Collaborative Research: Understanding Laser-Assisted Surface Cooling Enhancement (LASCE)

CBET-1403508/1402587 Aguar/Trujillo这笔赠款为研究和开发一种非侵入性方法提供资金，以增强目标表面和冷却液之间的局部热传递。这种方法利用了热空化气泡，当连续波(CW)激光在高吸收液体薄膜中适当聚焦时形成热空化气泡。这些气泡在微秒内形成并破裂，有力地搅动液体并加强传热。这种现象被称为激光辅助表面冷却强化(LASCE)。PI的初步估计表明，传热强化与相变(蒸发/沸腾)一样大，后者是目前液体冷却系统的上限。LASCE也可以达到或超过使用微改性结构获得的性能，但不实施任何类型的表面改性。此外，连续波激光器通常是不太复杂的激光介质，比脉冲激光更便宜、更简单，而且只需通过调制输出功率就可以控制气泡形成的频率。因此，该项目的潜在影响在于控制地表热量的新方法。这项研究包括加州大学河滨分校和威斯康星大学麦迪逊分校之间的合作实验和计算研究，旨在研究和量化：1)引起热空化的热输入和增强对流产生的冷却之间的平衡；2)所产生的流体流动对激光操作参数的敏感性；3)多个空化事件之间的相互作用及其对增强对流冷却的影响的物理学。基于高精度的数值模拟和详细的测量技术，将寻求对支撑最理想的热传递条件的物理基础的彻底检查，这对于优化LASCE的运行至关重要。紧随其后的是一个同样重要的目标，旨在探索LACSE是否适用于不可能进行表面修改的应用，例如在UCR开发的一种新型透明颅骨植入物(“大脑之窗”)上进行激光治疗时的皮肤(头皮)冷却。该项目的成功将为光学热空化的许多变革性应用打开大门，旨在降低NOx和颗粒物排放的低温燃烧策略，以提高发动机效率，以及为不同的生物医学应用提供经皮给药。

CBET-1403508/1402587Aguilar/TrujilloThis grant provides funding for studying and developing a non-intrusive method to enhance local heat transfer between a target surface and a cooling fluid. The approach takes advantage of thermocavitation bubbles, which are formed when continuous wave (CW) laser light is properly focused within highly-absorbing liquid thin films. These bubbles form and collapse within microseconds, vigorously agitating the liquid and enhancing heat transfer. This phenomenon is called Laser-Assisted Surface Cooling Enhancement (LASCE). The PI's preliminary estimates show that heat transfer enhancement is as great as that of phase change (evaporation/boiling), which is the current upper limit to liquid-based cooling systems. LASCE may also match or exceed the performance obtained using micro-modified structures, but without implementing any type of surface modification. Also, CW lasers are often less complex lasing media, cheaper and simpler than pulse lasers, and can control the frequency of bubble formation simply by modulating their output power. The potential impact of this project, therefore, is in novel ways of controlling surface heat. This has implications for systems ranging from laser surgery to combustion engine devices.This study encompasses collaborative experimental and computational research between University of California-Riverside and University of Wisconsin-Madison aimed at studying and quantifying the: 1) balance between the heat input to induce thermal cavitation and the cooling produced by enhanced convection; 2) sensitivity of the resulting fluid flow to the operating parameters of the laser and; 3) physics of interaction between multiple cavitation events and its effect on enhanced convective cooling. Based on highly accurate numerical simulations and detailed measurement techniques, a thorough examination of the physics underpinning the most desirable heat transfer conditions will be sought, which is essential in optimizing the operation of LASCE. This will be followed by an equally important objective, which aims to explore LACSE's suitability for applications where surface modification is impossible, such as skin (scalp) cooling during laser therapy across a novel transparent cranial implant ("Window to the Brain") developed at UCR. The success of this project will open the door to many transformative applications of optical thermocavitation aimed at low-temperature combustion strategies for mitigating the levels of NOx and particulate matter emissions to improve engine efficiency as well as transdermal drug delivery for diverse biomedical applications.