Two-phase cooling characteristics of mono-dispersed droplets impacted on an upward-facing heated disk

• Published in: Experimental thermal and fluid science 2013-01, Vol.44, p.312-322
• Main Authors: Mahmoudi, Seyed Reza, Adamiak, Kazimierz, Peter Castle, G.S.
• Format: Article
• Language: English
• Subjects: Applied sciences; Capillaries; Cooling; Correlation; Critical heat flux; Droplet cooling; Droplets; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Heat flux; Heat transfer; Impact velocity; Strouhal number; Theoretical studies. Data and constants. Metering; Weber number
• ISSN: 0894-1777; 1879-2286
• DOI: 10.1016/j.expthermflusci.2012.07.003

► Boiling characteristics of impacting droplets over a heated disk were studied. ► Two regimes of droplet impact were identified based on the range of Weber numbers. ► At lower Weber numbers, the resulting films are hydrodynamically stable. ► CHF showed significant enhancement due to the film stability at low Weber numbers. ► Two different CHF correlations for two regimes of impact were proposed. Droplet impact cooling has been shown to be a promising method for high heat flux removal applications. Recent experimental studies have revealed that even higher heat transfer at low mass fluxes and low Weber number can be achieved with only few degrees of superheat. In the present work, mono-dispersed droplet cooling of a horizontal upward facing heated surface was investigated at low Weber numbers. The impact velocity and frequency of free falling stream of droplets were varied through changing the gap between the heated surface and tip of different capillaries, and by variation of the volumetric flow rate (0.5–4.8cc/min). The impact velocity and droplet frequency were varied between 0.28–1.3m/s and 0.5–5 Hz, respectively, using four different capillaries sized between 17g and 22g. The coolant was 25°C deionized water and all the experiments were performed at atmospheric pressure. The time-averaged two-phase characteristic curves were obtained up to the Critical Heat Flux (CHF) regime. Through the extensive set of experiments, two separate correlations are proposed to predict the average CHFs based on the Weber in the range between 3–10 and 10–100, and Strouhal number ranged in the range between 6.35×10−3 and 3.88×10−2 and 1.81×10−3 and 3.86×10−2, respectively. The correlation predicts the average CHFs in both regions with absolute errors less than 20% and 25%, respectively.