Dynamic modeling of thermal treatment of timber poles Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/cz30pw29d

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  • The temperature-time-location relationships during steam conditioning and pressure treatment of timber poles have been studied and mathematical models that take into account both the thermal properties of the poles and the parameters of the treatment process have been developed. Although much work has been previously done in this area, the standard "recipe" to sterilize wood fails to bring the interiors of large diameter wood poles to the required temperature. Recent studies (DOST, 1984; NEWBILL et al.,1988) indicated that commonly used charts, initially made by MACLEAN (1930,1932,1935,1952), predict a much faster temperature increase than actually measured. In all previous modeling work it has been assumed that during pressure treatment, operational changes result in step changes of the surface temperatures of the poles. However, from actual measurements it was found that when operating conditions changed, there was a time interval, ' time lag', during which no effect was observed on the surface temperature of the poles. These time lags are due to the thermal capacity of the process equipment and were found to be an important element for accurate prediction. The unknown parameters of several mathematical models were estimated by fitting experimental data taken from commercial scale equipment (NEWBILL et al., 1988) . The best model was discriminated among rival ones and the sensitivity and reliability of its estimated parameters were analyzed. Charts were made that show the minimum required steaming time that ensures that the center pith shall be heated to and remain above 150 °F (65.5 °C) for 2 hours according to the 1982 Rural Electrification Authority, REA, purchase specification.
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