New Orleans, Louisiana
June 26, 2016
June 26, 2016
August 28, 2016
Students often lack the ability to apply what they learn in class to real systems. Chemical engineering students typically do not have an engineering lab experience before senior year. Prior work in our group led to commercialization of modular, instrumented heat exchangers and fluid flow experiments to ease the implementation of hands-on activities in a classroom environment. A new system is now being developed with a goal of making experimental modules that are affordable for individual student purchase or alternatively for programs with small lab budgets that wish to purchase units for a large number of students.
This paper describes the development of a very low cost miniaturized industrial shell and tube heat exchanger. Modeling of alternative designs was performed with COMSOL software, and final detailed system design used SolidWorks, the same CAD software that many undergraduate engineering students learn to use in freshman and sophomore level courses. We believe this can encourage students to participate in the design process and propose their own modification of the hardware. We took advantage of the tight integration between the SolidWorks CAD software and 3D printers to manufacture molds for vacuum forming the heat exchanger shells. This gives us the ability to perform rapid prototyping. Transparent PETG plastic sheets are used in vacuum forming the shell of the heat exchanger to allow students to see the tube and baffle arrangement inside the exchanger and to watch how fluid flows through the shell.
The heat duty of the small-scale heat exchanger was predicted from textbook industrial correlations and compared to the heat duty resulting from a 3D COMSOL model and experimental values. The measured heat duty for this small heat exchanger with gravity flow of hot and cold faucet water is about 500 W and the temperature change of each stream is about 4°C. The tube-side Reynolds number dependence of overall heat transfer coefficient from the COMSOL model agreed qualitatively with industrial correlations, however the COMSOL model was in better quantitative agreement with experiment. A key advantage of the lightweight construction is that the system reaches steady state within 5 sec after initiating the flow. The use of gravity flow from plastic beakers avoids the cost of pumps and batteries. During implementation in the classroom students measure inlet and outlet temperatures with a single handheld thermocouple probe and flow rates are measured with graduated plastic beakers and stopwatch.
We implemented this module in a material and energy balance course with 10 groups of three students each. The implementation design included the same four-question quiz given before and after working with the apparatus. A t-test paired sample statistical analysis was used to analyze the results. With all four questions the post-test mean was higher than the pre-test mean with p-values on two questions less than 0.05. This suggests that the module is helping students improve their understanding. Plans are to implement the module in one sophomore-level and one junior-level chemical engineering course this year with a straight lecture control group to look for relative learning gains on key concepts. These results will be presented at the ASEE meeting.
I would like my paper to be in a regular session.
Beheshti Pour, N., & Thiessen, D. B., & Van Wie, B. J. (2016, June), Implementation of an Ultra-low Cost Heat Exchanger Learning Module to Address Energy Balance Concepts Paper presented at 2016 ASEE Annual Conference & Exposition, New Orleans, Louisiana. 10.18260/p.25581
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