- Author
- Paulsen, O.
- Title
- On the Heat Transfer in Fire Test Furnaces.
- Coporate
- Technical University of Denmark
- Keywords
- furnaces | heat transfer | fire tests | reporducibility | temperature | temperature field | geometry | thermal radiation | thermal properties | masonry
- Identifiers
- fire tests and natural fire; description of an EDP-program for calculation of the thermal conditions in a fire test furnace; calculates results: systematics
- Abstract
- In Chapter 1 fire tests are discussed in relation to natural fires, based on literature. The reproducibility of fire tests is discussed. Temperatures and heat transfer conditions are mentioned, and previous works on heat transfer in fire test furnaces are recapitulated. A brief survey of the matter of equivalent time based on fire tests is given. In Chapter 2 are given the parameters which, for a given temperature-time curve, are important for heat transfer in fire test furnaces: [A] Size and geometry of furnace. [B] Ability of the furnace atmosphere to emit and absorb thermal radiation. [C] Thermal properties of the masonry of the furnace. [D] Type of fuel. A calculation model has been given, containing the above mentioned parameters: The development in time of the temperature field in furnace walls and specimen is described by the Fourier equation in one dimension. Radiation interchange between combustion products and furnace walls is described by an integral equation. The combustion products in the furnace are considered as a "modified grey gas" of uniform temperature. Convective heat transfer between gas (combustion products) and furnace walls is of minor interest and calculated in a simple way from empirical terms. Thus the boundary condition of the heat conduction equation is formed by the net heat flux by radiation and convection. Furthermore the signal from a temperature sensor positioned in the furnace is calculated. And a heat balance for the entire furnace is set up for calculation of the power consumption of the furnace. In Chapter 3 an EDP-programme is described which will compute a fire test furnace by the model mentioned in Chapter 2, and an example of a computation is given. In Chapter 4 is given the result of a great number of systematic computations roughly covering the existing fire test furnaces. These results have been systematized into a form making it possible - on the basis of relatively few data - to determine the thermal properties of a furnace and to make a methodical comparison between different furnaces. The statement is supported by examples. Chapter 5 gives a comparison of computations based on experiments using the fire test furnace in the Laboratory of Heating and Air Conditioning, the construction of which furnace was conducted by the author. Experiments were made with both gas- and oil-heating. Chapter 6 contains a speculative section concerning testing of a structure, containing considerable quantities of combustible material, but is, apart from that, concentrated upon the possibilities of an improved practice for testing. Different suggestions from the literature on improvement of the furnace tests are reviewed. A partly quantitative analysis has been carried through of a measuring instrument to be used in fire test furnaces. This instrument may improve the reproducibility considerably and has the very important property, that it does not render the definition of a standardized temperature curve impossible.