Study on Condensation of Water in Pneumatic Systems. 1st Report. Analysis Using a Homogeneous Condensation Theory.

In pneumatic systems, the condensation of water due to variations in air temperature is becoming a serious matter of concern. With the growing need to improve the characteristics and reliability of pneumatic systems, this problem is recently being given a great deal of attention. In this paper, the condensation in a pneumatic system is regarded as homogeneous condensation in which the condensation does not begin until the condensation nuclei are formed spontaneously from pure vapor molecules at a sufficiently high degree of supersaturation. The features of the condensation, the conditions of generation and the influencing factors are examined using a numerical simulation with a homogeneous condensation theory, for cases in which the compressed air is being exhausted from a container at a constant volume. Moreover, the results from using the homogeneous condensation theory are compared with that from the equilibrium condensation theory based on the assumption that a large number of condensation nuclei are in the air and the interface between liquid and gas is sufficiently large and flat. The temperature and pressure variations of air, which have a great influence on condensation, are predicted by the extended BGSP.