Any idea of heat buildup with teflon on copper friction?

rocketmanx · 02-02-2004, 10:38 AM

Was wondering if anyone knew the amount of heat that could be expected, if any of signifcance, from a small 1/4" teflon edge rubbing against copper. This is of course while being submerged in water.
Reason I ask is I mentioned the idea of a "scraper" of sorts which would essentially wipe away most of the boundary layer and keep a "pulsating supply of new/cool water to the copper. I was told that someone else had the idea too but to no real results. I had an idea over the weekend of how to do this without any external mechanisms and with a frequebcy of "wiping" that increases with flow rate. That probably gives away that idea. Whether it's any good or not, I can't say. But it looks good in drawings

myv65 · 02-02-2004, 01:04 PM

Power is work divided by time. Work is force times distance. Take the force applied between the teflon and copper. Multiply by the coefficient of friction. That's the tricky part, but for wet teflon on copper, I'd start with 0.05 or so. The result will be the drag force. Now multiply by the speed (distance divided by time). The answer will have units of force * distance / time, which is the same as power. If you're working in English units, 1 horsepower is 550 ft-lbf/sec. In metric, things are much easier as 1 N-m/sec = 1 watt.

The coefficient of friction should be between 0.01 and 0.1, but the exact value depends on surface finish and temperature, among other things.

rocketmanx · 02-02-2004, 01:30 PM

Thanks, but the amount of force I have no number for really. As for the coefficient of friction, thanks for the number I have no way of knowing that number. Maybe an internet search but I figured with so many guys here with so much experience with this stuff I thought they may have a close approximation. Your guesstimate is close enough for now. That's a negligible number. I have most of the formulas but no access to the numbers to plug in. I have all my old text books but no other resources handy. Although equations are far from the tip of my tongue after 20 years

Thanks for the reply, with the very limited amout of force it would probably be seeing it's probably next ot nothing. I'll press on anyway, I just gotta have something to fiddle with

lolito_fr · 02-03-2004, 04:03 AM

I'm thinking "flow meter in a waterblock" type thing. Warm?

If so, another way to look at things is to consider the amount of power available in the flow of water. You're only going to use up a small fraction of this (hopefully) to drive the rotor and rub the blade against the copper.

interesting experiment

02-02-2004, 10:38 AM	#1
rocketmanx Cooling Savant Join Date: Nov 2003 Location: Indiana Posts: 127	Any idea of heat buildup with teflon on copper friction? Was wondering if anyone knew the amount of heat that could be expected, if any of signifcance, from a small 1/4" teflon edge rubbing against copper. This is of course while being submerged in water. Reason I ask is I mentioned the idea of a "scraper" of sorts which would essentially wipe away most of the boundary layer and keep a "pulsating supply of new/cool water to the copper. I was told that someone else had the idea too but to no real results. I had an idea over the weekend of how to do this without any external mechanisms and with a frequebcy of "wiping" that increases with flow rate. That probably gives away that idea. Whether it's any good or not, I can't say. But it looks good in drawings __________________ "The more I learn the less I know, but I never knew as much as when I was sixteen"

02-02-2004, 01:30 PM	#3
rocketmanx Cooling Savant Join Date: Nov 2003 Location: Indiana Posts: 127	Thanks, but the amount of force I have no number for really. As for the coefficient of friction, thanks for the number I have no way of knowing that number. Maybe an internet search but I figured with so many guys here with so much experience with this stuff I thought they may have a close approximation. Your guesstimate is close enough for now. That's a negligible number. I have most of the formulas but no access to the numbers to plug in. I have all my old text books but no other resources handy. Although equations are far from the tip of my tongue after 20 years Thanks for the reply, with the very limited amout of force it would probably be seeing it's probably next ot nothing. I'll press on anyway, I just gotta have something to fiddle with __________________ "The more I learn the less I know, but I never knew as much as when I was sixteen"

02-02-2004, 01:04 PM	#2
myv65 Cooling Savant Join Date: May 2002 Location: home Posts: 365	Power is work divided by time. Work is force times distance. Take the force applied between the teflon and copper. Multiply by the coefficient of friction. That's the tricky part, but for wet teflon on copper, I'd start with 0.05 or so. The result will be the drag force. Now multiply by the speed (distance divided by time). The answer will have units of force * distance / time, which is the same as power. If you're working in English units, 1 horsepower is 550 ft-lbf/sec. In metric, things are much easier as 1 N-m/sec = 1 watt. The coefficient of friction should be between 0.01 and 0.1, but the exact value depends on surface finish and temperature, among other things.

02-03-2004, 04:03 AM	#4
lolito_fr Cooling Savant Join Date: Dec 2003 Location: France Posts: 291	I'm thinking "flow meter in a waterblock" type thing. Warm? If so, another way to look at things is to consider the amount of power available in the flow of water. You're only going to use up a small fraction of this (hopefully) to drive the rotor and rub the blade against the copper. interesting experiment

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)