Study of Dynamic Dielectric and Thermal Properties of Sundari Wood Under Different Salinity and Humidity

Abstract

Sundari wood is very useful as a construction material. Its physical properties were not well studied. Thermal conductivity and dynamic dielectric properties of Sundari wood have been studied for their dependence on salinity and thickness. Drying quality of most wood products is mainly depends on the distribution of moisture content of different slices, such as the humidity of environment, the temperature effect from the cutting slices, dielectric constant and dielectric loss, etc. The error associated with sensors when used to estimate relative humidity does not exceed ± 12% except when relative humidity increases with increasing salinity at the rate in excess of ± 2% per hour. The moisture content of the samples, in the form of small disc, has been varied by immersing the specimens in to water and the moisture content of the Sundari wood slice has been determined from the difference of weight of the treated samples and the dry samples. The same procedure has been applied to induce salinity in the specimen, where saline solution of different strengths was used. The dielectric constant was found to increase with increasing moisture content and also increases with increasing saline concentration. The introduction of solutions into the wood matrix increases with increasing dielectric constant by a factor of two. This increase is quite expected due to the presence of additional ions in Sundari wood and its composite nature. Dynamic dielectric permittivity, loss factor and a.c conductivity have been measured as a function of frequency in the range from 1 kHz to 13 MHz at room temperature. The dielectric permittivity, loss factor and real part of the conductivity of the Sundari wood were Ibund to be about 5.8 to 0.68, 5.28 to 0.04 and 12.64x10 9 to 24135.23x10 9 mho/cm, respectively, over the frequency range from 1 klIz to 13 MHz. These results also varied with thickness of the specimen and its saline content. From the conductivity results it is important to note that the conductivity in the high frequency is very sensitive and precisely .The conductivity varies appreciably with a small variation of parameters. The thermal conductivity of Sundari wood has been determined using a technique which is a modification of Lee's method in order to avoid the error due to the air gap between the specimen and the conducting disc used as heat source and heat sink. The effective temperature of Sundari wood samples at which thermal conductivity has been measured, was altered by changing the temperature of the heat source. Thermal conductivity of these samples increases with increasing salinity. The thermal conductivity has also been observed to increase with the increasing in the applied voltage heat the sample to the same temperature. Results are explained interms of the additional contribution from the water molecules and ions and also interms of the transfer of few eiectrons from the valence band to the conduction band which acts as the thermal energy carrier.