The performance requirements of the modern internal combustion engine have created increasingly large demands on the cooling system. Likewise, packaging of the engine and cooling system has required the development of compact high efficiency and performance cooling components. Much progress has been made to improve the performance of axial fan and heat exchanger technology, but the interaction between the fan and heat exchanger is often neglected. The problem is further enhanced when involving multiple fans, when coupling occurs not only between the fan and core flow, but also between the individual fans. To better understand the phenomena involved with coupling fans and heat exchangers, EMP has conducted a study of a heat exchanger system involving four 280-mm fans mounted to a core. The system was analyzed with Fluent 6.1 computational fluid dynamics (CFD) software, in both a pusher and puller configuration. The effects of increasing the stand-off distance between the fans and heat exchanger core were evaluated. The study revealed that the vorticity generated by the fans inside the shroud created significant interactions in the shroud flow, which reduced the overall efficiency of the system. EMP evaluated several variations of the base system to improve the shroud flow, including segregating the flow from the fans on the heat exchanger, implementing counter-rotating fans, and utilizing flow straighteners to direct the flow more smoothly through the core. Once an ideal fan configuration was determined, the performance of the base system and the "advanced" system were measured in a calorimeter test facility.
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