From what I can tell these people as selling a huge lump of metal. It's a F*CKING thermal mass. This isn't an invention of any kind. They simply took thermodynamics. It's kills me they made 22grand.
Not quite. They are taking advantage of the fact that matter takes (or releases) a lot more energy when it is changing state(eg. solid to liquid), then when it is simply changing temperature in the same state.
for example, water takes about 75J to heat one mol by 1K. but it takes
about 285000J to change one mol of ice to one mol of water
So, they have this lump of metal, that has a core of some other material that presumably changes state at the preferred temperature of coffee. What this means is that when the coffee is hotter than the joulies, the core melts absorbing a lot of energy. Then when the coffee is cooler than the preferred temperature, the core of the joulies re-solidifies, releasing a lot of energy, keeping the coffee warm.
It's a F*CKING thermal mass the same way that Twitter is a weekend project.
Weekend projects come and go with hardly a whimper. The hard part comes when you want to turn that weekend project into something people will actually use (or in this case, pay for). Creating a compelling brand, crafting a marketing message that resonates, designing the product so that it "feels" good to use, engineering something durable and long lasting, scaling to meet demand et al? These things require a heck of a lot more than a class in thermodynamics.
Regardless, the market has spoken and 300+ people saw enough value in this thermal mass to support it.
I don't think that is all there is to it. The page says they are filled with "Phase Change Material" (which I would guess is some sort of wax) that melts at !40F. I don't know why that would be better or worse than a lump of metal though.
It's much more likely to be a fusible alloy such as Wood's metal or Field's metal. My guess is that it's closer to Field's metal, since it is non-toxic and has a melting point very close to their advertised ideal.
They "simply took thermodynamics" and created a useful, beautiful product that solves a common problem and doesn't (as far as I know) exist yet. I don't understand what your issue is.
The keeping coffee "Hot" problem is easily solved with a good, insulated, transit mug. High quality ones will keep your coffee very hot for a couple hours.
What the Joulies do is _cool_ the coffee by initiating a phase change in their PCM, but then don't drop it too far down.
for example, water takes about 75J to heat one mol by 1K. but it takes about 285000J to change one mol of ice to one mol of water
So, they have this lump of metal, that has a core of some other material that presumably changes state at the preferred temperature of coffee. What this means is that when the coffee is hotter than the joulies, the core melts absorbing a lot of energy. Then when the coffee is cooler than the preferred temperature, the core of the joulies re-solidifies, releasing a lot of energy, keeping the coffee warm.