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Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/22/2016 10:57 AM

Hi there,

I am a building engineering student. I am doing an assignment to compare the pros and cons of the sea water cooled air-conditioning system by comparing with the air cooled and water cooled air-conditioning system.

Here are some of my ideas:

Pros

1.The SWAC got the highest energy efficiency performance when to compare with the other two.

2.Reduce greenhouse gas emission due to 1.

3.Reduce the pollution and annoying.

4.Save cooling medium cost.

Cons

1.Short life cycle of the sea water pipe and some parts of the condensing unit due to erosion.

2.Limited location

3.Extra construction area for pump house

Is there any other idea for this topic?? I wonder if there is any useful reference I can learn in this topic to enhance my work. Thanks for the help and pls excuse my pool ENG.

Have a nice day!

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#1

Re: Comparison of Sea water-cooled AC with other types of cooling method.

09/22/2016 11:06 AM

Perhaps consider the heat that is added to the ocean micro-ecosystem.

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#16
In reply to #1

Re: Comparison of Sea water-cooled AC with other types of cooling method.

09/25/2016 7:01 AM

Thanks!

That sounds a good idea for the aspect of environmental friendly.

May I have some keywords for searching related inf. ?

I did search impact of micro-ecosystem for sea water-cooled air-conditioning sys, but it doesn't work.

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#2

Re: Comparison of Sea water-cooled AC with other types of cooling method.

09/22/2016 11:11 AM

First of all these different types of A/C systems are site and size specific, where one choice may be well suited to the application, and another not...so your comparison makes no sense as there is no context....

SWAC

http://www.tsi.com/uploadedFiles/_Site_Root/Products/Literature/Handbooks/2980245C-HVAC-Handbook-2013-web.pdf

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#17
In reply to #2

Re: Comparison of Sea water-cooled AC with other types of cooling method.

09/25/2016 7:07 AM

U're right!

However, I got no context for this assignment, just simply do the comparison in my part. I will give an assumption context for a practical case to do another comparison.

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#3

Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/22/2016 11:55 AM

Seawater is quite aggressive towards piping and system components, so you will end up using some exotic materials like GRP piping and naval brass. Also, you need to keep various grobblies out of your cooling water circuit, like crabs, jellyfish and barnacles. Further, you may need to treat the water to prevent fouling by various dissolved materials.

At least you won't have the problems associated with an air/water cooling tower, like keeping legionella out of it, and arranging for blowdown.

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#20
In reply to #3

Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/25/2016 7:34 AM

Thanks!

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#25
In reply to #3

Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/27/2016 6:02 AM

I wonder why the risk of legionella disease will be avoided??

Air-cooled conditioning system also gives a sealed chilled cycle, is that right??

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#27
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Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/27/2016 11:28 AM

Legionella is only going to appear in systems with high stagnation rates. The colonies begin under sediment, that gets stirred up in an open circulating cooling system (cooling tower), and carried into the mist particles at the fan ducts.

Seawater cooling is a once-through system as such, and is not generally subject to the same conditions.

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#29
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Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/27/2016 11:37 AM

The legionella is not likely in the cooling liquid in any case. That part of the system is sealed up and not exposed to the circulating air. Usually the legionella issue shows up in drip trays underneath spot cooling heat exchangers or in low points in ducting where moisture condenses and collects. It could be bad though in a swamp cooler.

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#30
In reply to #29

Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/27/2016 11:47 AM

Yes, that is one manifestation of it.

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#32
In reply to #30

Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/28/2016 2:11 AM

Understood!

It is lucky to be here, I learnt a lot!

Thanks!!

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#4

Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/22/2016 1:59 PM

looks like you learning about how the practicality of a design of a device for an application works.

As other said, there is no right or best one size fits all way. Too many variables in the system.

A relevant example of this with Air Conditioning/heat Pump based heating and cooling where I live.

In many parts of the world ground based heat pump systems work super. Just not here. The problem is we have naturally low ambient ground temperatures in the mid 40's Fahrenheit range year round going hundreds of feet down.

It's super for efficient summertime cooling. In fact in many applications all that's needed is deep well or a loop of cheap HDPE pipe layed 4 - 6 feet underground, a small circulator pump and a basic water to air heat exchanger to make a very effective cooling system.

Downside is that for heating it's not worth crap. The ground temp to necessary heat exchanger temp, Δt, plus overall thermal energy source capability of the ground is way too far off to be practical. It's like trying to pull heat out of an ice cube to heat your coffee using a heat pump.

It could be done but the energy expenditure to to pump that little bit of heat out is way beyond the value in both terms of the actual thermal energy value and cost to construct and run the system.

Also in our area using it as a bidirectional thermal storage system doesn't work that well either being at best summertime cooling only puts in about 10 - 20% the energy of what winter time heating needs to take out.

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#5
In reply to #4

Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/22/2016 3:58 PM

Best practical synopsis I have ever read for your area! WTG!

Seawater is certainly useful for cooling, but you will have maintenance issues with organisms (install screens of correct size, really small, since critters grow), corrosion of most metals that is unacceptable, and some scale forming issues, especially if Δt is too large on the seawater side, due to under sizing the heat exchange system.

Depending on local seawater currents in your area, you may be able to tap into a cold current, and this is most desirable.

Best practice: Make sure the system is modular construction all the way down to the pipes, so that it can be taken apart and cleaned, or replaced.

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#7
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Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/22/2016 6:23 PM

And yet people and businesses spend a fortune every year installing them because they work so well everywhere else only to find that about December they have depleted their soil thermal reserves and it back to the old heating systems they had before.

One of the biggest ones I am aware of is at the local University. About 7- 8 years ago they spent a fortune to put in a huge geothermal systems to heat and coo the whole complex so they could get rid of their old NG and coal fired central boiler building that's over 100 years old.

To this day if a guy watches starting around mid December until near the end of the college season that old boiler system is just chugging away like it did for the last 100 plus years.

Rumor from one of the people I met once who works at the college in the maintenance dept said the first winter when their high end guaranteed to go geothermal system bottomed out they would run the old boilers flat out all night until just before sunrise to build up the geothermal systems reserves up for the day so that in the day time it looked like the geothermal was doing the job and the old boiler building was shut down.

From what bonehead stuff have seen first hand that university threw money at and then promptly failed on I would totally believe the story.

Personally I think they should have took their stupid multi million dollar football field renovation money and put a massive solar thermal heat collection system in its place and used that to load up the geothermal heat reservoir any time the sun was shining so it had a viable heat source to pump out of all winter.

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#8
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Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/22/2016 6:32 PM

The subsidy miners and subsidy engineers probably couldn't figure out how to divvy up the grants.

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#11
In reply to #7

Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/23/2016 8:41 AM

OR they could have installed a tire burner.

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#18
In reply to #4

Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/25/2016 7:11 AM

Thanks!

It will be a great material for the further case study.

What is the investment cost for a typical SWC for a 50-storey commercial building??

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#6

Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/22/2016 6:07 PM

Your question reveals that you have done no research on the subject.

That should have been your first exercise, before coming to any forums to ask for help.

Had you done some research, you would already have a longer list of pros and cons, harvested from the MANY papers, articles and literature available on the internet.

The main advantage is the lower specific heat capacity of seawater.

Now, go do some research!

Come back if you need help with advanced theories and knowledge that you have obtained by doing the research yourself.

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#19
In reply to #6

Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/25/2016 7:34 AM

I know my background knowledge of this topic is basic.

I did some research in Scopus and web of science before I'm here, but I can't get what I wanted.

For example, the material used for anti-erosion, types of sea water-cooled condenser which can be maintained separately (some parts of the condenser which contact with sea water directly can be replaced separately instead of to remove the whole), the maintenance cost of different types of cooling system. I just get the idea but have no further information on it.

Most resources I found is about general information and some of that are likely to be useful, however, it takes about $30 US to but the authority, poor me.

For example: Porak, DN (Porak, Dustin N.) ; VanZwieten, JH (VanZwieten, James H., Jr.); Wiles, B (Wiles, Benjamin) (2013), An Analysis of Florida's Sea Water Cooling Resource, MARINE TECHNOLOGY SOCIETY JOURNAL

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#9

Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/22/2016 7:03 PM

Well, I live in West Tennessee, so I think the cost of seawater coolant would be prohibitive .

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#10

Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/23/2016 8:11 AM

Try a search for the US Navy Machinist's Mate rate training manuals. They have a section on air conditioning. They have been using sea water cooled condensing units for a very long time.

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#24
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Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/27/2016 3:46 AM

Not only the USN, but any reputable navy throughout the world have obviously used sea water cooling systems for all their ships, on all manner of systems, whether that be military or merchant navies.

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#12

Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/23/2016 9:08 AM

Consider that all (big) boat's engines are SW cooled.

As far as I know, different metals are used depending of temperature to avoid fouling, but it works

Some powerplants are also on the sea shore ansd use SW to cool.

Their experience could be useful for your project.

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#26
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Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/27/2016 9:05 AM

Slow speed marine engines on large ships are cooled with a manufacturer's prescribed coolant which in turn is cooled by sea water in an heat exchanger, as is the majority of other marine machinery that requires any cooling processes including the subject of this topic refrigeration/air conditioning........the evaporators (tube type heat exchangers) used in these systems are sea water cooled and in the main have tube nests of 90/10 cupro-nickel if the sea water flow rate is kept below 3m/s, if the flow rate happens to be over this 70/30 cupro-nickel is used (uncommon), or they can use titanium plates in plate type heat exchangers.

Cupro nickel exhibits the good heat transfer properties required and also resists fouling and corrosion/erosion.

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#28
In reply to #26

Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/27/2016 11:31 AM

Good answers, the 90/10 alloy is the cheaper and softer of the two cupro-nickels used.

It is also apparently more subject to wear erosion due to system vibrations of supports against tubes (near tube plates out in the middle of a condenser or heat exchanger).

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#31
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Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/27/2016 10:07 PM

"It is also apparently more subject to wear erosion due to system vibrations of supports against tubes"

I can't say that I have seen this problem, however, one problem that can occur, mainly through lack of regular maintenance, is a partial blockage of a tube or tubes (small pebble, ribbon weed, illiterate mussels - they didn't read that copper was supposed to kill them!!!, etc.). This partial blockage acts like a convergent/divergent nozzle, increasing sea water velocity above the recommended 3m/s and erosion/corrosion occurs and holes the tube causing premature failure.

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#33
In reply to #31

Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/28/2016 11:40 AM

The unit in question also had experienced issues with really bad boiler makeup from an improperly designed and operated evaporator that produced water with a pH of about 4.8

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#13

Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/23/2016 11:07 PM

If it were me doing the project, I would pose a lot of questions to the fine folks that build desalination plants. Having worked with them quite a bit, I pretty much know the answer before I ask it.

Bar none, the best in the world at that discipline are the Israelis. They have pretty much overcome the restraints on materials used to build the plants.

If you want to overcome limitations, talk to the people that know the limitations involved and how to work around them.

On the environmental side of your project, too many things are still in a state of flux, and are being promoted via voodoo engineering.

As a side note, there is a much cheaper way to attain cooling than Sea Water or other applications. Take a moment to think about it, and it will present itself. Think groundwater. In my case a 3800 square ft. house in Arizona that is cooled for around $35.00 a month versus $400.00 a month by my neighbors. There is no such thing as a panacea, only creative solutions to issues presented. It helps if you have a background in the discipline you are using to solve a problem. I do not have a background in HVAC, but my idea beats everybody else's hands down. It is something to think about.

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#14
In reply to #13

Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/24/2016 7:23 PM

So you take the ground water and put it through a fan coil unit or heat exchanger and use the cold air or water to cool your home ? What is the inlet and outlet temp of the groundwater ? What do you do with this water after it runs through your system ?

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#15
In reply to #13

Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/24/2016 7:49 PM

Initial cost? Do you have your own well?

In general terms, where are you located?

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#21

Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/26/2016 10:51 AM

A major con is biological fouling. The nuclear industry found that heat exchangers in some areas would plug solid in short order due to proliferation of zebra clams in cooling systems. What grows in your water?

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#22
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Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/26/2016 11:19 AM

Zebra mussels are fresh water.

https://en.wikipedia.org/wiki/Zebra_mussel

It must have been some other aquatic zebra you were referring to. I agree with the statement about fouling due to slime, and macro-organisms.

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#23
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Re: Comparison of Sea Water-cooled AC With Other Types of Cooling Method.

09/26/2016 11:42 AM

You are right that zebra mussels were an issue on the great lakes. My main experience was with emergency cooling hardtanks, where we regularly had to boil out the tank and then go in and manually chisel out the marine growth and replace zinc anodes. Usually, the seawater systems had an oversize allowance for marine growth and add cleanouts to go in and mechanically remove the critters.

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