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Discussion Starter · #1 ·
I'm hoping someone with strong knowledge in refridgerant physics can help me on this one:

this isn't a contracting or job related question, but a personal/experimentation related one.

I want intermitent/sleeping airconditioning on my boat, but before 50 people chime in to get a proper air conditioner, I'll preface this by stating that I'm not spending $1200+ on a unit not to mention the haulout and associated thru-hull hardware for dockside/shore power air, and I'm damn sure not increasing my "house" batteries and associated distribution hardware either.

what I've settled on is making an "evaporator core" out of a $20+/- off the shelf transmission oil cooler, shrouded 12v fans and pump.

My question is, while an open loop using a cooler full of ice and ice water certainly will work, granted using gobs of ice and the mess, I got to pondering about dry ice, it will certainly last alot longer and alot colder.
My thought was to create a closed loop with 2 "cores", (one in a cooler with dry ice properly ventilated of course) and top off/bleed the loop with alcohol or antifreeze.

in theory this should work like a charm, but with this setup, will the "evap core" work , or just ice up???
 

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NICKTECH
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sure it'll work, but the amount of heat removed will depend on the mass/flow rate of the medium (antifreeze). what you got is a ghetto chiller that will work. all ya need is 40 to45 deg solution circulating thru the coil. the mass will depend on the coil size and the flow rate depends on the pump gpm. put a dimmer/speed control on there to regulate the flow. its got to be slow enough to p/u the heat but fast enough to more the right amount of solution. make the cooler coil thats in the co2 larger than the one in the boat. good luck with it, i dig these type of jobs. dont forget to send some pics:thumbup:
 

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You are going to circulate the anti-freeze through the coil, and the dry ice will chill the anti-freeze? In theory, I am with you, but, for the dollar, wouldn't you be better off with the open loop of ice water? How much does the dry ice-cost? How much for the "glycol"? For that matter, wouldn't you rather clean up the water as opposed to a glycol leak?

You could buy the blocks of ice as needed and easily discard the water in the morning. Don't get me wrong, I am on your side with the alternative thinking, so, I say, go for it. I also would like to see some pictures and love to know what are the results.
 

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I don't think it will cool enough to try. It's been 25+ years since I had to think this hard. According to established theory found in the basic book " Modern Heating, Cooling & Refrigeration" as I remember, you would need a ton of ice or equivalent to achieve less than 1 ton of cooling, less is due to natural parasitic losses. Your cabin would need something close to that, certainly more than the couple of hundred pounds you might be able to stuff into a cooler. My book is loaned to an apprentice just starting so I can't reference right now.

Plus I've been enjoying my favorite after hours beverage.

If you really need cooling, accept that you need to bite the bullit & install a commercially available unit & generator. You could probably mount an RV air to air unit like found on campers rather than the thru-hull fittings for a marine unit. You will need a generator as a battery bank of sufficient size would be very heavy & maintenance intensive. You would need shore power and/or generator and a lot of time to recharge. ( IE 18+hrs to charge for 8 hrs cooling )

I don't know the specifics of your boat, but for an example, I have a 32' Motor Home that came with a 15,500 BTUH AC unit & 4KW Onan Generator. I had to add a 2nd AC to keep the cabin under 85 degrees. The 4KW Generator will not run both units. If it were me, I would put a 5.5 KW Generator & 2 Heat Pumps if I had a substantial cabin area to cool.

If you use your boat in chilly weather, the Heat Pump is cheaper to run than a propane furnace.

There isn't a cheap, easy way to AC.

Get a sparky that knows such set ups, don't go cheap as it could cost your life and boat.
 

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Bone Saw, here are some thoughts from an old boater and a marine A/C guy. Buy the A/C unit.

There are quite a few flaws in your system.
A) CO2 is heavier than air. It can sink down into the bilge and build UP causing suffocation. Even placed on deck the 'station wagon effect' could draft the gas into the boat.
B) You can't seal the cooling part of the system as dry ice expands as it converts to a gaseous state. See here youtube dry ice bombs .
C) CO2 converts @ around -110*F. Your anti-freeze would have to meet this requirement should your pump stop.

Send me the info on your boat and I'll help you figure it out. I lived on this boat for a few years in the SoFL sun.

 

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Discussion Starter · #6 · (Edited)

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Discussion Starter · #7 · (Edited)
already have it put together with < $130 in parts, (2) 6v 4" fans in series with a rheostat, electric fuel pump with a Y in and out forming a loop w/ Y valve out for closed loop by pass/flow control, and 2 bleeder valves to top off. I put in 50/50 a freeze/h2o and set the one core in a cooler of ice/water, so far its blowing cold air and and condensing like a mofo. 2morrow i'll test it w/ CO, I hope the condensate dosen't ice up on the core
 

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"There isn't a cheap, easy way to AC."

Here, here! if it was that easy, would the world need Dr. Carrier?!?

What you're proposing, Bone Saw, is great for fun & games, science 101 experments, etc., but how are you going to keep a cooler sealed when you're heeled-over or when Neptune decides to throw a storm @ you?!? Have you ever heard of dry ice dripping on your skin? Not a pretty sight! Go with the genny and store-bought a/c unit, Fleetwood motorhomes spends billions of dolars a year installing these systems for a reason, it's the only thing that works! If dry ice was a way to go, don't you think large companys would be using it? They don't even use that type of system to cool computer chips, except in labratory situations under strict control. What you're trying to do is "cut a fat hog," we all try it (can you say "Ryobi?") then we decide that doing it the correct way is the cheapest way afterall (can you say "DeWalt?")

Sorry, but you need to know- save the headache and don't try to re-invent the wheel, Dr. Carrier has the patents on your better mousetrap already, spend the bucks and do the job right the first time. You do that and I won't try to melt down pop bottles to make lumber to build my hot tub deck- deal? ;-)

C.Ray
 

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NICKTECH
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i kinda did the same thing for the bar in my house. ive got a fridge in the basement that hold the kegs and the beer and soda lines run up to the beer tower and the soda gun. i stuck a coil of copper tubing in the fridge with a cond. pump. the lines were filled with windshield washer fluid because of it's antifreeze properties. the lines ran along with beer and soda lines to the tower to keep the lines and tower cold.
 

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NICKTECH
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do it, do it, do it. dont worry about the nay sayers. utilize a sealed canister as a heat exchanger that is vented outside to hold the co2. as it sublimes and absorbes heat the gas can carry the heat to the outside. submerge the canister into a anti freeze like solution and have the pump move the solution through the coil. fine tune the temp difference of the in and out water so that it's about 10 deg. if possible. there is a Qt formula that can determine the amout of heat remove. to use it you need to know the specifc heat factor of the solution thats used. ex. pure water is 1.0 an msds sheet might have it on there. the formula is:
Q=m x sph x delta T.
Q= btu's
m=weight
sph= specific heat factor
delta T is the difference in temp.
ex. 1gal h2o = 8.33lbs, sph =1.0 and the delta T is 10deg
Q=8.33 x 1.0 x 10 = 83.33 total btus.
use this with the gpm to determine btu/min, btu/sec or btu/hr.
good luck;)
 

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Discussion Starter · #16 · (Edited)
dry ice is readily availably and pretty cheap just about anywhere, we use to pack a 48qt size cooler full of subway sandwiches etc when we went offshore or on the road with 10-15lb block and the cooler contents would keep frozen solid for well over a week
$ for $, pound for pound, degree for degree, mess for mess, dry ice packs a helluva lot more punch than ice
I would rather toss in a 15lb block in my wheeled cooler for the long walk down the dock than lug 2 weighing 50 or 60 lbs +, not to mention all the slopping and sloshing underway, plus the dry ice will easily keep while not in use. a small cooler will easily fit with room to spare in either port or starboard cockpit lazerettes which are completely seperate from down below, a couple of bronze nipples and a 1/2" mushroom will safely plumb through the bulkhead and cooler and vent out the transom, nick you got me thinking about throwing on a low pressure check valve on the vent to maintain slight positive pressure to aid in shelf life while not in use, and as a bonus, will act as a NRV
 

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NICKTECH
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melting ice absorbs about 144 btu/lb while dry ice absord a lot more. plus there is no residual after the dry sublimates, and with a little testing one could determine how much to use vs what kind of preformance is desired. 99% ice with 1% water mixed with salt will change the specific gravity of the water and drop the ices boiling point to a temp below 32 deg. a temp of 20 or less can be acheived as an alternative to dry ice
 

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bu the AC dude you are looking to die with the co2 system. How big is the boat. you can get an inverter, central air that won't asphyxiate you in your sleep and batteries enough to run it. I'm thinking 2 8d batteries overnight. The smallier ones 5K btu will draw less than 5 amps at 120v
If you keep the boat long enough the cost of ice will far outstrip the cost of the system. It will also add value to the boat for the second happiest day of your life.
 

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"(can you say "whatever dude")

btw dummy, dry ice doesnt drip"


What's with the hostility "dude?!?"
btw dummy, I missunderstood this part of your original post, FORGIVE the hell out of ME for being human!!!:
"My question is, while an open loop using a cooler full of ice and ice water certainly will work, granted using gobs of ice and the mess, I got to pondering about dry ice, it will certainly last alot longer and alot colder...loop with alcohol or antifreeze."
I read that as you were going to dilute the CO2 with alcohol, et al and run it thru the pipes from a cooler to a coil below decks to cool the air. Once I saw your pic and re-read your original post, I understood what you were doing better.
I still think you're spinning your wheels, but I'm just a "dumb dude," so don't listen to someone who's been doing this "easy money" job for over 20 years...

Please, and I mean this, no sarcasm here, please do it and let us know how it works, I'm interested. Sounds like you're having success in the short term with a mock-up, but I hesitate to say that it'll work on a rolling boat for very long.

To help (I hope,) I'll let you know that we attempt to get a delta-T of 21 degrees across the evaporator coil in A/C systems. If you go below about 18 degrees or above about 23 degrees delta-T's, either you'll have freezing coils or lack-luster performance.

Hope that helped you- I'm not trying to shun you, I'm just letting you know that $300 for an A/C at Lowes, H/D, Sears, etc. and $500 for a Honda inverter generator that you can use for your computer, battery charging, electric outboard, etc. is a small investment IMHO to not have to "fiddle-fart" with a homade contraption while I'd rather be sailing, fishing or napping... If you looked at Craigslist or at yardsales near you, you could probably get the A/C for $50 and the genny for $200. You could use the genny when at the jobsite, making it a write-off at tax time too- how often do you get to write off something for your boat, eh? :)

C.Ray

Keep us posted on your progress, I for one am interested. Keep in mind that A/C's don't cool the air, they absorb the heat out of the air and reject it where you don't care about the heat being. It's a suptle but important differance to keep in mind... You may be able to use the idea to reverse your home made A/C into a heatpump if it works. I do remember seeing something about saltwater cooling somewhere, I'll see if I can find the book this weekend. Truce?
 

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Discussion Starter · #20 · (Edited)
To help (I hope,) I'll let you know that we attempt to get a delta-T of 21 degrees across the evaporator coil in A/C systems. If you go below about 18 degrees or above about 23 degrees delta-T's, either you'll have freezing coils or lack-luster performance.

Keep us posted on your progress, I for one am interested. Keep in mind that A/C's don't cool the air, they absorb the heat out of the air and reject it where you don't care about the heat being. It's a suptle but important differance to keep in mind... You may be able to use the idea to reverse your home made A/C into a heatpump if it works. I do remember seeing something about saltwater cooling somewhere, I'll see if I can find the book this weekend. Truce?
guess i've been a lil edgy lately, apologies and truce for the hostility:D this is the kind of info I was seeking, which is why I'm not in hvac and refridgeration:laughing:
in all honesty I'll never recoupe those costs when I sell it, its not a hinckly for chrissakes, think more along the lines of a J/24, she's a rocket ship and I'd like to keep her that way, putting 500-600lbs and 4-5$k+ of equipment in her ass end will make her a pig, Just for the occasional 1 or 2 niters on the hook so I can button up from the skeeters without sweating to death, normally a nice breeze will blow right through better than ac, but no wind nights at anchor on the cheasapeke can be a bear with mosquitos, about 3 weeks ago i sailed down to lower hooper Is. (about 89 miles from hailing port of middle river/north of baltimore) usually stop in st michaels or tilghman Is to rest, I pullud into knapps narrows(tilghman is) to catch some z's and wait for incomming tide (around 3am) after a few hours of brutal humidity and miserable sleep, I said screw it, charted/set auto pilot, motored out and slept in the cockpit.

y valve/bypass loop at the pump to regulate flow, and fans on a rheostat, mabey putting a thermometer on the in and out at the coil will help fine tune it
 
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