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NIST 3 Megawatt Quantitative Heat Release Rate Facility.


pdf icon NIST 3 Megawatt Quantitative Heat Release Rate Facility. (1458 K)
Bryant, R. A.; Ohlemiller, T. J.; Johnsson, E. L.; Hamins, A.; Grove, B. S.; Guthrie, W. F.; Maranghides, A.; Mulholland, G. W.

NIST SP 1007; 81 p. December 2003.

Keywords:

heat release rate; oxygen consumption calorimetry; response time; uncertainty

Abstract:

The 3 Megawatt Heat Release Rate Facility was developed at 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. The facility is capable of measuring heat release rates in the range of 0.10 to 3.0 MW including brief peaks as high as 5 MW. 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. Key features of the design and fabrication of these systems are presented including detailed schematics and the rationale for the choices made. Transient response and gas dispersion in the sampling system, sampling from a non-uniform duct flow, and making accurate total flow measurements using bi-directional probes are dealt with in the design. The design of a natural gas burner for measurement confirmation, including the special flow control and flow metering capabilities, is presented. The general design of the software allowing the display of nearly real-time heat release rates with corrections for sampling/instrumental delay and response times is also described.