A difference technique to avoid interface errors in measurement of high-conductance thermal insulation

Clarke, Robin E; Shabani, Bahman; Rosengarten, Gary

doi:10.1177/1744259116637863

Cited by 2 publications

(2 citation statements)

References 6 publications

(7 reference statements)

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“…Also included are the earlier uninsulated case results, for which alternative buffers were used. Specimen thermal resistance has been calculated by removing the effect of the buffers, as well as their contact resistance, from the measured total (Clarke et al, 2016b). Results are averages of the top and bottom heat flows and show good agreement between the three sets of uninsulated panel measurements, with the mean values being very close and the standard deviations all being below 1%, even if the extremely similar results for the set of three earlier measurements have not been replicated.…”

Section: Thermal Measurement Resultsmentioning

confidence: 99%

“…The proposed thermal measurement setup incorporated flexible buffer materials at the interface between specimen and apparatus plates. We have previously described the use of this procedure in order to minimize errors due to contact resistance and to protect the apparatus plates when measuring hard, uneven materials (Clarke et al, 2016a(Clarke et al, , 2016b. Buffers can provide an additional facility in the case of non-uniform heat flow.…”

Section: Overviewmentioning

confidence: 99%

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Thermal analysis of a non-homogeneous insulating panel

Clarke

Shabani

Rosengarten

2017

Journal of Building Physics

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This article describes heat flow meter measurements and transient thermal modelling (using ANSYS) of a webbed, hollow-cored panel located between silicone sponge buffer materials chosen to provide boundary conditions comparable to standard surface coefficients. Panel surface temperatures were also measured at eight locations to record the thermal measurement as a temperature step function following isothermal stabilization. An uninsulated configuration was studied as well as cases with different levels of bulk insulation filling the panel cores. Measured and modelled temperature-time plots agreed well after corrections for web and airspace thermal conductivity. Modelled spatial variation in heat flow exceeded 200% for one insulated case but was only about 2% for the uninsulated panel. Modelled values for heat flux and overall thermal resistance agreed well with standard analytical calculations. However, heat flows indicated by the apparatus were consistently higher than the modelled and calculated values by up to 8%, expected to be due at least partially to specimen non-homogeneity. Nevertheless, results suggest a useful role for the apparatus in providing temperature measurement under controlled conditions, helping to validate thermal modelling as a potential alternative to hot box measurement for non-homogeneous assemblies.

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Section: Thermal Measurement Resultsmentioning

confidence: 99%

Section: Overviewmentioning

confidence: 99%

Thermal analysis of a non-homogeneous insulating panel

Clarke

Shabani

Rosengarten

2017

Journal of Building Physics

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Accurate contact resistance characterization for thermal conductivity measurement with the Heat Flow Meter method

Fustinoni

Vitali

Gramazio

et al. 2021

J. Phys.: Conf. Ser.

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A common method to measure the thermal conductivity of low-conductive materials is to impose a known temperature difference across the thickness of the specimen, and to measure the resulting heat flow once steady-state conditions are reached. In particular, international standards, i.e. ASTM C518 and ISO 8301, define the characteristics of the guarded Heat Flow Meter apparatus and its measurement procedure. However, the actual measured quantity is the overall thermal resistance, which is given by the series of the contact resistance between the specimen and the temperature-controlled clamps, and the resistance of the specimen itself. Thus, the contact resistance must be correctly quantified in order to retrieve an accurate measurement. To this end, common practices are either to rely on a database of known contact resistances for material classes, or to use the “double thickness” method, which allows to eliminate the contribution of the contact resistance by carrying out the measurement on two specimens of the same material, but different thickness. While the first method is rather useless for accurate and reliable measurements, especially of unknown or innovative materials, the latter works only if the contact resistances, and therefore the surface finish, are the same for every surface of the specimen set. This paper presents an analysis of the uncertainties associated with the evaluation of the contact resistance carried out on several samples, and proposes a method to reduce such uncertainties, i.e. by inserting elastic thermal pads of known thermal conductivity between the specimen and the instrument. The results of the validation of the method are also shown, with an analysis on the improvement of the measurement accuracy for specimens with high roughness and irregular surfaces, or with conductivities beyond the instrument declared range.

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A difference technique to avoid interface errors in measurement of high-conductance thermal insulation

Cited by 2 publications

References 6 publications

Thermal analysis of a non-homogeneous insulating panel

Thermal analysis of a non-homogeneous insulating panel

Accurate contact resistance characterization for thermal conductivity measurement with the Heat Flow Meter method

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