Overheating and frequent thermal cycling of outdoor electronic cabinets in cold climates

Telephone companies use electronics to route calls between customers. The electronics are generally closely packed together and placed in steel containers outdoors. Forced air convection utilizing the outside ambient air is an effective means to cool outdoor electronic cabinets and is generally the system of choice given the relatively low cost and simplicity when compared to alternative cooling methods. Simple axial flow fans are typically turned on and off by a thermostat located inside the cabinet to keep the inside air temperature below a predetermined maximum. This simple cooling system is usually effective during summer operations. However, it may result in overheating and excessive thermal cycling in winter operations. Transient temperature data from experiments on a telecommunications cabinet is presented illustrating this problem. One possible solution to this problem is using continuously operating fans at low flow rates. This solution was arrived at through a combination of experimental testing and numerical simulation.