Abstract
The values of heat-transfer coefficients decrease in a drag-reducing surfactant solution flow. Therefore, it is necessary to develop an effective method for enhancing the heat transfer of a surfactant solution flow. The objective of this study is to examine the heat transfer enhancement effect when microbubbles are injected into a drag-reducing surfactant solution flow. Specifically, the relationship between microbubble size and the heat transfer enhancement of a surfactant solution flow was investigated experimentally. Microbubbles were generated using a porous metal pipe placed in a test pipe. Microbubbles having different sizes were generated by using three types of porous metal pipes. The flow patterns observed in air microbubble-surfactant solution two-phase flows were fine bubbly; these patterns were independent of microbubble size. The heat transfer enhancement effect depends on the air-surfactant solution flow ratio or microbubble size. An increase in the air-surfactant solution flow ratio or decrease in the microbubble size leads to a greater heat transfer enhancement effect.
