Heat transfer in electronic systems with emphasis on asymmetric heating

The trend in electronic circuit design is toward increasing power dissipation density. The performance and reliability of increasing number of electronic systems are now seriously threatened by thermal effects, so that it is necessary to reappraise the relevant thermal design procedures. This paper examines natural convection cooling and concerns the prediction of maximum temperatures of electronic cabinets containing arrays of vertically oriented circuit cards with unequal power dissipation levels. By means of a vertical channel model, the effects of channel spacing, channel height, and power dissipation level are assessed with emphasis on asymmetric powering of the channel walls. Methods are indicated for rapid evaluation of maximum temperatures and optimum channel spacing with asymmetric heating. The present results show that asymmetry reduces the thermal performance of the channel. Consequently, the power dissipation on the channel walls should be made nearly equal.