Cleaning effects of micro-bubbles were experimentally investigated. Pipe flows with and without the micro-bubbles were used for the study of the cleaning effects. The lard oil was used as a stain sample which was painted on the inner surface of the pipe. Removal rate of the lard oil was measured by a laser induced fluorescence method. Coumarin153 was added into the lard oil and was used as a fluorescent material. Reduction rate of fluorescence intensity from the lard oil by the micro-bubble flow was higher than that in water flow. Removal patterns of the lard oil were observed by a microscope. It was found that the micro-bubble flows had higher cleaning effects compared with water flows.
