2021 年 87 巻 899 号 p. 21-00102
The thermodynamic suppression effect of cavitation occurs in cryogenic fluid, hot water, and Freon, which suppresses cavity development. In this study, the purposes are to clarify the characteristics of the thermodynamic suppression effect in hot water up to 140 ℃, where the thermodynamic suppression effect is expected to be comparable to that of liquid nitrogen or liquid oxygen, and its relationship with the scale effect, which promotes cavitation. To detect the small variation of the temperature inside the cavity, the thermistor was calibrated by using the secondary standard platinum resistance thermometer. The cavity length and temperature depression inside the cavity were measured as indicators to evaluate the thermodynamic suppression effect quantitatively. By increasing mainstream temperature under constant mainstream velocity, the cavity length was unchanged up to 100 ℃. These results can be attributed to a mixture of the thermodynamic suppression effect and promotion effect due to the scale effect caused by the change of Reynolds number. As for temperature depression, it was found that temperature depression was increased as mainstream temperature increased even when the thermodynamic suppression effect and promotion effect due to scale effect are mixed. By increasing mainstream temperature under constant Reynolds number, the scale effect was taken away to some extent and the cavity length was shortened at 100 ℃.
