Why not copper pipes used?

[abhasib]

Sir,
I am a new heat engineering student. My questions are:

1) In a fire-tube boiler, why copper is not used for furnace body and smoke pipes inside the boiler? Copper is x15 time more thermal conductive.

2) Doesn't Iron pipe/ heating tank/ furnace need more fuel to heat up (for low thermal conductivity) and keep at high temperature?

 

[electrathon]

It will fail from the heat of the boiler.

 

[mike van]

You can't use copper for a steam system either, even outside the boiler as the joints will fail. Black iron pipe & threaded fittings.

 

[peakbagger]

Hopefully your education will include the history and ongoing use of the ASME boiler code. Its the "bible" for boilers including the materials that are allowable for construction. Iron is a somewhat generic term. In most cases iron pipe is actually a low alloy steel with a known material composition.

 

[tom in maine]

Heat transfer is based on thickness of the heat exchanger tube as well as its surface area. While playing with boilers at the University of Maine, most of the heat exchangers we used were copper. As long as they are wetted they work fine, same with steel or cast iron. And they are relatively cheap and easy to play with. Dry firing will destroy any heat exchanger in short order.
The bigger issue is potential erosion or corrosion on the outside of the heat exchanger.
And even bigger could be the wear and tear that might occur from any impacts on the heat exchanger.

We did mostly unpressurized boilers given code issues and cost. (Note how many boiler manufacturers do this to get around ASME.)

 

[Bad LP]

We did mostly unpressurized boilers given code issues and cost. (Note how many boiler manufacturers do this to get around ASME.)

Interesting. Never thought of it like that.