Visualization at cryogenic temperatures using a glass fiber bundle Original Research Article

A visualization method is being used to investigate features of nucleate boiling in narrow channels of liquid nitrogen. The information regarding bubble size, departure frequency, bubble spacing, and velocity will be used to develop an analytical model for critical heat flux (CHF) – especially its dependence in narrow channels on inclination angle and gap spacing. We report on the use of a glass fiber bundle combined with two different photographic and illumination techniques to study the desired bubble characteristics. The special considerations encountered with this approach at liquid nitrogen temperature are highlighted, including the use of submerged light-emitting diodes (LEDs) for illumination.