1997-12-31

An empirical approach to evaluating various compositions and configuration of high temperature heat shields 973123

Qualitative evaluation of over 100 heat shields was completed with the use of K-Flow 1.0, a Windows based computer program developed by Thermal Ceramics. These evaluations were designed to eliminated some of the cost incurred in developing and testing new heat shield configurations by narrowing the amount of actual lab testing required, K-Flow 1.0 offers a logical focused starting point while allowing for inexpensive investigation into other thermal containment alternatives. The empirical evaluation of various heat shield characteristics and how they relate to differential temperature provided several qualitative conclusions. The expected increased in differential temperature( a lower cold face temperature for a given hot face) was seen for increasing thickness and density. When the cold face temperature is plotted against the varied thickness or density, the relationship is not completely linear, Instead, the slope of the plot clearly change, indicating a point of diminishing returns for applications at specific temperature. The emissivity of the heat shield surfaces, both the hot and cold face, were varied independently. While altering the emissivity of the hot face offered little improvement, increasing the emissivity of the cold face did provide noticeably lower cold face temperatures. The emissivity affect is easily over-shadowed by the other factors and is considered a minor parameter. The presence of air gaps within a heat shield composite can also drastically affect the cold face temperatures Air gap thickness and location were varied with respect to temperature. The close the air gap was to the cold face the lower the temperatures became. It was also noticed that the thinner the air gap the cold face temperature. The effects of air flow paste the cold face of a heat shield were also examined. A plot showed the expected relationship of increased air velocity resulting in decreased cold face temperature.

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