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NIST 3 Megawatt Quantitative Heat Release Rate Facility: Description and Procedures.


pdf icon NIST 3 Megawatt Quantitative Heat Release Rate Facility: Description and Procedures. (3527 K)
Bryant, R. A.; Ohlemiller, T. J.; Johnsson, E. L.; Hamins, A.; Grove, B. S.; Guthrie, W. F.; Maranghides, A.; Mulholland, G. W.

NISTIR 7052; 130 p. September 2004.

Keywords:

heat release rate; calorimeters; uncertainty; quality control; gas sampling; data analysis; education; training; burners; natural gas; oxygen consumption; response time

Abstract:

The 3 Megawatt Heat Release Rate Facility (3MWHRRF) was developed at the National Institute of Standards and Technology (NIST) as a first step toward having broad capabilities for making quantitative large scale fire measurements. Such capabilities will be used at NIST to validate fire models and to develop sub-grid models. It will also serve to provide a data base for studying a broader range of fire phenomena, and to address issues related to material acceptance and fire codes. An equally important objective is to provide templates for use by other laboratories including commercial testing facilities to improve the quality of their data. Heat release is the result of the combustion of a fuel with the oxygen in air. The fuels of primary interest are those found in constructed facilities and include wood, plastics, foam materials used in furnishings (such as polyurethane), wire insulation (such as polyvinyl chloride), and carpet materials (such as nylon). The rate at which heat is released is the single most important quantity in terms of fire safety. Thus it is important that this measurement be made in a quantitative manner. It is a key predictor of the hazard of a fire, directly related to the rate at which heat and toxic gases build up in a compartment or the rate at which they are driven into more remote spaces. Heat release rates on the order of 1 MW to 3 MW are typical in a room that is flashed over or from a single large object such as a bed or sofa. It is important that heat release rate measurements be made accurately because fire regulations are frequently based on peak rates of heat release. Testing laboratories must be confident that the objects tested pass the required regulation and manufacturers need accurate information in defining the fire safety characteristics of their products. A second need for accurate heat release rate data is for the development of quantitative models for predicting heat release rate. In comparing a fire experiment and a model prediction, it is essential that the heat release rate measurement have an estimated uncertainty. The 3MWHRRF developed at NIST meets the needs described above for objects that can be placed under the 6 m OE 6 m hood, which is approximately 4 m above the floor, or for enclosures whose effluent can all be directed into the hood. It is capable of measuring heat release rates in the range of 0.10 MW to 3.0 MW including brief peaks as high as 5 MW. As documented in this publication, the expanded uncertainty (95% confidence interval) is 11% of the heat release rates in the range of 0.10 MW to 3.0 MW including brief peaks as high as 5 MW. As documented in this publication, the expanded uncertainty (95% confidence interval) is 11% of the heat release rate for fire sizes larger than 400 kW. The response time of the system is such that it can accurately resolve dynamic heat release rate events of 15 seconds or more.