ENHANCED FLOW BOILING OF HFE 7000 BY CHAOTIC MIXERS IN MICROCHANNELS

摘要

Improving mixing is an effective method to enhance flow boiling in microchannels. However, it is challenging to induce since the flow in microchannels is laminar under typical operating conditions. We report that flow boiling of 1-methoxyheptafluoropropane (HFE 7000) in a parallel microchannel array was significantly enhanced by chaotic mixers patterned on the bottom walls. The microchannel array consists of five parallel channels (height, width, length: 250 μm × 220 μm × 10 mm). The chaotic mixers consist of seven cycles with 12 staggered herringbone grooves (50 μm depth and width with 90° between two asymmetric arms) in each cycle. Its asymmetry is defined by the off center position of the apex of the herringbone groove. Compared with a smooth-wall microchannel array with identical channel dimensions, heat transfer coefficient and critical heat flux of flow boiling on HFE 7000 were enhanced up to 45 % and 61 % using chaotic mixer pairs in microchannels. Mass fluxes range from 1000 to 2200 kg/m~2-s and wall heat fluxes from 10 to 198 W/cm~2.