TAILIEUCHUNG - Heat Transfer Handbook part 101

Heat Transfer Handbook part 101. The Heat Transfer Handbook provides succinct hard data, formulas, and specifications for the critical aspects of heat transfer, offering a reliable, hands-on resource for solving day-to-day issues across a variety of applications. | 996 HEAT TRANSFER IN ELECTRONIC EQUIPMENT rates across a large substrate or PCB with an appropriately configured distribution plate or nozzle array and the freedom to tailor the jet flow to the local cooling requirements have made impingement cooling one of the most promising alternatives for hie cooiing of high-heat-flux components. Impingement cooling may involve a single jet or multiple jess directed at a ngg le component or an array of electronic components. Circular orifices slot-shaped orifices or nozzles of various cross sections may form the jets. The axis of the impinging jet may be perpendicular or inclined to the surface of the component. Moreover in the application of liquid jets a distinction can be made between free jets which are surrounded by ambient air and submerged jets for which the volume surrounding the jet is filled with the working liquid. Whereas heat transfer associated with gas jets has been the subject of active research since the midt1950s jet impingement cooling with dielectric liquids is a far more recent development. Many of the pioneering studies in this field were reviewed by Bergles and Bar-Cohen 1990 . More recent studies of heat transfer to free jets of dielectric liquids have been performed by Stevens and Webb 1989 Nonn et al. 1988 and Wang et al. 1990 . Womac et al. 1990 examined free as well as submerged liquid jets while submerged jet impingement beat transfer was the subject of the investigations by Wadsworth and Mudawar 1990 and Mudawarand Wadsworth 1990 . As a final distinction jet impingement cooling of electronic components may involve forced convection alone orlocalized flow boiling with orwithout net vapor generation. The discussion in this section is limited to single-phase forced convection. Correlation Despite the complex behavior of the local heat transfer coefficient resulting from parametric variations in the impinging jet flow it has been found possible to correlate the average heat transfer coefficient

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