Jerry Rodberg

Heat pipe temperature limits

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I'm trying something unorthodox with a few Hyper T4's, but I need to know what is a safe operating temperature range for the heat pipes.  I'll be using them for temperature control, but I may be taking them above and below what they'd normally see in the normal applications.  This may involve bolting one on on each side of a TEC for a sealed air system idea.

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Baron    0

Given the well sealed nature of a heatpipe, its far more than likely you will overwhelm the cooler's base ability to effectively transfer heat and fry the TEC well before you get to the point where the heatpipe(s) are in danger of failing. Most TEC's have a max Tcase of around 70-95 degrees C.

If you are going to be pushing a TEC that far you are going to be better served by a water based unit for the hot side as will likely be easier to seal off from the cold side and will handle a greater load while keeping the TEC safe.

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This isn't going to be used on a CPU, so it's unconventional for this board.  You're right about the TEC maximum temperature, but there are high temperature ones that operate up to 200 deg C.  Either way, I'll have either RTDs or thermocouples all over this setup so I'll be able to both protect components and measure the heat transfer efficiency.

 

I'm also going to be pumping heat each way, so I'm perhaps more curious at what low temperature do the heat pipes stop operating at. 

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Baron    0

It all depends on the working fluid used inside the heatpipes, most heatpipes designed for general purposes use water as the working fluid as it is cost effective and allows sealing of the pipe without specialised equipment.

Given that it requires the working fluid to be vaporised in order for the heat-pipe to function correctly, you will likely have issues with temperatures around or below 0 degree Celsius. Below the vaporisation point the heatpipe will effectivly function as a mostly hollow copper pipe in terms of heat transfer - not well in other words.

My suggestion would be to use a solid (non heatpipe) cooler on the cold side - large solid Al heatsinks (MOSFET coolers for amplifiers etc) are cheap and easily available on ebay.

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Baron,

 

That's helpful, thank you.  I wasn't certain if it was water or some other working fluid in the pipes.  It could have been low vapor pressure ammonia or something else with a greater working range.  I was considering a solid heatsink, but the heat distribution across a high volume air duct wasn't ideal.  I was hoping to avoid any mechanical moving parts in the heat transfer mechanism, so back to the drawing board.

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