An analysis of ethanol evaporation and flow at triangular capillary ports at different tilt angles

The use of shaped microchannels has become increasingly prevalent in heat engine and microelectronics industries due to their exceptional heat dissipation efficiency. However, limited research has addressed the evaporation characteristics of special-shaped capillaries under inclined orientations. At the capillary scale, the effects of gravity and surface tension are comparable, making their interplay particularly relevant. This study investigates the combined impact of gravity and capillary driving forces on the ethanol evaporation characteristics at the opening of triangular capillary tubes with different inclination angles. The temperature distribution and morphological changes of the meniscus during evaporation were explored using infrared thermography and video microscopy. Additionally, the internal flow structure of the meniscus was analyzed using particle image velocimetry technique (PIV). Comparisons were made among the evaporation characteristics at the opening of capillary tubes with different inclination angles (0°, 30°, 60°, and 90°) and cross-sectional shapes (circular and triangular). The results show that the inclination angle of triangular capillary tubes significantly influences the liquid level, corner liquid film thickness, temperature distribution, and flow pattern during ethanol evaporation. Increased inclination angle reduces the corner liquid film thickness, enhances heat transfer efficiency, and accelerates the evaporation rate. However, when the corner liquid film becomes excessively thin, liquid supply is impeded, which hinders the overall evaporation process. The fastest evaporation rate is observed at an inclination angle of 60°, accompanied by the lowest and most uniform temperature distribution at the meniscus.