Scaling of internal wall temperatures in enclosure fires

Abstract

Scaling of internal wall temperatures in enclosure fires The scaling of enclosure fires, including internal wall temperatures and heat fluxes, are thoroughly analyzed and a method of scaling internal wall temperatures is proposed. Two series of room fires were tested in three different scales, i.e. full scale (1:1), medium scale (1:2) and small scale (1:3.5), according to the theory. The fire source was either placed at the center or in the corner of the enclosures. The measured internal wall temperatures, incident heat fluxes, gas temperatures, gas velocities and gas concentrations in different scales are compared and analyzed. The results show that the proposed scaling method is able to scale the internal wall temperature very well, especially in medium scale. The incident heat fluxes and gas velocities are also scaled very well. The gas temperatures and gas concentrations are scaled generally relatively well. The calculation of upper layer gas temperatures in the compartment fires are investigated. The results show that both the maximum ceiling excess gas temperatures and average ceiling excess gas temperatures at the upper layer for corner fires are higher than those for center fires, and the ratio is 1.25 for both the maximum and the average ceiling excess gas temperatures. The maximum excess gas temperature normally exists right above the fire and is approximately 19 % higher than the average values for both center fires and corner fires. The widely used MQH equation cannot directly be used to estimate the gas temperatures in compartments covered with insulating materials. A correlation has been proposed to estimate the upper layer gas temperatures in compartments covered by similar insulating materials for both center fires and corner fires. The equation is expected to be valid for gas temperatures below 700 o C or slightly higher, but not over 1000 o C.

Experimental study on the influence of different thermal insulation materials on the fire dynamics in a reduced-scale enclosure

“…In addition to scaling the heat release rate of the burner, the need for scaling the time parameter was apparent as the thickness of the walls remained the same. The scaling of the time parameter was based on Quintiere [19] and on Li and Hertzberg, who scaled internal wall temperatures in enclosure fires [18]. Their study concluded that these scaling correlations presented a good agreement between the results from the scaled experiments and the large scale experiments within a number of different focus areas, including the HRR and the time parameter.…”

Testing for knowledge: Application of machine learning techniques for prediction of flashover in a 1/5 scale ISO 13784‐1 enclosure

“…15 In particular, the gas burner HRR and the gas burner duration were scaled with, respectively, Equation (1) 16 and Equation (2). 16…”

“…To ensure that a correlation would exist across the scales, the Froude scaling technique was used to scale down the size of the fire with respect to the geometric scaling of the enclosure. 15 In particular, the gas burner HRR and the gas burner duration were scaled with, respectively, Equation (1) 16 and Equation (2). 16…”

Scaling of wood pallet fires

“…The Froude scaling has been used widely in open and enclosure fires and results from model scale tests seem to fit full scale results well, see e.g. Li and Hertzberg's work [5]. Research on tunnel fires also shows there is a good agreement between model scale and full scale test results on many focused issues [14,15,[18][19][20][37][38][39].…”

“…However, the scaling laws used for the thick insulating materials may not be accurate. Li and Hertzberg [5] conducted a scaling study of heat conduction and heat balance in a room fire. They carried out two series of room fire tests in three different scales where the aim was to investigate the scaling of temperatures inside the walls.…”