Microwave method of nondestructive control of thermal characteristics of building material

A contactless microwave method and corresponding information-measuring system (IMS) for determination of thermal and physical characteristics thermal and physical characteristics (TPH) of building materials and products are considered. The method provides microwave heating of the samples by exposing the surface of the sample to electromagnetic field of the microwave range through a circular area, as well as temperature control of the environment and in the center of the circle. A microprocessor-based IMS system developed for practical implementation of the proposed method provides determination of the thermal and physical characteristics of the objects under study with high accuracy. A possibility of on-line automatic control of all operations of the thermophysical experiment, as well as the control of heat losses to the environment from the surface of the circular spot subjected?? to microwave heating and the timely correction of those losses to improve the accuracy of the final results is a distinctive feature of the system. Analysis of the calculated and experimental data showed that the elimination of the impact of the contact thermal resistance arising between the surfaces of the sample and the heating element on the determination of the desired thermal characteristics increases the accuracy of the method by 6— 8 %. The developed method allows more accurate determination of the thermal characteristics compared to other known techniques and can be used in practice of general thermal measurements and thermal engineering for construction.

thermal conductivity, thermal diffusivity, thermal activity, microwave heating, microprocessor system, thermal engineering for construction

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