Graduation Year

2009

Document Type

Thesis

Degree

M.S.M.E.

Degree Granting Department

Mechanical Engineering

Major Professor

Delcie Durham, Ph.D.

Keywords

Biological systems, Environmental impact, Sustainability, Exergy analysis, Green engineering

Abstract

A broad scope analysis of waterjet cutting systems has been developed using thermodynamics, life cycle analysis, and biological system comparison. The typical assessments associated with mechanical design include measures for performance and thermodynamic efficiency. Further analysis has been conducted using exergy, which is not typically incorporated into design practices. Exergy measures the effectiveness of a process with respect to a base state, usually that of the systems surroundings. Comparing Gibbs free energy of biological processes to exergy efficiency has served to illustrate the need for various levels of comparison. Each biological process used in this comparison correlates to a different type of mechanical process and level of complexity. Overall, biological processes display similar properties to mechanical systems in that simpler systems are more energy efficient.

In order to determine accurate efficiency and effectiveness values for a mechanical process, in this case waterjet cutting, a set of thermodynamic models was established to account for energy uses. Various output force and velocity models have been developed and are used here for comparison to assess output efficiencies with "no loss" models used as a lossless base. Experimental testing was then conducted using a simple nozzle and a pressure washer with 2 other diameter nozzles. The most energy efficient system used a turbojet nozzle. It was also the most efficient sustained system with energy inputs. However, it had a much lower exergy efficiency compared to the other systems. This implies that it could be significantly improved by more adequately utilizing the energy provided. An effort to assess the green nature of pressurized water systems was done through use of an Economic Input/Output Life Cycle Analysis (EIO-LCA).

The EIO-LCA is designed to assess processes for greenhouse gas emissions and total power consumption across the life of a system. Calculations showed that increases in power consumption result in much higher greenhouse gas emissions per unit time than increases in water consumption. Financial cost however showed an opposite trend due to the much greater cost of water with regard to consumption rates in each system. The most "green" system used only a nozzle with no power consumption.

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