Coping with very high heat loads in electronic telephone systems of the future

It is shown that in large buildings used by the Bell Regional Companies, conventional and modular cooling systems can handle up to about 1500 W for 2100 mm-high, 660 mm-wide frames, 2200 W/m² of floor space. This is for occupied spaces in which indoor air temperature is to be kept below 38°C long term and 40°C short term. For unoccupied spaces somewhat higher heat loads could be handled with the use of high-velocity air in closed cabinets. Above 2200 W/m² and certainly above 5400 W/m² heat dissipation, it is argued that designers should consider the use of water or some other high-heat-capacity cooling fluid instead of air. Smaller buildings do not normally utilize ducting or ceiling plenums, and are thus limited to around 430 W/m² of floor space. If ducts or plenums to allow more air flow past or through the equipment frames were used, the same heat dissipation levels as are feasible in large buildings could be achieved. For outdoor cabinets, some increase in heat dissipation beyond existing AT&T designs could be accomplished through passive measures such as shading, use of fins, and improved reflecting paints