(147d) The Accumulation TERM: PERSPECTIVES IN Teaching and Learning Unsteady-STATE Material and ENERGY Balances

Abstract This study seeks to understand and explain the underlying issues that cause students to have difficulty solving transient or unsteady-state problems. In a survey given to sophomore level undergraduate students within the Artie McFerrin Department of Chemical Engineering at Texas A&M University, eighty percent of the students indicated that they find unsteady-state problems more difficult to formulate. The most prevalent reasons given to explain why unsteady-state problems were more difficult were that the students have less experience with unsteady-state, they have difficulty setting up the differential balance, the problems are more difficult to visualize conceptually, and the application of differential equations makes them more complicated. Professors who were interviewed also indicated that their students have difficulties in solving unsteady-state systems. They were asked to discuss their thoughts on why students are often unable to solve unsteady-state problems and what could be done to minimize this issue. From these interviews, a list of recurring ideas was compiled. Sophomore chemical engineering students were given two unsteady-state material balance problems to solve in one occasion and one unsteady-state energy balance problem in a second occasion. They were asked to do so in a group but were not allowed to use textbooks. Half of the groups were provided with a step by step problem-solving strategy for unsteady-state problems. In addition, three of the groups were recorded as they attempted to solve these problems. For comparison, three senior chemical engineers were given the same set of problems and asked to solve them without the use of a textbook. The solutions were then reviewed and graded. Errors were grouped into several categories. In this paper, the authors will describe their preliminary findings and future plans to expand their studies to understand the student discomfort with transient systems. A web module that was developed for conservation of mass will also be presented. The authors hope that their findings will help them to develop effective tools and methodologies that can be integrated throughout the curriculum for teaching unsteady-state systems.

Key Words: Unsteady-state, transient, problem solving, material balances, energy balances