Fundamental study of electrohydrodynamic induction pumping of a stratified liquid/vapor medium /
Electrohydrodynamic (EHD) pumping of two-phase media has potential applications related to both pure pumping as well as heat transfer enhancement. Utilization as a pumping mechanism is attractive for terrestrial and outer space systems. Augmentation of mass flux in two-phase heat transfer applicatio...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1999.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=731686531&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Electrohydrodynamic (EHD) pumping of two-phase media has potential applications related to both pure pumping as well as heat transfer enhancement. Utilization as a pumping mechanism is attractive for terrestrial and outer space systems. Augmentation of mass flux in two-phase heat transfer applications, such as boiling and condensation, leads to enhanced heat transfer coefficients, thus making EHD pumping an attractive candidate for these situations. In this study, EHD induction pumping of a stratified liquid/vapor medium was studied from a fundamental point of view. A non-dimensional analytical model accounting only for electric shear stress due to interfacial charges was developed. The effects of all involved parameters including the external pressure gradient on the interfacial velocity were presented for four cases of attraction and repulsion mode pumping and discussed in detail. A stability analysis was conducted to understand the operating conditions leading to more than one possible solution for the interfacial velocity. General stability criteria were derived for all cases under consideration. Stability maps were introduced allowing not only classification of pump operation as stable or unstable based on the input parameters, but also permitting identification of measures to be taken to insure stable pump performance. An advanced model was then derived considering also electric shear stresses in the bulk of the fluid due to charge induction as a result of a temperature gradient. A non-dimensional parametric study was conducted employing the advanced model assuming uniform and non-uniform entrance temperature profiles and accounting for Joule heating. The EHD induction pumping process was assessed experimentally by conducting Laser Doppler Anemometry measurements of the velocity profiles. A suitable experimental apparatus was designed and built. Detailed profiles were presented for the working fluid HCFC 123 and for coated and uncoated electrodes employing AC and DC applied electric Gelds of varying voltages and frequencies. Finally, issues related to the comparison of theoretical and experimental results were discussed. A direct comparison was not possible due to the unstable and turbulent flow observed during the experiments and the inability of the current models to predict this behavior to the extent required. |
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| Item Description: | Vita. "Major Subject: Mechanical Engineering". |
| Physical Description: | xix, 173 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 157-159). |