A/C Basics?

[MarkS]

I am in the process of building my first computer and I want to do water cooling. After giving it a lot of thought and doing a lot of research, it looks like using a small 5000 BTU A/C unit to cool the liquid will be the best route. Since this is my first computer, I do not want to do a true phase change system. However, I would like to know any and all details of modding the A/C unit.

What I plan on doing is replacing the evaporator with a copper coil in a PVC pipe. The coolant will run through the pipe. The fabrication is simple and I've done much more complicated fabrication on aquarium systems. What I need help with is the evacuating/charging/etc of the system. I've read many threads and done many searches (here and internet), but all I've found are bits and pieces of data and nothing solid and cohesive.

As I understand it, after the fabrication is done and everything has been brazed, I need to vacuum out the system, charge it with nitrogen to 200 - 300 PSI, discharge the nitrogen, vacuum out the system and hold a vacuum for a couple of hours and repeat a few times to remove any air and moisture. Is this correct? If so, after this is done, to what pressure do I charge the unit with Freon(I know, general term...)?

Also, what it that tool called with three tubes and two gauges? How, exactly, does this tool help me? What are the three lines for? I think I've read that one is for vacuuming, one is for charging and the other is for...?

I hate to post such a newbie question, but I'm a newbie. We all have to start somewhere, right?

 

[XeonStrikeForce]

http://www.refrigerationbasics.com/1024x768/rb1.htm < Read this.

Yes Vacuuming is realy important for best quality use a porper vacuum pump for acceptable quality use a couple low temp compressors in series.

Guages (Manifolds) Can be easily purchased on Ebay, but beware geting refrigerant isn't easy.
You WILL have to replace the oil with wthe corect type for the refrigerant.

Now that I read your post I'm shacking my head going you are way over your head and need to learn more if your discribing the manifold like that.

 

[XeonStrikeForce]

http://www.refrigerationbasics.com/1024x768/rb1.htm < Read this front to back to front again, untill your dreaming about it.

Then if you have yahoo come and lets talk and I'll give you all the relivant links, but start with the above untill you understand it inside and out.

 

[MarkS]

Thanks for the link. Yes, I am getting in over my head. Clearly, I need to learn a whole lot more.

I'm still going to go ahead with this project, but that is all it will be. For the cooling system, I'm going to buy a used aquarium chiller.

 

[crimedog]

instead of throwing you a bunch of links and discouraging you what he should have done is tell you to keep the origional evap of the chiller and build a resevoir around it. have a look around here:
http://www.xtremesystems.org/forums/forumdisplay.php?f=155
and see how others have done it. all it takes is a cooler and some bending. if you want to mess around with phase in the future that's all well and good but i think you should start like that.

 

[MarkS]

instead of throwing you a bunch of links and discouraging you what he should have done is tell you to keep the origional evap of the chiller and build a resevoir around it. have a look around here:
http://www.xtremesystems.org/forums/forumdisplay.php?f=155
and see how others have done it. all it takes is a cooler and some bending. if you want to mess around with phase in the future that's all well and good but i think you should start like that.

That's a good idea. I can do acrylic and PVC fabrication, so creating a container will not be a problem and it will be far cheaper than even a used aquarium chiller.

I'm still going to go ahead with the original project.

I already have the copper coil:

It is just some 3/8" soft copper tubing that was hand wrapped around a length of 3" PVC pipe.

This is what the completed PVC heat exchanger would look like:

The model is kind of rough and not complete. It's missing the connectors for the water lines and other details, but you get the idea. The completed heat exchanger will not use clear PVC (approx. $50 PER FOOT).

 

[XeonStrikeForce]

I'm not discouraging him, I am simply letting him get the fundamental knowledge that will guarantee him success, and allow him to do it safely. Remember a bad mistake can cost you your life, and if he's that new to the hobby he really needs this.

Nice in-line heat exchanger, I'd put the discharge water into the centre and move the other refrigerant line up a bit to open the centre up for the water inlet. I would sujest you use a TXV @ 1/4Ton (Frankly I didn't think txv's that small existed, but allas aperantly they do) or if you expect to realy realy load it use a 1/2Ton TXV (6,000BTU/h)

 

[greenmaji]

I think they sell a TXV that has interchangeable ports going from 1/4-3/4 ton on the same model.. thats the only way Ive seen 1/4 ton TXV's..
One of my concerns about this liquid HX is how cold can PVC withstand not cracking.

 

[XeonStrikeForce]

High quality well insulated will survive up to -40
I personaly have never heard of or seen a 1/4 Ton txv, Smallest I've seen is 1/2 untill browsing ebay and saw one, I was like "WTF? Is that real?" Wish I got it, as it is a closer match to my compressor plant that I'll be using.

 

[MarkS]

One of my concerns about this liquid HX is how cold can PVC withstand not cracking.

Not too much, but I'm not concerned. This type of set up is used for giant aquarium chillers. Water will enter through bulkheads in the side of the PVC tube. The copper coil is the evaporator. The water in the PVC pipe will never get cold enough to crack the PVC.

And before anyone else jumps on XeonStrikeForce... Thank you, XeonStrikeForce! That was not what I wanted to hear, but it is what I needed to hear.

 

[MarkS]

This should clear up some confusion...

 

[XeonStrikeForce]

I still highely recamend you put your water connecters on the main Bulk head.

fyi: that is a very well fabricated coil, just might wish to spread the windings out a bit more so it resembles a non compressed spring.

 

[MarkS]

I still highely recamend you put your water connecters on the main Bulk head.

This is what I'm shooting for, except for the titanium coil and price:

Expensive Titanium Heat Exchanger

VERY Expensive Titanium Heat Exchanger

I could put one connector (called a bulkhead or tank adaptor) on each end. There is not enough room to put two bulkheads on the flange. Exactly what difference would it make to put the bulkheads on the end(s)? It does not look like the flow would change all that much. Your idea is better simply because I would not have to thermo-form the pipe to flatten it so the bulkheads will seat properly. PVC is HIGHLY toxic when heated and I don't like doing that.

I also thought of packing the pipe with tons of copper scouring pads. My thought is that they would increase the surface area of the coil simular to fins on a radiator, but would be better suited for liquids than fins. Coolant could easily flow through the pads and the increase in surface area would be tremendous. Your thoughts?

fyi: that is a very well fabricated coil, just might wish to spread the windings out a bit more so it resembles a non compressed spring.

Already done. The pic I posted was taken about 10 minutes after forming the coil.

 

[XeonStrikeForce]

due to the thermal qualities of water you all ready have plenty, it's now just a question of efficiently utilizing it, with just one one the bulk head firing the water into the middle of the coil so water must go through it will improve things nicely.

 

[Pf.Farnsworth]

Coaxial heat exchangers are trash, use plate.

5000btu unit is not small in this aplication. 1000btu is small.

I wouldnt worry about the pvc, I dought his chiller will see -40C

Yes they have TXV's smaller then 1/2ton. I have one here and 1/2ton. 1/3ton and 1/4ton orifice's for it. Actuallly they are rated in KW of capacity but I did the math for you.

What coolant will you use? Dont use antifreze, its to thick, dont use water will freze, dont use antifreze with water, will get thick when cooled down. Dont use glycol, thick and sticky. Alcohols are good choises.

Don't skimp out on a pump, spend $200 on a nice iwaki MD20 RLZ, make sure to get the RLZ high pressure model, flow means jack in WC because the best you will see in a loop on a PC is 3gpm, but what is important is the pressure - head. Especialy when dealing with chillers which means thick coolant.

What refrigerant will you be using?

Check out xtreme systems for more information.
http://www.xtremesystems.org/forums/forumdisplay.php?f=10

 

[greenmaji]

Pf.. some of us have been reading XS for 6+ months
and some of us (XenonStrikeForce) is a postalotumus over there ROFL

and Crimedog just rules

I think if we were modivated over here someone could get some help

 

[Pf.Farnsworth]

Pf.. some of us have been reading XS for 6+ months
and some of us (XenonStrikeForce) is a postalotumus over there ROFL

and Crimedog just rules

I think if we were modivated over here someone could get some help

Alright, I'll take you up on that. Maybe I shouldnt keep pointing to xtremesystems, but its a habbit. Maybe I just have alot of respect for people there because thats where I started back in the days. And I dont think I would be where I am today if I was interacting with people on any other forum I know of.

XenonStrikeForce, character indeed.

Actually I often see something wrong with what Crimedog says, information accuracy wise. I still maintain that the best place for specialized advice is from people who do it for a living.

 

[XeonStrikeForce]

Insane but consistant!

 

[crimedog]

Actually I often see something wrong with what Crimedog says, information accuracy wise. I still maintain that the best place for specialized advice is from people who do it for a living.

i agree, but here we are. i think too many people get too technical, this isn't an exact science. yes you can slap something together and i'll work I think that's more important that taking thermodynamics classes and reading up on refrigerants.

 

[MarkS]

Actually I often see something wrong with what Crimedog says, information accuracy wise. I still maintain that the best place for specialized advice is from people who do it for a living.

I don't know crimedog, so I cannot comment on his information. However, most of the "industry professionals" that I have met typically are arrogent. Sure, they know a lot, but why should they freely share the knowledge that they paid for? In my experience, the most knowledgable people in any field are the hobbiests. They have to learn hands on with what resources they can find. Most have not been to a school to learn the details of their hobby. These people typically are willing to share their knowledge so that others do not have such a hard time of it. That is what these forums are for. They are not just to show pics of your rigs and give you bragging rights. If people are not willing to help here then this site is basically useless.

i agree, but here we are. i think too many people get too technical, this isn't an exact science. yes you can slap something together and i'll work I think that's more important that taking thermodynamics classes and reading up on refrigerants.

I've always taught myself. I taught myself Pascal programming with a little help from my dad when I was 8. I taught myself BASIC programming by 10 (OK, not real impressive) and was self taught to a college level in C/C++ by 15.

When I started in the aquarium hobby, I learned plumbing, acrylic and general plastic fabrication as well as lighting, heating, cooling, fluid dynamics and chemistry fundamentals with what I found online.

I have never taken a single course on any of these subjects. The programming aspects I learned from books. The rest was learned by asking questions on aquarium boards and learning from the replies of members that have been there before. I can plumb a house to code and I am not a certified and licensed plumber. I can write a complex program and have never been to college. I can build you an aquarium or watercooling reservoir out of acrylic, PVC or glass plate.

Show me the details and any tips and tricks. Point me to websites with detailed info. Answer my questions. I promise you that I will have professional level A/C skills in less than 6 months. However, I cannot do that alone.

Now, can we get this thread back on topic?