Re: What happens when 70 F water runs through 350 F pipe?

I can give you some general information with regard to heating water running 
through pipes and so forth.

HOWEVER, this general information is NOT a substitute for real safety 
advice; it is not the role of the MadSci Network to provide such advice. (In 
fact, in my opinion, it is generally a pretty bad idea to try and get safety 
advice over the Internet)

So, if you have a real safety concern here, you need to find an engineering 
professional who can assess the specifics of your situation, perhaps 
starting by consulting the manufacturer of the oven.

With that said, the answer as to what will happen in this situation is "it 
depends".  Of course water will boil at about 212 degrees Fahrenheit.  So it you 
just had water sitting in the pipe, or moving through very slowly, it would 
start to boil, generating steam and (depending on the arrangement of things) 
potentially bursting the pipe or doing some other nasty thing.  But, if the 
water is flowing quickly enough, it may not have time to absorb enough heat to 
boil, so it might just get warmer.  [An example of this is the cooling system in 
your car's engine, where some of the engine would be above the boiling 
temperature of the coolant but it is not a problem as long as the coolant 
continues to circulate.]

A final thing to mention is that, in assessing possibilities in such a 
situation, you should also consider whether any part of the system might shut 
down.  If the water is flowing but there is some way the water might stop while 
the oven is still hot, a dangerous situation could be created.

Allan H. Harvey
"Don't blame the government for what I say, or vice-versa."