INTEGRATED THERMAL-ANALYSIS OF INDIRECT AIR-COOLED ELECTRONIC CHASSIS

Steady conjugate heat transfer in an air filled electronic chassis, wh ich is indirectly cooled by forced air along its top and bottom walls, is investigated numerically. Four printed circuit boards (PCB's), ver tically located in the chassis, form five separate air compartments fo r natural convection to take place. Along the top and bottom waifs of the chassis, cooling air, flowing inside finned channel passages, remo ves the heat generated by the PCB's. The effects of temperature distri butions on the top and bottom walls of the chassis on the PCB temperat ure field are of prime interest here. The integrated system and board level modeling is done using a two-step process. First, a simplified c omputational model is developed for the finned channel, which calculat es the nonuniform temperature distributions on the top and bottom wall s of the chassis. By applying the calculated top and bottom wall tempe rature distributions as boundary conditions, a three-dimensional (3-D) numerical study is next performed using control volume based finite v olume scheme to calculate the detailed temperature fields. This model considers the conduction within the PCB's, as well as the natural conv ection within the adjacent air. To elucidate the importance of an inte grated system and board level analysis, the results are compared with those for conventional constant wall temperature boundary conditions o n the chassis top and bottom walls.