Abstract: Condensation greatly reduces performance and life of pneumatic systems, and it is important to judge and prevent it in engineering practice. There are many factors that influence condensation of pneumatic systems, and there is no simple criteria easy to use till now. The influence of structure parameters of pneumatic components on system condensation is studied by more than 1 000 experiments. The dominant parameters that have significant influence on condensation were found, namely container volume V, length of exhausting tube l and section area of exhausting tube A. By introducing dimensionless volume of exhausting tube and dimensionless section area of outlet of container in the further analysis of experimental results, a very simple and thus very useful criterion, dimensionless volume of exhausting tube Al/V, is finally achieved to judge if inner condensation or outer condensation would occur or not. Outer condensation systems, non-condensation systems and inner condensation systems exist subsequently from left to right along the axis of Al/V. The critical value of those zones would change as running conditions change, but would not change while the structure parameters of pneumatic components change.

Key words: Condensation, Pneumatic systems, Structure size Dimension analysis