The NIST 3 megawatt quantitative heat release rate facility - description and procedures

Abstract

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...

Evaluation of the ability of fire dynamic simulator to simulate positive pressure ventilation in the laboratory and practical scenarios

“…The combustion products were captured by a 6 m x 6 m (20 ft x 20 ft) hood which was instrumented for oxygen consumption calorimetry. Oxygen depletion, temperature and pressure readings were continuously monitored in order to calculate the total heat release rate of the fire room [12]. …”

“…Total expanded uncertainties associated with oxygen calorimetry techniques are discussed in greater detail by Bryant et al [12]. This uncertainty was estimated to be 11 % and included components derived from gas concentrations, temperature and gas flows.…”

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“…하지만, 배기 덕트로 흡입하는 질량유량, 온도, 산소소모계수 등을 정확하게 측 정해야만 발열량 산출 값의 신뢰성을 확보할 수 있으므로 장비가 구축된 이후 우선적으로 안정성 작업이 선행되어 야 한다. Bryant (9,10) .…”

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“…Therefore, the heat release rate (HRR) for the NIST Continuous Feed Baby Dragon was also measured as a function of feeding rate. To do this, the entire apparatus was placed under the furniture calorimeter in the NIST Large Fire Laboratory (LFL) to determine the HRR using oxygen consumption calorimetry [29]. Using the methodology outlined in [29], the combined standard uncertainty of the peak HRR was determined to be 8 %.…”