In Chapter 1, a numerical computer technique is developed to determine radiation view factors between planar surfaces whose geometry is sufficiently regular so as to be defined by algebraic equations. This technique does not require spherical, cylindrical or rectangular symmetry, although such symmetries may be exploited when they exist. Once the essential geometric problem is formulated, enough generality can be built into the solutions so that certain "new" configurations, derived from translations or rotations of one surface relative to the other, can be solved as a matter of course. In Chapter 2, a model of bare soil evaporation is tested against measured flux from lysimeters obtained in the Peace River region of British Columbia and Alberta. Hydraulic diffusivity characteristics, measured from separate, adjacent field samples, were used in the model. Certain procedural difficulties in the measurement of hydraulic diffusivity are examined in detail, and recommendations for improvement are made. The degree to which evaporation simulation agrees with measured flux is discussed. / Land and Food Systems, Faculty of / Graduate

A study is described on the occurrence of wetwood in black cottonwood, found in the Lower Fraser Valley of British Columbia, Canada. Wetwood first appears when trees are 8 to 10 years old, and in 12 year and older trees, wetwood is always present. Further extension of wetwood is similar to that of a normal heartwood, A large number of microorganisms with different 0₂ requirements (i.e., aerobes as well as facultative and obligate anaerobes) were found in the wetwood. Wood-destroying fungi were absent in the wetwood. In the majority of the black cottonwoods examined, very low 0₂ concentrations (<0.1% or microaerobic conditions, detected by a Field-lab 0₂ analyzer) were found in the wetwood during the summer. Generally the 0₂ concentration increased during the winter while the reverse was true for CO₂ (detected by gas chromatography). CH₄ was also present, but only in small quantities, in most trees. Mechanical wounding of wetwood resulted in an increase in the 0₂ concentration and decrease in the CO₂ and CH₄ concentrations. However, sealing of the wound re-established the original gas composition. Presumably the microbial flora of wetwood is primarily responsible for the microaerobic conditions. The ability of 2 wood-destroying fungi (Polyporus delectans Peck and Ganoderma applanation [Pers.] Pat.) to cause a weight loss in wood under microaerobic and aerobic conditions (10 weeks incubation each) was determined, using a soil-block experimental technique, Microaerobic conditions prevented weight loss in wood (average 0.1%) and therefore wood decay, whereas under aerobic conditions, the average weight loss was 41.7%. Special characteristics of wetwood such as high pH (average 7.8) or high moisture content (approximately 160%) did not contribute significantly to the decay resistance. Also, microorganisms associated with wetwood showed no antagonism to the growth of wood-destroying fungi. Exposure of wood-destroying fungi to microaerobic conditions subsequent to aerobic conditions arrested their growth and ability to cause weight loss. On the other hand, exposure of these fungi to aerobic conditions following the microaerobic conditions, induced a significant weight loss in wood (average 10.9%), but it was considerably less than when the fungi were grown under aerobic conditions alone (average 41.7%). The 2 wood-destroying fungi survived 10 weeks exposure to microaerobic conditions, A 13 weeks exposure to anaerobic conditions (<0.002 % 0₂), however, resulted in the death of these, wood-destroying fungi. Eight wood-destroying fungi differed in their abilities to survive under anaerobic conditions; generally brown-rot fungi tolerated anaerobic conditions better than the white-rot fungi. Therefore, if anaerobic conditions exist in the tree trunks for long durations, some fungi (probably white-rot fungi) may die during that period while others (probably brown-rot fungi) may survive such an exposure and resume decay activity when 0₂ becomes available. These findings led to the concept that the microaerobic conditions found in the wetwood of black cottonwood may prevent the development of decay. / Forestry, Faculty of / Graduate

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Moisture transport in building materials is directly responsible for structural damage, as well as poor indoor air quality. For these reasons, the need to understand transfer mechanisms and predict moisture transport through building materials has increased over the last couple of decades. Although moisture diffusion phenomenon in the isothermal regime has been studied and explained extensively, there is no universally accepted model for predicting the moisture diffusion in a nonisothermal situation. Several diffusion models in the form of "Fick's Law" including ones based on gradients of water-vapor pressure, chemical potential of water, moisture concentration and activated moisture molecules have been proposed for predicting moisture diffusion through porous materials. However, the lack of reliable experimental results, resulting from the complexity of arranging accurate and repeatable measurement techniques and slow moisture movement, has prevented any model from being universally accepted. The present research addresses this modeling problem by evaluating current diffusion models through a series of experiments performed on oriented strand board (OSB), which is a wood-based material. The present experimental apparatus, developed over the last three years, was designed for the specific purpose of studying and developing an accurate method to measure moisture transfer properties in porous materials under nonisothermal conditions. The apparatus consists of a system of two environmental chambers capable of achieving a wide range of temperatures and relative humidities. Temperature and relative humidity can be independently controlled to within ±0.05°C and ±0.10 per cent R.H. of the set points. This apparatus is an alternative to the ASTM "cup method" which is limited to isothermal conditions and discrete relative humidities that correspond to those for various saturated salt-in-water solutions. Unlike the cup method, the relative humidity within the chambers is controlled by the direct removal and injection of distilled water. The system has forced recirculating flow which reduces the time to reach steady state. The new forced, direct control measurement procedure is denoted "ASHRAE FDC". The results obtained from the ASHRAE FDC experiments, show that moisture diffusion under nonisothermal conditions is governed by the gradient of the water-vapor pressure. The moisture transfer must cease when the diffusion potential is the same on both sides of the material for the validation of the diffusion model. The results show that the water-vapor pressure model meets this necessary and sufficient condition. Furthermore, a plot of the diffusion flux versus vapor-pressure difference was linear, within measurement uncertainty bounds. This observation infers that the permeability is approximately constant over the range of temperatures and humidities used in the investigation. During the ASHRAE FDC experimental procedure a small difference in the static pressure between the chambers was found. This pressure difference which was also observed in ASTM cup tests, is believed to be caused by concurrent air diffusion. The bulk flow of air governed by Darcy's equation balances the diffusion of air in the opposite direction as a result of the gradient in the partial pressure of (dry) air. The air permeability of an OSB specimen was measured and the results presented. The operation and accuracy of the apparatus was validated by comparing results from a series of isothermal tests to previously published results. The results obtained from the isothermal test allowed the permeability to be compared to results obtained from cup tests during the present investigation and to those previously published using the same method. Good agreement was found between the new data from both FDC and cup experiments and previously published results. / Master of Science

Woody biomass transportation costs and market values/costs are strongly correlated with the woody biomass moisture content. Properly managing moisture content can potentially lead to economic and environmental advantages in biomass energy markets. Good management requires accurate moisture content measurements. Therefore, availability of accurate, precise, reliable, and efficient tools to assess woody biomass moisture content is essential. In this study, six different tools (Fibre-Gen HM200, IML Hammer, Humimeter BLW, Timbermaster, Humimeter HM1 and Wile Bio Meter) were evaluated. The six tools employed three different measurement technologies; acoustic, conductance, and capacitance. Woody biomass samples were collected over one season (summer 2011) at three different locations in western Oregon (Corvallis, Dallas, and Clatskanie) for three softwood species and three hardwood species: Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), Ponderosa pine (Pinus ponderosa L.), western hemlock (Tsuga heterophylla (Raf.) Sarg.), hybrid poplar (Populus spp.), Madrone (Arbutus spp.), and Garryana Oak (Quercus garryana Dougl. ex Hook). Twenty 3-meter long log (20 to 400mm diameter) specimens were collected per species; 18 specimens were divided into two different treatments (open vs. covered), and the two remaining specimens were chipped. In addition, approximately 100 kilograms per species of hogfuel (limbs and tops) were collected and chipped. Moisture content measurements of logs, chips, and hogfuel were made regularly over a four month period. These data was used to develop multiple linear regression models for assessing the moisture content of the six species using the six tools. The major factors considered in the regression models were species (6), treatment (2), and tools (6). The data were also used to estimate the sample size needed for each tool. The best tool from each technology type was identified. The results generated from this study show that (1) none of the tools are accurate without calibration for different species, (2) the best model/tool combination could only explain about 80% of the variability in measurements, (3) further product development is required in some cases to ensure that the tools are robust for industrial application, and (4) there is a wide range in efficiency of the tools (i.e., 50 minute tool efficiency range). The Fibre-Gen HM200 and Wile Bio Meter were the most accurate, precise and efficient tools tested. The cost of transporting woody biomass from the forest to woody biomass plants is "optimized" when the moisture content drops to approximately 30% (wet basis). Validation of the models developed for three of the tools tested (Fibre-Gen HM200, Humimeter BLW and the Wile Bio Meter) indicates that the tools are accurate below 35% MC (wet basis). This suggests they could be used for making threshold transportation decisions, i.e., determining when to haul. / Graduation date: 2013

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