Jaiswal Ankush K, Jose Cibin T, Ramesh Rajesh, Nanani Vinay K, Sadeghi Kambiz, Joshi Ankit, Kompally Krishna, Pathikonda Gokul, Emady Heather N, Bheda Bhaumik, Kavouras Stavros A, Rykaczewski Konrad
School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, AZ, USA.
Julie Ann Wrigley Global Futures Laboratory, Arizona State University, Tempe, AZ 85287, USA.
iScience. 2024 Jun 17;27(7):110304. doi: 10.1016/j.isci.2024.110304. eCollection 2024 Jul 19.
Sweat evaporation is critical to human thermoregulation, but current understanding of the process on 20 μm to 2 cm scale is limited. To this end, we introduce a wind-tunnel-shaped ventilated capsule with an infrared window for simultaneous infrared sweat imaging and evaporation rate measurement. Implementing the capsule in pilot human subject tests suggests that the common assumption of sweat being an isothermal film is only valid when the evaporation rate is low and sweat forms puddles on the skin. Before transitioning to this filmwise mode, sweating occurs in cyclic dropwise mode, displaying a 3x higher mass transfer coefficient in the same conditions. Imaging highlighted distinct phenomena occurring during and between these modes including out-of-duct evaporation, pulsating droplets, temporary and eventually lasting crevice filling, and individual drop-to-film spreading. In all, sweat evaporation is an impactful area that our results show is ripe for exploration, which can be achieved quantitatively using the introduced platform.
汗液蒸发对人体体温调节至关重要，但目前对20微米至2厘米尺度上该过程的理解有限。为此，我们推出了一种带有红外窗口的风洞形通风胶囊，用于同时进行红外汗液成像和蒸发速率测量。在人体受试者的初步测试中使用该胶囊表明，汗液为等温薄膜这一常见假设仅在蒸发速率较低且汗液在皮肤上形成水坑时才成立。在转变为这种膜状模式之前，出汗以周期性的滴状模式发生，在相同条件下显示出高3倍的传质系数。成像突出显示了在这些模式期间和模式之间发生的不同现象，包括管外蒸发、脉动液滴、临时和最终持久的缝隙填充以及单个液滴到薄膜的铺展。总之，汗液蒸发是一个有重要影响的领域，我们的结果表明该领域亟待探索，利用所引入的平台可以对其进行定量研究。
