The NIST 20 MW calorimetry measurement system for large-fire research

Abstract

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.

The thermal character of a 1 m methanol pool fire

“…The effect of ambient convective currents on the fire was minimized by closing all inlet vents in the lab. The exhaust consisted of a large round duct (1.5 m diameter) located 6.0 m above the floor [14]. The smallest exhaust flow possible (about 4 kg/s) was used, helping to avoid perturbations (such as flame lean) and minimizing the influence of the exhaust on fire behavior.…”

“…u(Q̇) is the combined uncertainty of heat release rate measured from the calorimetry which is 3.4 % in Ref. [14]. Q̇r, fit was 39 kW ± 2.94%.…”

“…As expected, the ideal heat release rate agrees well with the measured calorimetric heat release rate since the combustion efficiency is expected to be nearly 1.0. The expanded uncertainty of heat release rate measurement using the calorimetry was 7 % based on repeat measurements, the results and methods described in [14], and additional natural gas calibrations at 250 kW. The heat release rate from the calorimetry was 256 kW ± 45 kW.…”

Full-Scale Experiments to Demonstrate Flammability Risk of Residential Upholstered Furniture and Mitigation Using Barrier Fabric

“…Detailed information on the NFRL calorimetry measurement system is provided by Bryant and Bundy [31].…”

Measuring Three-Dimensional Temperature Distributions in Steel–Concrete Composite Slabs Subjected to Fire Using Distributed Fiber Optic Sensors

“…The total expanded uncertainties (coverage factor of 2) for the material temperature and gas temperature measurements are ±6.2% and ±14.7% of the reading, respectively. The total expanded uncertainty for the burner heat release rate is less than ±2.4% [ 34 ]. The distributed optic fiber sensors have an estimated expanded uncertainty of ±11.2% of the reading.…”