An approximate methodology to simulate combined conduction-radiation heat transfer for multi-layer insulator

A quasi-analytical methodology was developed to model combined conduction-radiation heat transfer through the thickness of a reflective multi-layer insulator. This methodology was validated by the experimental result. It could be used for earlier steps of the design process of the high-temperature multi-layer insulators. Traditionally, radiation thermal conductivity approximation is used in the earlier stages of design. Despite the accuracy of this approach in steady-state cases, it yields to some unacceptable errors when the thermal load is transient. It was shown that old methodology can not predict maximum temperature and time of occurrences in acceptable margins. The developed model originated from the radiation thermal conductivity approximation. But unlike the primitive one, the developed model seems acceptable in transient cases. This model is based on consideration of thermal emittance through the thickness of the insulator. It can predict the maximum temperature of the structure and occurrences time with an error of less than 4%.