Evaporation of an isolated liquid plug moving inside a capillary tube. (October 2015)

• Record Type: Journal Article
• Authors: Srinivasan, Vyas; Marty-Jourjon, Victor; Khandekar, Sameer; Lefèvre, Frederic; Bonjour, Jocelyn
• Is Part Of: International journal of heat and mass transfer. Volume 89(2015:Oct.)
• Page Start: 176
• Page End: 185
• Publication Date: 2015-10
• Subjects: Taylor plug flow -- Thin-film drainage -- Evaporation -- Taylor's law -- Dewetting -- Partial wetting; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2015.05.039
• Languages: English
• ISSNs: 0017-9310

Abstract

Highlights: Evaporation dynamics of a Talyor liquid plug moving inside dry capillary tube. Liquid thin film drainage from the receding meniscus due to plug motion. Dewetting of liquid thin film and its evaporation under isothermal heating. Prediction of evaporative flux for isolated liquid plugs using hydrodynamic theory. Abstract: The paper reports an experimental study to understand the evaporation mechanism of a partially wetting isolated liquid plug (methanol) of length L moving inside a long, dry, horizontal circular glass capillary tube (ID = 1.5 mm). The plug (with specified range of non-dimensional L / D ratios) is pushed from rest by controlled injection of air from one side, till a quasi-steady terminal plug velocity is achieved in the adiabatic section (non-heated length) of the capillary tube. Under such conditions, the drainage of thin-film occurring at the receding interface and its subsequent dewetting is well predicted by existing literature. The plug is then allowed to move through the heated section maintained at constant wall temperature (lesser than the saturation temperature of methanol). The drained film now starts evaporating rapidly, drastically affecting the bulk transport behavior. High resolution videography, coupled with laser confocal microscopy provides vital bulk as well as local information, including time-varying plug length, film thickness and local dewetting behavior near the contact line. Experimental results obtained for different wall temperatures and different initial L / D ratios of liquid plug suggests that the Taylor's law for predicting drainage characteristics under adiabatic flow conditions is valid, even for cases where there is a continuous evaporation of thin-film. The study thus provides a framework for modeling evaporative flux based on simple hydrodynamic theory of film drainage.