Thermodynamic Irreversibility Research Articles

Measuring Irreversibility from Learned Representations of Biological Patterns

Thermodynamic irreversibility is a fundamental characteristic of living matter, crucial for maintaining the complex spatiotemporal structures and functions that define biological systems. However, accurately quantifying biologically relevant irreversibility remains challenging due to noise and nonlinear interactions among many degrees of freedom. Here, we employ deep learning techniques to identify tractable, low-dimensional representations of phase-field patterns in a canonical protein signaling process—the Rho-GTPase system—as well as in complex Ginzburg-Landau dynamics. We demonstrate that factorizing variational autoencoder neural networks can robustly extract informative pattern features despite noise. These neural-network-derived representations reveal signatures of mesoscopic broken detailed balance and time-reversal asymmetry in both Rho-GTPase and complex Ginzburg-Landau wave dynamics. By applying the compression-based Ziv-Merhav estimator to these representations, we successfully recover irreversibility trends across complex Ginzburg-Landau patterns, which vary widely in spatiotemporal frequency and noise level. Our irreversibility estimates also recapitulate cell-activity trends in Rho-GTPase patterns subjected to metabolic inhibition. Furthermore, our framework distinguishes between stable and chaotic dynamical phases in these nonlinear systems. By leveraging advances in deep learning, our approach provides robust, model-free measurements of nonequilibrium and nonlinear behavior in complex living processes. Published by the American Physical Society 2024

Irreversibility Analysis of Radiative TiO2+Al2O3+Cu/H2O Ternary Nanofluid Flow over a Bidirectional Stretching Sheet with Cattaneo-Christov Heat Flux: Nanotechnology Applications

Abstract Ternary nanofluids demonstrate better heat transfer characteristics in contrast to conventional liquids and typical hybrid nanofluids. These are applied in sophisticated cooling systems for electronics, heat exchangers, and automotive engines, along with renewable energy systems such as solar collectors, where efficient heat transfer plays a crucial role. The aim of this research is to investigate the movement of a Casson ternary nanofluid passing through a bidirectional exponential sheet by employing the innovative Cattaneo-Christov heat flux concept. The utilization of the energy equation considers thermal radiation, viscous dissipation, and heat source/sink effects, with the integration of chemical reaction effects into the concentration equation. An analysis of entropy generation is utilized to evaluate the thermodynamic irreversibility within the system. The conversion of transport equations involves a transformation from partial to ordinary differential equations, followed by a numerical solution utilizing the BVP4C solver embedded in the MATLAB package R2022b. The impacts of developed factors on thermal, concentration, and velocity behavior, as well as engineering quantities, are thoroughly explored graphically. The outcome reveals that the velocity gradients diminish as magnetic fields intensify, while it amplified by the Hall factor. The rise in temperature of ternary nanofluid correlates with elevated levels of radiation, and Brownian motion. Concentration intensifies with the rapid development of thermophoresis influences. Heightened values of the Reynolds and Brinkman numbers give rise to amplified entropy production but a decrease in the Bejan number. The ternary nanofluid displays a remarkable 8.92% increase in skin friction on the x-axis and y-axis, influenced by the potent Darcy-Forchheimer factor. The rates of mass and heat transfer in nanofluids undergo a decrease of 8.58% and 12.52%, respectively, due to the heightened influence of Brownian motion and Eckert number. The results could provide valuable insights into the performance of ternary nanofluids in various industrial environments under specific conditions.

Does the Novel Dual Source Heat Pump (DSHP) Out-Perform the Ideal DSHP? Experimentation Versus Simulation of DSHP Based Thermodynamic Irreversibility of the Throttle Valve

Purpose: The air-source heat pumps are associated with continuous frosting problems. To ensure a more energy efficiency technology, the novel dual-source heat pump (DSHP) was developed. This article aims to confirm and compare the energy performance of the novel dual-source heat pump (DSHP) with the performance of an ideal heat pump. Methods: We applied an experimental analysis from an installed DSHP system with converters and other components to obtain the energy performance of the DSHP, while the performance of an ideal pump was obtained from simulation based on the theoretical algorithm of the basic principle of the thermodynamic irreversibility of the throttle valve. Results: We found that the Ideal (simulated) DSHP has a higher coefficient of performance (COP) than the installed (experimented) DSHP. The Ideal DSHP’s COP of 4.52 is higher than the Novel DSHP’s COP, which range from 1.78 (day 3) to 2.01 (day 1). The DSHP are power efficient, which reduces carbon emission from whatever power source that is been used. Implications: Energy efficiency in buildings has severe implications for global warmings and the need for sustainability. Because the modern ventilation system utilise energy from waste and heat recovery to power heating and cooling systems, the DSHP remains promising for future generations of building ventilation design. Originality/Value: The value of the study is because it completes an experiment that analyse the performance of the DSHP, comparing the outcomes with results from a simulation based on an Ideal system.

Stochastic computer experiments of the thermodynamic irreversibility of bulk nanobubbles in supersaturated and weak gas-liquid solutions.

Spontaneous gas-bubble nucleation in weak gas-liquid solutions has been a challenging topic in theory, experimentation, and computer simulations. In analogy with recent advances in crystallization and droplet formation studies, the diffusive-shielding stabilization and thermodynamic irreversibility of bulk nanobubble (bNB) mechanisms are revisited and deployed to characterize nucleation processes in a stochastic framework of computer experiments using the large-scale atomic/molecular massively parallel simulator code. Theoretical bases, assumptions, and limitations underlying the irreversibility hypothesis of bNBs, and their computational counterparts, are extensively described and illustrated. In essence, it is established that the irreversibility hypothesis can be numerically investigated by converging the system volume (due to the finiteness of interatomic forces) and the initial dissolved-gas concentration in the solution (due to the single-bNB limitation). Helium nucleation in liquid Pb17Li alloy is selected as a representative case study, where it exhibits typical characteristics of noble-gas/liquid-metal systems. The proposed framework lays down the bases on which the stability of gas-bNBs in weak and supersaturated gas-liquid solutions can be inferred and explained from a novel perspective. In essence, it stochastically marches toward a unique irreversible state along out-of-equilibrium nucleation/growth trajectories. Moreover, it does not attempt to characterize the interface or any interface-related properties, neither theoretically nor computationally. It was concluded that bNBs of a few tens of He-atoms are irreversible when dissolved-He concentrations in the weak gas-liquid solution are at least ∼50 and ∼105 molm-3 at 600 and 1000K (and ∼80 MPa), respectively, whereas classical molecular dynamics -estimated solubilities are at least two orders of magnitude smaller.

Multiple shape factor effects of nanofluids on marangoni mixed convection flow through porous medium

This study explores the effects of multiple shape factors on nanofluids within Marangoni mixed convection flows through porous media. Nanofluids, containing nanoparticles in a base fluid, show unique thermal properties, making them valuable in cooling systems, energy storage, and medical devices. Marangoni mixed convection, driven by surface tension gradients, adds complexity to fluid dynamics and heat transfer in porous media. Analytical and numerical analyses examine how various particle geometries, nanoparticle volume fractions, and porous medium configurations influence transport phenomena. Entropy analysis calculates thermodynamic irreversibilities. Findings reveal relationships between shape factors, heat transfer rates, velocity profiles, temperature distribution, and entropy generation rates, offering insights for optimizing nanofluid-based systems. The study also investigates magnetic forces, heat source/sink effects, and viscous dissipation on thermal energy transfer in Graphene oxide/water and Molybdenum disulfide/water nanofluids. Using similarity transformations, Partial Differential Equations are converted into Ordinary Differential Equations, solved with HAM and NDSolver by using the Wolfram tools. Results graphically depict velocity, temperature, entropy, and skin friction values, providing practical insights for engineering applications.

Hydrothermal Characteristics-Based Water Purification Model Using Hybrid Nanofluid Flow over Non-Linearly Stretched Permeable Surfaces

Sequel to all the published facts on the hydrothermal of pure water on a permeable expanding/contracting surface with thermodynamic irreversibilities convey iron (III) oxide and copper hybrid nanoparticles as applicable in industry and engineering, nothing is known about the importance of viscous dissipation and the Joule heating. The current paper addresses the natural convective flow of pure water, / nanofluid and-hybrid nanofluid, (a novel advanced nanofluid composited of and nanoparticles) induced by a non-linearly stretching permeable sheet with velocity slip using a numerical scheme. The equations obtained are solved numerically via Galerkin Weighted Residual Method (GWRM), in the limiting sense, the present results conform with the existing work. Analyses reveal that a 20% concentration of nanoparticles in a base fluid is more effective in the augmentation of heat transfer than a 10% concentration. Also, the nonlinearity parameter increased the heat transfer rate for the hybrid nanosuspension. The report of this study will be of benefit to chemical engineering and nanotechnology advancement.

Design and performance comparison of large-scale hydrogen liquefaction processes based on mixed refrigerant cycle

Liquid hydrogen (LH2) is an efficient carrier for storage and transportation of hydrogen energy. To investigate the effect of mixed refrigerant cycle (MRC) on the performance of large-scale hydrogen liquefiers, three processes with a capacity of 50 TPD LH2 are designed in a relatively achievable way. Process I utilizes a dual-pressure hydrogen Claude cycle with nitrogen precooling as a reference. Process II incorporates a five-component mixed refrigerant cycle in place of the nitrogen cycle. Process III advances further by replacing the hydrogen cycle in Process II with an additional MRC composed of Ne, He and H2. Sensitivity analysis is applied to optimize the parameters of the three processes prior to the comparison of their heat exchangers performance and the energy and exergy analyses. Due to the synergistic effect of smaller temperature difference and higher refrigeration temperature, the employment of MRC for precooling yields a SEC of 1.350 kWh/kg LH2, 57.1% and 66.3% lower than those of nitrogen cycle and liquid nitrogen, respectively. The sensible heat of the Ne/He/H2 mixture shows a better temperature matching than the latent heat of the refrigerant hydrogen when cooling the product hydrogen, reducing energy consumption by 28.4%. The utilization of MRC for precooling generates more exergy loss in the separators, mixers and throttle valves, but the absence of nitrogen expanders and much lower flow rate of refrigerant save more exergy in total. The essential reason for the progressiveness of Process III is that the integrated heat exchanger in the cryostat achieves the logarithmic mean temperature difference (LMTD) of 2.11 K, effectively reducing the exergy loss of the refrigerant compressors, thereby diminishing the thermodynamic irreversibility.

Sustainable light olefins synthesis via CO2 hydrogenation: Comparative exergetic, exergoeconomic, and exergoenvironmental analyses

CO2-to-olefins (CTO) technology has emerged as a worthy solution for green olefin production and greenhouse gas emissions mitigation. However, most of the present researches focus on the development of high-performance catalysts, while few of them devote to the process design and performance evaluation. Hence, this study proposed three candidate CTO processes via methanol-mediated, direct and indirect FTS-based routes. Based on the rigorous modeling and simulation, exergy-based (i.e., exergetic, exergoeconomic, and exergoenvironmental) analyses were conducted to quantify the overall exergy dissipation, economic cost, and environmental impacts. More specifically, we carefully assessed and compared their comprehensive performances from the system-level, and discern the origins and formation of economic cost and environmental impacts from the component level. As a result, the direct FTS-based process has the highest exergy efficiency of 68.65 %, while the indirect FTS-based process and the methanol-intermediated process exhibit the lowest unit exergoeconomic cost and exergoenvironmental impacts of 0.147 $/kW and 38.55 mPts/kW, respectively. In addition, some pertinent optimization suggestions were proposed to enhance the systems’ thermodynamic efficiency, economic and environmental benefits. Overall, this study offers crucial insights into the thermodynamic irreversibility, economic viability, and environmental sustainability of the proposed CTO systems, propelling the frontiers of future sustainable olefin production.

Sustainability evaluation of C3MR natural gas liquefaction process: Integrating life cycle analysis with Energy, Exergy, and economic aspects

In a transition towards a clean energy future, natural gas serves as an interim fuel due to its lower emissions whereas the C3MR (propane pre-cooled mixed refrigerant process) is widely recognized for high efficiency and commercial scale application converting natural gas to LNG. Previously, numerous studies have been conducted to optimize the energy efficiency and performance of C3MR process but very little contribution has been made towards its sustainability analysis. To address this, a life cycle analysis approach is established to evaluate the carbon footprint of C3MR process. In order to showcase its link with energy consumption and put forward the groundwork of analyses, the research focuses on using simulation – assisted optimization to reduce the specific energy consumption (SEC) of C3MR process by optimizing design variables. The study highlights the use of mixed refrigerant (MR) as a process variable and validates that its optimal implementation has decreased SEC to 0.2195 kWh/kg LNG, while achieving a minimum inlet temperature approach (MITA) of main cryogenic heat exchanger (MCHX), less than 3 °C. The knowledge − based optimization approach applied in this research, developed comparative case studies on which multiple analyses are performed to verify scientific findings. Energy and exergy analyses are conducted to determine thermal efficiency of the process where the optimized case exhibits a reduced difference in its composite curves and an 8.65 % improvement in exergetic performance compared to the base case. The economic indicators assessment reveals that optimized case demonstrates lower capital and operating costs, establishing economic viability. Furthermore, the energy consumption parameters are utilized for evaluation of ecological impact ofLNGsupply chain through life cycle assessment (LCA) which reflects reduced greenhouse gas (GHG) emissions for optimized case. Hence, the current study fills existing research knowledge gaps in terms of providing a comprehensive process system engineering by evaluating energy synergistic point, thermodynamic irreversibility, process viability and sustainability using life cycle assessment.

Landauer Bound in the Context of Minimal Physical Principles: Meaning, Experimental Verification, Controversies and Perspectives

The physical roots, interpretation, controversies, and precise meaning of the Landauer principle are surveyed. The Landauer principle is a physical principle defining the lower theoretical limit of energy consumption necessary for computation. It states that an irreversible change in information stored in a computer, such as merging two computational paths, dissipates a minimum amount of heat kBTln2 per a bit of information to its surroundings. The Landauer principle is discussed in the context of fundamental physical limiting principles, such as the Abbe diffraction limit, the Margolus–Levitin limit, and the Bekenstein limit. Synthesis of the Landauer bound with the Abbe, Margolus–Levitin, and Bekenstein limits yields the minimal time of computation, which scales as τmin~hkBT. Decreasing the temperature of a thermal bath will decrease the energy consumption of a single computation, but in parallel, it will slow the computation. The Landauer principle bridges John Archibald Wheeler’s “it from bit” paradigm and thermodynamics. Experimental verifications of the Landauer principle are surveyed. The interrelation between thermodynamic and logical irreversibility is addressed. Generalization of the Landauer principle to quantum and non-equilibrium systems is addressed. The Landauer principle represents the powerful heuristic principle bridging physics, information theory, and computer engineering.

Computational framework for thermal transportation in radiative bio-convective micropolar nanomaterial flow over stretched sheet with entropy optimization

Entropy generation (EG) in bioconvective nanofluid flows is a phenomenon that occurs due to the presence of nanoparticles and microorganisms within fluid flows. EG leads to an increase in thermodynamic irreversibility within the system. Understanding and quantifying EG in nanofluid flows is essential to optimize heat transfer processes and design efficient systems. Current investigation aims to analyze the irreversibility of the magnetized bioconvective flow of non-Newtonian micropolar type nanofluid. Flow features are modeled considering flow by a Darcy Forchheimer permeable surface of a stretched sheet. Phenomenon of bioconvection in a micropolar fluid is considered to regulate the solid tiny particles. Magnetic field and permeability effects are accounted in momentum relation. Energy relation is constructed in the presence of Joule heating, internal fluid friction, and thermal radiation. Mass concentration equation is formulated by accounting Arrhenius kinetics and binary chemical reaction. Furthermore, the buoyancy effects of solid tiny particles are considered in thermal and concentration relations. Total entropy of the considered flow is modeled using the second thermodynamics law. System of dimensional equations representing the flow is obtained with the implementation of boundary layer approximations. The acquired system is altered into an ordinary one through transformations and then tackled by numerical scheme Runge-Kutta-Fehlberg method (RKF-45) in the Mathematica package. Behavior of velocity, thermal field, entropy production, mass concentration, motile density, and Bejan number versus sundry variables is investigated through plots. Skin friction, local heat, mass, and density rates are numerically examined. Thermal field upsurges and velocity field decays versus higher Hartmann number. Entropy generation improved versus higher Brinkman number, microorganisms diffusion variable, and temperature difference ratio variable.

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.

Entropy optimization of lid-driven micropolar hybrid nanofluid flow in a partially porous hexagonal-shaped cavity with relevance to energy efficient storage processes

Hydromagnetically associated heat convection can greatly enhance the performance of high-efficiency thermal appliances and renewable energy sources through an optimized design. This investigation examines the production of thermodynamic irreversibility and heat convection for a double lid-driven flow within a partially porous stratified hexagonal enclosure. The top and bottom-wall are moving in the opposite direction with an equal velocity U0. The top-wall and the bottom-wall are kept at temperature Tc and Th (Th >\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$>$$\\end{document} Tc) while the slanted walls are assumed to be thermally insulated. A constant magnetic field is employed in the horizontal x-direction. The hexagonal cavity was filled with a micropolar hybrid nanofluid Ag-MgO/water. The system of dimensionless equations was solved by the finite difference method (FDM) associated with successive over-relaxation (SOR), successive under-relaxation (SUR), and Gauss–Seidel iteration tactics and required results are computed with problem specific program in MATLAB code. The results indicate that the Ra and the thickness of the porous layer (Xp) significantly influences heat convection and thermal irreversibility processes. The Nuavg and STotal rises 6.299% and 3.373% as ‘ϕhnf\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\upphi }_{{\ ext{hnf}}}$$\\end{document}’ enhances from 0 to 4%, respectively. Furthermore, as the values of Ra, Ha, K0, and ϕhnf\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\upphi }_{{\ ext{hnf}}}$$\\end{document} increase, Beavg experiences a decline of 53.73%, 11.04%, 38.36%, and 0.09% respectively. Also, movement of wall has a significant impact on heat transfer rates and entropy production. The present study may be extended in numerous areas to mimic the problems like—(1) onset of thermo-mechanical process for solid–fluid interaction in a conduit. (2) Thermos-chemical process with extraction of ions in two-phase fluid for double layer plating on a continuously moving sheet, as region of porous stratum saturated with a class of fluid and region without porous medium occupied with other fluid.

Shape matters: Convection and entropy generation in magneto-hydrodynamic nanofluid flow in constraint-based analogous annular thermal systems

This work analyzes the performance of annular thermal systems of distinct geometries to understand their shape impacts using a novel constraint-based methodology. This research fills the gap in the literature by analyzing the geometrical shape impact of magnetohydrodynamic CuO/water nanofluid flow on fluid flow, heat transfer, and thermodynamic irreversibility. Through computational simulations, the outcome results demonstrate that the circular annuli (Case 1 and Case 2) outperform the analogous square system in terms of fluid velocity, heat transfer, and irreversibility. The analysis is carried out for a range of Rayleigh numbers (Ra = 103 to 106), nanoparticle concentrations (ζ = 0 to 4%), magnetic fields (Ha = 0 to 100), and magnetic field inclinations (γ = 0° to 180°). Additionally, a significant improvement in heat transfer is observed by augmenting nanoparticles of the working fluid, while the magnetic field intensity plays a crucial role in controlling fluid flow and heat transfer. The study provides valuable insights into how various parameters affect the nanofluidic heat and flow characteristics of equivalent annular geometries and contributes to the development of more efficient and effective designs of thermal systems. The novelty of the study lies in its comprehensive approach in the use of a constraint-based methodology that matches the flow areas or cooling lengths while maintaining the same heating length to analyze the impact of geometric shapes on heat transport and accompanying irreversibility during MHD nanofluid flow. Furthermore, the energy-flux vectors are utilized to delve into the insights. The maximum value of heat transfer noted for Case 1 and Case 2 is approximately 7% and 11%, respectively, compared to the square annulus (Base Case). The inclusion of nanoparticles in the carrier fluid causes a significant enhancement in heat transfer by up to 11%, compared to pure fluid (ζ = 0).

On the Supposed Mass of Entropy and That of Information.

In the theory of special relativity, energy can be found in two forms: kinetic energy and rest mass. The potential energy of a body is actually stored in the form of rest mass, the interaction energy too, but temperature is not. Information acquired about a dynamical system can be potentially used to extract useful work from it. Hence, the "mass-energy-information equivalence principle" that has been recently proposed. In this paper, it is first recalled that for a thermodynamic system made of non-interacting entities at constant temperature, the internal energy is also constant. So, the energy involved in a variation in entropy (TΔS) differs from a change in the potential energy stored or released and cannot be associated to a corresponding variation in mass of the system, even if it is expressed in terms of the quantity of information. This debate gives us the opportunity to deepen the notion of entropy seen as a quantity of information, to highlight the difference between logical irreversibility (a state-dependent property) and thermodynamical irreversibility (a path-dependent property), and to return to the nature of the link between energy and information that is dynamical.

Design and thermo-enviro-economic analyses of a novel thermal design process for a CCHP-desalination application using LNG regasification integrated with a gas turbine power plant

Designing and studying processes with reduced thermodynamic irreversibility and environmental impact is imperative to improve the global applicability of the stand-alone gas turbine cycles. Hence, the present study introduces a novel cascade heat integration tool for a gas turbine cycle combined with a liquefied natural gas cold energy utilization and regasification process. A saltwater desalination subsystem, an absorption chiller, and an organic Rankine cycle are also included in the integrated system. Therefore, the developed system demonstrates an environmentally friendly combined cooling, heating, power, and freshwater production framework, improving the performance of the system in comparison to previous research. This configuration is simulated within the Aspen HYSYS software for comprehensive energy, exergy, environmental, and economic assessments. The findings demonstrate that the whole configuration yields energy and exergy efficiencies of 92.92% and 63.5%, respectively. In comparison, these efficiencies in the single-generation mode are found to be 45.92% and 43.72%, correspondingly. The environmental analysis reveals that the carbon dioxide footprint equals 0.1792 kg/kWh when operating in the multigeneration mode and 0.4591 kg/kWh in the single-generation mode. Furthermore, the economic evaluation exhibits that the cost of energy equals 67.2 $/MWh and 135.92 $/MWh for the multigeneration and single-generation operational modes, respectively.

A Comprehensive Review of the Thermohydraulic Improvement Potentials in Solar Air Heaters through an Energy and Exergy Analysis

Supply disruptions, uncertainty, and unprecedented price rises of fossil fuels due to the recent pandemic and war have highlighted the importance of using renewable sources to meet energy demands. Solar air collectors (SACs) are major types of solar energy systems that can be utilized for space and water heating, drying, and thermal energy storage. Although there is sufficient documentation on the thermal analyses of SACs, no comprehensive reviews of the exergetic performance or qualitative insight on heat conversion are available. The primary objective of this article is to provide a comprehensive review on the optimum conditions at which the thermal performance of diverse types of solar air collectors is optimized. The effect of operating parameters such as temperature rise, flow rate, geometric parameters, solar radiation, and the Reynolds number on the thermal performance of SACs in terms of thermal hydraulic performance, energy, and exergy efficiencies has been reviewed adaptively. Beyond the operating parameters, a deep investigation is outlined to monitor fluid dynamics using analytical and computational fluid dynamics (CFDs) methodologies in the technology of SACs. In the third phase, thermodynamic irreversibility due to optical losses, thermal losses between absorber and environment, heat losses due to insulation, edge losses, and entropy generation are reported and discussed, which serve as the fundamental tools for optimization purposes.

Thermodynamic feasibility evaluation of an innovative multigeneration system using biogas dry reforming integrated with a CCHP-desalination process

This work investigates a new method for developing systems that use a creative heat integration process that provides heating, cooling, fresh water and power. Specifically, the suggested framework operates by syngas obtained through the dry reforming process of biogas. Environmental considerations and decrease in thermodynamic irreversibility are main features of suggested system. The energy, exergy-related, environmental, and thermoeconomic properties of the suggested system are evaluated after it has been simulated using the Aspen HYSYS software. Results indicate 99,775.5 kW of net power, 10,880 kW of cooling power, and 141,800 kW of heating power. Also, the multigeneration scenario exhibits energy and exergy efficiencies of 58.06 % and 36.0 %, respectively. From the exergetic point of view, total exergy destruction rate is found at 493479 kW. The results of the environmental assessment show that the structure emits 0.27 kg of carbon dioxide per kWh while it is operating in the multigeneration mode. This value is contrasted with a reduction of 34.15 % in heat generation and a decrease of 69.11 % in power generation modes. According to the economic study, when the system functions under multigeneration conditions, the total equipment cost and the levelized cost of products are obtained at 59,536,233 $ and 0.029 $/kWh.

Thermohydraulic performance analysis and parameters optimization of the combined heat sinks with microchannels and micro pin-fins

The combined heat sinks of microchannels and micro pin-fins are numerically studied in depth by three-dimensional conjugate heat transfer models for flow rate (Qv) ranging from 18 to 90 ml/min. The influence degrees of multiple parameters, i.e., the lengths and widths of the cavities and pin-fins, on cooling effect, pressure drop and comprehensive performance are analyzed quantitatively by Taguchi method. And the optimal combination structures for temperature of heat sink (OCS-T), pressure drop (OCS-PD) and performance evaluation criterion (OCS-PEC) are obtained accordingly. The original heat sink with fan shaped cavities and diamond pin-fins (FC-DPF) and the smooth rectangular heat sink (SR) are selected for comparison. The coupling effects of four structure parameters on the local and average thermal hydraulic characteristics are elucidated. The interrelation of multiple physical fields and the comprehensive efficiency of the optimal combination structures are discussed thoroughly. Moreover, the thermodynamic properties and irreversibility are illustrated based on the entropy generation. Results demonstrate that the length of fan shaped cavity and the width of diamond pin–fin have a dominant impact on heat dissipation and pressure drop. The width of cavity has a noticeable impact on the overall performance. Large width of cavity is favorable to induce transverse flow, and large width of pin–fin contributes to distinct vortices. The symmetrical vortices in the direction of channel height can improve chaotic mixing and temperature uniformity. At high flow rate, the performance evaluation criterion (PEC) of the OCS-PEC is increased by 29 % compared to the original structure FC-DPF. When total thermal resistances of the above two heat sinks are similar (0.43 K/W of the OCS-PEC and 0.45 K/W of the FC-DPF), the pumping power of the OCS-PEC (0.47 W) is 35 % lower than that of the FC-DPF (0.72 W) proving the excellent overall efficiency. In addition, the OCS-PD and OCS-PEC show better thermodynamic performance and less irreversible loss for high flow rate, which implies the energy efficiency advantage. The synergistic mechanism of flow and heat transfer is revealed and the results are significant for further understanding the rules of performance enhancement. The excellent overall performance of the OCS-PEC at high flow rate makes it more promising in application for electronic chips cooling in aerospace, defense and communication fields, thermal management of battery, hydrogen storage, fusion energy management, etc.

EFFECT OF THE NANOFLUID FLOW AND EXTENDED SURFACES ON AN ABRUPT EXPANSION TUBE REGARDING THERMODYNAMIC IRREVERSIBILITY

Numerous scientists have examined circular dimpled surfaces, tubes, and other approaches for enhancing heat transfer. Moreover, the dimples' angle of attack has a substantial effect on the tube's flow and thermal features. This numerical study presents a novel approach to enhancing heat transfer rate in a tube subjected to constant heat flux by incorporating a surface dimpling strategy and evaluates three different tube layouts with elliptical dimpled fins for different working fluids such as DW and Al<sub>2</sub>O<sub>3</sub>/DW nanofluid (φ = 0.5-1.0%) by using ANSYS Fluent v2020R2 under laminar flow conditions. Under identical circumstances, the thermal performances of proposed designs are compared to those of a smooth tube, and the influence of the elliptical dimpled fin angle of attack on these parameters is determined for different Reynolds numbers (1000 ≤ Re ≤ 2000). When comparing the Nusselt number of a tube with/without elliptical dimpled fins, it is found that EDT 1 performed better. Lower Reynolds numbers are shown to result in a greater friction factor. Besides, elliptical dimpled fins promote flow mixing within the tube and the establishment of a thermal boundary layer. At a 135° attack angle (EDT 1), the 1.0% Al<sub>2</sub>O<sub>3</sub>/DW nanofluid is found to be the best-performing nanofluid in the dimpled tube, improving Nu by up to 44.56%. Furthermore, ff presented an increase of 29.18% when comparing ST and EDT 1 flowing 1.0% Al<sub>2</sub>O<sub>3</sub>/DW at Re = 2000, while total S<sub>gen</sub> is diminished by 37.75% in the same conditions.