The acoustic levitation method (ALM) has found extensive applications in the fields of materials science, analytical chemistry, and biomedicine. This paper describes an experimental investigation of a levitated droplet in a 19.4-kHz single-axis acoustic levitator. We used water, ethanol, water/ethanol mixture, and hexane as test samples to investigate the effect of saturated vapor pressure on the flow field and evaporation process using a high-speed camera. In the case of ethanol, water/ethanol mixtures with initial ethanol fractions of 50 and 70 wt%, and hexane droplets, microlayered toroidal vortexes are generated in the vicinity of the droplet interface. Experimental results indicate the presence of two stages in the evaporation process of ethanol and binary mixture droplets for ethanol content >10%. The internal and external flow fields of the acoustically levitated droplet of pure and binary mixtures are clearly observed. The binary mixture of the levitated droplet shows the interaction between the configurations of the internal and external flow fields of the droplet and the concentration of the volatile fluid. Our findings can contribute to the further development of existing theoretical prediction.
We experimentally investigate the flow structure and evaporation behavior of a droplet in an ∼19 kHz single-axis acoustic levitator. Decane, nonane, octane, heptane, hexane, and pentane are used as test fluids to investigate the effect of saturated vapor pressure on the internal and external flow fields. Under low saturated vapor pressure (decane and nonane), the direction of the external flow is away from the surface of the droplet. However, at a relatively higher saturated vapor pressure (octane, heptane, hexane, and pentane), the direction of the external flow is toward the surface of the droplet, with vortices forming near the droplet surface. For droplets with a low saturated vapor pressure (decane, nonane, octane, and heptane), the internal flow is similar to that in the case of rigid body rotation. Finally, under high saturated vapor pressure (hexane and pentane), the internal flow is an unsteady 3D complex flow. The experimental results indicate that the vapor concentration distribution around a levitated droplet surface correlates closely with changes in the external and internal flows.
*f5h#^_icjHk)Hl[&5# mnfg#fo'pq45 6789ab#r&s34)#t0euv"w (0xy[4'&[512/D)z{#|} ~#I?6)fg#12/Dz{ 005'*!#\ 9i!#&+f0!'5 *!5? 6))b0pqc&&' 6$%pq*!a!4 5#"w034!4?[\ 0$&\"r&s34'\pq)45)12#,)¡¢0£¤¥34' pq)1g#|¦\46456 789ab#pq0xy[4!'£ !"#$\912/D)z{ # §¨0©ª6#/'5: « ¬ < ae > ?° *pqc±²&'³´µ ¶•Gç ¹&\#ºa»¼½¾¿6ÀÁÂPM4, 0ÃÄ0ÅAE!12/DcÇ66,()4 ÈÉÊËÌ*/)1g#R&5ÍÎH*Ï45)ÐÑÒ# §k545)h#12/D&65 Ó Ô Õ ; ; Ö ×Ö ; aeØ ÓÓ ÙÚ §Û §ÛÜ_YÛÝÞßb5àYÛáâãCaÛÂPM äå ae Õ < ae = å åçèéêëì« íîï ð ñÕ ae ae ò ae Ô å < ae ae ó Õ î < ôõ ö ÷ ð ø õ ùõ ú õ ø ö ûü ý ö ôü < þ ff õ 0 ff 1 2 3456789abcdef de ü ü ü ! 0 ü ! " õ " ö !# 0 ü ú úùö " ý$÷ " õ ú ! ö 0% õ & ö õ " ö ! ñî ' ' ü 0 " ' ü ü ö ! ()õ " ü ò * + ,-.. /01 02 0/%/ü ! 1 ö 3 4 5 6 7 8 9 6 % !ú ÷ ù ' ü ü ö ! ('ùõ " ü " ý õ "ö ! 0 ÷ þ & ü úú ÷ þ " ü ú ¬2 þ üö 0 üö ú2 & þ 0 ü &õ ! &ô ú " '" ý üú ÷ þ " ü úõ ü ü ô : ü &' ô " ý ü' ü !2 ý õ ú üõ ! &0 ! 0 ü ! " õ " ü &ö !õ !þ ! ' ü !÷ ö ; þ ö & 2 ý õ ú ü Ö0"' õ ú "' ü ü ö ! (õ " ü ¬ ý ùü : ü ¬÷ õ (ü2 õ " '" ý üú ÷ þ " ü ú' ô ú ÷ þ " ö !ö ú0 õ 2 " þ ü & ö ! " " ý ü' ü ü ö ! (ö ! " ü ' õ 0 üõ ! &" ý ü !" ý üú ÷ þ " ö !ö ú! " 0 ! 0 ü ! " õ " ü & Öí 2 ü : ü ! " " ý ö ú0 õ 2 " þ ü '" ý üú ÷ þ " ü ú ¬" ý üú " ! (õ (ö " õ " ö ! '" ý ü' ü ü ö ! (ö ! " ü ' õ 0 üö ú: ü <ü ' ' ü 0 " ö : ü Ö1 üý õ : ü= ü ü ! ú " þ & < ö ! (" ý üõ 2 2 ÷ ö 0 õ = ö ÷ ö " < 'þ ÷ " õ ú ! ö 0ö õ & ö õ " ö !" " ý üõ (ö " õ " ö ! (ôü " ý & ¬õ ! &' þ ! &" ý õ " " ý ü' ü ü ü0 ! 0 ü ! " õ " ö !ü ' ' ö 0 ö ü ! 0 < 'ú ÷ þ " ü úö úö ô2 : ü &(ü õ " ÷ <= <" ý ö úö õ & ö õ " ö ! Ö% !" ý ö ú 2 õ 2 ü ¬" ý üü ' ' ü 0 " ú ' " ý ü' ü ü ö ! (õ " üõ ! &" ý üþ ÷ " õ ú ! ö 0ö õ & ö õ " ö ! !" ý ü' ü ü ü0 ! 0 ü ! " õ " ö ! 0 ý õ õ 0 " ü ö ú " ö 0 úõ ü ü 2 " ü & Ö > ? @ AB 7 5 C ü ü ü0 ! 0 ü ! " õ " ö ! ¬ ü ü ö ! (õ " ü ¬$÷ " õ ú ! ö 0ö õ & ö õ " ö ! Ö J-K Ô aeL ×MñÔ Õ ; = ò
The acoustic levitation is one of the levitation techniques to control a sample in sound pressure. The acoustic levitation induces the internal and external flow of the levitated droplet. It is considered that these flows affect heat and mass transfer of the levitated droplet. The purpose of this study is to investigate the relationship between convective heat transfer and flow behavior of the levitated droplet. The convective heat transfer between ambient air and the droplet is calculated by an evolution of the surface area and temperature. The convective heat transfer increases as the temperature of water droplet increases. The external flow structure is measured by PIV. The non-heated water droplet has a toroidal vortex below a levitated droplet. As the temperature of water droplet increases, the external flow structure changes from that of non-heated droplet. The larger the diameter and temperature of droplet become, the larger external flow velocity near the surface of the levitated droplet becomes. It is suggested that the increase of external flow velocity enhances the convective heat transfer and the convective heat transfer is more enhanced by the increase of temperature.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.