Fire Safety Science Digital Archive

THE ADIABATIC SURFACE TEMPERATURE AND THE PLATE THERMOMETER The concept of Adiabatic Surface Temperature (AST) opens possibilities to calculate heat transfer to a solid surface based on one temperature instead of two as is needed when heat transfer by both radiation and convection must be considered. The Adiabatic Surface Temperature is defined as the temperature of a surface which cannot absorb or lose heat to the environment, i.e. a perfect insulator. Accordingly, the AST is a weighted mean temperature of the radiation temperature and the gas temperature depending on the heat transfer coefficients. A determining factor for introducing the concept of AST is that it can be measured with a cheap and robust method called the plate thermometer (PT) even under harsh fire conditions. Alternative methods for measuring thermal exposure under similar conditions involve water cooled heat flux meters that are in most realistic situations difficult to use and very costly and unpractical. This paper presents examples concerning how the concept of AST can be used in practice both in reaction-to-fire tests and in large scale scenarios where structures are exposed to high and inhomogeneous temperature conditions.