Abstract:

With the rapid development of laser dermatology, the epidermis cooling technology becomes more and more important, and it is of great potential for commercial application. Cryogen spray cooling (CSC) with several tens of milliseconds has been successfully applied in laser treatment of vascular diseases, which can protect epidermis from the thermal injuries due to the absorption of melanin and hence increase the incident laser energy, leading to the improvement in therapeutic outcomes. CSC involves flashing atomization and boiling heat transfer on cooling surface. The majority of previous studies were conducted experimentally. The research progresses of the mechanism of flashing atomization, spray characteristics, heat transfer dynamics and the enhancement were summarized for the past 20 years. The typical research methods and results were compared and analyzed, and the different factors to influence the heat transfer dynamics of CSC were investigated. New spray techniques, such as using lower point cryogens and hypobaric pressure method, are effective to enhance cooling capacity. Finally, the remaining difficulties in this field were clarified and the potentials of the ongoing research were pointed out.

Key words: cryogen flashing spray cooling, laser dermatology, heat transfer, gas-liquid two-phase flow, biomedical engineering

摘要：

随着皮肤激光医学的高速发展，与之配合的表皮冷却技术日益重要，具有极大的市场应用前景。制冷剂瞬态闪蒸喷雾冷却（CSC）已经成为激光治疗血管性皮肤病的重要辅助冷却手段，可以有效减小黑色素吸收激光能量导致的表皮热损伤，从而提高入射激光能量、改善治疗效果。CSC涉及到低沸点高挥发性介质的闪蒸雾化、冷却表面沸腾相变传热等多相流与传热复杂科学问题，已有研究大部分是以实验的方式进行。本文从闪蒸喷雾机理、闪蒸喷雾特性、表面动态传热规律与传热强化4个方面对CSC在近二十年的研究进展进行综述，对比分析了典型研究方法与研究结果，并对其影响因素进行了探讨，使用更低沸点的新制冷剂与背压/距离耦合的喷雾新技术可以极大提高冷却能力。最后，指出了当前研究的难点以及后续研究方向。

关键词: 制冷剂闪蒸喷雾冷却, 激光皮肤医学, 传热, 气液两相流, 生物医学工程