Purpose

The present study aims to investigate the inverse-thermocapillary effect in an evaporating thin liquid film of self-rewetting fluid, which is a dilute aqueous solution (DAS) of long-chain alcohol.

Design/methodology/approach

A long-wave evolution model modified for self-rewetting fluids is used to study the inverse thermocapillary characteristics of an evaporating thin liquid film. The flow attributed to the inverse thermocapillary action is manifested through the streamline plots and the evaporative heat transfer characteristics are quantified and analyzed.

Findings

The thermocapillary flow induced by the negative surface tension gradient drives the liquid from a low-surface-tension (high temperature) region to a high-surface-tension (low temperature) region, retarding the liquid circulation and the evaporation strength. The positive surface tension gradients of self-rewetting fluids induce inverse-thermocapillary flow. The results of different working fluids, namely, water, heptanol and DAS of heptanol, are examined and compared. The thermocapillary characteristic of a working fluid is significantly affected by the sign of the surface tension gradient and the inverse effect is profound at a high excess temperature. The inverse thermocapillary effect significantly enhances evaporation rates.

Originality/value

The current investigation on the inverse thermocapillary effect in a self-rewetting evaporating thin film liquid has not been attempted previously. This study provides insights on the hydrodynamic and thermal characteristics of thermocapillary evaporation of self-rewetting liquid, which give rise to significant thermal enhancement of the microscale phase-change heat transfer devices.

中文翻译：

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自润湿液体薄膜中的逆毛细血管逆蒸发

目的

本研究旨在研究自润湿液体的蒸发薄膜液中的逆毛细血管逆作用，后者是长链醇的稀水溶液（DAS）。

设计/方法/方法

修改后的自润湿液体的长波演化模型用于研究蒸发的液态薄膜的逆热毛细特性。通过流线图显示归因于热毛细作用反向的流动，并对蒸发传热特性进行定量和分析。

发现

由负表面张力梯度引起的热毛细管流将液体从低表面张力（高温）区域驱动到高表面张力（低温）区域，从而阻碍了液体循环和蒸发强度。自润湿液体的正表面张力梯度会引起热毛细血管逆流。检查并比较了不同工作流体（水，庚醇和庚醇的DAS）的结果。表面张力梯度的符号显着影响工作流体的热毛细特性，并且在高的过高温度下，相反的作用非常明显。逆热毛细管效应显着提高了蒸发速率。

创意/价值

以前从未尝试过对自粘性蒸发薄膜液体中的逆热毛细管效应的研究。这项研究提供了有关自润湿液体热毛细管蒸发的流体动力学和热学特性的见解，这些特性使微米级相变传热装置显着提高了热效率。