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Some errors exist in the above paper. [ABSTRACT FROM AUTHOR]

One of the target of the above paper is the study of the entropy generation (it is included in the title). However, two serious errors exist in the study of entropy generation. [ABSTRACT FROM AUTHOR]

This comment concerns a rightful doubt involved in the above paper. In the reviewed article, a novel model without empirical constants was proposed to evaluate the effective thermal conductivity of three-phase soils, and such a model was claimed to be workable for soils with porosity ranging from 0.0349 to 0.4764 at all saturation degrees. However, sufficient reasons and pictorial explanations were given in this comment to prove its inapplicability for high degrees of saturation. Besides, the inapplicable range is constantly changing, depending on the porosity, i.e. the larger the porosity, the smaller the inapplicable saturation region. Similar issues were further discussed due to its great influence on the follow-up research in this field, i.e. whether can achieve a full coverage of the applicable saturation range [0,1] for a given porosity. [ABSTRACT FROM AUTHOR]

Abstract The present comment concerns some doubtful results included in the above paper. [ABSTRACT FROM AUTHOR]

Two mistakes exist in [1]. [ABSTRACT FROM AUTHOR]

In this study, the relationship between freezing point and suction of four types of chloride loess samples (CaCl 2 , MgCl 2 , NaCl and KCl) was investigated by freezing point tests and filter paper method-based suction tests. Break points were observed from the freezing point versus water content curves near the plastic limit, which decline at higher salt contents. The freezing point declines roughly linearly with salt content for samples with 2–1 type chloride salts (CaCl 2 and MgCl 2), while decreases attenuatedly for those with 1–1 type chloride salts (NaCl and KCl). The higher the cation content, the more significant the freezing point depression, and the ranking of Mg2+ > Ca2+ > Na+ > K+ was roughly noted, which is linked with the cation hydration capacity. In addition, the relationship between the osmotic suction of samples h 0soil and that of chloride solution h 00solution was suggested to be described by a linear relationship. The freezing point of samples depends on both matric suction and osmotic suction. The limitations of the Mizoguchi's model were noticed through data analysis and by retaining its basic construct, a suction-based model for freezing point of chloride loess was established and verified. • Relationship between freezing point and suction of chloride loess was revealed. • Effect of cations on freezing point of chloride loess depends on hydration degree. • Osmotic suction of chloride loess is fitted as a function of that of chloride solution. • A modified Mizoguchi model for chloride loess considers the influence of suction. [ABSTRACT FROM AUTHOR]

The present comment concerns some doubtful results included in the above paper. [ABSTRACT FROM AUTHOR]

With the highly integrated development of electronic components, higher requirements are put forward for heat transfer components, there is an urgent need for high-performance heat transfer components. Oscillating heat pipe (OHP) is novel types of heat pipe with excellent heat transfer capability. However, the heat transfer limit hinders their operation and application. This paper proposes an OHP under trans-critical conditions with the working fluid of R218 and explores its operating characteristics and heat transfer capability. Visualization experiments and pressure monitoring were conducted to analyze the state changes within the OHP under trans-critical conditions. After evaporation section temperature surpassing the critical temperature of R218, the pressure increases with the temperature, once the pressure reached near the critical pressure, OHP can transcend the limitation of the critical temperature and realize efficient oscillating operation under trans-critical conditions. With stable operation, the working fluid velocity can reach up to 1.49 m/s, and the OHP under trans-critical conditions presented excellent heat transfer performance with the thermal resistance of 0.22 °C/W. This paper proves the feasibility of the OHP under trans-critical conditions and provides a basis for further research. [ABSTRACT FROM AUTHOR]

Heat exchanger studies have been conducted for several decades since the beginning of the development of heat transfer theories due to their widespread use in various industries. The ongoing research topics include heat exchanger efficiency, design parameter optimization, material development, and heat transfer technology exploration. Research has been continued to evolve nanofluid compositions, concentrations, and operating conditions that affect heat exchanger efficiency. They have used hybrid nanofluids in heat exchangers, which contain multiple types of nanoparticles or nanoparticles with additional additives, as hybrid nanofluids improve thermal performance. As a result, the development and optimization of hybrid nanofluids as a working medium in heat exchangers are gaining popularity, and the use of hybrid nanofluids in heat exchangers has already drawn a lot of interest as a viable strategy in industrial sectors. Therefore, such a surge of interest in using hybrid nanofluids in heat exchangers has resulted in a significant body of literature on this. In this review paper, the authors aim to incorporate the findings of these studies and offer a thorough evaluation of the state-of-the-art research on the application of hybrid nanofluids in various types of heat exchangers. This review provides a synopsis of the published literature on the efficacy of heat exchangers utilizing hybrid nanofluid. The researchers have also encountered and documented several challenges, including stability and aggregation, improving thermal conductivity, fluid flow characteristics, corrosion and material compatibility, cost and scalability, and determining the ideal size and shape of nanoparticles while considering environmental and health concerns. In addition, this review identifies research gaps in preventing agglomeration, ensuring nanoparticle dispersion, optimizing fluid composition to minimize flow effects, exploring and identifying materials compatible with hybrid nanofluids, investigating cost-effective methods for hybrid nanofluid production, and addressing scalability issues for widespread implementation in industrial heat exchangers. This review paper will be a valuable resource for researchers and practitioners seeking to overcome these challenges and advance the field of hybrid nanofluids for heat exchanger applications. [ABSTRACT FROM AUTHOR]

This paper focuses on researching the various factors that influence the material melting rate during the hot air melting process. To achieve this purpose, the paper proposes a melting model for Acrylonitrile-Butadiene-Styrene (ABS) plastic under hot air heating based on Computational Fluid Dynamics (CFD). Orthogonal experiments were conducted based on the parameter range of each factor obtained in the pre-experiment. The results showed that the outlet distance, hot air velocity, hot air temperature, and their interaction items are important factors that affect the melting rate of ABS materials. Based on the simulation results, a multiple nonlinear regression model was constructed to predict the melting rate under different parameters. Comparing the simulation values with the predicted values of the multiple nonlinear regression model, the error between the two was no >10%, indicating the effectiveness of the prediction model. The research results can help guide the hot air welding melting process for different materials and characteristics, and provide a certain reference value for the development of hot air welding technology. • Welding of airbag labels was performed using hot air welding technology; • Realizes real-time monitoring of melt quality during the material melting process • Using CFD modeling to study the effects of outlet distance, hot air velocity, and hot air temperature on the melting rate. [ABSTRACT FROM AUTHOR]

The distributed energy supply system provides a good scheme for energy supply. The micro gas turbine with a recuperator is a common power device in distributed energy supply systems. In recent years, several achievements have been made in the development of micro gas turbine recuperators. Plate-fin and primary surface recuperators have been used in mature applications. Moreover, the thermodynamic properties of the heat transfer channel have been studied in detail. Among them, the cross wavy primary surface recuperator developed by Capston Company is one of the important achievements. This paper reviews the technical development of thermodynamic performance of micro gas turbine recuperator in recent years. The micro gas turbine recuperators are divided into plate-fin and primary surface recuperators commonly. In this paper, the correlation formula, heat exchange enhancement, optimum design and the influence of recuperator on the overall machine performance are reviewed. It has been found that the plate-fin recuperators have been sufficiently studied by scholars, and the results are more comprehensive. As for the primary surface recuperators, which have just become popular in recent years, the research results are less comprehensive due to their unique structure. In the future development of micro gas turbine recuperators, this will be the future research and development trend due to the high heat exchange efficiency and the lack of comprehensive research on primary surface recuperators. [ABSTRACT FROM AUTHOR]

Following paper presents an experimental study on eight potential plate materials for evaporative air coolers. There are three groups of materials: currently used plate materials (kraft papers), new natural origin plate materials (cotton fibers), and new synthetic plate materials (synthetic fibers). Proposed materials were examined in terms of different properties such as upward and downward distribution height, water capacity, durability and diffusivity. The results were compared with data presented by other authors. It was established that, synthetic materials are characterized by superior water distribution qualities in comparison to the materials of natural origin. Basalt paper-like synthetic fiber allowed to rise water vertically to 40 cm during 120 min tests. The highest water rise obtained in other studies was 18 cm, hence basalt paper-like fiber is visibly superior in comparison with the currently known materials. In terms of downward water distribution, two new synthetic surfactant non-wovens show better performance than the existing materials by quickly and evenly distributing water over the entire length of the sample. The durability of synthetic fibers and non-wovens is higher comparing with the materials of natural origin. The results show that synthetic materials are better suited to the role of plate materials in evaporative air coolers. • Experimental tests of eight potential plate materials for evaporative coolers • The tests include upward and downward water distribution, diffusivity and durability. • New materials show visibly higher performance in terms of most effectiveness factors. • Synthetic materials are confirmed to be most promising for evaporative coolers. [ABSTRACT FROM AUTHOR]

This paper is the second of a two-part series that presents experimental data and analysis on the liquid nitrogen quenching heat transfer process of a stainless-steel tube with an inner surface low-thermal conductivity thin-film coating. This paper focuses on the effects of different flow directions and two tube wall thicknesses. Additionally, this paper also provides an analysis on the chilldown thermal efficiency of the quenching process. Three flow directions with four different inner surface coating modifications, and three tube wall thicknesses were examined. The experimental data covers the Reynolds numbers ranging from 3500 to 140,000. The chilldown efficiency, along with chilldown time and LN 2 (liquid nitrogen) mass consumption were analyzed to assess the overall performance of the LN 2 line chilldown process. For thin tube wall cases, the chilldown efficiencies cover a range between 3% and 41%, and the maximum chilldown efficiency value is found for the tube with 3 L coating at Re = 5278 in the vertical up flow direction. For thick wall tube cases, the efficiencies cover a range between 4% and 52%, and the maximum chilldown efficiency value was found for the tube with 4 L coating at Re = 5308 in the vertical up flow direction. [ABSTRACT FROM AUTHOR]

Surfactant flooding is an effective method for enhanced oil recovery and does not lose its relevance. This paper investigates the influence of pore space heterogeneity on dynamic surfactant adsorption in porous media. The novelty lies in the study of dynamic adsorption with multiphase flows. The paper presents new results characterizing the influence of pore space heterogeneity under different wetting angles and viscosity ratios. We consider sodium methyl ester sulfonate as a water-soluble surfactant. The results are based on numerical experiments on groups of 2D isotropic monodisperse porous structures with various pore space heterogeneities, characterized by the disorder coefficient. The lattice Boltzmann equations are used as a mathematical model. Pore space heterogeneity is a factor that can significantly suppress the adsorbed amount. The strength of the influence depends on the wetting conditions and viscosity ratios. An increase in the disorder coefficient enhances the effect of the wetting angle, but an increase in the wetting angle reduces the effect of the disorder coefficient. The influence of pore space heterogeneity does not depend on the viscosity ratio and weakens when transitioning from drainage to imbibition mode. The prediction accuracy of the adsorbed amount deteriorates with an increase in the disorder coefficient and the displaced fluid viscosity. [ABSTRACT FROM AUTHOR]

The selection of optimal design and the most efficient operational parameters for energy devices constitute a priority task for sustainable development and increasing energy efficiency within the net-zero emissions strategy. This is particularly important in adsorption cooling and desalination systems with poor performance due to unfavourable heat transfer conditions in conventional packed beds of adsorption chillers (ACs). Therefore, looking for additional ways of performance improvement is still challenging, especially covering different design variants and operational strategies. The existing complex, time-consuming and costly analytical, numerical and experimental methods, usually focused on a specific design and operating parameters of conventional packed adsorption beds, cannot tackle these comprehensive problems. Since artificial intelligence (AI) based models are considered tools that sometimes may overcome the shortcomings of the programmed computing approach and the experimental procedures, the paper introduces automated machine learning (AutoML) as a general approach for the design and optimization study of adsorption cooling and desalination systems. The double-effect, i.e. specific cooling capacity (SCP) and specific daily water production (SDWP) of various adsorption chillers (ACs) operating in large-, pilot- and small-scale adsorption cooling and desalination systems, is considered in the study. The paper also presents a novel big data optimization procedure for selecting the best operating and design strategy in adsorption cooling and desalination technology. Finally, a new concept of fluidized bed-type application in adsorption chillers is proposed, which allows for enhancing the performance of ACs. The presented approach can be referred to as a complementary design technique in adsorption cooling and desalination systems, besides the existing complex analytical and time-consuming numerical methods and expensive experiments. • Double-effect desalination and cooling production in adsorption chillers (AC) are evaluated • The new approach allows considering various cooling and desalination adsorption systems. • The novel concept of fluidized bed application in adsorption systems is proposed. • The developed models constitute powerful tools for optimizing ACs systems' performance. [ABSTRACT FROM AUTHOR]

Nanochannels consisting of hot and cold walls with periodic rectangular and triangular nanostructures were simulated by molecular dynamics in this paper, the periodic size dimensionless parameters φ was defined to describe the dimension of nanostructures on the wall. The results show that the addition of nanostructures leads to the variation of mass density distribution of fluid near the wall. A hot wall with nanostructures can promote the appearance of a fluid high-potential area near it. The discrepant attraction for fluid from the wall caused by the different wall conditions leads to different flow characteristics in nanochannels. Fluid velocity growth rate near the hot wall is 10.5% higher than that near the cold wall. Average velocity of the fluid near the hot wall is 5.1% higher than that of fluid near the cold wall. A wall with rectangular nanostructures at φ = 0.28 shows minimum flow resistance among rough hot walls, while a wall with triangular nanostructures at φ = 0.14 has minimum flow resistance among rough cold walls. Heat is transferred from the hot wall to the cold wall through fluid flow. Wall conditions impact the heat transfer situation of fluid in flow boundary by changing the fluid mass density contribution. The addition of nanostructures and decrease of nanostructures size is beneficial for heat transfer while unfavorable for fluid flow, convective heat transfer was influenced by their combination. For a wall with 300 K, the addition of rectangular nanostructures at φ = 0.07 has the best convective heat transfer performance. For a wall with 200 K temperature, increasing triangular nanostructures at φ = 0.14 on the wall can reach the best convective heat transfer capacity. This paper can provide a theoretical foundation for the optimization of nanochannels to achieve best convective heat transfer ability. [ABSTRACT FROM AUTHOR]

The presence of magnetic field results in a reduction in natural convective heat transfer and entropy generation in cavities. The use of nanofluids improves the performance of thermal systems. The present paper discusses the impact of uniform and non-uniform magnetic fields on the second-law performance of nanofluid-filled and porous cavities, introduces artificial intelligence (AI) approaches, and examines the applications of AI in optimizing heat transfer and entropy generated in these systems. The mathematical formulation is presented in terms of the entropy generation for natural convection in cavities. This paper demonstrates the influences of various important non-dimensional parameters on entropy generation in cavities. Besides, advances in the second-law performance of cavities and the role of AI techniques in the field are discussed and future directions are provided. [ABSTRACT FROM AUTHOR]

Flow control is essential in high-pressure CO 2 systems. Flow regulators are widely used for flow adjustment in piping systems. In this paper, a novel combinational flow regulator is proposed, which contains four parallel branch channels, and each channel is arranged with a solenoid valve and an orifice plate. In order to analyze the internal flow characteristics of high-pressure CO 2 and flow adjustment performance of the proposed flow regulator, a numerical model of the regulator is established, and the validation of numerical model is verified by experimental results. Then, the pressure and velocity characteristics are studied numerically. Finally, the flow adjustment performance is investigated numerically and experimentally from three aspects: variation of flow rate with differential pressure, variation of the product of flow coefficient and throttling area, and dynamic variations of pressure, temperature and flow rate of the flow regulator. This paper serves as a valuable reference for researchers utilizing flow regulators to adjust the flow rate of CO 2 or other fluids. • Numerical model of a novel flow regulator is established, verified by experiments. • Pressure and velocity characteristics are discussed, CO 2 as working medium. • Variation of flow rate with differential pressure and flow area is analyzed. • Dynamic working situation of the regulator is investigated by experiments. [ABSTRACT FROM AUTHOR]

A numerical investigation was conducted to explore the heat transfer optimization effect of circular tube heat exchanger with L-shaped twisted tape insert and to find the optimal parameter design in this paper. For better thermohydraulic performance, the effects of twist pitch (P), inner diameter (D), tape width (W) and number of tape (N) were studied with Reynolds number ranged from 1875 to 3750. Moreover, response surface method (RSM) was employed to indicate the relationship between the Nusselt number (Nu) and these parameters. With the analysis of flow structure inside the tube, it was conducted that the twisted tape insert was helpful to transform the axial velocity of fluid to radial velocity, forming vortex in the L region. The numerical results showed that the Nu and friction factor (f) of the tube fitted with L-shaped twisted tape insert gained an 199% to 208% increase and 674% to 696% when compared with that of smooth tube respectively. Besides, an optimal parameters set was obtained with P = 65.59 mm, W = 0.95 mm, D = 8.80 mm, in which the Nu and f were increased by 204% and 704% respectively as the results of response surface method. • Effects of L-shaped twisted tapes insert on heat transfer and flow characteristics in were numerically investigated. • The influence of four geometric parameters of twisted tape insert on thermos-hydraulic performance were studied. • The enhanced thermal performance of the L-shaped twisted tapes was obtained by centrifugal force. • The effect of short side of the L-shaped on the thermal performance and flow characteristics were discussed. [ABSTRACT FROM AUTHOR]

The escalating gas turbine (GT) inlet temperature and the amplifying radiation effect of multi-component radiation gases aggravate the thermal radiation phenomena. In addition, the omission of radiation effect in the classical film cooling scaling criteria makes the research data obtained under relative low temperature conditions invalid. This paper provided a mechanistic-level explanation of the influence of the thermal radiation term on the energy equation, and subsequently introduced two novel dimensionless parameters (radiation number and optical thickness) that can effectively reflect the radiation impact on scaling criteria. Furthermore, three parameter matching schemes were proposed to enable the data match of high and low temperature conditions for adiabatic cooling effectiveness, overall cooling effectiveness, and dimensionless radiation heat flux. Compared to the high temperature test method, the scaling criteria can provide valuable insights into the film cooling behavior under realistic GT conditions. The method proposed in this paper can not only help prevent material loss and energy waste but also align with the principles of energy conservation, emission reduction, and sustainable development. • R n and τ g were introduced to effectively reflect the radiation impact on scaling criteria. • The determination process of wall emissivity and gas absorption coefficient was proposed. • Three schemes of novel scaling criteria were presented. [ABSTRACT FROM AUTHOR]

The thick-layer drying kinetics of moisture-containing porous material (honeysuckle) at constant temperature and humidity are experimentally investigated, and the drying characteristics under variable temperature and humidity conditions are analyzed in this paper. The results show that the drying rate is constant and linearly/positively corrected with the moisture content under constant temperature and humidity conditions, and the corresponding slope (drying rate constant) decreases exponentially with the increase in the number of stacked layers because of the increased flow resistance and diminished convective migration of water vapor. The migration of saturated water vapor changes from convection-dominated to diffusion-dominated after the thickness of the stacked materials exceeds a critical value. Based on the experimental data, a new semi-theoretical drying model was proposed for thin-layer and thick-layer drying of moisture-containing stacked porous materials, and it was experimentally verified with a coefficient of determination greater than 0.92. The relative humidity of the drying medium is a key factor in determining the drying rate, and reducing the relative humidity of the drying medium at a constant temperature is suitable for drying heat-sensitive materials. This paper can contribute to the development of drying kinetics and provide a theoretical basis for the drying of moisture-containing porous material. • A new drying kinetic model is proposed for thin-layer and thick-layer drying. • Drying rate constant decreases exponentially with the increasing stacked layers. • Mechanism of hot air drying of honeysuckle (porous material) is discussed. • Effects of temperature, humidity, and stack structure on the drying rate are analyzed. • Relative humidity has a more significant effect on drying rate than temperature. [ABSTRACT FROM AUTHOR]

A novel non-intrusive thermal diffusion measurement (TDM) method has been proposed for measuring the phase flowrates of gas–liquid slug flows in our previous research. Since the structure of TDM was arbitrarily designed and needed to be optimized for accurate measurement, the effect of the heat flow distribution and the thermophysical properties of the pipe wall and fluid on the wall temperature response to a rising Taylor bubble (TB) is further investigated by using the CFD tool in this paper. The wall temperature and temperature rise are used to describe the wall temperature response, and their variation rules with heat flow distribution and the thermophysical properties of the pipe wall and fluid are presented and analyzed based on heat transfer. The simulation results indicate that the optimal heating length for a large wall temperature rise and small power consumption is 0.6 D , and the optimal pipe material should be with small density and specific heat and a suitable thermal conductivity of about 15 W/(m·K). Moreover, the wall temperature response is obvious, especially for TBs moving in the liquid with large fluid thermal conductivity, density, and specific heat, and small viscosity. The paper can clarify the wall temperature response mechanism of the heated pipe wall and provide a theoretical basis for the development of the TDM method. • Local instantaneous heat transfer characteristics of a rising TB are investigated. • Wall temperature responses under different heat flow distributions are presented. • Effect of wall/fluid thermophysical properties on temperature response is analyzed. • Titanium is the optimal metal for strong temperature response in the TDM method. • Optimal heating width is 0.6 D for strong response and energy saving. [ABSTRACT FROM AUTHOR]

The energy conversion and utilization of liquid metals is becoming one of the effective ways to solve energy problems. The conversion and transfer of thermal energy from liquid metals to water are significant in advanced nuclear energy and metallurgy. It has been an urgent concern, especially in Generation IV of advanced nuclear energy systems‑lead-cooled fast reactors and the ultimate energy source for humanity-fusion engineering. In this paper, a large-scale liquid metal and water interaction test platform was developed to investigate the lead‑bismuth liquid metal and water interaction and the cover gas pressurization characteristics. Firstly, the evolution of phase behavior and water/vapor migration paths were inferred based on the transient temperature law. Secondly, the cover gas pressurization patterns above the molten pool were analyzed, and the test data showed three pressurization patterns, including two types of local vapor explosions. Additionally, this paper predicted the existence of another dangerous pressurization mode, i.e., overall vapor explosion. Finally, the cover gas pressurization rate model was established, and there is an appropriate matching between the model and test data with an average relative error of 12.6%. This paper provides an essential reference for profoundly understanding the energy conversion and thermal interactions between liquid metals and water. • A large-scale liquid metal and water interaction test platform was developed to investigate energy conversion and interaction. • Based on the transient temperature law, we discovered the gas-phase evolution characteristics during lead-water interaction. • Three different types of pressurization patterns of cover gas were identified. • A model of cover gas pressurization was developed to predict the pressurization rate. [ABSTRACT FROM AUTHOR]

The energy sectors and chemicals depend heavily on shell & tube heat exchangers, which are also employed extensively in the modern manufacturing industry. Flow-induced noise has an important impact on how heat exchangers function. and should not be overlooked. Computational Fluid Dynamics (CFD) and acoustic-solid coupling are used in this paper to investigate the fluidic and vibration noise of tubes in shell & tube heat exchangers. In order to study the characteristic law of noise caused by flow, the flow and acoustic fields are combined in this research, with the flow field being estimated by accepting a large eddy simulation. A combination methodology of theoretical analysis and numerical simulation is utilized to analyze the influence of pipe type, pipe spacing, flow direction outside the pipe, flow velocity outside the pipe, and pipe length on noise. The results indicate that as the diameter of the pipe increases, the noise level rises, and with increasing pipe spacing, the noise decreases. The noise increases as the incidence angle of the fluid inflow increases. When flow rate accelerates, so does the noise. The study presented in this paper can serve as a theoretical and computational foundation for the design of shell & tube heat exchangers. [ABSTRACT FROM AUTHOR]

Verify the numerical model and physical mesh on the basis of the experiment, and then analyze the flow dynamics of the combustion chamber of the dual-stage counter-rotating swirler based on the verified numerical method. It is found that the flow dynamics of the combustion chamber of the dual-stage counter-rotating swirler is different from that of the single-stage swirler, which is affected by the change of the confinement ratio. With the increasing of confinement ratio, the flow field characteristics of combustion chamber with the dual-stage counter-rotating swirler presented in turn the axial growth flow pattern of reflux bubble (Rc ≤ 3.8), contraction flow pattern in the middle of reflux bubble (5.3 ≤ Rc ≤ 10.6) and double reflux bubble flow pattern (Rc ≥ 19.5). In addition, this paper defines the influence factor based on the change of confinement ratio, and quantitatively studies the degree of influence of the confinement ratio variation on the length of the return area of the combustion chamber. The work of this paper deepens the understanding of the physical mechanism that influences the flow and combustion by the confinement ratio, and also provides the improvement scheme for the optimization and design of the combustion chamber with dual-stage counter-rotating swirler. [ABSTRACT FROM AUTHOR]

The photoacoustic effect was explained more than half a century ago and has since been used to develop non-destructive and non-contact techniques for testing materials. Most existing experimental setups are time-consuming. In this paper, we deal with the development of time-resolved photoacoustics to use all the advantages of photoacoustic techniques in the development of real-time characterization of various samples. We propose a model for a time-resolved photoacoustic signal of thin samples measured in a gas-microphone setup with a minimal volume cell, assuming that the gas column in the cell can be shorter than the thermal diffusion length in air. The derived model additionally includes the influence of thermal relaxations and detector transfer function. We also suggest a methodology for inverse problem solving, i.e., to determine the sample properties from measured signals using the presented model. The model has been validated by comparing the model predictions with an experimentally measured signal for a thin metallic sample excited by an optical pulse train of a repetition rate of 12 Hz. The results obtained by the suggested inverse-problem solving methodology are in accordance with the literature, thus confirming the validity of the proposed methodology. We have shown that the proposed model and the methodology of inverse time-resolved photoacoustic problems give the same results as the widespread time-consuming frequency photoacoustic measurements. This means that the presented model and methodology enable the employment of low-frequency time-resolved gas-microphone photoacoustics in the real-time characterization of thin solids. [ABSTRACT FROM AUTHOR]

Mixing of surface microstructure and wettability is one of the future development trends. Their combination always affects the bubble motion and heat transfer coefficient under pool boiling/flow boiling, but it is difficult to distinguish their respective contributions. This work studies the combination of new microstructure and mixed wettability to improve the flow boiling heat transfer in the channel. The nucleation, growth, coalescence and departure behaviors of R134a boiling bubbles were numerically analyzed. Effects of different heights, gaps and mixed wettability of microstructures and heat fluxes on bubble emission frequency and boiling heat transfer coefficient were discussed. Results showed that this new microstructure provides the bubble with the momentum of lateral motion, which helps the bubble to merge and leave faster. The surface of the hydrophobic groove coupled with the hydrophilicity as the substrate can effectively increase the bubble emission frequency, up to 134.37%. At the same time, the heat transfer coefficient decreases with the increase of the height of the microstructure, and it also increases with the increase of the microstructure gap. Finally, the contribution of each variable was determined by analysis of variance. The research results in this paper provide a reference for heat pipe and vapor chamber. • A creative microchannels with mixed wettability was proposed and optimized. • Synergistic effect of groove microstructure and mixed wettability was studied. • Surface mixed wettability has more influence on boiling heat transfer. • Bubble emission frequency of surface-A is 134.37% higher than surface-B. [ABSTRACT FROM AUTHOR]

A novel double-wall-hole honeycomb seal (D-WHHCS) is proposed in this paper. D-WHHCS is designed based on a traditional honeycomb seal (HCS) by drilling double holes in the honeycomb sidewalls. The leakage characteristics of D-WHHCS are investigated via the computational fluid dynamics (CFD) method. The sealing performance of D-WHHCS under different seal clearances, wall hole positions, operating pressures and rotating speeds is studied. The sealing mechanism of D-WHHCS is revealed. The results show that D-WHHCS has better sealing performance than HCS under all the considered operating conditions, with a maximum leakage reduction of 3.95%. A fluid concentration effect when the axial cavity number (N) = 14 is observed in D-WHHCS, which causes a 9.16% improvement in the maximum turbulent kinetic energy compared with HCS at the outlet extension. A large vortex in the cavities of D-WHHCS with N = 14 is guided by the jets at the centerlines of the drilling hoes. The average turbulent dissipation in the cavities of D-WHHCS is a maximum increase of 95.30%, even though the vortexes in the cavities with N = 13 are weakened by the counteractive effect of two jets. The leakage reduction performance of D-WHHCS decreases with increasing clearance. An abnormal low-pressure region is produced in the first cavity because the intensive jet covers the first two cavities and suppresses the throttling effect of the first-stage honeycomb cavity. The leakage of D-WHHCS further decreases along with holes closing to rotor surface. • The leakage of double-wall-hole honeycomb seal (D-WHHCS) decreases 3.95%. • A fluid concentration effect is observed in the sealing gap of D-WHHCS. • A huge turbulent dissipation in unit cavities is observed in the D-WHHCS. • The sealing performance of D-WHHCS is weakened with seal gap increasing. • The smaller the distance between holes and rotor is, the larger the vortexes is. [ABSTRACT FROM AUTHOR]

This paper introduces the concept of "architectural ingenuity" to scientific discourse, elucidating its dynamic and evolving nature. It addresses the complexity inherent in integrating architectural design with applied and theoretical thermodynamics. Architectural paradigms, viewed through a thermodynamic lens, have evolved in response to climatic conditions over time. This evolution entails the optimization of architectural elements and configurations to maximize energy flow and adaptability to prevailing thermodynamic boundary conditions. "Architectural ingenuity", operating within a thermodynamic framework, optimizes efficiency by engaging with thermodynamic boundary conditions through elements like building orientation and materials. The constructal law provides a methodological scientific framework for integrating and analyzing historical legacies with architectural innovation, facilitating the evolution of "architectural ingenuity". "Climatic constructal heterotopia" epitomizes a novel fundamental architectural theory and a robust scientific methodology founded on thermodynamic principles. Through the synthesis of historical insights under the lens of principles such as entropy minimization, energy optimization, and flow dynamics within the constructal law framework, this concept aims to advance the evolution of sustainable architectural design practices. It places particular emphasis on their evolution over logarithmic time scales, reflecting a deep understanding of the intricate interplay between architecture and thermodynamics. In conclusion, this article strives to contribute a new perspective to the architectural theory discourse, unraveling the intricate interplay between "architectural ingenuity", natural principles, thermodynamics and the evolution of design that is governed by Adrian Bejan's constructal law. [ABSTRACT FROM AUTHOR]

In the heat transfer community, one-dimensional media refers to some media where the temperature and other thermophysical properties vary along one direction. Plane-parallel, concentric cylindrical, and concentric spherical geometries are among of regular one-dimensional media. In this paper, a general ray tracing approach is presented to track the curve paths of energy particles in regular one-dimensional variable index media. The domain of interest is limited by specular sidewalls and the medium is divided into slices with constant temperature and radiative properties. Then, the path of random energy particles emitted from boundary surfaces and volume elements are traced, element by element, until they absorb by diffuse-gray surfaces or the gray medium. After counting the number of absorbed particles by each boundary surface and volume element, the Monte Carlo method is performed to simulate thermal radiation heat transfer. The results are presented for three regular geometries, including plane-parallel, concentric cylindrical, and concentric spherical media, and the effects of radiative properties are investigated by some numerical experiments. [ABSTRACT FROM AUTHOR]

Nanofluid-microchannels have gained prominence in recent years as a means of cooling electronic devices; however, nanoparticle deposition remains a challenge. In this paper, a discrete phase model (DPM) is used to study the effects of various forces on nanoparticle deposition of Al 2 O 3 -water nanofluids in a straight microchannel. The results indicate that Brownian motion has a significant impact on nanoparticle deposition. For instance, when Cunningham values vary from 1.2 to 0.2, nanoparticle deposition ratios decrease from 8.69% to 3.41%. When the fluid velocity is <0.6 m/s, the thermophoretic force becomes crucial, whereas Saffman's lift force becomes important when the particle diameter is <10 nm. In addition, gravity and pressure gradient forces can be ignored. Virtual mass and drag forces impact deposition indirectly by changing residence times. Finally, a new correlation has been proposed for calculating particle deposition ratios. • A liquid-based deposition process differs from a gas-based deposition process. • Brownian motion has the greatest impact on nanoparticle deposition. • Thermophoretic and Saffman's lift forces become essential in certain conditions. • A new correlation was developed to determine particle deposition ratios. [ABSTRACT FROM AUTHOR]

This paper reviews the recent evolution of unmanned aerial vehicles (UAVs) through the lens of thermodynamic design. Emphasis is placed on using constructal theory in order to understand the relationship between different degrees of freedom within these complex dynamic systems. Size scale, the way in which UAVs are categorized based on weight and dimensions and one of the most significant factors in the design of any UAV, is analyzed in terms of its relationship to energy consumption. Specifically, constructal theory is used to predict the minimum size at which any UAV will need to be tethered in order to support its energy requirements. [ABSTRACT FROM AUTHOR]

In this paper, the condensation bubbles generated by the mixing and condensation of gaseous and liquid oxygen crossflow experimentally and theoretically. The mixing and condensation experiment of the bubbles was carried out, employing gaseous and liquid oxygen as working fluids in vertical tubes. Three successive flow patterns were observed: initial gas plume, condensation oscillation, and separation condensation. The corresponding characteristics include gas mass aggregation, bubble surface smoothness and wrinkling alternately, and bubble disappearance after separation and condensation. Then, a Nusselt number (Nu) heat transfer correlation formula is fitted with a corresponding fitting error in the range of −31% ∼ 35%. In addition, bubble force balance and conservation equations were employed to establish a mixing condensation bubble model suitable for gaseous and liquid oxygen in vertical tubes, and the error between theoretical and experimental results was in the range of −25% ∼ 20%. Furthermore, the effects of working conditions and forces on bubble condensation length has been analyzed. The results showed that increasing the liquid oxygen flow rate, reducing the gas oxygen volume flow rate, or appropriately reducing the gas inlet diameter led to reducing the bubble condensation length. It was shown that the bubble drag and shear lift forces affect the condensation length mostly. • First experiment of the oxygen bubble condensation in downward liquid oxygen flow. • Three flow patterns in bubble evolution is observed. • A theory model is established to predict the bubble condensation process. • A Nu correlation is fitted error in the range of −31% ∼ 35%. • Effect of forces on bubble evolution is analyzed theoretically. [ABSTRACT FROM AUTHOR]

In this paper, we present a comprehensive study on the heat transfer in the spiral coiled tubes, employing both numerical simulations and experimental analysis. The investigation includes an exploration of water flow at different mass flow rates, ranging from 0.025 to 0.11 kg / s , to capture a wide range of operating conditions. The numerical simulations were conducted using advanced computational fluid dynamics (CFD) techniques, providing detailed insights into the heat transfer behavior within the spiral tube. Concurrently, experimental tests were performed to validate the numerical results and compare them with existing findings from previous studies. The primary aim of our study is to establish correlations for calculating the Nusselt number and friction coefficient in the spiral coiled tubes. These correlations serve as essential tools for engineers and researchers in predicting heat transfer characteristics and pressure drop, thus facilitating the design and optimization of heat exchangers and heat recovery systems that incorporate spiral coiled tubes. Overall, the results obtained from this investigation enhance our understanding of heat transfer in spiral tubes and contribute to the development of reliable predictive models. The proposed correlations offer practical and efficient means of assessing heat transfer performance, making significant strides towards achieving more energy-efficient and sustainable industrial processes. • Fluid flow and heat transfer in a spiral coiled tube were studied. • Effects of mass flow rate of water on heat transfer in a spiral coiled tube were investigated. • Correlations for calculation of Nusselt number and friction coefficient for water flow in a spiral coiled tube were developed. [ABSTRACT FROM AUTHOR]

Cooling systems often rely on numerical calculations with precise heat transfer boundary conditions (HTBC), usually expressed as average values. The value of the average HTBC depends on the area in which they are determined. The paper presents a new approach showing the influence of the choice of the method of supplying liquid onto the surface on the non-uniformity of energy transfer from the cooled surface, which is important in the selection of the determination domain on the HTBC. The tests were carried out for two full-cone nozzles with different spray angles and two materials with different thermal properties. The local and average heat fluxes were determined for various distances of the nozzles from the surface and various liquid supply pressures. Cooling capacity, unevenness of energy transfer from the surface and quenching characteristics were evaluated and assessed using cooling curves. The study concludes that adopting HTBC based on average heat flux variation does not cause a significant error in the assessment of energy transfer during cooling with a nozzle with spray angle of 60° for EN 1.4845 steel. However, for Inconel and a nozzle with spray angle of 45°, the noticeable non-uniformity requires the application of a local HTBC. • Unevenness the spray cooling process. • Possibilities of using the average heat transfer boundary condition. • Recommendations for the use of local heat transfer boundary condition. [ABSTRACT FROM AUTHOR]

Fuel leakage and spill fires often occur during storage and transportation of liquid fuels. And the spread and burning processes of spill fires are susceptible to cross-air flows. In this paper, spill fire experiments were conducted on a fireproof glass (with or without ignition) under different wind speeds (0–2 m/s). The effects of wind on the spread process and burning behaviors were analyzed. Results showed that, for the cases without ignition, the spread length could vary in a non-linear manner with wind speed. And a spread length model was developed based on force analysis. For spill fires under small wind speeds, the burning area increased firstly, followed by a decrease before stabilization. When the wind speed exceeded a critical value, the fuel layer spread rapidly in the upwind direction after the shrinking phase. The steady stage was observed for all tests. With the wind speed increase, the quasi-steady burning area changes from being circular to elliptic first, before it gradually became circular in the end. To explain this process, a detailed heat transfer analysis was conducted. Considering the fuel layer shape and the heat transfer characteristics of spill fires, an analytical burning rate model was developed. • Wind drag force shows a significant effect on the spreading process for non-ignition continuous leakage tests. • Three typical spill fire spreading behaviors can be observed under different wind speeds. • The variation of the convective feedback with wind speed is primarily responsible for the change in the fuel layer shape. • An analytical model is developed based on the stagnant layer theory to calculate the burning rate of liquid fires. [ABSTRACT FROM AUTHOR]

This paper employs topology optimization techniques to enhance the performance of liquid-cooled plates while investigating the optimization process and its outcomes. A multilevel optimization strategy is implemented to refine the accuracy and smoothness of the optimization process. The study demonstrates that expanding the range of penalty factors and refining the granularity of penalty factors can effectively enhance the capability of multilevel optimization in suppressing the formation of intermediate densities. Furthermore, a multi-objective function is utilized to strike a balance between the heat transfer efficiency and the hydraulic performance of the liquid-cooled plate. Ultimately, after considering aspects related to heat transfer and hydraulic performance, the research finds that compared to traditional straight-channel liquid-cooled plates, liquid-cooled plates featuring streamlined multi-branched flow channels not only increase the heat transfer area but also reduce pressure drop. As a result, this design improves the temperature uniformity of the liquid-cooled plate and enhances the velocity uniformity of the cooling fluid. At different inlet velocities, the topology-optimized liquid-cooled plate exhibits a reduction in both effective thermal resistance and pumping power compared to the traditional straight-channel liquid-cooled plate. • Multi-level optimization strategy improves the smoothness and precision of the topology optimization process. • Expanding the penalty factor range and refining granularity helps to reduce the intermediate density in the topology process. • Topology-optimized liquid-cooled plates improves the uniformity of coolant velocity and temperature distribution. [ABSTRACT FROM AUTHOR]

The porous microchannel heat sink can be used to meet the increasing demand for electronic device cooling. In this paper, heat transfer is enhanced by optimizing heat flux distribution for porous microchannel heat sinks subject to an exponential heat flux. The Nusselt number, dimensionless wall temperature and thermal resistance are obtained using the semi-analytical method. The Nusselt number is found to be dependent on the product of dimensionless exponent, Reynold number, and Prandtl number. The optimal heat flux distribution is dependent on the length of the channel and it is that under constant wall temperature boundary condition in most cases. The thermal performance is assessed using the thermal resistance ratio between constant wall temperature and constant heat flux boundary conditions. An optimal length exists when the constant wall temperature condition is used to reduce the maximum wall temperature. The effects of Biot number and the ratio between effective thermal conductivities of solid and fluid phases on the minimum value of the thermal resistance ratio and the optimal length are also studied. The result shows that the thermal resistance can be reduced by about 28% by optimizing the heat flux distribution, compared with the commonly used constant heat flux boundary condition. • Heat transfer for porous heat sinks is enhanced by optimizing wall heat flux. • The optimal heat flux distribution is that for CWT conditions in most cases. • An optimal length is found when the constant temperature conditions is used. • The thermal resistance can be reduced by about 28%. [ABSTRACT FROM AUTHOR]

The inverse heat transfer problems (IHTP) have a wide range of applications in the engineering field. Bayesian methods using Markov Chain Monte Carlo (MCMC) have long been considered as a robust and effective method for solving inverse problems. However, the discretization of the problem domain by the spatio-temporal Galerkin skill, i.e., the finite element interpolation also includes the time dimension, making the scale of the unknown parameters extremely difficult for Bayesian calculations. In this paper, a fast Bayesian parallel sampling (FBPS) framework is proposed for large-scale parameter estimation of benchmark three-dimensional inverse heat transfer problems (3D-IHTP). The FBPS we developed achieves a parameter computation scale of 10 5 magnitude within minutes, through dimensionality reduction of the space-time dependent problem domain. The Hamiltonian Monte Carlo (HMC) sampler, which is proven to be more efficient for high-dimensional parameter estimation, is employed. Through several simulation tests of IHTP, it was confirmed that the solving efficiency of FBPS surpasses that of the traditional Bayesian strategy significantly. Finally, FBPS is successfully developed to estimate the unknown heat flux on the chip heat sink and pack interface effectively, given some simulated high resolution measurement data. The reliability and efficiency show that FBPS has the potential to support efficient prediction techniques for a class of IHTPs in engineering applications. • A fast Bayesian parallel sampling framework (FBPS) for 3D-IHTP is proposed. • Computation time to solve IHTP with unknown size of 105 is in minute level. • FBPS is about 55 times faster than the traditional Gibbs method. • FBPS provides reliable technical idea to solving large-scale Bayesian inverse problem. • FBPS is applied to the inverse problem of chip packaging heat dissipation. [ABSTRACT FROM AUTHOR]

Changing the inner tube shape proves to be an effective method to enhance the efficiency of horizontal latent heat thermal energy storage exchangers (H-LHTES), which can improve the heat transfer efficiency of exchangers. This paper proposed an I-beam inner tube exchanger, which contained I-1 and I-2 types, then under the constant mass of phase change material, the charging and discharging performance of the H-LHTES with I-beam, circular, rectangular and rhombic inner tube shapes were comparatively investigated using FLUENT numerical simulation software. The results demonstrated that compared with the circular inner tube, the charging and discharging time reduces remarkably for the H-LHTES with I-beam, rectangular and rhombic inner tubes, and the I-beam inner tube shows the best enhancement effect, additionally, the I-1 has the shortest total time at the inner tube height of 74.8 mm, the charging and discharging time reduces by 82.41% and 43.56%, the total time decreases by 50.46%, the rectangular and rhombic inner tubes have the shortest total time at the inner tube height of 82.8 mm and 90.8 mm, the total time decreases by 34.7% and 36.99%, respectively. The results can supply a reference for the optimal design of inner tube shape of the H-LHTES. [ABSTRACT FROM AUTHOR]

In the thermal management of fuel cell vehicles, radiators are subjected to vibrations due to vehicle speed and road surface irregularities. However, there has been no comprehensive study of the impact of these vibrations on the heat transfer performance of radiators. Therefore, this paper employs R141b to conduct three-dimensional transient numerical simulations of flow boiling in small channels under vertical vibrations. The study reveals that the single-phase heat transfer coefficient exhibits periodic variations. At the same vibration frequency, the heat transfer frequency for the vertically oriented heating surface is twice that of the horizontally oriented surface, This is because the thermal boundary layer varies with the vibration velocity. Furthermore, as the frequency increases to 21 Hz, the time-averaged heat transfer coefficient can increase by up to 2.5 times. Following boiling onset, for horizontally oriented heating surfaces, an increase in frequency or amplitude enhances the transient heat transfer performance. Under the conditions of 28 Hz and 5 mm, the heat transfer coefficient can increase by 125.7%. However, for vertically oriented heating surfaces, when the frequency exceeds 14 Hz or the amplitude exceeds 8 mm, the heat transfer performance weakens after 7.143 s due to the promotion of bubble coalescence by the vibrations. [ABSTRACT FROM AUTHOR]

Supercritical water gasification provides a new approach to the green transformation of coal. Nevertheless, the flow characteristics of fluids and particles injected into the reactor through the nozzle still need to be further investigated. In this paper, a three-dimensional numerical simulation of the particle jet in supercritical water environment is carried out coupling Large Eddy Simulation (LES) with Discrete Phase Model (DPM). The simulation focuses on the effects of particle size, Stokes number, mass flux ratio and initial fluid velocity on the flow characteristic of the fluid-particle flow, especially on the vortex structure evolution, particle distribution and velocity profile. The findings are that as the particle size decreases and the initial fluid velocity increases, the evolution of vortex structures become increasingly fierce, such as the destruction of large-scale coherent structures, the disappearance of vortex ribs, and the lateral expansion of vortices in the development section. Particle distribution exhibits characteristics similar to the vortex structure, as particles adhere closely to the carrier fluid at low Stokes number (St < 1). On the contrary, with increasing of Stokes number (St > 1), the particles are freer from fluid interference and keep their original motion state moving forward. The fluid velocity at the center of the transverse interface jet decrease with increased mass flow ratio. For higher initial fluid velocities, particle distribution is more uniform, and more particles are carried to areas with larger radial distances. [ABSTRACT FROM AUTHOR]

The inundation of the lower tubes in a tube bundle with condensate formed on the upper tubes is among the major causes of reduced condensation rate. Experimental methods can hardly be used to get detailed information on the inundation effect, since each factor that controls the condensation process should be considered individually. However, CFD modelling using direct interface-tracking methods is an effective tool for analyzing such processes. This paper reports the results of simulation of the saturated propane vapor condensation on the surface of a horizontal tube using the Volume of Fluid method with the modified Lee model. The study presents, for the first time, the characteristics of saturated vapor condensation including the effect of inundation predicted using a 3D model. The interphase surface and the distribution of instantaneous heat transfer coefficients over the surface of the inundated pipe are presented. It has been shown that increasing the temperature of the condensate flow can substantially affect the distribution of the heat transfer rate over the tube surface due to the formation of a thermal entrance region. These results may become a starting point for modelling condensation in a tube bundle that enjoys current interest in practice. [ABSTRACT FROM AUTHOR]

This paper outlines and discusses the thermal conductivity of 1-Butyl-3-methylimidazolium tetrafluoroborate ionic liquid, as well as three classes of nanocolloids. The [C4mim][BF4] ionic liquid was enhanced with three kinds of nanoparticles, Al 2 O 3 , ZnO and MWCNT and all fluids thermal conductivity was experimentally measured. Results discussion includes also an in-depth analysis on Prandtl number and thermal diffusivity. All the data were carefully debated in terms of state of the art advancement and these suspensions suitability for practical applications in heat transfer. It was found that the thermal conductivity increases with nanoparticles addition and this enhancement depends on nanoparticle type and temperature. Plus, the temperature influence is rather limited, while the consideration on Prandtl number and thermal diffusivity revealed that it is extremely relevant to consider all the thermophysical properties when choosing a new thermal fluid. Additionally, a comparison with well known correlations was inserted, concluding that no theory can estimate the ionic liquids nanocolloids thermal conductivity. Concluding, the thermal properties of [C4mim][BF4] ionic liquid and its nanocolloids with Al 2 O 3 , ZnO and MWCNT shows that these nanocolloids uncover great potential for heat transfer applications. • 1-Butyl-3-methylimidazolium tetrafluoroborate thermal conductivity is experimental determined. • The thermal conductivity of nanocolloids is debated in terms of nanoparticle mass fraction and temperature. • Thermal conductivity correlations are anticipated for [C4mim][BF4] and its nanocolloids. • The thermal diffusivity and Pr number of nanocolloids based on [C4mim][BF4] follow an in depth discussion. [ABSTRACT FROM AUTHOR]