Dead Leg Freezing Versus Thermosyphon

[ChemEngSquirrel]

I have a 12" water pipe flowing at 50deg C with a long 2" vertical dead leg in the 12 o'clock position. Can i rely on the thermosyphon effect (hot water rising into dead leg due to high density) to justify not heat tracing the 2" stagnant line.

The line can be exposed to min ambient temps of -15 deg C.

Thanks.

 

[Compositepro]

I don't think, because the water has to rise and fall in the same pipe. Warm water will rise up the center and fall at the pipe wall and the streams will be exchanging heat at the same time. It will work to some limited extent, but I wouldn't count on it.

 

[MortenA]

I would say that 2" is too small and that it should be heat traced

 

[LittleInch]

A "long" 2" - 2 INCH?? If it is 2" I would just insulate it and rely on heat conduction through the pipe wall to prevent freezing. The water might not be a 50 C, but shouldn't freeze.

If it is 2 FEET, then no, a 2" pipe won't conduct enough heat to prevent this and you need to trace heat this line.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[LittleInch]

Sorry, I read this as 2" long dead leg.... I should re-read before posting, but the point applies - what is "long"?

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way