Integrated thermal analysis of indirect air-cooled electronic chassis

Steady conjugate heat transfer in an air filled electronic chassis, which is indirectly cooled by forced air along its top and bottom walls, is investigated numerically. Four printed circuit boards (PCB's), vertically located in the chassis, form five separate air compartments for natural convection to take place. Along the top and bottom walls of the chassis, cooling air, flowing inside finned channel passages, removes the heat generated by the PCBs. The effects of temperature distributions on the top and bottom walls of the chassis on the PCB temperature field are of prime interest here. The integrated system and board level modeling is done using a two-step process. First, a simplified computational model is developed for the finned channel, which calculates the nonuniform temperature distributions on the top and bottom walls of the chassis. By applying the calculated top and bottom wall temperature distributions as boundary conditions, a three-dimensional (3-D) numerical study is next performed using control volume based finite volume scheme to calculate the detailed temperature fields. This model considers the conduction within the PCBs, as well as the natural convection within the adjacent air. To elucidate the importance of an integrated system and board level analysis, the results are compared with those for conventional constant wall temperature boundary conditions on the chassis top and bottom walls.