Ambient air cooling of electronics in an outdoor environment

Factors that define the outdoor environment include temperature, humidity, solar loading, UV, pollution and chemical exposures, salt, wind, rain, sleet and snow. The traditional method of ensuring a "clean" environment in outdoor electronics deployment applications is through the utilization of closed-loop systems that eliminate the exchange of outdoor air with the internally housed electronics equipment. Typical examples include a sealed enclosure with a closed loop heat exchanger or air conditioner that utilizes positive pressure to guard against ingress. This type of solution requires a tremendous amount of power and generates significant acoustical noise as well as providing above ambient temperature cooling. Telcordia developed GR-63-CORE and GR-487-CORE to define standardized methods to compare units and at times force solutions (like the use of a sealed enclosure and a heat exchanger). As a way to provide the proper level of cooling and protection for the electronics, a dual media filter system was developed that allows the use of ambient air for cooling. The primary filter media is intended for the removal of aerosol particulate, and the secondary filter media is intended for the removal of liquid vapor/mist from the aerosol. A study was conducted to compare a heat exchanger system to a dual media filter system and show that it not only provided the required cooling, but also prevented corrosion due to its ability to minimize the relative humidity and industrial pollutants.