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Thesis Defense: Travis Pruitt

Parameter Estimation and Dynamic State Observer Design for Vapor Compression Systems

Between cooling our house, our workplace, and keeping our food cold both in home and commercially (among other uses), the vapor compression cycle (VCC) is a common method for removing heat from various environments and it accounts for a significant amount of the energy used throughout the world. Therefore, with an ever-growing demand for more efficient processes and reduced energy consumption, improving the ability to accurately model, predict the performance of, and control VCC systems is beneficial to society as a whole. While there is much information available regarding the performance for some of the components found in VCC systems, much of the challenge associated with modeling VCC lies within the complex behavior of the heat exchangers found in the system. Over the years, lumped parameter models have been developed for the VCC. However, many of these rely on simplified geometry (mainly a bare tube assumption), and neglect to capture the effect of the fins found throughout those heat exchangers. This thesis builds upon approaches used in the past by identifying effective heat transfer coefficients that capture this effect. Using this approach, a 2-ton residential air-conditioning unit was modeled and was able to predict the heat removed by the VCC system within ±4% error when compared to published performance data from the manufacturer. Furthermore, these coefficients, along with the complete dynamic model, form the basis of a nonlinear state observer which can be used to further the ability to accurately predict and monitor system performance.

About the presenter

Travis is a mechanical engineer at the American Food Equipment Company in Caldwell and master’s candidate at Boise State’s College of Engineering. At work, his primary role is designing various machinery for the food industry. When not at work, Travis is an avid outdoor enthusiast and enjoys spending as much time as possible with his wife Kelly and dog Sage in the mountain ranges found throughout Idaho and northern Nevada.

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