Effect of skin indentation on heat transfer during cryogen spray cooling

Abstract

Flat surfaces produce the most efficient heat transfer, but once indentation exists (as it does in all clinically relevant cases), larger indentations produce a higher maximum heat flux. This suggests that higher momentum sprays (which produce larger skin indentations for identical spurts) than those in current clinical use may improve CSC efficiency.

Effects of relative humidity on laser light transmittance during cryogen spray cooling of in vitro skin phantoms

“…In summary, these experimental observations suggest that the refractive index variation of flying droplets as a function of temperature, along with the droplets that travel toward and bounce off the substrate surface, the formation of a cryogen layer 15 and the water that condenses/freezes around the cryogen cone spray and layer 16 form a dynamic cloud that is highly dispersive.…”

“…While the transmittance reduction due to the dispersive cloud of cryogen droplets in-flight and of those that bounce off the substrate surface, as well as the formation of a cryogen layer and condensed/frozen water on the sprayed surface may be present regardless of the sprayed object, we believe that the larger transmittance reduction for the agar phantom compared to that of the glass slide is due to addition of two other dispersive sources: (1) enhanced accumulation of cryogen by indentation and (2) freezing of internal water. Cryogen accumulation was first reported by Basinger et al 15 , who studied the effect of skin indentation on heat transfer during CSC application. According to this study, the indentation generated by the impingement of cryogen on a gel (polyacrylamide) phantom causes cryogen accumulation and, therefore, thicker cryogen layers as compared with rigid phantoms.…”

Numerical Prediction of the Intracellular ICE Formation Zone during Cryosurgery on a Nodular Basal Cell Carcinoma Using Liquid Nitrogen Spray

“…This was later confirmed also by Franco et al [163] in terms of the uniformity in the protection these sprays could provide when used in conjunction with laser irradiation. Nevertheless, the reader must not forget that non-uniformities in the heat transfer coefficient over the entire spray area exist and depend on the following parameters: geometric parameters such as nozzle diameter-length [164], nozzle-to-skin distance [165] and nozzle angle [162], cryogen spurt duration [166][167][168][169][170][171][172][173], ambient pressure [174][175][176], humidity and frost formation effects [177][178][179][180], skin indentation effects [181,182], and the dynamics of cryogen spray deposition, such as cryogenic spray shape, the droplet velocity and diameter [183]. 3.…”

Inertia dominated flow and heat transfer in liquid drop spreading on a hot substrate

“…Clinical observations suggest that the skin indents due to momentum of cryogenic spray. In Basinger et al (2004) it was shown that one can improve the maximum heat flux and cooling efficiency by physically increasing the size of indentation, which can be achieved by nozzles producing higher momentum.…”