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Open AccessArticle

Thermal Boundaries in Cone Calorimetry Testing

1
Fire Safety Centre, Korea Conformity Laboratories, Cheongju 28115, Korea
2
Built Environment Research Institute, Ulster University, Newtownabbey BT37 0QB, UK
*
Author to whom correspondence should be addressed.
Coatings 2019, 9(10), 629; https://doi.org/10.3390/coatings9100629
Received: 7 August 2019 / Revised: 25 September 2019 / Accepted: 27 September 2019 / Published: 29 September 2019
(This article belongs to the Special Issue Advanced Coating for High Temperature Applications)
Bench-scale cone calorimetry is often used to evaluate the fire performance of intumescent-type coatings. During the tests, the coating geometry inflates. These thick, block-shaped specimens expose their perimeter side surfaces to both the heat source and the surroundings, unlike the typical thin, plate-shaped samples used in flammability tests. We assessed the thermal boundaries of block-shaped specimens using plain steel solids with several thicknesses. The heat transmitted through the exposed boundaries in convection and radiation modes was determined by four sub-defining functions: non-linear irradiance, convective loss, and radiant absorption into and radiant emission from solids. The individual functions were methodically derived and integrated into numerical calculations. The predictions were verified by physical measurements of the metals under different heating conditions. The results demonstrate that (1) considering absorptivity, being differentiated from emissivity, led to accurate predictions of time-temperature relationships for all stages from transient, through steady, and to cooling states; (2) the determined values for the geometric view factor and the fluid dynamic coefficient of convection can be generalized for engineering applications; (3) the proposed process provides a practical solution for the determination of optical radiative properties (absorptivity and emissivity) for use in engineering; and (4) the heat transmitted through the side surfaces of block specimens should be included in energy balance, particularly in the quantification of a heat loss mechanism. This paper outlines a comprehensive heat transfer model for cone calorimetry testing, providing insights into the mechanism of complex heat transmission generated on the test samples and quantifying their individual contributions. View Full-Text
Keywords: intumescent coating; cone calorimeter; thermal boundary condition; view factor; emissivity; absorptivity; convective heat transfer coefficient intumescent coating; cone calorimeter; thermal boundary condition; view factor; emissivity; absorptivity; convective heat transfer coefficient
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MDPI and ACS Style

Kang, S.; Kwon, M.; Choi, J.Y.; Choi, S. Thermal Boundaries in Cone Calorimetry Testing. Coatings 2019, 9, 629.

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