AbstractWe describe forced air cooling, based on two new concepts, for CPU modules with high heat dissipation. The first concept is a slit jet flow system, and the second is an impingement duct flow system. These systems are designed for electronic equipment with multiple circuit boards (CPU modules), on which the CPUs have high heat dissipation and the SRAMs have low heat dissipation, loaded in three dimensions and in parallel. The slit jet flow system is very simple compared with the impingement jet flow system, which has a complicated comb‐style impingement jet. The slit jet system includes an air duct with slit orifices and an axial fan upstream from the circuit boards. The impingement duct system consists of an air duct and a heat sink with a fan, which is attached to the CPU. This system also has slit orifices and an axial fan upstream or downstream from the circuit boards. For electronic equipment with each of these flow systems installed, the increases in external thermal resistance for the CPU and SRAMs were measured after stopping one of the cooling fans or the CPU's micro cooling fan. The results showed that the slit jet and impingement duct flow systems provide good cooling performance and redundancy. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(3): 226–236, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10031