Entropy Production Research Articles

Probing SUSY at gravitational wave observatories

Under the assumption that the recent pulsar timing array evidence for a stochastic gravitational wave (GW) background at nanohertz frequencies is generated by metastable cosmic strings, we analyze the potential of present and future GW observatories for probing the change of particle degrees of freedom caused, e.g., by a supersymmetric (SUSY) extension of the Standard Model (SM). We find that signs of the characteristic doubling of degrees of freedom predicted by SUSY could be detected at Einstein Telescope and Cosmic Explorer even if the masses of the SUSY partner particles are as high as about 104 TeV, far above the reach of any currently envisioned particle collider. We also discuss the detection prospects for the case that some entropy production, e.g. from a late decaying modulus field inducing a temporary matter domination phase in the evolution of the universe, somewhat dilutes the GW spectrum, delaying discovery of the stochastic GW background at LIGO-Virgo-KAGRA. In our analysis we focus on SUSY, but any theory beyond the SM predicting a significant increase of particle degrees of freedom could be probed this way.

Velocity slip and temperature jump effects on entropy generation of MHD second-grade hybrid nanofluid in Jeffery-Hamel flow

PurposeThis paper aims to model and analyze Jeffery Hamel’s channel flow with the magnetohydrodynamics second-grade hybrid nanofluid. Considering the importance of studying the velocity slip and temperature jump in the boundary conditions of the flow, which leads to results close to reality, this paper intends to analyze the mentioned topic in the convergent and divergent channels that have significant applications.Design/methodology/approachThe examination is conducted on a EG-H_2 O <30%–70%> base fluid that contains hybrid nanoparticles (i.e. SWCNT-MWCNT). To ensure comprehensive results, this study also considers the effects of thermal radiation, thermal sink/source, rotating convergent-divergent channels and magnetic fields. Initially, the governing equations are formulated in cylindrical coordinates and then simplified to ordinary differential equations through appropriate transformations. These equations are solved using the Explicit Runge–Kutta numerical method, and the results are compared with previous studies for validation.FindingsAfter the validation, the effect of the governing parameters on the temperature and velocity of the second-grade hybrid nanofluid has been investigated by means of various and comprehensive contours. In the following, the issue of entropy generation and its related graphical results for this problem is presented. The mentioned contours and graphs accurately display the influence of problem parameters, including velocity slip and temperature jump. Besides, when thermal radiation is introduced (Rd = +0.1 and Rd = +0.2), entropy generation in convergent-divergent channels decreases by 7% and 14%, respectively, compared to conditions without thermal radiation (Rd = 0). Conversely, increasing the thermal sink/source from 0 to 4 leads to an 8% increase in entropy generation at Q = 2 and a 17% increase at Q = 4 in both types of channels. The details of the analysis of contours and the entropy generation results are fully mentioned in the body of the paper.Originality/valueThere are many studies on convergent and divergent channels, but this study comprehensively investigates the effects of velocity slip and temperature jump and certainly, this geometry with the specifications presented in this paper has not been explored before. Among the other distinctive features of this paper compared to previous works, the authors can mention the presentation of velocity and temperature results in the form of contours, which makes the physical analysis of the problem simpler.

Enhanced Thermal Study in Hybrid Nanofluid Flow through a Channel Motivated by Water/Cu+Al2o3 and Entropy Generation

This study examines the analysis of entropy generation in the magnetohydrodynamic oscillatory convective flow of hybrid nanofluid through a porous horizontal channel with velocity slip. The analysis incorporates suction at the cold wall and injection at the hot wall. Variable viscosity, thermal radiation, and viscous dissipation are also considered. Utilizing similarity transformations, the governing nonlinear partial differential equations are converted into ordinary differential equations, and exact solutions are obtained using Mathematica. Graphs are used to illustrate the impact that a variety of physical factors have on velocity, temperature, entropy generation, the Bejan number, skin friction, and the Nusselt number. The graphic results demonstrate that the fluid velocity is positively correlated with the cold wall slip parameter and negatively correlated with the hot wall slip parameter. There is an opposite relationship between fluid temperature and thermal radiation and an ascending relationship between fluid temperature and the Brinkman number. Findings from this study have important implications for better thermal management, device performance, and reliability as well as for optimizing microelectronic cooling systems.

Numerical assessment of hydrothermal and entropy generation characteristics of graphene quantum dots nanofluid in a microchannel heat sink incorporating secondary channels and ribs

Efficient heat dissipation from electronic chips is essential for enhancing their performance and longevity. Significant progress has been achieved through the introduction of nanofluids and microchannel heat sinks. However, there is still a need for nanofluids that demonstrate exceptional thermal properties and stability. Graphene quantum dots nanofluid, an innovative carbon-based coolant with zero-dimensional nanostructures, presents promising features such as excellent chemical stability, surfactant-free preparation, superior thermal properties, and minimal impact on rheological characteristics. This study explores, for the first time, the hydrothermal behavior and entropy generation of graphene quantum dots nanofluid in a microchannel heat sink comprising secondary flow channels and ribs. To this end, a three-dimensional conjugate heat transfer model is built using ANSYS Fluent software, and the governing equations are solved using the finite volume method. The simulations are carried out considering temperature-dependent thermophysical properties under different concentrations ranging from 0 to 0.5 % and Reynolds numbers ranging from 100 to 500. The results reveal that the maximum bottom wall surface temperature decreases by 5.88 K, while the heat transfer coefficient improves by 24.9 % compared to the base fluid. Moreover, the total entropy generation reduces by 14.7 %. On the other hand, the pressure drop increases by 43 %. Overall, the highest increment in Performance Evaluation Criteria is 10.8 % at a Reynolds number of 100 and a concentration of 0.5 %, making this particular condition suitable for practical applications.

Numerical exploration of the entropy generation in tri-hybrid nanofluid flow across a curved stretching surface subject to exponential heat source/sink

Numerical exploration of the entropy generation in tri-hybrid nanofluid flow across a curved stretching surface subject to exponential heat source/sink

A Thermodynamic Study on Information Power in Communication Systems.

Modern information theory pioneered by Shannon provides the mathematical foundation of information transmission and compression. However, the physical (and especially the energetic) nature of the information has been elusive. While the processing of information incurs inevitable energy dissipation, it is possible for communication systems to harness information to perform useful work. In this article, we prove that the thermodynamic cost (that is, the entropy production of the communication system) is at least equal to the information transmitted. Based on this result, a model of a communication heat engine is proposed, which can extract work from the heat bath by utilizing the transmission of information. The communication heat engine integrates the manipulation of both energy and information so that both information and power may be transmitted in parallel. The information transmission rate and the information power of the communication heat engine are derived from a pure thermodynamics argument. We find that the information power of the communication heat engine can be increased by increasing the number of communication channels, but the absolute energy efficiency of the heat engine first increases and then decreases after the number of channels of the system exceeds a threshold. The proposed model and definitions provide a new way to think of a classical communication system from a thermodynamic perspective.

Investigation of performance and entropy generation rate of Direct Contact Membrane Distillation (DCMD) with Static Mixer (SM): 3D CFD study

This study investigated the performance of Direct Contact Membrane Distillation (DCMD) with a Static Mixer (DCMDSM) and compared it to conventional DCMD using 3D Computational Fluid Dynamics (CFD) under steady-state conditions. The permeate flux and total entropy generation rate (TEGR) were explored as functions of various parameters, including temperature differences between feed and permeate flow, inlet velocity, salt mass fraction, membrane porosity, membrane thermal conductivity, and membrane pore radius. The study revealed that the maximum permeate flux of DCMDSM was 79 % higher than DCMD. Additionally, the average TEGR of DCMDSM was 67 % lower than that of DCMD. Furthermore, increasing the inlet velocity led to higher permeate flux in both DCMD and DCMDSM. The results showed that the performance of the DCMDSM at lower velocities was better than at higher inlet velocities. Moreover, increasing the temperature difference between feed and permeate, salt mole fraction, and porosity showed similar effects on permeate flux for both DCMD and DCMDSM, with the permeate flux of DCMDSM consistently exhibiting 60 % higher permeate flux than DCMD across all parameter ranges. Finally, the analysis of membrane thermal conductivity indicated that higher thermal conductivity of the membrane resulted in better permeate flux for DCMDSM than DCMD. Additionally, the TEGR analysis revealed that it was minimized at lower temperature differences, higher inlet velocities, and lower membrane thermal conductivities for both DCMD and DCMDSM.

A novel balanced teaching-learning-based optimization algorithm for optimal design of high efficiency plate-fin heat exchanger

Plate-fin heat exchangers (PFHE) are crucial for engineering applications. Pursuing high performance in PFHE design through optimal methods is common, yet challenging for traditional optimization approaches. Meta-heuristic algorithms (MAs) continuously achieve significant breakthroughs in this problem. This paper proposes a novel balanced teaching-learning-based optimization (NBTLBO) algorithm for PFHE optimal design, which optimizes entropy generation units and heat transfer area using objective functions derived from thermal modeling. NBTLBO introduces two phases, as straightforward as that of TLBO, that collaborate to balance exploitation and exploration, offering substantial superiority over TLBO. This addresses the limitations of existing TLBO studies that involve complex multiple phases and neglect phase interactions. The experiments reveal that NBTLBO achieves the best ranking in CEC 2014 and 2020 benchmarks compared with many popular MAs and even their enhanced variants. It also yields the best results across all four PFHE design examples, showing significant improvement over TLBO and other existing methods. A non-dominated sorting NBTLBO algorithm is developed for multi-objective PFHE design, achieving improved Pareto results compared to existing methods. It verifies that NBTLBO, despite its simplicity akin to TLBO, effectively balances exploitation and exploration, thereby achieving notably enhanced performance, rendering it a preferred option for tackling global optimization challenges.

Thermodynamically Ideal Quantum State Inputs to Any Device

We investigate and ascertain the ideal inputs to any finite-time physical process. We demonstrate that the expectation values of entropy flow, heat, and work can all be determined via Hermitian observables of the initial state. These Hermitian operators encapsulate the breadth of behavior and the ideal inputs for common thermodynamic objectives. We show how to construct these Hermitian operators from measurements of thermodynamic output from a finite number of effectively arbitrary inputs. The behavior of a small number of test inputs thus determines the full range of thermodynamic behavior from all inputs. For any process, entropy flow, heat, and work can all be extremized by pure input states—eigenstates of the respective operators. In contrast, the input states that minimize entropy production or maximize the change in free energy are nonpure mixed states obtained from the operators as the solution of a convex-optimization problem. To attain these, we provide an easily implementable gradient-descent method on the manifold of density matrices, where an analytic solution yields a valid direction of descent at each iterative step. Ideal inputs within a limited domain, and their associated thermodynamic operators, are obtained with less effort. This allows analysis of ideal thermodynamic inputs within quantum subspaces of infinite-dimensional quantum systems; it also allows analysis of ideal inputs in the classical limit. Our examples illustrate the diversity of “ideal” inputs: distinct initial states minimize entropy production, extremize the change in free energy, and maximize work extraction. Published by the American Physical Society 2024

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 %.

Exploration of melting heat transfer and entropy generation in a magnetized hybrid nanoliquid over an extending sheet of varying thickness

The analysis of melting heat transfer over an expansive sheet of variable thickness is of the utmost importance in various industrial and engineering sectors, such as injection molding of polymers and composites, cooling of nuclear reactors, hot rolling, etc. Thus, the current work examines the flow dynamics, melting heat transport, and entropy generation of a magneto-hybrid nanofluid over a stretching device with variable thickness in porous media. A water-based hybridized nanofluid is formed using copper (Cu) and aluminium oxide (Al2O3) nanoparticles in the presence of thermal radiation, viscous dissipation, and Joulean heating. The transport partial derivatives were transmuted to ordinary derivatives using appropriate similarity quantities. These equations were numerically solved through shooting techniques combined with the Runge–Kutta–Fehlberg (RKF) method. Diverse figures and tables are sketched to illustrate the outcomes of the various parameters involved in the study. The investigation reveals an enlargement in the heat-bounding surface with an escalation in the magnitude of volume fraction, melting heat transfer, and magnetic field terms. In contrast, the momentum-bounding surface depletes with these parameters. Furthermore, as thermal radiation and Eckert numbers rise, the thermal gradient increases. The entropy generation increases with higher Brikman number and porosity term, but the melting heat parameter causes a decline in the entropy profiles.

A peristaltic motion for pressure driven flow of Casson nanoliquid along with gyrotactic microorganisms in an entropic porous channel: A numerical study

Pump designs can be optimized for maximum energy efficiency, reduced waste, and enhanced overall performance by taking entropy factors into account. In this regard, the current investigation concentrates on examination of thermodynamic analysis for bio-convection peristaltic phenomenon of a non-Newtonian Casson nanofluid in an asymmetrical elastic channel by considering the generation of entropy. The pressure driven flow is managed by using lubrication approach and converting the system in to laboratory (wave) frame. The resulting findings of physical expressions together with the surface conditions are tackled by shooting numerical algorithm on conventional software Mathematica with the help of built-in tool (NDSolve). Graphical attitude of numerous physical quantities (entropy generation, Bejan number, and velocity profile, density of gyrotactic motile microorganisms and nanoparticles volume fraction) is also added and the results are equated with the existing literature. After detailed discussion on graphical display, it is concluded that with porosity of the medium helps to get the entropy generation reduced while, with the increase in bio-convection Peclet value, the micro-organisms’ density declines. The results of the study can be of great significance in the fields of nanotechnology, bio-microsystems and Bio-nano cooling phenomenon.

Entropy analysis of Darcy-Forchheimer flow of Reiner-Rivlin A12O3–Cu/engine oil based hybrid nanofluid between two rotating disks

This paper analyzes the flow of the Reiner-Rivlin hybrid nanofluid, considering the magnetic field and varying thermal conductivity between two spinning disks. Appropriate similarity variables are used to transform all dimensional equations into dimensionless form. A semi-analytical homotopy analysis approach applied to solve dimensionless equations and velocity profiles, temperature distribution, Nusselt number, skin friction, entropy generation, and Bejan number are presented graphically. Some key outcomes include that axial and tangential velocities decreases when porosity parameters increase. Additionally, higher Eckert number when varying from 1 to 1.3, increases the temperature near the center of the two disks from 1.02 to 1.18. The heat transfer rate goes up from 10.2767 to 10.3043 when thermal conductivity rises from 0.1 to 0.7. The entropy generation grows in proportion to the Brinkman number, Reynolds number, and the porosity parameter values. This research might enhance cooling, lubrication, and thermal management in automotive, aerospace, and biomedical industries.

Entropy generation in mixed convection rotating flow over a heated surface

This work aims to study entropy generation in mixed convection flow of Newtonian viscous fluid. Water and kerosene oil we can take as counter examples in this case. This fluid flows past a vertical plate. This fluid near the wall is heated with isothermal heating. The plate moves with constant acceleration and the fluid flows in a rotating fame. Mixed convection is considered here due to buoyancy force and constant plate linear translation. This problem is modeled in terms of partial differential equations (PDEs) and then using suitable variables, the problem is transformed into dimensionless form. Exact solutions of the problem are attained using the Laplace transform. The equations for Bejan number and entropy generation are also developed in dimensionless form, and then by via the exact solutions of velocity and energy, the results of entropy generation and Bejan number are figured. Graphical results are provided to discuss about the behavior of embedded parameters. Results of Nusselt number and skin friction are also figured in tabular form and discussed.

Development of ternary hybrid nanofluid for a viscous Casson fluid flow through an inclined micro-porous channel with Rosseland nonlinear thermal radiation

ABSTRACT The current problem is concerned with the investigation of Casson ternary hybrid nanofluid flow through microchannel. Nanofluids containing three distinct kinds of nanoparticles have a lot of industrial and engineering applications as a result of their amazing thermal properties. The nanoparticles (alumina A l 2 O 3 , titanium oxide Ti O 2 , and copper oxide CuO ) are immersed in base fluid (ethylene glycol C 2 H 6 O 2 ) resulting in ternary hybrid nanofluid ( A l 2 O 3 + Ti O 2 + CuO / C 2 H 6 O 2 ). For the problem under consideration, the momentum distribution, temperature distribution, entropy generation, and Bejan number have been examined. With the aid of tables and graphs, comparisons of ternary hybrid, binary hybrid, and mono nanofluids have also been investigated. With nondimensional variables, the governing equations are transformed into a dimensionless form and solved using the Chebyshev Collocation Method (CCM). Analysis shows that the increment in Reynolds number, Brinkmann number, and exponential heat source parameter results in an enhancement in the dimensionless temperature and the variational improvement of the thermal radiation parameter reduces the thermal distribution. Hence, the findings show that ternary hybrid nanofluids perform better in terms of thermal conductivity performance than either binary hybrid or mono nanofluids.

Structure optimization of intercooler bionic fins based on artificial neural network and genetic algorithms

The bionic fins inspired by the shark are proposed to enhance the thermal-hydraulic performance of the intercoolers in this work. The geometric parameters of the fins are investigated to examine the effects on thermal-hydraulic performance. The height and width of protrusions are chosen as optimization parameters based on the results of the geometric parameter analysis. Non-dominated genetic algorithms are combined with artificial neural networks to obtain the optimal solution for the geometry parameters. The artificial neural networks used in this study exhibit a reliable accuracy with errors below 10 % (with mostly remaining below 5 %). The optimal values for the height and width of the protrusions are determined to be 1.01 mm and 0.82 mm, which results in a Colburn factor of 0.01923 and a comprehensive index of 0.04305. Compared with the original design, the optimized structure yields 17.69 % and 4.77 % increments for the Colburn factor and comprehensive index. Compared with the original model, the intercooler with the optimal structure exhibits a 9.9 % increase in entropy generation and a 20.2 % enhancement in the exergy difference between the inlet and outlet.

Numerical analysis of fluid flow and heat transfer characteristics in single crystal diamond microchannels with ribs and secondary channels

To meet the heat dissipation requirements of high-frequency and high-power electronic devices, single crystal diamond microchannels (SCD-MC) with secondary channels and rib combinations are proposed. The fluid flow and heat transfer characteristics in SCD-MC with various secondary channels and rectangular rib combinations are investigated through numerical simulations. The comprehensive performance and energy saving effect of the microchannel were evaluated by analyzing the factor of merit and entropy generation performance. The results show that the SCD-MC with secondary channels and rib combinations enhance fluid disturbance and increase the solid–liquid contact area, significantly improving heat transfer. When Reynolds number (Re) is 586, compared with the straight microchannel, the average temperature at the bottom of the SCD-MC with rectangular secondary channels and rectangular rib (Case 5) is reduced by 4.8 K, the heat transfer coefficient is increased by 209.8 %, and the factor of merit is improved by 89.2 %. The entropy generation augmentation number of the Case 5 microchannel was the minimum of 0.52, which has the highest energy saving effect. The factor of merit of the Case 5 microchannel exhibits a tendency to first increase and then decrease with the increase of the relative width of the secondary channel (Ψ), the relative width of the rib (Φ), and the relative position of the rib (Π). At Re = 586, Ψ = 0.933, Φ = 0.667, and Π = 0.5, the factor of merit of the Case 5 microchannel is 2.08, indicating the highest comprehensive performance. This finding provides new ideas and methods for the design and application of microchannel thermal management.

Thermo-fluidic and entropy generation analysis of MPCMS in straight, segmental, and rib-groove microchannel heat sinks: A numerical investigation

The efficient management of thermal systems is crucial for various technological applications, necessitating innovative cooling strategies to enhance performance and reduce entropy generation. Microchannels have emerged as a promising solution due to their high heat transfer rates and compact size. This study investigates the thermofluidic characteristics and entropy generation in straight, segmental, and rib-groove microchannels utilizing de-ionized water and microencapsulated phase change slurry (MPCMS) as working fluids. Employing numerical analysis, the investigation integrates a mixture model for the base fluid and micro-encapsulated phase change material (MPCM) using an equivalent heat capacity approach to incorporate the phase transition of the MPCM (composed of paraffin with a Ti shell). Operational parameters include an inlet fluid velocity ranging from 0.575 to 3.45 m/s, heat flux varying between 15 and 30 W/cm2, and MPCM volume fractions of 5% to 20%. The ANSYS Fluent Solver, a finite volume method using a multigrid solver, was used to control the simulation by species transport. Notably, segmental channels exhibit a notable decrease in wall temperature of 29.7% and 26.3% compared to straight and rib-groove channels, respectively, under constant heat flux and flow rate. However, the effectiveness of MPCM in enhancing thermal performance was greater in straight and rib-groove channels, surpassing segmental channels by 2.5% and 3.28%, respectively, under constant heat flux. On analyzing the irreversibility, segmental channels exhibit higher frictional entropy but lower thermal entropy generation due to the fin structure, resulting in an overall reduction in total entropy generation. Moreover, segmental microchannels, when utilizing MPCMS, demonstrate superior performance in reducing irreversibility by 60.66% and 49.6% compared to straight and rib-groove channels, respectively. Total entropy generation increases with higher velocity and heat flux, while it diminishes with higher MPCM concentration across all configurations.

A finite difference approach for analysis of entropy generation and stream surface on nonlinear convective magnetohydrodynamic flow over an oscillating surface

A finite difference approach for analysis of entropy generation and stream surface on nonlinear convective magnetohydrodynamic flow over an oscillating surface

Re-evaluating the cosmological redshift: Insights into inhomogeneities and irreversible processes

Understanding the expansion of the Universe remains a profound challenge in fundamental physics. The complexity of solving general relativity equations in the presence of intricate, inhomogeneous flows has compelled cosmological models to rely on perturbation theory in a homogeneous Friedmann-Lemaître-Robertson-Walker background. This approach accounts for a redshift of light encompassing contributions from both the cosmological background expansion along the photon's trajectory and Doppler effects at emission due to peculiar motions. However, this computation of the redshift is not covariant, as it hinges on specific coordinate choices that may distort physical interpretations of the relativity of motion. In this study we show that peculiar motions, when tracing the dynamics along time-like geodesics, must contribute to the redshift of light through a local volume expansion factor, in addition to the background expansion. By employing a covariant approach to redshift calculation, we address the central question of whether the cosmological principle alone guarantees that the averaged local volume expansion factor matches the background expansion. We establish that this holds true only in scenarios characterised by a reversible evolution of the Universe, where inhomogeneous expansion and compression modes compensate for one another. In the presence of irreversible processes, such as the dissipation of large-scale compression modes through matter virialisation and associated entropy production, the averaged expansion factor becomes dominated by expansion in voids that can no longer be compensated for by compression in virialised structures. Furthermore, for a universe in which a substantial portion of its mass has undergone virialisation, adhering to the background evolution on average leads to significant violations of the second law of thermodynamics. Our approach shows that entropy production due to irreversible processes during the formation of structures plays the same role as an effective, time-dependent cosmological constant (i.e. dynamical dark energy) without the need to invoke new unknown physics. Our findings underscore the imperative need to re-evaluate the influence of inhomogeneities and irreversible processes on cosmological models, shedding new light on the intricate dynamics of our Universe.