Separation of heat transfer modes in fire: Review and analysis

The local heat transfer to a fire-exposed surface consists of radiative and convective components. Computational fluid dynamics fire models independently predict each of these heat transfer modes. However, experimental measurements of heat transfer are typically limited to measurements of the total heat transfer rather than the separation of individual components. As a result, it can be difficult to identify whether total heat transfer discrepancies between models and experiments are due to errors in convective and/or radiative heat transfer. Several different approaches have been presented over the years to separate the total measured heat transfer into its individual components. Each method comes with its own assumptions, limitations, and uncertainties. This paper provides a review of the existing literature on this topic which is augmented with engineering analysis. Previous studies are summarized, the mathematical formulations in each method are presented, and the uncertainties associated with the assumptions are discussed. These results are then used to estimate the expanded uncertainty associated with each approach. Under ideal conditions, the uncertainty of the separated heat transfer modes are approximately 15% of the total heat flux. Under less ideal conditions this uncertainty is higher. General recommendations to reduce these uncertainties in future studies are provided. • Summarizes studies on separating heat transfer modes in fire using four methods. • Provides data on repeatability of heat transfer measurements in local fire exposures. • Presents engineering analysis of assumptions employed by each separation method. • Calculates the expanded uncertainty associated with each separation method. • Provides general recommendations to minimize uncertainties in future studies.