Abstract
Comparing to continuous spray, intermittent spray is able to offer effective cooling by consuming less liquid. Targeting at relatively high-temperature applications, this study explores the influences of pulse duration and duty cycle (DC) in the cooling performance of the intermittent spray of a self-rewetting fluid, the 1.5% wt.% aqueous solution of 1-pentanol. Unlike water, using the self-rewetting fluid in intermittent spray is able to induce the inverse Marangoni convection which helps to replenish the hot spot with cool liquid even though the surface temperature exceeds 145°C. This leads to a further reduction in fluid consumption because comparable cooling rate can be delivered by spraying the self-rewetting fluid at a much lower frequency. Although dryout can still occur in the low DC regime, the inverse Marangoni convection is proven to sustain effective cooling during spray-off period in the high DC regime. As a result, cooling rate is nearly independent of DC in the high DC regime. For the self-rewetting fluid, cooling performance is not benefited from increasing the pulse duration as excess fluid simply drains out without contributing much to heat removal. Hence, a pulse duration of 1.5 s with a DC of 15% is recommended for the intermittent spray cooling of 1-pentanol/water mixtures at high wall superheats. Since the spray cooling efficiency of the self-rewetting fluid is always higher than that of water in this study, it opens up new possibility in spray quenching with more rapid cooling, better thermal uniformity, and further reduction in liquid consumption.
Published Version
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