The present study deals with an experimental and numerical study to quantify the skin necrosis during cryotherapy. Agarose gel (0.6% (w/v)) is used to mimic the thermal properties of the dermis. The spray cooling is performed with 0.8 mm, 0.6 mm and 0.4 mm nozzle diameters for a single freeze-thaw cycle of 120 s freezing and 130 s thawing. The distance from the nozzle to the gel surface (z) is maintained at 9 mm, 18 mm and 27 mm. The numerical modelling for the thermal analysis has been performed with enthalpy equation; the numerical results are well matched with the experimental results. The numerical results are used to calculate the lethal front, ablation volume and gap (distance between lethal and ice front) in the gel. The ablation volume obtained with 0.8 mm nozzle diameter for − 50^oC and − 25^oC isothermal surfaces is 83% and 62% smaller than the ice volume respectively for all the spraying distance. Similarly, it is 93% and 78% smaller for z = 27 mm while it is 91% and 73 ± 2% respectively for z = 18 mm and 9 mm in the case of 0.6 mm nozzle diameter. The present numerical model may help in the computerised planning of cryotherapy.

本研究涉及一项实验和数值研究，以量化冷冻治疗期间的皮肤坏死。琼脂糖凝胶（0.6％（w / v））用于模拟真皮的热学性质。喷雾冷却的喷嘴直径为0.8 mm，0.6 mm和0.4 mm，以进行120 s冻结和130 s解冻的单个冻融循环。从喷嘴到凝胶表面（z）的距离保持在9mm，18mm和27mm。用焓方程进行了热分析的数值模拟。数值结果与实验结果吻合良好。数值结果用于计算凝胶中的致命锋，消融量和间隙（致命锋与冰锋之间的距离）。在− 50 ^o C时，喷嘴直径为0.8 mm时获得的消融体积在整个喷射距离内，-25 ^o C等温表面分别比冰量小83％和62％。类似地，在喷嘴直径为0.6 mm的情况下，z = 27 mm时分别减小93％和78％，而z = 18 mm和9 mm时分别减小91％和73±2％。本数值模型可以帮助进行冷冻治疗的计算机化计划。