Thermal Uniformity Research Articles

Experimental Study on the Comparison between Network Microstructure Titanium Matrix Composites and Ti6Al4V on EDM Milling.

Network microstructure titanium matrix composites (NMTMCs), featuring Ti6Al4V as the matrix and network-distributed TiB whiskers (TiBw) as reinforcement, exhibit remarkable potential for diverse applications due to their superior physical properties. Due to the difficulty in machining titanium matrix composites, electrical discharge machining (EDM) stands as one of the preferred machining techniques for NMTMCs. Nevertheless, the compromised surface quality and the recast layer significantly impact the performance of the workpiece machined by EDM. Therefore, for the purpose of enhancing the surface quality and restraining the defects of NMTMCs, this study conducted comparative EDM milling experiments between NMTMCs and Ti6Al4V to analyze the effects of discharge capacitance, charging current, and pulse interval on the surface roughness, recast layer thickness, recast layer uniformity, and surface microcrack density of both materials. The results indicated that machining energy significantly influences workpiece surface quality. Furthermore, comparative experiments exploring the influence of network reinforcement on EDM milling revealed that NMTMCs have a higher melting point, leading to an accumulation phenomenon in low-energy machining where the reinforcement could not be completely removed. The residual reinforcement in the recasting layer had an adsorption effect on molten metal affecting the thermal conductivity and uniformity within the recasting layer. Finally, specific guidelines are put forward for optimizing the material's surface roughness, recast layer thickness, and uniformity, along with minimizing microcrack density, which attain a processing effect that features a roughness of Ra 0.9 μm, an average recast layer thickness of 6 μm with a range of 8 μm, and a surface microcrack density of 0.08 μm-1.

Design and Optimization of Accumulator Pack

For an electric scooter, a lithium-ion battery with a Acro Butyl-nitrate (ABS) temperature management system was developed. Without the use of active cooling components like a fan, a blower, or a pump used in air/liquid-cooling systems, passive thermal management systems employing ABS can regulate the temperature excursions and maintain temperature uniformity in Li-ion batteries. Therefore, this new type of thermal management system can provide the benefits of a small, light, and energy-efficient system. The simulation results for a Li-ion battery sub-module with twenty 18650 Li-ion cells encased in ABS and a melting point of 114 to 120 °C are displayed. There are many important advantages to using aluminium fins manufactured from 0.7mm thick aluminium sheet between the battery cells in an accumulator pack. The relevance of them is explained in the following ways: Accumulator packs, particularly those used in high-power applications like scooters, can produce large amount of heat when in use. The performance, longevity, and safety of battery cells are all significantly impacted by heat. Aluminium fins serve as heat sinks and enhance heat dissipation by boosting the amount of heat-transfer surface area. Heat can be effectively transferred from the cells to the fins thanks to the thin aluminium sheet. Temperature Control: Battery cell efficiency and longevity depend on maintaining their temperature within a favorable range. By releasing more heat, aluminium fins assist in controlling the temperature. The fins aid in preventing overheating and preserving a more constant operating temperature by efficiently draining heat from the cells. Thermal Uniformity: The accumulator pack's thermal uniformity is enhanced by the inclusion of aluminium fins between the battery cells. Variations in cell temperature can cause performance imbalances and lower pack efficiency because uneven heat distribution can cause temperature differences among the cells. The fins aid in the even distribution of heat throughout the cells, reducing temperature variations and fostering consistent performance. Reduced Hotspots: Hotspots are small, high-temperature regions inside a battery pack that can hasten degradation and pose safety issues. Aluminium fins aid in heat dissipation, which reduces the development of hotspots. The fins' increased surface area enables more effective heat transport, which lowers the possibility of localized temperature accumulation. Improved Safety: Effective heat dissipation with aluminium fins can aid in accumulator packs' increased safety. Battery cells may experience thermal runaway or other dangerous situations as a result of high temperatures. The risk of thermal incidents is decreased by maintaining lower cell temperatures, improving operational safety in general. It's crucial to remember that parameters like spacing, size, and overall pack should be taken into account while designing and using aluminium fins. Additionally, by lowering the amount of heat that is released into the environment, liquid cooled heatsinks can be utilised to lessen the environmental effect of electronic equipment. The following are some benefits of employing liquid-cooled heatsinks: ● more efficient at cooling than heatsinks that use air cooling ● can be used to enhance the functionality and dependability of electronic equipment ● can be used to lessen how harmful electrical devices are to the environment. The following are some drawbacks of employing liquid-cooled heatsinks: ● more expensive than heatsinks that are air-cooled. ● more difficult to install and keep up ● Tend to leak more frequently. Keywords — CFD, 18650,ABS ,ALUMINUM FINS ,DRIVE CYCLE MODELS,EQUIVALENT CIRCUIT MODEL.

Conjugate transient flow and thermal analysis of non-isothermal rubber curing process in autoclave system

Autoclave manufacturing under high pressure and elevated temperature was required to vulcanize the rubber compound applied in the aerospace industry. Nevertheless, few works have comprehensively explored the transient effect of flowing factors on curing efficiency, thermal uniformity, and exergy destruction in autoclave processing. In this study, the three-dimensional model and non-isothermal vulcanization of an autoclave with a built-in combustion chamber were solved by combining the finite volume method and the proposed mixed kinetic model, and exergy destruction was determined to estimate the energy consumption using a direct method. Variations in the Reynolds number (Re), gas pressure (P), temperature, rate of temperature change, and Prandtl number (Pr) were analyzed to improve the unstable thermo-vulcanization and reduce energy consumption in autoclave processing. The results demonstrate that increasing the inlet Re can significantly increase the curing rate while decreasing the temperature difference in the rubber area, and a reduction of 41.89 %−46.62 % for the complete vulcanization time is achieved by changing Re from 105 to 2 × 106; however, adjusting P and temperature has only a minor effect on the heat transfer under constant higher Re. Furthermore, changing the rate of temperature change and Pr is also advantageous for optimizing the curing process and reducing exergy destruction. A minimal non-dimensional exergy destruction rate arises for a given P, rate of temperature change, or Pr when the Re is raised. The knowledge gathered from this research could provide a theoretical foundation for reducing energy consumption and boosting productivity during autoclave curing.

Enhancing thermal management in cylindrical Li-ion battery through PCM integration with variable contact area

Cylindrical Li-ion batteries are widely embraced in various sectors, notably electric vehicles and renewable energy storage systems. An effective thermal management system is vital for their safe and dependable operation, enhancing both the performance and reliability of the system. This study employs a distinctive hybrid cooling strategy consisting of a phase change material (PCM) at the centre of the battery and liquid cooling at the surface of the cylindrical batteries. The contact area between the coolant and the battery’s surfaces varies to make sure same heat transfers from each battery. This approach is instrumental in maintaining thermal uniformity and regulating the maximum temperature. In the numerical analysis, we employed ANSYS Fluent 2022 R1 to create the computational model encompassing the Li-ion battery, PCM, and liquid cooling system. This arrangement utilized eight 18650Li-ion batteries, with each battery housing a 2 mm radius PCM rod at the centre of the batteries. A heat-conducting element (HCE) was introduced to facilitate contact between the battery and the coolant channel. Water was selected as the coolant, and the coolant channel cross-sectional area is 65 × 2 mm2. The relationship governing the variable contact area is determined by fixing the velocity and the first battery contact area. The variable contact geometry maintains thermal uniformity throughout the battery module, resulting in a 74% enhancement in thermal uniformity. Nevertheless, the integration of PCM inside the battery effectively prevents individual batteries from surpassing specified temperature limits. It yields a remarkable 36.64% enhancement in thermal uniformity compared to situations in which PCM is not present, albeit with a 3.75% capacity loss. Furthermore, the study investigates the effects of coolant flow rates and performs an extensive analysis of temperature variation and melting fraction.

Formation mechanism and improved remedy of thermal property of cold shut surface defects in Vortex Flow Meters: Numerical simulation and experimental verification in investment casting of 316 L stainless steel

The purpose of this study aims to investigate the leading causes of CS (Cold Shut) defects in VFM (Vortex Flow Meters) of intricate geometric configuration and propose improvement strategies to leverage the thermal property in the vicinity of thin-walled regions, such as insulation-enhanced uniformly distributed temperature via ceramic core embedment. First, penetrant testing reveals whether the defect is a penetrating-type defect. Second, several extensive material characterization techniques such as optical microscopy (OM), energy-dispersive X-ray spectroscopy (EDS) analysis, and charge-coupled device (CCD) were employed to provide deeper insights into the formation and morphology of defects. Third, numerical simulations and experimental verifications were utilized to further analyze the causes of CS defects in vortex flowmeters. Fourth, effective preventive measures were designed after identifying the causes of defects, which involved using ceramic cores to replace the shell at deep and thin-walled locations. A virtual thermo-dynamic sensor (VTDS) was used to analyze the temperature distribution in the area before and after the installation of ceramic cores. The results indicate that the temperature in the defect area increased by >40 degrees during the filling period from 2.5 s to 5 s. Additionally, adequate thermal uniformity was achieved through the high thermal conductivity of the ceramic material, thereby reducing the cooling rate and the coefficient of kinematic viscosity in that area, leading to improved fluidity of the molten iron. Ultimately, the occurrence rate of CS defects decreased from 42.6 % to 0 %.

Thermal Management for a Stadium Power Supply Container Using a Rack-Level Air Cooling Strategy

This study investigates the airflow and thermal management of a compact electric energy storage system by using computational fluid dynamic (CFD) simulation. A porous medium model for predicting the flow resistance performance of the battery modules in a battery cabinet is developed. By studying the influence of rack shapes, the effects of heat exchanger arrangements and other parameters on the airflow and battery thermal distribution are analyzed. When applying a larger bottom air channel, the inlet flow uniformity of each battery cabin in the cabinet increases by 5%. Meanwhile, temperature standard deviation decreases by 0.18 while raising the flow rate from 3 m/s to 8 m/s, indicating better temperature uniformity in the battery cabin. When the charge–discharge ratio reaches 0.5 C, the temperature deviation of the entire cabinet significantly increases, reaching 8 K. Furthermore, a rack-level thermal management scheme is proposed to effectively reduce the thermal deviation of the container electric energy storage system and improve the overall temperature uniformity. Results reveal that the rack-level thermal management of the wavy cabinet in the electric storage container can effectively improve the thermal uniformity of the distributed battery cabin, and the overall thermal deviation is controlled within 1.0 K.

Study of cooling experiment and simulation for edible oil storage

This paper proposes a refrigerant cooling method using an inner tube in a storage tank to improve the cooling performance and thermal uniformity during the storing of edible oil. With a prototype of an oil tank in Central Grain Reserve of Zhenjiang, the experimental oil tank was built in a scale of 50:1. Both natural and manual cooling experiments were carried out for the experimental tank. The manual cooling process involved two supplying modes for the refrigerant tube (top and bottom) and four different refrigerant temperatures (10 ℃, 12 ℃, 14 ℃, 16 ℃). The experimental results show that, compared with natural cooling, manual cooling can effectively reduce the temperature difference and thermal stratification between upper and lower layers. The temperature difference is 6.79 ℃, 1.93 ℃, and 3.67 ℃ for the natural cooling, manual top supplying, and manual bottom supplying mode, respectively. Furthermore, for the two manual modes, the cooling efficiency of bottom supplying is 21.4% higher than that of the top supplying, and the average oil temperature drops by 0.8–1 ℃. Based on experimental results, different working conditions (20, 40, and 60 ml/s) were simulated to determine the optimal flow rate for bottom supplying mode. The simulation results indicate that the low flow rate (20 ml/s) corresponds to the best thermal uniformity, and the maximum temperature has no obvious change under different flow rate conditions. Therefore, it is not necessary to increase the flow rate to improve cooling efficiency considering the rising energy consumption.

Numerical study and optimization of thermal efficiency for a pin fin heatsink with nanofluid flow by modifying heatsink geometry

This paper presents a numerical study on the thermal efficiency of a pin fin heatsink (HEK). The working fluid used is an alumina/water nanofluid, which enters the HEK in a laminar flow regime and exits from its surroundings. This study involves varying the distance between circular pin fins, their height, and their diameter. By altering these parameters, we determine the values of thermal resistance (THR) and temperature uniformity (Teta) on the HEK, along with the heat transfer coefficient (HTC). We further optimize the obtained results using artificial intelligence techniques to minimize the THR of the HEK, maximize the HTC, and achieve the best Teta on the HEK. This numerical investigation employs a two-phase approach to model nanofluid flow within the HEK. The optimization process yields predictions with an accuracy of less than 4%. The findings reveal that increasing the height of the pin fins reduces the HTC and the heat capacity of the HEK, while simultaneously improving the Teta on the HEK. Expanding the distance between pin fins enhances the HTC, decreases the THR of the HEK, and further improves the Teta on the HEK. Similarly, augmenting the diameter of the pin fins amplifies the HTC, reduces the THR, and enhances the Teta on the HEK.

Energy management of a concentrated photovoltaic−thermal unit utilizing nanofluid jet impingement in existence of thermoelectric module

To generate a concentrated photovoltaic–thermal (CPVT) unit system, linear Fresnel concentrators have been attached to a PV unit and a thermoelectric generator (TEG) has been combined in this work to boost productivity. In the presence of concentrators, the temperature of the silicon layer increases. While electrical output is enhanced for the CPVT unit, the non-uniform isotherms can decrease the lifetime of the panel, so confined jets of alumina–water nanofluid have been applied for cooling. To validate the numerical code, previous papers were examined and good accommodations were reported. Various values of the inlet temperature (T in) and velocity (V in) of jets have been analysed. The impacts of installing concentrators on overall performance and CO2 mitigation have been investigated. An increase in V in leads to an incremental increase in thermal performance of about 4.2% and thermal uniformity is enhanced by about 13.91%. The thermal power of the system is enhanced by about 2.19 times as a result of adding concentrators. Also, the PV power is enhanced by 86.22% in the presence of the reflectors. With the increase in T in, the thermal and electrical performance decrease by about 19.95% and 5.24%, respectively. Installing concentrators enhances the overall performance by about 6.55%. After 10 years, the amount of CO2 mitigation for the CPVT-TEG system reaches 148.28 ton.

Effect of truncated pin-fins on flow and heat transfer characteristics with impinging jets on a concave surface

The double-wall cooling system containing jet impingement and full-length pin-in cooling structures shows good performance in heat transfer enhancement and uniformity, which has-been used in the blade cooling design. However, the pressure loss induced by the full-length pin-fin is relatively high. It is very meaningful to get a cooling type which can balance the heat transfer performance of double-wall cooling and flow resistance, especially for the blade leading edge. In this study, numerical simulations have been carried out to study the influences of truncated pin-fins height and arrangement on heat transfer increment and flow behavior of jets impinging onto a concave double wall channel with varying truncated pin-fins arranged, considering the heat transfer enhancement potential and relatively weaken pressure loss penalty of truncated/broken pin-fin. Jets impingement on a smooth-concave surface is regarded as Baseline. Streamlines in two-dimensional sections in the channel and limiting streamlines near the target wall conjugated with flow characteristics figures are applied to better understand the flow structures in the channel. The local and averaged heat transfer performance is analyzed based on the flow discussions. The overall parameters, i.e., thermal performance, friction factor and pumping power, are also obtained. The results show that the introduction of relatively high truncated pin-fins located on the upper wall presents higher heat transfer enhancement and lower pressure loss comparing with the full-length case and truncated pin-fins located on pressure loss comparing with the full-length case and truncated pin-fins located on target wall cases. The truncated pin-fins placed on the upper surface with relative height of 0.75 reaches the highest overall thermal performance and uniformity in this work.

Analysis on temperature uniformity in methane-rich internal reforming solid oxide fuel cells (SOFCs)

Temperature uniformity is a critical parameter in solid oxide fuel cells (SOFCs) since it directly impacts thermal stress, material degradation and output performance. Effective thermal management typically aims to achieve a minimal temperature gradient, especially within a SOFC stack assembled by numerous single cells. In this study, numerical simulations of various boundary conditions and cell designs are performed to investigate thermal uniformity in methane-rich internal reforming SOFCs, which can be utilized as a guidance for design and operation in practical application. The results indicate that the fuel gas with a 5 % mole fraction of methane is more effective in enhancing thermal uniformity through reforming cooling effect at the electrolyte compared to only a 1 % mole fraction. It is strongly recommended in cell design to maintain the ratio of the cell's length to its width (Rcell) greater than or equal to 1.0 considering its better thermal uniformity. However, both increasing the ratio of channel width to rib width (Rc-r) and decreasing the ratio of channel height to channel width (RH-W) have been demonstrated to deteriorate temperature uniformity. Within this study, increasing the backpressure to 1.5 bar is found to result in a 16.7 % reduction in the maximum temperature difference across the electrolyte when compared to that at atmospheric pressure. It is also advisable to operate at the inlet temperature ranging from 973 K to 1023 K for a more uniform temperature distribution within the SOFC.

Heat transfer characteristics of liquid cooling system for lithium-ion battery pack

To improve the thermal uniformity of power battery packs for electric vehicles, three different cooling water cavities of battery packs are researched in this study: the series one-way flow corrugated flat tube cooling structure (Model 1), the series two-way flow corrugated flat tube cooling structure (Model 2), and the parallel sandwich cooling structure (Model 3). Based on the fluid-solid coupling method, this study analyzes the cooling performance of the three models, including thermal uniformity, heat dissipation, and pressure loss. At a high discharge rate, compared with the series cooling system, the parallel sandwich cooling system makes the average temperature and maximum temperature of the battery pack decrease by 26.2% and 26.9% respectively, and the battery pack temperature difference decreases by 62%, and the coolant pressure loss decreases by 95.8%. The results show that the Model 3 overcomes the temperature accumulation caused by the series flow of coolant and achieves a better level of thermal uniformity while improving the heat dissipation and pressure loss performance. The research provides scholars and industries with a reference for upgrading thermal management and improving the stability of the power battery pack for electric vehicles, which has both theoretical and practical significance.

Advancing heat management in proton-exchange membrane fuel cells through hybrid nano-composite phase change materials

Heat management challenges in proton-exchange membrane fuel cells (PEMFC) leads to performance degradation, particularly during operational fluctuations and vehicle downtime. This study examines the use of Nano-additive phase change materials (PCMs) as an innovative approach to thermal management in PEMFCs. It addresses a research gap, as PCMs' advantages in batteries and electronics are well-known, but their application in PEMFCs remained relatively unexplored. Hence, using the ChtMultiRegionFoam solver from OpenFOAM, two heat transfer aspects in PEMFCs are studied. The first examines PEMFC cooling under normal conditions, combining liquid cooling with a hybrid Nano-composite phase change material (HNCPCM). The results indicate the HNCPCM cools the PEMFC for 11 min before reaching saturation, after which liquid cooling starts. Moreover, with HNCPCM, the PEMFC's thermal efficiency and temperature uniformity enhance by 7.04 % and 39.76 %, respectively. Therefore, the HNCPCM contributes to cooling as the temperature and voltage fluctuate under real conditions. The second aspect evaluates PCM and insulation to maintain the PEMFC stack's operating temperature range (OTR) during downtime. Using 4 mm PCM and 11 mm insulation, the stack stays within the OTR for nearly 4 h, extending the OTR duration by 49.2 %. Consequently, the waste energy stored by PCM ensures the stack remains within the OTR, averting performance degradation upon restart.

STUDY ON TWO-PHASE FLOW AND TEMPERATURE UNIFORMITY CHARACTERISTICS OF MICROCHANNEL HEAT PIPE

In order to offset the local heat flux concentration phenomenon and ensure the steady performance of electronics, a test apparatus for evaluating the thermal performance of a microchannel heat pipe was constructed to investigate the thermal uniformity of the microchannel heat pipe under varying heat source placements. The experimental findings indicate that at a power of 25 W with the heat source positioned on plane C, the overall thermal resistance of the heat pipe differs by 60.1% compared to the local thermal resistance. Furthermore, the heat pipe exhibits a minimum overall thermal resistance of 0.3 K/W, highlighting improved temperature uniformity and quicker start-up performance. The mathematical model based on the lattice Boltzmann method is established and the dynamic operation mechanism of boiling and condensation under the action of local heat source in closed space is discussed. The simulation results suggested that when the heat source is positioned centrally on the underside, the diffusion of the working fluid vapor becomes more uniform and the most intense boiling occurs. The boiling of the working fluid in this area results in the most frequent and intense periodic improvement in heat transfer, thus achieving optimal thermal performance in terms of temperature distribution for the heat pipe.

Segmented thermal resistance model of flat-plate CLPHP based on PEMFC cooling

As a passive heat transfer superconductor for proton exchange membrane fuel cell (PEMFC) cooling, the heat transfer performance and temperature uniformity of flat-plate closed loop pulsating heat pipe (CLPHP) are the key factors to determine its application efficiency. Based on the geometric structure and working medium thermophysical properties of flat-plate CLPHP, this study establishes segmented and integral thermal resistance theoretical models for the heat transfer properties of each section of the flat-plate CLPHP. The calculation accuracy of the segmented and integral thermal resistance models is compared through experimental verification. The results show that the segmented thermal resistance model's temperature variation and temperature uniformity are more accurate than that of the integral thermal resistance model when the flat-plate CLPHP is started, operated stably, or at higher heating power. However, the model calculation error is relatively large when the heating power is relatively high at 400 W, but the calculation accuracy of the segmented thermal resistance model in temperature and temperature uniformity is 2.32 and 5.99 times that of the integral thermal resistance model. The segmented thermal resistance model provides a theoretical basis for improving the calculation accuracy of flat-plate CLPHP coupled PEMFC cooling.

(Digital Presentation) Dynamic Thermal Detection of Water Electrolyzer with Dual-Layer Characteristic Temperature Based on IR

As the prevalence of water electrolysis systems continues to expand, increased attention has been placed on the dynamic thermal detection of the electrolyzer. Presently, the scope of dynamic thermal detection for water electrolysis systems is limited to solely the temperatures at the inlet and outlet. This study propounds a novel dual-layer characteristics temperature (DLCT) model for the purpose of water electrolyzer temperature monitoring. The DLCT model addresses two significant issues of the dynamic thermal detection of the WEE: characteristic temperature extraction difficulty and signal perturbation caused by auxiliary factors. The first layer of multi-gaussian distribution (MGD) regression in the DLCT model quantifies the sectional temperature of the electrolyzer surface and produces numerous potential characteristic temperatures (CT). These temperatures are subsequently assigned to each section and are then conveyed to the second layer of linear regression, which provides an incisive quantized temperature variation pattern for the electrolyzer surface temperature distribution. Importantly, the DLCT model requires no supplementary modifications to the water electrolysis system or the installation of temperature sensors within or on the surface. By employing the DLCT model during dynamic operation, the ability to monitor the temperature of the electrolyzer comprehensively is improved, the temperature distribution of the electrolyzer can be quantized and richer insights regarding the surface temperature distribution can be gained, promoting better thermal uniformity, as well as pin-pointing the potential hot spot. Hence this method can also be used for structure design to produce better uniformity. The dynamic temperature detection results under different operating conditions are analyzed, and it can be concluded that the operating parameters, especially the lye circulation flow, can greatly influence the temperature distribution uniformity of the electrolyzer significantly. In conclusion, the DLCT model effectively handles the two primary challenges in dynamic thermal detection of water electrolysis systems by providing global and sectional characteristic temperature readings, enabling electrolyzer to be monitored holistically. So that future improvement regarding both structural and operational optimization can be conducted in improving the thermal uniformity. Figure 1

Deep reinforcement learning based toolpath generation for thermal uniformity in laser powder bed fusion process

Laser powder bed fusion (LPBF) is a widely used metal additive manufacturing technology. However, the accumulation of internal residual stress during printing can cause significant distortion and potential failure. Although various scan patterns have been studied to reduce possible accumulated stress, such as zigzag scanning vectors with changing directions or a chessboard-based scan pattern with divided small islands, most conventional scan patterns cannot significantly reduce residual stress. The proposed adaptive toolpath generation (ATG) algorithms, aiming to minimize the thermal gradients, may result in extremely accumulated temperature fields in some cases. To address these issues, we developed a deep reinforcement learning (DRL)-based toolpath generation framework, with the goal of achieving uniformly distributed heat and avoiding extremely thermal accumulation regions during the LPBF process. We first developed an overall pipeline for the DRL-based toolpath generation framework, which includes uniformly sampling, agent moving and environment observation, action selection, moving constraints, rewards calculation, and the training process. To accelerate the training process, we simplified the data-intensive numerical model by considering the turning angles on the toolpath. We designed the action spaces with three options, including the minimum temperature value, the smoothest path, and the second smoothest path. The reward function was designed to minimize energy density to ensure the temperature field remains relatively stable. To verify the effectiveness of the proposed DRL-based toolpath generation framework, we performed numerical simulations of polygon shape printing domains. In addition, four groups of thin plate samples with different scan patterns were compared using the LPBF process. The results indicated that using our proposed DRL algorithms for toolpath generation reduced the maximum distortion of the sample by approximate 47% compared to Zigzag patterns, 29% compared to Chessboard patterns, and 17% compared to ATG patterns. Our work demonstrated the effectiveness of implementing machine learning algorithms in the toolpath generation of the LPBF process.

Experimental investigations on the heat transfer characteristic of impingement/swirl cooling structures inside turbine blade leading edge

Experimental investigations were performed to study the heat transfer characteristics of impingement/swirl cooling structures inside a turbine leading edge (LE) as measured using the transient thermochromic liquid crystal (TLC) technique. The considered Reynolds numbers (Re) were 10,000, 20,000, and 30,000, and the effects of Re and the ratio of the impingement cooling hole offset distance to the impingement cooling hole diameter (e/d) on the heat transfer performance of the impingement/swirl cooling structures inside the blade LE were analyzed. The effects of the coolant outflow mode were also considered. The results show that the heat transfer intensity of the high heat transfer region of impingement/swirl cooling structures increases with Re. The e/d on the local Nusselt number (Nu) distributions for the two shooting areas are similar under different Re conditions. Changes in e/d significantly influence the heat transfer characteristics. As e/d increases from −1.5 to 1.5, the heat transfer effect and thermal uniformity of the LE inner wall chamber improved. Comparative analyses with the experimental results of the LE model without film cooling holes show that the thermal uniformity of the LE model significantly improves when including film cooling holes.

Thermal Performance Analysis of Liquid Cooling System in Lithium-ion Battery

Electric vehicles (EV) have been rapidly developing and are becoming increasingly popular due to its zero emission, low operating cost and noise free. However, there are some factors that limit the development of electric vehicles, such as the thermal performance, cost, lifetime and safety of the battery. To address this difficulty integration of liquid cooling system is the promising solution. The battery cooling technologies like air cooling system, liquid cooling system, direct refrigerant cooling system, phase change material (PCM) cooling system are used in e-vehicle. In this research, the main goal is to better understand how to improve the consistent temperature distribution in battery packs. The study provides general strategies to reduce thermal unevenness or achieve almost no differences in temperature within lithium-ion battery modules. These modules are cooled using channelled liquid flow, where a liquid circulates through channels designed for thermal management. To demonstrate the effectiveness of the proposed strategies, the research numerically analyzes two cases: one with multiple short channels and another with orderly magnified contact areas. Two of the methods demonstrate significant improvement in the overall thermal uniformity of the battery pack.(a) Shortening flow paths with multiple serpentine channels, and (b) enhancing contact areas between batteries and serpentine channels along the flow path in the stream wise direction, both show considerable promise in improving pack thermal uniformity.The study investigates the thermal effects of varying liquid flow rates in a computational fluid dynamics model for an 71 18,650 battery pack discharged at 5C. A three-dimensional model is built in ANSYS and the mesh is generated using Fluent Meshing. The maximum temperature differences observed across the battery module during a 5C discharge are 2.2 K for one strategy and 0.7 K for the other. This information highlights the effectiveness of the second strategy in achieving lower temperature variations, indicating better thermal uniformity during the discharge process compared to the first strategy.

A new design of cooling plate for liquid-cooled battery thermal management system with variable heat transfer path

Liquid-cooled battery thermal management system (BTMS) is of great significance to improve the safety and efficiency of electric vehicles. However, the temperature gradient of the coolant along the flow direction has been an obstacle to improve the thermal uniformity of the cell. In this study, a BTMS design based on variable heat transfer path (VHTP) was developed and applied to prismatic cells. Compared with the reference liquid cooling plate, the variable heat transfer path design changes the heat transfer path between the coolant channel and the battery surface by setting a reasonable groove, thereby changing the basic feature that the battery surface temperature rises monotonously along the flow direction. The geometric parameters of the trench are optimized. The results show that grooves with d1 = 0, d2 = 26 mm, d3 = 57 mm, and d4 = 0 are the best VHTP designs to improve thermal uniformity. The optimized VHTP cooling plate reduces the temperature difference across the battery surface by 22.7 % to 25.4 % for different discharge rates and cooling fluid mass flow rates, while slightly improving the maximum temperature on the battery surface, compared to the reference cooling plate.