Abstract:

In the manufacture of heat exchangers or other devices filled with compressed gases or liquids, efficient detection of leaks is a critical process. Photoacoustics has been used to quickly detect these leaks in an industrial environment. Although this technology can detect leaks as small as 10[sup -6] standard cc/s, it has not been extended to localization or quantification of these leaks. This work aims to resolve these issues. An acoustic source strength based on the Beer-Lambert law and gas diffusion from a point source is developed and used to predict photoacoustic signals. The relationship between photoacoustic signals and leak test parameters, specifically leak rate, modulation frequency, and laser power, are presented. An effective strategy for illuminating the suspected leak area is shown, and leak detection using multiple microphones is discussed. A carbon dioxide laser tuned to 10.6 microns is used as the radiation source with sulfur hexaflouride as the tracer gas. Comparisons are made between theoretical predictions and experimental results. [Work sponsored by Ford Motor Company.]