Investigation on heat-transfer and flow performance in a two-turn curved microchannel with cavities using Air, N2, CO2, H2, and He

Abstract

Curved microchannels with cavities have attracted increasing attention due to their potential to enhance heat transfer in micro-scale cooling applications. This study addresses a gap in the literature by providing a comprehensive thermo-hydraulic assessment of a curved multi-turn microchannel with cavities using multiple coolant gases. Unlike previous studies that focus on single fluids or simplified geometries, the present work integrates detailed CFD simulations with an overall performance criterion (OPC) to evaluate the trade-off between heat transfer enhancement and hydraulic penalties. This approach enables a more realistic comparison of coolant performance under practical operating conditions. Five gaseous coolants, air, N 2 , CO 2 , H 2 , and He, are examined using three-dimensional CFD simulations without symmetry assumptions over a Reynolds number range of 200–800. The performance is evaluated based on surface temperature, convective heat transfer coefficient, and pumping power. In addition, an overall performance criterion (OPC) is introduced to quantify the trade-off between heat transfer enhancement and the associated pumping power penalty. The results show that H 2 provides the highest cooling performance; however, it yields the lowest OPC values due to a significantly higher pumping power requirement, raising practical concerns about safety and operation. In contrast, CO 2 demonstrates the highest OPC values, reaching approximately 2.0 at Re = 200, owing to its relatively low pumping power demand. At higher Reynolds numbers ( Re = 800), the OPC of CO 2 decreases to about 1.57, while H 2 shows an improvement of approximately 140%. These findings highlight the importance of considering both thermal performance and hydraulic costs when selecting a coolant. The results also suggest the need for further investigations into a wider Reynolds number range to identify optimal operating conditions. The present study provides useful insights for the design and optimization of microchannel-based cooling systems, particularly in selecting suitable coolant gases and evaluating the impact of multi-turn curved geometries. Multi-turn curved microchannels enhance heat transfer via Dean vortices. Coolant selection requires balancing cooling performance and pumping power. OPC provides a realistic design criterion.