Changes In Temperature Field Research Articles

Experimental and numerical study of a passive thermal management system using flat heat pipes for lithium-ion batteries

Effective thermal management is essential for lithium-ion batteries to reduce the battery surface temperatures and the temperature differences within the battery packs. In this study, a battery thermal management (BTM) system containing flat heat pipes was established to improve the temperature uniformity during high discharge rate operations, thereby ensuring battery performances, long lifetimes, and safety. A numerical model was developed, and the modeling results agreed with the experimental data. Through the simulation analysis, we discuss the change in the battery temperature fields, which were compared to two other cooling systems: air natural convection and aluminum plate cooling. The results indicated that the use of flat heat pipes could effectively decrease the maximum temperature and temperature difference with minimum energy costs.

Study on Thermal Erosion Process of SiCp/Al Composite Material in EDM

SiCp/Al composites are composed of two different material properties of aluminium matrix and SiC particles. In order to deeply study the erosion process of SiCp/Al composite in EDM, a single pulse discharge model of SiCp/Al composites was established. The melting and solidification model and the volume of fluid (VOF) model in Fluent software were used to simulate the thermal erosion process of EDM. The change of temperature field and the formation of molten pool in the heating process of SiC particles and Al matrix are analysed. The number of SiC particles in molten pool is counted and analysed, and the number of SiC particles in molten pool was counted, the simulation results were verified by the single pulse EDM experiments. The results show that the depth-diameter ratio of the molten pool increases with the increase of the pulse width, and decreases with the increase of the peak current. The number of melted particles in molten pool is basically unchanged.

Thermal conductive properties of solid-liquid-gas three-phase unsaturated concrete

In order to study the thermal conductivity of unsaturated concrete, 8 groups of concrete samples with different porosity and water content were prepared. For comparative analysis, the porosity of samples by adding air entraining agents with different mass fractions, and the water-filled porosity is controlled by weight and humidity method. The actual porosity, water-filled porosity and gas-filled porosity of the specimens were measured by nuclear magnetic resonance technology (NMR), and the thermal conductivity is synchronously test in the corresponding state. Based on the experimental data, it is verified that the dispersion-continuous thermal conductivity model is feasible to determine the thermal conductivity of unsaturated concrete. Combining the calculated results with the test results, we obtain the variation of thermal conductivity with porosity and gas-liquid filling of pores. Furthermore, a two-dimensional mesoscopic model of porous media was established to analyze the mechanism of the three phases of solid, liquid and gas in the heat transfer process. The results show that both porosity and water content have great influence on the thermal conductivity of concrete. Thermal conductivity not only decreases with the increase of porosity, but also increases nonlinearly with the increase of water-bearing porosity at the same porosity. Compared with the elemental materials, the pore makes the distribution of temperature field change greatly. For three-phase unsaturated concrete, the connectivity of pores and the difference of solid-liquid-gas thermal conductivity will also cause temperature distortion in local areas.

An electromagnetics-temperature-component multi-physical coupled model for electric furnace in calcium carbide smelting process

A transient three-dimensional (3D) mathematical model is established to analyze electromagnetics-temperature-component multi-physical field distribution in calcium carbide (CaC2) smelting process in this paper. The electromagnetic field is solved by Maxwell’s equations using the finite element method. The temperature field and phase change are modeled by the enthalpy equations. The chemical reaction process is built by reaction kinetics equations. The numerical modeling method is verified against data from literature. The results show that multi-physical fields are strongly coupling and uneven in electric furnace. Therefore, the higher temperature and product are mainly distributed in the upper layer of center zone. Large-capacity electric furnace is qualified with significant advantage in increasing output. When three-phase alternating current increases from 10,000 A to 14,000 A, the volume of CaC2 and molten CaC2 pool increases by 51.6% and 52.3% at the end of smelting process, respectively. However, it also increases the temperature in furnace, which has a negative effect on the safe production. The mathematical model established in this paper can accurately reflect electromagnetics-temperature-component multi-physical field distribution, and can provide guidance for the design and development of high-efficiency calcium carbide electric furnace.

Model test and numerical simulation on the development of artificially freezing wall in sandy layers considering water seepage

Abstract The influence of seepage on the development of the frozen wall must be considered when artificial ground freezing (AGF) is applied to the coarse-grained soil layers. In this paper, the influence of groundwater flow in a sandy layer on the temperature field during artificial freezing is studied. Model tests were carried out with different seepage velocity, and the temperature field changes of upstream and downstream as well as the development of the frozen wall were obtained. The experiment was numerically simulated using a finite element platform, COMSOL Multiphysics. The test showed that the frozen wall was symmetrical when there was no seepage, which was approximately elliptical. Under the seepage condition, the upstream and downstream frozen walls were asymmetrical, approximately heart-shaped. The asymmetry increased with the increase of seepage velocity and pipe spacing. When the seepage velocity increased, the closure time of frozen wall increased. The numerical simulation results and the experimental results were basically consistent. The asymmetry of the frozen wall under the seepage condition was quantitatively analyzed based on numerical simulations.

Laser irradiation behavior of plasma-sprayed tantalum oxide coatings

With the repaid development of laser manufacturing industry, laser protection for optical components, especially high power continuous laser, has been a major concern. Optical coatings should have a good anti-laser ablation property. However, the high-power laser ablation behavior of plasma-sprayed Ta2O5 coatings is rarely investigated. In this paper, tantalum oxide coatings were prepared by plasma spraying technique and irradiated using continuous laser with 1070 nm wavelength. The phase structure, ablation surface morphology and reflectivity of the coating were characterized by XRD, SEM, and UV–Visible-near Infrared Spectroscopy. During laser irradiation, the tantalum oxide coatings experience three stages: coating oxidation, micro-cracks occurrence and mechanical failure. A finite-element simulation was also conducted to explore the change of temperature field during irradiation. The simulation results show that the change of reflectivity of tantalum oxide coating during laser irradiation is of great benefit in improving its laser protection ability.

Numerical simulation of bimetallic casting cooling during the process of lost foam casting

The authors consider cooling process of a “gray cast iron–austenitic stainless steel” bimetallic casting in the lost foam casting conditions. They provide a mathematical model of coupled heat transfer between the molten gray cast iron, stainless steel, nonstick coating and dry quartz sand during the process of bimetallic casting cooling, taking into account phase transitions in gray cast iron and quartz sand. The article shares calculated data on casting crystallization time and a solid-phase fraction formed in gray cast iron with temperature field changes with time and cooling rates of the bimetallic casting. The data have been obtained for stainless steel thicknesses of 1.5 mm, 5 mm and 10 mm (volume ratio of 20:1, 6:1 and 3:1, respectively) and two pouring temperatures of 1350 °C and 1500 °C. The calculated values of the bimetallic casting solidification time are summarized as a polynomial. Formation of shrink holes near the left wall of the casting proves to be possible with a stainless steel thickness of 1.5 mm.

Sensitivity Analysis of Laser Quenching Parameters of ASTM 1045 of Disk Laser Based on Response Surface Method

Laser hardening is an important branch of laser surface hardening technology, which is widely used in metallurgy, transportation, machinery manufacturing, aerospace and other fields. At present, relying entirely on experience or process trial-and-error method, it can not effectively reveal the transient mechanism of laser quenching of disk laser, which is not conducive to shortening the research and development cycle and saving costs. The numerical simulation provides an effective way to obtain the dynamic evolution law of multi-field coupling in laser quenching process. In this paper, a thermo-mechanical coupling model of ASTM 1045 laser quenching process by disk laser is established. In the model, the temperature-dependent physical parameters were calculated by CALPHAD method. The transient law of temperature and microstructural transformation during quenching was obtained by solving the model. The formation and transformation degree of martensite were characterized by the dynamic changes of the depth and width of quenched transformation layer. The quenching structure and transformation hardening law were observed by Axioskop 2 SEM and Zeiss-IGMA HD FE-SEM to verify the accuracy of the simulation results. On this basis, the process parameters of laser quenching were sampled by Monte-Carlo method based on response surface methodology. The sensitivity effects of different process parameters on the temperature field and phase change field of laser quenching were analyzed, which laid a theoretical foundation for the optimization of process parameters. (1) Establish a thermo-mechanical coupling model for quenching process of ASTM 1045, and the sensitivity of the system is calculated. (2) The model can accurately reproduce the transient process of temperature and phase transformation field during laser quenching. (3) The laser power and laser incident angle are positively correlated with the response value. (4) The spot diameter and scanning speed are negatively correlated with response value. (5) The model can effectively calculate the sensitivity of laser quenching, predict the width and depth of quenching layer, and optimize process parameters.

Microstructure and Simulation of Semisolid Aluminum Alloy Castings in the Process of Stirring Integrated Transfer-Heat (SIT) with Water Cooling

The continuing quest for aluminum castings with fewer defects has aroused the interest in rheological high-pressure die casting (RHPDC). A new machine, stirring integrated transfer-heat (SIT) device, based on the mechanical stirring and enhanced cooling for semisolid slurry preparation was proposed to produce the thin-walled communication shell part by RHPDC process. The influence of SIT process characteristics on the microstructure was studied. The microstructure of SIT-RHPDC shell part in different locations was investigated. Combined with simulation, the flow characteristics and the temperature field change in the melt under the stirring-only process and different stirring with internal water-cooling conditions were studied to get a better understanding of the nucleation, grain growth and solidification behavior. Under the dual action of agitation and heat dissipation in SIT device, the fluid convection has changed the temperature field of the melt significantly. The temperature field of the melt becomes relatively uniform from a great temperature gradient and the continuous cooling rate is increased to 5 °C/s. In the same time, the slurry has a greater supercooling degree, and flows more evenly in the filling process. The experimental results indicate that compared with microstructure of an HPDC component, the microstructure at different locations of SIT-RHPDC part is composed of refined rosiness and nearly spherical particles.

A Review of Studies on Temperature Field Changes of Solid Rocket Engines under Different Environments

At home and abroad this paper summarizes the present stage of solid missile motor and the loading of the temperature field of research, the analysis of environment includes variable temperature load, surface vessel, warehouse storage for a long time, cooling solidification, by special heat load, etc., the results verify the reliability of the principle, put forward some new model and algorithm formula, and provide certain guiding significance to the reality.

Analysis of the fast hydrogen release from the metal hydride container applied in automotive industry

This article discusses the analysis of the hydrogen release consequences from a metal hydride container. It is focused on the hydrogen flow behaviour and temperature field change, which participates in the reduction of hydrogen desorption kinetics. Despite the thermal input of Peltier thermopiles used for heating the container, at rapid hydrogen leakage the metal hydride material cools down and this affects the self-regulation of the volume flow rate. The article describes the investigation of the container operating parameters (temperature field, pressure, flow rate, thermal input) during a rapid release of hydrogen with subsequent analysis of pressure effects on the obstacles located in the surrounding environment during an undesired hydrogen explosion. The concluding part of the article explains the mathematical relationship between the pressure of the shock wave and the distance between the obstacle and the centre of the explosion.

Tendencies of long-term changes of temperature fields, salinity and water level of the North-Western part of the Black Sea

The paper analyzes the variability of hydrological characteristics of the North-Western part of the Black for different temporal scales: long-term, seasonal and synoptic. The traditional methods of geographic investigations, such as comparative-geographic, retrospective and cartographic methods, were used. When analyzing sea level data packages and thermohaline characteristics mathematical methods, including statistical, correlation and regression analysis, were used. As a result of the conducted research quantitative estimates of tendencies of long-term changes of the thermohaline characteristics and level in the North-Western part of the Black Sea were received. Over the period of 1982-2005 an increase of water temperature in the North-Western part of the Black Sea was observed: in winter water temperature in the surface layer increased by 2оC, in the bottom layer – by more than 2оC. Over the period of 1990-2005 an increase of an average annual water temperature in Odesa area constituted 1,2°C. The most considerable and statistically significant temperature increase took place during the summer hydrological season: an average summer temperature increased during this period by 2,7оC. During transitional seasons (autumn and spring) there was also a tendency of temperature increase, however, statistically significant trend was observed only during the autumn period. There is a statistically significant negative trend observed for long-term changes of salinity. For the period of 1990-2005 an average annual salinity decreased by 1.36 ‰. A tendency of salinity decrease was observed for all seasons of the year, however, statistically significant trends are observed only in winter and summer. A close relationship between long-term changes in water salinity and runoff of the Dnieper River was also established. A sea level rise is observed at all stations of the North-Western part of the Black Sea. Over the period of 1947-2012 an average annual sea level in Odesa increased by 14 cm. An analysis of climatic changes of wind-induced sea level fluctuations showed that the frequency of surges of varying intensity remained almost unchanged, however, the frequency of sweeps changed significantly. Over the period of 1980-2012, as opposed to the period of 1947-1979, the frequency of minor sweeps (no more than 30 cm) increased, and the frequency of significant (more than 30 cm) and very significant (more than 50 cm) sweeps, on the contrary, decreased by about 5%-6%. Changes of wind-induced sea level fluctuations' character harmonize with wind direction and wind speed over the North-Western part of the Black Sea.

Multimodal temperature sensing using Zn2GeO4:Mn2+ phosphor as highly sensitive luminescent thermometer

Motivated from increasing demands of non-contact temperature sensing, here Mn2+ doped Zn2GeO4 (ZGO) phosphor is produced to explore the temperature dependencies of its optical characteristics. Temperature dependencies of emission intensity and luminescence decay lifetime of Mn2+ in the range from 250 K to 420 K are investigated. The maximum relative sensitivities achieved are 4.5% K−1 and 4.6% K−1 for temperature sensing modes of emission intensity and decay lifetime, respectively. In order to realize temperature imaging, a temperature sensing scheme is employed based on time-resolved technique with the help of an intensified charge coupled device (ICCD) and a fluorescent microscope, where the luminescence integral intensities ratio of obtained images for two time segments is calibrated to measure the temperature. A maximum relative sensitivity of 12.2% K−1 is achieved and the best temperature resolution is about 0.68 K. Employing the temperature imaging system we built, the temperature distribution of micro circuit on a printed circuit board (PCB) has been monitored with high temperature and spatial resolution. The results may offer a significant advance in the development of temperature visualization for precise distributions and change of temperature field.

Dynamic temperature compensation model based on nonuniform temperature field change

As the development of infrared temperature measurement technology, the research of the surface temperature monitoring system of rotary kiln based on infrared scanning has attracted the attention of experts in related fields. However, the non-contact characteristics of infrared bring many irresistible factors to the temperature measurement accuracy of rotary kiln, one of which cannot be ignored is the ambient temperature. In order to ensure the accuracy and stability of the system in temperature monitoring, the current research focuses on analyzing the influence of ambient temperature and establish a reasonable and effective temperature compensation model. In this paper, we analyze the influence of ambient temperature on temperature measurement in rotary kiln is analyzed based on the components of radiation received by infrared detector. The radiation received by infrared detector includes target radiation, reflection of ambient radiation and atmospheric radiation. It is found that the environmental temperature mainly affects the reflective radiation and atmospheric radiation of the environment, which cause the accuracy of temperature measurement drop. Therefore, this paper analysis the influence of ambient temperature on these two parts, and we put forward a dynamic temperature compensation model Based on nonuniform temperature field change, which improves the accuracy of temperature measurement by 5 percentage points.

Effect of Fixed and Removable Gas-Injection Patterns on the Expansion of Reaction Zones during Underground Coal Gasification

The expansion pattern of the three reaction zones, including oxidation, reduction, and dry distillation zones in the underground coal gasification (UCG) process, is recognized to be different using various gas-injection patterns, on account of which the corresponding stability and syngas components are notably distinguished. The current work carried out UCG model tests in a removable gas-injection point (receded five times). During the stable gasification process, the temperature field map and changes in syngas composition were monitored to determine the area proportions among the three zones and their expansion rates. The differences in the expansion of the three zones between fixed and removable gas-injection points were then explained according to cavity growth. The results showed that the UCG process using a removable gas-injection point exhibited a better performance than that using a fixed point in some aspects, including gasification stability, syngas calorific value, area ratio of the reduction zo...

Modeling of heat source in grinding zone and numerical simulation for grinding temperature field

To accurately predict temperature field changes of the subsurface of the workpiece, a heat source model of the contact zone in the real grinding process is established using the temperature matching method according to the principle of anti-heat source and the actually measured grinding temperature. The finite element method is utilized to simulate the change of the grinding temperature field of the workpiece, and make a comparison with the triangular heat source model. The grinding temperature field at different depths of the workpiece in the grinding zone is measured using the K-type thermocouple. The results indicate that the heat source model according to the temperature matching method has a good consistency with the measured values at different depths on the subsurface. The relative errors are between 1.8% and 8%. Comparing with the triangular heat source model, the distribution accuracy of the predicted temperature field is improved almost 2 times.

Gas-cooled nuclear reactor core shaping using heat exchange intensifiers

The need to shape reactor cores in terms of coolant flow distributions arises due to the requirements for temperature fields in the core elements (Safety guide No. NS-G-1.12. 2005, IAEA nuclear energy series No. NP-T-2.9. 2014, Specific safety requirements No. SSR-2/1 (Rev.1) 2014). However, any reactor core shaping inevitably leads to an increase in the core pressure drop and power consumption to ensure the primary coolant circulation. This naturally makes it necessary to select a shaping principle (condition) and install heat exchange intensifiers to meet the safety requirements at the lowest power consumption for the coolant pumping. The result of shaping a nuclear reactor core with identical cooling channels can be predicted at a quality level without detailed calculations. Therefore, it is not normally difficult to select a shaping principle in this case, and detailed calculations are required only where local heat exchange intensifiers are installed. The situation is different if a core has cooling channels of different geometries. In this case, it will be unavoidable to make a detailed calculation of the effects of shaping and heat transfer intensifiers on changes in temperature fields. The aim of this paper is to determine changes in the maximum wall temperatures in cooling channels of high-temperature gas-cooled reactors using the combined effects of shaped coolant mass flows and heat exchange intensifiers installed into the channels. Various shaping conditions have been considered. The authors present the calculated dependences and the procedure for determining the thermal coolant parameters and maximum temperatures of heat exchange surface walls in a system of parallel cooling channels. Variant calculations of the GT-MHR core (NRC project No. 716 2002, Vasyaev et al. 2001, Neylan et al. 1994) with cooling channels of different diameters were carried out. Distributions of coolant flows and temperatures in cooling channels under various shaping conditions were determined using local resistances and heat exchange intensifiers. Preferred options were identified that provide the lowest maximum wall temperature of the most heat-stressed channel at the lowest core pressure drop. The calculation procedure was verified by direct comparison of the results calculated by the proposed algorithm with the CFD simulation results (ANSYS Fluent User’s Guide 2016, ANSYS Fluent. Customization Manual 2016, ANSYS Fluent. Theory Guide 2016, Shaw1992, Anderson et al. 2009, Petrila and Trif 2005, Mohammadi and Pironneau 1994).

Study on break of thermal stratification in container targeted to thermodynamic vent system for future spacecraft

In the future space exploration mission, transfer vehicle using cryogenic propellant and oxidizer will be likely operated. Thermal management systems, such as thermal insulation, pressure control, and reduction of boil off gas must be installed on transfer vehicle since cryogenic fluid has high volatile characteristics. Final target of this study is the development of thermodynamic vent system (TVS) utilizing jet mixing. Numerical simulation and ground based experiment for thermal and fluid behaviours in tank partially filled with liquid nitrogen were conducted. Thermal stratification in tank was formed by creating heat input from side wall, and change of temperature field and break of thermal stratification by jet mixing were investigated. Numerical results were evaluated by comparing with experimental results.

Study on cable fire spread and smoke temperature distribution in T-shaped utility tunnel

With the rapid development of the economy, underground utility tunnel has become an important infrastructure and “lifeline” for major cities. Through the investigation of the fire form of the pipe gallery, it was found that the most dangerous fire in the underground utility tunnel is the integrated pipe gallery power cabin, which is mainly represented by cable fires. This paper mainly focuses on the special T-shaped structure of the underground pipe gallery. The FDS software is used to simulate the occurrence of cable fires, analyzing the temperature field change of the corridor and the temperature of the ceiling of the T-shaped corridor with the changing of the fire source power. The cable fire is how to spread at the T-junction. The situation results provide a certain reference for the actual fire extinguishing of underground T-shaped cable duct corridors.

Suppression Method of Jump Points for Multipole Magnetic Encoder at Low Temperature Based on Single-Pole Angle Value Fitting

To eliminate the jump points of multipole angle values after subdivision at low temperature, the magnetic field and temperature field characteristics of a multipole magnetic encoder are analyzed in this study, and the effect of changes in magnetic field strength and temperature field on the precision of angle values is studied. To eliminate the jump point of multipole angle values caused by changes in the temperature field, the suppression method based on single-pole angle value fitting is proposed. The error between the single-pole and multipole angle values is tabulated by the oversampling linear interpolation method, and the precision of fitting single-pole to multipole angle values is effectively improved. The error of the angle value caused by changes in the temperature field is studied and analyzed, and the relationship between the jump angle values and the pole number of the multipole magnetic encoder is obtained. Furthermore, the jump point is compensated for by the jump range of the multipole angle values. Finally, the angle accuracy of the multipole magnetic encoder in a cryogenic chamber is experimentally verified. The experimental results show that the low-temperature jump point compensation method proposed for the multipole magnetic encoder in this paper can effectively suppress the jump of the angle values.