Browsing by Author "Ungan, Aydin"

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    Melting behavior of continuously charged loose batch blankets in glass melting furnaces
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1986) Ungan, Aydin; Viskanta, Raymond
    The paper reports on numerical methodology for predicting the melting of a two-dimensional, axially fed glass batch blanket. In the absence of rheological data for commercial glass batch mixtures, it is assumed that each grain within batch acquires a horizontal velocity, which is constant and equal to that of charging speed throughout the transformation process. The vertical motion of batch is obtained from Newton's first law of motion by ignoring all the internal shear stresses in the vertical direction. During the transformation, the chemical reactions are simulated using modified form of Arrhenius equation. The gas percolation within the blanket is considered and the flow is predicted using Darcy's law, and heat exchange between gas and solid phase is accounted for. The formation of molten glass layer on the top of the blanket is modeled by appropriate transport equations, and the penetration of radiation from the combustion space incident on this semitransparent layer is approximated by spectral, two-flux equations. The system of equations is solved using the marching method of Patankar and Spalding [16]. The model is utilized to generate some sample results under idealized conditions. Accordingly, the heat flux at the top surface is assumed to be due to an effective gas-crown temperature. At the bottom surface, the heat flux from the melt was simulated by imposing a constant heat flux over the entire batch. A baseline condition is set for each parameter and parametric calculations were performed for a range of physically plausible conditions to determine the effects of the bottom heat transfer rate and preheating on the batch melting characteristics.
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    Three-dimensional numerical modeling of circulation and heat transfer in a glass melting tank Part 1. Mathematical formulation
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1987) Ungan, Aydin; Viskanta, Raymond
    This paper presents numerical methodology to simulate the transport processes in a glass melting tank. The model also considers the most widely used glass circulation enhancement schemes such as air bubblers and electric boosting. Refining process is simulated by predicting the size distribution and number density of gas bubbles within the glass melt. The gas bubbles are allowed to grow and dissolve within the melt. The diffusion of gas is restricted to a single component, and bubble rupture and collision are neglected. Contribution of gas bubbles to the buoyancy force is also accounted for. The numerical method of solution employed is summarized.
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    Three-dimensional numerical modeling of circulation and heat transfer in a glass melting tank Part 2. Sample simulations
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1987) Ungan, Aydin; Viskanta, Raymond
    In part 1 of the companion paper the mathematical formulation and numerical solution procedure was developed for the simulation of the transport processes within a glass melting tank. In this paper the utility of the model, as coupled to the batch and combustion space submodels, is demonstrated by presenting and discussing sample numerical results.