Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item The role of adsorbed phase volume on the thermodynamics of supercritical methane adsorption on microporous carbon(Montana State University - Bozeman, College of Engineering, 2019) Remington, Emily Lynn; Chairperson, Graduate Committee: Sarah L. Codd; Nicholas P. Stadie (co-chair)Experimental determination of the isosteric heat of adsorption at the fluidsolid interface is an important undertaking in the chemical sciences since this fundamental thermodynamic quantity is closely related to the binding energy of the adsorbate on the adsorbent surface. The usual methods employed to calculate the isosteric heat from measured gas adsorption equilibria, however, are unsuited to the treatment of adsorption under a high-pressure adsorptive fluid (where the difference in molar volume between the two phases becomes small and depends significantly on that of the adsorbed phase). Herein we employ a methodological approach to the thermodynamic analysis of adsorption up to high pressures in the supercritical regime, with a specific focus on methane adsorption on microporous carbonaceous materials at T/T c between 1.25-2.75 and P/P c up to 2. The aim is to achieve a meritorious description of the thermodynamics of the adsorbed phase with as few independent parameters as possible. We compare several simple approaches to estimating the molar volume of the adsorbed phase, and demonstrate that among the several well-known sources of error involved in the isosteric approach, that attributed to molar volume estimations is not itself prohibitive to achieving meritorious results. We contrast the isosteric approach with that of the so-called 'isoexcess' methodology, and thereby shed new insights into the key role of the finite adsorbed phase volume in assessments of adsorption thermodynamics.Item The influence of solar radiation in snow on near surface energy balance in complex topography(Montana State University - Bozeman, College of Engineering, 2015) Curley, Patricia Glatz; Chairperson, Graduate Committee: Edward E. AdamsOnce snow reaches the ground it begins to metamorphose. It may thermodynamically metamorphose into a weak layer, which could lead to slab avalanches. The effect of local weather, topography and snow depth on this process can be estimated with a first principle one-dimensional energy balance equation in conjunction with a mesh topographic model. To do this, the commercially available software RadThermRT (RTRT) was used. This work focused on the effect of solar radiation on surface and near surface temperatures as well as the effect of varying the resolution of the topographic model. Three main components were completed. A solar radiation attenuation coefficient was developed based on wavelength, snow grain size, and snow density from published literature. Then this code was used to calculate results from twelve hour radiation recrystallization experiments carried out in a cold lab with homogenous snow. Finally, conditions for metamorphic events were calculated and qualitatively affirmed in the field at the Yellowstone Club ski area. This work demonstrates that solar radiation has a significant effect on the surface temperature as well as temperature at depth, and weak layer metamorphic events can be modeled. Based on RTRT calculations with 100 kg/m 3 density snow, shortwave radiation increased the temperature at the surface by approximately 5°C and at 2.5 centimeters below the surface by 9°C. During the 2013/14 and 2014/15 seasons, diurnal weather data was collected at the Yellowstone Club ski area, and events around the mountain were recorded with the help of the Yellowstone Club ski patrol and thermal imaging. For radiation recrystallization events, strong positive-knee-shaped gradients were successfully modeled on congruous slopes. RTRT and measured results agreed within 2°C. Spring events were also calculated and measured but there were some false positives. In the winter, spatial variation over the mountain was greater than in the spring where snow temperatures were ubiquitously high. Overall, this work is useful for modeling snow surface and depth temperatures to project the occurrence of weak layer metamorphic events. Going forward from this work, projecting longevity of weak layers and including a layer history of the snow would further improve the model.