The guarded hot plate apparatus has the capability to generate precise and measurable unidirectional heat flow on the measurement plate.The calibration method of two foreign precision heat flow meters and two domestic heat flow meters was investigated using a high-performance single-sample guarded hot plate apparatus developed by National Institute of Metrology of China.A 40 mm thick rock wool was used as the thermal resistance insulation material.Three different working conditions were designed:placing the test surface of the heat flow meter close to the measuring plate(Condition 1),placing it in the middle of the rock wool(Condition 2),and attaching it to the cold plate(Condition 3).The sensitivity coefficient C of each heat flow meter was measured.Under Condition 2,the measured value of C showed the smallest deviation from the indications of the two foreign heat flow meters,with a relative deviation of about 7%.The experimental results of all four heat flow meters consistently showed that Condition 2 had the lowest C value,while Condition 1 had the highest.Analysis indicated that the thermal conductivity of the organic solid material constituting the heat flow meter was greater than that of rock wool.Additionally,when in contact with the measuring plate or the cold plate,the resistance of the heat flow passing through the heat flow meter unit was smaller than that passing through the rock wool,resulting in non-unidirectional distribution of the heat flow and uneven distribution of the heat flow on the contact surface,the heat flow meter unit absorbed more heat flow,leading to an overestimation of the C value.
thermal measurementguarded hot plate apparatusthermal resistance heat flux meterheat fluxcalibration
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