A Study On The Effects Of Temperature In Air Leak Detection

Air leak detection technology is essential for products quality, energy saving and environment protection in modern industrial production processes and normal life. But for the nature of air the temperature has great effects on the testing result. The mathematical model of pressure-based air leak detection system is established in this study. The effects of temperature on testing results are analyzed based on simulation and experiments.Firstly, the mathematical model of leaking chamber is presented based on the principles of gas dynamics and thermal dynamics. The influences of ambient temperature on the pressure, temperature and leak rate of chamber are analyzed using numerical simulation in pressure-based air leak detection. Simulation results show that the ambient temperature has greater effects on the testing accuracy of direct-pressure-based air leak detection in testing smaller leak rate. The differential-pressure-based air leak detecting results are greater than the real leak rate of chamber before the recovery of air temperature and are smaller after the recovery of air temperature. The detection bias of differential-pressure-based air leak detection system is greater in larger volume, leak and higher testing pressure of chamber.Secondly, the direct-pressure-based air leak detection system is designed and established. The computer control software is also carried out based on LabVIEW software development platform. The experimental study on influence of changing ambient temperature on direct-pressure-based air leak detection results is proposed. The experimental results show that small leak of chamber has less influence on air temperature. The leak rate is decreasing with air pressure decreasing and temperature rising in positive pressure-based leak detection. And the leak rate is decreasing with air pressure increasing and temperature rising in negative pressure-based air leak detection. The equivalent of heat-transfer coefficient is increasing with air temperature falling and decreasing with air temperature rising.Finally, a pressure and heat-transfer coefficient based air leak detection is proposed. And compared with normal direct-pressure-based air leak detection, the testing results are analyzed. The detection results show that this method can decreasing the influence of ambient temperature in small heat-transfer coefficient chamber testing.The researches lay the foundation for further study of temperature effects in air leak detection.