A report presents a computational study of heat and mass transfer for isolated and interacting drops of one fluid (liquid O2) immersed in another fluid (H2) in finite, quiescent surroundings under supercritical conditions. The mathematical models used in this study were described in three previous articles in NASA Tech Briefs; namely, "Model of a Drop of O2 Surrounded by H2 at High Pressure" (NPO-20220), "The Lewis Number Under Supercritical Conditions" (NPO-20256), and "Model of Interacting O2Drops Surrounded by H2 at High Pressure" (NPO-20257), Vol. 23, No. 3 (March 1999), page 70.

This work was done by Josette Bellan and Kenneth Harstad of Caltech forNASA's Jet Propulsion Laboratory. NPO-20404

Topics:
Heat transfer Materials properties Mathematical models Physical Sciences Pressure Simulation and modeling Thermodynamics
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Evaporation of isolated and collections of fluid drops under superficial conditions

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NASA Tech Briefs Magazine

This article first appeared in the September, 1999 issue of NASA Tech Briefs Magazine (Vol. 23 No. 9).

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Overview

The document presents a computational study on heat and mass transfer for isolated and interacting drops of liquid oxygen (O₂) immersed in hydrogen (H₂) under supercritical conditions. Conducted by researchers Josette Bellan and Kenneth Harstad at the California Institute of Technology for NASA's Jet Propulsion Laboratory, the study builds upon previous articles that established mathematical models for this fluid system.

Key findings from the research indicate that under supercritical conditions, the behavior of the O₂/H₂ system is characterized by slow diffusion. The study identifies a sequence in which temperature, density, and mass-fraction profiles relax, with temperature relaxing the fastest, followed by density, and then mass-fraction. This sequence is crucial for understanding the dynamics of fluid interactions in supercritical environments.

One of the significant insights from the study is the effect of clustering of drops. As pressure increases, the accumulation of oxygen in the interstitial regions between drops becomes pronounced, leading to increasingly smeared gradients. This behavior contrasts sharply with that observed in isolated drops, where the gradients are more defined. The research also highlights that the effective Lewis number—an important parameter in heat and mass transfer—can be as much as 40 times greater than the traditional Lewis number. This discrepancy suggests that the traditional Lewis number may not adequately represent the relative importance of heat and mass transfer in these conditions.

The document emphasizes the juxtaposition of isolated versus collective behavior of fluid drops, contributing to a deeper understanding of the dynamics at play in supercritical fluids. The findings have implications for various applications, including propulsion systems and combustion processes, where understanding the interaction of fluid drops is critical.

Overall, this study enhances the knowledge of heat and mass transfer in supercritical conditions, providing valuable insights for future research and practical applications in aerospace and other fields. The work is documented in NASA Tech Brief NPO-20404, which serves as a technical support package detailing the methodologies and conclusions drawn from the research.