Uniformity Of Temperature Field Research Articles

Dynamic Response of Phase Change Heat Exchange Unit with Layered Porous Media for Pulsed Electronic Equipment

Effective heat dissipation challenges transient high-power electronic devices in hypersonic vehicle cabins. This study introduces a Phase Change Heat Exchange Unit with Layered Porous Media (PCHEU–LPM) employing pulsed heat flow at the top and forced convection at the bottom. The primary aim was a comparative parametric study analyzing the thermal response of the heating surface under pulsed heat flow conditions. The geometric model was generated using electron microscopy images of manufactured objects and the numerical model was established based on the enthalpy–porosity method. Numerical simulations explored amplitude and frequency effects on pulsed thermal excitation, evaluating temperature and phase fields. A comprehensive time-frequency transformation assessed the temperature response. The results indicated an initial decrease and subsequent increase in interface temperature fluctuation with pulse heat flux amplitude growth. Temperature field uniformity correlated with natural convection strength in two-phase and liquid-phase regions. At mid and low frequencies, the phase change process increasingly suppressed interface temperature fluctuations. Optimal pulse thermal excitation selection was crucial for minimizing temperature fluctuations while maintaining the interface temperature within the expected phase transition range. In conclusion, a novel design concept is posited herein, aiming to enhance surface temperature uniformity and broaden the applicability of electronic devices through the manipulation of porosity rates.

Study on Temperature Field Uniformity of Dynamic Induction Heating for Camshaft of Marine Diesel Engine

This paper focuses on the study of the induction heating process of a camshaft in a marine diesel engine. A three-dimensional finite element model for dynamic induction heating is established using the finite element method of multi-physical field coupling, aiming to investigate the temperature uniformity of the cam during this process. Three elements are analyzed in this study: the moving speed, the gap between the induction coil and the workpiece, and the width of the induction coil. These factors allow for an analysis of the temperature distribution in the thickness direction and contour line direction of the cam under various conditions. On this basis, an equivalent parameter about the temperature uniformity in the thickness direction of the cam is proposed to guide the selection of the camshaft induction heating process parameters.

Simulation analysis of microwave sintering of recycled building bricks based on three-phase porous medium model

The visualization and quantification characteristics of numerical simulation can overcome many obstacles caused by experimental conditions and contribute to the development of the microwave sintering mechanism of recycled building bricks (RBB). However, existing research has paid little attention to the numerical simulation of the microwave sintering of RBB. This study considers the phase transition and mass transfer of three-phase porous media, and establishes a fully coupled model of electromagnetic, heat transfer, and three-phase porous media to study the thermal behavior of RBB under microwave irradiation. The results indicate that the electric field inside the cavity exists in a non-uniform form with high and low energy regions. The addition of RBB will see a redistribution of the electric field in the cavity. The non-uniform distribution of electric field and the selective heating of microwaves result in the appearance of hot and cold regions inside RBB during sintering. Phase transition and mass transfer are beneficial for improving the uniformity of temperature field. The geometric size and position of RBB will affect the uniformity of the temperature field of RBB, and adding SiC board can be effective to improve the uniformity.

SIMULATION AND EXPERIMENTAL RESEARCH STUDIES ON TEMPERATURE FIELD FOR THE PRODUCTION OF DIAMOND-COATED MILLING TOOLS BY HFCVD DEVICE WITH SEPARATED WORKTABLES

Diamond-coated tools have extremely extraordinary physical and chemical properties and have become ideal tools for machining the emerging materials that are hard to machine. In mass production of diamond-coated milling tools, the homogeneity of diamond coatings has always been sought for and is highly influenced by the uniformity of temperature field near the tool substrate. In order to further improve the uniformity of the temperature field and deposit diamond coatings with uniform thickness, a novel hot filament chemical vapor deposition (HFCVD) device with separated worktables and plates for mass production of diamond-coated milling tools is proposed. First, the simulation models of previous device with integrated worktable versus new device with separated worktables are established using finite volume method. The simulation results shows that the temperature distribution is more uniform in the device with separated worktables. Second, temperature measurement experiments are conducted, which prove the correctness of simulation model. Subsequently, experiments involving the deposition of diamond coatings on milling tools are conducted using two kinds of worktables, utilizing the same parameters as in the simulation. Finally, high-speed milling experiments are conducted to test the diamond-coated milling tools. According to the results of SEM, Raman and high-speed milling experiments, it can be concluded that the homogeneity of coating thickness and cutting performance of the milling tools produced by HFCVD device with separated worktables and plates are better.

Study on the Influence of Product Thermal Effect on Thermal Vacuum Test

Due to different applications, the size, shape and surface state of the power supply on spacecraft vary greatly, but they all need to experience a harsh environment, such as extreme vacuum, cold and hot alternation. Therefore, it is necessary to undergo the thermal vacuum test on the ground. During the thermal vacuum test, the aerospace power supply products with different surface states have different internal temperature rise effects due to their own emissivity and absorption during testing. The higher the temperature rise effect, the lower the product reliability. Therefore, in order to reduce the temperature rise effect of products in the process of thermal vacuum test, the temperature rise effect of products with different surface states or the same surface state can be reduced by using different shading measures in the thermal vacuum test of products is analysed and verified by experiments. The test results show that the product with bright surface has lower temperature rise effect than the product with blackened surface, which can reduce the maximum temperature difference, enhance the uniformity of temperature field and enhance the reliability of the product. In addition, using measures such as covering the product with aluminized film or overhanging it can reduce the surface temperature difference, with the overhanging shade being more effective.

Heat generation mechanisms during induction heating of cross-ply carbon fiber reinforced thermoplastic laminates

Induction welding is considered to be one of the most promising welding technologies for carbon fiber reinforced thermoplastic (CFRTP) composites. However, the uncertainty of heat generation mechanisms presents a challenge to regulating the temperature field uniformity. In this paper, a quantitative calculation method for the induction heating efficiency of various mechanisms was proposed for cross-ply CFRTP laminates. Combining electrical and thermal properties, the cross-ply CF/PEEK and CF/PPS induction heating experiments were designed to explore the quantity ratio of various heat generation mechanisms. The results show that the heat production at the junction is about 106-107 times that of fiber heating. The dielectric loss is dominant mechanism at the junction, and the proportions of heat generated by dielectric loss in CF/PEEK and CF/PPS laminates were 0.6688 and 0.8255, respectively. Furthermore, the temperature prediction model with various stacking sequences was established, showing a good agreement with the experimental temperatures.

Novel cellular coil design for improved temperature uniformity in inductive heating of carbon fibre composites

Electromagnetic induction has great potential for energy efficient manufacturing of polymer composites. Carbon fibre can be directly heated inductively, achieving rapid, localised, and volumetric heating. The main obstacle to wider adaption of induction in composites processing is the non-uniformity of temperature distribution in-plane and through thickness of composite laminates. This study puts forward a new cellular architecture of the coil and examines the feasibility of addressing the problem of field uniformity. The geometrical parameters of the coil were examined in concurrent modelling and experimental work, aiming at reducing the effect of field cancellation in neighbouring cells and maximising both the coil efficiency and the field uniformity. The paper demonstrates good potential of the new coil designed with significantly improved uniformity of temperature field compared to traditional commercially available coils. This result has been further optimised with parametric finite element analysis to reduce the standard deviation in surface temperature by a further 37%.

Numerical analysis on thermal-hydraulic performance of optimized microchannel heat sink with slant ribs and quatrefoil rib-elliptical groove complex structures

A novel microchannel heat sink (MCHS-SREGQR) arranged with the spoiler element structure of the slant rib-elliptical groove-quatrefoil rib is proposed to meet the heat dissipation demands of electronic devices with high heat flux. The strategies for heat transfer enhancement are as follows: Firstly, the elliptical grooves are periodically arranged in the sidewalls of the microchannel and the quatrefoil ribs are set one-to-one at the centre of the grooves. The two structures complement each other's strengths and weaknesses. Secondly, the slant ribs are symmetrically arranged along the centreline of the channel. The slant ribs tend to expand along the flow direction, and produce diversion, guiding and gathering effects on the fluid, thus enhancing flow efficiency of the fluid domain in all aspects. Lastly, a novel quatrefoil rib is put forward, with a special structural design that both effectively inhibits the flow dead regions around the corners of the rib and significantly increases fluid turbulence. Three-dimensional numerical simulations are used to evaluate the effects of slant rib relative position, slant rib relative transverse spacing, and overall rib relative height on pressure drop, heat transfer capacity, and temperature field uniformity of the microchannel. Furthermore, the hydrothermal performance of MCHS-SREGQR is analyzed in comparison with a traditional straight rectangular microchannel and six other microchannels arranged with similar spoiler elements. The results indicate that when the Reynolds number is 696, the temperature at the heat source surface of MCHS-SREGQR decreases by 52.3% and the thermal resistance decreases by 66.6%, while the Nusselt number increases by 131% and the temperature uniformity increases by 76.8%. In addition, the field coordination number Fc increases by 131% and the performance evaluation criterion PEC can be achieved as 1.179.

Surface integrity of drilling Ti-6Al-4V micro-holes using the ultrashort pulse laser with different three-dimensional paths planning

The improvement of aero-engine performance posed a challenge to the heat dissipation ability of blades, resulting in a substantial increase in the demand for micron-sized (≤1 mm) film cooling holes. In this paper, an improved three-dimensional path machining method for ultrashort pulse laser drilling of Ti-6Al-4V titanium alloy is studied. The influence of four representative paths that are contour offset path, broken line path, raster path and jagged path on hole quality is described and discussed in detail. By establishing a three-dimensional two-temperature model in cylindrical coordinates, the defocusing control of the machining process is carried out, and the temperature field distribution with different drilling paths is simulated and analyzed. Finally, the experimental study of drilling round holes with a diameter of 800 μm is carried out on the titanium alloy Ti-6Al-4V plate with a thickness of 1 mm, and the wear resistance of the workpieces is tested. The experimental results show that, compared with the other three paths, the temperature field uniformity of laser processing with the contour offset path is the best, the quality of the processed holes is significantly improved, the outlet roundness is increased by 26.54 %–36.59 %, the cone angle is reduced by 12.7° and the wear resistance is increased by >1.3 times. Moreover, there is no obvious recast layer and micro cracks on the pore wall, and dense nano oxide particles are produced on the surface. In summary, the contour offset path controlled by three-dimensional defocusing is an effective hole processing path, which provides the possibility for machining efficient and high-quality film cooling holes.

Research on the heating rate of induction heating CFRP and temperature field based on image entropy

The electromagnetic induction heating technology has the advantages of fast heating speed and cleanness, and can realize the rapid temperature curing of carbon fiber reinforced polymer (CFRP). In order to improve production efficiency and curing quality, a finite element model of induction heating CFRP was established, and the temperature field distribution and heating mechanism during induction heating of CFRP were analyzed. The correctness of the model and conclusion is verified by experiments. On this basis, the influence of current, diameter, frequency and distance on the heating rate is analyzed, and it is found that frequency has the greatest influence on the heating rate. In addition, the mathematical relationship between temperature field uniformity and entropy value is established, which provides a quantitative analysis method for the temperature field uniformity of induction heating CFRP. Through optimization analysis, it is obtained that for the CFRP mentioned in the article, the coil size is selected between 65 mm and 95 mm, and the spacing is between 3.5 mm and 6.5 mm, so that the temperature field has the best uniformity.

Mixing Characteristics and Flow Fields Optimization of Primary Air for Coal Mill

This paper mainly focuses on the problems of inaccurate measurement of the primary air flow rate in a coal-fired power plant. The feasibility of improving the uniformity of flow fields and temperature fields by installing double-layer arch cool air distributor and mixed flow matrix was analyzed by the method of numerical simulation. The results show that, the relative standard deviation of the wind speed measurement section of optimization model decreased from 18.7%~18.4% to 9%~9.1%, compared with the original model. Similarly, the relative standard deviation of temperature measurement section also decreased from 15%~14.6% to 1.3%~1.4%. The study suggests that this mixed flow fields equalization solution can effectively enhance the mixing of cool and hot primary air, and can improve the uniformity of the mixed air flow fields, thereby improving the accuracy and reliability of primary air measurement.

Effect of shell shape on the charging and discharging performance of a vertical latent heat thermal energy storage unit: An experimental study

In this paper, the effect of shell shape on vertical latent heat thermal energy storage (LHTES) unit is experimentally investigated to alleviate the heat transfer lagging region and enhance its charging and discharging performance. A cylindrical (CYL) and two conical (CON-I and CON-II) LHTES units are designed and fabricated, and they have the same heat transfer area and internal volume. Paraffin with a narrow range of phase change temperature and high enthalpy was selected as phase change material (PCM), and water is used as heat transfer fluid (HTF). The thermal behaviors of CYL, CON-I and CON-II such as evaluation of melting and solidification fronts, temperature response characteristics, heat transfer characteristics and energy and exergy conversion are comparatively studied. A correlation is developed to predict the entire melting and solidification time of different LHTES units under different HTF flow rates and temperatures. The results demonstrate that CON-I and CON-II can provide a better temperature field uniformity and enhance the heat transfer rate between HTF and PCM. When compared with CYL, the entire melting/solidification time is reduced by 16.95 %/8.07 % and 29.94 %/23.22 % for CON-I and CON-II, and the time-averaged heat transfer rate is increased by 20.69 %/23.61 % and 35.87 %/41.24 % for CON-I and CON-II during the melting/solidification processes. In addition, the developed correlation is able to well predict the entire melting and solidification time of PCM in the LHTES unit with a relative error of ±5 %.

Integrated design of solar concentrator and thermochemical reactor guided by optimal solar radiation distribution

The improvement of solar thermochemical reactor performance is crucial in solar energy utilization technology. This study presents an integrated design method for solar thermochemical concentrator-reactor to enhance performance and safety guided by the ideal optimized solar radiation distribution. The ideal solar radiation distribution in the reactor is obtained by gradient optimization algorithm and the enhancement mechanism is analyzed. To achieve the ideal distribution, a two-stage composite parabolic concentrator is added to the solar thermochemical concentrator-reactor as secondary concentrator and designed by genetic algorithm. The results show that the optimized energy distribution with limited solar input can enhance the energy conversion, thus improving the performance of the solar reactor and reducing the reaction temperature level. The reason is that the ideal optimized solar radiation distribution significantly improves the uniformity of temperature, concentration and reaction field, while strengthening the match between them. Furthermore, the reactor satisfies the optimal reaction temperature window of 940–1100 K based on the minimum Gibbs free energy well under the optimized distribution. The secondary concentrator design achieves almost identical reactor performance under ideal solar radiation distribution and can still maintain 4–8% performance enhancement and 20–30% maximum temperature reduction under different operating conditions.

A New Type of Air Conditioning System Based on Finned Ceiling Radiant Coupled with Independent Fresh Air and Its Thermal Comfort Experimental Study.

The traditional radiation air conditioning system has some problems, such as easy condensation, insufficient refrigeration capacity, complex structure, and control system. Therefore, this study proposes a new type of finned metal radiant plate with large heat flow per unit area, sufficient cooling capacity, and simplified heat exchange system, in order to realize large temperature difference between cooling and heating. The temperature field uniformity and thermal comfort test of a novel type of finned ceiling radiant panel and independent fresh air linked air conditioning system under summer cooling and winter heating circumstances are accomplished through artificially generated climate environments. The study's findings demonstrate that in the radiation and fresh air modes, the maximum interior temperature differential under cooling conditions does not rise over 2.1°C. The maximum temperature differential in the space at any one moment in the radiation and fresh air modes cannot be greater than 3°C when heating conditions are present. The fresh air's cooling and dehumidifying effects are clear. The dehumidification efficiency may reach 50%, and the moisture content ranges from 5.48 to 9.63 g/kg. With PMV ranging from −0.34 to 0.54, the enhanced air conditioning system in this research provides exceptionally good thermal comfort. Additionally, the finned radiant panel's installation area occupies just 14% of the ceiling, which is sufficient to fulfill the room's cooling and heating load needs as well as provide high thermal comfort and consistent indoor temperature. The theoretical investigation and practical implementation of the direct expansion radiant air conditioning system are both strongly supported by this research.

Effects of human tissue acoustic properties, abdominal wall shape, and respiratory motion on ultrasound-mediated hyperthermia for targeted drug delivery to pancreatic tumors

Background PanDox is a Phase-1 trial of chemotherapeutic drug delivery to pancreatic tumors using ultrasound-mediated hyperthermia to release doxorubicin from thermally sensitive liposomes. This report describes trial-related hyperthermia simulations featuring: (i) new ultrasonic properties of human pancreatic tissues, (ii) abdomen deflections imposed by a water balloon, and (iii) respiration-driven organ motion. Methods Pancreas heating simulations were carried out using three patient body models. Pancreas acoustic properties were varied between values found in the literature and those determined from our human tissue study. Acoustic beam distortion was assessed with and without balloon-induced abdomen deformation. Target heating was assessed for static, normal respiratory, and jet-ventilation-controlled pancreas motion. Results Human pancreatic tumor attenuation is 63% of the literature values, so that pancreas treatments require commensurately higher input intensity to achieve adequate hyperthermia. Abdominal wall deformation decreased the peak field pressure by as much as 3.5 dB and refracted the focal spot by as much as 4.5 mm. These effects were thermally counteracted by sidelobe power deposition, so the net impact on achieving mild hyperthermia was small. Respiratory motion during moving beam hyperthermia produced localized regions overheated by more than 8.0 °C above the 4.0 °C volumetric goal. The use of jet ventilation reduced this excess to 0.7 °C and yielded temperature field uniformity that was nearly identical to having no respiratory motion. Conclusion Realistic modeling of the ultrasonic propagation environment is critical to achieving adequate mild hyperthermia without the use of real time thermometry for targeted drug delivery in pancreatic cancer patients.

Non-Newtonian Fluid Flow Modeling in the Inertial Viscometer with a Computer Vision System

Purpose of research. Development of theoretical premises for the new inertial viscometer, as well as the development of an approximate model of the viscosity fluid flow using convolutional neural networks and laser speckle contrast imaging data.Methods. The study consists of two parts. The first is devoted to a theoretical study of viscosity fluid flow in the toroidal channel of еру new inertial viscometer. The mathematical model of the flow includes the dimensionless equations of Navier-Stokes and convective heat conduction, the analysis of which made it possible to estimate the conditions for the uniformity of pressure and temperature fields. The numerical solution of the simplified Navier-Stokes equation was obtained by the control volume method. The computational experiment made it possible to identify additional operating conditions for the viscometer. The second part of the research is aimed at solving the problem of predicting the values of the shear strain rate on the tour surface and the flow rate. The approximate flow model is based on an ensemble of convolutional neural networks trained on data from laser speckle-contrast visualization of a fluid flow in a transparent tube.Results. The recommendations on the operating parameters of the inertial viscometer for the studied types of liquids in a given viscosity range are obtained. An approximate model has been developed in the form of an ensemble of deep neural networks, which makes it possible to determine the volumetric flow rate and the shear strain rate on the flow surface based on fluid flow images.Conclusion. The approximate Navier-Stokes equation obtained as a result of theoretical analysis for the flow of a viscous fluid in a toroidal channel can be used to numerical determination the kinematic viscosity. So, the necessary flow characteristics, such as volumetric flow rate and shear strain rate on the flow surface, can be found using the developed and pretrained convolutional neural network based on laser speck contrast imaging data. The test fluid can be any non-Newtonian fluid capable of reflecting coherent radiation. In particular, it can be physiological fluids, including blood.

Design and optimization of coil structure based on the uniformity of core temperature field

Design and optimization of coil structure based on the uniformity of core temperature field

Simulation and experimental study of uniformity of temperature field of electrically heated water

With the aim of investigating the non-uniformity of the temperature field of electrically heated water in a horizontal stationary circular tube, we numerically simulated the axial and radial temperature fields in a horizontal circular tube using the Fluent CFD package. We then designed a sectioned grouping heating scheme based on a two-position controller for experimental verification. The results show that the axial temperature in the tube is non-uniform if the tube is not placed horizontally. In the heating stage, uniform heating of the entire tube surface leads to significant vertical temperature stratification, with higher temperature in the upper part and lower temperature in the lower part of the circular tube. However, heating only the lower half of the tube's surface can reduce the temperature difference between the upper and lower layers from more than to less than, effectively improving the uniformity of the temperature field. During steady-state operation, due to the limitations of the two-position controller algorithm, the radial temperature deviation rises to a maximum of for the sectioned grouping heating mode. Compared with the whole-tube uniform heating mode, the grouping heating mode, especially the four-group heating mode, has obvious advantages with regard to the time to reach steady-state and the uniformity of the steady-state temperature field. This paper provides a reference for the design of heating schemes for horizontal isobaric closed circular tubes with high precision, minimal overshoot and good temperature field uniformity.

A numerical study of optimizing the well spacing and heating power for in situ thermal remediation of organic-contaminated soil

The thermal conductive heating (TCH) technology has been widely applied to remediate fields contaminated by organic compounds in recent years, because of its broad applicability, high treatment effectiveness, and less sensitivity to geological heterogeneity of treated sites. However, the high cost of thermal energy of TCH technology creates a need for optimal operation including the selection of number of heating wells and the power of each heating well. In order to investigate the relationship between site characteristics and operating conditions to realize uniform underground heating and to lower energy consumption during the process of TCH, numerical simulations were performed using COMSOL Multiphysics based on a coupled water-vapor-heat transport model without considering the organic pollutants. The numerical results were first validated by comparing with the experimental data obtained with a single heating tube from field tests. The effects of well spacing, water content, soil type as well as the heating power were discussed, and two measures for temperature uniformity and the degree of overheating were proposed. The results showed that low-power uniform heating can improve the uniformity of temperature field and reduce the degrees of overheating. For the sites with various water contents, different well spacings should be adopted to improve the efficiency of TCH. For a clay field, it is more suitable to use low-power heating strategy, whereas for other soil types, the well spacing can be increased appropriately with respect to the heating power. These results can serve as guidelines for heating well arrangement towards energy-efficient TCH applications.

Experimental investigation of bubble group and temperature distribution uniformity in the direct contact boiling heat transfer process

In the present study, a new method is proposed to measure the uniformity of temperature distribution and the phase distribution in direct contact boiling heat transfer. The proposed method is applied to explore the relationship between uniformity of bubble distribution and temperature distribution. Based on the uniformity theory, the relationship between temperature distribution uniformity, temperature field uniformity, two-phase mixing uniformity and volumetric heat transfer coefficient is explored. Then the uniformity of temperature distribution is obtained through thermal imaging under specific conditions. The obtained results show that the actual temperature distribution uniformity and the correlation coefficient of the uniformity through the gray value are higher than 99%. Moreover, the obtained relationship between bubble group distribution and temperature distribution reveals the essence of the uniformity of bubble group distribution in improving heat transfer. It is concluded that the temperature non-uniformity mainly originates from improper mixing of different streams with different temperatures when entering the heat exchanger, which reduces the thermal performance of a heat transfer process. This non-uniformity has a strong correlation with the flow pattern. The main objective of the present study is to provide a new method to evaluate bubble group distribution and temperature distribution in boiling heat transfer.