Metal Heat Research Articles

Operating condition optimization of liquid metal heat pipe using deep learning based genetic algorithm: Heat transfer performance

Liquid metal heat pipes play a critical role in various high-temperature applications, with their optimization being pivotal to achieving optimal thermal performance. In this study, a deep learning based genetic algorithm is suggested to optimize the operating conditions of liquid metal heat pipes. The optimization performance was investigated in both single and multi-variable optimization schemes, considering the operating conditions of heat load, inclination angle, and filling ratio. The single-variable optimization indicated reasonable performance for various conditions, reinforcing the potential applicability of the optimization method across a broad spectrum of high-temperature industries. The multi-variable optimization revealed an almost congruent performance level to single-variable optimization, suggesting that the robustness of optimization method is not compromised with additional variables. Furthermore, the generalization performance of the optimization method was investigated by conducting an experimental investigation, proving a similar performance. This study underlines the potential of optimizing the operating condition of heat pipes, with significant consequences in sectors such as high temperature field, thereby offering a pathway to more efficient, cost-effective thermal solutions.

Ceramic-to-metal bonding using rare-earth containing Sn–Bi solder

With the increasing miniaturization and power of optoelectronic devices, direct bonding of optical substrates like semiconductors and ceramics to metal heat sinks using low melting-point solder has gained significant interest. In this study, we demonstrated the bonding of glass to copper using Sn-58 wt% Bi solder (SB solder) doped with a small amount of rare earth (RE) elements. The RE elements act as active agents that facilitate the bonding to glasses without glass metallization. By optimizing the bonding parameters, such as reflow temperature and time, and employing an inert gas atmosphere to prevent solder or RE oxidation, we successfully achieved the highest shear strength in glass-copper solder joints using SB-RE solder, without the need for ultrasonic-assisted soldering (UAS). These results demonstrate the potential of using RE-containing solder for bonding unmetallized glass and ceramics in optoelectronic devices with metals at low soldering temperatures (< 200 °C). Furthermore, analysis of the shear strength and failure morphology of solder joints revealed only small degradation, primarily originating from the bulk solder region rather than the solder-glass interface, after both thermal aging (100 h) and cycling tests (100 cycles). The establishment of low-melting point RE-containing solders opens the possibility of direct jointing ceramic optoelectronic substrates to metal heat sinks for more efficient heat dissipation. In the meantime, our work also suggests that further optimization studies are necessary to explore its performance under more extreme working conditions.

Numerical study of turbulent heat transfer of annular fuel assembly in a sodium-cooled fast reactor by a SST k-ω-kθ-εθ model

ABSTRACT The annular fuel has two cooling surfaces inside and outside, which can fully take away the heat of the fuel assemblies. It is urgent to conduct research on sodium-cooled fast reactor annular fuel assemblies. The Prandtl number Pr of liquid sodium is much less than 1 (Pr ˂˂ 1). The problem is that using the traditional constant turbulent Prandtl number Pr t of 0.85 ~ 0.9, which will greatly affect the accuracy of the numerical prediction of the thermal-hydraulic properties of liquid sodium. In order to address this issue, the turbulent heat transfer characteristics of the bare and wire spacers 7-pin annular fuel assembly for a sodium-cooled fast reactor are investigated by a SST k-ω-k θ -ε θ model. The open-source CFD software OpenFOAM is used for this calculation. In order to verify the validity of the present calculation method, some classical liquid metal heat transfer correlations are used to compare and analyze the results of the present calculation method (k θ -ε θ model), the results of the Reynolds analogy hypothesis (Pr t = 0.85 model), and the results of the turbulent Prandtl number correlation (Pr t = kays model). It is shown that the SST k-ω-Pr t = 0.85 model overestimates the Nusselt number Nu of the annular fuel assembly. The SST k-ω-k θ -ε θ model agrees well with the SST k-ω-Pr t = Kays model of the bare and wire spacers 7-pin annular fuel assembly . It suggests that the numerical calculation results of the SST k-ω-k θ -ε θ model are reliable in both the simple and complex fuel assembly models. In brief, the SST k-ω-k θ -ε θ model is more capable of predicting the turbulent heat transfer characteristics of the bare and wire spacers 7-pin annular fuel assembly in sodium-cooled fast reactors. In addition, the thermal-hydraulic characteristics of annular fuel assemblies with wire spacers for sodium-cooled fast reactors have been investigated. This research can provide a reference for the study of turbulent heat transfer characteristics of annular fuel assemblies in sodium-cooled fast reactor.

Scalable Photonic Digital-to-Analog Converters

This work introduces a novel architecture for implementing a parallel coherent photonic digital-to-analog converter (PDAC), designed to transform parallel digital electrical signals into corresponding analog optical output, convertible to analog electrical signals using photodiodes. The proposed architecture incorporates microring resonator-based modulators (MRMs), phase shifters, and symmetric multimode interference couplers. Efficient modulation is achieved by MRMs utilizing carrier depletion-induced refractive index changes, while metal heaters facilitate tuning of the ring resonator resonance wavelength. The proposed architecture is scalable to higher bit resolutions and exhibits a dynamic range limited by MRM’s sensitivity to applied bias and noise levels. Experimental results of the fabricated chip in the silicon-on-insulator (SOI) platform showcase the successful realization of a 4 GSample/sec conversion rate in a 2-bit resolution operation, along with a stationary conversion of four parallel DC digital signals into 16 analog intensity levels in a 4-bit PDAC configuration. The study encompasses a proof-of-concept experimental demonstration of 8 Gbps data conversion, along with a 50 Gbps data conversion rate using the optimized design in the simulation, affirming the accuracy and quality of the PDAC architecture. These findings contribute to the advancement of PDAC technology, providing insights into performance characteristics, limitations, and potential applications.

Numerical Simulation of Heat Pipe Thermal Performance for Aerospace Cooling System Applications

The design of integrated and highly efficient solutions for thermal management is a key capability for different aerospace products, ranging from civil aircraft using hydrogen on board to miniaturized satellites. In particular, this paper discloses a novel numerical tool for the design and thermal performance assessment of heat pipes. To achieve this goal, a numerical Ansys Parametric Design Language code is set up to verify the effective subtractive heat flux guaranteed by the selected heat pipe arrangement. The methodology and related tool show their ability to provide good thermal performance estimates for different heat pipe designs and operating conditions. Specifically, the paper reports two very different test cases: (1) solid metal heat pipes to cool down the crotch leading-edge area of the air intake of a Mach 8 civil passenger aircraft, and (2) a copper-water heat pipe to cool down a Printed Circuit Board of a generic small LEO satellite. The successful application of the methodology and numerical code confirms the achievement of the ambitious goal of developing in-house tools to support heat pipe thermal performance prediction for the entire aerospace domain.

Investigating diffusion and convergence trajectory of hydrogen storage technology based on patent analysis

Safe and flexible hydrogen storage technology (HST) emerges as a crucial element in driving the industrialization of hydrogen energy. Consequently, HSTs are being extensively investigated globally, with an increasing number diffusing beyond national boundaries through transnational patent applications. However, the absence of an evolutionary analysis constrains the exploration of technological opportunities in HST. In this study, we unveil the evolutionary trajectory and innovation trends of HST by analyzing its global diffusion and convergence network, utilizing patent family and IPC co-occurrence data spanning from 1993 to 2022. Our results indicate that the transnational diffusion of HST is concentrated in core countries. Japan and France emerged as dominant source countries, while China, Europe, Korea, and Canada were identified as main target countries for HST diffusion. Notably, in the past decade, China and France have experienced significant expansion in filing HST patents. However, China filed a relatively limited number of patent families, suggesting a varied level of engagement in transnational HST diffusion. Hydrogen fuel cells, storage alloys, vessels, and distribution systems constitute the primary technological domains of HST. In the initial stages, fuel cells and alloy materials dominated HST development, often converging with metal powders and heat treatment. However, since 2003, F17C, related to storage vessels, has evolved as a focal point of convergence, involving the integration of pressure tanks, filling and discharging systems, liquid transportation, gas purification, and rare earth materials. Overall, this research offers novel insights for strategizing future HST innovations.

Study of heating and evaporation of metal in an inductor in relation to the problem of space debris processing and creating evaporative-type space engine

The work experimentally studied the evaporation of water and metal in a crucible simulating the nozzle of a space engine during induction heating, and also carried out analytical assessments of the generated jet thrust. An experimental laboratory setup is described. Measurements of the pressure created by the nozzle as a result of evaporation of the material in a vacuum were carried out. Zinc was used as the evaporated material. The experimental results are in satisfactory agreement with theoretical estimates. The results obtained are expected to be used in the development of an evaporative-type space engine with space debris as a working fluid.

Iron particles ignition in different hot coflow temperatures

Understanding the ignition of iron particle combustion in hot environments is critical for harnessing the use of metal fuels in clean energy production. In this research work, a new single particle burner is implemented to disperse and burn iron particles using hot air coflow. The burner disperses iron particles through Coulomb forces between two air-spaced capacitor electrodes. The oxidizer coflow is heated up as it passes through a newly designed induction gas heater. Electromagnetic induction is used to heat up multiple metallic and porous heat discs by Joule heating. When the coflow gas passes through the pores of the discs, it carries the heat generated within the porous discs and delivers it to the travelling iron particles which provides ultimate heat transfer effectiveness. Coflow temperature homogeneity is examined using Schlieren imaging and confirmed by thermocouple measurements at the outlet of the coflow tube. Particle ignition and combustion occur in open space, providing excellent conditions for optical diagnostics. Two synchronized high-speed cameras were used to simultaneously determine the particle size using green laser shadowgraphy and detect iron particles ignition. Iron particles ignition experiments were conducted for a sieved patch (45–53 μm) at different hot coflow temperatures starting at 700℃ up to 900℃. The burner showed extensive capabilities to maintains a stable and homogeneous hot coflow for a wide range of temperatures up to 900℃. Ignition experiments showed 5.67 % of ejected particles are burnt at 700 ℃, while full ignition (99.33 %) can be achieved at 900 ℃.

Low-loss integrated dynamic polarization controller based on silicon photonics

&lt;sec&gt;A dynamic polarization controller (DPC) is an important component in fiber optic communication, optical imaging, and quantum technologies. The DPC can transform any input state of polarization (SOP) into any desired SOP to overcome polarization-related impairments resulting from high internally and externally induced birefringence. In this work, a low-loss silicon photonics-integrated DPC is designed and demonstrated experimentally. The whole chip is fabricated by using industry-standard silicon-on-insulator technology. Using the edge-coupling method, the coupler loss is reduced to less than 2 dB, and the total loss of DPC is reduced to 5.7 dB. Using a variable-step simulated annealing method, for a low-noise photodetector and high-static-extinction-ratio device, a dynamic polarization extinction ratio can reach more than 30 dB. The size of the DPC on the chip is 5.20 mm × 0.12 mm × 0.80 mm.&lt;/sec&gt;&lt;sec&gt;The DPC utilizes a 0°/45°/0°/45° structure, which can realize arbitrary polarization-based coordinate conversion with endless polarization control. The 0° and 45° transform structures and matrices are presented, and the principle of the 0° and 45° structures is explained in detail by using the Poincaré sphere.&lt;/sec&gt;&lt;sec&gt;A simulation using Lumerical is conducted to optimize the polarization rotator-splitter, which can transform the TM&lt;sub&gt;0&lt;/sub&gt; mode light in one waveguide into the TE&lt;sub&gt;0&lt;/sub&gt; mode light in the other waveguide while the TE&lt;sub&gt;0&lt;/sub&gt; mode light in one waveguide remains unchanged. Based on the optimized structure, the static polarization extinction ratio of DPC can be measured to be a value greater than 40 dB.&lt;/sec&gt;&lt;sec&gt;The thermal phase shift (TPS) is characterized by using a Mach–Zehnder modulator. The length of the TPS is 400 μm, and the resistance of the metal heater is 2.00 kΩ. The maximum power consumed by the four TPSs is a total of 0.2 W. The modulation bandwidth of the DPC designed by our group is approximately 30 kHz. By considering an applied voltage of 5.6 V in the case of the TPS, the bandwidth–voltage product is 5.6 × 30 = 168 kHz·V.&lt;/sec&gt;&lt;sec&gt;To optimize the DPC parameters, such as the step length, electronic noise, and static polarization extinction ratio, numerical simulation results of the simulated annealing approach are analyzed in detail.&lt;/sec&gt;&lt;sec&gt;In conclusion, a low-loss silicon photonics-integrated DPC is designed and demonstrated experimentally. A dynamic polarization extinction ratio is obtained to be greater than 30 dB by using the variable-step simulated annealing method. The DPC is expected to be utilized in fiber or quantum communication systems to minimize size and further decrease costs.&lt;/sec&gt;

Low-loss integrated dynamic polarization controller based on silicon photonics

&lt;sec&gt;A dynamic polarization controller (DPC) is an important component in fiber optic communication, optical imaging, and quantum technologies. The DPC can transform any input state of polarization (SOP) into any desired SOP to overcome polarization-related impairments resulting from high internally and externally induced birefringence. In this work, a low-loss silicon photonics-integrated DPC is designed and demonstrated experimentally. The whole chip is fabricated by using industry-standard silicon-on-insulator technology. Using the butting coupling method, the coupler loss is reduced to less than 2 dB, and the total loss of DPC is reduced to 5.7 dB. Using a variable-step simulated annealing method, for a low-noise photodetector and high-static-extinction-ratio device, a dynamic polarization extinction ratio can reach more than 30 dB. The size of the DPC on the chip is 5.20 mm × 0.12 mm × 0.80 mm.&lt;/sec&gt;&lt;sec&gt;The DPC utilizes a 0°/45°/0°/45° structure, which can realize arbitrary polarization-based coordinate conversion with endless polarization control. The 0° and 45° transform structures and matrices are presented, and the principle of the 0° and 45° structures is explained in detail by using the Poincaré sphere.&lt;/sec&gt;&lt;sec&gt;A simulation using Lumerical is conducted to optimize the polarization rotator-splitter, which can transform the TM&lt;sub&gt;0&lt;/sub&gt; mode light in one waveguide into the TE&lt;sub&gt;0&lt;/sub&gt; mode light in the other waveguide while the TE&lt;sub&gt;0&lt;/sub&gt; mode light in one waveguide remains unchanged. Based on the optimized structure, the static polarization extinction ratio of DPC can be measured to be a value greater than 40 dB.&lt;/sec&gt;&lt;sec&gt;The thermal phase shift (TPS) is characterized by using a Mach–Zehnder modulator. The length of the TPS is 400 μm, and the resistance of the metal heater is 2.00 kΩ. The maximum power consumed by the four TPSs is a total of 0.2 W. The modulation bandwidth of the DPC designed by our group is approximately 30 kHz. By considering an applied voltage of 5.6 V in the case of the TPS, the bandwidth–voltage product is 5.6 × 30 = 168 kHz·V.&lt;/sec&gt;&lt;sec&gt;To optimize the DPC parameters, such as the step length, electronic noise, and static polarization extinction ratio, numerical simulation results of the simulated annealing approach are analyzed in detail.&lt;/sec&gt;&lt;sec&gt;In conclusion, a low-loss silicon photonics-integrated DPC is designed and demonstrated experimentally. A dynamic polarization extinction ratio is obtained to be greater than 30 dB by using the variable-step simulated annealing method. The DPC is expected to be utilized in fiber or quantum communication systems to minimize size and further decrease costs.&lt;/sec&gt;

Thermal Analysis of Al and Cu Metals Heat Sinks with Different Geometries at Raspberry Pi Control Cards Used for Image Analysis-Based Drone Control in Smart Agriculture Drones

A heat sink is a tool for dissipating the heat generated by electronic parts. The equipment's specific operating conditions necessitate the equipment's extra heat dissipation. This research compared and optimized the temperature and heat flux parameters based on the results of the design of a heat sink for CPU, RAM, and PCLe to a USB 3.0 bridge. It is aimed at an examination of the advantages and disadvantages of using square, rectangular, and circular shapes in the design of a heat sink. Copper and aluminum (Al) are the most common heat sink materials (Cu). Autodesk Inventor Pro software with Nastran module is used for design and thermal analysis.&#x0D; According to Inventor Nastran's thermal analysis results it is found that there is no significant difference between Al and Cu materials based on cooling capacity at designed models. Also, it is found that the geometry of the heat sinks directly affects the cooling capacity of a heat sink.&#x0D; The application results show that the cooling achievement is directly related to the correct heatsink design and enough surface area.&#x0D; According to Inventor Nastran's thermal analysis results it is found that there is no important difference between Al and Cu materials based on cooling capacity at designed models. Also, it is found that the geometry of the heat sinks directly affects the cooling capacity of a heat sink.&#x0D; The application results show that the cooling achievement is directly related to the correct heatsink design and enough surface area.

Fatigue fracture mechanisms and life prediction of welded S310 - S321 joints at high temperature

Austenitic stainless steel is prevalent in the manufacturing of aircraft structural components and chemical pipelines, which are frequently subjected to high temperatures. To investigate the high cycle fatigue strength of welds involving two stainless steel materials S310 and S321, a series of high cycle fatigue tests were conducted at 550 °C, 650 °C, 750 °C, and 850 °C, respectively. Scanning electron microscopy (SEM) was used to observe the fracture surfaces in the base metal zone (BM), fusion zone (FZ), and heat affected zone (HAZ). The microstructure characteristics near the fusion line of the specimens were analyzed by the electron backscatter diffraction (EBSD). Results reveal a negative relavance between the presence of inclined coherent twin boundaries (CTBs) and material's fatigue performance. The initiation of cracks from the surface is caused by machining defects, welding voids, and high temperature oxidation of certain grains near the surface. For specimens that fracture in the FZ, the fatigue life show the divergence trend with temperature increases. Meanwhile, a fatigue life prediction model based on XGboost algorithm is developed with axial stress amplitude (σa), temperature (T), average grain size (Dmean), twin boundary density in the FZ (ρtb), and fracture location (Lf) as crucial analytical parameters. This model demonstrates better accuracy in predicting fatigue life with a mean absolute percentage error (MAPE) of 39.58 % compared with Basqin model's 46.81 %.

Optimization and comprehensive comparison of thermo-optic phase shifter with folded waveguide on SiN and SOI platforms

The thermo-optic phase shifter (TOPS) using metal heaters is widely used in various integrated photonics devices for its advantages of simple fabrication, low loss, and low cost. While folded waveguides are commonly employed to enhance the performance of these phase shifters, a comprehensive understanding of how varying the number of folds and the dimensions of heaters impact the device's performance is still lacking. In this paper, we conducted a comprehensive comparison and optimization into the impact of the number of folded waveguides and the width of heater on the performance of folded waveguide thermo-optic phase shifter (FW-TOPS) on silicon nitride (SiN) and silicon-on-insulator (SOI) platforms using the finite element method (FEM). The research has revealed that both the number of waveguides and the width of the heater exert a substantial influence on the performance of FW-TOPS, particularly on platforms with low refractive index contrast. In cases where the number of waveguides is the same, and the width of the heater electrode is identical, the comparison indicates that on the SiN platform, the FW-TOPS in waveguide Combination 2 (waveguide 1 is a single-mode waveguide, while waveguide 2 is a multi-mode waveguide) exhibits superior overall performance, compared to waveguide Combination 1 (both waveguide 1 and waveguide 2 are single-mode waveguides). However, on the SOI platform, FW-TOPS with waveguide Combination 1 demonstrates better overall performance compared to waveguide Combination 2. Furthermore, the simulation results indicate that although air trenches can significantly reduce the power consumption of the FW-TOPS, they also lead to a substantial decrease in the response speed. Therefore, on the 300 nm-thick SiN and 220 nm-thick SOI platforms, air trenches do not effectively enhance the overall performance of the FW-TOPS.

Operational Characteristics of Research and Test Benches and Installations with Heavy Liquid Metal Heat Carriers

Operational Characteristics of Research and Test Benches and Installations with Heavy Liquid Metal Heat Carriers

Conjugate Modeling of a Closed Co-Rotating Compressor Cavity

Abstract Robust methods to predict heat transfer are vital to accurately control the blade-tip clearance in compressors and the radial growth of the disks to which these blades are attached. Fundamentally, the flow in the cavity between the co-rotating disks is a conjugate problem: the temperature gradient across this cavity drives large-scale buoyant structures in the core that rotate asynchronously to the disks, which in turn governs the heat transfer and temperature distributions in the disks. The practical engine designer requires expedient computational methods and low-order modeling. A conjugate heat transfer (CHT) methodology that can be used as a predictive tool is introduced here. Most simulations for rotating cavities only consider the fluid domain in isolation and typically require known disk temperature distributions as the boundary condition for the solution. This paper presents a novel coupling strategy for the conjugate problem, where unsteady Reynolds averaged Navier–Stokes (URANS) simulations for the fluid are combined with a series of steady simulations for the solid domain in an iterative approach. This strategy overcomes the limitations due to the difference in thermal inertia between fluid and solid; the method retains the unsteady flow features but allows a prediction of the disk temperature distributions, rather than using them as a boundary condition. This approach has been validated on the fundamental flow configuration of a closed co-rotating cavity. Metal temperatures and heat transfer correlations predicted by the simulation are compared to those measured experimentally for a range of engine-relevant conditions.

Analytical solution and its application for the dynamic characteristics of a heat recovery steam generator in gas–steam combined cycle

This paper presents a study from the perspective of analytical solutions to analyze the dynamic characteristics of a Heat Recovery Steam Generator (HRSG) and explore its practical applications. The study employs the lumped parameter method to simplify the metal heat storage and temperature changes within HRSGs. Differential equations, based on the principles of mass and energy conservation, are formulated to describe the heating surfaces within HRSGs. Analytical solutions are derived, and the essential parameters in these expressions are discussed for their physical significance. Using these analytical solutions, the dynamic heat transfer processes for heating surfaces in a typical HRSG under various starting conditions are investigated. The findings reveal that a larger heat transfer factor or a smaller heat capacity factor of HRSG metal (or a larger ratio of these factors) results in a faster thermal equilibrium during the heat transfer process. Additionally, a dynamic forecasting model is developed based on these analytical solutions. The Particle Swarm Optimization (PSO) algorithm is applied as a parameter identification technique to fine-tune the model's initial parameters, which may be incomplete in real start-up processes. To validate the model, real-time on-site measurement data from a cold start-up of a non-supplementary fired HRSG is used. The results demonstrate the model's strong predictive capabilities, with an average absolute error ranging from 0.5 °C to 2 ℃, highlighting its high accuracy. Comparing the model with a thermal equilibrium model, it is evident that during the cold start-up of an HRSG, the heating surfaces exhibit dynamic characteristics, transitioning from a non-steady state in the first 3000 s to a quasi-steady state between 3000 and 7000 s.

ANTI-CORROSION PROTECTION OF PIPELINES

Currently, in our country, the issue of protecting metals from corrosion has achieved high results, so there is a big gap between the achievements of scientific research in this direction and their use in industry. It is necessary to develop and implement highly effective methods of increasing the strength, corrosion resistance, heat and cold resistance of metals and alloys. Popularization, dissemination and implementation of effective methods of protection against corrosion and corrosive-mechanical destruction of machines, devices, equipment and metal structures are of great importance.&#x0D; During surface-plastic deformation, a chip is not formed, but a fine plastic deformation of the surface layer takes place. As a result, the surface layer is strengthened, wear resistance and resistance to corrosive environment increases. In many cases, the use of surface-plastic deformation makes it possible to increase the safety margin of parts working under variable loads by 1.5 to 3 times, and to increase the service life of parts. The paper examines directions for increasing the stability of parts of oil industry equipment by the method of surface plastic deformation, for resistance against various types of corrosion and corrosive-mechanical destruction.&#x0D; Fatigue is the phenomenon of gradual accumulation of material damage under the action of variable loads, which leads to changes in the properties of crack formation, their development and destruction. The processes of metal fatigue have been studied by many researchers, many hypotheses have been put forward, but the nature of fatigue remains largely unexplained.

Crystal plasticity modeling of electropulsing induced plasticity in metals

A crystal plasticity model incorporating the effects of magnetoplasticity, electron-wind, imbalance of charges near grain boundaries and Joule heating in high frequency short duration electric current pulsed metals has been developed for metals with a face center cubic (FCC) structure. The model decouples the athermal and thermal effects on dislocation activity and quantifies their effects on flow stress. The Joule heating affects the thermal activation in plastic deformation. The magnetoplasticity and electron-wind reduce the slip barrier or contribute additional force to assist dislocation motion. Imbalance of charges near grain boundaries may amplify or minimize the contribution of thermal or other athermal effects. The developed crystal plasticity model has been implemented in DAMASK and verified by simulating electroplasticity in aluminum. The results reveal that the magnetoplasticity reduces flow stress and the reduction increases with the peak current density. Joule heating is generally less important during the processing due to the short pulse duration but becomes more significant when the frequency goes up. The impact of imbalance of charges near grain boundaries on Joule heating depends on the thickness of grain boundaries, the distribution of current density and conductivity, while it always reduces the effect on magnetoplasticity. The electron-wind effect on flow stress is negligible compared to the other three factors. This work provides some new insights in the understanding of electroplasticity in metals.

Experimental and numerical study on temperature control performance of phase change material heat sink

With the increasing power consumption of electronic products, the rising temperature leads to the deterioration of working environment and the reduction of service life. In order to control the temperature rise of electronic products, in this paper, the heat sinks with phase change material (PCM) and honeycomb metal were designed. And their performance was compared with that of the original heat sink (without PCM and honeycomb metal) then studied under various working conditions. Paraffin (n-eicosane) and prepared low melting point alloy were filled into the heat sink with honeycomb metal. The temperature control performance of heat sink was tested experimentally under different heating power. A two-dimensional heat transfer mathematical model of honeycomb metal PCM heat sink was established and solved numerically. The numerical results were compared with experimental data to verify the mathematical model. The results demonstrate that PCM heat sinks effectively controls the temperature of electronic devices and the low melting point alloy makes heat sink better performance than paraffin. Honeycomb metal further decreases the temperature of the paraffin heat sink by up to 3.6 °C, and extends the effective working time of the alloy heat sink by 14 %. The performance of the low melting point honeycomb metal heat sink is superior to that of the paraffin honeycomb metal heat sink at high heating power, and is close to the latter at low heating power. The effective working time of PCM honeycomb metal heat sink is significantly extended when the PCM melting point is close to the limit temperature, especially at high heating power and for the PCM with low thermal conductivity. This study provides valuable reference for temperature control design of electronic products.

Effective Protective Coating of Pipe Metal with High-Strength Corrosion-Resistant Material Based on Low-Molecular Oligodiene

Statement of the problem. A significant number of PJSC «Gazprom» main gas pipelines were built thirty or more years ago. At that time ineffective insulating materials were used for protecting steel pipes, applied mainly in the conditions of the route, which led to their extremely unsatisfactory condition in the future. Thus, at present there is a need to develop effective protective coatings for steel pipelines using domestic materials and equipment. Results. As a result of a series of experiments the composition of the composite material of the insulating coating based on the rubber concrete (Kauton) optimized to the state of the rubber mastic of the usable consistency has been determined. By carrying out a series of search experiments, rational temperature-time regimes of rubber mastic heat treatment have been determined for the formation of an effective layer of protective coating on the surface of pipe metal isolating it from harmful influences. Experimental device for providing modes of structure formation of pipe metal insulating coating material has been designed. Vulcanization of the rubber-containing mastic on the surface of a steel tube is performed by induction heating of the tube metal maintaining the necessary temperature-time modes of structure formation of the protective coating material. The physical and mechanical characteristics of the insulating coating for steel pipes on the basis of rubber mastic have been determined experimentally. Conclusions. The results of the research allow us to draw a conclusion about expediency, efficiency and significance of application in various areas of industrial production of coatings based on synthetic rubber to protect steel pipes from various negative influences and aggressive environments.