Purpose

The purpose of this paper is to study heat and steam transfer in a vertical air gap and improve thermal protective performance of protective clothing under thermal radiation and hot steam.

Design/methodology/approach

An experiment-based model was introduced to analyze heat and moisture transfer in the vertical air gap between the protective clothing and human body. A developed test apparatus was used to simulate different air gap sizes (3, 6, 9, 12, 15, 18, 21 and 24 mm). The protective clothing with different air gap sizes was subjected to dry and wet heat exposures.

Findings

The increase of the air gap size reduced the heat and moisture transfer from the protective clothing to the skin surface under both heat exposures. The minimum air gap size for the initiation of natural convection in the dry heat exposure was between 6 and 9 mm, while the air gap size for the occurrence of natural convection was increased in the wet heat exposure. In addition, the steam mass flux presented a sharp decrease with the rising of the air gap size, followed by a stable state, mainly depending on the molecular diffusion and the convection mass transfer.

Originality/value

This research provides a better understanding of the optimum air gap under the protective clothing, which contributes to the design of optimum air gap size that provided higher thermal protection against dry and wet heat exposures.

中文翻译：

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干湿热暴露防护服下垂直气隙热湿传递实验研究

目的

本文的目的是研究垂直气隙中的热量和蒸汽传递，提高防护服在热辐射和热蒸汽下的热防护性能。

设计/方法/方法

引入了基于实验的模型来分析防护服与人体之间的垂直空气间隙中的热量和水分传递。开发的测试设备用于模拟不同的气隙尺寸（3、6、9、12、15、18、21 和 24 毫米）。具有不同气隙尺寸的防护服经受干湿热暴露。

发现

气隙尺寸的增加减少了在两种热暴露下从防护服到皮肤表面的热量和水分传递。在干热暴露中引发自然对流的最小气隙大小在 6 到 9 mm 之间，而在湿热暴露中自然对流发生的气隙大小增加。此外，蒸汽质量通量随着气隙尺寸的增大呈现急剧下降，随后趋于稳定状态，主要取决于分子扩散和对流传质。

原创性/价值

这项研究提供了对防护服下的最佳气隙的更好理解，这有助于设计最佳气隙尺寸，从而为干湿热暴露提供更高的热保护。