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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Heat and mass transfer 29 (1994), S. 319-327 
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung In einem Fluidsystem, das bei hohem Wärmefluß den Effekt des unterkühlten Siedens zeigt, findet der wesentliche Wärmetransportmechanismus in einer sehr dünnen Schicht statt, die zwischen der beheizten Oberfläche und den Dampfpolstern liegt und als „Unterschicht“ bekannt ist. Basierend auf den Gesetzmäßigkeiten des konvektiven Siedens unter dominierendem Einfluß der Wärmeleitung durch die Flüssigkeits-Unterschicht wurde ein theoretisches Modell zu Beschreibung des Wärmeübergangs bei unterkühltem Sieden entwickelt. Um nützliche Daten für die Simulation der in Leichtwasserreaktoren (LWR) herrschenden Bedingungen zu gewinnen, erfolgten die Experimente bei Aufwärtsströmung siedenden Wassers in einem senkrechten Rohr im Druckbereich 6,9 bis 15,5 MPa. Diese experimentellen Ergebnisse werden mit Vorausberechnungen nach dem erstellten Theoriemodell, sowie jenen nach fünf der bekanntesten Korrelationen verglichen. Für unterkühltes Sieden in Leichtwasserreaktoren zeigte sich hierbei, daß die Experimente am besten durch das neuentwickelte Modell wiedergegeben werden.
    Notes: Abstract In a subcooled flow boiling system at high heat flux, the major heat transfer mechanism places emphasis on a very thin liquid layer, known as the ‘sublayer’ which is trapped between the heated surface and the vapor blankets. Base on the convective boiling heat transfer dominated by the heat conduction through the liquid sublayer, a theoretical model for subcooled flow boiling heat transfer has been developed. To provide useful data in the simulation of Light Water Reactors (LWRs) conditions, heat transfer experiments for up-flow boiling water through a vertical tube at the pressure ranging from 6.9 to 15.5 MPa have been conducted. The experimental results are compared with the predictions of the present model and other five famous correlations. For the LWRs subcooled flow boiling, the comparison reveals that the present model show the best agreement with the measured data.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied electrochemistry 24 (1994), S. 1170-1175 
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract A one-phase, two-dimensional fluid model is applied to predict the flow and thermal fields between electrodes in an electrochemical drilling (ECD) process. A body-fitted curvilinear coordinate transformation is used such that a moving, irregular surface of the workpiece in the physical domain becomes a fixed, regular boundary in the computational domain. The equilibrium workpiece shapes predicted by the present model agree in general with experimental results. Results show that some transport properties vary abruptly in the transition region. In the transition region, the rate of change of pressure in the streamwise direction is higher near the tool than near the workpiece. The electrolyte temperature near the surfaces of the workpiece and the tool in the transition and side regions is higher than that in other places.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied electrochemistry 23 (1993), S. 316-321 
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The purpose of the present paper is to describe the simulation of electrochemical drilling (ECD), which is generally affected by the electrical field and the flow field between two electrodes. A body-fitted transformation is applied to predict precisely the gradient of the electric potential field, and a bubbly-two-phase flow model is used to simulate the quasi-static electrochemical drilling process. The metal removal rate, determined by the variation of electric potential and the thermal-fluid properties, is then calculated. Numerical results agree well with experimental data. The void fraction is the most important factor in determining the electrolyte conductivity and the equilibrium shape of the workpiece. The overcut of the workpiece can be reduced by increasing the tool feed rate or decreasing the electrolyte flow flux. A bare bit type of tool, compared with coated tool and bare tool, can also diminish the overcut in ECD.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied electrochemistry 29 (1999), S. 321-330 
    ISSN: 1572-8838
    Keywords: ECM ; inverse problem ; numerical ; thermal-fluid properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The effect of thermal-fluid properties are considered in the numerical simulation of the tool shape for a given workpiece shape in electrochemical machining. An embedding method is used for this inverse problem. A bubbly two-phase, one-dimensional flow model and a one-phase, two-dimensional flow model are applied to predict the fluid field of the electrolyte, respectively. Results show that the void fraction is the most important factor in determining the electrolyte conductivity and the shape of the workpiece. The proper machining conditions and numerical parameters are important to obtain a good solution. The relative error can be reduced under 0.002.
    Type of Medium: Electronic Resource
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