I've been half-seriously thinking about trying to make them, without a wick, probably, for simplicity of manufacturing. You may call them thermosiphons or thermosyphons if you like.
- buy a small diameter metallic tube(s) and cut them to proper length
- hit one end of the tube shut with a hammer and then solder it tight
- fill with proper amount of water
- keeping it upright, hammer the top end shut too
- heat the lower end of pipe until it boils and steam starts to escape from non-soldered end
- now solder that other end so that it's both water and airtight.
There should be only water vapor inside. Since it was at boiling point at ATM (100 deg C) there will me significantly lower than ambient pressure inside the tube when it cools down so proper sealing is extremely necessary (I wouldn't trust thermosiphons that transmit steam and condensed water via plastic tubes since the joints are just pressed shut - not soldered).
I think such tubes are available from hardware stores (typical plumbing sizes) and some hobbyist stores (even very small diameters). Copper, brass, aluminum... I wouldn't care what it is since it's single metal so no galvanic corrosion should occur. I just want it to be solderable with normal tin+lead or tin+silver soldering wire and a blowtorch (because there's no soldering iron capable of heating the pipe hot enough to make a realiable solder).
Anyone of you done such a thing? If so, what material was your pipe? If not, do some of you have experience on soldering (big) components that don't have tin-covering on them?
Here's a list of fillings for heatpipes copy-pasted from a D.I.Y. heatpipe thread from Finnish murobbs forum (it's not original research so they copy-pasted it from some place else, I don't know where):
MEDIUM MELTING PT. BOILING PT. AT ATM. PRESSURE. USEFUL RANGE
Helium -271 -261 -271 to -269
Nitrogen -210 -196 -203 to -160
Ammonia -78 -33 -60 to 100
Acetone -95 57 0 to 120
Methanol -98 64 10 to 130
Flutec PP2 -50 76 10 to 160
Ethanol -112 78 0 to 130
Water 0 100 30 to 200
Toluene -95 110 50 to 200
Mercury -39 361 250 to 650
Sodium 98 892 600 to 1200
Lithium 179 1340 1000 to 1800
Silver 960 2212 1800 to 2300
I have no idea the original creators of that table came up with "useful range" because that depends on amount of substance inside the tube. I'd choose plain water... maybe with small amount of normal antifreeze glycol since they also contain corrosion inhibitors to prevent car engines from rusting from the inside out. Ethanol wouldn't be bad either but I'd stay away from acetone since I'll be boiling it before sealing the pipe and don't want to get toxicated doing it in a poorly ventilated household.
I read many of the posts there but they were creating plastic heatpipes with flexible hoses... they also had a low-pressure pump to depressurize it and due to leaks in the system, had to be depressurized frequently.
I want a permanently sealed, all metal heatpipe (without a wick is OK too). If I could buy heatpipes from a store, I'd be happy with that (because they only cost around 2 eur each and would have a wick) but the problem is that in reality I'd have to order hundreds of them since I'd have to contact the manufacturer itself. DIY is probably the only reasonable way to obtain heatpipes in small quantities.