Heat Source Intensity Research Articles

MATHEMATICAL MODEL OF THE PROCESS OF DRYING WALNUTS IN A CONVECTIVE-VIBRATION DRYER

Obtaining high-quality walnuts must necessarily involve drying them to a conditioned moisture content of 10%. To achieve this goal, dryers of various types and designs are used, but convective dryers with various upgrades to intensify the drying process are the most common. To implement the drying process with the highest possible efficiency, it is necessary to know the regularities of the course of events occurring inside the drying equipment, that is, according to what laws the interaction of the drying agent and the material occurs. Simply put, you need to get a mathematical model of the process of drying walnuts in a convective-vibration dryer. The analysis of recent studies and publications shows that despite the significant variety of measures and means for the implementation of the convective drying process, all of them have the development of a mathematical model of the process as one of the stages of the study. In most cases, the mathematical model describes the interaction between the drying agent and the material to be dried. Before starting work on the creation of a mathematical model of drying, some assumptions were made, including the constancy of thermophysical characteristics and the coefficient of heat transfer during the entire drying process. To adequately describe the change in the amount of moisture in the material, the concept of negative internal heat sources was applied, which is equivalent to the current moisture content of the material and depends on its initial humidity and the operating parameters of the process. The solution of the equation of non-stationary thermal conductivity was carried out analytically by the operational method. The solution of the equation of the non-stationary process of thermal conductivity, taking into account the potential change in the intensity of negative internal heat sources in time, made it possible to obtain an equation by which it is possible to determine the temperature of the material at an arbitrary point of the nut volume depending on the drying exposure. The obtained equation makes it possible to adequately simulate the process of drying walnuts in a convective-vibration dryer and control the change in the temperature of the material to ensure the high quality of the final product.

Long-term operational characteristics of subway source heat pump system under various tunnel internal heat source intensities

In recent years, subway systems have effectively alleviated urban traffic congestions. However, thermal pollution of underground spaces is a prevailing problem, which poses a serious threat to the safe and efficient operation of subways. The subway source heat pump system (SSHPS), equipped with a front-end tunnel lining heat exchanger, is an effective solution to tackle the aforementioned problem. However, the design methodology and operational strategy of the system is not yet established, which necessitates an analysis of its long-term operational characteristics. In this study, an SSHPS simulation model was developed using the TRNSYS simulation tool based on a demonstration project and the model was subsequently validated against measured data. The validated model was used to evaluate the long-term performance and operational characteristics of the subway system under various internal heat source intensities ranging from 0 W/m to 240 W/m. The simulation results showed that the tunnel air temperature steadily increased as the internal heat source intensity increased. When the internal heat source was 0 W/m, the average annual decrease in tunnel air temperature was 0.11 °C. However, the average annual tunnel air temperature did not fall below the minimum subway design specification temperature of 5 °C at any point in time. When the internal heat source was 120, 180, and 240 W/m, the tunnel air temperature exceeded the maximum temperature of 40 °C stipulated in subway design guidelines on multiple occasions. As the internal heat source intensity increased, the performance of both the heat pump unit and SSHPS progressively decreased during the cooling season and gradually increased during the heating season. The runtime of the heat pump unit gradually decreased from 92.72 % to 77.57 % during the cooling season, whereas it increased from 46.92 % to 89.41 % during the heating season. The heat pump unit exhibited an average energy efficiency ratio (EER) of 5.07, 4.95, 4.87, 4.80 and 4.76 whereas the SSHPS demonstrated an average EER of 3.04, 3.01, 3.00, 2.99 and 2.98. Throughout its operational years, the SSHPS consistently maintained stable and cyclically high performance. However, the system did not fully meet the specified cooling and heating loads under all operational conditions, indicating that there was a source–load mismatch issue within the system. Hence, it is recommended to incorporate auxiliary cold and heat sources, thereby establishing a composite heating and cooling system based on subway source heat pump technology, with the aim of enhancing the reliability of energy supply for the system. This study can serve as a valuable reference for formulating high-efficiency and energy-saving operational strategies for SSHPSs.

A semi-analytical method based on the Green's function for the laser melting process of the metal materials

Thermal responses of the metal materials subjected to intense laser irradiation are complicated due to the phase change in the melting process. In order to simplify this problem, previous studies usually ignored the liquid phase or took the usage of finite element method, which limited the achievement of theoretical breakthroughs. In the present study, a one-dimensional heat transfer model with consideration of phase change was established to describe the melting process of the metal materials caused by a constant intense laser beam. The governing equations with three domains were constructed in the piecewise form: the liquid phase region (melted already), the solid phase region (unmelted yet) and the melting region. The limited discretization method was employed to describe the moving of the soli-liquid interface and the energy exchange. The piecewise governing equations in liquid and solid region were solved separately and analytically by means of the Green's function method, and the calculation result was verified by the finite element simulation. The results of the analytical model were in good agreement with those of the finite element simulation, and the maximal prediction errors of the temperature field prediction between the theoretical model and FE simulation is limited to 2.8 %. In addition, the influences of heat source intensity, material heat conductivity, latent heat on the melting process were discussed in detail. The analytical and simulation results reveal that the semi-analytical solution in piecewise for 1-D laser melting process can be successfully used to reflect the dynamic temperature response of the metal materials and the movement of the solid-liquid interface. This work is of guiding significance for the analytical solution of the multi-dimensional melting process of the metal materials under the fixed and continuous laser beams.

Flow-field characteristics of the thermal plume above an elliptical high-temperature heat source surface

The thermal plume formed by the high-temperature elliptical heat source surface during the smelting process is often captured and removed by the local exhaust system. Accurately mastering the flow-field characteristics of such high-temperature elliptical heat plumes is helpful for efficient design of local exhaust systems. In this paper, the effects of the ratio of long and short axes (5/4 ≤ ξ ≤ 5/1) and the intensity of heat source (80 ≤ F ≤ 160 W) on the axial and radial velocity distribution of thermal plume in an elliptical heat source are investigated by numerical simulation combined with experimental validation. The results show that in the range of ξ ≤ 5/1, the axial dimensionless velocity distribution of the elliptical plume field and the spreading range of the plume field are mainly affected by ξ instead of F. For 5/4 ≤ ξ ≤ 5/1, the maximum axial velocity Um appears at 1.7 to 2.7 times Z/L (plume height to heat source long axis ratio). For ξ ≤ 5/2, the height at which the cross-sectional velocity field transitions to a circular distribution aligns with the height of Um. It is found that the plume velocity field is characterized by applying the point source model for ξ ≤ 5/3, and vice versa for the linear source model. The plume flow rate formulation obtained by modifying the linear source model for ξ > 5/3 has a better predictive ability in the Z/L ≤ 5 region. This study provides a reference for the design of ventilation systems for elliptical surface heat sources.

Simulation study on the impact of heat source intensity on the inhaled air quality of an innovative personalized air supply method

Abstract To improve the local microenvironment of the human body in industrial buildings with strong heat sources, this paper proposes a new personalized air supply method based on the attachment effect. The numerical simulation method is used to study the influence of heat source intensity on the inhaled air quality in this paper. Studies have shown that when the air supply speed is less than or equal to 0.5 m/s, the fresh air ratio decreases as the Gr number of the heat source increases. When the air supply speed is greater than or equal to 0.7 m/s, the fresh air ratio increases as the Gr number of the heat source increases.

Investigation on temperature control performance of an underground confined space under ventilation

The control of thermal environment in underground structures has always been a subject of great concern. In this paper, the influence of initial surrounding rock temperature (ISRT), ventilation temperature (VT) and ventilation volume (VV), as well as internal heat source intensity (HSI) on the temperature control of ventilation risk in underground closed space is explored by building a 50-person Mine refuge chamber (MRC) model with internal heat source. The model is verified according to the experimental data, and the relative deviation is less than 4.3 %. The simulation results show that the indoor temperature (IT) is proportional to the ISRT, HSI and VT, but inversely proportional to the VV. When there are 30 people in the MRC, the ISRT and the initial IT are 32 °C, the VT is 20 °C, and the VV should exceed 450 m3/h to meet the temperature control requirements of 96 h. Taking into account the comfort of personnel, it is recommended that the air volume of 900 m3/h is more appropriate for 30 people.

Analytical model of modified diamond tools temperature by focused ion beam in dry diamond turning

The contact process between the chip and the rake face is directly affected by the temperature of the rake face, and then tool wear and machining quality is indirectly influenced by it. In this study, a temperature prediction model for the rake face of modified diamond tools during dry turning of the 6061 aluminum alloy was established based on the moving heat source method. The shear heat source, rake face chip friction heat source, cutting edge-workpiece ploughing effect heat source, cutting edge workpiece roll burnishing heat source, and flank face workpiece elastic recovery heat source were considered by this model during the dry diamond turning, simultaneously considering the non-uniformity of heat source intensity and heat distribution ratio, as well as the influence of ion implantation on the temperature of the tool rake face. The experimental results indicate that this model successfully predicts the temperature of the modified tool rake face, and it is found that an increase in dose will promote a decrease in the temperature of the rake face. Theoretical analysis reveals that modified cutting tools have the characteristic of reducing the temperature of the rake face, revealing the essence of the influence of “modification” on the temperature of the rake face from the perspective of the cutting mechanism, and providing a theoretical basis for optimizing modification parameters.

PIV experimental study on natural convective flows at high Rayleigh numbers in industrial buildings

High heat loads in industrial buildings potentially form strong natural convective flows. These flows exhibit significant unsteadiness and anisotropy, which can profoundly impact indoor air distribution. To study the flow characteristics of thermal convective flows in large indoor spaces, we built a large-scale test bench with controllable thermal boundaries. Under three different heat source intensities represented by Rayleigh numbers (Ra = 3 × 1010, 6 × 1010, and 1 × 1011) that are typical in industrial buildings, we used 2-dimensional particle image velocimetry to capture the large-scale convective airflow by splicing nine subregions, each with 800 instantaneous flow fields sampled at a frequency of 3 Hz. The results show that the convective airflow exhibited large-scale circulation patterns. The velocity near the wall gradually increased with the increased Ra number, while the velocity at the center remained low. The turbulence intensity near the wall was less than 1, while that at the center was larger than 5 and fluctuated greatly. The dominant fluctuation frequency of the airflow under the high Ra was 0.1 Hz. Through proper orthogonal decomposition, it is found that even for horizontal flows, the main transient fluctuations still exhibit an up-and-down fluctuating flow structure. Additionally, the calculation of the velocity structure function revealed that the airflow near the wall is anisotropic, while the airflow at the center is isotropic. The Reynolds number of the flow generated by vertical temperature differences exhibits a power function relationship with the Rayleigh number. This study provides a basis for the optimization of air distribution design in industrial buildings.

The significance of chemical reaction, thermal buoyancy, and external heat source to optimization of heat transfer across the dynamics of Maxwell nanofluid via stretched surface

Energy loss during the transportation of energy is the main concern of researchers and industrialists. The primary cause of heat exchange gadget inefficiency during transportation was applied to traditional fluids with weak heat transfer characteristics. Instead, thermal devices worked much better when the fluids were changed to nanofluids that had good thermal transfer properties. A diverse range of nanoparticles were implemented on account of their elevated thermal conductivity. This research addresses the significance of MHD Maxwell nanofluid for heat transfer flow. The flow model comprised continuity, momentum, energy transport, and concentration equations in the form of PDEs. The developed model was converted into ODEs by using workable similarities. Numerical simulations in the MATLAB environment were employed to find the outcomes of velocity, thermal transportation, and concentration profiles. The effects of many parameters, such as Hartman, Deborah, buoyancy, the intensity of an external heat source, chemical reactions, and many others, were also evaluated. The presence of nanoparticles enhances temperature conduction. Also, the findings are compared with previously published research. In addition, the Nusselt number and skin friction increase as the variables associated with the Hartman number and buoyancy parameter grow. The respective transfer rates of heat are 28.26%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\%$$\\end{document} and 38.19%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\%$$\\end{document} respectively. As a result, the rate of heat transmission increased by 14.23%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\%$$\\end{document}. The velocity profiles enhanced while temperature profiles declined for higher values of the Maxwell fluid parameter. As the external heat source increases, the temperature profile rises. Conversely, buoyancy parameters increase as it descends. This type of problem is applicable in many fields such as heat exchangers, cooling of electronic devices, and automotive cooling systems.

Numerical simulation study on the effect of internal heat source on pumping ventilation

Natural ventilation is a passive building technology that can reduce energy consumption for mechanical cooling of the indoor environment. Natural ventilation technology has received renewed attention from researchers. Theoretical studies on natural ventilation have evolved from a steady state to a non-steady state. Pumping ventilation is distinct from other ways of natural ventilation in that its flow direction alternatingly changes from the indoor to the outdoor. However, all published studies did not consider the influence of internal heat sources in pumping ventilation, and there are few discussions about the fluid periodic variation in wind-thermal coupling studies. Based on a previous study, the numerical simulation of single-sided pumping ventilation with two openings in the same wall driven by wind and thermal pressure is conducted in the paper. The influence of heat source intensity and the height of the location of the heat source are analyzed. The applicability of different ventilation rate calculation formulas is discussed. The results show that the indoor airflow oscillation frequency decreases in the effect of wind and thermal pressure, compared to driven by air pressure alone. However, changing the height location and intensity of the heat source does not affect the frequency characteristics in these cases.

An Accurate Electro-Thermal Coupling Model of a GaAs HBT Device under Floating Heat Source Disturbances.

Taking into consideration the inaccurate temperature predictions in traditional thermal models of power devices, we undertook a study on the temperature rise characteristics of heterojunction bipolar transistors (HBTs) with a two-dimensional cross-sectional structure including a sub-collector region. We developed a current-adjusted polynomial electro-thermal coupling model based on investigating floating heat sources. This model was developed using precise simulation data acquired from SILVACO (Santa Clara, CA, USA). Additionally, we utilized COMSOL software (version 5.6) to simulate the temperature distribution within parallel power cells, examining further impacts resulting from thermal coupling. The research findings indicate that the rise in current induces modifications in the local carrier concentration, thereby prompting variations in the local electric field, including changes in the heat source's peak location and intensity. The device's peak temperature exhibits a non-linear trend regulated by the current, revealing an error margin of less than 1.5% in the proposed current-corrected model. At higher current levels, the drift of the heat source leads to an increase in the heat dissipation path and reduces the coupling strength between parallel devices. Experiments were performed on 64 GaAs (gallium arsenide) HBT-based power cells using a QFI infrared imaging system. Compared to the traditional temperature calculation model, the proposed model increased the accuracy by 6.84%, allowing for more precise predictions of transistor peak temperatures in high-power applications.

Intensity analysis of frictional heat source during core tube sampling and drilling

AbstractCurrently, the heat generated during coal core tube sampling causes rapid gas desorption, leading to substantial measurement errors in laboratory gas content assessments. Reducing these errors requires studying frictional heat from core tube friction against the hole wall and coal core temperature rise. Combining the independently developed device to simulate the thermal effect of coring and the COMSOL finite element analysis software, the intensity of the frictional heat source during the core tube sampling and drilling process was analyzed under different coring depth and rotational speed conditions. The research results show that: At constant speed, frictional heat intensifies as the core depth increases. However, the rate of temperature rise decreases with increasing core depth; when the coring depth is constant, the frictional heat is proportional to the rotational speed. For example, at a depth of 140 m and a rotational speed of 120 r/min, the intensity of frictional heat generated by drilling is 2.21 ∗ 10E6J. Similarly, at 180 r/min, the strength is 2.28 ∗ 10E6J, and at 240 r/min, the strength reaches 3.65 ∗ 10E6J; Under certain conditions, core tube wall temperature will not rise indefinitely but will stabilize to a certain value.

Mesoscale multi-component energy density transport for natural convective microchip cooling with solid–liquid–gas phase changes

A design of microchip cooling with natural convection driven multi-phase coolant flows is proposed by using thermoelectric modules as heat sinks. A new multi-component multi-phase (MCMP) thermal energy transport model is built for convective heat transfer with solid–liquid–gas phase changes. Different from previous lattice Boltzmann models based on temperature distributions, the present model is based on MCMP energy density distributions, which track sensible and latent heat transport for each phase. The local MCMP heat fluxes are related to mesoscale relaxation times and phase volume fractions. Transient solid–liquid–gas interfaces and local temperatures are obtained through the dynamical balance of mesoscale forces and fluxes among all phases together with MCMP enthalpy–temperature distributions. Comparisons of the on and off states of the heat sink modules show that the chip temperature can drop from about 300 to 110 °C, with the coolant liquid–gas phase change temperature of 80 °C at equivalent heat source and sink intensities of 100 W/cm2. Results also show that increasing heat sink intensity to 300 W/cm2 or decreasing gas–liquid phase change temperature to 60 °C can further decrease the chip temperature to 90 °C. The effects of sizes of chips, modules, and cooling units are also illustrated. It is observed that gas bubbles attached on chips impede heat transfer due to the low gas phase thermal conductivity, which means future improvements should also focus on removing or degrading attached gas bubbles. This model provides a quantitative tool for immersion chip cooling performances.

Modeling and solving of temperature field of screw–nut pair based on geometric error distribution probability

Random geometric errors are inevitable during the machining process of the screw raceway, ball and nut raceway, which makes the contact state between the ball and raceway diverse, further leading to the generation of nonequal strength heat sources inside the screw–nut pair. In the past, when studying the temperature field of the screw–nut pair, it was assumed that all the balls were evenly loaded. To achieve more accurate temperature field modeling, the modeling of temperature field of the screw–nut pair based on geometric error distribution probability was studied. First, a quantitative relationship between geometric error and contact angle are established. Second, the axial force generated by ball and raceway with different joint geometric errors is determined when subjected to axial loads. Then, on the basis of geometric error statistics, the relationship between the error probability distribution and the heat source intensity distribution is connected, and the corresponding temperature field is solved by the finite difference method. Finally, the probabilistic temperature distribution theory is verified indirectly by a multi-axis thermal deformation experiment. The probabilistic temperature distribution model shows the dynamic change process of the temperature field with the probability of geometric error distribution and has guiding significance for the temperature field modeling of the screw–nut pairs with different precision. When the joint error presents a rectangular distribution, the maximum intensity heat source will be generated, and the ultimate temperature field will be induced.

Personalized kitchen air supply for reducing individual thermal discomfort and cooking pollution intake

High ambient temperature and cooking activities that produce pollutants and waste heat usually make the indoor air quality and thermal environment of residential kitchen unfavorable in summer. Personalized kitchen air supply (PKAS) could be applied to relieve the thermal discomfort and cooking pollution intake of cooking staff. This paper investigated a personalized air supply method of residential kitchen in summer. The residential kitchen was depicted in computational fluid dynamics simulation by realizable k-ε model and discrete ordinate radiation model to reflect the complex thermal characteristics of stove. Based on orthogonal analysis, exhaust rate, exhaust outlet baffle width, and supply air angle were significant factors affecting the concentration of pollutant in kitchen space, whereas exhaust rate and air supply rate were significant factors affecting the intake fraction. Single-factor analysis was further conducted to find better parameter configurations of PKAS for pollutant control. Then, thermal comfort experiments with and without air supply were carried out. When the air supply volume was 280 m³/h and the air supply temperature was 21 °C, the thermal discomfort of subjects can be effectively improved against an uncomfortable condition of 30 °C background temperature, 80 % relative humidity, and a localized heat source intensity of 4.5 kW. The result of this paper can provide valuable information to develop PKAS for better thermal discomfort improvement and cooking pollutants control.

Conjugate dissipative radiative heating with thermal slipping and the entropy production on the thrust of MHD gold blood nanofluid with curvature effects

AbstractThis article analyzes the impact of conjugated dissipative radiative heat transfer with heat source/sink, thermal slip, and the transverse magnetic field on the behavior of the magnetohydrodynamic (MHD) peristaltic thrust containing ferromagnetic gold nanoparticles (AuNPs) with different shape factors through the non‐Newtionian blood flow within compliant walls tube. Entropy generation (EG) plays a prominent role in all aspects connected to thermodynamics and heat transfer aiding in the identification and reduction of system irreversibilities. The sources of irreversibility stem from dissipative friction inherent in fluid flow, the presence of a magnetic field, and the heat transfer process. The ferromagnetic gold nanoparticles (AuNPs) exhibit diverse shapes (bricks, cylinders, and platelets) and possess both magnetic and thermal attributes thereby enhancing the efficiency of heat transfer process. The peristaltic thrust drives the dynamic behavior of the gold blood nanofluid through a compliant tube. The tube walls are flexible and exhibit a curvature effects that can alter the dynamics of fluid flow. The effective Hamilton‐Crosser model is selected to express the thermal conductivity of the nanofluid. Gold blood nanofluids can be treated as incompressible, non‐Newtonian, and MHD fluid flow. The governing equations of the system are solved using the perturbation approach under the assumptions of low Reynolds numbers and long wavelength. Hybrid interactions of magnetic field, radiative heating, thermal slip, elastic wall properties, and gold nanoparticles shapes and concentrations are investigated within the gold blood nanofluid flow. The resulting graphs include the profiles of velocity, temperature distributions, EG, and irreversibility parameters under the influence of the above parameters. The findings reveal that the overall EG rises with increasing values of heat source intensity, Brinkman number, temperature difference factor, compliant wall curvature coefficient, and gold nanoparticles concentrations. Additionally, it is observed that an increase in magnetic flux strength results in the emergence of reversal flow patterns near the walls. This arises due to the augmented magnetic flux obstructing the peristaltic nanofluid flow leading to reduce streamwise velocity. Moreover, heightened magnetic flux strength causes temperature reduction for both thermal slip and non‐slip conditions. Generally, the presence of a thermal slipping parameter further enhances the distribution of temperature. In essence, the rationale and significance of this study primarily revolve around comprehending the interplay of these diverse factors with MHD peristaltic motion of gold blood nanofluid and EG. This not only furthers our theoretical understanding of complex systems but also has practical implications that can improve new technologies, processes, and medical applications. For example, in medical treatments like photothermal therapy (PPT), insights gained from this research can help in developing more effective and precise treatment methods. By understanding the impact of these factors on EG, new ways can be identified to minimize or manage system inefficiencies leading to more sustainable and optimized treatment processes. This research holds promise for application in cancer detection and treatment by employing a combination of PPT and magnetic hyperthermia. This entails dispersing AuNPs into the blood circulation through arteries and blood vessels and subsequently applying photothermal radiation and a magnetic field.

Comparative studies and optimizations of air distribution of underground building ventilation systems based on response surface methodology: A case study

As underground enclosed buildings, utility tunnels have limited ventilation conditions. An efficient ventilation system is necessary for improving the indoor thermal environment and air quality in utility tunnels. In this paper, exhaust fan ventilation (EFV), relay fan ventilation (RFV), and innovative wall-attached ventilation (WAV) schemes are compared using a series of evaluation indicators (i.e., energy efficiency coefficient, nonuniform coefficient, temperature not guaranteed rate, and age of air). The results show that the WAV scheme offers a higher ventilation efficiency, while decreasing the age of air and providing a uniform air distribution. Thus, the WAV scheme is recommended for utility tunnel ventilation systems. Additionally, the WAV scheme is further optimized and analysed based on response surface methodology (RSM). The influence of different factors (i.e., the slot outlet height (h), slot outlet width (b), air-supply velocity (u0), and cable heat source intensity (q)) on the evaluation indicators is studied, and the optimal design scheme (h = 1.40 m, b = 0.12 m, u0 = 3.00 m/s, q = 74.5 W/m2) is obtained and verified. The age of air in the optimal design scheme is 486.50 s. This paper can provide a reference for the ventilation design of urban underground buildings.

Performance and reliability of Al2O3/TiC ceramic tool with multi-bionic surface microstructure in intermittent dry turning of AISI 52100 hardened steel

The biological structures of Odontodactylus scyllarus, Gampsocleis grafiosa and Procambarus clarkia have interesting functions. They provide valuable inspiration for creating multi-bionic surface microstructure on Al2O3/TiC cutting tool. The microstructure is expected to effectively improve performance and reliability. This work analyzed performance and reliability of Al2O3/TiC cutting tool with multi-bionic microstructure in intermittent dry turning of AISI 52100 hardened steel. It was found that the dimension and the shape of the multi-bionic surface microstructure were greatly affected by the heat source intensity of the laser pulse. The cumulative damage Dcm of tool was negatively correlated with the fractal dimension Fmca obtained for laser-caused microscopic crack. The correlation coefficient was found to be −0.8635. On the contrary, the fracture toughness KICM was positively correlated with Fmca. The correlation coefficient had a value of 0.8731. A theoretical performance metric Pm was put forward for the tool by fusing tool stress, material damage and fracture toughness. The theoretical performance metric Pm was verified by the experimental tool life. Both tool performance and tool reliability were enhanced by using the proposed surface microstructure. Moreover, the optimum tool performance and the highest tool reliability arose simultaneously when the laser angle was 75°. Tool performance and tool reliability can be separately enhanced by 57% and 63% at this laser angle.

A general differentiable layout optimization framework for heat transfer problems

In the present work, we intend to demonstrate how to efficiently perform heat source layout design in a gradient-based way to maximally enhance the performance of heat transfer systems. To this end, a general and differentiable heat source layout optimization framework based on parameterized level set functions is proposed to optimize a thermal objective. Heaviside projection is utilized to realize an analytical description of the heat source intensity function, thus engaging a differentiable finite element analysis (FEA) implementation. The automatic differentiation technique is incorporated into this framework for sensitivity analysis, which can avoid tedious manual derivation work. Furthermore, gradient oscillations caused by improper finite element discretization are observed within components moving boundaries, thus possibly resulting in optimization failures. To remedy this problem, an adaptive multiresolution FEA method is proposed to enhance the awareness of component boundaries and eliminate this instability without introducing an extra FEA cost. Several numerical experiments are presented to illustrate positive effects of the adaptive multiresolution strategy and demonstrate the effectiveness of the proposed general and differentiable approach in heat conduction problems. To the best of our knowledge, it is the first time to realize such a framework for heat transfer systems with arbitrary-shaped heat sources. It is very promising to extend this framework to other physical field problems, or combine this framework with a deep learning-based surrogate in a unified way and implement a more efficient low-cost layout design in future research.

Impact of Arrhenius activation energy on MHD nanofluid flow past a stretching sheet with exponential heat source: A modified Buongiorno’s model approach

Nanofluids have a wide range of applications in biological research. They are employed in targeted medication administration, hyperthermia (for cancer treatment) and differential diagnostics like magnetic resonance image (MRI). In light of these medical applications, the impact of an external magnetic field and an exponential heat source on the dynamics of [Formula: see text]–[Formula: see text] over a nonlinearly stretched surface has been investigated. A realistic modified Buongiorno model has been used which includes the effects of reaction rate, Biot number and activation energy. The boundary value problem governing the model is solved on MATLAB R2022a using the solver, BVP5C. Further, the consequences of different parameters on rate of heat transfer coefficient (Nusselt number), rate of mass transfer coefficient (Sherwood number), drag coefficient, velocity, temperature and volume fraction profile are observed graphically. It is noted that volume fraction and uniform heat source intensity have a positive effect on the Nusselt number and negative effect on Sherwood number. The effects of thermal radiation and magnetic field on volume fraction profile are, respectively, positive and negative. The current physics of flow across a vertical stretching surface is expected to serve as the foundation for various medical science, engineering and technology applications.