Hi,
I live in apartment building which has an unlimited (to me) supply of cold water. As an alternative to a conventional air conditioner, I was wondering if it would be practical to run the water through a radiator
Thanks
Some additional comments:
My goal is partly to save money on electricity, but mostly I just want something that is moderately efficient and doesn't require a wall mount.
Here are the options that I see.
Wall mount air conditioner
- Cannot use
- cutting a hole in wall is out of the question
Tap water heat exchanger
- No wall mount required
- No electricity used
- Will it provide enough cooling? Could hook to bath tub
Portable air conditioner
- No wall mount required
- Have a 10,000 BTU unit
- Almost useless for cooling even a small room
- HORRIBLE efficiency, worse than even cheap window units
"Split" air conditioners
- No wall mount required, but small hole is required for tube
- Have a porch, could place condenser outside
- Good efficiency
- A bit expensive and large for an apartment
Outdoor water chiller
- No wall mount required, but small hole is required for tube
- Can obtain used drinking fountain almost free
- Simpler install, water tubing can be flexible
- Sounds like best solution if efficiency is moderately good
- Can a drinking fountain handle the job without the motor burning out? The apartment is fairly small.
sp snipped-for-privacy@yahoo.com wrote re air conditioning with a
You _might_ cover the ceiling with lots of cold water pipes :-) Warming
1000 pounds of water per hour (about 2 gpm) 10 F would provide 10K Btu/h of cooling. If the air-water temp diff is 10 F, with a 1.5 Btu/h-F-ft^2 slow-moving airfilm conductance, you'd need about 10K/(10x1.5) = 667 ft^2 of pipe, eg 67 4"x10' pipes, but that might not dehumidify well, even if some condensation occurs, and it would waste a lot of water.If you really wanted to do this, you might make a tank around the hot fins of a cheap window AC and fill it with oil (to avoid corrosion) and pump lots of 110 F oil through a heat exchanger to warm 0.4 gpm of 60 F water to about 110 F. Z = 0 and E = 1-e^(-NTU) = 0.9 makes NTU = 2.3 =
60A/200, so A = 6.7 ft^2, eg a 3"x10' copper pipe inside a 4"x10' PVC pipe. You might pump the still-pressurized hot water back into the hot water pipe in your apartment, where it might eventually push some cold water out of the bottom of the water heater for the apartment building.Nick
Moved to a different forum. Thanks to Nick and Stretch for the replies.
Hmm, I didn't actually move that post to this forum; maybe it was moved here by a moderator of another forum (sci.engr.hvac or alt.hvac).
I wasn't actually considering using all that piping; Nick was merely trying to show me that I would need an enormous radiator to make an effective water-based cooling system.
Since I'm here, I might as well post the original message. It follows:
I live in an apartment building which does not have a provision for a regular window air conditioner. I do have a portable 10,000 BTU unit, but it performs very poorly and it is expensive to run. I have a porch, and I want to put a split-system air conditioner on it.
I am an electrical engineer, and I would like to convert an existing non-split unit rather than purchasing a split air conditioner. Even if it doesn't save me money, I am set on trying to do it. I'm sure a lot of people will say that it's not worth it, but if nothing else, I will come out learning a lot about how air conditioning systems work.
My question is about the fluid which circulates between the compressor and the indoor (air-liquid) heat exchanger. What are the advantages and disadvantages of the following:
- Running the refrigerant from the outdoor compressor all the way to the indoor heat exchanger
- Having two closed loops: one localized loop for the refridgerant, which stays outside. then a second loop which is cooled by the 1st loop, and then goes inside to the heat exchanger.
And if I do the 2nd option, what would be a good liquid to use in the tubing? Theoretically almost anything with a large specific heat
*could* work, but there may be practical advantages/disadvantages to certain liquids (freezing and boiling points, etc).If I go with the 2nd method, would I be better off taking apart a large window AC unit, or taking apart a water chiller (from an old water fountain)? The water chiller would already have 2 loops, which makes things simpler, but it is probably not meant for such heavy use. With a window AC unit, I would have to build a liquid-to-liquid heat exchanger, such as two radiators immersed in an insulated box filled with oil.
Thanks
Cover you ceiling with pipes how pretty, and it will drip water everywhere .
Or 5 3/4" x 10' copper pipes connected with Ts and street elbows. Heating water with 1/3 the usual energy could be interesting, compared to a $1K heat-pump water heater. Put an AC on a platform in the basement with a fountain pump and a vertical PVC pipe near a tank water heater with a thermosyponing fresh water loop, and air condition the house with a circulation fan to the (dry) basement.
Wal-Mart sells Haier 5K Btu/h window ACs with a 9.7 COP for $98. I took one apart today and found it wouldn't be hard to add a tank around the hot fins without any recharging or replumbing.
Nick
That would be a good solution, because no connection would have to be made to the outside, except if the hot water wasn't used frequently. And if that happened, some type of solenoid valve could be actuated to release some of the hot water outdoors and cycle in some cold water to cool the AC.
At my apartment, unfortunately, I don't have access to the water heater. Something to keep in mind when buying a house, I suppose.
I think I'm going to try cutting the piping in a conventional window AC and adding longer refrigerant lines so that the hot fins are outside, and the evaporator is inside. The compressor could technically be on either side, but I might as well put it outside if I can. There would also have to be a way to drain out the water which condenses inside -- shouldn't be too difficult.
"Nick Pine specializes in astral-physics - physics that only work in another plane of reality. Take his nonsense accordingly. "
Placing myself with a crowd that you label in that manner is hardly trying to "impress everyone". And I'm not about to get my PhD, I don't know why you assumed that. And as far as attitude, I've been trying to maintain composure and stick to the subject despire your incessant flaming from the get-go. You seem to have made about twelve thousand posts since google started their archive. After briefly scrolling through the list, I see that they are almost all pointless banter from someone who has nothing better to do.
That's good.
Nick
Back to the actual subject, if anyone can still bear to follow this thread...
I think the only concern would be getting the pressure right in the indoor part of the tubing. You want to make sure the refrigerant boils and turns to a vapor in the indoor part, and you can set the temperature at which this happens by the pressure in the tubing. If the splicing of the tubing affected the pressure, some adjustable valves might be able to compensate.
Hmm, shouldn't have used google-groups to post. I thought I was posting just to alt.home.repair, but I guess it went to both groups.
Yup, now twice as many people world wide know just how clueless you really are.
Dude,
You are going to spend thousands of dollars to save a few tens of dollars! If you open the refrigerand circuit without EPA certification the penalty is 5 years jail and $27,500 fine! In addition if you don't have the certification you won't be able to buy the proper refrigerant for this application. This is NOT the stuff you can buy at Wal-Mart. There are over 100 different refrigerants, only one will work in the window unit. Has to do with compression ratios, specific heat, operating pressures, metering oriface sizes and LOTS of other stuff. Stick to electricity.
On the other hand, if you start working on this project, it should keep you out of other kinds of trouble for a LONG time! :-) That is if this thing doesn't blow up in your face and kill you. I have i brother and a sister in law who are engineers and they don't mess with stuff they don't understand. By the way, have you ever heard of the darwin awards? Don't get your name on their lists.
Stretch
Funny thing is, he can buy what hes wanting...spend under 2 grand, and save alot of effort attempting to re-invent the wheel.
I read his posts..and all I can do is say that I actually agree with Paul on this one.. The guy has no clue what to call the parts hes working with, but...hes gonna make a window unit work again after he opens it.. and if you say..500 mC, hes gonna be like....wha? You tell him, and then its..but the compressor in the unit will do that right? No...dont tell this guy about the Dawin awards....if he wins this year, we can all say we know someone..err...knew someone thats famous.
If he did, what would he do if the water heater tank were full of 110 F water and he still needed AC?
I like cats too. I have four: Roo (blind), Creamsickle (stupid), Inviso (feral), and Kidders (evil feline of doom.)
Nick
He might pump 110 F pressurized water through a $40 400' flat spiral of
1/2" plastic pipe on the bottom of a 6' plastic swimming pool on the balcony. A smaller pool would do, if the AC only works part-time.Where I live, the average outdoor humidity ratio w = 0.0133 with water vapor pressure Pa = 29.921/(0.62198/w+1) = 0.626 "Hg on an average day in July, and air near 110 F water has a saturated vapor pressure Pw = e^(17.863-9621/(110+460)) = 2.68 "Hg, so (using an ASHRAE swimming pool formula) we can lose 5K Btu/h = 100A(Pw-Pa) with A = 24 ft^2 by evaporating about 5/8 gallons per hour of water.
The hot water circ pump (Grainger's $120 4PC86 looks good) would also improve the thermosyphon loop.
Nick
cat boi, get a job , get a woman, get a life, until then , just f*ck off and die
cat boi, u started no group, get a job, get a woman, get a life, otherwise f*ck off and die
Hi,
I took this thread off of "sci.engr.heat-vent-ac" and "alt.hvac"; hopefully it will calm down a bit. It seems to be added to "alt.energy.homepower", so I'll continue it there as well. If anyone is just starting on this thread, I'm trying to come up with a way to make an AC that works without a window, yet works better than those portable units (I already own one, and I don't like it). There are "split" AC systems pre-made, but I'm starting to think they aren't appropriate for an apartment, even if money was not an issue. Upon moving out, the refrigerant circuit would have to be dismantled. I'm not sure if store-bought units provide valves to contain the refrigerant when doing this; otherwise the refrigerant would have to be completely drained and refilled every time. Additionally, they're fairly expensive, and though building one is simple in principle, I might instead pursue another route, which Nick just suggested.
Warning: This is a rather long post.
---------------
In reply to Nick's previous message:
That would actually be like a cross between two types of AC's: split and portable units. It would be just like the portable unit in that the compressor and the entire refrigerant circuit stays inside. Except instead of using a fan and an air duct to remove the heat outdoors, it would use a water circuit. And instead of discharging the exhaust right out a window, like a portable unit, it would have a "second half" outdoors, like a split unit. The nice thing about such a unit would be that the exhaust "duct" could just be two thin, flexible hoses. If such a unit was commercially produced (or should I say producable?), it could have many applications. There are many people who work in temporary locations, and use portable AC's. But a lot of these people just point the AC at their immediate work area, and let the hot air blast out the back. Usually this is because it's too inconvenient or impractical to duct the hot air through their workplace. With smaller water hoses, this wouldn't be as much of a problem. Don't get me wrong, lugging around a swimming pool of tubing wouldn't allow for portability, but I address an alternative later in the post. Additionally, for temporary use, they could just plug into any cold water supply and drain.
In order to get my store-bought portable unit to operate acceptably, I need to use an enormous hose (bigger than the manufacturer supplied), or else it will overheat and automatically shut off. Even in a very small room, with the exhuast only having to go a foot or two. The exhaust duct is ugly, and it is extremely hot. If the duct was more than 10 feet or so, I bet the net result of using the portable AC would be to heat the room, due to the heat radiating from the duct.
To add to Nick's idea:
What about using a second (smaller) compressor for the water circuit? If the water was allowed to evaporate as it hit the hot coils, its cooling ability would be much more efficient than if it stayed liquid and just absorbed a small amount of heat as it passed. The compressor would then pressurize the steam, lowering its boiling point, and it would cool through the tubing Nick just mentioned, where it would condense. There could then be a resevoir of water, to ensure that the water in the next part of the tubing was almost entirely in the liquid phase. Then it would go through some small flexible tubing to the indoors, and cools the coils again. The pressure in various stages of the tubing could be regulated somewhat by adjustable valves.
For me, a 6 foot pile of piping isn't that bad in the first place; I never use my porch. But it would be nice to reduce that size, if possible.
Some people might argue that having two compressors would reduce the efficiency of the total system by a factor of about 1/2 purely because of having double the number of compressors. However, where the water compressor is doing "extra" work, the regular AC doesn't have to work as hard, because its hot coils would be cooler. There would still energy losses due to more moving parts, the viscocity of the water, etc... The net efficiency would surely go down, and maybe it would go to less than 1/2 its original value. It's just a question of whether it goes to an acceptable level. People who buy portable units expect to pay more for the units, and paying more for electricity is expected too. The units are usually only bought because the user is unwilling to go without AC, but the choice of AC units is limited by the environment. Generally the application is temporary, and my case is no exception (I won't live here very long). I have to guess that my store-bought portable AC has an efficiency of 1/4 of even a cheap window unit. A similar efficiency would be fine.
Also, I *do realize* a purely water-based AC would NOT work well (alone). I am definitely not suggesting anything like that. Here, the water is just transferring heat from a very hot coil to the less hot outdoor air. The water would do that naturally, without a compressor involved. It is NOT causing a SEPERATION of heat between two resevoirs; ie: adding heat to the hotter side. And I realize that the water would probably never been cooler than either the indoor or outdoor air. It would only be cooler than the hot coils of the AC, and that's all that matters. The phase changes between liquid and vapor would simply be to absorb and release lots of energy quickly.
If such a unit was made commercially, the only benefit over a standard portable AC would be having a thinner, flexible exhaust circuit. That alone would open up possibilities. But for me, it would also mean that I wouldn't have to cut into any refrigerant circuits. Which means not having to worry about properly containing the refrigerant, getting a vacuum pump, soldering the joints, putting more refrigerant back in without letting in air/moisture, getting the pressure right, the list goes on...
----------------------
Now, we had some arguements in the other newsgroup about making versus buying, "reinventing the wheel", etc. Personally, I think it's more like "building a wheel" to a certain specification. There will always be some people who try to do things that they are destined to fail at, and others who run away from anything challenging. Either extereme isn't desirable. As far as that topic goes, I think it's best to just leave it at that. But just for the record, if someone made a portable AC unit approximately 20,000 BTU which had the design I described above (with flexible, insulated water tubing), I would probably buy instead of build. But that's besides the point, because I've never seen such a thing.
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