DocD

What type of griddle do you mean, panini-press type, stovetop, electric or gas countertop, or what? I've looked into this myself a little before, I have a love/hate relationship with my aluminum Calphalon stovetop griddle LOL The practical aspects of the engineering make it increase rapidly in cost, depending on what you require from it - this is a much more difficult range to work in compared to cooling electronics. What would people be willing to pay for a griddle that heats a lot more evenly? Even just a 1/4" sheet of plain copper 12x24" would cost $750 - and that's without handles or any particular finish, and it still wouldn't be as evenly heated as something with heat pipes. 1/2" aluminum would cost $250 and not work as well as copper.

Easy - having someone else cook! I haven't tested them side by side, but I probably should, given my collection. Thermodynamically, the fins on the King Pin make sense... but a very simplistic, informal test hinted that heat didn't transfer as fast as the others. But I should cook 3 roasts to test them... Fun fact - the same principles help conduct heat into porous foods, too, like bread - evaporation at the hot surface then condensation at the cooler interior, whether that's a thousand small gas bubbles in bread or the interior pocket of a larger thing like a popover. It just doesn't happen as much as in the pressurized tubes in the King Pin etc.

I collect these pins, and have the Hot Rod, Space Age Cooking Pin, Thermo Pin Potato Baker, and & the aforementioned King Pin, ALL of which are heatpipes. Note that unlike the others, the King Pin has a large heatsink on the outside end to increase heat flux into the pin. The thermometer in it doesn't just report the heat around the outside end - it very much responds to the inside temperature; perhaps it's tied to expansion of the internal heatpipe. These pins are far more effective than you might imagine, despite the issues mentioned like small surface area, low air density, etc. The proof is in that graph initially posted by the OP / @Rho - the pin decreases the time to reach temperature by almost threefold, regardless of those issues. That's real data that supercedes any supposition about those issues. Note also it addresses the comment by dcarch - the cooling is indeed also shortened, as seen in the second part of each curve, though it's less effective in this direction for the reason identified by @dtremit. This cooling is in fact used for industrially-processed meat, to reduce the time to bring it closer to refrigeration temperature by "more than 25%".

I think the true heat-pipe thermal pins mentioned by the OP (Rho) were ahead of their time and therefore mostly unappreciated by their target audience and their copycat competitors with the aluminum nails, plus the results were a little strange too - your medium-rare roast would have the more-done gray on both the outside AND in the center around the pin, with a donut of pink between those; slices would certainly look a bit "space age" IE Martian! That does answer one question above - the meat thermometer should ALWAY be put in the slowest-heating part of the cooked item; for normal roasting, that would be the center, but with the pin it goes halfway between pin and surface (the instructions enclosed with the pin explicitly state this). The aluminum potato nails may have also been part of the thermal-pins downfall because to the unaware eye, they look similar - but function SO much more poorly as Rho said. The aluminum can get just as hot, as AlaMoi mentions - the difference is in the total heat flux (NOT temperature), the aluminum carries only 1% of the heat energy, is slower, and looks to be of little use. For a potato, this isn't a huge deal. For a 25# raw turkey, it is. Competitors could pump out aluminum nails for pennies, while the heat-pipe pins actually require somewhat serious engineering due to the forces involved (a computer heat pipe is nowhere near as extreme). The consumer, however, wouldn't see this on the product page, only the price difference - so I suspect they'd buy the cheaper one, find it didn't work well, and write the whole thing off. I own 2 heat-pipe pins, and they work exactly as advertised - half the cooking time: 20# turkey can be cooked in 90 minutes with a heat pipe pin in each side. These days I actually see them referred to more in COOLING large cuts of meat to stop cooking and/or expedite storage, they halve the cooling time also. The little experiment AlaMoi mentions doesn't mention a heat pipe. An aluminum nail takes at least 10-20 seconds for the heat to get to the other end. Using my heat pipe pin and boiling water, it gets too hot to hold in 1-2 seconds. (I ran across this thread looking for info on the pins, and wanted to contribute to the searchable history.)