So I’m at DESIGN West in San Jose walking the aisles, looking to replenish my collection of free pens (sure to someday become a valued family heirloom) and soaking up the attendee and exhibitor buzz. As I go up and down the rows, I am surrounded by coding tools, debuggers, ICs, prototype PCB and product vendors, sensors, displays, and more—pretty much what you’d expect at a major industry event catering to those engineers who actually have to get a project done (in sharp contrast to the glitz, glam, and promises of CES, the Consumer Electronics Show in, of course, Las Vegas).
Amidst all the sophisticated products I see—and they truly are magial and miraculous, if you stop to think about it for a while—there are a few vendors offering heat pipes. You can’t get more un-electronic that those. [If you don’t know what a heat pipe is, you should; take a moment to educate yourself here.]
A heat pipe’s role in life is simple: to convey heat from point A—that’s usually your circuit or component—to point B—a heat sink, cold plate, or some sort of radiator. What’s amazing is that the heat pipe does this silently, reliably, effortlessly, without fans, motors, an external power source, or moving parts (we’re not considering the moving fluid inside as a moving part.)
So why do I like heat pipes? There are a few reasons: first, they solve your thermal problem without introducing new problems. They do one thing and they do it well—efficiently, quietly, passively, and quickly. They don’t try to dictate your system design or topology, have revision issues, or give you compatibility headaches.
They are like the quiet kid in the back of the class who somehow understands the assignment, hands it in on time, neatly done, and doesn’t complain that the assignment was given out only the day before it was due, or over a holiday weekend. Or maybe they are like the project team member at the design review meeting who says “no problem, I’ll take care of that” and comes back the next day with a simple, elegant solution to the design problem, all nicely wrapped and ready to go.
I’ll tell you another reason I like them: they are a great “demo” for younger students. In an age when kids are jaded and immune to the amazing technology around them, the simplicity of the heat pipe strips that all away and is its virtue as a visual aid. A very effective hands-on demonstration is this: you take a cup of very hot or even boiling water (if you afraid of regulatory or safety concerns, go the other way and use ice water, but it’s not at all as dramatic). You put one end of a plain metal rod about the size of a pencil into the liquid, and have the student hold the exposed end. Eventually, the end gets hot (or cold, depending on the liquid). No big deal, that’s just common sense and experience.
Then you take a heat pipe of the same length and diameter of your plain rod, and repeat the experiment. With a second or so, the end being held gets hot (or cold). And how did this rod, which looks the same as the first one, do that trick?
The answer is a great jumping-off point for a discussion of basic physics, phase change, energy transfer, and more. As we are trying to get some attention and respect of younger students for science, technology, engineering, and math (STEM), to show them there is more to know and pursue than just playing with high-tech toys, this is one way to start them thinking about how it happens.
And it was done without batteries, without keyboard, without processor—just with basic materials. It’s a kind of magic, unless you know the trick.
And isn’t that the best kind? ◊