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
+ fan, and then back down the drain. The water is colder than I would
ever want the room to be. Any thoughts?
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
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 firstname.lastname@example.org 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.
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
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.
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.
What is with the anti-college attitude? I only brought up my Physics
background after you said:
"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.
Back to the actual subject, if anyone can still bear to follow this
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.
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.
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
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
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.
sp email@example.com wrote:
[Whilst considering air conditioning while heating water for showers
with 1/3 the usual energy by disconnecting the condenser fan and making
an unpressurized tank around the hot fins of a $98 Haier 5K Btu/h 9.7
SEER Chinese-built AC (with remote :-) from Wal-Mart and pumping
antifreeze up through a vertical 4"x8' PVC pipe with a 10 W fountain
pump, said pipe containing 5 1/2" copper pipes connected with Ts and
street elbows to make a pressurized thermosyphon loop through a tank
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.
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