using heat exchanger AND keeel cooler in one loop.

Hi All,

I know this is an unusual set-up but I wil ask anyway - I am not interested in*possible alternativ or better solutions at this stage.

Can*keel cooler water be run through a heat exchanger (steel hull)?
benefits?
draw backs?

An example where this*could be used:*If*one has a way too big keel cooler box (say volume is150 gallons*and a small engine about 100HP) and connects pipes that will allow it to be used for keel cooling. The internal circulation pump is used to pump through the keel cooler and*through the engine.

If operating in really cold waters the keel cooling water*temperature will be very close to the*seawater temperature when it enters the engine again. This result in running the engine too cold.

HOWEVER, if running the keel cooled water straight*through a heat exchanger (where the internal circulation pump is used for internal engine*circulation and the raw water pump is used for the keel cooling) and back through the keel cooler, then the "normal funtion" of the heat exchanger is retained. This basically means that the internal engine thermostat will bypass the*heat exchanger (like during warm-up) and keep the engine temperature at the correct level. When the engine temperature gets too high the engine circulation through the heat exchanger is resumed again.

Benefits: the engine will operate at correct temperature, that*any large cooler can be used, that the system is not affected wether operating in the arctics or in the tropics, that a normal heat exchanger engine can be used with keel cooling (no special engine version required).
Drawbacks: use of 2 pumps instead of one.

Singleprop wrote:I am not interested in*possible alternativ or better solutions at this stage.

Can*keel cooler water be run through a heat exchanger (steel hull)?
benefits?
draw backs?

Click to expand...

Sure. The engine doesn't know where the water comes from as far as the heat exchanger is concerned, it only knows delta T, the temperature in vs out.

However, do you have a wet exhaust? That water has to come from somewhere. The exhaust manifold cooling (if it is seawater cooled now) can be derived from the heat exchanger outlet and go from there to the keel cooler loop. The exhaust spray ring cooling water and shaft lube/cooling will have to be supplied from some other source and might involve adding a dedicated pump with proper controls and monitoring.

There are benefits to your idea but also additional,*though not overwhelming, complications depending on the existing installation.

*

Hiya,
** Correct me if I'm wrong Mr. DavidM but I don't think a keel cooled sytem necessarily needs a dry stack.

using heat exchanger AND keel cooler in one loop.

DavidM wrote:

I don't see any advantage to this idea over a straight keel cooler. A conventional keel cooler circulates glycol coolant through the external cooler instead of a seawater heat exchanger. The engine's thermostat regulates the coolant temperature just fine.

Your idea just adds more complexity with no offseting advantages.

And don't forget a keel cooler needs a dry stack exhaust system whether conventional or with your separate circulating loop.

David

Hi David, the advantages are mentioned in the first post.*

I might not understand engine cooling 100 % (- maybe just 50%), but in this set-up we are using the engines own*circulation pump for the keel cooler. Where would the thermostat divert the fluid to?
This link might help visualize it, just replace the raw water in the middle drawing with keel cooler water: http://www.depcopump.com/catalog107/81.pdf*

Click to expand...

*


-- Edited by Singleprop on Wednesday 3rd of November 2010 10:05:04 AM

Don't attempt to use the existing freshwater pump to circulate the keel coolant. Keep the system as is, the raw water pump will circulate the keel coolant, the fresh water pump will circulate the jacket water and neither you or the engine will know the difference. You check the engine coolant just like you always*have.*

You will need to add another engine driven pump (or electric with proper controls and monitoring) to provide exhaust cooling which may or may not include the exhaust manifold.

Any discussion about thermostats is just noise. The engine already has one.

-- Edited by RickB on Wednesday 3rd of November 2010 10:47:57 AM

DavidM wrote:Doesn't make sense to me.

Click to expand...

"Can*keel cooler water be run through a heat exchanger (steel hull)?"

*"I am not interested in*possible alternativ or better solutions at this stage."

Is something not clear about the original statement or question?

Carey's (of this forum) custom lobsterboat was keel cooled with a wet exhaust when he acquired the boat. The original engine (a Sabre I believe) had a keel cooler that the engine's coolant was circulated through. I assume this circulation was accomplished by the engine's coolant pump. But it also had a raw water pump that was used to put water into the exhaust elbow to cool it and the muffler, exhaust hose, etc. This water went out with the exhaust.

If this installation had engine oil and transmission fluid heat exhangers, I don't know if they were cooled by the engine coolant on its way to or from the keel cooler or by the raw water from the raw water pump on its way to the exhaust.

When he had the boat re-engined with a new Cat, the cooling system was changed to a conventional main heat exchanger fed by a raw water pump on the engine. The raw water from the heat exchanger is injected into the exhaust system.

DavidM wrote:The proposed system adds additional pumps and heat exchangers that will be expensive, adds congestion to the engine room and has more components to fail.

Click to expand...

How is that? The guy said he wants to keep the system as is, no mods to anything and no "improvements."

The existing engine has a heat exchanger, a fresh water pump, and a thermostat.

All he asked about doing is taking water from his high*volume keel cooling installation rather than the sea and delivering that to the existing heat exchanger before returning it to the loop.

The engine would not have the slightest hint than anything in its life has changed. Cold water would enter the heat exchanger and leave a bit warmer, exactly as if it was an open circuit raw water system.*The freshwater or jacket water circuit would*remain untouched.

How he handles the exhaust, red gear,*and shaft*are the only wild cards and he hasn't described*those items*or asked about how to handle them.

The drawing you posted shows a pump taking a suction through a heat exchanger, which is a real bad idea to begin with.
*

Hi David, there is no double teaming, just questions and information changes. I amjust trying to learn here and your replys are helpfull (RickB's as well).

Would the heat exchanger be able to control the engine temperature better since it is matched perfectly to the engine.

Or would the direct keel cooling result in cycling of warm-ups and cool-downs?

Singleprop, Delfin uses a Walter keel cooler with an inline heat exchanger to warm house water when underway.* The flow is from engine through keel cooler back to* the engine with a side loop from the hot side of the cooling loop through the exhanger.* There is only a single water pump for the system, circulating coolant through the system, and that is the pump on the CAT 3306.* I'm not sure how you would design a simpler system.** As you suggest, the thermostat maintains the proper engine temperature, and the circ pump on the engine can handle the flow requirements for the entire system just fine.* Since no raw water is used, no engine zincs are required, just external zincs on the keel cooler.* Exhaust is dry stack.* One advantage of this system is that when at the dock, the boiler or H2O heater keeps the engine and engine room warm through the heat exchanger via convection currents.

We cool the genset through another keel cooler, but also have a wet exhaust since the routing for a dry stack for the genset would have been problematic. We use a water/air separater so the system is a little quieter.* This installation is much more complicated, and only used because a dry stack wouldn't work.

Hope that helps.




-- Edited by Delfin on Wednesday 3rd of November 2010 08:08:36 PM

Singleprop wrote:Would the heat exchanger be able to control the engine temperature better since it is matched perfectly to the engine.


Or would the direct keel cooling result in cycling of warm-ups and cool-downs?

Click to expand...

I'll take one more shot at this then quit.

The existing standard equipment heat exchanger and thermostat works just fine doesn't it? The existing standard heat exchanger uses raw water to cool the jacket water that is temperature controlled by the thermostat.

If you have a large volume of keel coolant as you described and it cools off very rapidly in the cold water where you said the boat lives it will cool the heat exchanger just like it was raw water coming from the sea and returning to the sea. The engine cannot tell the difference. Water comes in one hole in the hull and goes through the raw water pump, then the heat exchanger, then out the other hole. just because there is a big tube or tank or something on the other side of those holes rather than an ocean is irrelevant.

If by "direct keel cooling" you mean to use the engine jacket water pump to move water through the keel cooler, the existing thermostat on the engine will maintain the setpoint temperature. That is what thermostats do.

The only snag with that approach is you might have considerable work to do to modify the existing heat exchanger installation and piping since it probably includes the header tank and pump plumbing. Not knowing what engine you have makes it* impossible to comment on that or how you plan to manage exhaust, gearbox, and shaft cooling.

*

Rick is totally right on. You could run through a keel cooler and then utilize a heat exchanger, but why? The one advantage to normal engine heat exchangers, would be that you'd have no sal****er in the system, therefore adding overall life to the heat exchanger. And all that might make sense if one happen to be installed an engine already having a heat exchanger into a boat that already has a sufficient keel cooler. But, I think it was Rick, and maybe someone else, you'd now have to supply cooling water to the exhaust. Personally, I would remove the heat exchanger, or as I did when I re-powered, remove the keel cooler. I chose the latter, since I was seeking to increase my cruise speed, and wanted to get rid of the drag.

Carey wrote:you'd have no sal****er in the system

Click to expand...

That's interesting, the nanny program protects us from seeing a t****t even if its underwater.

Good word game, maybe "Saltywater" would be more PC
Steve W.

RickB wrote:

*
Carey wrote:you'd have no sal****er in the system

Click to expand...

That's interesting, the nanny program protects us from seeing a t****t even if its underwater.

*

I guess I should have said salt water. Go figure.



*

Would the Nanny program be able to provide information about which kind of fluid would be best to use for the previously mentioned steel keel cooler.

I guess that if its a conversion of an existing keel, then the assumption must be that the inside of the keel is unpainted steel, which*requires that the keel cooling fluid must be added some corrosion inhibitor or similar?

What if the keel is epoxy treated? Same fluid?

Because a keel cooler is in the engines cooling circuit the appropriate DIESEL antifreez is used for the entire system.

In the warm areas as low as 35% antifreez works better as a coolant and has enough rust inhibitors , water wetting agents and all the rest to keep the engine together.

In the North the % of AF will be chosen by how cold the protection is needed.

Singleprop wrote:

the assumption must be that the inside of the keel is unpainted steel, which*requires that the keel cooling fluid must be added some corrosion inhibitor or similar?

What if the keel is epoxy treated? Same fluid?

Click to expand...

It is a safe assumption that the internal areas of a fabricated steel keel cooler are not coated beyond the primer (if any) applied to the pieces before assembly. Welding will destroy the primer in the heat affected zones so epoxy coatings are also out unless the entire system was flushed with cleaner, then drained, dried, and then flooded with expoxy and drained again, and I really doubt that happened so you have to consider the entire area as raw steel.

There are several water treatment "systems" applicable to the keel cooling loop, ask your favorite engine dealer for advice on what works best locally and is within your budget. Remember, there are some nasty bugs that live in cooling circuits. Spend some time researching what is available.

If you use common antifreeze, or if you use a coolant treatment of another type, try and use different colors in the two loops so leak chasing is made simpler.

*

Raw Water pump

Ahoy, Keel cooler to raw water pump to heat exchanger (With or without the core?) Than from the exhaust discharge back to the keel cooler. Is that an acceptable loop or am I missing something.