Doctor of Philosophy (PhD), Wright State University, 2023, Engineering PhD

Icing, or the formation of ice from water via freezing or water vapor via desublimation, is a phenomenon that commonly occurs within air cycle-based refrigeration systems and requires thermal control that limits system performance. In aircraft applications icing frequently occurs in the heat exchangers and turbine(s) that are part of the air cycle machine, the refrigeration unit of the environmental control system. Traditionally, water vapor is removed from an air cycle machine via condensing in a heat exchanger and subsequent high-pressure water separation. This approach is not capable of removing all of the vapor present at low altitude conditions, corresponding to a high risk of icing. To mitigate icing under these conditions, a membrane dehumidifier is considered to separate the water vapor that remains after condensing and liquid water separation. Three distinct investigations are conducted as part of this work. The first is aimed at modeling approaches for desublimation frosting, or frost growth on sufficiently cold flat surfaces. This results in a novel, analytical, and non-restrictive solution well-suited for representing frost growth and densification in moist air heat exchangers. The second investigation concerns membrane dehumidification and module design. A custom component model is developed and verified under aircraft conditions, then the Pareto frontier of volumetrically efficient membrane modules is characterized via a multi-objective optimization study. The final investigation evaluates three two-wheel air cycle subsystem architectures with differing dehumidification approaches: (1) condenser-based, (2) membrane dehumidifier-based, and (3) combined. Steady-state simulations are run for each of these over a range of flow rates and altitudes. The results demonstrate that incorporating a membrane dehumidifier reduces the turbine inlet saturation temperature, which mitigates icing in the turbine and reduces the required bypass fl (open full item for complete abstract)

Committee: Mitch Wolff Ph.D. (Advisor); James Menart Ph.D. (Committee Member); Abdeel Roman Ph.D. (Committee Member); José Camberos Ph.D., P.E. (Committee Member) Subjects: Mechanical Engineering

Master of Science, University of Toledo, 2019, Civil Engineering

This thesis validates the use of Analatom AN110 corrosion sensors and the dehumidification system in the main cables of The Anthony Wayne Bridge over Maumee River in Toledo, Ohio, to keep the relative humidity at a level in which corrosion cannot occur. The 88 years old bridge has been subjected to several rehabilitation projects to control corrosion, as well as to extend its life cycle. The acoustic emission monitoring system was installed in 2011 to detect potential locations of corrosion, but no such signals were detected. Internal inspections done by Modjeski and Masters, Inc. at two locations on each cable revealed severe corrosion and subsequently urged Ohio Department of Transportation (ODOT) to find promising technology, such as a dehumidification system, to prevent corrosion. Previous research and inspections revealed that, even with improved wrapping and painting, it was impossible to make cables completely watertight, which led researchers to find a system that can protect cables by controlling humidity. Main cable dehumidification involves injecting dry air into the cable environment which then collects moisture, releasing it through exhaust, thereby reducing relative humidity and controlling corrosion.This system is also considered the most cost-effective approach in prolonging the life cycle of the suspension bridges. In this thesis, an extensive review of literature about cable dehumidification and examples of past applications of this system in bridges is presented, along with the application of Linear Polarization Resistance (LPR) technology, laboratory testing of Analatom AN110 corrosion sensors, and dehumidification systems. An environmental chamber with an aluminum duct was created inside the laboratory to simulate the condition of the main cables. AN110 corrosion sensors used LPR technology to measure corrosion rate and relative humidity in real-time, and the data was retrieved with the help of the Data Acquisition System. The first test w (open full item for complete abstract)

Committee: Douglas Nims (Advisor); Mark Pickett (Committee Member); Alex Spivak (Committee Member) Subjects: Civil Engineering

Master of Science, University of Toledo, 2016, Civil Engineering

The Anthony Wayne Bridge is a suspension bridge located in Toledo, Ohio currently undergoing an extensive rehabilitation project. Internal inspection revealed corrosion of the steel wires within the bridge's main cable. The bridge operators have elected to pursue the installation of a dehumidification system. Such a system injects dry air into the cable to lower the relative humidity and stop the corrosion process. The research presented in this thesis investigates the use of the Analtom AN110 corrosion sensor and its applications on the Anthony Wayne Bridge. Dehumidification systems require extensive monitoring systems to ensure their effectiveness and proper operation. The AN110 corrosion sensor uses linear polarization resistance (LPR) technology to measure corrosion rates in real time. Such measurements could potentially provide data valuable in ensuring the effectiveness and progress of the drying-out process. Included is an extensive review of the bridge's rehabilitation process, a literature review of dehumidification and the application of LPR technology, and laboratory testing of the corrosion sensor. Laboratory testing involved the exposure of the sensor to cyclic relative humidity to observe the relationship between corrosion rate and relative humidity. The use of the AN110 corrosion sensor in the monitoring of the future dehumidification system on the Anthony Wayne Bridge is recommended. Among other factors, testing results showed a clear and consistent relationship between the recorded corrosion rate and the relative humidity. The sensor functions as expected and confirms the existing understanding of the effect of relative humidity on the corrosion of steel.

Committee: Douglas Nims (Committee Chair); Mark Pickett (Committee Member); Joseph Lawrence (Committee Member) Subjects: Civil Engineering

Master of Science in Civil Engineering, University of Toledo, 2013, Civil Engineering

The main cable of a suspension bridge is a fracture critical element which is difficult to inspect. The research presented in this thesis investigates this universal problem plaguing owners of suspension bridges across the globe. It is well known that the leading issue associated with deterioration and aging of steel bridges is corrosion. In most cases, visual inspection of structural members has long been an adequate method for monitoring steel structures exposed to environmental conditions which lead to corrosion. In the case of suspension bridges, it is possible to visually inspect the deck and towers with minimal difficulty; however, visual inspection of the main cables is both difficult and expensive. It is not possible to visually inspect the entire volume of the cable in a practical, cost-effective way. For this reason the current solution is to perform an invasive inspection in accordance with the NCHRP-534, which attempts to maximize the probability of estimating the condition of the cable while minimizing effort and expenses. These issues have lead researchers to look for nondestructive methods of determining the condition of the cable. The methods discussed in this thesis include acoustic monitoring, embedded sensors, and magnetic inspection through the magnetic main flux method. In addition, the study sought to identify the best available procedures for protecting the cables of suspension bridges from corrosion. Dehumidification, a method of controlling the cable environment to prevent corrosion, was identified as a promising preservation technology and is compared to traditional protection strategies. This study includes laboratory research on corrosion monitoring through acoustic emission and has evaluated both the available monitoring and preservation strategies for suspension bridge main cables. The research was performed for the Ohio Department of Transportation, and the results will have a direct impact on the Anthony Wayne Bridge in T (open full item for complete abstract)

Committee: Douglas Nims (Advisor); Brian Randolph (Committee Member); Ali Fatemi (Committee Member) Subjects: Civil Engineering

Master of Science, The Ohio State University, 2010, Food Agricultural and Biological Engineering

Leading Dutch researchers reported significant benefits to closed greenhouse systems. Ooteghem (2007) simulation studies of optimal control in a closed greenhouse environment predicted 52% heating fuel saving and 39% increase of tomato crop yield using a heat recovery system whose major components included heat pumps, heat exchangers and aquifers. Opdam et al. (2005) reported 19% primary energy saving, 22% yield increase, 80% chemical reduction, and 50% irrigation water saving for tomato production in a closed greenhouse. Although the Dutch researchers successfully demonstrate year-round operation of closed greenhouses, their success benefited from the mild weather and availability of aquifers, not always the case for other geographical regions. Results of this study using Ohio conditions estimated that 90% and 92% of CO2 loss through cooling and dehumidification ventilations when an elevated CO2 level of 800 ppm must be maintained. This study also found that for Wooster, Ohio to achieve economical year-round closure, due to the larger weather variation and lack of accessibility to aquifers, a better economical return would be expected with semi-closed designs that allow the greenhouse to vent when the heat load is approaching a certain percent of peak levels. For example, a 50% peak load design can meet the cooling and dehumidification needs of a closed greenhouse for 92% and 90% of the year, respectively. Also determined in this study was the amount of heat which can be recovered with thermal storage. Potential recoverable heat of a closed greenhouse at Wooster, Ohio can contribute up to 23%, 25% and 98% of total heating needs of the year, 2006, with 1-day, 2-day and year-round thermal storage capacities, respectively. The models used for the above analyses were evaluated using data collected in a greenhouse located at Wooster, OH. Convection and infiltration heat loss prediction were validated during cloudy and clear sky nights. The results gave prediction disagr (open full item for complete abstract)

Committee: Peter P. Ling PhD (Advisor); Harold M. Keener PhD (Committee Member) Subjects: Agricultural Engineering; Engineering