The Steamboating Forum

Quote: "I might get so interested in this question that I produce a small test rig, in order to actually measuring the difference "

When I get time, I have the parts to do this, a 6" long steel pipe and copper pipe of the same size, pressure gauges, thermocouple etc. My guess is, I'm wrong about this, but I'd like to see anyway and then I can stop questioning it.

Fred, Your analogy makes sense, where the wall is really an insignificant part of the process. Water can be boiled in a paper cup, which somehow makes the barrier wall between the heat and water insignificant in regards to rate of heat transfer.

Was talking to one of my steam buddies this morning and he said he didn't really know and mentioned that he understood some British Locomotives (LMS) used copper fireboxes and flues at one time and then went to steel. Judging by their attitude of efficiency in their old British transport films, if there was an advantage and savings by using copper, they would have continued.

-Ron

I managed a few minutes today to do some preliminary testing, I'll post video this evening.

Used two schedule 40 pipes 1/4" NPT X 6" plugged one end on each and added a pressure gauge at the other, then held it horizontal and aimed a propane torch at a point on it's center. One of steel, one of "copper" although I think that one is actually red bronze which is made of copper.

In each I placed 5ml of water and set the dial on the propane torch at the same position for each test.

I made sure all components including the propane tank were at ambient temperature at the beginning of the tests measured with a Fluke infrared.

The copper pipe made 30psi in 2 minutes 30 seconds. The steel pipe made 30 psi in 3 minutes 55 seconds. But there is more to that.

The two behaved much differently. Heating a spot on the steel pipe made the water push away to the unheated ends of the pipe. The pipe glowed red at the heated point and the gauge was not rising on 20, it took another minute and a half to raise it up to 30 psi.

In the copper pipe the pressure rose steadily up to 30 psi, I think the reason being the heat traveled through the copper and heated the whole pipe more evenly. The steel not transferring heat as fast, the ends of the pipe remained colder much longer. The copper pipe did not glow red during the test.

I'm going to try the test again with 10ml of water.

Not sure how conclusive this was and what variables I'm not taking in to consideration. One of the things missing was convection heat on the remainder of surfaces away from the flame.

I'm not claiming anything, just reporting the results and method used of the rudimentary tests.

-Ron

The report above, there was obviously not enough water to come to any sort of definite conclusion, it was being boiled away at the point of heat.

Ran the same test again with 10ml (About half the volume of the pipe) of water and took both to 50 psi, results:

Copper 1 minute 58 seconds.

Steel 1 minute 55 seconds. (This may have been due to the Bourdon tube of the gauge being about 10 degrees warmer for this test)

In this test, the steel was actually a bit better.

-Ron

Ron,

I saw your test on the youtubes...

I think the gauge having heat from the copper/brass test influenced the steel test.

The bourdon tube in the gauge probably could hold as much water as the "boiler"/pipe in your test.



-CB

P.S. I double posted with Ron, Please Reply to Ron's New thread about his video: Copper vs Steel boiler components