I'm trying to quickly put together a A/C system for my shop using the creek out back as my main source of cooling. The creek is currently running at about 55 degrees F, it should stay close to that throughout the summer.
My first thought was to modify a regular window type air conditioner so that the condensor coil is cooled by cold water instead of hot air. I've started to wonder though....might it be possible to cool directly with my 55 degree water? That's about the temp of an A/C evaporator.
If I pump the cold water through a radiator in the shop, will very much cold air come out? I've also thought about making some sort of swamp cooler with this water, but I don't want the extra humidity...
Additionally I plan on using the water to sprinkle the roof and concrete walls during the hottest parts of the day. (not unusual for all my huge thermal mass of concrete to hit 85 degrees)
Another problem I have is that the creek is about 50 feet below the shop, so I have a lot of pumping to do, and I want to do that as efficiently as possible. Is it more efficient to pump water in a closed loop from the creek, up the hill, and then back down into the creek? Does the water flowing back down cancel out the head pressure? I would rather use an 'open' system and use the excess water for irrigation but it takes a lot of juice to pump all that water up hill.
if you pump from one level, and have the return to the same level, (closed loop, like a siphon) you will only have the initial filling of the pipe, and from then it's just friction loss.
My friends back east, had a house cooler, run from spring water, that worked as you describe. You will have to craft a "drip tray" to carry the condensate away.
As for spray evaporative cooling, I think that minerals from the water, will get things looking really nasty in a year or 3.
Hi Guys:
Actually, the water-out cancel the the water-in only work to about 30', after that the weight of the water exceed the vapor pressure of the water and "boils" the water, hence the pump on the well with the cylinder on top (as opposed to a deep well pump with the cylinder down in the well and a rod running to it from a handle) will only pump water up from about 30" lower than the surface of the water.
All is not lost, though - 30 feet of the 50 foot total drop/rise is essentially for free, so you will only have to pump againts something like a 20' head, instead of a 50" head.
Also, note that the pump need to be at the source of the water, or not more than about half way up, because it is subject to the same 30' rule that the hand pump on the well is subject to.
You will, however, have to overcome the friction in the whole 100 feet of pipe (50' up and 50' back), so a fair bit of power is still required, but you would have the same problem if you took the water out and pumped it up to only 30 feet and then back 30' because it is the differance in the altitude of the outlet and inlet that generates the "lift" for the water - so 30' up and 30' back still equals no flow!
Hope this did not completely confuse you do to the (non) clarityof the foregoing!
Regardz,
Wayne Stayton
Interesting thought Wayne, this boiling is ..... refrigeration! But frozen means plugged, so there is the rub. I wonder if a thermostatically controlled outlet on the water could be created to keep the water temp above say 35f.
Great information guys, as usual. :) What do you think about using this as a circulator pump?
http://www.harborfreight.com/1-inch-clear-water-pump-1479.html
I plan on installing some 1" PVC from the creek to the shop. I'm also going to run a 3 phase power line down there for lights and other stuff, making my own little camp ground. :D
Think an old chevy truck radiator would do the trick?
I have that same pump. When they say "clean water pump" they mean it. I used it on a 1000 Gal. pond to suck algae off the rocks with a "window screen" filter on the pickup at the suction end. The pump plugged up in a heartbeat. I have used it to transfer "clean water" and have had no problem. Don't know if it will have much flow at the 50' lift you are looking at.
Bob
I had an apartment in DC with chilled water A/C. The unit ran wall to wall near the ceiling, around 12'. The coil had 1/2" copper pipe with fins about 9" square. I've been told they were from supermarket freezer cases. There was a big gutter underneath with a drain for the condensation. I'd guess it was placed near the ceiling where the hottest air was and allowed the cool air to fall into the room. It worked well except for the constant drip.
BioHazard:
I don't think that you will be very happy with the performance of the system as you have described it.
Let's assume you have 50 degree water going in to your radiator. Let's further assume that you have 80 degree air blowing across your radiator. I think that you will be hard pressed to extract more than about 20 degrees of "coolth" out of the water.
Let's further assume that you have something like 200 gallons per minute flowing through the system.
That means that you will have 200 gal * 8 lbs/gal * 20 degrees delta for a total of 53.3 BTU per minute net heat transfer and you'll have 70 degree air coming out of the device.
A real air conditioner uses 35 degree evaporator coils and transfers more like 10,000 BTU / minute with 50 dgree air, max, coming out of the machine.
You'll wind up with a system that just vaguley makes you feel slightly cool IF you stand right in front of it - ten feet away, you won't even know that it is there, except for the noise of the fan running! <grin> Sort of the "peeing-on-a-forest-fire" concept!
YMMV, but I don't really think that you will get much bang for your buck with this set up, sorry!
Regardz,
Wayne Stayton
Hmmm....I hate it when math gets in the way. ::) I have read a bit about cold water hydronic cooling systems, but they normally use water colder than 55F. I think I might be better off going with the water cooled air conditioner, certainly 55 degree water will work a lot better on the condenser than 80-90 degree air!
I'm pretty sold on the slow speed fan and a water bottle sprayer approach. Why cool the entire room and surfaces down when we really just want to cool the body. I wonder if you sat on a sterling engine if that could power the fan?
How about just running the water line into the cushions of your favorite chair?
Casey
The problem is I'm always running around like a chicken with my head cut off at the shop. ;D I'm very intolerant to heat/humidity...anything over 65 and I start sweating like Shaq. ::) Last year, without A/C I had to take maybe 4-5 showers during my work day.
Although that is an interesting idea....a water cooled chair. Hmmmmm..........
Bio all good info so far!
Your big issue is humidity, not going to remove much at 55.
If your in a arid part of the country it will do a better job.
Kind of like going in to a cool basement, feels good when you first go in, but then you feel clamy.
Ok...how about this for an example:
If I take a 5000 BTU window air conditioner that uses 500 watts while being air cooled on a hot day...
And I replace that hot air with cold water...what's going to happen exactly? Will the A/C make more than 5000 BTU? Will it use less than 500 watts?
It has to be "more efficient" but then again I can't understand how that would make it use less power?
BioHazard:
I THINK (ALWAYS dangerous!! <grin>) that a conventional airconditioner cycle the compressor on and off to maintain a certain pressure in the highpressure vapor side of the unit, which is where the condensor is.
If you add on a water cooled condensor, you are going to lower the pressur ine the vapor side quicker than the air-cooled condensor will di it, so the compressor will come back on sooner.
I think that the net effect will be that ou increase the capacity of the unit, without much change to the total efficiency of the unit. So, you might have 30% more capacity with the compressor running 25% more than an air cooled unit - just number that I sort of picked out of the air, but I would THINK they would be representative of what happens - but I think that you will use more electricity with an increased output, for a net of slightly better efficiency.
Worth exactly what you paid for it!
Regardz,
Wayne Stayton
Well, today I took apart one of my air conditioners and pulled the condenser away to put it in a bucket of water. Very happy with the results! The air coming out was colder than when it was air cooled. I was surprised how quickly the water warmed up, now I'm going to have to think of some sort of hot water pre-heater with that. ::) I was only using hose water, which is about 10 degrees warmer than the creek.
End result, I can remove the fan that normally cools the A/C, saving some watts, and then cool a bigger space with a smaller unit. And I won't have to cut a hole in the wall to put the air conditioner in! ;D
How do they actually calculate how many BTU is actually coming out of the front of an air conditioner?
Quote from: BioHazard on June 18, 2011, 11:27:38 PM
.....How do they actually calculate how many BTU is actually coming out of the front of an air conditioner?
I don't know, but you could measure your bucket temp, run the unit for 5 min, then remeasure, and subtract the watts added by the motor heat, and that's how much heat you moved.
At some point, the freon can't move more heat, regardless of the size of the creek you stick the condenser in .
When you note the conditioned air is colder that will be setting you up for problems if you get ice on the evaporator - the additional back-end cooling the water gives will need extracting on the front end by increasing air volume. Beware changing the layout since the condenser fan also cools the compressor that is hopefully internally overtemperature protected with a self resetting temp switch. The fans usually share a motor so removing the rear one may increase the front-end air stirring but not by much.
Interesting...I thought the compressor was mainly cooled by the refrigerant it's pumping? Maybe I could wrap it in copper tubing and water cool it....
Good point about needing more air flow if the evap is colder, I've experienced that freezing over many times in the winter when I use this air conditioner as a dehumidifier. :)
Some more questions about pumping head losses:
If I have a submersible pump let's say 10 feet deep, does the "head" start at the water level, 10 feet above the pump, or does it start all the way down at the pump?
Also, using an inline sort of pump, does it make any difference whether it is pulling or pushing water? In other words, if I had 10 feet of suction, and 40 foot of head, would that be any different than zero suction and 50 feet of head?
Head height is the difference between static water at start and static water at end. Example, think about a drilled well: the "head" is measured from the static water level in the well casing, not from how deep you set the pump in the water. Therefore, you would measure the difference in water level at your creek to your outflow. Yes, you have to include the suction of water from below in you calcs of head height. Weight of water is still weight of water for the pump to overcome, whether it is pulling or pushing. The real problems are that you can only suck water from so far down before you get cavitation/vacuum from the weight of the water, and that pumps aren't built to suck water from more than a few feet below. And remember, the pump is running dry if you are sucking for a while before building up enough suction so water flows through it. Keep the pump as low as possible.
If you're dealing w/ a pressurized closed loop filled w/ water, all you have to deal with is the resistance of the pipe per foot x length of the loop, as someone mentioned earlier.
Alright, I got some more testing done tonight. I have two identical 5200 BTU window air conditioners. One of them has the condenser in a bucket as mentioned above and the other is unmodified.
Plugged them both in side by side with a kill-a-watt. The air cooled A/C was burning about 480 watts, while the water cooled was closer to 390 watts. (with the fan still attached) The colder the water on the "hot" side, the less electricity it used.
I don't understand how that works. Can somebody explain this? I would think the motor should be pumping away at the same rate it always does?
It also easily heats 20+ gallons of water to over 100 degrees in a few minutes. I see an air conditioner powered shower in my future.... ;D
Looks like my creek flow has dropped significantly since the rain stopped, I hope it doesn't stop flowing all together. Tonight I was able to pump the entire creek dry with a 1/2hp sump pump....
Quote from: BioHazard on June 21, 2011, 02:16:19 AM
I don't understand how that works. Can somebody explain this? I would think the motor should be pumping away at the same rate it always does?
Bio
I am no expert but I will take a shot at explaining it.
If you would have a way of attaching a high side pressure gauge to both units I think the high side pressure on the water cooled unit will be much lower and that is why the compressor runs at lower amp draw.
If the water was allowed to get very hot the amp load would come up and match the air cooled unit.
Water holds a lot of BTU's and is very efficient at absorbing it. Wish I could remember all those scientific terms I learned in school. :( :(
Interesting test, now can you get the fan that moves the air through the condenser off the shaft and retest?
Billswan
Did you test both units with the kill a watt meter before running the test to see if the draw was the same on both?
Did the output temp on the water cooled unit get colder?
QuoteWater holds a lot of BTU's and is very efficient at absorbing it. Wish I could remember all those scientific terms I learned in school.
Hey, finally something that relates to my training (I have a Biophysics major and Chemisty minor): I think you're looking for the term "specific heat" and "heat capacity". :) :)
- Specific heat of air: 1.01 (J/G degree C)
- Specific heat of water: 4.179 (J/G degree C)
Quote from: billswan on June 21, 2011, 06:26:54 AM
Interesting test, now can you get the fan that moves the air through the condenser off the shaft and retest?
Yeah, I'll try to do that tonight. Interestingly the fan motor is labeled "20 watts" but when the A/C is on fan only mode it draws 45w.
Quote from: Carlb on June 21, 2011, 07:27:38 AM
Did you test both units with the kill a watt meter before running the test to see if the draw was the same on both?
Did the output temp on the water cooled unit get colder?
I didn't test the power consumption before modifying, I wish I had. They are identical units though, both with about 3-4 years of heavy use on them.
The evaporator was colder on the water cooled machine, I can't remember the numbers now I'll try and post them later.
Quote from: mbryner on June 21, 2011, 11:12:26 AM
QuoteWater holds a lot of BTU's and is very efficient at absorbing it. Wish I could remember all those scientific terms I learned in school.
Hey, finally something that relates to my training (I have a Biophysics major and Chemisty minor): I think you're looking for the term "specific heat" and "heat capacity". :) :)
- Specific heat of air: 1.01 (J/G degree C)
- Specific heat of water: 4.179 (J/G degree C)
Also latent heat!
The added heat added to or released as something goes from solid to liquid, liquid to gas or back again .
Sublimation from liquid to a gas.
http://en.wikipedia.org/wiki/Latent_heat
Alright, working with this thing is getting a bit akward with the condensor haning out the back. If I move it anymore I'm afraid I'll kink the lines.
I can either surround the condensor with some sort of water jacket(??) or, I was thinking about just removing the condensor and replacing it with a coil of copper tubing. Would that work, just a simple coil of 1/4" tubing dunked in water? Obviously I'd have to recharge the unit if I did that...
If you are going to remove the condenser to add the copper tubing, Why not just use the copper tubing to re-locate the existing condenser?
Quote from: Carlb on June 26, 2011, 05:24:40 AM
If you are going to remove the condenser to add the copper tubing, Why not just use the copper tubing to re-locate the existing condenser?
I could, although it would be a lot easier to build a heat exchanger if the condenser is nothing more than a coil of tubing. The original one is made for air, and I've already bent a bunch of fins...
Grain of salt warning:
If you leave the coil as is and remove that fan you could just spill water over it and use a metal gutter to route the hot waste water anywhere, even down a zig zag of other gutters into a pool. Reuse the same water with a small pump. Big volume of reserve water and you're set.
The coil should work just fine for a long time in that sort of mode, made for air or not. The heat exchange is working now with water, why mess with that end of it?
R
Have you seen the $4.99 fin straightener?
http://www.harborfreight.com/radiator-fin-straightener-37892.html
Quote from: RogerAS on June 26, 2011, 10:32:22 AM
Grain of salt warning:
If you leave the coil as is and remove that fan you could just spill water over it and use a metal gutter to route the hot waste water anywhere, even down a zig zag of other gutters into a pool. Reuse the same water with a small pump. Big volume of reserve water and you're set.
The coil should work just fine for a long time in that sort of mode, made for air or not. The heat exchange is working now with water, why mess with that end of it?
R
I'm hoping in the end it will be sort of a "pressurized" system, water inlet, water oulet and a couple of garden hoses...that way I can lower the head pressure. I could do a recirculating system but the water temp seems to make a big difference on power consumption. The difference between 65 and 85 degree water is huge. It should be even better once I get the colder 55 degree creek water flowing. I haven't had a lot of time to work on it though....
Quote from: Horsepoor on June 26, 2011, 04:00:10 PM
Have you seen the $4.99 fin straightener?
http://www.harborfreight.com/radiator-fin-straightener-37892.html
LOL, yeah, I have one of those, and I need to use it. ;D
Interesting thread, I always like thinking of ways to make air con units more efficient :)
I guess as one of the other guys mentioned before if the system becomes too efficient ie the condensor gets too cold the evaporator will also get too cold and if the fan isn't strong enough to blow enough heat then that is when it will freeze up... in summer if the shed is warm enough it probably won't happen though...
How big is the workshop you are trying to heat?
I am in the process of building my own workshop soon, It will just be a colorbond rather than brick and I will put insulation on the inner walls and install a nice large split system air conditioner to keep things cool, we have a 7kW (I think that's 24,000 BTU?) one inside which chills our house nicely so I am thinking if I can run that sucker with my new lister engine on WVO then I get free air con!
I have seen a few water-water heat exchangers on ebay, you could connect one of those in-line with the aircon condensor so that you have your normal radiator and also water cooling when you want. You would need to have the system re-gassed and it might get a bit messy, it might just be easier to obtain a larger capacity air conditioner.. the inverter type split systems can provide 2.5kw cooling power for a similar wattage input around 600~, of course it depends on how often the system is running and insulation etc etc