The influence of solar shielding on the thermal behavior of outdoor communication equipment

Remotely-deployed wireless devices such as tower-top active antenna arrays, remote radio heads, and pico- or femto-cells are an increasingly prevalent feature of communications systems. Outdoor devices can feature high levels of heat dissipation, and can operate in harsh atmospheric conditions with ambient temperatures as high as 55°C and wind speeds as low as 0m/s during periods of peak solar loading. In this paper, the influence of geometric and environmental parameters on outdoor communication equipment is examined. Using an analytical model and CFD analysis, a range of parameters, geometric and environmental, were investigated for a heat sink structure, with and without a solar shield, within a representative tower-mounted wireless device for a specific urban location at the hottest time of the year (Kuwait in Summer). The geometric parameters investigated were shield length, vertical position and clearance; and the environmental parameters were solar irradiation and orientation, and ambient temperature. For a fixed temperature rise above ambient, the heat dissipation from the sink structure reached a minimum at 13:30 in the day. There was a significant difference between this environmentally-defined worst case and the condition stipulated by telecommunications standard GR-487, which was more conservative. Shielding the heat sink marginally reduced solar ingress at the worst-case time of day, and facilitated marginally greater heat dissipation. Enhancing the length of the shield induced a chimney flow, which further augmented heat dissipation. The findings of this paper are of practical relevance for the thermal design of outdoor communications equipment: in particular, it is evident that the use of standard environmental conditions is conservative in comparison with a more comprehensive design process which references representative worst -case data.