Carnegie Mellon University

Invention Based Learning in Transport Laboratory: What the world needs is a better nozzle for hot sauce.

See the WTAE clip Here. (Caution: file is over 10Mb)

Matt Cline and Paul Sides invented a new project for Transport Laboratory in the spring semester of 2008.  Three notions underlay the initiative. 1. Where do inventors learn to invent? They are not trained to invent, per se.  Someone once asked Sonny Barger, the leader of the Hell’s Angels, how his organization recruited new members.  He replied that the Hell’s Angels do not recruit new members, they recognize them.  This urban legend reflects the approach capitalism takes to inventors who have the innate drive to invent or grow into it over time; the successful ones get "recognized." Perhaps a course should exist in which students learn about the process of invention, i.e. what they need to know, eureka and beyond. The hypothesis was that students would be able to generate ideas for products or processes; they would be able to generate a working prototype or demonstration in six weeks; and they would learn more because they owned the project in a way qualitatively different from other assignments.

The assignment We announced the concept to the class during a lecture hour the week before spring break. No groans greeted the news and several students visibly awakened.  One student wanted to know who owns the Intellectual Property, which was the first spark indicating that ownership both in the narrowest and broadest senses, had nucleated. The assignment had four main elements:

1. Each team must invent a product or process based on a principle of momentum, heat, or mass transfer.

2. Each team must demonstrate a working prototype within the six weeks remaining in the semester.

3. Each team must make a poster that describes the idea, the technical underpinnings, prior art, and an assessment of how well it works  (A poster session on the last day of class was envisioned.)

4. Each team had a budget of $1,000.00 to spend on its invention.

The immediate assignment over spring break was that each team must generate three ideas for an invention.

Getting started The experience of the first week surpassed all expectations. Each group came in with at least three ideas, some more than three.  The atmosphere of the discussions was a mixture of seriousness and fun.  The students were touchingly nervous about floating their ideas.  One group described their approach to idea generation as holding a meeting where they “stepped through their day” of activities and asking how each task could be improved.


• Better hair driers:  One team used a combination of vents and bristles made of metal to deliver warm air to the hair more efficiently. Another team proposed to use a combination of mild heat and desiccant to improve hair drying.

• Solar parking lot: Tubes carrying heat transfer fluid and embedded in asphalt can heat water for household use.

• A better hookah:  This team proposed an electrically heated system to improve taste.

• A better distributor of aromatic oil:  Aromatic oils are distributed by immersing the ends of rattan reeds in the oil.

• Energy recovery:  Heat recovery from internal combustion engines and from refrigeration units

• Two groups proposed ways of keeping coffee warm, such as crystallizing of sodium acetate.

• Miscellaneous ideas: A portable Jacuzzi, a heated life vest, a better hot sauce nozzle

The students were more engaged in lab and even more present. On the first day some groups were busily de-constructing commercial products to learn how they worked.  The instructors and TA invoked engineering principles to clarify the logic behind the products. For example, one student asked how his team could evaluate the heat available from various reactions they were considering as potential heat sources.  They were preparing to head for the lab bench to do some experiments when the Prof. Sides pointed out that a quick trip to a handbook might be beneficial.  Of course the student had been exposed to thermochemistry in the thermodynamics courses, but this knowledge was consigned to a “do not open unless being tested in thermo” compartment. The look of combined embarrassment and aha! was the mark of learning.  One student stopped typing on his computer briefly to say “This is fun!” with a look comprising equal parts pleasure and astonishment that he could be enjoying himself in a required engineering class. Many teams worked beyond he class period, good sign.  Another group posted an email to their classmates citing an especially good website for finding heat exchangers.  Another good sign.

As an example, consider the solar parking lot team.  The concept is clear … tubes buried in asphalt and carrying a heat transfer fluid from the parking lot to a central heated water reservoir.   The questions arising from the implementation of this project, however, are many.  Should the students build a "scale model" of a whole parking lot with tiny tubes and a thin layer of asphalt-simulation material or should they build a representative section with a 12 cm layer of asphalt and real-scale tubes?  Should their strategy be to think about the design first and build later or go ahead and start building in parallel with model development?  How does the time available affect their strategic decisionmaking? What are the heat transfer mechanisms in play and how are they connected?  What are the constraints on the problem?  To what extent are advanced engineering tools such as finite element analysis appropriate to use?

The discussion with the scented oil team centered on modeling of the system.  What is the rate limiting step?  The students had found a description of a formula called the Washburn equation for evaluating the rise of liquid in a capillary.  The instructor asked them to derive it. The team worked up the solution to the capillary rise problem and was trying to develop an experiment that would give clues about the mechanism of mass transport in a rattan reed.  One main question was, how does the oil get out?  Does it flow by capillary action to the top and then evaporate, does it flow partially to the top of the reed and then evaporate thru the open end?  Does it infuse the reed and evaporate from the sides?  A couple of experiments were proposed.  First they coated the end with glue and observed the rate of evaporation.  Not much happened.  Then they coated the outer surface of the reed and observed.  The rate decreased substantially.  The group then tried to visualize the progress of the oil up the reed, but couldn't see it until they added food coloring.  The food coloring became visible even from the outside.  The implication seemed to be that the oil was rising part way up the read, diffusing outwardly from the walls.  In this sense, the reed is an extended surface for mass transfer, technically analogous to the classic problem heat transfer from an extended surface such as a pin fin.

The hot sauce team had done some testing of existing hot sauce dispensers.  The purchased various bottles of hot sauce and did splat testing of the hot sauce shaken from the bottle.  They found that the design of the nozzle/cap made a difference in whether the hot sauce splat generated droplets that scattered from the impact zone or whether the sauce formed a circular non-splattering coating on the surface.  They had generated a concept for a nozzle that involved multiple apertures arranged in a circular pattern and used a rapid prototyping machine to make it.  The interesting point is that, despite their direct experience with techniques for measuring viscosity, they had not connected even that laboratory experience with the problems underlying their invention.  Of course, when the instructor mentioned that it might be a good idea to support their development process with measurement of the viscosity of various hot sauces, they had the aha! reaction.

For a few weeks, one could walk into the lab and see a fully instrumented purple hookah.

Final Push and Poster Presentations The teams pulled their work together during the final two weeks. At 8:30 AM on the day of the poster session, the President of Carnegie Mellon, Dr. Jared Cohon, entered the laboratory and began visiting the posters. Prof. Sides cautioned him to step back a bit when the hot sauce nozzle was being demonstrated, which saved his suit. After the President left, faculty and graduate students, university media, and even local television news visited the poster session, which thrilled the students.  A feature on the event was shown on the Pittsburgh affiliate of ABC three times in the ensuing 24 hours news cycle.

In summary, students invented and realized their inventions with far more enthusiasm than for pat assignments. The students improvised and pushed their ideas to some working level, but I was surprised about having to remind students continually that engineering science taught in their courses applied to their inventions and could be used to enhance them. We need to work on closing this gap. The main lesson learned was that we had found a formula for engaging the students and that the project should be repeated in subsequent years.

Paul Sides