A common problem encountered when designing a new product for demanding environmental conditions is specifying its leak tightness and measuring its seal integrity. Correlating empirical test data to production leak testing is an on-going challenge and a major source of confusion. Products of interest are those in automotive fuel and vapor management systems, A/C and cooling systems and power-train components and systems.
A simple solution to the problem is proposed in this paper, based on defining the maximum acceptable microchannel geometry called the Equivalent Micro Geometry (EMG). Various mechanisms of fluid transport through microchannels are summarized. Flow through two types of EMGs, sharp edged orifices and microchannels, are examined. A practical implementation of the EMG approach to determine leak tightness specifications of components, exposed to automatic transmission fluid, is presented.
Newly developed Intelligent Micro Flow Sensors enable, for the first time, direct measurement of airflow through microchannels in the viscous flow, slip flow, transitional and molecular flow regimes. This technology is used to demonstrate the implementation of the EMG concept for setting up an inline production leak tightness test with air, to provide cost effective solutions.