Heat-flow meter method

BS EN 12664, 2001. Thermal performance of building materials and products. Determination of thermal resistance by means of a guarded hot plate and heat flow meter methods. Dry and moist products of medium and low thermal resistance,... 

Method 7B describes a heat flow meter method for the determination of the apparent" thermal conductivity. This is a much faster method of determining this property and is the usual method employed. It uses a heat flow meter as for example described in BS 874, 1973. Appendix C. An international standard. ISO 8301, 1991 [39]c. ists that defines the use of heat flow meters and the calculation of the heat transfer properties of specimens. The... 

The constant, k, is a material constant called the coefficient of thermal conductivity. It is the time rate of heat flow under steady-state conditions through a unit area and unit thickness per unit temperature gradient. Several methods for measuring thermal conductance are available, of which the guarded-hot-plate and heat-flow-meter methods are the most widely used. The most accurate method for plastics having thermal conductivities of 3.4 x 10 cal/(second)(cm)(°C) [1.4 W/m K] or less (most filled and unfilled polymers) is the guarded-hot-plate method as described in ASTM Cl77. A comparable method is described in ISO 8302. ... 

Guarded Heat-flow-meter Method. The previous two methods are absolute determinations of thermal conductivity, that is, all the quantities required for the application of equation 9 are measured directly. A widely used comparative method is illustrated schematically in Figure 6. This design is the basis of an ASTM procedure (22) it is characterized by a heat-flux transducer, a sensitive device that produces an electrical output proportional to heat flux. A number of configurations are available, each having certain advantages. 

ASTM C518, 2004. Standard test method for steady state thermal transmission properties by means of the heat flow meter apparatus. 

ASTM C 518-85 Standard Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus, 17 pp (Comm C16)... 

The direct measurement of the thermal conductivity or X factor is one of the most common ways to check the quality of a vacuum panel. Several test methods are available, such as the heat flow meter [45], guarded hot-plate and guarded-calibrated hot box [46, 47] procedures, which measure the heat transferred under steady state conditions through the sample whose surfaces are kept at two different given temperatures. 

Heat flow meter test results generally agree well with those generated hy absolute methods. The technique, which is easier to use and is a universally recognised standard test procedure [45], is also usable either for high accuracy measurements to support VIP analytical modelling/development or for fast tests for QA/QC programs. 

Guarded heat flow meters are variants on the guarded hot-plate technique, which utilize a heat flow meter to measure the heat flux. These techniques are comparative in nature because a reference material is needed to calibrate the heat flux meter. They utilize smaller samples and are thus able to equilibrate faster, improving the versatility of the guarded hot-plate method. 

For the thermal conductivity measurement, sample C and pine PS foam sample were measured by the method described above. It was found that it took 33 minutes for a temperature increase from 33.2 to 34.5°C for pure PS sanple and 40 minutes for sample C. This indicates that with the addition of activated carbon, the thermal conductivity of foam samples decreases. Further experiments by heat flow meter (FOX 200, LaserComp) will be conducted to investigate the effect of activated carbon and moisture. 

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