Running cold water through a AC evaporator coil

[whatusernamesareleft]

I was looking at an ac evaporater coil and running water through it.  How well would this idea work?

[Bruce S]

For what?

[bob g]

given a hot enough day, sufficient water volume and cold enough
you can certainly cool things down with such a system, however
you have lots of variables to work out.

how much space?
how well is it insulated?
how hot is it in the space?
how much water do you have to work with?
how cold is it?

answer those questions (and maybe a couple others) and then you can
pick a core, pump, fan and all the other stuff to make it all work.

usually doesn't work well unless you have a free flowing spring with lots of water to use and dump back into the outflow of the spring.

well water probably isn't going to work well.

another possibility if you live in a very dry area,  you can use a cooling tower and a large storage tank, use the tower at night to chill the water and use it the next day to  provide cooling.  figure on a very large storage tank and/or a small space that needs cooled/

fwiw
bob g

[Basil]

It works.
I did a test with an old window unit. 90 deg day.
Coil copper pipe in the unit is about 3/8 inch.
I used the cooling coil of course. Closed one end off enough
to let the complete coil get cool while the fan was running.
Water temp at the facet was 56 degs. But the water had to run
through a 50 ft hose pipe laying on the hot ground. It still dropped
the temp from 90 to 70 deg's. It felt dare good. And this was out in the sun.
It does not take as much water to do this as you would think.
A small spring is all it would take. Well water is different temps
at different place's. Water here is around 56 deg's or a litter higher.

[jlt]

I have used a couple of car condensers hooked up in series . the cold water going into the one closest to the fan. and I used a electric radiator fan from an old Subaru

  My water comes from a gravity flow spring at about 55 degrees. I use the exhaust water on my lawn

It will keep the house at 68 degrees when It is 90 out side.

I would  .start it running in the morning when I left for work.If I let the house get hot before tuning the unit on It only did a fair job.

  It would only use about 2 gallons per minute . I had the unit mounted in a basement window
Which helped bring cooler air from the basement.

A lot of friends would come by and say they thought I had central air conditioning . 

[bob g]

lets do some math, shall we

lets make a few assumptions just for the purpose of illustration and discussion.

for our example lets use the following parameters

ambient temperature 100 degree F
water source temperature 50 degree F

so we have 50 degree's of differential to work with...

lets assume a perfect heat exchanger, that can remove all the available btu's, or in other words make perfect use of the 50 degree differential.

now lets use water weight as 8lbs per gallon

lets assume we have a source of water that free flows 5 gallon per minute, or 300 gallon per hour

the definition of a btu is the amount of heat it takes to raise one pound of water one degree F.

so if we have 300 gallons of water, and it weighs 8lb/gallon, they we have 2400 lbs of water.

using the btu formula, therefore 2400lbs of water (per hour) * 50 degree's differential = 120kbtu's or about 5 tons of cooling, however

we can't get a perfect exchanger, and we aren't likely to want to get down to the base temp of the supply water for space cooling, so lets assume we want to get down to 70 degree F. we would then have a need for about 2400lbs * 30 degree's = 72kbtu's

my bet is the exchanger is likely not going to exceed 50%, so we might end up with 36kbtu's or 3 tons of cooling capability.

so i suppose it is possible to get some good cooling if you have sufficient supply of cold water, enough of a heat exchanger to get as much of the coolth possible from that water (in reality really the ability to dump that amount of heat from the house to the water source), and have everything else worked out.

then there is the deal with humidity and its effect on the systems ability to cool, what to do with condensation water if in a humid area, and a few other issues.

to start with one needs a reasonable size free flowing spring to tap the cold water from, and be able to reintroduce the waste water back to the stream. this is something they frown on with wells, for obvious reasons.

if someone would be so kind as to recheck my math, and make corrections if necessary would be appreciated.

thanks
bob g

[thingamajigger]

@All
We used to use this system way back when me and Dad were kids and I installed a similar system in the first house I bought. The AC evaporator coil is way too small and I used a 5' x 14" fin exchanger which came out of hot water system. I cut into the return air duct and set the coil at an angle vertically then added spacers on the side to close it in. I also do this with my forced air furnace, I use two 25" x 20" filters one on top of the other vertically for twice the suface area because I'm too lazy to clean the washable filters every 3 months. I used a seperate thermostat to control a solenoid valve which controlled the cooling water then the warm water went to a seperate spigot outside, through a garden hose --- to the garden.
It worked like a damn however as someone mentioned if you try to cool a house that is already hot then it takes forever. The best system I had skipped the furnace all together and used a seperate fan and fin exchanger. It sucked air into the house through a seperate duct and discharged it into the basement then I would leave a window open at the highest point in the house. Hot air rises so all the hot air leaves the house through the top window at the highest point as all the cool air enters from the lowest point, I basically fill my house with cool air from the bottom up.

I should note for me trying to mix cool and warm air was a losing proposition and the cooling seemed way more effective when I pulled fresh cool air in as I pushed all the hot air out.

Regards
Thing