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Drift-flux analysis of two-phase flow in microgravity
Abstract
As NASA programs such as the International Space Station, the Space Shuttle, the Space Nuclear Power Initiative, and other future spacecraft become more demanding, two-phase (gas-liquid) systems for advanced life support and thermal management are highly advantageous over single-phase systems. Two-phase fluid loops provide significant thermal transport advantages over their single-phase counterparts and are able to carry more energy per unit mass than single-phase systems. They are also able to transport more energy per unit pumping power than single-phase systems. These two advantages alone offer great reductions in both mass and volume, which are two primary design parameters for space-based systems. Unfortunately, the ability to predict two-phase phenomena such as flow regime transitions and void fraction at microgravity conditions is greatly limited and its development is still in its infancy. A Texas A&M University two-phase flow loop was tested aboard NASA's KC-135 aircraft to collect two-phase microgravity data for dichlorodifluoromethane (R-12). A wide variety of flow rates were tested and many different flow regimes were observed. Data produced by the two-phase microgravity experiment were analyzed in accordance with the drift-flux model to calculate the distribution parameter, C₀, and the drift-velocity, V[gj], of the two-phase mixture. The C₀and V[gj] found for each flow regime were compared with other microgravity and a one-g upflow data. The C₀ for the slug flow regime was greater than that of the transition and annular flow regimes respectively for the microgravity data and correlated well with other R-12 microgravity data for the slug flow regime. The V[gj] for slug flow was found to be negative, which was unexpected, but the drift velocities for the transition and annular flow regimes provided expected results. The V[gj] for the annular flow regime in microgravity was less than that of the one-g upflow system due to the lower superficial velocities required in microgravity. Similarly, the C₀ for the R-12 microgravity data was higher than for a one-g upflow system due to its lower void fraction. A common C₀ and V[gj] can be used to predict void fraction for the transition and annular flow regimes for R-12 for the same pipe diameter and operating conditions.
Description
Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item.Includes bibliographical references (leaves 53-55).
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Citation
Braisted, Jonathan David (2004). Drift-flux analysis of two-phase flow in microgravity. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /ETD -TAMU -2004 -THESIS -B74.
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