AN EXPERIMENTAL-STUDY OF THE GROWTH OF BREATH FIGURES
AN EXPERIMENTAL-STUDY OF THE GROWTH OF BREATH FIGURES
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DOI：
10.1016/0166-6622(91)80126-9
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发表时间：
1991-05-01
期刊：
影响因子：
--
通讯作者：
GALVIN, KP
中科院分区：
文献类型：
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作者：
BRISCOE, BJ;GALVIN, KP
本文介绍了一种实验研究的方式，其中系统的液滴（呼吸数字）的演变过程中的水蒸气冷凝在聚乙烯薄膜。 假设接触角滞后可以忽略，观察到的现象与冷凝物-基材接触角无关。 它表明，通过使用两个实验系统，液滴可以根据两个根本不同的生长规律，这是一个功能，这是过去的研究之间的一个明显的异常的原因。 尽管在生长方面存在显著差异，但发现两组结果与Vincent [R.A. Vincent，Proc. R. Soc.伦敦，A辑，321（1971）53.]液滴的无聚结生长速率以dD/dt = kappa-D-β的形式表示，其中D是液滴直径，β是常数。 在凝结开始时，液滴相对孤立，这发生在合并增长的重要时期，其特征在于第一制度。 第二种状态的特征是聚结对液滴生长影响最大的时期。 在第一个实验系统中，液滴的增长受到潜热消散速率的限制。 在这种情况下，kappa是常数，并且在第一和第二方案期间，液滴的平均直径缩放为D（m）几乎等于t1/（1+beta）。 beta值约为0.49。 在第二个实验系统中，潜热很容易消散，因此系统按照恒定的冷凝蒸汽流量发展。 参数kappa随时间变化。 结果是，液滴的平均直径在第一状态期间按比例缩放为D（m）几乎等于t1/3，并且在第二状态期间按比例缩放为D（m）几乎等于t。
This paper describes an experimental study of the way in which a system of droplets (breath figures) evolves during the condensation of water vapour on a polyethylene film. The phenomenology observed is independent of the condensate-substrate contact angle assuming contact angle hysteresis is negligible. It is demonstrated, through the use of two experimental systems, that the droplets can grow according to two fundamentally different growth laws, a feature which has been the cause of an apparent anomaly between past studies. Despite the significant difference in the growth, both sets of results were found to be in good agreement with an empirical equation proposed by Vincent [R.A. Vincent, Proc. R. Soc. London, Ser. A, 321 (1971) 53.] which describes the time independent evolution of the process.The coalescence-free growth rate of the droplets was expressed in the form, dD/dt = kappa-D-beta where D is the droplet diameter and beta is a constant. The important period of coalescence growth, which occurs at the start of the condensation when the droplets are relatively isolated, characterises the first regime. The second regime is characterised by the period when coalescence has its maximum influence on the droplet growth. In the first experimental system the growth of the droplets was limited by the rate at which the latent heat could be dissipated. In this case kappa was a constant and the mean diameter of the droplets scaled as D(m) almost-equal-to t1/(1+beta) during both the first and second regimes. The value of beta was approximately 0.49. In the second experimental system the latent heat was easily dissipated and hence the system evolved according to a constant flux of condensing vapour. The parameter kappa varied with time accordingly. The result was that the mean diameter of the droplets scaled as D(m) almost-equal-to t1/3 during the first regime and scaled as D(m) almost-equal-to t during the second regime.