Development Of A Thermal Conductivity Measurement Instrument Based On A Modified Model Of Transient Plane Source Method

Currently, energy saving and environmental protection have been widespreadconcerned in fields of construction, petroleum, chemical, life, etc. One of importantimplementation ways is to use insulation materials. Insulation material is regarded asthe fifth largest energy, following the coal, oil, natural gas and nuclear energy.Coefficient of thermal conductivity is one of the important thermo-physicalparameters to evaluate the thermal conductivity of insulation materials. The smallercoefficient of thermal conductivity of the materials is, the better its insulationperformance is. There are two kinds of experimental measurement methods of thethermal conductivity, steady-state methods and transient-state methods. Steady statemethods, including the guarded hot plate method, heat flow method and so on,although the measurement accuracy is higher, but they are limited in manyapplications because of the long test time, the small measurement range, fordemanding test sample, etc. Transient plane source, one of transient-state methods,with advantages of short test time, the large measuring range, simple samplepreparation, has been widespread concerned. Currently, there are already matureproducts of thermal conductivity measuring instruments based on transient planesource abroad, while no similar products at home. Therefore, the development of athermal conductivity measuring instrument based on transient plane source methodnot only can fill the gaps, but also promote the development of domestic technologicalprogress and the cause of energy conservation and emission reduction.The purpose of this subject is to analyze and compensate the influencing factorsthat affect the thermal conductivity measurement accuracy based on the measurementprinciple of transient plane source, thereby to propose a new correction measurementmodel and develop a thermal conductivity measurement instrument based on transientplane source method.The main content of this paper includes:1. The concept of thermal conductivity was introduced and common methods ofmeasuring thermal conductivity at home and abroad were summarized and compared.Then the development status of the transient plane source thermal conductivitymeasurement instruments at home and abroad and the problems of transient plane source were described.2. The transient plane source measurement principle was introduced in detail; onthis basis, the main factors that impact transient plane source measurement accuracy,the time delay, the heat capacity of the probe, resistance change of the probe, etc,were analyzed and compensated, a new correction model of the temperature risemeasurement of the probe was proposed, which provided a theoretical basis for thedevelopment of higher-performance thermal conductivity detector.3. The detailed design of the thermal conductivity measurement instrument basedon transient plane source was discussed; two specifications of new sensor probes weredesigned and made; the programmed voltage source hardware circuit and the dataacquisition system were developed; the measurement and control software based onthe Labview8.6in the PC was written, realizing functions of parameter control, datacollection, analysis and processing, and calculation of the coefficient of thermalconductivity; finally a measuring instrument prototype was built.4. The probe calibration experiments, related circuit test experiments, instrumentcalibration and calibration experiments, and thermal conductivity coefficientmeasurement experiments of three kinds of materials were made and the experimentaldata were analyzed. Experimental results showed that, reproducibility of theinstrument was good, and measurement accuracy was improved in the new correctionmodel of compensating the impacts of three factors; the sources of error wereanalyzed.5. The work this paper completed was summarized, and also the problems and thefuture research need to be improved were pointed out.