Evaluation of Empirical Evidence Against Zone Models for Smoke Detector Activation Prediction
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Evaluation of Empirical Evidence Against Zone Models for Smoke Detector Activation Prediction Thomas Cleary *, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA Gabriel Taylor, Nuclear Regulatory Commission, Washington, DC 20555-0001, USA Received: 31 January 2020/Accepted: 5 November 2020
Abstract. A series of experiments were conducted in a large room to generate data to assess the accuracy of computer fire model predictions of detector activation time. A comparison between experimental measurements and zone model predictions of the detector activation in the Consolidated Fire and Smoke Transport model (CFAST) version 7.4.3 were made. The experimental room was 11.0 m by 7.3 m by 3.7 m high with a single opening 2.44 m high and 1.83 m wide centered in a short wall. Two ceiling configurations were examined, a flat ceiling and a flat ceiling with two 0.30 m wide and 0.30 m deep solid beams. The fire source was a gaseous fuel burner fed with different mixtures of propane and propene that produced soot yields ranging from 0.010 gsoot/gfuel to 0.072 gsoot/gfuel and a fuel flow ramp time that ranged from 30 s to 1800 s. The heat release rate profile reached a nominal maximum value of 30 kW. The activations of two different models of photoelectric smoke detectors and a single ionization smoke detector, each with a range of alarm set points and installed at various locations on the ceiling, were recorded. Predictions of the various smoke detector activation times were made in CFAST with the temperature approximation method, and a fixed smoke detector concentration method for photoelectric detector activations. Predictions with the smoke detection method were better than the temperature approximation method over the range of fire scenarios examined. Predictions of smooth ceiling experiments were generally better than the beamed ceiling experiments. Keywords: Smoke detection, Fire models, CFAST, Alarm prediction
1. Introduction Predicting smoke detector activation is often fundamental to performance-based design of building fire safety. While fire detection system installations are usually prescribed in building codes, notification from the fire detection system is often the starting point for egress analysis in design calculations. Activation time is also used to determine response time and supports the fire non-suppression probability * Correspondence should be addressed to: Thomas Cleary, E-mail: [email protected]
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Fire Technology 2020 analysis in nuclear power plants. Thus, given a set of design fires, accurately predicting smoke detector activations increases the validity of the design scenario outcomes. When it comes to predicting smoke detector activation there is a choice to be made from solving simplified algebraic equations, running zone fire models, or running CFD fire models which is driven by the user end needs and computational resources. Zone fire models still find favor with end users because of their relative simplicity and familiarity, and more recently where large data sets are needed to eva
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