Heat Pipe Lifespan? 1

[generalpatton]

Howdy,
Our company has historically only needed passive extrusions for thermal management. We're now getting into heat pipe assemblies for our cooling needs.

Here are a few general questions I have:

1. Assuming a heat pipe assembly is operated within its limits, how long would you expect it to function at 100% of its capacity?

2. What are the normal failure mechanisms? Release of working fluid, fluid contamination, wick structure breakdown, etc.?

I am trying to get a feel if we should plan for scheduled maintenance 5, 10, 15 yrs, etc., down the road.

Thanks for any help.

 

[IRstuff]

There seems to be lots of articles about this on the web:

http://www.1-act.com/pdf/heat-pipe-product-reliability-guide.pdf

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[generalpatton]

Thanks. I've gone through that and several other articles. I'm really more interested in input from the end user and their experience.

I've received varying estimates from lots of sales guys...5 yrs, 10 yrs, 15 yrs. Our particular project could have a lifespan of 20 yrs. So I'm trying to find out if a heat pipe assembly is a good fit for us. Thanks for the input.

 

[davefitz]

Well, I recall one used for a power plant primary airheater in 1991 that lasted a grand total of 2 days following commissioning. Apparently, an anti-corrosion additive broke down into twice as many molecules, which led to overpressure of the individual pipes , which caused the end caps to be shot off and these projectiles wereflying all around the plant. It basically put an end to the heat pipe market at US powerplants.

It is my understanding that corrosion is the main issue if it is corectly designed and operated- to maximize heat transfer, the thinnest wall thicknest permitted is used , and corrosion thru the thin wall sets the useful designlife.

 

[btrueblood]

Various spacecraft over the years have used heat pipes to radiate waste heat from various high-power components. These have demonstrated design lifetimes in the 10-20 year range. Heat pipes, with ammonia fill fluids, have worked to control heat rejection to the permafrost underlying the trans-Alaska pipeline, since 1977. If memory serves (comments made by instructor in a spacecraft design class some 20 years ago), the predominant failure mode for the Alaksa pipeline heat pipes has been rifle bullet impacts (they make a lovely bang when they pop, apparently staving off boredom of Alaskan hunters). Barring corrosion concerns of the outer shell as DaveFitz points out, or thermo-mechanical cracking of the shell, or fouling/chemical degradation of the fill fluid, there should be little else to go wrong.