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I’m not entirely sure how you’ll cool the engines at high altitudes, combustion engines can use their exhaust to cool the engine. Using large radiators on an e

I’m not entirely sure how you’ll cool the engines at high altitudes, combustion engines can use their exhaust to cool the engine. Using large radiators on an electric engine kinda defeats the purpose especially when they can’t be effectively be built into the body of the engine.

jandrese 7y ago
I'm not sure why largeish passive radiators are a problem. If you're worried about the aesthetics you can put them inside of ducts and pass the air over them. This doesn't seem like it should be that big of an issue. Plus you'll probably want to recover some of that waste heat to heat the cabin.
xyzzyz 7y ago
How exactly does one use exhaust to cool the engine? This is something I've never heard of in the context of cars of motorcycles, where exhaust is generally removed as soon as possible, and if it's used for anything, it's for running turbochargers that make the engine even hotter.
- FabHK 7y ago
  Not sure what GP was referring to, but they might have had in mind the practice to run engines a bit too rich, so that fuel runs through the system with insufficient oxygen to burn, ie as a liquid, which cools the engine.
- stevehawk 7y ago
  There are two strategies for keeping cylinders cool in cruise: push the red mixture knob forward for a rich fuel/air mixture setting that uses unburned fuel to lower cylinder head temperatures, or pull the mixture knob out to such a lean setting that an abundance of air and reduction in engine power and heat cools the cylinders. Running aircraft engines “lean of peak” (LOP) typically reduces airspeed about 5 percent in cruise while lowering fuel consumption about 20 percent—but not all engines are capable of LOP operations, and doing it wrong can cause permanent and costly engine damage. source: https://www.aopa.org/news-and-media/all-news/2019/may/flight-training-magazine/technique-lean-of-peak https://www.aopa.org/news-and-media/all-news/2019/may/flight...
yetihehe 7y ago
Nope, combustion engines generate MUCH more heat than electric engines. Also they don't use exhaust to cool the engine, with all due respect, your argument is entirely backwards. It will be easier to cool electric engines and they will need smaller radiators (if any, have you seen radiators on engines in drones?). More probable is that you will need to heat batteries so that they don't freeze at higher altitudes.

jandrese 7y ago

I'm not sure why largeish passive radiators are a problem. If you're worried about the aesthetics you can put them inside of ducts and pass the air over them. This doesn't seem like it should be that big of an issue. Plus you'll probably want to recover some of that waste heat to heat the cabin.

xyzzyz 7y ago

How exactly does one use exhaust to cool the engine? This is something I've never heard of in the context of cars of motorcycles, where exhaust is generally removed as soon as possible, and if it's used for anything, it's for running turbochargers that make the engine even hotter.

FabHK 7y ago
Not sure what GP was referring to, but they might have had in mind the practice to run engines a bit too rich, so that fuel runs through the system with insufficient oxygen to burn, ie as a liquid, which cools the engine.
stevehawk 7y ago
There are two strategies for keeping cylinders cool in cruise: push the red mixture knob forward for a rich fuel/air mixture setting that uses unburned fuel to lower cylinder head temperatures, or pull the mixture knob out to such a lean setting that an abundance of air and reduction in engine power and heat cools the cylinders. Running aircraft engines “lean of peak” (LOP) typically reduces airspeed about 5 percent in cruise while lowering fuel consumption about 20 percent—but not all engines are capable of LOP operations, and doing it wrong can cause permanent and costly engine damage. source: https://www.aopa.org/news-and-media/all-news/2019/may/flight-training-magazine/technique-lean-of-peak https://www.aopa.org/news-and-media/all-news/2019/may/flight...

yetihehe 7y ago

Nope, combustion engines generate MUCH more heat than electric engines. Also they don't use exhaust to cool the engine, with all due respect, your argument is entirely backwards. It will be easier to cool electric engines and they will need smaller radiators (if any, have you seen radiators on engines in drones?). More probable is that you will need to heat batteries so that they don't freeze at higher altitudes.