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ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Soil, Water & Air Resources Research » Research » Publications at this Location » Publication #276286

Title: Experimental methods of determining thermal properties of granite

item AKINYEMI, OLUKAYODE - University Of Agriculture - Nigeria
item Sauer, Thomas - Tom
item ONIFADE, YEMI - Federal University Of Petroleum Resources

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 11/24/2011
Publication Date: 12/9/2011
Citation: Akinyemi, O.D., Sauer, T.J., Onifade, Y.S. 2011. Experimental methods of determining thermal properties of granite. In: Blasik, M., Hanika, B., editors. Granite: Occurrence, Mineralogy and Origin. Hauppauge, NY: Nova Science Publishers. p. 131-141.

Interpretive Summary: Energy from the sun or heat from buried wires or pipes can warm the soil or other geologic materials. It's important to understand this process for agricultural production and for the design of efficient engineering applications. The key property is the thermal conductivity of the material, literally how effective the material is in transferring heat. In this study, two methods (block and needle) were used to evaluate the effect of adding a paste to the surface of the sensor to improve the heat transfer and reduce measurement error. The results show significant improvement in the performance of both methods when using this paste for measurements on granite rock. The results of this study are of interest to scientists involved with heat flow in natural environments as it demonstrates an improved method for making thermal property measurements for non-uniform surfaces.

Technical Abstract: Determination of thermal properties of granite using the block method is discussed and compared with other methods. Problems that limit the accuracy of contact method in determining thermal properties of porous media are evaluated. Thermal properties of granite is determined in the laboratory with and without application of thermal interface material TIM (Arctic Silver®) to study effects of thermal contact resistance. The thermal properties analyzer KD2 (line - source heat dissipation probe) is also used with and without TIM to measure thermal conductivity of the sample. Results from block method and KD2 analyzer, with and without TIM, are compared with standard values. Results indicate significant differences with consideration of thermal contact resistance. Thermal conductivity of the granite sample increased from 2.95 W/mK to 3.95 W/mK with the standard values (Kappelmayer & Haenel, 1974) for granite ranging from 2.0 and 7.0 W/mK. Volumetric heat capacity increased from 5.95 x 104 J/m3K to 7.17 x 104 J/m3K, thermal diffusivity increased from 0.412 x 10-4 m2/s to 0.67 x 10-4 m2/s while heat flux density increased from 2.63 x 10-1 W/m2 to 4.9 x 10-1W/m2. The difference in thermal conductivities with or without TIM is significant at (P > 0.05) which implies the effectiveness of the thermal interface material in reducing thermal contact resistance.