Showing papers on "Electronics cooling published in 1989"

Noise control on computer and business equipment using speed controlled blowers

Abstract: The authors present a method to reduce the noise level of computer and business equipment by the implementation of temperature-controlled variable-speed blowers. The possibility for reducing the noise emission is given by the fact that today's cooling design is mostly based on worst-case environmental conditions (maximum temperature and altitude above sea level) to cover the wide variety of the products' worldwide installations. The potential acoustical benefits of adaptive cooling are significant and would be extremely expensive to attain using conventional path noise-control methods such as mufflers or enclosures. However, it should not be overlooked that the price paid for lower noise levels, in addition to the cost of the controller (which is in most cases balanced by the removal of acoustical treatments), is a possible effect on the reliability of the electronics, since their cooling is no longer overdesigned. >

A system comparison between water and air-borne cooling systems for telephone exchanges

Abstract: The authors compare three cooling systems (two airborne and one waterborne) for telephone exchanges: (1) cooling through a false floor; (2) conventional air conditioning; and (2) cooling with natural convection coils, for instance using the Ericsson cooling system ERICOOL. The waterborne natural-convection system appears to be the most advantageous. The system has the following advantages: lowest power consumption; easiest achievement of cooling reserve in case of main failure; best working environment in the switching room; greatest development potential for future electronic packaging structures with increased power densities. >

Uniform air-flow cooling for high power crates

Abstract: In the course of developing circuits requiring wide dynamic range, low noise, and high precision, the authors needed to know how well they could control ambient temperatures. They built a standard cooling unit that provides reasonably uniform air flow with relatively high air speed. Other data were included that were obtained during the R&D research and development work for the unit. It was found that the uniformity of the cooling air flow should be expected to be worse than 30% and the gradient of the air velocity to be worse than 1.6 (m/s)/2 cm. It was concluded that a cooling system should be attached if each module consumes significantly more than 30 W. >

How mechanical engineering issues affect avionics design

Abstract: Environmental questions that involve temperature and heat dissipation in connection with avionics are discussed. The authors describe recent work on (a) passive (no machinery to move coolant) cooling techniques allowing deletion of active (machinery powered) cooling systems, and (b) studies to ascertain the effect of temperature on reliability. It is shown that passive cooling techniques can produce temperatures approximately equivalent to those of active cooling, and that heat-transfer-enhancement techniques can extend the application of passive cooling. In addition, it is noted that active cooling can incur high prices beyond the immediately visible costs of the active cooling systems alone. The influence of temperature as a failure accelerator in moderate temperature ranges cannot be readily confirmed. Passive cooling minimizes the interface definition for application of electronic equipment, thus simplifying use of a box in multiple applications. >