Sinan Keyinci

Temperature control has a crucial effect on the efficiency, safety, and lifetime of lithium-ion batteries (LiBs). For this reason, developing effective cooling solutions remains an active area of battery thermal management research. In this study, a honeycomb-shaped (HC-S) liquid cooling plate (LCP) was designed and manufactured for the thermal management of a pouch-type LiB. Although biomimetic and HC-S cooling structures have been investigated in battery thermal management studies, experimental evaluations of honeycomb-inspired LCPs for pouch-type LiBs with different coolant media are still limited. Therefore, this study contributes to the literature by experimentally assessing HC-S LCP and directly comparing various coolant circulation under the same discharge condition. The LCP was produced from Aluminum 6061-T6 using Computer Numerical Control (CNC) machining and experimentally tested under a constant 1C discharge rate. Pure water and a 50% pure water-50% monoethylene glycol (MEG)-based coolant mixture were circulated through the plate to evaluate their cooling performance. Among the tested cooling scenarios, the best thermal performance was obtained with 100% pure water circulation. In this case, the maximum temperature (Tmax) on the battery surface decreased from 42.595 °C to 28.939 °C, corresponding to a 32.06% reduction compared with the uncooled condition. The average temperature (Tavg) on surface was also reduced by 29.12%, from 38.935 °C to 27.598 °C. In addition, pure water circulation improved temperature uniformity by lowering the maximum temperature difference (∆Tmax) on the battery surface to approximately 2 °C. The results show that the proposed HC-S LCP can effectively maintain the battery temperature within the optimum operating range of 15-35 °C and improve the thermal safety of LiB.

Bu çalışma, silindirik 18650 tipi lityum-iyon batarya paketleri için farklı kanal geometrileri ve giriş hızları altında sıvı soğutma plakalarını sayısal olarak incelemektedir. Üç boyutlu zamana bağlı CFD simülasyonları kullanılarak ısıl ve akışkan davranışının etkileşimi analiz edilmiştir. Soğutucu akışkan olarak saf su ve hacimce 50:50 oranında karıştırılmış su-etilen glikol karışımı kullanılmış; giriş hızları 0.1, 0.25 ve 0.5 m/s olarak belirlenmiştir. Sonuçlar, daha az sayıda ve daha geniş kanallara sahip konfigürasyonun en düşük maksimum sıcaklığı (Tₘₐₓ ≈ 305 K) ve en homojen sıcaklık dağılımını (ΔT

The Ahmed body is one of the most widely used generic models in automotive aerodynamics. Rear underbody diffusers are known to improve aerodynamic performance by enhancing pressure recovery. However, detailed flow analysis indicates that localized low-pressure regions and lateral vortex structures can limit the effectiveness of a fixed diffuser configuration. In this study, the flow behavior of a 35° Ahmed body equipped with an optimized underbody diffuser is investigated numerically. The analysis focuses on the detailed wake topology and pressure evolution along the diffuser surface to better understand the governing flow mechanisms. Flow visualizations show that side leakage and vortex cores developing near the lateral edges intrude into the diffuser channel and disturb the intended expansion process. To address this limitation, a variable-angle diffuser configuration is proposed and parametrically evaluated. The geometry is adjusted to control the lateral vortex interaction and stabilize the underbody expansion. The variable diffuser reduces side leakage intensity and improves wake alignment. Compared to the fixed diffuser configuration, an additional drag reduction of 51 drag counts is achieved. The results highlight that diffuser performance depends not only on the expansion angle but also on its interaction with lateral flow patterns developing near the underbody and wake regions.

In this study, a battery case was developed using a 3D (three dimensional)-printed composite of hexagonal boron nitride (hBN) and polylactic acid (PLA) to enhance the thermal performance of lithium-ion battery (LiB) modules. A 10 wt.% amount of hBN was incorporated into the PLA matrix to improve the composite’s thermal conductivity while maintaining electrical insulation. A 3S2P (3 series and 2 parallel) battery configuration was initially evaluated based on the results of a baseline study for comparison and subsequently subjected to a newly developed test procedure to assess the thermal behavior of the designed case under identical environmental conditions. Initially, X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were utilized for material characterization, and their results verified the successful integration of hBN by confirming its presence in the hBN-PLA composite. In thermal tests, experimental results revealed that the fabricated hBN-PLA composite battery case significantly enhanced heat conduction and reduced surface temperature gradients compared to the previous baseline study with no case. Specifically, the maximum cell temperature (T_max) decreased from 48.54 °C to 45.84 °C, and the temperature difference (ΔT) between the hottest and coldest cells was reduced from 4.65 °C to 3.75 °C, corresponding to an improvement of approximately 20%. A 3S2P LiB module was also tested under identical environmental conditions using a multi-cycle charge–discharge procedure designed to replicate real electric vehicle (EV) operation. Each cycle consisted of sequential low and high discharge zones with gradually increased current values from 2 A to 14 A followed by controlled charging and rest intervals. During the experimental procedure, the average ΔT between the cells was recorded as 2.38 °C, with a maximum value of 3.50 °C. These results collectively demonstrate that the 3D-printed hBN-PLA composite provides an effective and lightweight passive cooling solution for improving the thermal stability and safety of LiB modules in EV applications.

The energy that powers electric vehicles comes directly from their high-performance batteries, serving as the heart of their operation. They convert stored chemical energy into mechanical energy to propel vehicles. One of the most vital parts of an electric vehicle is a battery pack. Superior advantages such as higher energy density, longer life cycles, and the fast-charging ability of lithium-ion batteries set them apart from the others. However, battery performance and longevity exhibit a high degree of temperature sensitivity. In other words, operating batteries below and above the specified temperature range values causes problems such as decreased lifespan, safety issues, and performance losses. In electric vehicles, varying power demands during driving cause different current levels to be drawn from the battery packs. This leads to fluctuations in battery temperatures due to chemical reactions occurring. Besides that, regional and seasonal temperature variations also affect the operating temperatures of batteries. Therefore, maintaining the batteries within the specified temperature range, typically between 25 and 40 °C, is only achievable with an adequate battery thermal management system. This review intends to guide researchers working on designing more efficient thermal management systems by providing refined information about previous efforts in this field. The designs found in the literature have been illustrated with simplified figures. Cooling inlet and outlet locations are indicated in blue and red, enabling easier comparison and better understanding of different cooling designs. Air-cooling studies in the literature show that a well-designed system can keep the T_max and ΔT values of LiB cells ~305 K and 2.8 K during 3C discharge at a T_ambient of about 298.15 K. When liquid cooling systems are examined, a 50% glycol–water mixture can maintain pouch cells at nearly 30.3 °C with a ΔT of 2.78 °C under similar 3C and 25 °C conditions. Overall, the results demonstrate that well-designed BTMS configurations including optimized airflow or coolant–flow arrangements are capable of keeping LiBs safely within their optimal thermal operating conditions.

Temperature is a crucial parameter for ensuring the long lifespan and safe operation of lithium-ion batteries (LiBs). An efficient battery thermal management system (BTMS) tries to maintain temperature in between optimum limits. Despite some disadvantages, air-cooled BTMSs are still preferred due to their advantages such as light weight, simple design, low cost, and ease of maintenance. This study experimentally evaluated a fan-assisted BTMS for the purpose of cooling a 4S2P battery module that includes 18650 type cells. The battery module was initially tested with no cooling system to observe the temperature characteristics of the module, followed by testing with forced air cooling using a fan. Experiments were also conducted with perforated plates installed between the fan and the module to see their effects on the thermal behaviors. Tests were initiated when the ambient temperature was approximately 25 °C and the discharges were carried out by drawing constant currents of 4 A, 8 A, 12 A, and 16 A from the module via an electronic load. The results of this study highlighted the importance of an effective BTMS in ensuring battery safety and performance across different operational conditions. While all tested cooling configurations maintained acceptable temperature levels at lower discharge currents (4 A and 8 A), they struggled to do so at higher currents (12 A and 16 A). Among them, the Fan–HC mode demonstrated the highest efficiency, reducing the maximum temperature (T_max) by 38.82% at 12 A and 28.89% at 16 A compared to the no-cooling scenario. Moreover, it ensured a more uniform temperature distribution within the module. These findings emphasize the necessity of optimized cooling strategies, particularly for high-power applications.

In research automotive aerodynamics, it is not common to focus on a specific vehicle due to restricted access to the CAD geometries, their short life span, and limited validation data. For this reason, researchers prefer generic bodies that look like automobiles such as Ahmed Body in their investigations. However, the absence of moving ground and rotating wheels makes these generic bodies unrealistic for aerodynamic studies. In this context, including wheels in CFD simulations, varying ground and wheel boundary conditions, and comparing their qualitative and quantitative flow parameters with the original Ahmed Body experiment is the main objective of this paper. Results have shown that changing stationary ground and wheel boundaries into moving and rotating boundaries do have minor effects on wake characteristics and drag coefficients. However, just the presence of wheels on the model increases force coefficients significantly (increment in drag and lift coefficients by 27.32% and 188.5 counts, respectively.) even though these boundaries are stationary. As a result, the absence of moving ground and rotating wheels can be tolerated to some extent (especially for experimental studies in which inclusion of moving and rotating boundaries may have difficulties). However, a study cannot be evaluated exactly with a model without wheels.

Bu makalede, otomotiv aerodinamiği literatüründe sıklıkla kullanılan Ahmed cismi için bir HAD benzetiminde ağ oluşturma stratejisi üzerine bir çalışma yapılmıştır. Genel olarak bu çalışmalarda, türbülanslı sınır tabaka bölgelerini modellemek için prizmatik ağ katmanı oluştururken farklı yöntemler gözlemlenmektedir. Yetersiz bir prizmatik ağ katmanı sınır tabakasını çözmede eksik kalırken, bu katmanın gereğinden fazla olması ise ağ sayısını, dolayısıyla çözüm sürelerini artırmaktadır. Bu çalışmada, Ahmed cisminin akış yapısı, Ansys-Fluent™ programı ile akış hızına (U∞=40 m/s) ve gövde uzunluğuna bağlı Reynolds sayısı Re=2.83×106 olacak şekilde incelenmiştir. Matematiksel ifadelerden yararlanılarak oluşturulan prizmatik ağ katmanı ve bu ağın sonuçları hem nitel hem de nicel yönden incelenip, farklı bir strateji geliştirilen son bir ağ ile sonuçlar tekrar değerlendirilmiştir. Sonuç olarak, kabaca oluşturulan ilk ağ ile sonradan geliştirilen ağlar arasında, sınır tabakası üzerindeki akış profilini modellemede daha iyi bulgular elde edilmiştir. Ayrıca CD ve CL için deneysel yöntemle elde edilen sonuçlara, geliştirilen ağlarda, kabaca uygulanan ağa göre daha yakın sonuçlar elde edilmiştir.