Overview
ISO 14934-2:2013 - Fire tests - Calibration and use of heat flux meters - Part 2: Primary calibration methods describes primary calibration procedures for total hemispherical radiometers and total heat flux meters used to measure radiant heat flux in fire testing. The standard specifies three primary methods - the Vacuum Black-Body Cavity (VBBC), the Spherical Black-Body Cavity, and the Variable-Temperature Black-Body (VTBB) - designed to provide traceable irradiance levels while minimizing convective heat-transfer effects during calibration. Note: in service these instruments measure a combination of radiant and convective heat transfer, and the convective component depends on meter design, orientation, ambient flow/temperature and cooling water temperature.
Key topics and requirements
- Scope and instruments: Calibration of total hemispherical radiometers and total heat flux meters (examples: Schmidt‑Boelter thermopile and Gardon foil types).
- Three primary methods:
- VBBC (method 1): evacuated black‑body cavity; reduces convection by lowering cavity pressure (≈ 0.5 Pa to 2 Pa). Suitable for meters up to 50 mm housing diameter and calibration range ~2 kW/m² to 70 kW/m².
- Spherical black‑body (method 2): high‑uniformity spherical furnace with downward aperture to minimize convection; irradiance tied to controlled furnace temperature.
- VTBB (method 3): uses electrical substitution radiometry (ESR) and a substitution procedure to minimize convective differences between standard and test meter.
- Calibration essentials:
- Apparatus descriptions, detailed operating procedures (normative annexes), irradiance calculation methods, and data reduction procedures.
- Requirements for suitability of gauges, measuring range, meter condition prior to calibration.
- Uncertainty analysis: methods include following GUM principles (ISO/IEC Guide 98‑3) and accounting for convective contributions where relevant.
- Number of calibration levels, expression of results and required content of calibration reports.
- Normative and informative annexes: detailed operating procedures, irradiance calculation examples, drawings and guidance for operators.
Applications and users
- Calibration laboratories and national metrology institutes establishing traceable heat‑flux calibrations.
- Fire test laboratories and manufacturers of heat flux meters seeking primary calibration methods to support fire testing and product certification.
- Research institutions studying radiant heat transfer and instrument performance in fire environments.
- Regulatory bodies and standards developers requiring traceable irradiance measurements for fire safety tests.
Related standards
Keywords: ISO 14934-2:2013, heat flux meter calibration, primary calibration methods, VBBC, spherical black‑body, VTBB, radiant heat flux, convective heat transfer, electrical substitution radiometer, fire tests.
Open preview (PDF)Fire tests — Calibration and use of heat flux meters — Part 2: Primary calibration methods
