Effect of operational parameters on flow boiling heat transfer performance for porous interconnected microchannel nets

Abstract

A porous interconnected microchannel net (PIMN) is proposed as an effective structure in this study. As a combination of IMN and sintered porous material, the PIMN was fabricated via solid-phase sintering and wire electric discharge machining with orthogonally interconnected microchannels on the both side of the porous matrix. Two-phase heat transfer performance of the PIMN was investigated and evaluated through flow boiling experiments utilizing deionized water as the coolant at different operation parameters (mass flux and inlet subcooling). The results showed that the heat transfer enhancement by the PIMN was outstanding comparing to the reentrant porous microchannels (RPM) thanks to the interconnected microchannels and porous structure. The PIMN under the condition of higher mass flux or inlet subcooling yielded better two-phase heat transfer performance, including the higher heat transfer coefficients and lower pressure drop. Visualization images captured by high speed camera revealed that the flow pattern inside the PIMN transformed from bubbly flow to annular flow as the boiling mechanism developing from nucleate boiling into convective boiling. Further study in two-phase flow instabilities showed that more stable two-phase flow for the PIMN leads to better pressure drop and boiling heat transfer performance.