No abstract

A key issue in student design projects in thermodynamics is the necessity to modify property values during iteration and/or redesign. This is particularly true when dealing with two working fluids (e.g., air, water) in a combined cycle. The necessity to manually ascertain these values at all points of the cycle can inhibit the pedagogic purpose of the project: to allow students to view how overall system parameters (efficiency, specific fuel consumption, horsepower, etc.) may vary in response to changes in one or several input parameters (turbine pressure ratio, ambient air temperature, barometric pressure, cooling water temperature, boiler pressure, etc.). A separate paper to be presented at this conference describes the details of an Excel™ spreadsheet add-in that relieves the student of the laborious updating of these property values as cycle modifications are made. This paper presents the application of this Excel™ add-in to analyze a baseline combined cycle plant (including cogeneration), and how various sensitivity analyses and optimization problems may be used to enhance students' understanding of the basic design. Additional plants that could be analyzed are suggested.

No abstract

An interactive method for using spreadsheets to calculate and graphically display the properties of various thermodynamic working fluids is presented; the detailed calculation of individual property values is accomplished via Thermal Fluids Toolbox, a freeware program provided by Spreadsheet World, Inc. Interface with the cells containing calls to Thermal Fluids Toolbox is provided with Visual Basic for Applications sliding toolbars which allow a smooth variation of property values. Properly used by students, these worksheets have the potential to reinforce and enhance understanding of the fundamental interrelationships among various properties; students are free to change various parameters such as pressure, temperature, and quality, and immediately view the effect of these changes on the associated Mollier and T-s diagrams. Students may quickly visualize the effect of these changes, rather than being mired in the minutiae of table lookups, interpolation, transcription, and manual plotting. An additional benefit of the rapid and very accurate plotting of thermodynamic properties is a better understanding of approximations frequently employed in the compressed liquid region, wherein the effect of pressure may be neglected (i.e., properties may be evaluated principally as functions of temperature); the relationship between saturation pressure and saturation temperature is also immediately discernable, as well as property variations in the compressed liquid and superheated vapor regions. In addition to the dynamic visualization of the Mollier and T-s diagrams, students may be tasked to use the worksheet to construct their own Mollier and T-s diagrams for prescribed property values using a "copy and paste" technique. A detailed description of the spreadsheet construction for Mollier and T-s diagrams for water is provided, along with suggested tutorial questions for students and recommendations for additional applications. Feedback comments are provided from seniors who used the Mollier and T-s diagrams, and from juniors who used a similar application which provided a tutorial on p-v and Tv diagrams. Several screen shots of the worksheets are provided. The spreadsheet files are available from the author via email.

The Department of Engineering Mechanics at the United States Air Force Academy debuted Engineering Tools Seminar (ETS) in the spring of 2008. ETS is a hands-on course that exposes 3rd-year undergraduate students to manufacturing processes, but ETS is unique in its treatment of other essential "tools" such as computer software, technical communication and engineering ethics. ETS was created to bolster sagging enrollment, deliberately address neglected content, and fulfill student requests for an introductory manufacturing course. Students enrolled in the department's three curricula suggested that an equipment training course prior to their senior year would streamline the training process, eliminating ad-hoc training that occurs in other courses, their capstone courses, or on their own time. Such a deliberate process would produce well-trained, productive students that could hit the ground running in their capstone courses.The manufacturing processes presented include wood working, machining, welding and composite lay-up. In addition, software tools are introduced and compared including Microsoft Excel®, MatLAB®, MathCAD®, and Inventor®. Key aspects of technical communication including reading, writing and presenting are introduced and practiced. Finally, a two-lesson seminar on engineering ethics completes the content. A small desk set is constructed by the students as a capstone project, and draws on many of the skills learned throughout the course. To evaluate the course, students were surveyed frequently and faculty feedback was collected. The results presented show that the welding, machining and Excel® content was very successful, while general organization and some content could be improved in future offerings.