Modeling And Experimental Observation Of A Rapid Compression In A Piston Cylinder Assembly For Use With Model Eliciting Activities

In this work, the classic thermodynamic problem of a rapid compression of a closed system contained in a piston-cylinder assembly is studied. This experiment allows students to gain a deeper understanding of reversible processes, polytropic processes, and the appropriateness of the ideal gas law assumption. Rather than being told how to model the process, the experiment gives students the opportunity for open-ended investigation of a system commonly encountered in thermodynamics courses. Students can use the experimental results to assess the accuracy of their assumptions. In order to keep costs low and promote dissemination of the experiment, the experimental apparatus is a modified version of an inexpensive scientific toy which goes by the following names: Fire Tube, Flash Tube, or Fire Syringe. The device is basically a handheld glass or acrylic tube with a metal plunger which can compress air within the tube. If you put a small piece of paper inside the tube, the system conditions after compression are such that the paper may ignite and burn. For this investigation, a Fire Tube has been instrumented to acquire pressure and volume data during the compression. The data acquired from this investigation will be utilized in the development of Model-Eliciting Activities (MEAs). MEAs use open-ended case studies to simulate authentic, real-world problems that small teams of students address. MEAs do not resemble the problem-solving activities involved in most course textbooks, differing in length of time, access to information resources, number of individuals involved in problem-solving, and type of documentation that is required. However, the most important difference is the emphasis on building, expressing, testing, and revising conceptual models. Universities which adopt MEAs into their curriculum could use the data presented here, and avoid the cost and effort associated with instrumenting their own Fire Tubes.