부산대학교 도서관

Boiling point and bubble generations in the liquid-filled tube were measured by processing the signal from hydrophones (1) or piezoelectric chips (2) attached on the tube. The sensors need to be located as close as possible to the spots where boiling occurs. However, it is difficult to capture the onset of boiling if the sensors were distant from the bubbles. To address this issue, we propose heatable and pressurizable tube sensors detecting resonance frequency fluctuations to measure boiling instantaneously. Our tube resonators are composed of commercial stainless steel tubes and piezoelectric chips at two distal locations and can be directly connected to a power supply for Joule heating. While water is introduced into a tube resonator under Joule heating, the resonance frequency of the tube resonator is measured in real time by a phase-locked loop. At the onset of boiling, sharp increase of the resonance frequency occurs since there is significant density reduction due to the liquid-vapor phase transition. Such a sharp increase in the resonance frequency simply becomes an indicator for boiling. Since pressure within the tube can be easily elevated by same pressure regulators used for liquid injection, boiling point measurements can be performed at various pressures.