科研之友
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摘要
In place of the one-dimensional steady-state model assuming the transfer process along the direction of cloth thickness only, a more comprehensive theoretical treatment of coupled heat and moisture transfer process is proposed in this study on the multilayer-cloth for perspiration based infrared camouflage, capable of predicting multi-dimensional and transient processes, and illuminating the influence of the related variables and ambient fluid field. We used the CFD software Fluent with its user-defined functions to solve the governing equations and applied the model first to a simplified two-dimensional case with previous benchmark conditions. The results confirmed our earlier conclusion from the one-dimensional model that such a cloth structure can achieve the satisfactory effect of infrared camouflage, yet with much more details within the entire 2D simulation domain: 1) most of cloth outer surface bears the same temperature as the ambient, but the temperature is a little bit lower nearer the wind inlet due to the local higher latent heat loss; 2) the humidity gradually decreases horizontally from skin surface to the ambient, while vertically, along the wind blowing direction, the humidity first increases and then decreases. We then employed this model to compare the system behaviors between transient and steady conditions. Our predictions also demonstrated that changes in the ambient condition in terms of wind speed, ambient humidity and temperature will impact the distributions of temperature, humidity and heat loss in the cloth. This first imposes challenges to the idea of perspiration based infrared camouflage; it also implies nonetheless that such scheme is feasible over a certain range of ambient conditions. Our proposed cloth system thus provides a model analysis that reveals and tackles the complex human body cloth interactions.
- 出版日期2014-7
- 单位清华大学
