Spontaneous imbibition of liquids in glass‐fiber wicks. Part I: Usefulness of a sharp‐front approach

Abstract

Spontaneous imbibition of a liquid into glass‐fiber wicks is modeled using the single‐phase Darcy's law after assuming a sharp flow‐front marked by full saturation behind the front occurring in a transversely isotropic porous medium. An analytical expression for the height of the wicking flow‐front as a function of time is tested through comprehensive experiments involving using eight different wicks and one oil as the wicking liquid. A good fit with experimental data is obtained without using any fitting parameter. The contact‐angle is observed to be important for the success of the model—lower contact angle cases marked by higher capillary pressures were predicted the best. The proposed model provides a nice upper bound for all the wicks, thereby establishing its potential as a good tool to predict liquid absorption in glass‐fiber wicks. However, the sharp‐front model is unable to explain region of partial saturation, thereby necessitating the development of part II of this article series (Zarandi and Pillai, Spontaneous Imbibition of Liquid in Glass fiber wicks. Part II: Validation of a Diffuse‐Front Model. AIChE J, 64: 306–315, 2018) using Richard's equation. © 2017 American Institute of Chemical Engineers AIChE J, 63: 294–305, 2018

Microstructural evolution and corrosion behavior of a laser surface modified cast Co–Cr–Mo–C alloy

“…The results indicate that improved corrosion resistance is achieved by LSM processing as shown in Figure 6 and Table 3. In general, structural alloys exhibit improved corrosion resistance due to protective oxide films formed on their surfaces (Knapp & Wren, 2012; Momeni, Behazin, & Wren, 2016; Momeni & Wren, 2015; Zarandi, Pillai, & Kimmel, 2018). Corrosion involves surface redox reactions (metal oxidation coupled with solution reduction) and interfacial transfer of the charged species involved in the redox reactions.…”

Flow along and across glass‐fiber wicks: Testing of permeability models through experiments and simulations

“…As we shall later, the shape and small size of the wick samples allow us to apply the falling‐head method very well. Many permeability measurement techniques, especially for fabrics and fiber mats used in LCM, involve forcing a high‐pressure liquid to pass through a porous sample . In contrast, our chosen technique is a gentle gravity‐driven method that does not use high applied pressures and hence does not cause any flow‐induced compression or deformation in the wicks.…”

“… The falling‐head permeameter used for measuring the permeability of small fiber‐ wick samples: (a) schematic and (b) photo.…”

“…For example, the glass‐fiber wicks have been used extensively in TIKI torches because of their low cost and ease of manufacturing. Despite being used extensively in a popular household product, it is surprising that wicking in such a medium has not be studied scientifically and in detail until recently . The present study is an attempt to characterize its important property (permeability), which is crucial for predicting wicking‐flows.…”

“…The imbibitional flow of a liquid in wicks due to capillary suction has been modeled using several different approaches . Among the many methods available to model the wicking phenomenon mathematically, the Washburn equation based approach, the sharp‐front approach based on Darcy's law for single‐phase flow, and the diffusive‐front approach based on Richard's equation are perhaps the most popular and widely used. These mathematical models require porous‐medium (wick) properties such as hydraulic radius, fiber radius, porosity, and so forth, to be useful in prediction and optimization studies.…”