- Author
-
Womeldorf, C. A.
- Title
- BFRL's Convective Calibration Facility for Total Heat Flux Gauges. BFRL Fire Research Seminar. VHS Video.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Report
-
Video,
February 22, 2000,
- Keywords
-
measuring instruments
|
heat flux
- Abstract
- Heat flux gauges measure energy flow in many different applications: the radiant flux from a fire; the thermal efficiency of a fire fighter's gear or building insulation; the aerodynamic heating of an airfoil; even the cooling of electrical components in a computer. Until recently the only standard NIST calibration has been from a blackbody source providing a radiant flux up to 80 kW/m2. Because many sensors are used in mixed radiation and convection environments, the uncertainty associated with convection can be significant. Recognizing this, over the past four years BFRL has developed a convective heat flux facility to assess a sensor's convective response. The facility consists of a small wind tunnel that produces a two-dimensional laminar boundary layer across a heated isothermal copper plate. A test sensor is mounted flush alongside a reference in the plate to measure the heat leaving the plate. Convective calibrations up to 5.00±0.13 kW/m2 are possible, with a heat transfer coefficient up to 45 W/m2K. This presentation describes the facility with its second-generation heated plate and provides an analysis of the system uncertainty. Redundant references, improved sensor heating and mounting, improved reference isolation, and a minimized radiation component have reduced the combined relative expanded uncertainty of the reference to ±2.5%. The benefits of an embedded temperature sensor in the gauge surface are described. The facility is available for comparative calibrations and heat transfer studies.