Temperature Distribution Characteristics Research Articles

Temperature distribution characteristics of linear fires in utility tunnels under the influence of sealing ratios and vertical positions of the fire source

This study delves into two key factors affecting fire development process and longitudinal ceiling temperature attenuation characteristics in a utility tunnel: the sealing ratios and the vertical positions of the linear fire source. The evolution process of linear fire is typically divided into five stages. In the stable combustion stage, the flame height at the end of the liner fire source is observed to be higher than that at the center. During the rapid loss stage of mass, the mass loss rate peaks and then stabilizes for a period of time, the maximum peak growth rate is 1.35 (the fire source is located at position 02), the duration shortens as the distance between the liner fire source and the ceiling decreases and the sealing ratio increases. When the sealing ratio is 100 %, the maximum temperature growth rate is 2.25 with the change of fire source position. The ceiling temperature in the upper part of the linear fire zone is lower in the center and higher on both sides, however, the distribution is asymmetric. A mathematical model of longitudinal ceiling temperature attenuation is established. The results may provide guidance for the control of linear fires in long-narrow confined spaces.

An enhanced heat transfer method based on the electrocapillary effect of gallium-based liquid metal.

As electronic products become smaller and more powerful, there is an increasing need for effective heat dissipation. An effective heat exchange method is necessary for the equipment to function reliably in a compact space. To tackle the limitations of current microfluidic cooling technology, including difficulty in manufacturing, maintenance, and cost reduction, a heat exchange method with a simple system is proposed in this work. This method is based on the electrocapillary effect, using eutectic gallium-indium alloy droplets with high thermal conductivity, surface tension, and controllability as the basic unit. An electric field is applied to generate unevenly distributed charges in the electric double layer on the droplet surface, thereby creating a surface tension gradient that can drive the surrounding solution to flow. Simultaneously, the oscillation of the droplet can also intensify the disturbance of the solution. The violent disturbance of the solution causes the heat transfer mode to change from conduction to convective heat transfer and greatly reduces the thermal resistance, resulting in a substantial increase in heat flux. For this heat transfer method, the temperature distribution and flow characteristics of the solution in low-frequency oscillating and direct-current-biased alternating current electric fields are studied, and the effect of voltage, frequency, and the number of droplets on heat transfer enhancement is clarified. Compared with conduction without internal disturbance, the heat flux can be increased by up to 110% based on the combined effect of two droplets. This work provides a solution for enhancing the heat transfer of microfluidics.

Experimental investigation on temperature distribution characteristics inside the condensing tube of the R134a two-phase natural circulation loop

Temperature distribution of two-phase flow inside the condensing tube can effectively reflect the heat transfer characteristic of the fluid, playing a pivotal role in the study of heat transfer in two-phase flow systems. In this study, we use the stainless steel capillary sealed distributed fiber Bragg grating (S-DFBGs) to measure and characterize the temperature distribution of R134a fluid inside the condensing tube under steady-state (pump-driven two-phase circulation) and unsteady-state (type I and II density wave instabilities in two-phase natural circulation loop) conditions, and the frequency and time domain characteristics of the fluid temperature distribution inside the tube has been investigated in detail. Through frequency-domain analysis, the temperature spectrum inside the condensing tube can indentify two types of the instability together with flowrate and pressure. Through time-domain analysis, temperature distribution inside the condenser can dermine the phase transition point, hence the condensation length. Moreover, two types of the instability exhibit different temperature fluctuation characteristics, providing reliable and effective information for further research on two phase natural circulation instability mechanisms.

Study on Shutter Heating Performance of Gas Turbine Intake System

Abstract Aiming at the anti-icing and de-icing requirements of gas turbine intake system, study the heating performance of a typical shutter vane, and compares and analyzes the influence of different ambient temperature and different electrothermal pipe heat generation rate on vane temperature distribution and heat transfer characteristics. The results show that the air convection at different positions on the blade surface of the louver leads to the difference in the temperature distribution of the upper and lower surfaces of the blade, as well as the leading edge and trailing edge of the blade, and the leading edge of the blade, as the area with the lowest overall temperature distribution of the blade, should be focused on in the design of anti-icing and de-icing systems. Increasing the heat production rate of the electric heating tube, there is more heat flow near the midline of the blade, which makes the temperature rise at this position the highest, and it is necessary to pay attention to the energy waste and blade damage caused by local overheating of the blade. Therefore, when the ambient temperature increases from 245.15 K to 318.15 K, the leaf temperature increases from 248.73 K to 322.74 K, and the temperature rise also increases from 3.58 K to 4.59 K. The electrothermal technology can be used to the anti-icing and de-icing of the intake system shutters on the basis of choosing the heat generation rate of the electrothermal tube reasonably.

Experimental study on fireproof of aviation lubrication oil tank

Abstract This paper presents an experimental study on the fireproof performance of aeroengine lubrication oil tanks. By constructing a simplified lubrication oil tank model and simulating the harsh operating conditions of engine fires, the oil tank was exposed to flames generated by a standard burner for testing. The study monitored and recorded key parameters such as temperature, pressure, flow rate, and phase changes within the tank. The results indicate significant differences in the temperature distribution characteristics of the tank walls under different inlet temperatures and flow conditions. In the rigorous 15-minute flame test, all tests successfully completed the fire verification process.

Finite element parameterization modeling and thermal performance analysis for woven fabrics using unit cell models

Addressing the lengthy testing times, complex procedures, and high costs of current methods for evaluating fabric thermal properties, this study introduces a numerical simulation and prediction approach for determining fabric thermal conductivity and thermal effusivity. Using ANSYS/APDL finite element software, we developed a parametric model to effectively simulate and analyze temperature distribution characteristics across various woven structures, fabric densities, and materials for warp and weft yarns. The thermal conductivity and thermal effusivity of the fabrics were calculated using a unit cell structure model and validated through experimental results. Our findings demonstrate that ANSYS/APDL parametric modeling can be effectively applied to various fabrics with different woven structures, fabric tightness levels, and materials for both warp and weft yarns. The absolute error between the simulated and experimental thermal conductivity results is within 5%, and the absolute error for thermal effusivity is within 7%, indicating a strong agreement between simulation and experiment. Additionally, our results reveal that increasing fabric density leads to higher thermal conductivity and thermal effusivity.

Research on gas-liquid interface parameters related to thermal performance of frost-free evaporator of air source heat pump

Direct spray frost-free air source heat pumps (FFASHPs) base on liquid desiccant solutions are a more promising renewable energy technology for developing net-zero emission buildings. In order to improve the thermal performance of the frost-free evaporator, a numerical mode was established based on the penetration theory and the two-film theory to reveal the interfacial heat and mass transfer mechanism of LiCl solution falling film absorption on the air side of the frost-free evaporator. The distribution characteristics of temperature, water vapor concentration, effective diffusion coefficient, morphology, velocity and pressure at the interface under different air Reynolds numbers and temperatures were analyzed. The results show that the distribution uniformity of interface parameters has a greater effect on heat transfer performance than its average value. The critical Reynolds number is 391.0 under the present study, and the distribution uniformity of interface parameters and the intensity of interface fluctuation are improved, and the thermal performance reaches the peak. The COP of FFASHP system can be improved effectively when the frost-free evaporator is operated under the critical condition matching its parameters. The purpose of the study is to provide theoretical support for the performance improvement and efficient operation of frost-free evaporators.

A Circulation Study Based on the 2022 Sino–Vietnamese Joint Survey Data from the Beibu Gulf

This study analyzed the horizontal and vertical distribution characteristics of temperature and salinity in the central and eastern regions of the Beibu Gulf, based on conductivity measurements in summer 2022, temperature, and depth (CTD) measurement data from the Sino–Vietnamese cooperative project “Demonstration Study on Ecological Protection and Management in Typical Bays: Seasonal Survey of the Beibu Gulf”. Furthermore, the study utilized the computational results from the numerical Finite-Volume Coastal Ocean Model (FVCOM) to elucidate the intrinsic patterns that formed the temperature and salinity distribution characteristics in August 2022 from both thermodynamic and dynamic perspectives. The circulation in the Beibu Gulf drives external seawater to move northward from the bay mouth. During this movement, numerous upwelling areas are created by lateral Ekman transport. The formation of different scales of cyclonic and anticyclonic vortices and current convergence zones is influenced by topography, runoff, and the water flux from the Qiongzhou Strait, which are key factors in the formation of upwelling and downwelling. The surface circulation in August 2022 significantly differed from the 20-year average surface circulation, with an influx of 1.15 × 104 m3/s more water entering the Beibu Gulf compared to the multi-year average. The water flux from the Qiongzhou Strait is a critical factor affecting the circulation patterns in the Beibu Gulf. The northeastern waters of the Beibu Gulf are characterized by current convergence zones, where extensive upwelling occurs. The rich nutrient salts in these areas promote the reproduction and growth of phytoplankton and zooplankton, making this the most favorable ecological environment in the Beibu Gulf and serving as a natural reserve for fisheries, coral reefs, dugongs, and Bryde’s whales.

Evaluation of Boundary Layer Characteristics at Mount Si’e Based on UAV and Lidar Data

The atmospheric boundary layer is a crucial transitional region connecting the surface with the free atmosphere, playing a bridging role in land-sea-air interactions and the interactions between different atmospheric layers. This study utilizes rotary-wing UAVs, high-resolution lidar, and WRF simulation data to analyze the vertical distribution characteristics of temperature, humidity, wind speed, and wind direction boundary layer over the Mount Si’e region in 4–6 April 2024. The results indicate that the boundary layer temperature decreases with increasing altitude, reaching up to 18°C, while humidity decreases with height, dropping to as low as 35%. Daytime wind speeds range from 4 to 8 m/s, decreasing to 2 to 4 m/s at night. The boundary layer height can reach up to 900 m during the day and drops to 100–200 m at night, showing distinct diurnal variation characteristics. UAV observations are in good agreement with lidar and WRF simulation results, highlighting the application value of UAVs in high temporal and spatial resolution boundary layer studies. The study also reveals the significant impact of complex terrain on boundary layer characteristics, providing scientific insights into the dynamic and thermal processes of the boundary layer and offering reference value for improving regional weather forecasting and numerical simulations.

Numerical Analysis of Spray Evaporation Process in Desuperheater

Abstract The cooling water is sprayed into the desuperheater to regulate the temperature of the superheated steam. Computational fluid dynamics (CFD) was applied to investigate the spray evaporation process in the desuperheater. Discrete phase model (DPM) was applied to describe the gas-liquid two-phase flow characteristics based on the Eulerian-Lagrangian approach. The Rosin-Rammler distribution and TAB model were used for the description of the primary and secondary droplet breakup, respectively. The coupling effect of gas-liquid two-phase, influence of temperature on latent heat, the stochastic collision and coalescence of droplets were considered in the CFD model. The numerical results show good agreement with the plant data. The hydrodynamics and temperature distribution characteristics were analysed. The influence of water mass flow rate and orifice dimensions on temperature distribution and temperature non-uniformity was further investigated. The results indicate that increasing the water flow rate can improve the desuperheating ability, but it will make the temperature uniformity worse. Under the same operating conditions, smaller orifice diameters are beneficial for production of droplets with smaller size, leading to better desuperheating ability.

Thermal radiation imaging technology and sensor assisted calculation of sports training technology simulation

With the development of sports training science and technology, the real-time monitoring of athletes’ physical condition and training effect is becoming more and more important. As a non-contact measurement method, thermal radiation imaging technology can capture the changes of athletes’ body surface temperature efficiently and in real time, and provide relevant information about physiological state and performance indicators. This paper discusses the application of thermal radiation imaging technology in sports training to help measure athletes’ physical state and training effect, so as to provide scientific basis for improving training efficiency and reducing sports injuries. In this paper, the high resolution thermal imaging equipment is used to systematically analyze the thermal radiation imaging of athletes, and the physiological index monitoring and data processing technology are combined to dynamically observe the temperature distribution and change characteristics of athletes under different training states. Through comparative analysis, the correlation between the data provided by thermal radiation imaging technology in the training process and the traditional physiological indicators was evaluated. The results show that thermal radiation imaging technology can effectively reflect the heat distribution and local body temperature changes of athletes during training. Compared to traditional physiological feedback data, the technology has significant advantages in quickly identifying excessive fatigue and potential injuries in athletes, especially during high-intensity training, and can provide early warning of associated risks. The application of sensor-assisted measurement system will further enhance the accuracy and effectiveness of sports scientific research and provide important support for athletes’ scientific training and health management.

Core-winding of Sodium Cold Fast Reactor Based on CFD Method Numerical Study of Flow Characteristics

Abstract Liquid metal cooled fast reactor often uses spiral winding wire as the positioning component of fuel rod bundle. Besides fixing, spiral winding has the functions of strengthening subchannel mixing and heat transfer. These characteristics have a very important impact on the internal flow temperature characteristics of the fuel assembly and the safety of the core system, so it is necessary to conduct in-depth research on the flow field distribution of the fuel rod bundle channel with wire wound, the transverse and axial flow characteristics of the edge channel and its internal channel, the flow characteristics of the circulation and eddy current, the local temperature field, and the outlet temperature distribution characteristics. In the actual research, there are some problems such as high cost, difficulty and high risk to carry out thermal hydraulic characteristic experiment directly. This paper uses CFD fine simulation technology to study 7 rod bundles with wire winding, uses Fluent meshing to partition high-quality polyhedral unstructured mesh, uses ANSYS Fluent to conduct numerical simulation, studies the influence of the presence of rod bundles with wire winding on the distribution of flow field and local temperature field, and forms a mature and reliable simulation experiment scheme. The temperature change curve and lateral mixing phenomenon obtained by CFD simulation were investigated. The outlet temperature differences of side channel, inner channel and corner channel were investigated, and the convective heat transfer characteristics between channels were investigated due to the existence of wire winding.

Exploring the integration of InSAR data into climate‐driven creep models to assess slow‐moving landslide dynamics

AbstractThe deformation behavior of slow‐moving large landslides is often governed by rainfall characteristics. Based on observational data such as precipitation, deformation measurement, and pore water pressure measurements in the slip zone, in many cases a strong correlation between strong rainfall events, a time‐delayed increase of pore water pressures in the slip zone, and, simultaneously to this, an increase of the deformation rate of the landslide can be found. Based on such detailed data, calculation models, which couples the relation between rainfall characteristics and the development of pore water pressures in the slip zone on one hand and the deformation behavior of the slope on the other, can be developed and be used for a better understanding and a prediction of deformation behavior of such slow‐moving landslides. Climate change issues will lead to a change in rainfall frequency and magnitude and annual temperature distribution characteristics in several regions worldwide, which will also lead to changes in the deformation behavior of such large landslides. In this contribution, satellite‐based interferometric synthetic aperture radar (InSAR) data are discussed to be used as source for deformation measurements as bases for prediction models describing the rainfall‐triggered deformation behavior of slow‐moving landslides.

Research on temperature distribution characteristics of oil‐immersed power transformers based on fluid network decoupling

AbstractDue to the complex structure and large size of large‐capacity oil‐immersed power transformers, it is difficult to predict the winding temperature distribution directly by numerical analysis. A 180 MVA, 220 kV oil‐immersed self‐cooling power transformer is used as the research object. The authors decouple the internal fluid domain of the power transformer into four regions: high voltage windings, medium voltage windings, low voltage windings, and radiators through fluid networks and establish the 3D fluid‐temperature field numerical analysis model of the four regions, respectively. The results of the fluid network model are used as the inlet boundary conditions for the 3D fluid‐temperature numerical analysis model. In turn, the fluid resistance of the fluid network model is corrected according to the results of the 3D fluid‐temperature field numerical analysis model. The prediction of the temperature distribution of windings is realised by the coupling calculation between the fluid network model and the 3D fluid‐temperature field numerical analysis model. Based on this, the effect of the loading method of the heat source is also investigated using the proposed method. The hotspot temperatures of the high‐voltage, medium‐voltage, and low‐voltage windings are 89.43, 86.33, and 80.96°C, respectively. Finally, an experimental platform is built to verify the results. The maximum relative error between calculated and measured values is 4.42%, which meets the engineering accuracy requirement.

Spectral properties regulation for the performance improvement of solar-driven methane dry reforming reactor based on the photothermal synergistic catalysis

With the development of chemical industry, many chemical reactions are expected to be directly driven by solar energy. Among them, methane dry reforming (MDR) is a highly promising reaction system. Since all the energy required for MDR comes from solar energy, the temperature distribution and reaction characteristics in the reactor are determined by radiation transportation, and therefore regulating the optical properties according to the spectral distribution characteristics becomes necessary for improving the chemical conversion performance of the reactor. In this paper, aiming at the specific strengthening mechanism of different spectra in photothermal synergistic catalysis, the spectral response characteristics in the reactor were purposefully regulated, so as to achieve the improvement of reactor efficiency and reaction conversion performance. By adjusting the optical properties of compound parabolic concentrator (CPC) and porous catalytic absorber (PCA) in a cavity reactor, the CO2 conversion can be increased by 68.52%, the CH4 conversion can be increased by 54.48%, and the solar-fuel efficiency can be increased to 6.16%. This indicates that the selectivity of different bands of full spectrum can significantly affect the reactor performance. Through the above research, this paper aims to provide a new optimization idea for the photothermal reactor.

Experimental study of heat pipe start-up characteristics and development of an enhanced model considering gas diffusion effects

Heat pipe-based cooling reactors, offering passive heat transfer and modularity, are becoming the preferred type for micro-reactors. Alkali metals such as sodium, potassium and lithium are usually used as the working medium of the heat pipe, which is in a frozen state at normal atmospheric temperature. After heating the heat pipe, the working medium will melt and enter the gas chamber, and its flow state will undergo a transition from discontinuous flow to continuous flow. The start-up of the heat pipe affects the heat export and neutron physical characteristics of the heat pipe cooling reactor. Building a model of heat pipe can predict the start-up of heat pipe effectively, which can be helpful to study the start-up and safety analysis of heat pipe cooling reactor. In this paper, a heat pipe flat-front model considering the gas diffusion effect is established, and the gas temperature distribution characteristics in the non-continuous flow region are obtained through the start-up experiment of heat pipe. The calculated results of the flat-front model considering gas diffusion effect and the vertical flat-front model are compared with the experiment. The results show that the model in this paper can better describe the start-up of heat pipe. At the same time, the evaporation and condensation coefficient model based on temperature change is used to deal with the evaporation and condensation mass flow at the phase change interface of the heat pipe, which can better describe the temperature difference at the interface of the heat pipe.

Distribution characteristics of soil moisture and temperature under different land use types in the deep profile of loess area in northern Shaanxi, China.

Understanding the effects of different land use modes on the spatial and temporal variations of soil moisture and temperature in the deep profile and revealing the regulatory effects of various vegetation covers on regional water and heat resources can provide a theoretical basis for the optimization of land management and vegetation restoration. Taking the advantage of different land use patterns in the Liudaogou watershed in the northern part of Loess Plateau, we monitored soil moisture content as well as temperature in the 0-1000 cm soil layer in 2022 to analyze the temporal variation and vertical profile distribution characteristics of soil moisture and temperature under four land use modes (woodland, grassland, farmland, and wild grassland). The results showed that soil moisture and temperature distributions varied significantly across different land use types. In the growing season (April-October), total soil water storage in the 0-1000 cm soil layer of the four land use types, in a descending order, was as follows: soybean farmland (1393 mm), wild grassland (1374 mm), Caragana korshinkii forest (1218 mm), and alfalfa grassland (557 mm). Soil moisture of C. korshinkii forest and soybean farmland changed obviously in the 0-300 cm soil layer, and that of wild grassland and alfalfa grassland was in 0-500 and 0-200 cm soil layers, respectively, while soil moisture of deep soil layers fluctuated little. The impact of land use modes on soil temperature was primarily manifested in the 0-200 cm soil layer, and the depth was up to 300 cm. The depth of precipitation infiltration replenishment of the four land use modes was approximately 200 cm. The depth of soil moisture depletion was 200 cm in both C. korshinkii forest and alfalfa grassland, and was 100 cm in soybean farmland and wild grassland. Soil hydrothermal processes in the deep profile varied across vegetation types.

Infrared temperature distribution characteristics and state assessment method of sandstone under tension and compression stress

Abnormalities in infrared radiation temperature (IRT) often accompany the loading In this investigation, stress experiments and splitting tests were conducted on sandstone to investigate the IRT characteristics of sandstone under various loading conditions. The results shows that the Maximum Infrared Radiation Temperature (MAXIRT) increases by up to 5 °C, while in splitting tests, the minimum infrared radiation temperature (MINIRT) decreases by approximately 1.5 °C. Compared to the average infrared radiation temperature (AIRT), MAXIRT is more sensitive to compressive stress, whereas (MINIRT) is more responsive to tensile stress. The correlation between IRT indicators and stress were further analyzed. The findings reveal a positive correlation between IRT and compressive stress. At low stress levels, the correlation coefficient fluctuates between −0.4 and 0.6, generally showing low correlation. As stress increases, the correlation coefficient rises, reaching above 0.8, indicating a high correlation. Tensile stress exhibits a negative correlation, with a consistent trend. Additionally, a statistical analysis of the frequency distribution of IRT under different stress conditions was conducted, followed by hypothesis testing. The results demonstrate that the probability distribution of IRT during loading follows a skewed normal distribution. The changes in skewness can be divided into three stages: initial fluctuation, stable variation, and abrupt failure. Under compressive stress, a right-skewed distribution is observed, with skewness exceeding 3.5 before fracture and reaching above 10 near fracture. Under tensile stress, a left-skewed distribution is noted, with skewness reaching −4.5 near fracture. These findings contribute to the assessment of rock stress states and provide early warning information for predicting rock failure.

Simulation and experimental analysis of dynamic thermal rise relaxation characteristics for dry-type distribution transformer

Abstract The temperature distribution characteristics of dry-type distribution transformers reflect their overall performance and quality. Distribution transformer daily load changes dramatically, its temperature fluctuates within a certain range. However, most of the research results on transformer temperature rise focus on the steady-state temperature characteristics of transformers, and lack of research related to dynamic temperature rise characteristics. This paper carries out a multi-physics coupling simulation and experimental verification of the dynamic temperature rise relaxation characteristics. The simulation uses the “electromagnetic-flow-thermal” multi-physics coupling analysis method to simulate the steady-state temperature rise characteristics and dynamic temperature rise relaxation characteristics of windings under different load rates. Then, this paper also explores the correlation between the dynamic temperature rise relaxation characteristics and load rate at the typical positions of high-voltage windings and low-voltage windings. The results show that the temperature rise of the winding shows the law of increasing the saturation index function with the increase of the load application time at any load rate. A quantitative characterization model of dynamic temperature rise relaxation behavior at different positions of transformer windings is constructed. It is found that the steady-state temperature rise value of different parts of the winding increases regularly as a power function with the increase of load rate, while the constant value of dynamic temperature rise relaxation time in different parts of the winding decreases as a power function with the increase of load rate. The verification results of the quantitative characterization model of dynamic temperature rise relaxation behavior show that the maximum error of the measured and theoretical steady-state temperature rise value is only 1.56 K, and the maximum error of the constant value of dynamic temperature rise relaxation time is only 0.082 h. These findings provide valuable insights into the performance and quality of dry-type distribution transformers, and can help improve their design and operation for better efficiency and safety.

Study on the maximum ceiling temperature and downstream temperature distribution in inclined tunnel fire

Constrained by various factors, including terrain, tunnels frequently exhibit slopes. While existing research on fires in inclined tunnels predominantly focuses on the characteristics of smoke flow in large slope tunnels, there is a notable lack of attention given to the study of micro-slope tunnels and important factors such as induced air inflow. Therefore, in this paper, the numerical simulation method is used to study the maximum ceiling temperature rise and downstream temperature distribution in inclined tunnel fire under the conditions of micro-slope and large slope. The results show that the main factors affecting the ceiling temperature rise are not only the tunnel slope, but also the HRR and the downstream length. These effects can be expressed by the stack effect intensity. When the inclined tunnel fire occurs, the maximum ceiling temperature and the downstream temperature distribution characteristics show two states. When the stack effect in the tunnel is diminished, there is no significant alteration in the maximum ceiling temperature and temperature distribution within the tunnel when compared to a horizontal tunnel. In a tunnel with a strong stack effect, the maximum temperature decreases as the stack effect increases, and the temperature distribution differs greatly from a horizontal tunnel. The theoretical analysis of this paper identifies the demarcation point of the two state changes as the dimensionless induced air inflow velocity of 0.1. On this basis, a piecewise prediction model for the maximum ceiling temperature of the inclined tunnel fire is established. Because the temperature distribution between the fire source and the maximum temperature position is not regular. Thus, using the maximum ceiling temperature as a reference point, an accurate segmented prediction model of temperature distribution is proposed for downstream Region 1. This study offers guidance for designing tunnel structures with high-temperature resistance and assessing safety conditions within the tunnel.