Flat plate heat exchanger size?

[AirConditioner]

Originally Posted by AC_Hacker

Well, it's clear that you are too hard-headed to take advice, but hey.. we can still be friends.

I appreciate the advice, but not so much the attitude. I asked you to explain why you can't use threaded connections and you still haven't done that. The truth is flared threaded connections are used in refrigeration. Threaded NPT connections are also used in other places, such as for pressure gauges and access valves. Why do they sell refrigeration gauges and access valves with threads if it is impossible to seal them? For that matter access valves are always covered with a threaded cap to keep them from leaking.

Examples:
http://www.ebay.com/itm/JB-INDUSTRIE...item4d259b8582

http://www.ebay.com/itm/1-4-Flare-Sw...item2a4d68816b

http://www.ebay.com/itm/ALCO-AFA1-4H...item54078443cc

http://www.ebay.com/itm/JOHNSON-CONT.../381006887035?

I appreciate you sharing your experience but yelling "they leak cause I said so" isn't very helpful.

Originally Posted by AC_Hacker

Just remember the key words, "high pressure", "severe temperature cycling" and "relentless vibration"

None of those things disqualify the use of threaded connections. Threaded connections are rated for thousands of PSI. Hydraulic equipment all has threaded connections and works under constant high pressure, heat, and vibration. Sometimes, specialty locking thread sealants are required.

Originally Posted by AC_Hacker

I store mine in empty green camping propane bottles which I have vacuumed to within an inch of their life.

And I assume this has a threaded connection on the top?

Originally Posted by AC_Hacker

But if you're still asking if it's big enough, you didn't look through the Brazed Plate manuals I suggested...

So, if you don't want to do your own research, my friend, you'll just have to guess.

I did look at the link you posted, and none of them give the number of plates, so the information is not really comparable.

[AC_Hacker]

Originally Posted by AirConditioner

And I assume this has a threaded connection on the top?

No threaded connection at all, there is a special valve that uses a spring + the pressure of gas within the cannister to ensure a seal.

There's really no value in bickering...

Build your project. Keep using what methods work and change whatever doesn't work.

Just do it.

-AC

[AirConditioner]

Originally Posted by AC_Hacker

No threaded connection at all, there is a special valve that uses a spring + the pressure of gas within the cannister to ensure a seal.

And what holds that valve to the modified torch you use to release or collect the gas? A threaded connection. And yes, the schrader valve inside a propane tank is threaded in also.

Originally Posted by AC_Hacker

There's really no value in bickering...

Let's be honest, you were giving incorrect advice and then started whining when I pointed it out. I'm not bickering, I'm simply trying to separate facts from BS. From the extensive research I've done on this website, you seem to constantly have an abrasive attitude with everybody.

[AC_Hacker]

Originally Posted by AirConditioner

Let's be honest, you were giving incorrect advice and then started whining when I pointed it out. I'm not bickering, I'm simply trying to separate facts from BS. From the extensive research I've done on this website, you seem to constantly have an abrasive attitude with everybody.

Less talk and more action will prove your point.

-AC

[AirConditioner]

Originally Posted by AC_Hacker

Less talk and more action will prove your point.

-AC

As your grandma used to say, if you don't have anything nice to say, don't say anything at all. I'll update that to say, if you don't have anything useful to add, don't make a post in somebody's thread.

I came here to ask a few questions and TALK with some other like minded folks on this subject. If it is SUCH A BIG DEAL to you to offer any kind of explanation with your advice, then please, don't bother to offer it at all. I don't need it that bad. You aren't enough of an expert to have that kind of attitude.

If you don't want to talk about this stuff and the theories behind WHY, then you shouldn't be here. I don't have any "point" to prove to you or anybody else. I can accomplish this project completely on my own just fine, but why reinvent the wheel?

[BradC]

Originally Posted by AirConditioner

Not trying to offend you or anything, but are you sure you sealed the threads properly? (Maybe there is a special way it needs to be done for such high pressure?) I thought threaded flare connections were pretty standard in A/C stuff? I even found access valves for sale with 1/8" NPT threads. (still can't post a link)

I've been away from the forum for a while, but this thread just appeared in my inbox and I thought some perspective might be useful.

A "threaded flare connection" is a *completely* different animal to a "threaded connection".

Threaded connections are generally used to seal at low pressure, heavy *large* molecules and where leakage is not an issue (air, oil, water). In high pressure and leak prone environments they are *never* used to effect a seal. Where you see 1/8" npt threads for gauges and access valves they are tapered threads and designed to be used with a sealant. The use of the tapered thread and sealant is a *one* shot affair. The act of tightening the fitting deforms the threads which coupled with the sealant effects the seal. Even the valve on your Propane bottle is screwed in with a tapered thread, but there is a very hard to remove adhesive sealant holding it together and filling the gaps.

Removable refrigeration fittings are sealed with flares or gaskets. Flares are simply a soft metal to harder metal compression connection and the thread is there to maintain pressure on the sealing surface, not to participate in the seal. Gaskets should need no explanation.

Those Brazed Plate Heat Exchangers use parallel threads which are not in any form suitable for sealing. They require fittings with gaskets or o-rings to effect the seal. They don't cope well with vibration or thermal cycling and therefore don't see use in refrigeration systems.

Think about this. You have 200g of gas in your system, and your threaded connections leak gas at a tiny but significant rate. It's not very long until your critically charged system is no longer critically charged and things are not behaving as they should.

By the way, disposable tanks are sealed with schrader valves, and the fitting that screws on to them is sealed by a *gasket* and not the thread.

Do it whatever way you want to do it, but you have been given sound advice. As you say, you can accomplish this project completely on your own just fine, you just don't seem to want to listen to those of us that *have* done this many times over. Come back and let us know how it works out for you.

[jeff5may]

Brad hit it on the head. While flare fittings have no seals in them, they are installed with fine threads and generous clamping pressure applied, so the metal tubing is actually deformed to keep a tight seal. Propane bottles and automotive (AN) fittings use polymer seals which crush around the joint to make the leakproof connection. The NPT fittings are not rated for hydraulic high pressure at all.

In systems under a ton of capacity, I have had no good luck with mechanical connections. They tend to rattle everything apart, even sharp bends in tubing. If there are lines to run somewhere else, they get tied to the frame solidly and flared. Any leakage whatsoever will throw a big wrench in efficient operation.

[AirConditioner]

Originally Posted by BradC

A "threaded flare connection" is a *completely* different animal to a "threaded connection".

I am fully aware of this. AC_Hacker is the only one who lumped all threads into one category. Flare connections are what I have been talking about the whole time, and they are quite standard in refrigeration. New tapered (NPT) fittings with the proper sealant torqued to the right spec can also work, but I agree it would be the most likely place for a leak to happen.

Originally Posted by BradC

Those Brazed Plate Heat Exchangers use parallel threads which are not in any form suitable for sealing.

I believe they are also available with flared connections. Or if they just have pipe stubs coming out I would think they could be flared.

Originally Posted by BradC

Do it whatever way you want to do it, but you have been given sound advice.

I was given advice from only one person, AC_Hacker, who lumped all types of threads into one category and could not properly explain why any of them leak. Until you came along nobody offered any explanation of why threads might leak. I am open to sound advice with proper explanations, not internet ranting "cuz I said so".

Originally Posted by jeff5may

The NPT fittings are not rated for hydraulic high pressure at all.

Sorry, but that is totally incorrect. Just google "hydraulic NPT fitting". This is a random result I got:
http://www.grainger.com/product/ENERPAC-Hose-Fitting-46C623?s_pp=false&picUrl=//static.grainger.com/rp/s/is/image/Grainger/46C623_AS01?$smthumb$

3/8" NPT Reusable hydraulic hose fitting.

I have a hot water pressure washer that uses plenty of 3/8" NPT fittings (OEM) that do not leak on a 3000 PSI, 200 degree heat exchanger with constant heat and pressure cycling.

[jeff5may]

You don't have to use the advice given. The whole journey that is engineering is founded on trying to make things work that might not. With enough super loctite and refrigerant, you can get a leak-free fitting or two. At least until something else breaks.

You stated you wanted the easiest, cheapest solution as well as reliable operation. To most of us, it is undisputed that a solid or brazed connection is not extremely difficult to perform. It is much easier over the long term to seal the refrigerant loop as strong as possible once and move on. O-rings and tapered threads can go in different places.

Feel free to discard this free advice. Trial and error, my brother.

[AirConditioner]

Originally Posted by jeff5may

The whole journey that is engineering is founded on trying to make things work that might not.

That is exactly why I came here to talk about heat exchangers, which nobody is really talking about. Posts such as this one go totally against the reason I am here and the reason this board exists:

Originally Posted by AC_Hacker

Less talk and more action will prove your point.

I'm not here to prove anything to anybody and I am here to talk all day long about what works and what doesn't, and more importantly, WHY. As many posts as I've read here AC_Hacker constantly has a bad attitude like that. I also don't need to be treated like a child that knows nothing of the subject just because I happened to ask a question and have not been registered very long on this board.

Originally Posted by jeff5may

You stated you wanted the easiest, cheapest solution as well as reliable operation.

Where in the world did I say that? I stated I was making an experimental system to be filled with propane. A logical person might assume that threaded (flare) connections would make sense on an experimental system that will probably be changed around a few times before the final version. I also said I was filling with propane, so, who really cares if a little leaks out? It's cheap and relatively safe for the environment. It also works at lower pressures, so less stress on the joints.

I would never expect an A/C system built at home from junk and ebay parts would function perfectly and never leak from the very first try, would you?