@misc{KondaSharmaMathiazhagan, author = {Konda, Karunakar Reddy and Sharma, Dikshant and Mathiazhagan, Akilan}, title = {Quantitative assessment of cooling methods for electrical machines in aircraft drives}, series = {IEEE Access}, volume = {12}, journal = {IEEE Access}, publisher = {IEEE}, address = {New York}, issn = {2169-3536}, doi = {10.1109/ACCESS.2024.3517319}, pages = {192768 -- 192785}, abstract = {Transformation of the aviation sector towards climate-neutral solutions such as electrification is urgent. Aviation electrification requires reasoned selection of suitable technologies which has to meet strict requirements and standards. Cooling of electrical components plays a vital role in the sizing and overall performance of the electrical drive system and must achieve high effectiveness and reliability at low weight. Three cooling methods - air cooling, direct slot cooling and cooling jacket - are sized for a 300 kW commuter aircraft (CS23) all-electric propulsion system. They are further evaluated quantitatively for weight, drag, reliability and effectiveness in a conservative assessment. A lumped parameter thermal network (LPTN) approach is utilized to assess and evaluate the thermal performance of the cooling systems. The LPTN model served as the basis to determine the temperature limits and capabilities of the cooling system which are then utilized to size the auxiliary components. Reliability is assessed via fault tree analysis, drag via scoop inlet characteristics and effectiveness via the heat load dissipated per weight of the system and the required cooling power per mechanical power. Cooling jacket achieves the highest effectiveness closely followed by slot cooling. Air cooling proves to be most reliable and lightest.}, language = {en} } @misc{SharmaMedinaMendezSchmidtetal., author = {Sharma, Dikshant and Medina M{\´e}ndez, Juan Ali and Schmidt, Heiko and Cremer, Tilman}, title = {Seasonal cold storage with borehole heat exchangers: an application study using numerical simulations}, series = {Tagungsband des Jahrestreffens der DECHEMA-Fachgruppen Computational Fluid Dynamics und W{\"a}rme- und Stoff{\"u}bertragung, 6.-8. M{\"a}rz 2023, Frankfurt am Main, Deutschland}, journal = {Tagungsband des Jahrestreffens der DECHEMA-Fachgruppen Computational Fluid Dynamics und W{\"a}rme- und Stoff{\"u}bertragung, 6.-8. M{\"a}rz 2023, Frankfurt am Main, Deutschland}, publisher = {DECHEMA e.V.}, address = {Frankfurt am Main}, pages = {18 -- 19}, language = {en} } @misc{KoenigSharmaKondaetal., author = {K{\"o}nig, Paul and Sharma, Dikshant and Konda, Karunakar Reddy and Xie, Tianxiao and H{\"o}schler, Klaus}, title = {Comprehensive Review on Cooling of Permanent Magnet Synchronous Motors and Their Qualitative Assessment for Aerospace Applications}, series = {Energies}, volume = {16}, journal = {Energies}, number = {22}, issn = {1996-1073}, doi = {10.3390/en16227524}, abstract = {The permanent magnet synchronous motor (PMSM) can be a suitable candidate for electrified propulsion in aviation. Despite the very high efficiency, heat dissipation during operation leads to performance limitations. Elevated temperatures in the electrical insulations and the magnets pose a potential safety risk that must be reduced by selective cooling. A comprehensive review is conducted to capture current research interests in cooling methods in PMSM. Cooling methods are described according to their heat transfer mechanism, grouped, and assigned to the components within the motor. Key findings of the literature reviewed are described in the context of PMSM cooling. Information on cooling media and potential combinations of cooling methods in components is gathered. Assessment parameters such as safety, weight, effectiveness, integrability, complexity and cost are defined to enable a subsequent qualitative analysis for six selected cooling methods. A point-weighted evaluation approach, according to VDI 2225, was applied to identify the most promising cooling approach for successful implementation in aviation.}, language = {en} } @misc{AsliKoenigSharmaetal., author = {Asli, Majid and K{\"o}nig, Paul and Sharma, Dikshant and Pontika, Evangelia and Huete, Jon and Konda, Karunakar Reddy and Mathiazhagan, Akilan and Xie, Tianxiao and H{\"o}schler, Klaus and Laskaridis, Panagiotis}, title = {Thermal management challenges in hybrid-electric propulsion aircraft}, series = {Progress in Aerospace Sciences}, volume = {144}, journal = {Progress in Aerospace Sciences}, issn = {1873-1724}, doi = {10.1016/j.paerosci.2023.100967}, pages = {1 -- 29}, abstract = {The utilization of hybrid electric propulsion concept in aviation offers a viable solution to address the limitations posed by the relatively low energy density of batteries in fully electric aviation. These hybrid systems enable the aircraft to achieve a significant range while simultaneously minimizing carbon emissions. While the individual components of a Hybrid Electric Propulsion (HEP) system, such as electric motors and batteries, are designed with high efficiency, their integration presents a significant challenge in the realm of thermal management. Designing an efficient system for managing the substantial waste heat generated by heat sources and effectively transferring it to heat sinks during various flight phases is a complex task. This challenge becomes even more critical as the design must adhere to system weight limits and prioritize aviation safety considerations. In this review article, we performed a systematic review of the challenges related to the key elements in a thermal management system. These elements encompass every component or subsystem that contributes to the thermal management of a generic hybrid-electric propulsion system. This includes electric motors and generators, batteries, heat exchangers, power transmission systems, power distribution systems, storages, fuel cells, cooling fluids and pipes, control system, pumps and fans. Following the identification of the challenges, the paper provides a comprehensive summary of the existing solutions that have been offered and pursued by the community to address the challenges. Furthermore, the paper also discusses emerging technologies related to each element, highlighting their potential in overcoming these challenges.}, language = {en} } @misc{SharmaRadomskyMathiazhaganetal., author = {Sharma, Dikshant and Radomsky, Lukas and Mathiazhagan, Akilan and Asli, Majid and H{\"o}schler, Klaus and Mallwitz, Regine}, title = {Thermal analysis of metal foam integrated heatsink for electrified aircraft applications}, series = {International journal of thermofluids}, volume = {30}, journal = {International journal of thermofluids}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {2666-2027}, doi = {https://doi.org/10.1016/j.ijft.2025.101465}, pages = {1 -- 21}, abstract = {Metal foams facilitate large heat dissipation in high-power dense systems such as power electronics for electrified propulsion application. This work addresses the cooling of a power semiconductor device with aluminium and copper metal foam integrated hybrid heatsink and its comparative analysis to a conventional finned heatsink using 0D and 3D modelling approach. Two equation foam model in Fluent is utilized and the numerical approach is validated against experimental dataset. Inlet air velocity is varied such that the Darcy to turbulent regimes of the open-cellular foams are covered. Foam porosities from ∼ 0.85-0.95 with 10-20 PPI are investigated and the thermal performance of the heatsink is found to be independent of the foam material. High porosity (> 0.9), 20 PPI foams are found to aid forced-convection by improving the thermal resistance by more than 10\% against the 10 PPI counterparts. The hybrid heatsink outperforms the foam-based and conventional heatsink by 40\% and 15\% respectively when considering the reduction in junction temperatures, while the hydraulic resistance increases 10 times when compared to the conventional one. The 0D thermal resistance model is robust in predicting the junction temperatures for metal foam heatsinks with only a 5\%-6\% discrepancy for both the 50 W and 100 W heat load scenarios. The key and novel contribution of this study is the integration of detailed 3D simulations of a power electronics cooling environment with the development of a corresponding 0D thermal model. This approach not only eases the physical representation of the system but also enables the model to be extended to diverse heat load conditions.}, language = {en} } @misc{SharmaRadomskyMathiazhaganetal., author = {Sharma, Dikshant and Radomsky, Lukas and Mathiazhagan, Akilan and Konda, Karunakar Reddy and Hammami, Ghaieth and Asli, Majid and H{\"o}schler, Klaus and Mallwitz, Regine}, title = {Strut-based porous media heatsinks for high-performance power electronics thermal management in electrified aircrafts}, series = {ASME Turbo Expo 2025 : Turbomachinery Technical Conference and Exposition : Volume 4: Controls, Diagnostics \& Instrumentation; Cycle Innovations; Education; Electric Power : June 16-20, 2025, Memphis, Tennessee, USA}, volume = {4}, journal = {ASME Turbo Expo 2025 : Turbomachinery Technical Conference and Exposition : Volume 4: Controls, Diagnostics \& Instrumentation; Cycle Innovations; Education; Electric Power : June 16-20, 2025, Memphis, Tennessee, USA}, number = {V004T06A011}, publisher = {The American Society of Mechanical Engineers}, address = {New York, NY}, isbn = {978-0-7918-8880-3}, doi = {10.1115/GT2025-152670}, pages = {1 -- 11}, abstract = {Multi-level inverters are one promising solution for high-power applications, enabling higher efficiency and improved power quality over conventional inverters. The emergence of these converter topologies with a larger number of topological switches makes reliable, forced and even natural convection air cooling a feasible option for aircraft power electronics. The need for high heat dissipation rate, robust design and lightweight heatsinks has led to the development of strut-based porous media structures for forced air cooling. The current work focuses on investigating Kelvin, Body-Centered Cubic (BCC) and Simple Cubic (SC) periodic open cellular structured (POCS) lattice heatsink with a fixed porosity and a fixed unit cell size. 3D printed Kelvin and SC heatsinks using AlSi10Mg material are tested in an air duct experimental setup along with a conventional LAM aluminium heatsink. The Computational Fluid Dynamics (CFD) simulation model is validated with the experimental results and a 0D thermal model is developed using the CFD results. The CFD thermal results are in close accordance with the experimental results for the POCS heatsink within an error band of ±2\%. The 0D results using the thermal data from CFD simulations also show a close comparison for the calculated semiconductor junction temperatures. The Kelvin heatsink performs the best thermally from the CFD analysis and has the least error when comparing the 0D and 3D-CFD results.}, language = {en} }