4 ms·

But any fire is magnitudes hotter than -50. That cold is a blip on the fire's radar. Once started, and as long as there's fuel and oxygen, it won't stop because

• foobarian 6y ago
  My uncle used to joke that his car ran better in the mountains because the air was cleaner and thus had more oxygen. He was not serious, but in case of cold air there would be more oxygen per unit volume due to density so that might improve the combustion.
  • munk-a 6y ago
    The air pressure is also higher at colder temperatures so if the fire is underground it'd have more forces working in its favor to cycle fresh air to it and the relative temperature difference between the freshly heated and exhausted air and the fresh air would be wider causing there to be more turbulence cycling the air around.
  • pletnes 6y ago
    Hence the invention of the intercooler diesel engine.
    • llampx 6y ago
      The turbocharger is what helps at high altitudes, not the intercooler which just cools the air. The turbo packs more air in to the engine, which helps at sea level but makes a big difference at high altitude. Superchargers do the same.
  • deleted 6y ago
    [deleted]
  • klodolph 6y ago
    Heat engines generate power from a difference in temperature. The larger the temperature difference, the more power. You can increase the temperature difference by making the heat source hotter or by making the heat sink colder.
  • mikestew 6y ago
    Ignoring, of course, the fact that "in the mountains" means an increase in altitude and thus a decrease in air density. My carbureted vehicles that were jetted for sea level always ran like shit in the mountains. And fuel injected vehicles run fine (because they can adjust for the altitude on the fly), but with noticeably less power. Apologies for pedantically deconstructing what your uncle meant as a smart-assed joke.
    • bigiain 6y ago
      Lower air density means old carburetted engines run leaner - which since most such engines are tuned to run slightly rich for reliability in favour of slightly lean, gives you more power up until the point they overheat and if they're a 2 stroke motor relying on the oil mixture in for lubrication the fuel, seize. One of the old traditional racetracks here in Australia is Mt Panorama at Bathurst. It's got about a 180m elevation change between the start/finish/pit straight and the top of the mountain. Back when they were allowed to race motorcycles there, old 2 stroke racebikes were notorious for seizing at the top of the hill if they'd been jetted down at the bottom and hadn't been set "rich enough" to allow for the altitude change. Many many riders crashed and said "It was running really strong, til it locked up on me and spat me down the road..." (No apologies at all for my off topic response to pedantry...)
      • mikestew 6y ago
        Mmm, pretty sure sea level carbs run rich at altitude. Less air means a need for less fuel for the same ratio. But the fuel side didn’t change because we didn’t rejet, so now too much gets pumped in. If I’m guessing the bikes might have seized at the bottom of the hill instead? Or it just took until the top before the damage was done.
        • bigiain 6y ago
          Ahhh, yeah - you're right. I've got it back to front there. In my defence it's been a long time singe they've been allowed to race motorcycles there. At least 20 years. And now you mention it I do recall bikes seizing at the end of pit straight, right down the bottom of the hill.
• Retric 6y ago
  It can significantly slow down wild fires which need to heat a constant supply of fuel to ignition temperatures. Wood burns at 180 degrees Celsius, so the difference between 20c and -50c is +160C vs +230C or over 40% more heat. This is especially impactful when looking at how easily sparks propagate fires across gaps.
  • jameshart 6y ago
    A typical wildfire is not putting much of its overall energy output into bringing fuel up to combustion temperature, though. The combustion energy in a kilo of wood is measured in megajoules; the amount of energy needed to elevate the temperature of a kilo of wood by a degree is measured in kilojoules. So while you're right that the energy budget needed to combust new fuel goes up by 40% or so if the fuel is at -50°C, the energy budget going into that is only a percent or so fo the total energy the wildfire is putting out. The rest of the energy beyond what's needed to bring fuel up to combustion point is going into making massive walls of glowing flames, mile-high convection columns of air, sending smoke thousands of miles, etc., etc... That is, in many ways, precisely what makes it a wildfire, rather than a smouldering ember. In the limit - when a fire is dying out - then I guess, for sure, changing the fuel temperature can sap a larger part of the energy budget.
    • Retric 6y ago
      The point is propagation speed. A burning tree surrounded by acres of burning trees is largely irrelevant at that point. It might happen to produce spark that travels miles, but that’s relatively rare. Which is why firebreaks can be useful.
• why_Mr_Anderson 6y ago
  It's actually one way of putting out otherwise very persistent fires, especially the ones that like to only smoulder (really nasty chemicals, metal compounds, etc.) Removing heat from the reaction lowers the ignition temperate of the surrounding material to a point that fire dies out on its own. Side note: it doesn't work that well on burning plutonium.