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Onsager Heat of Transport at the Liquid-Vapour Interface of Glycerol-Water SolutionsJames, Ronald Arthur January 2007 (has links)
The Onsager heat of transport, Q*, has been measured for water vapour above glycerol-water solutions (75 % to 94.5 % glycerol) over a temperature range of -46 to -32 ℃. For solutions of concentrations 80 % and above, Q* varied from 5.41 kJ mol-1 ± 0.97 to 17.37 kJ mol-1 ± 2.61, consistent with previous results for aniline and n-heptanol. The dissociation of glycerol-water complexes was not rate determining, as was the case for sulfuric acid-water solutions, and therefore the glycerol-water system is a better two component system analog for comparison with the CO2-water system than the sulfuric acid-water system.
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Onsager Heat of Transport at the Liquid-Vapour Interface of Glycerol-Water SolutionsJames, Ronald Arthur January 2007 (has links)
The Onsager heat of transport, Q*, has been measured for water vapour above glycerol-water solutions (75 % to 94.5 % glycerol) over a temperature range of -46 to -32 ℃. For solutions of concentrations 80 % and above, Q* varied from 5.41 kJ mol-1 ± 0.97 to 17.37 kJ mol-1 ± 2.61, consistent with previous results for aniline and n-heptanol. The dissociation of glycerol-water complexes was not rate determining, as was the case for sulfuric acid-water solutions, and therefore the glycerol-water system is a better two component system analog for comparison with the CO2-water system than the sulfuric acid-water system.
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Variability of Water Storage and Instream Temperature in Beaded Arctic StreamsMerck, Madeline F 01 May 2011 (has links)
The purpose of this study is to investigate variation in water export and instream temperatures throughout the open water season in a beaded Arctic stream, consisting of small pools connected by shallow chutes. The goals are to better understand heat and mass movement through these systems, how this may impact chemical and biological processes, and the resulting shifts with changes in climate. This is accomplished by first examining the extent and variability of water storage and export through qualitative analysis of observational data. Further, heat fate and transport is examined through development of an instream temperature model. The model formulation, a simple approach to model calibration and validation, and information regarding residence and characteristic times of different pool layers are presented. Using temperatures measured at high spatial resolution within the pools and surrounding bed sediments as well as other supporting data (e.g., instream flow, specific conductivity, weather data, and bathymetry), various types of storage within the pools, banks, and marshy areas within the riparian zone, including subsurface flow paths that connect the pools, were found. Additionally, data illustrated that some pools will stay stratified during higher flow periods under certain weather conditions. Through modeling efforts, the dominant heat sources were found to vary between stratified layers. It was also found that potential increases in thaw depths surrounding these pools can shift stratification and mixing patterns. These shifts can further influence mass export dynamics and instream water quality. Given the amount and different types of storage within these systems and the influence of stratification patterns on the residence times in the pools, Imnavait Basin and similar beaded Arctic watersheds will likely experience delayed export of nutrients that are limiting in most Arctic systems.
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The Onsager heat of transport at the liquidvapour interface of p-tert-butyltolueneBiggs, Georgina Aimee January 2007 (has links)
The Onsager heat of transport for p-tert-butyltoluene was measured, as part of a series of preliminary experiments towards the determination of the importance of temperature gradients on the air-sea flux of carbon dioxide. The results presented in this thesis imply that the temperature gradient is a major contributor to the magnitude of the air-sea flux. The heat of transport has been measured for the p-tert-butyltoluene system by measuring stationary-state pressure changes for known temperature differences on the vapour side of the interface. At the pressure ranges used the number of mean free paths was always outside the Knudsen zone, but the values of Q* were approximately 100 % of the latent heat of vaporisation. Departures from linearity of plots of P against ΔT are attributed to temperature jumps at the surface of the dry upper plate. Both the results taken for p-tert-butyltoluene and the earlier results for water from this laboratory fit to a Type III BET isotherm, where the c parameter is not constant. They also reveal the importance of the temperature gradient in determining the value of the thermal accommodation coefficient, and provide a new method of measuring thermal accommodation coefficients for a variety of surfaces and vapours
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The Onsager heat of transport at the liquidvapour interface of p-tert-butyltolueneBiggs, Georgina Aimee January 2007 (has links)
The Onsager heat of transport for p-tert-butyltoluene was measured, as part of a series of preliminary experiments towards the determination of the importance of temperature gradients on the air-sea flux of carbon dioxide. The results presented in this thesis imply that the temperature gradient is a major contributor to the magnitude of the air-sea flux. The heat of transport has been measured for the p-tert-butyltoluene system by measuring stationary-state pressure changes for known temperature differences on the vapour side of the interface. At the pressure ranges used the number of mean free paths was always outside the Knudsen zone, but the values of Q* were approximately 100 % of the latent heat of vaporisation. Departures from linearity of plots of P against ΔT are attributed to temperature jumps at the surface of the dry upper plate. Both the results taken for p-tert-butyltoluene and the earlier results for water from this laboratory fit to a Type III BET isotherm, where the c parameter is not constant. They also reveal the importance of the temperature gradient in determining the value of the thermal accommodation coefficient, and provide a new method of measuring thermal accommodation coefficients for a variety of surfaces and vapours
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Water, Heat and Solute processes in Seasonally frozen Soils : Experimental and Modeling StudyWu, Mousong January 2015 (has links)
Soil freezing and thawing is of importance in transport of water, heat and solute, which has coupled effects. Solute type and solute content in frozen soil could influence the osmotic potential of frozen soil and decrease freezing point, resulting in differences in soil freezing characteristic curves under various solute conditions. Prediction model provides an approach for estimating soil freezing characteristic curves under various water and solute conditions based on soil freezing characteristic curve obtained at certain water and solute conditions. Water, heat and solute transport in seasonally frozen soil is a coupled process strongly linked to evaporation and energy balance of soil surface. High solute content and shallow GWTD provide good conditions for water and solute accumulation in surface layer, which would result in more evaporation during thawing. Also, high solute content in upper layer would cause more liquid water to exist in upper layer, which may enhance evaporation during freezing period. Obvious increase in cumulative evaporation amount was detected for frost tube experiments, 51.0, 96.6, to 114.0 mm when initial solute content increased from 0.2%, 0.4%, to 0.6%, and initial GWTD of 1.5 m. Similar trends were observed for other GWTD and solute treatments. Water and heat transport simulated by the CoupModel combined with GLUE calibration showed good performances, when constrained by certain criteria. Uncertainties were investigated using ensemble of modeling results. Simulated energy partitioning showed intensive oscillations in daily courses during soil freezing/thawing periods and strongly influenced the stability of energy system on surface of soil. The study demonstrated the complexity in water, heat and solute transport in seasonally frozen soil, and the necessity of combining experimental data with numerical model for better understanding the processes as well in decision making for irrigation district water resources management. / 土壤冻融过程对于水热及溶质的运移具有十分重要的影响,并对于寒旱区水文过程的研究有着深远意义。在冻土中,溶质的种类及溶质含量会对土壤溶质势产生影响,并导致冰点的降低,进而影响土壤冻结曲线的变化。本研究通过建立含盐冻土冻结曲线的预报模型,有效地利用一定水盐试验条件下的冻结曲线对未知条件下的冻结曲线进行预测,进而为数值模型实时根据土壤水盐条件获得准确的液态含水量与温度的关系时提供了可行的方法。冻融土壤中的水热盐运移过程与地表的水热平衡有着密切联系,进而影响冻融土壤蒸发过程。试验研究表明,高溶质含量及浅埋深地下水条件为地表的蒸发提供了便利条件,因为高溶质含量土壤冰点降低,同一负温条件下的液态含水量增大,为蒸发提供了可利用水分;而浅埋深地下水对冻融期水盐的表聚提供的方便,进而有助于融化期地表水分的大量蒸发及下层土层水分的大量向上补给。例如,当地下水初始埋深设置在1.5 m时,对于初始含盐量分别为0.2%,0.4% 和0.6% g/g的冻融试验组,冻融期累积蒸发量分别为51.0,96.6和114.0 mm。同样的增加趋势在其它初始地下水埋深设置试验组里也被验证,且初始地下水埋深越浅,累积蒸发量也越大。CoupModel 与GLUE相结合的方法能够有效地根据实测数据对模型进行率定并经过筛选后得出较好的模拟结果集合。通过对筛选的模拟输出集合的不确定性分析,对模型模拟过程的不确定性有了很好的了解。模拟的地表能量分配过程显示,地表能量的日变化过程较为剧烈,并且对地表能量平衡系统的稳定性产生了显著影响。研究通过试验与模拟相结合的方法,展示了季节性冻融土壤中水热盐耦合运移过程的复杂性,同时也表明利用试验取样与数值模型相结合的方法研究冻融土壤中水热盐运移过程的必要性,并为高效的水资源管理决策的制定提供了有效的手段。 / <p>QC 20150518</p>
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