C210_Flyer wrote:
Regarding radiational cooling. There is a measurable amount of heat lost through the props. So it makes sense to put insulated prop covers on …
Sorry to be nitpicking here (had to study lots of thermodynamics in a previous life) but “radiation cooling” is absolutely no factor here, especially with regards to the propeller. In order to be dissipated through the propeller, the heat of the engine must first be conducted through the propeller shaft (made of iron, a rather poor conductor for heat) and hub to the blades. At best their temperature will be five or 10 degrees (Celsius) above the environment. At those low temperatures and temperature differences, heat transfer by radiation is negligible. But of course the blades will be cooled down to environment temperature by convection rather quickly. Therefore a thermal insulation certainly makes sense. But only after the engine compartment is totally sealed off, because the major heat loss will occur there.
It ought to be not too hard to get some rough figures, knowing the surface area, the initial delta-T, the thermal mass (~200kg for an IO540).
Start with 50mm of celotex insulation 
The outside surface should be silver.
I know how to work out a delta-T per watt of heat generated on one side of a barrier made of a given material for which the degC/watt is published. But this is more involved, plus the logarithmic (decay) cooling.
in cold and humid hangars where temperature changes through winter are condensing water on unheated metal-surfaces the insulation blanket on cowling and 50W handheld light with protected bulb through oil door is small and simple solution to keep condensation away. Consumption only 150 kWh/4months
Ah, that famous heat bulb which my ancestors had talked of, later outlawed by the European Union. 
In what way should it be a “protected” bulb?
Rwy20 wrote:
later outlawed by the European Union.
Honestly? Banning 100W lightbulbs (which convert 95 percent of the electricity, itself generated with an efficiency of not more than 30 percent from coal or nuclear fission, into heat) was the smartest thing they ever did. Without that directive, LED lighting, which is now the standard everywhere, would still be 10 years in the future.
I’m afraid we will quickly derail the thread, but I don’t like the approach to ban stuff that isn’t in itself harmful. And I don’t like LED light because it flickers; I recently bought some and immediately threw them away because I couldn’t stand the flickering. I have other LED bulbs of apparently higher quality where I don’t perceive the flickering, but when you measure it, it is still there. I don’t know what that does to your brain activity if you use it in the long term, but I wouldn’t be sure it has no effect.
If you want, tax energy until that compensates for all the negative external effects of energy production, but I don’t like this micro-management approach of other people deciding for everyone else what light sources they should use.
Rwy20 wrote:
I have other LED bulbs of apparently higher quality where I don’t perceive the flickering,…
The good ones have a capacitor (which adds 10 cent to the price, obviously too much for the cheaper suppliers) which completely prevents the flickering. I believe in regulations, I am a child of the European Union
The good ones have a switch mode power supply which feeds the LEDs with smooth DC. That gives you the best efficiency. But that needs inductors and capacitors – it cannot be done without them. It is even more pricey if you want them dimmable and efficient and non-flickering.
Unfortunately whenever the EU regulates something, 93.75% of people making stuff will find ways to get around it just about comply. So you get crap like flickering LED lamps, LED lamps whose efficiency is way below what it should be, and fluorescent lamps which claim to have the 5000hr life but actually do 500-1000hrs. I have some very low wattage exterior lights on the house which run all the time it is dark and in 17 years not one of them has made 1000hrs. All of it ROHS and REACH compliant and CE marked of course. It’s a damn big con, unfortunately. Plus the fluorescent lamps give out UV which does retina damage.
The point about a 50W or a 100W bulb under the cowling is a good one. With a wire shroud around it, it is a cheap and safe way to keep the cowling contents warm.
In fact I did think of using a power resistor, as described here, but screwing it to the bottom of the sump is another “little exercise” which is very nontrivial…
The biggest problem, which I guess they have solved in the cold countries where hangarage is also available, is electricity availability. I have never had the ability to plug something into the mains, even inside a hangar. It simply was never allowed. The power socket might be next to the plane but I was never allowed to use it. And this is fairly common, I know. It all depends on the airfield situation and politics.
what_next wrote:
Honestly? Banning 100W lightbulbs (which convert 95 percent of the electricity, itself generated with an efficiency of not more than 30 percent from coal or nuclear fission, into heat) was the smartest thing they ever did. Without that directive, LED lighting, which is now the standard everywhere, would still be 10 years in the future.
For us who have “green” energy production LED or not makes no difference whatsoever. Take a look at this"this":https://electricitymap.tmrow.co online map (on a PC)
LeSving wrote:
For us who have “green” energy production LED or not makes no difference whatsoever.
Lucky “you” “We” lead the European continent with 30% “green” electricity production, so saving electricity makes a lot of sense for us. Recently they replaced all the lamps (I think they were sodium gas discharge lamps) in our hangar with LED ones. Much more even light with perfect colour, zero flicker, no two-minute warm-up time and half the electricity consumption as before. Not driven by the EU (sodium lamps are still approved) but by common sense.
