Abstract
Cryogenic sprays are used for cooling human skin during laser dermatologic surgery. In this paper, six straight-tube nozzles are characterized by photographs of cryogenic spray shapes, as well as measurements of average droplet diameter, velocity, and temperature. A single-droplet evaporation model to predict average spray droplet diameter and temperature is tested using the experimental data presented here. The results show two distinct spray patterns--sprays for 1.4-mm-diameter nozzles (wide nozzles) show significantly larger average droplet diameters and higher temperatures as a function of distance from the nozzle compared with those for 0.5-0.8-mm-diameter nozzles (narrow nozzles). These results complement and support previously reported studies, indicating that wide nozzles induce more efficient heat extraction than the narrow nozzles.
Highlights
L ASER treatment of hypervascular skin lesions, such as port wine stain birthmarks, is the clinical application of interest in this work, and several papers summarize the progress to date [1]–[3]
The initial values used in the model for V are 80, 60, 30, and 15 m/s for SW, LW, SN, and LN, respectively; and for D are 25 and 14 m for wide and narrow nozzles, respectively
0.01, demonstrating that the difference in of these two spray groups is statistically significant at a 95% level. These measurements confirm the existence of two atomization patterns, as suggested above: larger droplet diameters (10–15 m) produced by the wide nozzles, and smaller droplet diameters (2–6 m), produced by the narrow nozzles
Summary
L ASER treatment of hypervascular skin lesions, such as port wine stain birthmarks, is the clinical application of interest in this work, and several papers summarize the progress to date [1]–[3]. To remove these lesions, patients are treated with laser pulses that induce permanent thermal damage to targeted blood vessels, typically located 200–550 m below the skin surface. E. Karapetian is with the Beckman Laser Institute, University of California, Irvine, CA 92612 USA, and with the Department of Chemical Engineering and Material Sciences, University of California, Irvine, CA 92697 USA. Our experimental results are discussed in the context of those obtained during recent studies aimed at measuring the heat extraction from skin during CSC [12]–[14]
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