MODIFYING CONE CALORIMETERS FOR TESTING MATERIALS WITH LOW HEAT RELEASE RATES

摘要

The cone calorimeter was designed to measure heat release from combustible materials such as wood plastics and building products. These typically have peak heat release rates (HRR) of 250- 2000 kW/m2. Traditionally, the results have been either used directly, as predictors of full scale heat release, or as data for flame spread and other numerical models. More recently, some nations have issued standards and regulations which use HRR as measured in the cone. Some of the performance criteria specified in these new regulations are so low as to be within the currently allowable noise and drift levels of the instrument. A recent study identified three methods which could be used to improve upon noise and drift and make the cone calorimeter a more appropriate tool for low heat release measurements: 1. Reduce analyzer noise and drift by specifying a better performance requirement 2. Tighten laboratory practice to remove interfering influences 3. Increase the oxygen depletion levels (by using a larger specimen) This paper identifies improvement areas in all of the above areas but will focus on primarily on increasing oxygen depletion levels. A recent development in that area is the use of a larger cone heater which gives a uniform heat flux over the whole surface area of a much larger (150 x 150mm specimen). This paper will discuss the larger cone heater in more detail.