for curved surfaces are compared to previous published literature for regular flat surface for large K.

Numerical analysis of heat and mass transfer of MHD natural convection flow in a cavity with effects of source and sink

The study of fluid flow and heat transport is found in many engineering applications such as boilers, nuclear plants, thermal energy storage, and underground pipelines. This study focuses on investigating the effects of isothermal source and sink on natural convection and entropy generation for Casson fluids using the finite element method. Under these considerations, fins ensure the effectiveness of heat transfer systems and flow patterns. Results describe that a higher Ra value leads to promote heat and mass transfer while Ha has the opposite impact. By increasing Ha value, results to retard convective heat transfer. As the Lewis number increases, so does the entropy due to deformation and the Bejan number. The shape optimization study about fins is performed in detail. The aspect ratio of cold fins is varied from 1.25 to 7, found that length and width are nearly directly related to entropy, mass, and heat transfer rates. The correlation coefficient for mean Nusselt and Sherwood number versus sink width is 0.9942, very close to 1, showing a very close direct relationship. The linear regression coefficients for mean Nusselt, Sherwood number and total entropy versus sink lengths are (0.7484, 2.2343), (0.7706, 2.254) and (2.4927, 5.8662), respectively.

Tracking the multifield dynamics with cosmological data: a Monte Carlo approach

We introduce a numerical method specifically designed for investigating generic multifield models of inflation where a number of scalar fields ϕ K are minimally coupled to gravity and live in a field space with a non-trivial metric 𝒢> IJ (ϕ K ). Our algorithm consists of three main parts. Firstly, we solve the field equations through the entire inflationary period, deriving predictions for observable quantities such as the spectrum of scalar perturbations, primordial gravitational waves, and isocurvature modes. We also incorporate the transfer matrix formalism to track the behavior of adiabatic and isocurvature modes on super-horizon scales and the transfer of entropy to scalar modes after the horizon crossing. Secondly, we interface our algorithm with Boltzmann integrator codes to compute the subsequent full cosmology, including the cosmic microwave background anisotropies and polarization angular power spectra. Finally, we develop a novel sampling algorithm able to efficiently explore a large volume of the parameter space and identify a sub-region where theoretical predictions agree with observations. In this way, sampling over the initial conditions of the fields and the free parameters of the models, we enable Monte Carlo analysis of multifield scenarios. We test all the features of our approach by analyzing a specific model and deriving constraints on its free parameters. Our methodology provides a robust framework for studying multifield inflation, opening new avenues for future research in the field.

A general theory to estimate Information transfer in nonlinear systems

A general theory for computing information transfers in nonlinear stochastic systems driven by deterministic forcings and additive and/or multiplicative noises, is presented, satisfying quite general boundary conditions in the state-space: either closed, periodic or satisfying a vanishing probability density function. It extends the Liang-Kleeman (LK) framework of causality inference to nonlinear cases based on information transfer across system variables, which is presented in detail in (Liang, 2016. Information flow and causality as rigorous notions ab initio. Phys. Rev. E, 94: 052201. DOI: 10.1103/PhysRevE.94.052201). We present an effective method of computing formulas of the rates of Shannon entropy transfer (RETs) between selected causal and consequential variables, the ‘Causal Sensitivity Method’ (CSM), relying on the estimation from data of conditional expectations of the system forcings and their derivatives. Those expectations are approximated by nonlinear differentiable regressions, leading to a much easier and more robust way of computing RETs than the ‘brute-force’ approach which calls for the computation of numerical integrals over the state-space and the knowledge of the multivariate probability density function of the system. The CSM is furthermore fully adapted to the case where no model equations are available, starting with a nonlinear model fitting from data of the consequential variables, with the subsequent application of CSM to the fitted model. RETs are decomposed into deterministic and stochastic components, being compensated by the self generation of entropy in ergodic conditions. Moreover, RETs are decomposed into sums of single one-to-one RETs plus synergetic terms (of pure nonlinear nature) accounting for the joint causal effect of groups of variables. State-dependent (or specific) RET formulas are also introduced, puting in evidence where in state-space the entropy transfers and local synergies are more relevant. A comparison of the RETs estimations is performed between: 1) the ‘brute-force’, expensive (taken as benchmark), probability-density-based approach (AN), 2) the CSM-based approach with and/or without model fitting, and 3) the multivariate linear (ML) approach, in the context of two different models: (i) a model derived from a potential function and (ii) the classical chaotic Lorenz system, both forced by additive and/or multiplicative noises. The analysis demonstrates that the CSM estimations are robust, cheaper, and less data-demanding than the AN-reference values in the different experiments, providing evidence of the possibilities and generalizations offered by the method (e.g. causality diagnostics between subspaces) and opening new perspectives on real-world applications.