Assessment of Uncertainties for the NIST 1016 mm Guarded-Hot-Plate Apparatus: Extended Analysis for Low-Density Fibrous-Glass Thermal Insulation.
Assessment of Uncertainties for the NIST 1016 mm
Guarded-Hot-Plate Apparatus: Extended Analysis for
Low-Density Fibrous-Glass Thermal Insulation.
(777 K)
Zarr, R. R.
NIST TN 1606; NIST Technical Note 1606; 55 p. February
2009.
Keywords:
thermal insulation; building technology; guarded hot
plate; thermal conductivity; thermal resistance;
uncertainty; transmission; mathematical models;
thickness; heat flow; temperature differences
Abstract:
An assessment of uncertainties for the National
Institute of Standards and Technology (NIST) 1016 mm
Guarded-Hot-Plate apparatus is presented. The
uncertainties are reported in a format consistent with
current NIST policy on the expression of measurement
uncertainty. The report describes a procedure for
detennination of component uncertainties for thermal
conductivity and thermal resistance for the apparatus
under operation in either the double-sided or
single-sided mode of operation. An extensive example for
computation of uncertainties for the single-sided mode
of operation is provided for a low-density fibrous-glass
blanket thermal insulation. For this material, the
relative expanded uncertainty for thermal resistance
increases from 1% for a thickness of 25.4 mm to 3% for a
thickness of 228.6 mm. Although these uncertainties have
been developed for a particular insulation material, the
procedure and, to a lesser extent, the results are
applicable to other insulation materials measured at a
mean temperature close to 297 K (23.9 DGC, 75 OF). The
analysis identifies dominant components of uncertainty
and, thus, potential areas for future improvement in the
measurement process. For the NIST 1016 mm
Guarded-Hot-Plate apparatus, considerable improvement,
especially at higher values of thermal resistance, may
be realized by developing better control strategies for
guarding that include better measurement techniques for
the guard gap thermopile voltage and the temperature
sensors.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899