Air-cooled Condition Research Articles

Thermal Fault-Tolerant Asymmetric Dual-Winding Motors in Integrated Electric Braking System for Autonomous Vehicles

A conventional dual-winding (DW) motor has two internal windings consisting of a master part and a slave part, each connected to a different electronic control unit (ECU) to realize a redundant system. However, existing DW motors have a problem related to heat generation in both the healthy mode and the faulty mode of the motor operation. In the healthy mode, unexpected overloads can cause both windings to burn out simultaneously due to equal heat distribution. If the current sensor fails to measure correctly, the motor may exceed the designed current density of 4.7 [Arms/mm2] under air-cooling conditions, further increasing burnout risk. External factors such as excessive load cycles or extreme heat conditions can further exacerbate this issue. In the faulty mode, the motor requires double the current to generate maximum torque, leading to rapid temperature increases and a high risk of overheating. To address these challenges, this paper proposes the design of a thermal fault-tolerant asymmetric dual-winding (ADW) motor, which improves heat management in both healthy and faulty modes for autonomous vehicles. A lumped-parameter thermal network (LPTN) with a piecewise stator-housing model (PSMs) was employed to evaluate the coil temperature during faulty operation. An optimal design approach, incorporating kriging modeling, Design of Experiments (DOE), and a genetic algorithm (GA), was also utilized. The results confirm that the proposed ADW motor design effectively reduces the risk of simultaneous burnout in the healthy mode and overheating in the faulty mode, offering a robust solution for autonomous vehicle applications.

Effects of Cooling Media on Microstructure and Mechanical Properties in Friction Stir Welded SA516 Gr.70 Cryogenic Steel Joints.

SA516 Gr.70 steels were welded by friction stir welding (FSW) under various media of air, water, and water + CO2 cooling, and the effect of the cooling media on the microstructure and mechanical properties of joints was systematically analyzed. The nugget zone (NZ) under the air-cooling condition contained coarse bainite + martensite. Martensite was obtained by decreasing the cooling media temperature. Furthermore, tensile fracturing of the joints occurred in the basal metal (BM), and the ultimate tensile strength of the joints under various cooling media was similar to that of the BM. However, with decreasing cooling media temperature, the total elongation of the joints noticeably increased. Good strength (545 MPa) and elongation (16.8%) were obtained in the joints under the water + CO2 cooling condition since the fine martensite microstructure enhanced the plastic deformation capacity of the joints. In addition, in the NZ under water + CO2 cooling condition, good toughness of 110 J/cm2 was obtained due to a high fraction of high-angle boundaries and fine martensite.

The effect of elevated temperature on the performance of pozzolanic cement mortar

The current study focuses on the mechanical behavior of fly ash (FA) and wood ash (WA) as cement replacements at increased temperatures. Mortars containing 5, 10, 15, and 20% FA and WA as cement replacement were made and then exposed to temperatures of 200 ℃, 400 ℃, 600 ℃, and 800 ℃, with chosen samples being air-cooled or water-cooled. Curing times for the specimens were 28, 56, 150, and 365 days, respectively. For each age, compressive and tensile strength tests, weight loss at increased temperatures, and scanning electron microscopic examinations were performed. The control sample and FA at 10% replacement without temperature exposure showed a maximum compressive strength of 18 MPa and 1.4 MPa tensile strength at 28 days. Significant moisture was lost at high temperatures, decreasing strength performance. The control sample had a compressive strength of 23.3 MPa after 28 days of exposure to high temperatures under 600 ℃ air-cooled conditions. FA had the maximum value of 18.30 MPa at 15% replacement for 365 days air-cooled at 200 ℃, while WA had the highest strength of 16.40 MPa observed at 200 ℃ for 365 days. The cooling method had a considerable effect on the strength performance, with air-cooled being the better alternative. The study’s findings demonstrate the potential of FA and WA as environmentally friendly cement substitutes that can improve mortars’ durability and heat resistance at elevated temperature. This has significant implications for the building sector, particularly in regions prone to high thermal stress. It encourages the use of environmentally friendly materials without sacrificing structural integrity.

An electrical analogy model for performance evaluation of natural air-cooled TEG modules considering nonlinear effect of heat convection

With the outstanding merits of the simple principle and low computational cost, the electrical analogy model of thermoelectric generator (TEG) modules plays an important role in evaluating the performance of thermoelectric energy harvesting systems. However, owing to the simplification of the heat dissipation structure and difficulty in determining the heat dissipation parameters, it is difficult to accurately describe the nonlinear influence of thermal convection on the heat dissipation performance of the TEG module under natural air-cooled conditions, thereby reducing the estimation accuracy of the module temperature and output. A new nonlinear electrical analogy model to evaluate the performance of natural air-cooled TEG modules was proposed in this study. The proposed model more accurately describes the nonlinear influence of thermal convection on the thermal dynamic characteristics of the TEG module by introducing a heat transfer branch between the cold and hot side surfaces of the TEG module and the environment. A parameter extraction method based on multi-objective optimization and the non-dominated sorting genetic algorithm II (NSGA-II) was proposed to overcome the problem of the heat dissipation parameters of natural air-cooled TEG modules. The experimental results show that under natural convection conditions, the maximum estimation errors of the temperature and output voltage evaluated by the proposed model and parameter identification method are less than 6.18 % and 9.14 %, respectively. Under forced convection, the maximum estimation errors of the temperature and output voltage were less than 7.36 % and 8.71 %, respectively. The above estimation errors are significantly lower than the traditional model.

Green iron recovery through hydrogen-based mineral phase transformation using ultrafast air-cooling for heat recycling: A pilot-scale investigation

The utilization of ultrafast air-cooling has been proposed to reduce energy consumption in hydrogen-based mineral phase transformation (HMPT) technology for more sustainable iron recovery. Optimal conditions, including a grinding fineness of −74 μm accounting for 90 wt%, a reducing gas concentration of 20 vol%, a roasting temperature of 540 °C, and an air-cooling temperature of 300 °C, yielded an iron concentrate with a TFe grade of 59.29 wt% and a recovery of 89.40 wt%. The beneficiation indexes obtained by ultrafast air-cooling were comparable to those of the N2-cooling method. The reaction mechanisms were comprehensively studied to optimize the process, which revealed controlled oxidation of artificial magnetite to maghemite and hematite under ultrafast air-cooling conditions. The heat released during oxidation was recycled, leading to reduced energy consumption. Furthermore, ultrafast air-cooling increased particle porosity and cracks, thereby reducing subsequent grinding energy requirements. This research advances carbon reduction efforts in the steel industry, facilitating the transition to carbon neutrality.

Simulation research on thermal management system of battery module with fin heat dissipation structure

The LiFePO4 battery module will generate a lot of heat in its working process. A method of combination air-cooling and liquid cooling can dissipate this heat, so that to keep optimal operating temperature range for battery module. However, designing a combination that can maximize the heat dissipation effect remains a challenging task due to the involvement of numerous parameters. Finally, an optimal solution is proposed based on the orthogonal optimization design approach, including the fin length, coolant mass flow rates, coolant temperature. The simulation results indicate that the average temperature difference of the cell was reduced by 14.03 % and the temperature difference of the cooling channel was reduced by 46.41 %. Besides, the cell temperature was further controlled by optimizing the air-cooling conditions. The results showed that when the air-cooling maintained the average temperature difference of the cell less than 5 °C, then the temperature difference of the cooling channel was only 1.084 °C. This scheme provides a reference for the optimization of large-capacity battery module temperature.

Thermomechanical Processing of V-N Structural Plate Steels in Low Temperature Austenite

Austenite restoration during thermomechanical (TM) rolling of typical vanadium-microalloyed structural steels was studied to optimize strength in the as-rolled and air-cooled condition. Multi-pass plate rolling simulations were performed on V-N microalloyed and CMn steels to compare recrystallisation behaviour in various temperature regions. Included were a conventional schedule ending at high temperature and two TM schedules with mill exit temperatures in the intermediate and low austenite regions. Increasing delay periods after roughing enhance the suppression of recrystallisation after the start of finishing thereby increasing both nucleation site density and nucleation rate for ferrite formation and refinement in grain size. Good agreement was found between microstructures after industrial TM rolling and those obtained from laboratory simulations. Although precipitation of vanadium carbonitrides is an effective strengthening mechanism, appreciable gains in yield strength due to grain refinement can be achieved by rolling in the lower austenite region. Low nitrogen contents in V steels produce coarser final ferrite grain sizes and lower strengths probably due to a larger precipitate size. V-N steels display similar flow behaviour to CMn grades down to approximately 825°C at low to intermediate strain rates but may experience alternate regions of work hardening and dynamic softening at lower temperatures in austenite.

Effect of cooling medium on the κ carbide precipitation behavior, microstructure and impact properties of FeMnAlC low-density steel

The effect of four different cooling mediums, namely ice brine, water, oil, and air on the κ carbide precipitation behavior, microstructure, and impact properties of FeMnAlC low-density steel is thoroughly investigated by using OM (Optical Microscope), SEM (Scanning Electron Microscope), TEM (Transmission Electron Microscope), XRD (X-Ray Diffraction), VSM (Vibrating Sample Magnetometer), Rockwell hardness tester and in conjunction with low-temperature impact experiments. The results indicate that after cooling with different mediums, the austenite structure exhibits a mixed crystalline phenomenon and has a significant presence of twins. The average grain size of austenite increases as the cooling rate decreases, with the largest size observed in air-cooled conditions. Concurrently, the volume fraction and size of intragranular κ carbides gradually increase with a decreasing cooling rate. This phenomenon contributes to an increase in Rockwell hardness, with the highest value recorded in the air-cooled state at 36.8 HRC. Furthermore, the impact toughness initially increases and then decreases as the cooling rate decreases. Notably, water cooling demonstrates the highest impact energy at 68 J. The formation of intergranular κ carbides in oil and air-cooled conditions is identified as the primary reason for the decline in impact toughness.

Enhancing sustainable valorization: Harmless synergistic melting treatment for high-value vitreous products from MSWI fly ash and electrolytic manganese residue

The waste-to-energy and manganese industries face significant ecological challenges due to two major risk sources: municipal solid waste incineration (MSWI) fly ash and electrolytic manganese residue (EMR), especially, the MSWI fly is classified as hazardous waste. High temperature melting is a promising method for harmless disposal of solid wastes. However, it has yet to be industrialized due to the high costs and energy consumption. This study proposes using EMR as an additive to co-melt with MSWI fly ash, aiming to develop a method that minimizes energy consumption while producing high value-added products. To this end, the phase evolution and phase-change cooling characteristics during the co-melting process of MSWI fly ash and EMR were experimentally investigated. XRD and SEM analyses revealed that pure vitreous slag can be obtained when mixtures are heated to 1500 °C for 120 min with ≥40 wt% EMR addition under natural air-cooling conditions. Additionally, to produce vitreous slag by air-cooling and increase MSWI fly ash treatment capacity, the molten mixture with 30 wt% EMR addition was adopted in the directional solidification experiments to establish a predictive model relating the average cooling rate to the glass content. The findings ultimately contribute to the advancement of melting-based industrial applications.

Effect of low-temperature hot rolling on the microstructure and mechanical properties of air-cooling medium manganese martensitic wear-resistant steel

In this paper, the low-temperature hot rolling was conducted on air-cooled medium manganese martensitic steel, utilizing a finishing rolling temperature (FRT) that was significantly lower than the conventional used temperature. The effect of FRT on the microstructure, mechanical properties and wear resistance was systematically investigated. The results revealed that the pancaked austenite grain formed after low-temperature hot rolling could still be completely transformed into martensite structure under air-cooled condition. The lower FRT significantly refined the martensite multi-level microstructures, increased the grain boundaries density and dislocations density, and promoted the nano-scaled V(C, N) precipitation. These resulted in enhanced refinement strengthening, dislocation strengthening and precipitation strengthening. Compared to the FRT-900 sample, the FRT-700 sample exhibited increased yield strength, tensile strength, and Brinell hardness, with values rising from 973 MPa, 1526 MPa, and 454 HB to 1174 MPa, 1701 MPa, and 482 HB, respectively. In addition, the refined microstructure effectively increased the dimple region in the fractography of impact samples, preventing the propagation of crack and thereby enhancing the impact absorbing energy. Consequently, the impact absorbed energy at −40 °C of experimental steel was increased from 28 J to 38 J, while also increasing strength. Moreover, the low-temperature hot rolling effectively increased the surface hardness of the experimental steel, inhibited abrasive embedding and improved impact wear resistance. The mass loss rates of low-temperature hot rolling samples were 0.052 mg/s and 0.063 mg/s under the impact energy of 1 J and 2.5 J, respectively.

The effect of temperature and sulphate attack on ternary blended self-compacting concrete

In this paper, self-compacting concrete was prepared by modifying cement content of the conventional concrete mix. The substantial cementitious materials like fly ash, metakaolin and ground granulated blast furnace slag are used to partially replace the cement. The substitution amount of fly ash, metakaolin are 15%, 5% (fixed) and GGBS is used by 20%, 30% and 40% of cement to get three various SCC mixes. For both M25 and M40 grade concrete followed the same pattern and produced S25A, S25B, S25C, S40A, S40B and S40C. The mechanical properties of concrete like flexural and split tensile strength along with compressive strength at the age of 7, 14, and 28 days for all blends mixes. Specimens were immersed into 5% sodium Sulphate and 5% magnesium Sulphate solutions, and compressive strength was conducted on the specimens at 3, 7 and 28 days. Based on the mechanical properties and sulphate resistance of all the mixes S25C and S40C are selected for the temperature effect on mortar mix related to that concrete. The mortar specimens of S25C and S40C were tested for various elevated temperatures such as 250 °C, 450 °C to 650 °C for a period of 1 h. After that, the specimens were cooled in quenched and air-cooled condition.

Temperature Modeling of AZ31B Alloy Plate during open-Roller Conveying Process Considering Air-Cooling Characteristics

In the process of open-roller conveying, magnesium alloy plates easily produce temperature drops and uneven temperatures. Ignoring the heat dissipation caused by the contact between the plate and the roller table, the process can be described as a process of air cooling. The present study aimed to investigate the temperature distribution and evolution of a magnesium alloy plate during the process. The air-cooling process of the AZ31B magnesium alloy plate was investigated and analyzed in detail under different initial temperatures and plate thicknesses, with a specific focus on the temperature distribution along both the width and thickness directions. The results show that the temperature-difference curves between the end face and the center under different air-cooling conditions appeared to have four stages: rapid increase, slow increase, basic stable and slow decline. To facilitate the establishment of the temperature model, the whole air-cooling process was approximately divided into two independent one-dimensional heat-conduction processes in the thickness direction and the width direction. Subsequently, one-dimensional steady-state heat-conduction models were developed in various directions, based on the fundamental principles of heat transfer and assuming that the adjacent temperature-drop layer satisfied the quadratic function distribution. Through the superposition of cooling with time in two directions, the temperature evolution at different positions in the process of air cooling can be solved accurately.

Experimental investigation of a sustainable reinforced cantilever concrete slab exposed to different intensity of temperatures

Recently, several scientists have paid special attention to how high temperatures alter the chemical and physical features of reinforced concrete structural members such as slabs. Cantilever concrete slabs, the impact of cooling regimes, the influence of the crack created during heating, and the residual strength of concrete slabs subjected to extreme temperatures were very limitedly investigated in the reviewed literature. Therefore, this research investigated the behavior of cantilever concrete slabs subjected to elevated temperatures and cooling regimes. Two different slab thicknesses (100 mm and 150 mm), various intensity of temperature (200 °C, 300 °C, 400 °C and 500 °C) and two different cooling conditions (Air and Quench cooling) were examined. The observations made during the thermal loadings were the moisture movement, deformation, crack patterns, and temperature on the slab's exposed (bottom) and unexposed surface (top). The results indicated that the magnitude of temperature influences all the tested specimens. In the quench-cooled condition, the development of cracks was increased in the non-exposed slab surface when heated at 300 °C, 400 °C and 500 °C. The severity of the exposed temperature and cooling regimes also affected the concrete slab's irreversible loss of flexural stiffness. The flexural stiffness reduction of the 100 mm thick slab varied from 1.68% to 35.52% for a temperature range of 200 °C–500 °C under air-cooled conditions, while for the quench-cooled specimens, the stiffness reduction varied between 0.88% and 45.92% for the same temperature range. On the other hand, increasing the slab thickness from 100 to 150 mm decreased the stiffness reduction, where the stiffness reduced by 1.02%–24.61% and 0.28%–32.17% for the cases of air and water coolings, respectively.

Heat transfer process analysis and performance research of micro heat pipe array applied for the thermal management of proton exchange membrane fuel cells

• A new PEMFC thermal management method based on micro heat pipe array is proposed. • Micro heat pipe array has fast thermal response and good temperature uniformity. • Micro heat pipe array can enhance the heat dissipation capacity of PEMFC. Effective thermal management is critical for the safe and efficient operation of proton exchange membrane fuel cells (PEMFC). The small temperature difference between the stack and the environment brings greater challenges to the cooling system. This study proposes the integration of micro heat pipe arrays (MHPA) into bipolar plates for thermal management of small-power air-cooled PEMFC. The heat transfer performance of 2 mm MHPA under air-cooled conditions is experimentally studied, and a comparative study is conducted on the actual application of air-cooled PEMFC. The results show that the MHPA can reach a steady state within 600∼900 s when the heating power is changed. The minimum thermal resistance of the MHPA is 0.53 K/W, the uniform temperature distribution in the evaporation zone is very uniform within 2 K, showing a small heat transfer thermal resistance and good temperature uniformity performance. When the maximum temperature inside the stack does not exceed 65 ℃, the maximum output power of the MHPA-PEMFC is 25.66% higher than that of the traditional air-cooled PEMFC, and the maximum temperature difference inside the stack is reduced by 50.1%. The results of this study provide a theoretical basis for the application potential of MHPA in PEMFC thermal management.

Effects of cooling conditions and chitosan coating on the properties of porous calcium phosphate granules produced from hard clam shells

• Clam shell was used to synthesize CaP granules by gas foaming technique. • Samples under furnace cooling condition were biphasic CaP granules (HA/β-TCP). • Samples under air cooling condition were triphasic CaP granules (HA/β-TCP/α-TCP). • Samples air-cooled and chitosan-coated had maximum compressive strength. The main inorganic components of clam shells are calcium carbonate and trace elements of magnesium, strontium, and zinc. Clam shells can be used as a calcium source to synthesize calcium phosphates, and these trace elements promote the growth of bone tissue and improve the performance of bioceramics. In this study, hydroxyapatite (HA) powders were synthesized from clam shells, and porous calcium phosphate granules were prepared through the gas foaming technique. In addition, the effects of a chitosan coating and cooling conditions on the strength of the porous granules were investigated. The results indicated that the samples produced under the furnace cooling condition were biphasic hydroxyapatite/β-tricalcium phosphate granules (HA/β-TCP), whereas the samples produced under the air-cooling condition were triphasic hydroxyapatite/β-tricalcium phosphate/α-tricalcium phosphate granules (HA/β-TCP/α-TCP). The compressive strength of the porous granules prepared through air cooling was 79% higher than that of the granules produced through furnace cooling. The compressive strength of the air-cooled sample after the subsequent application of the chitosan coating further increased by 21%. A degradability test revealed that the weight loss rate of the air-cooled samples was greater than that of the furnace-cooled samples, which was due to the presence of high-solubility α-TCP in the air-cooled samples.

Thermal study of the natural air cooling using roll bond flat heat pipe as plate fin under multi-heat source condition

Conventional radiators with the solid metal fins are difficult to meet the 5G base stations with greatly increased cooling requirements. Therefore, a novel phase-change device, named roll-bond flat heat pipe (RBFHP), has emerged as an alternative fin with the merits of easy to fabricate into large surface but thin, low-cost, and high heat transfer coefficient. In this study, the RBFHPs were tested with multi-heat source under natural air-cooling condition, to reflect the practical application scenario. And the thermal performances were investigated and optimized in terms of the heat source distribution, filling ratio, inclination angle, and power distribution mode. The results show the thermal performance is highly relevant to the relative position between the liquid-vapor interface and the higher load heat source. It is improper for the RBFHP to function when the latter is above the former, on the contrary, when the latter is beneath the former, the phase change cycling in the RBFHP can be prompted and sustainable. The final optimized RBFHP was working in 30° inclination angle with 20% filling ratio, and the largest heat source was the bottom one among the 3 lower distributed heat sources. And its total thermal resistance and temperature rise can be reduced by 15.3% and 10 °C respectively, compared to an evenly heated aluminium plate at 48 W total heat load.

Research on high efficiency deposition method of titanium alloy based on double-hot-wire arc additive manufacturing and heat treatment

Wire arc additive manufacturing (WAAM) is a promising additive manufacturing technique with growing acceptance in fabricating large size components. In this paper, titanium alloy Ti-6.5Al-2Zr-1Mo-1V (TA15) for double-hot-wire arc additive manufacturing (DHWAAM) was firstly investigated and analyzed in deposition state and heat treatment, mainly including mechanical properties and microstructure evolution. The heat input modes of the two processes are different, the deposition efficiency is doubled and the material processing efficiency is greatly accelerated but the change of mechanical properties is not obvious. The microstructure and mechanical properties were analyzed. Due to the decrease of heat input, the grains of DHWAAM are mainly equiaxed grains, while the grains of WAAM are coarse columnar grains. In addition, in the perpendicular direction to columnar grains growth, tensile specimens have better mechanical properties. Sample with fine αP in the microstructure has better elongation. In the heat treatment, it is found that the heat treatment temperature has a great influence on the mechanical properties under air-cooling conditions. The α in the stress-relieved state is finer than the double-annealed state, which shows better yield strength.

Microstructures, Simulations and Solidification Behaviors of A356 Semisolid Aluminium Alloy Prepared by Stirring Integrated Transfer-Heat Technology under Different Cooling Mediums

Based on the theory of grain refinement, the microstructures and simulations of A356 semi-solid aluminum alloy under different cooling mediums were studied. The experiment and simulation results show that water cooling is better than any other cooling mediums. Combined with the simulation of stirring and heat dissipation in SIT device, the changes of temperature field and solid fraction of the melt were studied to help understand the nucleation, growth and solidification behavior under the SIT process. During the process, the temperature field of the melt becomes relatively uniform from a larger temperature gradient and the continuous cooling speed is increased. The results also indicate that compared with traditional casting, the microstructure cooled by water are composed of refined rosiness and nearly spherical particles. With the increase of cooling degree, the average grain size decreased from 206μm to 186μm. The solid fraction increases from 4.4% to 12.2% under the no-cooling and air-cooling conditions, while it is more uniform, increasing from 5.1% to 8.8% due to the water cooling.

The effect of microstructure evolution on the ratchetting-fatigue interaction of carbide-free bainite rail steels under different heat-treatment conditions

Low-cycle fatigue experiments emphasizing the ratchetting are performed on the carbide-free bainitic (CFB) rail steel under different heat-treatment conditions. The effects of microstructure and retained austenite (RA) on the ratchetting-fatigue interaction are investigated through macroscopic and microscopic characterizations. The results indicate that the CFB rail steel exhibits a non-saturated and strain amplitude-dependent cyclic softening feature and shows different ratchetting behaviors and failure modes at various stress levels. Ratchetting promotes the development of stable dislocation substructure and the transformation of blocky RA. The fatigue resistance of 1380 grade CFB steel under the online controlled cooling conditions is better than that of 1280 grade CFB steel under the air-cooling condition.

Structure Parameters Optimization of the Rain Cover and Ventilation Duct of Dry Air Core Reactor under the Forced Air Cooling Condition

In this paper, the three‐dimensional fluid field‐temperature field coupled model of air core reactor is established, the detailed temperature field distributions of reactor can be obtained, and the reason about the temperature rise of reactor is significant increased when adding the rain cover is given by analyzing the flow velocity of fluid in the air ducts. Considering the natural air cooling no longer meets the temperature rise requirement of the reactor, the forced air cooling is performed by installing ventilation duct and fan at the bottom of the reactor, combined with the finite element method and central composite experimental design method (CCD), the influence of structure parameters of rain cover and ventilation duct on the temperature rise of reactor are analyzed, meanwhile, the response surface model is established, which reflects the relationship between the temperature of reactor and the structure parameter of rain cover and ventilation duct, and the optimal design parameters can be obtained based on the quantum genetic algorithm, the maximum temperature of the reactor is only 59.3°C, the difference between the prediction of response surface and simulation result is only 0.1°C, and the correctness of the optimization method is validated, which provides an important guiding significance for the safe and stable operation of reactor in the system. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.