Blowing off steam tables

Abstract

In thermodynamics courses, there is appreciable time and effort devoted to teaching steam tables. Despite this, students still find the ability to use steam tables for retrieving thermodynamic properties a challenging skill to master. The challenges arise from the need to interpolate, the need to identify the correct region, and the requisite familiarity with property trends. The use of steam tables to retrieve thermodynamic properties is often presented to students as a keystone skill for subsequent study of steam power plants. However, if graduates do not require this skill in practice, perhaps we are simply teaching an obsolete system that serves the course objectives but not beyond. Several compelling alternatives exist. Among them, computerized thermodynamic property databases for common substances are readily available and can rapidly supply state properties. However, we want to avoid tools that simply supply property values without reinforcing thermodynamic fundamentals. For instance, steam tables can supply accurate property values, but they fail to emphasize the interdependence of these properties. Instead, the use of property diagrams to solve thermodynamic problems can greatly improve students' understanding of thermodynamics by visualizing property relationships. As a highly visual and intuitive tool, property diagrams eliminate the time devoted to mastering steam tables. After teaching steam tables for multiple years within a year-long thermal-fluid sciences course and recognizing the poor pedagogic utility, the steam tables were entirely replaced by the temperature-entropy ( T-s ) diagram as the primary source for water thermodynamic properties. This paper discusses the implementation, challenges, and the outcomes of this introduction. Apart from developing instructions aligned solely to property diagrams, a number of visual tools were identified, adopted, and developed to facilitate the transition. The overall outcomes were notably positive from a student learning perspective. Students quickly became comfortable using the T-s diagram to solve the same textbook problems they would have solved using steam tables. The loss of accuracy was more than made up by their ability to quickly identify a state and retrieve its properties. Furthermore, students improved their ability to predict property trends when compared to students who relied primarily on steam tables. The results highlight the need for change in thermodynamics pedagogy by abandoning steam tables and emphasizing the fundamentals necessary to study steam power plants.