Forced Convection

[weeber]

Hey all,

I've got a question that I've been struggling with and maybe someone here can help me.

I have a stainless steel pipe with water flowing through it that's going to be exposed to a controlled fire. I need to calculate the outlet temperature of the water at the end of the pipe.

The water flowrate, pipe diameter, fire temperature, and inlet water temperature are all known. Since it looks like the flowrate of water in the pipe will put it in the laminar flow regime, I was considering using the Seider-Tate relation and assume a constant wall temperature equal to that of the fire. But this poses a problem because the fire is burning at a temperature higher than liquid water will actually exist, and I'm not sure if it's possible to use Seider-Tate with this condition.

Is there a better to go about solving this problem? It seems like I might be making this more complicated than it is, so anything that makes my life easier would be greatly appreciated.

Thanks.

 

[vpl]

Is the pipe going to end at the fire or it just passing through? Is the fire continuously there (and how do you know your fire will stay at the same temperature?)

Seems that the whole phase-change thing would interrupt any laminar flow you have going.

Patricia Lougheed

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[weeber]

VPL,
1. The pipe is just passing through.

2. The fire will be continuous. This problem is for an aircraft-rescue training facility, which simulates a burning aircraft for rescuers to practice on. Design guidelines for such facilities say all components shall be designed for a maximum temperature of 2,100-F. That's the temperature I'm working with.

Basically, I have a 12" diameter pipe with approximately 12' of length exposed to the fire. I want to make sure that over this 12' length I don't turn all the water in the pipe to steam. I know some steam will be generated on the walls of the pipe, but I want to keep the bulk temperature of the water at the end of the pipe at about 200-F (it's entering at 50-F).