Master of Science / Department of Mechanical and Nuclear Engineering / Mohammad H. Hosni / A traditional cooling/refrigeration cycle has four main system components which are an evaporator, a compressor, a condenser, and an expansion valve. This type of cycle requires use of refrigerants which have been found to be harmful to the environment, including causing damage to the atmospheric ozone layer. The main objective of the project was to investigate a water-based non-vapor compression cooling system. Water as a working fluid has the advantages of being inexpensive and environmentally safe for use, as compared to commercially available chemical refrigerants. The water-based cooling system investigated employed cavitation phenomena in converging-diverging glass nozzles. Cavitation is an important phenomenon in fluids, and is common occurring in many devices such as pumps, refrigeration expansion valves, and capillary tubes. It occurs when the static pressure of the fluid falls below the vapor pressure, into a metastable liquid state. Cavitation can be in the form of traveling bubble cavitation, vortex cavitation, cloud cavitation, or attached wall cavitation. In this thesis, the focus was first on visualizing cavitation for water flowing through converging- diverging glass nozzles. These nozzles had throat diameters between 2 mm and 4 mm. Two systems were used: (1) a continuous flow system, where water was driven by a centrifugal pump, and (2) a transient blow down system, where water flow was initiated using a suction pump. A high-speed camera was used to record videos and images of the associated cavitation phenomena. A thermal infrared camera was used in an attempt to measure temperature drop in the nozzle while the system was running The second part of this thesis focused on the understanding of the fundamental thermodynamics phenomena and on the development of practical knowledge relevant to the cavitation process. Two equations of state were used in the analysis, the van der walls equation of state, and the Peng Robinson equation of state. Equations of state were used to predict the transition from vapor to liquid. At a given temperature, the equations were solved for a pressure value corresponding to saturated liquid and saturated vapor specific volume values. Then, the equations were used to determine the spinodal liquid and vapor lines, which represent the metastabillity limits for the liquid and vapor. The characteristic equations of state, combined with implementation of the Law of Corresponding States and thermodynamic theory, were used to estimate the temperature reduction available for refrigeration.

Diverging diamond interchanges (DDI) have been proved to outperform other types of diamond interchanges in terms of safety, cost-effectiveness and efficiency, but few research efforts have been done to conduct the analytic calculation of delay, with which optimization of timing plans can be acquired more efficiently. This paper develops the control strategies based on the introduction of overlap and offset analysis, which provide a uniform representation of sequences for DDI signal control. Based on the developed timing plan then the delay calculation equations are put forward and results show the calculation fit simulation very well with R-Square to be 0.9949 for total delay of those two directions. Ecodriving aims to achieve the best fuel efficiency by guiding vehicles travel at planned and optimized speed trajectories. This study opens the door for safety concerns for following normal driving vehicles (FNVs) when following ecodriving vehicles (EVs). To examine the safety issues under different circumstance. Three road elements: initial signal status, ambient vehicles and speed limit along with three EV elements: SpeedTolimit, DistanceToStoplight and acceleration were chosen as potential influential elements, and time to collision (TTC) was selected as the dependent variable. Therefore, six testing scenarios and six baseline were designed and implemented using a drive safety DNS-250 simulator. 29 drivers participated in the driving simulator study. The results show the aforementioned road elements and EV elements have significant influence on TTC of FNV in different testing parts. Therefore, these finding can be used as guidance for future ecodriving algorithm design and implementation. / Master of Science / The research conducted in the thesis are composed of two sub-topics: delay calculation for diverging diamond interchange and safety assessment of ecodriving, on following traffic. Both of them are new coming technologies and are attracting increasing research interests. The first research topic, diverging diamond interchange is a new design of interchange which aims to decrease the conflict points of intersection hence increase the safety and efficiency. The second topic is about ecodriving, which is a vehicles communication-related topic, aims to improve fuel efficiency by taking better use of signal phasing and timing (SPaT) information. Both of them will contribute to the construction of environment-friendly and safe transportation systems. The research on these topic are innovative and should play role in guiding follow-up research in the future.

Master of Science / Department of Mechanical and Nuclear Engineering / B. Terry Beck / Mohammad H. Hosni / Cavitation is the formation of vapor phase from the liquid phase by reduction in its absolute pressure below the saturation pressure. Unlike boiling, where the temperature of the liquid is increased to cause vaporization, the reduction in the pressure alone can cause the liquid to turn into vapor. Cavitation is undesirable in many engineering applications as it is associated with reduction in efficiency and is known to cause damage to pump and propeller components. However, the endothermic nature of cavitation could be utilized to create a region of low temperature that could be utilized to develop a new refrigeration cycle. The work presented in this thesis is part of ongoing research into the potential cooling capacity of cavitation phenomena, where the cavitation in a converging-diverging nozzle is being investigated. Due to the constricting nature of the throat of the converging-diverging nozzle, the liquid velocity at the throat is increased, obeying the continuity law. With an increase in velocity, a reduction in absolute pressure is accompanied at the throat of the nozzle according to the Bernoulli’s principle. The local absolute pressure at the throat can go lower than the saturation vapor pressure, thereby causing the fluid to cavitate. The effect of water temperature on the flowrates, the onset of cavitation within the nozzle, and the resulting length of the cavitation region within the nozzle are the subject of this thesis. Experimental results and analysis are presented which also show that near the onset of cavitation, the flowrate can go beyond the choked flowrate, causing the local pressure in the throat to go well below zero for an extended amount of time in the metastable state, before nucleating (cavitating) into a stable state. Flow visualization using a high speed digital camera under different operating conditions was aimed at investigating the region of cavitation onset, which appears to be associated with boundary layer separation just downstream of the nozzle throat. In order to delay the boundary layer separation point in the downstream section of the nozzle, the diffuser region of the nozzle was modified to enable two flow paths, where one path would suck the flow near the inner walls of the nozzle and the other would allow the bulk of the flow to pass through. This was achieved with the use of inserts. Various inserts were tested in an attempt to capture the effect of inserts on the cavitation phenomena. Their effect on the flowrates, length of two phase region, and cavitation onset are presented in this thesis.

The master´s thesis deals with the flow induced by rotation of cavitating fluid in converging-diverging nozzle, which simulates the vortex rope in impeller of water turbines. Measurement is performed on an experimental circuit in laboratory. Results from experimental measurements are compared with CFD simulation of single and two-phase flow. The main focus is to compare the difference of hydraulic losses and shapes of cavitating structures identified in the experiment and in the simulation.

As the population grows and the travel demands increase, alternative interchange designs are becoming increasingly popular. The diverging diamond interchange is one alternative design that has been implemented in the United States. This design can accommodate higher flow and unbalanced flow as well as improve safety at the interchange. As the diverging diamond interchange is increasingly considered as a possible solution to problematic interchange locations, it is imperative to investigate the safety effects of this interchange configuration. This report describes the selection of a comparison group of urban diamond interchanges, crash data collection, calibration of functions used to estimate the predicted crash rate in the before and after periods and the Empirical Bayes before and after analysis technique used to determine the safety effectiveness of the diverging diamond interchanges in Utah. A discussion of pedestrian and cyclist safety is also included. The analysis results demonstrated statistically significant decreases in crashes at most of the locations studied. This analysis can be used by UDOT and other transportation agencies as they consider the implementation of the diverging diamond interchanges in the future.

Statistical graphics are often augmented by the use of color coding information contained in some variable. When this involves the shading of areas (and not only points or lines) - e.g., as in bar plots, pie charts, mosaic displays or heatmaps - it is important that the colors are perceptually based and do not introduce optical illusions or systematic bias. Here, we discuss how the perceptually-based Hue-Chroma-Luminance (HCL) color space can be used for deriving suitable color palettes for coding categorical data (qualitative palettes) and numerical variables (sequential and diverging palettes). / Series: Research Report Series / Department of Statistics and Mathematics

Statistical graphics are often augmented by the use of color coding information contained in some variable. When this involves the shading of areas (and not only points or lines) - e.g., as in bar plots, pie charts, mosaic displays or heatmaps - it is important that the colors are perceptually based and do not introduce optical illusions or systematic bias. Here, we discuss how the perceptually-based Hue-Chroma-Luminance (HCL) color space can be used for deriving suitable color palettes for coding categorical data (qualitative palettes) and numerical variables (sequential and diverging palettes). / Series: Research Report Series / Department of Statistics and Mathematics

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