evaporation water maker

[ccgarnaal]

On board commercial shipping evaporation water makers are more common then reversed osmosis units. They are cheaper and require a lot less maintenance.

For those unfamiliar with the principle:

A closed steel bowl filled with feed water is pulled vacuum til about 0.1 bar absolute pressure. At this pressure water will boil at 45°C. The heat is usual provided by free hot cooling water">engine cooling water running trough a coil at the bottom of the bowl. The water evaporates goes trough a steel wool filter to stop any droplets caught in the damp stream. On top there is a water cooled pipe cooler and a scale to catch the condensate fresh water. You need 3 pumps, one too remove the brine at the bottom. One to extract the fresh water and one air pump to get the unit to vacuum. A feed pump is optional as the vacuum already pulls in feed water and it has to be restricted.


I prefer these units over a reversed osmosis any time, low maintenance and high production.
Disadvantage: the water is pure condensate so you need to ad minerals too make it taste proper.

Has anyone ever seen an evaporation unit on a cruiser?

I've been thinking about building one of these and using a sunboiler to provide the necessary heat so you don't have to run the engine.

Any ideas, suggestions ?

[RabidRabbit]

Maybe its just me but thats sounds more complicated. Regular RO is very simple and basic. I'm from maple country New England where sugers have been doing RO for many years and I grasped the process before ever knowing what a watermaker is. With maple sap you keep the sugar brine and dump the pure water in creek. Maybe on my nuclear trawler when I get older.

[sailorboy1]

Yes I have seen one of a "cruiser".

As an ex-navy mechanic who has worked and operated on both evaporators and vapor distillers, you have to be be kidding. Do you have any idea of the power requirements?

[ccgarnaal]

Originally Posted by Don Lucas

Yes I have seen one of a "cruiser".

As an ex-navy mechanic who has worked and operated on both evaporators and vapor distillers, you have to be be kidding. Do you have any idea of the power requirements?

Yes, compared too a RO unit the mechanical power needs are less but the thermal power demand is massive. I have worked on a cruise ship and we had both multistage evaporators and RO units. We always used the evaporators till we didn't have any heat left and if that wasn't enough we used the RO units.
The evaporators needed about 20kW in electrical - mechanical power and had a production of about 120 tons / 24 h. The RO unit needed 300kW in electrical - mechanical power. and produced less.

[sailorboy1]

Go ahead and design, build, and market one! Opportunity must be knocking for you.

Don't let any of us stop you!

[ccgarnaal]

Just a wild idea and wondering if anyone has one.

[downunder]

Originally Posted by ccgarnaal

Just a wild idea and wondering if anyone has one.

I doubt it.

[GrowleyMonster]

To work economically you need to have your engine running and utilize the waste heat of the engine exhaust for your heat source. A wet exhaust system would not be compatible with that process. Second best is to use the engine cooling water. The more heat you have, the less vacuum you have to pull. Could be done efficiently on a motorboat but I think RO is better on a sailboat.

[ccgarnaal]

Originally Posted by GrowleyMonster

To work economically you need to have your engine running and utilize the waste heat of the engine exhaust for your heat source. A wet exhaust system would not be compatible with that process. Second best is to use the engine cooling water. The more heat you have, the less vacuum you have to pull. Could be done efficiently on a motorboat but I think RO is better on a sailboat.

How about using a sun boiler? They give about 800w of heat / m² and temperatures between 50-90°C.

Of course engine heat is more practicable. An engine gives off about 40% shaft power of introduced diesel energy 25-30% to exhaust gasses. And about 25% to the cooling water.

Thus on a 10kW engine you would have about 4kW of thermal energy. Assuming you are running at full power. Running unloaded it would never work.

[msponer]

Originally Posted by ccgarnaal

How about using a sun boiler? They give about 800w of heat / m² and temperatures between 50-90°C.

These used to exist for liferafts. They were clear plastic and blown up into a sort half beach ball with some extra bits inside, then would float alongside the liferaft. I think the gentleman in 'Adrift' had one -- as I remember from his book, it was quite touchy to use. The sea water in the evaporation chamber on the bottom kept rolling and spilling into the part that held the collected and condensed freshwater. There might be a way to fix that problem... But I'm not sure the production would be considered relevant for non-survival situations.

[onestepcsy37]

in place of either you might consider plain old water distillation units. there are a number available for home use that run on either house current or stovetop. you'll get the purest water possible but not much - maybe a gallon or so per 'run' of the distiller. google on home distillation for a look at what's available. not expensive to purchase when compared to reverse osmosis units and maintenance is cheap too.

and don't overlook the possibility of distilling other liquid refreshments when the feds aint watching...

[bobconnie]

Haveing spent a good while installing and maintaining water distilling systems in Alaska, all I can say is be prepared to spend a bunch of time makeing water and even more time maintaining the equipment! The heat required to make enough water for a boat with 2 aboard, useing what they need, is huge! if you had a diesel fired boiler the amount of fuel you would use would scare ya !!LOL and ya better be in a Cool area where ya might use the heat your gonna have aboard ! and your gonna have water that tastes like crap till ya add some things to it ! RO sytems are far better both from a power useage point, to the better taste output from the system! and when ya concider the fact ya can fit an RO in a lot of places through the boat ! so it takes up less useable room, uses less power, makes a better product, and makes no heat in the boat, so is useable anywhere the waters clean enough to use!( no oil or stuff in the water) But then so do a distillalation unit! no way would I ever consider a still system. RO is the only way to go !!

[Tristan]

We have deeply talked about it in the thread:
http://www.cruisersforum.com/forums/...ter-62469.html
T.

[onestepcsy37]

bobconnie - yes, i googled around and got the 'knowing'. a 'tabletop' distiller will give you a gallon in about five hours - no competition for an ro unit. uses either 600 watts or 3000 watts depending on how you interpret their advertising. so on a cost per gallon basis i don't think you could beat ro.

there's also a stovetop model but i can't imagine how much lp gas you would need to make a gallon. otoh, if you were ever stranded on an island (a very wooded island) you could use the stovetop model over a campfire - so score one for the distiller.

and tristan, when it comes to 'free fresh water', nothing beats my rain catching tarp...