Microscopic observations of three-dimensional thermal flow of micro droplets induced by evaporation

• Main Authors: Cheng Huang, 黃鉦
• Other Authors: Chin-Tai Chen
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/72077923837097049349

碩士 === 國立高雄應用科技大學 === 機械與精密工程研究所 === 100 === Production of micro parts by inkjet printing and evaporation of many different droplet materials on substrates involve droplet cooling, which is a common research subject. Although great progress is made by experiment and numerical simulation, fundamental mechanism of droplet evaporation is not clear in detail nowadays. The complete evaporation process still need theory and simulation to analytically predict the change of temperature in a fluidic field during evaporation. Hence, in this study a real-time image-capture system is developed to assist in reducing the test errors and improving accuracy in droplet evaporation experiments with visible and thermal images. The image-capture system is composed of a webcam, a digital CCD camera, a thermal imager and a light source, in which the image and storage system coded in NI LabVIEW program is operated to perform image captures of all connected devices with synchronization. The distribution of temperature within a liquid droplet is obtained by the thermal imager (IR). A liquid solution containing polystyrene particles (diameter: 10 μm) is used to assist in the observations of thermal flows. The evaporation process of droplets can be sustained with long time by using micro-droplets supply for observing their thermal images. Thermal experiments are performed to observe the symmetric droplets during liquid-film evaporation. Using the diluted polystyrene-particles solution, an eddy within the droplet is found near its center. In the study, we propose a novel method of observation in the thermal flow, assisting experimenters to perform their experiments compared with simulational results. In the future, further analysis for the relation between the thermal and fluidic fields during droplet evaporation can be achieved by the proposed method.