use of sea water for condenser water 1

[abuwandi]

a friend of mine is involved in design of 400000 sq. ft hotel project in the middle east. the hotel to be located on an island.he asked me about the possibility of using sea water as condenser water at chillers. not having any experience with this systtem, what are the challenges one
could confront implementing this system? and at what size
of project it can be made feasible relative to air cooled chillers or cooling towers. it seems to me corrosion of piping and heat exchangers, filtration and blockage of
water intakes are some of the issues.

 

[butelja]

The seawater could be handled by having two cooling water loops. The chillers and all other cooling water users making up the primary loop could use fresh water with corrosion inhibitors added. The seawater can be handled in a secondary cooling loop using appropriate materials of construction for seawater. A plate and frame heat exchanger (probably titanium) would be used to reject heat from the primary fresh water loop to the secondary (open) seawater loop.

By using this setup, all chillers, coils, etc. could be made of standard materials. Only the secondary seawater loop would need more exotic materials of construction. The chillers would probably be much more efficient using this scheme than by using air cooled condensors, because your ambient dry bulb temperature is likely very high.

 

[leatherneck]

Be careful of seaweed, mussels, or other growth that could clog the seawater intakes. A simple addition of chlorine at the intake should minimize problems.

 

[GGW]

abuwandi,

Sea water is used in many shell and tube exchangers (if this is the type of exchanger used) for condensing refrigerants used in air conditoning and marine applications. The most common tube material used is 90 / 10 Cu-Ni with 90 / 10 Cu-Ni clad tubesheets. The inside of the heads are usually coated with some sort of tarset material to prevent corrosion of the heads. The heads along with the rest of the exchanger is made out of standard carbon steel.

 

[centrifman]

GGW is correct, sea water is used in many sea water applications. In addition to 9010 tubing, you can also get titanium/titanium clad tube sheets or stainless steel. These tubes will last longer; however, with these exotic tubes in the condenser the performance of the chiller will be reduced. Any of the chiller manufacturers can run a selection with and without the exotic tubing so that you may see the difference in kW/ton. Also, the tar epoxy works fine for corrosion, but doesn't work the greatest with regards to erosion. If there is any chance of erosion a ceramic based coating would be best. This can be applied to both the steel heads and tubesheets.

 

[Vijayaraghavan]

Generally 500TR and above would be better economical selection for special type condensers with direct sea water used for chillers

The infrastructure facility may be expensive like sea water intake well, screens, pump room etc and dischrge back to sea. But considering the low operating cost of the system, the pay back may be good.
Regards
R.Vijay

 

[paulkeating]

We designed a seawater primary/secondary system here in Sydney and found that the mussel spores got into the system and as they grew they got to "learn" the pattern of chemical dosing (which was supposed to get rid of them) and they would "close up" as that time approached, and open up again afterwards ...

Clever little blighters ....

We had a lot of trouble with environmental control getting approval for chemicals for mussel-limitation, and also had to use a venturi at the hot water discharge to ensure we got a very quick mix so that we didn't overheat too much of the surrounding water for fear what it would do to the marine life ...

 

[HVAC68]

well, the primary & secondary heat exchangers may result in higher inefficiencies due to 2 level heat transfer. There are chillers for Marine water application. I know that there is a separate division in Carrier which deals with that. Not sure about ther rest. Best thing would be to consult the manufacturers.

Just thinking loud - how is the air-conditioning done in ships ???

HVAC68

HVAC68

 

[MarauderX]

paulkeating: i remember reviewing a similar problem in Ithaca, New York where the university campus utilized the lake. Zebra mussels were the cause of poor intake, but they found that the suckers were detered by certain light sources. They finally mounted a light at the intake after they had already tried adding more piping with a greater inner diameter to allow for the mussels (they just grew on top of each other to block the intake), and after they had tried to add complex grates at the intake (mussels just grew all over the grates to block flow). I would bet that other mussel species have the same reaction. Funny little buggers.

Using sea water demands that only certain materials be used, and that the system be completely separate from the closed chiller loop. Many manufacturers make appropriate heat exchangers and can recommend how often to maintain them.

 

[Centrif]

All the large ships in the US Navy as well as those in UK and most of the other NATO countries use seawater cooled chillers. Most are direct seawater loops with 90/10 Cu-Ni tubes and clad heads with annodic/cathodic plugs (sacrificial metal). Many cruise ships use a very similar setup. Several use titanium tubes/heads and one new class of submarine has the chillers on a secondary fresh water loop. Unfortunately this has the effect of raising the actual head the chiller must operate at due to the losses relative to the secondary loop heat transfer. Brand "Y" makes them all and has an engineering group dedicated for these applications.

 

[Keith53]

Centrif is correct,

I worked with same for 20 years.

All major chiller manufacturers make direct S/W cooled chillers for marine applications.

Direct cooling is certainly best when possible.

Shore based fixed installs nearly always encounter problems due to marine growth/obstruction. So back-up conventional F/W Towers are not a bad idea unless design/appearance prevents it.

That problem, the extent of it, and the answer to it would be best addressed by marine engineering firms with experience in that local.

 

[rmw]

Not knowing where this island is, also be careful if the sea water you intend to use is brackish. While Cu/Ni materials are excellent for regular seawater, certain chemicals and compounds found in brackish waters near the coast can be "death" to them, as my old Chief Engineer at the company where we manufactured salt water desalinators would always say.

rmw

 

[Cooky]

I've selected many chillers for marine applications, as many have already mentioned 90-10 copper nickle condensers are commonly selected. As an additional form of protection, Sakaphen is added to the 90-10 Cu-Ni during construction to significantly increase the protection against corrosion and it also protects the heat exchange surface against fouling.

For a typical chiller, 90-10 Cu-Ni plus Sakaphen is double the cost of 90-10 Cu-Ni alone.

Cooky