Session: 13-02: Thermal management applications - Heat exchangers

Paper Number: 151174

Experimental Investigation of Enhanced Heat Sinks for Hybrid Electric Aircraft 

Managing the heat generated by onboard battery systems is a major thermal management challenge for hybrid/ electric aircraft. Calogy Solutions, Ltd. (Sherbrooke, Quebec, Canada) has introduced an innovative approach for controlling battery cell temperatures in electric vehicles. However, their initial solution –a standard plate-fin heat sink– proved inefficient for aircraft applications. This paper presents the design and testing of two optimized heat sinks specifically developed for the battery thermal management system of a hybrid electric aircraft, and compares their performance with the original plate-fin heat sink.

Pin fin heat sinks are popular for cooling applications due to their superior heat transfer capabilities. However, designing these heat sinks involves balancing thermal performance, pressure drop, and manufacturing constraints. This study focused on optimizing a heat sink for the battery thermal management system of a kW-scale hybrid/electric aircraft to meet specific requirements. The optimization process included two key approaches: fin optimization and surface modification. Parametric studies were performed to identify optimal configurations, and multi-variable optimization using a weighted objective function was applied to select the best models. Optimization criteria included thermal and hydraulic performance, weight, and fabrication challenges, with each factor normalized and weighted based on its importance. The optimal configuration identified was square fins with a width of 1.1 mm, height of 15 mm, and a pitch-to-height ratio of 0.15. This configuration showed an 81% improvement in heat transfer coefficient and a 24% reduction in weight compared to the original plate-fin heat sink. Additionally, another optimized heat sink was created using surface modifications with micro-fins on both sides of each fin. This pattern featured staggered square microstructures with a height-to-width ratio of 4. The testing results for these optimized heat sinks are detailed in this paper. 

A custom-designed box was created to direct airflow into the heat sinks, modeled in accordance with the specifications used in CFD analysis. Testing was conducted across two different airflow rate ranges. For higher flow rates, the box's inlet duct was connected to a section downstream of the nozzle and the wind tunnel's flow conditioning area. The airflow in the wind tunnel was controlled by adjusting the blower frequency. For lower flow rates, a fan was placed at various positions within the inlet duct, and two different perforated plates, with open areas of 40% and 79%, were placed on top of the duct.

The results from both the blower and fan tests showed that the modified heat sink outperforms the original in terms of thermal performance. Significant improvements were observed at higher airflow rates and greater source powers. Furthermore, the location of the fan did not seem to provide any particular advantage. Experimental results were in strong agreement with numerical simulations, though the experiments indicated a more substantial performance enhancement with the modified heat sink than what the simulations predicted.

Presenting Author: Faezeh Rasimarzabadi National Research Council Canada

Presenting Author Biography: Dr. Faezeh Rasimarzabadi completed her Ph.D. in Aerospace engineering and received a Post-Doctoral from University of Alberta in Mechanical Engineering. She currently works at the Aerospace Research Center, National Research Council Canada as an Associate Research Officer in the Propulsion and Power Laboratory. Her primary research focus has been on key research in hybrid electric aircraft technologies, including developing and validating new airframe-engine configurations, and thermal management systems.

Authors:

Faezeh Rasimarzabadi National Research Council Canada
Utkarsh Sheel Anand Carleton University
Evgueni Bordatchev National Research Council Canada
Hassan Azarkish Calogy Solutions
Mahmood Shirazy Calogy Solutions