The performance of single- and four-nozzle spays for high heat flux electronics cooling using nitrogen-saturated FC-72 was evaluated in this study. The testing was performed using a multichip module (MCM) test setup, similar to MCM’s used in current high-end computer systems. The MCM contained eight test chips; four of these were cooled by single-nozzle sprays and four by four-nozzle sprays simultaneously. The swirl-atomizing, full-cone spray nozzles were incorporated into a production spray plate and were positioned about 6 mm above the test chips. An additional facility was constructed for visualization of the sprays and heat transfer behavior using clear heating elements coated with an indium titanium oxide (ITO) film. Using both the heat transfer and visualization data, it was determined that the heat transfer could be broken down into two or three components: a dominant single-phase component in and around the spray impact, a two-phase liquid film boiling component in the corners away from the spray impact, and, for the multiple-nozzle sprays, a single-phase drainage flow component. Multi-part empirical models were generated based on this conceptual model, and the correlations predict the data to within 5%. In addition, a phenomenological critical heat flux (CHF) model was generated based on previous work with thin liquid-film boiling that suggests CHF in thin films occurs due to a homogeneous nucleation mechanism. This model predicts the current data to within 12% for both single- and four-nozzle arrays.

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