Seawater air conditioning

[J Clark H356]

http://www.marinaire.com/Products-s/...FcMbgQodAi4HCw

Look at the MarineAire 16,000 BTU model. Cost is $1,595 US.


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[Lodesman]

Originally Posted by Ironman162

Please don't take what I said in the original posting as gospel I know very little about the subject hence the discusdion. It looked like a radiator of sorts to me with my limited understanding.
All I know is that the seawater is pumped through a system of pipes and back out again as shown on the diagram.

There is overwhelming evidence that it does work well in Australia and elsewhere but might be climate specific of that Im not sure.

Do you understand how a refrigerator works? Marine A/C does the same things - it compresses refrigerant; this make it hot (ideal gas law); the hot refrigerant runs through a heat exchanger that is cooled by seawater - the hot seawater is pumped overboard, and slightly cooler refrigerant is decompressed (making it that much colder than it started) - this is run through a radiator, where a fan blows ambient air over its fins, thus cooling it.

[Hard Rock Candy]

When you blow cool air over your sweaty body the evaporation of the moisture on you skin is what cools you down. So automatic air conditioner completely natural. Mac

[Reefmagnet]

Oh wow. I just cottoned on to the concept. I was thinking that the seawater was for cooling a condenser on a regular refrigerated cooling system. do-uh!

I think such a system would struggle to be useful. Firstly, sea water temperatures even in Sydney reach the low to mid 20's at the height of summer which leaves little differential for effective cooling. Secondly at night, when most people would "appreciate" air conditioning, it is more than likely that the sea temperature will be warmer than the air temperature. Thirdly, the device does not remove humidity which has as much, if not more, affect on comfort as temperature. Lastly, if the ocean is at the temperature of the coil, it should already be cooling the adjacent air around the boat anyway as nature is employing the exact same principle with the sea either extracting heat from warm daytime air or radiating heat to cooler night time air.

As a matter of interest, here's a CSIRO point and click SST map of Australia:

Point n click sea surface temperature

[stillbuilding]

Australia has a history of using water filled canvas water bags to provide cool drinking water. In earlier times, posh outback houses had "tunnels" under the house fitted out with wet canvas curtains, cooled air was extracted by fan thru these tunnels and distributed thru the house.

I wonder if a similar system would function on a boat. I suspect not due to the higher humidity but don't have the maths to comment.


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[Canibul]

I think you need a significant delta t ( temp differential) for it to be very effective. Here, if you pump sea water at 84 degrees through a coil, and blow air across the coil, you will get 84 degree air. Duh. The air is 88, so it would be a lot of trouble to lower the temp 4 degrees. A simple fan would be a lot cheaper and provide much of the same benefit.

I worked on the oceanographic studies for the mini-OTEC ( offshore thermal energy conversion) sites in both Hawaii and Puerto Rico. That concept uses the marked difference in temperature between surface and deep water to generate electricity using ammonia as a thermal transfer medium. They needed deep water, close to shore in order for it to be feasible to get the power ashore. But there was something like a 30 degree temperature differential between surface water and deep ocean water in these locations. Not practical for boats.

As I understand it, what was proposed here by the OP is also not the same thing at all as an evaporative "swamp cooler". Which is what some others are suggesting. That's another device entirely. Has nothing to do with the temperature of the water. Uses evaporation to remove heat. Have you ever seen the little burlap/canvas bags you fill with water and hang on the front of your vehicle while driving? That uses simple evaporative transfer to cool the water in the bag as it seeps to the outside and evaporates, taking heat with it.

[Ironman162]

You may well be right but it still depends on the temp differential. Until some actual measurements are taken we wont know.
In principle it can work under the right conditions and there is much evidence to that effect.
I believe its worth exploring and modifying rather than shooting it down outright for now.



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[Canibul]

I wasn't shooting anything down. What i am seeing here are people talking about three totally different designs and getting them mixed together in the process. A radiator is different than a compressed refrigerant system, and they're both different from a swamp cooler.

It's not rocket surgery to see that blowing air over an 84 degree surface will in fact cool or warm the air to near 84 degrees. So the radiator approach would have very limited use in the tropics.

In high latitudes, however, in summer, during a spell of hot weather the surface sea temp would likely be a lot cooler than the ambient air. In that case, the cool water approach would have some benefit. So, off Cape Cod in August, for example, you could get something like 10 degrees or more difference during a hot spell.

[darylat8750]

Originally Posted by Lodesman

Do you understand how a refrigerator works? Marine A/C does the same things - it compresses refrigerant; this make it hot (ideal gas law); the hot refrigerant runs through a heat exchanger that is cooled by seawater - the hot seawater is pumped overboard, and slightly cooler refrigerant is decompressed (making it that much colder than it started) - this is run through a radiator, where a fan blows ambient air over its fins, thus cooling it.

He does understand how normal air conditioners work. He is thinking outside the normal box. Trying to improve comfort with much less energy use than a conventional A/C.

[jcapo]

Cools the beer and the boat. Just need a lot of ice.

[darylat8750]

I agree than the delta in most tropical areas wil be too small for really effective cooling . however the water temperature only needs to be below the dew point to provide dehumidification effect. The collection and disposal of the condensate will be easy manually and not too bad if you can drain it via a shower sump .

[Lodesman]

Originally Posted by darylat8750

He does understand how normal air conditioners work. He is thinking outside the normal box. Trying to improve comfort with much less energy use than a conventional A/C.

That is not clear. If he "saw" a system in Sydney that effectively cools the air using seawater, then he was looking at a marine a/c unit.

[Ironman162]

Im looking at all the options as they are mentioned here and elsewhere.

Apologies if you find that confusing.

I was fortunate enough to see a working seawater cooling system on a boat in Sydney where Im currently moored and I am also looking at SeaAir airconditioners as was suggested by an earlier post in a very professional manner.
I would prefer not to have to put hours on my generator and Darylat8760 highlighted I am looking for lateral ideas.
For what its worth I do know how refrigerators work and understand delta figures

Isnt it too easy to run a 10kva diesel generator for 9 hours running a split aircon.

Thank you for all your ideas, I think the concept is now exhausted and at a risk of being antagonised I won't comment any further.




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[Ironman162]

Can anyone point me to an aministrator please as I seek to close this thread that I started to my regret.

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[Ironman162]

If you are an Administrator can you assist to close this thread please? Thank you.

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