The effects of aspect ratio on the heat transfer characteristics of boiling mini-channel flow

Flow boiling demonstrates superior heat transfer performance and holds significant potential for thermal management applications. In this study, the great effects of aspect ratios of mini-channel on flow boiling heat transfer are reported by the numerical simulation method. Regarding the heat transfer coefficient (HTC), a boiling number threshold of 5.0 × 10−4 is obtained. Below this value, bubble detachment is not yet constrained by the channel, reducing the dry patches and providing better heat transfer at larger aspect ratios. Above this threshold, boiling becomes more intense, bubble size increases, making detachment easier in smaller aspect ratios, which show superior heat transfer performance. For the critical heat flux (CHF), at a flow rate of 0.1 m/s, the CHF for smaller aspect ratios is 77.78% higher than for larger aspect ratios. As the flow velocity increases, inertial forces begin to dominate bubble behavior, reducing the influence of channel size effects, and the differences in CHF gradually decrease. When the flow velocity exceeds 0.5 m/s, bubble behavior becomes similar, and the difference in CHF drops to less than 10%. This research highlights key parameters for optimizing mini-channel design, promoting the refinement and development of mini-channel structures.