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wrote:

...I'm trying to come up with a way to make an AC that works
without a window... 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.

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.

You might need the outdoor part if you had your own water heater and
the tank were hot and you needed more AC, but you are unlikely to need
one if you push the hot water back into the hot water pipe that enters
your apartment and the apartment tank is bigger and more people use its
hot water. Do you pay your own hot water bill?

...lugging around a swimming pool of tubing wouldn't allow for
portability, but I address an alternative later in the post.

You could make a flat spiral of 400' of 1/2" HDPE pipe in a fairly
lightweight 6 foot diameter disk.

Additionally, for temporary use, they could just plug into any cold
water supply and drain.

And miss the opportunity to heat water with 1/3 the usual energy... You
might open a solenoid valve to drain some hot water from the top of the
tank when/if the bottom gets to 110 F, in order to avoid the pipe and
pool on the balcony. You'd still have the 8' PVC pipe containing some
copper pipes.

What about using a second (smaller) compressor for the water circuit?

More money and energy and complexity.

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.

Evaporating water from the hot coils seems to invite mineral deposition
and corrosion. It also requires lots of surface. If you didn't mind
wasting energy, you might build an unpressurized plastic film
plate-type heat exchanger into the aquarium surrounding the hot fins.
If 5K Btu/h flows through A ft^2 of film with a 30A Btu/h-F conductance
and a 5 F temp diff, A = 5K/(5x30) = 33 ft^2, eg 16 1'x2' films spaced
1/4" apart. This would take the place of the 8' PVC pipe and the pipe
on the balcony. The "pool" might be a 6'x6' piece of plastic film
draped over 2 2x4s in a balcony corner, with a 10 W fountain pump.

Nick