Sublimation rate and the mass-transfer coefficient for snow sublimation
Sublimation rate and the mass-transfer coefficient for snow sublimation
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DOI：
10.1016/j.ijheatmasstransfer.2008.06.003
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发表时间：
2009-01-15
影响因子：
5.2
通讯作者：
Perron, Frank
中科院分区：
文献类型：
--
作者：
Neumann, Thomas A.;Albert, Mary R.;Perron, Frank
雪的升华是影响雪晶体结构的基本过程，对冰芯解译、遥感、雪水文学和雪中化学过程等都有重要意义。先前的研究已经使用现场数据从能量、同位素或质量平衡计算中推断出升华速率。因此，这些研究无法控制许多决定升华速率的环境参数（例如温度，相对湿度，雪的微观结构）。我们在实验室中对雪样进行了升华率测量，同时控制了许多参数。结果表明，在测量精度范围内，在很宽的样品温度和空气流速范围内，离开雪样品的空气流通常是饱和的。这一结果支持了对单个冰粒的理论研究，该研究发现在升华过程中没有能量障碍需要克服，并表明雪的升华受到蒸气扩散到孔隙空间的限制，而不是在晶面升华。在空气流速相对较高的大孔隙空间（即表面或深度灰白层）中可能存在欠饱和。我们使用这些数据来放置边界的质量传递系数雪作为雷诺数的线性函数，并发现，h（m）= 0.566 Re + 0.075。(c)2008爱思唯尔有限公司保留所有权利。
Sublimation of snow is a fundamental process that affects the crystal structure of snow, and is important for ice core interpretation, remote sensing, snow hydrology and chemical processes in snow. Prior investigations have inferred the sublimation rate from energy, isotopic, or mass-balance calculations using field data. Consequently, these studies were unable to control many of the environmental parameters which determine sublimation rate (e.g. temperature, relative humidity, snow microstructure). We present Sublimation rate measurements on snow samples in the laboratory, where we have controlled many of these parameters simultaneously. Results show that the air stream exiting the snow sample is typically saturated under a wide range of sample temperature and air-flow rate, within measurement precision. This result Supports theoretical work on single ice grains which found that there is no energy barrier to be overcome during sublimation, and suggests that snow sublimation is limited by vapor diffusion into pore spaces, rather than sublimation at crystal faces. Undersaturation may be possible in large pore spaces (i.e. surface- or depth-hoar layers) with relatively high air-flow rates. We use these data to place bounds on the mass-transfer coefficient for snow as a linear function of Reynolds number, and find that h(m) = 0.566 Re + 0.075. (c) 2008 Elsevier Ltd. All rights reserved.