ChBE 162 is a required foundational class for undergraduate chemical engineering students. Roughly 60 sophomores take this class every year. Based on student self-evaluations of the course and performances on exams, students lack confidence in applying the concept of efficiency to thermodynamic systems. While they are able to calculate efficiency for a simple process when given the relevant thermodynamic equations, their conceptual understanding for developing such equations is lacking. This gap is apparent when students perform such analyses on analogous processes and wrongly attempt to force-fit prior equations that no longer apply.
The root of the problem is that the concept of efficiency when combined with the use of thermodynamic variables is un-relatable for many students. In order to address this disconnect, we are developing instructional analogies to illustrate the concept of efficiency using more familiar systems, such as those that involve monetary transactions as they should be more tangible. As an example, when a monetary transaction is made at a financial institution, a transaction fee may be charged of say 3%; the efficiency for this step will be 97%. When part of a larger collection of transfers, this cost affects an overall efficiency. The transaction fees in essence symbolize losses in efficiency, analogous to energy losses that may occur during specific unit operations within an overall chemical process.
The use of such analogies activate student learning prior to class. I have developed a series of web-delivered videos, roughly 10 minute each, to explore the concept of efficiency. Students are required to watch these videos for answering problem set questions. The first sets of videos introduce the concept of efficiency and its importance in energy generation systems. These videos develop the analogies for conceptually relating contributors to thermodynamic efficiency to cost-bearing financial transactions. The next set of videos focus on process units within chemical engineering systems that affect efficiency such as pumps and turbines. Here, thermodynamic limits that define efficiency are considered. The final videos relate the overall determination of efficiency to the interconnected function of multiple components together in a chemical process. An example is that of a refrigeration system that consists of a condenser, evaporator, throttle valve and a compressor. Each of these videos is embedded with 3-5 questions to provide interactive feedback.
The improvement in student learning was assessed by two main ways. Firstly, exam questions from several years ago were re-administered in Spring 2015. The performance on the exam questions is compared between 2015 and prior years. Secondly, student attitude surveys were administered to gauge student perceptions towards the videos.
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