(186h) Redefining the Scale of Fluid Flow Experiments

The sudden migration to online instruction was one of the repercussions of the global COVID-19 pandemic which brought unprecedent challenges for engineering education, especially for laboratory-based courses with hands-on learning outcomes. Unit Operations laboratories are one of these courses in Chemical Engineering undergraduate programs which often involves experimentation with pilot-scale flow systems comprised of pumps, valves, flow meters, and pipe networks, to study the principles of fluid flow in pipes. The approach behind fluid flow experiments relies on the direct operation of flow components by students, typically to characterize friction losses in pipes, fittings, and pumps. The lack of hands-on experience that would result from moving Unit Operations laboratories entirely online, without experimentation, was a big concern as it would have compromised some of the student learning outcomes thus jeopardizing the quality of instruction, and even program accreditation.

Motivated by the need to alleviate these challenges, small-scale experimental kits were conceptualized, designed, and utilized in online instruction of Unit Operations 1, the first of the three laboratory-based classes taken by undergraduate Chemical Engineering students at University of Florida during their junior and senior years. Experimental kits were designed to satisfy criteria such as modularity, cost-effectiveness, and safety, and to be easily shipped to each student in the class. Among these kits, the mini fluid flow (MFF) system was designed to have a 3D-printed fluidic device comprised of pipes of different diameters, contractions/expansions, bends, and built-in pressure taps. The fluidic device was connected to a submersible pump, receiving water from a plastic reservoir by means of plastic tubing containing flow reducers, and a small pinch valve to adjust the flow rate. Eleven “tube taps” enabled pressure drop measurements across pipes and fittings using a miniaturized differential pressure sensor that was subsequently connected to an Arduino microprocessor for real-time data monitoring and acquisition. Rigorous characterization tests were conducted not only to match operating ranges of both pump and pressure sensor but also to satisfy the desired scale of the system, among other design criteria. The MFF was designed to have a main inlet (receiving water from the pump) and two outlets discharging water back to the reservoir thus completing a closed loop. A plastic, graduated cylinder was used to measure flow rate using the so-called stopwatch and bucket method. The signal transferred from the differential pressure sensor to the Arduino microprocessor is read and saved in a personal computer via acquisition software. The overall goal of mini fluid flow experiments was the systematic investigation of friction losses using pressure drop measurements across multiple flow pathways. Experiments were designed such that students were able to conduct experiments individually at home, controlling experimental factors such as flow rate and flow configurations, and having the total pressure drop across the device as response variable.

The incorporation of mini fluid flow experiments in Unit Operations 1 when taught 100% online, demonstrated the ability to maintain high-quality, online instruction of fluid mechanics topics using small-scale, versatile experiments with opportunities for multiple experimental configurations and statistical analysis. Even though remotely assisted by instructors and lab assistants, students conducting experiments at home were able to fully assemble/disassemble the various MFF components which fostered troubleshooting abilities. A subsequent semester with “HyFlex” instruction (online + in-person) along with improvements in the design of the MFF system led to increased, positive acceptance by students, enhanced team dynamics, and overall improved understanding of topics learnt in lecture classes taken in previous semesters. A special highlight of experiments conducted in HyFlex classes was the flexibility to propose alternative experimental designs which fostered creativity and imagination among students.

Additional studies are currently underway to evaluate the potential of scaling-up and/or scaling-down fluid flow experiments by combining the MFF system with a pilot-scale pipe network, aiming to explore the ability of fluid flow systems to predict flow patterns in experiments regardless of the scale. In addition, further improvements to the MFF system will enable the characterization of fluid dynamics under fully turbulent flow thus strengthening the objectives of fluid flow experiments to be used as a single, small-scale systems or as hybrid (small- and pilot-scale) modules without the restrictions imposed by flow regime. Furthermore, the incorporation of the MFF system is suggested to enforce theoretical concepts of lecture-based courses and as an opportunity to showcase Engineering programs via K-12 experimental demonstrations, science fairs, and outreach initiatives.