CFD simulation and statistical analysis of moisture transfer into an electronic enclosure

Condensation and moisture related problems are the cause of failures in many cases and consequently serious concerns for reliability in electronics industry. Thus, it is important to control the moisture content and the relative humidity inside electronic enclosures. In this work, a computational fluid dynamics (CFD) model is developed to simulate moisture transfer into a typical electronic enclosure.

In the first attempt, an isothermal case is de- veloped and compared against the well-known RC circuit analogy considering the behavior of an idealized electronic enclosure. It is shown that the RC method predicts a faster trend for the moisture transfer into the enclosure compared to the CFD. The effect of several important parameters, namely, position of the opening, initial relative humidity inside the enclosure, length and radius of the opening and temperature is studied using the devel- oped CFD model for the isothermal case.

The model is then combined with a two level factorial design to identify the significant factors as well as the potential interactions us- ing the numerical simulation results. In the second part of this study, a non-isothermal case is studied, in which the enclosure is exposed to two different conditions, i.e., in- ternal temperature oscillation only and combined cyclic changes of ambient relative hu- midity and temperature.

The results are compared with experimental data from literature, and show that the local climate inside the enclosure responds faster to the temperature changes compared to the RH changes. The trends predicted by the CFD simulations can be used to decide for the right time and position of a commercial adsorbent and/or thermal mass inside the enclosure to control the local climate.