Development And Evaluation Of Several Modules Of Thermal Conductivity Measuring Instrument Based On TPS Method

Thermal conductivity is a key thermo-physical parameter that characterizes the thermal and adiabatic properties of materials.Its accurate measurement is of great significance in food processing,building energy conservation,electronics industry and aerospace.Transient plane source method is one of the transient methods for measuring the thermal conductivity of materials.It has the advantages of short measurement time,wide measurement range and good adaptability to different kinds of samples.At present,the thermal conductivity measuring instrument developed abroad based on TPS method is already mature,and it is widely favored by many users internationally,while there are still no such mature instruments within our country.After several years of R&D,our research group has developed the TPS-based standard module,which is a function for measuring isotropic bulk samples.Currently,with this standard module,isotropic bulk samples with higher thermal conductivity(larger than 0.1 W/m K)can be measured with good accuracy,but for samples with lower thermal conductivity,the accuracy is still rather poor.Therefore,the problems existed in the our current-version TPS instrument are:(1)some other functions for the test of anisotropic samples,single-sided samples,liquid samples,have not been developed;(2)a special function for the test of low thermal conductivity material should be developed in order to improve the measurement accuracy for low thermal conductivity materials Base on the above analysis,for the improvement of the performance and application range of the current TPS instrument,this thesis focuses on the development of several measurement modules,including the low-thermal-conductivity module,the anisotropic module,the single-sided module and the liquid module.The main contents of this thesis are as follows:1.The basic concepts and main measuring methods of thermal conductivity were introduced in this part.Then the research status of TPS method at home and abroad was expounded,and the research purpose and contents of the thesis were put forward.2.For the low-thermal-conductivity module,the main sources of the measurement error was analyzed,and the corresponding correction model was proposed.Then the influence of the heat loss through the probe leads on the measurement was studied in detail,and the thermal conductivity of four different insulation materials were respectively measured under the ideal model and the corrected model.The results showed that the accuracy of the thermal conductivity of insulation materials was improved by about 4% after correcting the error.3.For the anisotropic module,firstly,the basic principle for measuring the thermal conductivity of anisotropic materials by TPS method was introduced,and the theoretical temperature rise model of the probe was deduced.Then,the program algorithm of the anisotropic measurement module was established.Finally,the thermal conductivity of stacks of silicon steel sheets and three kinds of wood were measured,and the results were analyzed and evaluated.4.As to the single-sided module,based on the single-sided measurement principle of the transient hot strip method,the temperature rise model of the probe of TPS single-sided method was established.Then,the program algorithm was designed.Finally,the test performance of the module was evaluated by comparing with the standard module.5.As to the liquid module,a new probe and sample holder for measuring the thermal conductivity of liquids were designed,and the resistance temperature coefficient of the new designed probe was calibrated.And by measuring the thermal conductivity of a large amount of different kinds of liquids,the performance of the liquid measuring device designed in this thesis was evaluated.6.The main work of this thesis was summarized in this part,and some suggestions for improvement were put forward.