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This paper aims to analyze the friction heat conduction and entransy of two friction linings in the high‐speed slide accident of a mine friction hoist.

Firstly, the dynamic thermophysical properties were analyzed and their fitting equations were also obtained. Additionally, the dynamic heat partition ratio was obtained according to the dynamic thermophysical properties. Then, a simple method was developed to solve the temperature rise of friction lining. Finally, based on the theoretical model of temperature rise, the entransy of friction lining with respect to T and t were gained.

The error of temperature rise between simulation result and experiment result is less than 7 per cent, which proves that the theoretical model is correct. The entransy decreases with the temperature below 40°C and it increases after 40°C. The entransy of lining K is a little higher than that of lining G within 19 s, but the entransy of lining G is much higher than lining K after 19 s and the entransy difference gets great gradually. It is indicated that the lining K has good heat‐resistant property which is of great benefit to the tribological property of friction lining.

The authors' study provides a fundamental basis for developing a new friction lining with good heat‐resistant property, and it also brings forward a new quantitative method to evaluate the heat‐transfer capability of friction materials.

A simple method was introduced to calculate the temperature rise of friction lining with the consideration of dynamic thermophysical properties and dynamic heat partition ratio. And the entransy of friction lining was obtained to evaluate the heat‐transfer capability of friction linings quantitatively.

The purpose of this paper is to carry out a numerical investigation to study laminar convection flow of Al₂O₃-water nanofluids within a three-dimensional rectangular section channel asymmetrically heated.

A three-dimensional model of the channel is designed and simulated by using Comsol Multiphysics. The finite elements method is used to perform the numerical simulation. A variety of cases are taken into account by considering Reynolds numbers ranging from 250 up to 1,000, concentration between 0 and 6 per cent, particle dimension of 20, 40 and 60 nm and inlet temperature equal to 293.15 and 320 K. A constant heat flux of 1,000 W/m² is imposed on the top surface of the channel.

The results demonstrate that nanofluids guarantee improved thermal performances with respect to the base fluid, as shown by the augmented Nusselt number. On the other hand, pressure drop shows a noticeable increase; therefore, an entropy generation analysis is developed to establish optimal conditions for the system under investigation.

The originality of this work consists in the analysis of a three-dimensional asymmetric heated channel with nanofluids in laminar convection. The present work would be beneficial to improve the design of devices with particular focus on solar thermal panel.

This paper aims to present a numerical study that investigates the flow of MgO-Al₂O₃/water hybrid nanofluid inside a porous elliptical-shaped cavity, in which we aim to examine the performance of this thermal system when exposed to a magnetic field via heat transfer features and entropy generation.

The configuration consists of the hybrid nanofluid out layered by a cold ellipse while it surrounds a non-square heated obstacle; the thermal structure is under the influence of a horizontal magnetic field. This problem is implemented in COMSOL multiphysics, which solves the related equations described by the “Darcy-Forchheimer-Brinkman” model through the finite element method.

The results illustrated as streamlines, isotherms and average Nusselt number, along with the entropy production, are given as functions of: the volume fraction, and shape factor to assess the behaviour of the properties of the nanoparticles. Darcy number and porosity to designate the impact of the porous features of the enclosure, and finally the strength of the magnetic induction described as Hartmann number. The outcomes show the increased pattern of the thermal and dynamical behaviour of the hybrid nanofluid when augmenting the concentration, shape factor, porosity and Darcy number; however, it also engenders increased formations of irreversibilities in the system that were revealed to enhance with the permeability and the great properties of the nanofluid. Nevertheless, this thermal enhanced pattern is shown to degrade with strong Hartmann values, which also reduced both thermal and viscous entropies. Therefore, it is advised to minimize the magnetic influence to promote better heat exchange.

The investigation of irreversibilities in nanofluids heat transfer is an important topic of research with practical implications for the design and optimization of heat transfer systems. The study’s findings can help improve the performance and efficiency of these systems, as well as contribute to the development of sustainable energy technologies. The study also offers an intriguing approach that evaluates entropy growth in this unusual configuration with several parameters, which has the potential to transform our understanding of complicated fluid dynamics and thermodynamic processes, and at the end obtain the best thermal configuration possible.

The aim of this work is to determine the average surface temperature of a conical antenna. Its cooling is ensured by means of a nanofluid-saturated porous structure. The volume fraction of the H₂O–Cu nanofluid ranges between 0% (pure water) and 5%, whereas the ratio between the thermal conductivity of the used porous materials and that of water (fluid base) varies in the wide 4–41.2 range. The antenna is contained in a coaxial conical closed cavity with a variable distance between the cones, leading to an aspect ratio varying between 0.2 and 0.6. The axis of the assembly is also inclined with respect to the gravity field by an angle varying between 0° (a vertical axis with top of the cone oriented upwards) and 180° (a vertical axis with top of the cone oriented downwards).

Simulations have been done by means of the volume control method based on the SIMPLE algorithm.

Results of the numerical approach show that the cavity’s aspect ratio and inclination with respect to the gravity field significantly affect the thermal behavior of the active cone. Otherwise, the work confirms that the Maxwell and Brinkman models used to determine the nanofluid’s effective thermal conductivity and viscosity, respectively, are adapted to the considered assembly.

A new correlation is proposed, allowing the determination of the average surface temperature of the active cone and its correct thermal sizing. This correlation could be used in various engineering fields, including electronics, examined in the present study.

The purpose of the paper is to conduct a numerical and experimental investigation into the properties of nanofluids containing spherical nanoparticles of random sizes flowing through a porous medium. The study aims to understand how the thermophysical properties of the nanofluid are affected by factors such as nanoparticle volume fraction, permeability of the porous medium, and pore size. The paper provides insights into the behavior of nanofluids in complex environments and explores the impact of varying conditions on key properties such as thermal conductivity, density, viscosity, and specific heat. Ultimately, the research contributes to the broader understanding of nanofluid dynamics and has potential implications for engineering and industrial applications in porous media.

This paper investigates nanofluids with spherical nanoparticles in a porous medium, exploring thermal conductivity, density, specific heat, and dynamic viscosity. Studying three compositions, the analysis employs the classical Maxwell model and Koo and Kleinstreuer’s approach for thermal conductivity, considering particle shape and temperature effects. Density and specific heat are defined based on mass and volume ratios. Dynamic viscosity models, including Brinkman’s and Gherasim et al.'s, are discussed. Numerical simulations, implemented in Python using the Langevin model, yield results processed in Origin Pro. This research enhances understanding of nanofluid behavior, contributing valuable insights to porous media applications.

This study involves a numerical examination of nanofluid properties, featuring spherical nanoparticles of varying sizes suspended in a base fluid with known density, flowing through a porous medium. Experimental findings reveal a notable increase in thermal conductivity, density, and viscosity as the volume fraction of particles rises. Conversely, specific heat experiences a decrease with higher particle volume concentration.xD; xA; The influence of permeability and pore size on particle volume fraction variation is a key focus. Interestingly, while the permeability of the medium has a significant effect, it is observed that it increases with permeability. This underscores the role of the medium’s nature in altering the thermophysical properties of nanofluids.

This paper presents a novel numerical study on nanofluids with randomly sized spherical nanoparticles flowing in a porous medium. It explores the impact of porous medium properties on nanofluid thermophysical characteristics, emphasizing the significance of permeability and pore size. The inclusion of random nanoparticle sizes adds practical relevance. Contrasting trends are observed, where thermal conductivity, density, and viscosity increase with particle volume fraction, while specific heat decreases. These findings offer valuable insights for engineering applications, providing a deeper understanding of nanofluid behavior in porous environments and guiding the design of efficient systems in various industrial contexts.

This paper aims to examine the Cu-Al2O3/water hybrid nanofluid flow over a shrinking sheet in the presence of the magnetic field and dust particles.

The governing partial differential equations for the two-phase flow of the hybrid nanofluid and the dust particles are reduced to ordinary differential equations using a similarity transformation. Then, these equations are solved using bvp4c in MATLAB software. The bvp4c solver is a finite-difference code that implements the three-stage Lobatto IIIa formula. The numerical results are gained for several values of the physical parameters. The effects of these parameters on the flow and the thermal characteristics of the hybrid nanofluid and the dust particles are analyzed and discussed. Later, the temporal stability analysis is used to determine the stability of the dual solutions obtained as time evolves.

The outcome shows that the flow is unlikely to exist unless satisfactory suction strength is imposed on the shrinking sheet. Besides, the heat transfer rate on the shrinking sheet decreases with the increase of . However, the increase in and lead to enhance the heat transfer rate. Two solutions are found, where the domain of the solutions is expanded with the rising of, and. Consequently, the boundary layer separation on the surface is delayed in the presence of these parameters. Implementing the temporal stability analysis, it is found that only one of the solutions is stable as time evolves.

The dusty fluid problem has been widely studied for the flow over a stretching sheet, but only limited findings can be found for the shrinking counterpart. Therefore, this study considers the problem of the dusty fluid flow over a shrinking sheet containing Cu-Al₂O₃/water hybrid nanofluid with the effect of the magnetic field. In fact, this is the first study to discover the dual solutions of the dusty hybrid nanofluid flow over a shrinking sheet. Also, further analysis shows that only one of the solutions is stable as time evolves.

The use of alternative oils for the lubrication of automobile engines has a potential of ecological and technical advantages. It requires the detailed knowledge of several thermophysical and viscosimetric properties in a large temperature range.

For 11 different oils, the density, the heat capacity, the thermal conductivity, the viscosity at ambient pressure and the pressure‐viscosity at maximal 1,000 bar have been measured. The latter has been measured with a newly developed apparatus which is described in detail. Two hydrocarbon‐based factory‐fill oils and nine alternative oils have been tested. Five of the alternative oils are based partly or completely on esters, the other four on polyglycols, one of them additionally on water.

Data for thermophysical and viscosimetric properties are given in form of diagrams and tables. The consequences for the cooling capacity and the film forming behavior are discussed. The latter is only slightly better for the factory‐fill oils, compared to the alternative oils.

The pressure‐viscosity is measured at up to 1,000 bar, which is lower than the maximum pressure in the tribological contacts of an engine.

The published data can be used to calculate tribological contacts which are lubricated with alternative engine oils or with actually used factory‐fill oils. This might help to decide if esters or polyglycols are superior as engine oils.

The results of this test program might be helpful for engineers who are interested in using alternative lubricants in tribosystems.

This paper aims to study forced convection in a double tube heat exchanger using nanofluids with constant and variable thermophysical properties.

The cold fluid was distilled water flowing in the annulus and the hot fluid was aluminum oxide/water nanofluid which flows in the inner tube. Thermal conductivity and viscosity were taken as variable thermophysical properties, and the results were compared against runs with constant values. Finite volume method was used for solving the governing equations. For distilled water, Re = 500 was used, while for nanofluid, nanoparticles volume fraction equal to 2.5-10 per cent and Re = 100-1,500 were used.

Heat transfer rate can be enhanced by increasing the volume fraction of nanoparticles and Reynolds number. Thermal efficiency is better with constant thermophysical characteristics and the average Nusselt number is better for variable characteristics.

Heat exchanger efficiency is evaluated by using distilled water and nanofluid bulk temperature, thermal efficiency and average and local Nusselt numbers for both variable and constant thermophysical characteristics.

This paper aims to evaluate the dynamic viscosity and thermal conductivity of halloysite nanotubes (HNTs) suspended in SAE 5W40 using machine learning methods (MLMs).

A two-step method with surfactant was selected to prepare nanolubricants in concentrations of 0.025, 0.05, 0.1 and 0.5 wt%. Thermal conductivity and dynamic viscosity of nanofluids were ascertained over the temperature range of 25–70 °C, with an increment step of 5 °C, using a KD2-Pro analyser device and a digital viscometer MRC VIS-8. Additionally, four different MLMs, including Gaussian process regression (GPR), artificial neural network (ANN), support vector machine (SVM) and decision tree (DT), were used for predicting dynamic viscosity and thermal conductivity by using nanoparticle concentration and temperature as input parameters.

According to the achieved results, the dynamic viscosity and thermal conductivity of nanolubricants mostly increased with the rise of nanoparticle concentration in the base oil. All the proposed models, especially GPR with root mean square error mean values of 0.0047 for dynamic viscosity and 0.0016 for thermal conductivity, basically showed superior ability and stability to estimate the viscosity and thermal conductivity of nanolubricants.

The results of this paper could contribute to optimising the cost and time required for modelling the thermophysical properties of lubricants.

To the best of the author’s knowledge, in this available literature, there is no paper dealing with experimental study and prediction of dynamic viscosity and thermal conductivity of HNTs-based nanolubricant using GPR, ANN, SVM and DT.

This paper aims to address the coating and compound analysis of diamond-like carbon (DLC) on steel, to understand the frictional behavior in tribological gear systems presented in paper Part I. Here, the Ti and Zr modified DLC coating architectures are analyzed regarding their chemical, mechanical and thermophysical properties. The results represent a systematic analysis of the thermal insulating effect in tribological contact of DLC coated gears.

The approach was to evaluate the effect of the substitution of Zr through Ti at the reference coating ZrCg to TiCg and the effect on thermophysical properties. Furthermore, the influence of different carbon and hydrogen contents on the coating and compound properties was analyzed. Therefore, different discrete Ti or Zr containing DLC coatings were deposited on an industrial coating machine. Thereby the understanding of the microstructure and chemical composition of the reference coatings is increased.

Results prove comparable mechanical properties of metal modified DLC independent of differences in chemical compositions. Moreover, the compound adhesion between TiC_g/16MnCr5E was improved compared to ZrC_g/16MnCr5E. The effect of hydrogen content Ψ and carbon content x_c on the thermophysical properties is limited by Ψ = 18 at.% and x_c = 90 at.%.

The findings of the combined papers Part I and II show a high potential for industrial application of DLC on gears. Based on the results DLC coatings and gears can be tailored to each other.

Systematic analysis of DLC coatings were conducted to evaluate the effect of titanium, carbon and hydrogen on thermophysical properties.