Analysis of the thermal behavior of telephone switching cabinet

Telephone companies utilize densely packed electronics in outdoor metal cabinets to route calls between customers. Effective cooling of the electronics is of concern as operation at elevated temperatures can dramatically reduce the expected operational life span and cause unexpected interruption in service. A better understanding of the influence of the different factors which affect the transient thermal behavior of the cabinet will facilitate improved thermal management of the switching cabinets. To achieve this goal the switching cabinet is modeled using the lumped capacitance method.;The model predicts the transient temperatures of components of the enclosure such as the electronic equipment, air, batteries, and shell of the enclosure. The model also allows the use of one or more thermal sinks. The thermal capacitances of each of the major elements is determined using mass fractions. Transient energy balances for each element are developed creating a system of simultaneous differential equations which are solved at each time step using a fourth order Runge-Kutta method. The system model was compared with experimental measurements on an outdoor commercial telecommunications cabinet and it provided a good prediction of the temperature trends.;A search of the parameters which affect the thermal behavior of telephone switching cabinets was conducted. A sensitivity analysis was performed to determine which factors had a significant influence on the internal air temperature of the cabinet. The outdoor ambient air temperature is shown to be the dominant factor determining the peak inside air temperature of the cabinet. The important factors were non dimensionalized and parametric studies were conducted. Weighted relationships between the internal cabinet air temperature and the important dimensionless parameters were developed which predict peak operating temperatures and time to reach peak temperatures following a spike in electronic loading.;This research is important as it identifies the important factors affecting the thermal behavior of the outdoor telephone switching cabinet. It also provides correlations which simplify the general understanding of the transient thermal behavior of outdoor electronic cabinets.