Spray impingement cooling with single- and multiple-nozzle arrays. Part II: Visualization and empirical models

The performance of single- and multiple-nozzle sprays for high heat flux electronics cooling using nitrogen-saturated FC-72 was studied in a multi-chip module (MCM) test setup, similar to MCM’s used in current high-end computer systems. An additional facility was constructed for visualization of the sprays and heat transfer behavior using clear heating elements coated with an indium tin 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 droplet impact region, a two-phase liquid film boiling component in the corners away from this region, and, for the multiple-nozzle sprays, a single-phase drainage flow component. Empirical models were generated based on this conceptual model, and the correlations predict the data to within about 6%. 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 about 12% for both single- and four-nozzle arrays.