An acoustic field is used to increase the critical heat flux of a copper boiling heat transfer surface. The increase is a result of the acoustic effects on the vapor bubbles. Experiments are being performed to explore the effects of an acoustic field on vapor bubbles in the vicinity of a rigid heated wall. Work includes the construction of a novel heater used to produce a single vapor bubble of a prescribed size and at a prescribed location on a flat boiling surface for better study of an individual vapor bubble s reaction to the acoustic field. Work also includes application of the results from the single bubble heater to a calibrated copper heater used for quantifying the improvements in critical heat flux.

Due to higher standards of living around the world, greater industries and larger infrastructures causes an increase of the global energy consumption. This harvest of energy puts a great stress on the global environment. With this development, it becomes increasingly important to utilize energy resources in the best possible way. Fans are components that are often used in the industry and in households. A common problem is that the fan is oversized. An oversized fan causes an excessive flow, which has to be adjusted in order to achieve the correct flow. This results in larger energy usage than the use of a properly sized fan. When designing a ventilation system calculations have to be made in order to determine the total pressure loss of the system. A series of simplifications are applied when using theoretical calculations. The total pressure loss of the system is assumed to be the sum of the pressure loss of each component in the system. This simplification ignores the separation distance that exists between each component. In reality, when air passes through the components, swirls emerge and a distortion of the velocity profile occurs. This causes large pressure losses due to friction losses occurring between the fluid and the pipe wall. The recommendation given in HVAC installations states that two 90 degree elbows should not be placed closer to each other than 6D (D representing the hydraulic diameter of the pipe) to thereby prevent large pressure drops. This dissertation will address the following questions: The recommendation in HVAC installations states that two 90 degree elbows should not be placed closer to each other than 6D (D representing the hydraulic diameter of the pipe) to thereby prevent large pressure drops. Does this recommendation conform with the empirical data obtained from conducted experiments?  What is the relation between the pressure drop and the separation distance between two 90 degree elbows? In this dissertation a series of experiments are conducted where pressure loss measurements are made within a circular ventilation duct with two integrated 90 degree elbows. Pressure loss measurements within a U-shaped piping system are made at five different fluid velocities each at 11 different separation distances between the two 90 degree elbows. By analysis of the obtained empirical data and by comparing it to the recommendation no results were found to validate this statement.

The objective of this study was to determine the safety impacts of right turn followed by U-turn movements (RTUT) at signalized intersections as well as median openings. RTUT movements are the most common alternatives to direct DLT movements(DLT). In order to achieve such data in a shorter amount of time, conflict analysis was chosen to be useful in this study as opposed to crash analysis. Additionally, data collection sites were divided dependent on certain geometric criterion and conflict data was recorded by the use of video recording equipment. Seven out the eleven conflict types used during the study were related to RTUT movements while the remaining observed conflicts were related to DLT movements. The safety comparison of right turns followed by U-turns to direct left turns at traffic signal sites indicated that DLT movements generated two times more conflicts per hour than RTUT movements. When the effects of traffic volumes have been taken into consideration, RTUT movements had a 5 percent higher conflict rate than DLT movements. At median opening sites, DLT movements generated 10 percent more conflicts per hour than RTUT movements. Furthermore, the other conflict rate, which takes the effect of traffic volumes into consideration, was 62 percent higher for DLT movements as compared to RTUT movements.Impacts of separation distance on safety of RTUT movements were investigated by a regression model. The model investigated impacts of U-turn bay locations and the number of lanes on major arterial on separation distance requirements. The model results indicated that U-turn bays located at signalized intersections and greater number of lanes on major arterials increases the minimum separation distance requirements. Finally, on four lane arterials U-turn distributions at median openings were analyzed to investigate how U-turns are accommodated at such locations. A u-turn regression model was developed to investigate impacts of median modifications on signalized intersection safety. The model results indicated that median modifications across the high volume driveways may cause safety problems at downstream signalized intersection.

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Concrete, the major construction material used in the civil industry worldwide, displays remarkable performance and economic benefits. Yet, it also presents a huge environmental impact producing about 7% of the global carbon dioxide (CO2). Given the rise of global warming concerns, studies have been focusing on alternatives to reduce the amount of Portland cement (PC), which is the least sustainable ingredient of the mixture, for example by adopting particle packing model (PPM) techniques. Although a promising alternative, there is currently a lack of studies regarding the efficiently use of PPMs to reduce PC without compromising the fresh and hardened properties of the material. This work appraises the influence of PPMs and advanced mix-design techniques on the fresh (rheological behaviour) and hardened (compressive strength, modulus of elasticity, porosity, and permeability) state behaviours of systems with reduced amount of PC, the so-called low cement content (LCC) concrete. Results show that is possible to produce eco-efficient concrete maintaining and/or enhancing fresh and hardened properties of the material. Nevertheless, further durability and long-term behaviour must be performed on LCC systems.

The construction industry is closely tied to economic development economies, and increasing demand also presents a significant contribution to environmental degradation. The construction industry’s impact to climate change is led by the 8% contribution from the production of concrete mixtures, more specifically, the production of cement. The combination of using advanced mixdesign techniques (e.g., particle packing models -PPM) and more sustainable ingredients poses as a promising alternative to overcome concrete environmental impact. However, there is a lack of studies regarding the fresh state difficulties arising from the aforementioned combination. Therefore, this work appraises the use of mobility parameters to overcome the fresh state issue raised when mix-designing mortar mixtures through PPM and with high volume of limestone filler. Twelve mixtures were developed with distinct cement content ranging from 150 kg/m3 to 320 kg/m3. To produce sustainable mortar, besides using PPM, cement content was replaced by limestone filler. Time dependent fresh state analysis was performed using mortar slump flow and a rheological profile. In the hardened states, the compressive strength, porosity, surface electrical resistivity tests were performed. The main findings of the project observed a strong correlation between mobility parameters and five distinct rheological parameters: flow behaviour parameter, high shear rate viscosity and shear stress, low shear rate viscosity and shear stress. Additionally, in the hardened state, a dilution parameter IPScement was used to appraise the dilution and filler effect of the mortar mixtures. The works highlighted a promising method to produce eco-efficient mortars.

Concrete, the second most used material in the world, presents great performance and economic benefits. Yet, it is often characterized by a brittle behaviour, low tensile strength, and toughness. Fibers are usually added to concrete to counteract its brittle behaviour, increasing ductility and toughness, controlling crack propagation and delaying concrete failure. However, their addition significantly worsens the fresh state performance of the material. To improve fresh state of the so-called Fiber Reinforced Concrete (FRC), conventional mix-design methods recommend the use of high paste content, which results in a significant increase of Portland cement (PC) content and raises the carbon footprint of the material. The latter is responsible for 8% of the global annual carbon dioxide (CO2) anthropogenic emissions. Given the current worldwide concerns on global warming, the construction industry is in a need to lessen the demand, and thus production of PC. Recent studies have been focusing on the use of advanced mix-design techniques (i.e. particle packing models- PPMs) along with Inert Fillers (IF) as an alternative to reduce PC content in concrete. However, the latter was not applied to conventional FRC. In this work, advanced mix design techniques (i.e. PPMs) are used to overcome the aforementioned issues and mix-proportion eco-efficient FRC with low cement content (< 300 kg/m3). Fresh (i.e. VeBe time, slump, rheological behaviour) and hardened (i.e. compressive strength, and flexural behaviour) state tests were performed on the proposed mixtures and compared with control high PC content (375 kg/m3) FRC mixes. Results show that PPM designed mixes presented higher minimum torque (yield stress) but quite comparable apparent viscositiy when compared to conventionally designed mixtures. Moreover, the flowability (i.e. VeBe time, and slump) tends to decrease as fiber content, length, and/or as the amount of fillers increase in the mixtures. In addition, PPM mixes exhibited a shear thinning behaviour following the Herschel-Bulkley model, which enables the design of FRC PPM mix-proportioned mixtures for applications requiring high torque regimes such as vibrated and/or pumped concrete. Finally, results show that the use of PPMs to mix proportion eco-efficient low cement FRC mixtures produced improved hardened (i.e. compressive strength, and flexural performance) state behaviour with lower environmental impact than conventional ACI designed FRC mixtures.

Wildland fire behavior research in the last 100 years has largely focused on understanding the physical phenomena behind fire spread and on developing models that can predict fire behavior. Research advances in the areas of live-fuel combustion and combustion modeling have highlighted several weaknesses in the current approach to fire research. Some of those areas include poor characterization of solid fuels in combustion modeling, a lack of understanding of the dominant heat transfer mechanisms in fire spread, a lack of understanding regarding the theory of live-fuel combustion, and a lack of understanding regarding the behavior of flames near slopes. In this work, the physical properties, chemical properties and burning behavior of the foliage from ten live shrub and conifer fuels were measured throughout a one-year period. Burn experiments were performed using different heating modes, namely convection-only, radiation-only and combined convection and radiation. Models to predict the physical properties and burning behavior were developed and reported. The flame behavior and associated heat flux from fires near slopes were also measured. Several important conclusions are evident from analysis of the data, namely (1) seasonal variability of the measured physical properties was found to be adequately explained without the use of a seasonal parameter. (2) ignition and burning behavior cannot be described using single-parameter correlations similar to those used for dead fuels, (3) moisture content, sample mass, apparent density (broad-leaf species), surface area (broad-leaf), sample width (needle species) and stem diameter (needle) were identified as the most important predictors of fire behavior in live fuels, (4) volatiles content, ether extractives, and ash content were not significant predictors of fire behavior under the conditions studied, (5) broadleaf species experienced a significant increase in burning rate when convection and radiation were used together compared to convection alone while needle species showed no significant difference between convection-only and convection combined with radiation, (6) there is no practical difference between heating modes from the perspective of the solid—it is only the amount of energy absorbed and the resulting solid temperature that matter, and (7) a radiant flux of 50 kW m-2 alone was not sufficient to ignite the fuel sample under experimental conditions used in this research, (8) the average flame tilt angle at which the behavior of a flame near a slope deviated from the behavior of a flame on flat ground was between 20° and 40°, depending on the criteria used, and (9) the traditional view of safe separation distance for a safety zone as the distance from the flame base is inadequate for fires near slopes.