Department of Forest and Wood Science

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Browsing Department of Forest and Wood Science by browse.metadata.advisor "Ackermann, Pierre Alexander"

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    Measuring and modelling dynamic moisture loss of pulpwood during rail transport in South Africa
    (Stellenbosch : Stellenbosch University, 2022-11) Morkel, Russel George; Ackermann, Pierre Alexander; Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science.
    ENGLISH ABSTRACT: The unit of planning in the South African forest industry is volume (m3). The unit of trade and financial reporting for pulpwood, however, is weight (tonnes). As living trees invariably contain more water than wood, this disparity has necessitated a detailed understanding of moisture loss with age-after-felling, to better predict m3/tonne conversion factors (for yield estimation, forest valuation and stock control purposes). All moisture loss research to date, has been conducted in a static setting, where low-speed ambient winds come to the processed wood in a forested environment. No research has assessed the possibility of incremental weight loss induced by the slipstream of a fast-moving freight train. This is not necessarily an academic oversight, more a lack of context. Few countries rail large quantities of debarked, small diameter, wet pulpwood traded by weight. Furthermore, although natural airflow is a primary driver of moisture loss, its quantity and quality are uncontrollable, and its effect in a forest setting often inconsequential. The objective of this research was to measure and model the dynamic weight loss of wet pulpwood, during a 317 km rail journey, on one of the world's largest dedicated timber trains. The research included scaled wind-tunnel experiments and operational trials using a wagon-mounted continuous-weighing platform and mobile automatic weather station. The simplified and more controlled wind-tunnel simulations recorded a statistically significant 6.6% step-down (p<0.001) in the treatment payload weight caused by the slipstream of the train. The treatments lost 114% more moisture than the comparable static controls. Time, temperature, relative humidity, wind speed and wind temperature accounted for 87% of the weight loss of the hardwood treatments over the entire period. The complex and less controllable operational methods recorded smaller slipstream induced weight losses. The modernized operational method treatments lost on average 2.84% more than the static controls (a relative difference of 346%). The treatment regression models showed that time, temperature, relative humidity and wind accounted for between 86% to 96% of the variation in weight loss. The preponderance of nighttime travel (characterized by low temperatures and high relative humidity levels) limited the effect of the slipstream on incremental moisture loss.