EXECUTIVE SUMMARYThe 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 × 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 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.This document is intended to serve as a description of the NIST 3 Megawatt Heat Release Rate Facility and as an operations manual. It is also intended to serve as a general guide for implementing, operating and maintaining quality control of similar quantitative large scale heat release rate measurement facilities. The m...

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The National Fire Research Laboratory is a unique large-fire research facility; able to characterize the response of full-scale building systems to realistic mechanical loading and fire. The facility maintains an infrastructure of measurements necessary for accurately characterizing the heat release rate of fires, a key parameter in predicting fire hazard. This measurement infrastructure includes four oxygen consumption calorimeters to measure the heat released during fire experiments, and a fuel consumption calorimetry system (natural gas burners and flow control) to generate precise amounts of heat release. Both systems have a heat release rate capacity of 20 MW, twice the capacity of the previous facility. A rigorous evaluation of the processes for the measurements by oxygen consumption calorimetry and fuel consumption calorimetry has resulted in significant improvements in measurement uncertainty when compared to previous versions of the facility. Measurement agreement between the two independent systems has been demonstrated and provides evidence that NFRL's system of heat release rate measurements for large-scale fire research are the most accurate and highly characterized of their kind. The methodology, hardware, and performance of the large-fire calorimeters and natural gas flow system are described here to provide technical guidance on achieving accurate heat release measurements to laboratories with the mission of accurate large-scale fire testing.

SUMMARYAccurate heat release rate measurements provide essential information to defining the fire safety characteristics of products. The size, complexity, and cost of full-scale fire tests make achieving accurate and quantitative results a serious challenge. A detailed uncertainty analysis of a large-scale heat release rate measurement facility is presented as a guide to the process of estimating the uncertainty of similar facilities. Quantitative heat release rate measurements of full-scale fires up to 2.7 MW were conducted using the principle of oxygen consumption calorimetry. Uncertainty estimates were also computed for the heat input measurements from a well-controlled natural gas burner. The measurements of heat input and heat release rate were performed independently, and the discrepancy between the two was well within the uncertainty limits. The propagation of uncertainty was performed at the level of voltage and temperature measurements, which avoided using mutually dependent measurement parameters. Reasons for the significant contribution to the combined uncertainty from the oxygen concentration and exhaust flow measurements are demonstrated. Also presented is a first-order effort to account for the uncertainty due to factors in full-scale fire tests such as operator error and environmental influences that are not modeled by the heat release rate equation. Published in

Acetone¯uorescence provides a useful way to visualize the¯uid mixing process within supersonic wind tunnels, some of which operate in the low temperature (240±300 K) and low pressure range (0.1±1 atm). Measurements are presented to quantify the dependence of the acetone laser induced¯uorescence (LIF) signal on temperature and pressure in this range. The temperature and pressure sensitivity of the acetone LIF signal resulted in less than an 8% variation over the experimental conditions for a laser excitation wavelength of 266 nm. Condensation of the acetone vapor was identi®ed as a potential problem for this diagnostic technique. Methods to prevent and check for condensation are discussed.