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Proceedings Paper

Dynamics of cryogen deposition relative to heat extraction rate during cryogen spray cooling
Author(s): Wim Verkruysse; Boris Majaron; Guillermo Aguilar; Lars Othar Svaasand; J. Stuart Nelson
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Paper Abstract

Goal is to investigate how delivery nozzle design influences the cooling rate of cryogen spray as used in skin laser treatments. Cryogen was sprayed through nozzles that consist of metal tubes with either a narrow or wide diameter and two different lengths. Fast-flashlamp photography showed that the wide nozzles, in particular the long wide one, produced a cryogen jet (very small spray cone angle) rather than a spray (cone angles of about 15 degrees or higher) and appeared to atomize the cryogen less finely than the narrow nozzles. We measured the cooling rate by spraying some cryogen on an epoxy-block with thermocouples embedded. The heat extraction rate of the wide nozzles was higher than that of the narrow nozzles. The results suggest that finely atomized droplets produced by the narrow nozzles do not have enough kinetic energy to break through a layer of liquid cryogen accumulated on the object, which may act as a thermal barrier and, thus, slow down heat extraction. Presumably, larger droplets or non- broken jets ensure a more violent impact on this layer and therefore ensure an enhanced thermal contact. The margin of error for the heat extraction estimate is analyzed when using the epoxy-block. We introduce a complementary method for estimating heat extraction rate of cryogen sprays.

Paper Details

Date Published: 17 May 2000
PDF: 12 pages
Proc. SPIE 3907, Lasers in Surgery: Advanced Characterization, Therapeutics, and Systems X, (17 May 2000); doi: 10.1117/12.386235
Show Author Affiliations
Wim Verkruysse, Beckman Laser Institute and Medical Clinic (United States)
Boris Majaron, Beckman Laser Institute and Medical Clinic and Jozef Stefan Institute (Slovenia)
Guillermo Aguilar, Beckman Laser Institute and Medical Clinic and Univ. of California/Irvine (United States)
Lars Othar Svaasand, Univ. of Trondheim (Norway)
J. Stuart Nelson, Beckman Laser Institute and Medical Clinic (United States)

Published in SPIE Proceedings Vol. 3907:
Lasers in Surgery: Advanced Characterization, Therapeutics, and Systems X
R. Rox Anderson; Kenton W. Gregory; Eugene A. Trowers; David S. Robinson; Kenneth Eugene Bartels; Lou Reinisch; Reza S. Malek; C. Gaelyn Garrett; Lloyd P. Tate; Hans-Dieter Reidenbach; Timothy A. Woodward; Kenneth Eugene Bartels; Lawrence S. Bass; George M. Peavy; C. Gaelyn Garrett; Kenton W. Gregory; Nikiforos Kollias; Harvey Lui; Reza S. Malek; George M. Peavy; Hans-Dieter Reidenbach; Lou Reinisch; David S. Robinson; Lloyd P. Tate; Eugene A. Trowers; Timothy A. Woodward, Editor(s)

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