What's the effect of ...

Methods of cooling laser tubes

What's the effect of ...

Postby twehr » Fri Mar 02, 2012 12:35 am

Bubbles in the cooling system? More specifically, what is the effect of bubbles attached to the glass inside the laser tube?

bubbles.jpg


Note: large air bubbles pass right through the system without a problem. It is only the smaller ones, attached to the inner surfaces of the tube's cooling chamber, that I am concerned about.

What I am seeing (and hopefully attributing to the bubbles) is a gradual loss of power over a longish engraving job. The jobs start out fine, but after 15 minutes or so, begin to loose power. Waiting a sufficient amount of time and starting over produces similar results. BTW - the water NEVER gets warm, let along hot. Since the bubbles are lining the tube, is that allowing the tube to be hot and loose power while the water passes right through without being affected?

Along with everyone's speculation as to the effect, I am open to suggestions for eliminating them. I believe they are caused by organic growth in the water that is contaminating the inner surface of the tube's cooling jacket. I now have an algaecide but believe I need to "clean" the tube first. I did add some bleach this afternoon and am letting it circulate. We'll see what happens.

I have a new tube coming, but really want to figure this out before I put it in. Don't want to potentially damage yet another tube.

All suggestions and comments welcome.
tim
--
"The answer is usually easy and obvious once you know what it is." tw

DIYLaser Blog
SemiHomemadeTools.com
twehr
 
Posts: 439
Joined: Mon May 24, 2010 4:49 pm

Re: What's the effect of ...

Postby frob » Fri Mar 02, 2012 2:51 am

Not sure it will work, but
you might try a wetting agent -
they add that to automotive antifreeze i believe for similar reasons -
Ive seen it sold in auto parts stores as a separate additive for racing enthusiasts.
"water wetter" or something similar i think was the name.

http://www.redlineoil.com/product.aspx?pid=74&pcid=10

"Reduces or eliminates bubbles or vapor barrier that form on hot metal surfaces to reduce coolant temperatures by up to 20°"
frob
 
Posts: 260
Joined: Tue Jan 31, 2012 6:24 pm
Location: Montreal, Quebec, Canada

Re: What's the effect of ...

Postby artofmystate » Fri Mar 02, 2012 5:13 am

What kind of flow rate are you seeing with your setup? What pump are you using?

If the flow rate is high enough, those bubbles should be pushed out with a quickness.
artofmystate
 
Posts: 17
Joined: Thu Jan 19, 2012 9:27 pm

Re: What's the effect of ...

Postby AndrewR » Fri Mar 02, 2012 6:43 am

The bubbles just look like dissolved gasses in your water coming out of solution.

http://www.education.com/science-fair/a ... tap-water/
AndrewR
 
Posts: 22
Joined: Sun Feb 12, 2012 9:23 am
Location: Seattle, WA

Update

Postby twehr » Fri Mar 02, 2012 3:42 pm

After several hours of running the bleach/algaecide/water mixture, about 90% or more of the bubbles are gone.

Less Bubbles.jpg


I don't have any video of the flow rate from before, but here is a few seconds of video now. It looks to me to be at least double (if not quadruple) what it was.

http://www.youtube.com/embed/L28J1wJZx3c

I need to dump all the old water and refill, as it has turned quite cloudy with the gunk it collected.

Tonight or this weekend, I will see if there is any difference in how the laser performs.

Still haven't heard anybody speculate on the actual effects of the bubbles.
tim
--
"The answer is usually easy and obvious once you know what it is." tw

DIYLaser Blog
SemiHomemadeTools.com
twehr
 
Posts: 439
Joined: Mon May 24, 2010 4:49 pm

Re: What's the effect of ...

Postby StigOE » Fri Mar 02, 2012 4:30 pm

I have noticed that every time I start the laser, there is quite a bit of air around the water intake on the tube, even if both the pump and outlet hose is fully submerged. Anyone have any idea where all the air is coming from? I'm using distilled water with some anti-freeze.
StigOE
 
Posts: 96
Joined: Thu May 12, 2011 9:08 pm
Location: Norway

Re: What's the effect of ...

Postby frob » Fri Mar 02, 2012 4:43 pm

StigOE wrote:I have noticed that every time I start the laser, there is quite a bit of air around the water intake on the tube, even if both the pump and outlet hose is fully submerged. Anyone have any idea where all the air is coming from? I'm using distilled water with some anti-freeze.


There is actually a fair amount of air that dissolves in the water. that explains how fish can live :)
Cold water can hold a lot more air in solution than hot water. heat up the water, the air bubbles out.
To avoid that, keep the system completely sealed and provide a means to extract air bubbles at the pump ,
like a plumbing air trap that are used in residential hot water heating systems.
it also helps in preventing algae/mold etc. to get rid of the oxygen & minerals in the water - distilled or demineralised is better.
frob
 
Posts: 260
Joined: Tue Jan 31, 2012 6:24 pm
Location: Montreal, Quebec, Canada


Return to Cooling

Who is online

Users browsing this forum: No registered users and 3 guests