Enhanced flow boiling in an interconnected microchannel net at different inlet subcooling

• IMN yields higher HTC and lower pressure drop at low to medium inlet subcooling.
• IMN significantly suppresses the two-phase instability at low to medium inlet subcooling.
• Reentrant and segmented structures of the IMN lead to superior flow boiling heat transfer.
• HTC changes in line with the transition from nucleate boiling to convective boiling heat transfer.

An interconnected microchannel net (IMN) was developed by using traditional wire electric discharge machining method to explore the feasibility of enhancement and application in confined cooling. It features orthogonally parallel channels on the both sides with the channel depth exceeding half the substrate thickness to ensure the interconnectivity. Two-phase boiling heat transfer performance of the IMN was evaluated and a comparison with conventional rectangular microchannels (RMC) was investigated. Using deionized water as the coolant, flow boiling tests were conducted with variation in the heat flux and inlet subcooling of 10, 40 and 70 K. The results showed the IMN yielded higher heat transfer coefficient and lower pressure drop at subcooling of 10 and 40 K, while the advantage diminished when the subcooling increased to 70 K. A transition of boiling mechanism from the nucleate boiling region to the convective boiling region occurred with increase of vapor quality, which was accompanied with the flow pattern changing from the bubbly flow to annular flow. Further study revealed that the IMN can significantly mitigate the two-phase flow instability due to the unique reentrant and segmented structure characteristics, indicating a highlight for the potential application in the flow boiling enhancement of microchannel heat transfer.