Effect of mechanical vibration on flow and heat transfer characteristics in rectangular microgrooves

The effects of vertical mechanical vibration on the flow characteristics of a liquid film in vertical rectangular microgrooves are observed, and the heat transfer characteristics of the liquid film are analyzed by a simplified mathematical model. The vibration frequencies are 6 Hz, 10 Hz and 30 Hz, respectively, and the maximal displacement of the microgroove plate is 4.15 mm. The width of the microgrooves ranges from 0.2 mm to 0.4 mm, while the depth ranges from 0.2 mm to 0.6 mm. The experimental results show that the dry point is impelled upward and the wetting length is elongated by the vibration; the contact line is regularly elongated or shortened alternately in one vibration cycle; and the shape of the contact line changes obviously with the increasing vibration frequency or amplitude. Our mathematical analysis shows that the heat transfer in the microgroove is intensified by the vibration because the wetting area in the microgroove is enlarged, but the ratio of the heat transfer through the evaporative thin film to the total heat transfer remains at around 0.9 and is little changed by the vibration. Therefore, the intensive evaporation in the micro region dominantly contributes to the total heat transfer in the microgroove no matter the mechanical vibration happens or not.