Additional circuit in diesel cooling system ?

[rossny]

Hi all,
I am going to add an additional anti -freeze loop to my existing diesel cooling loop to use at anchor when the engine is not running. I will tee off the engine hoses entering the heat exchange inlet and outlet of the water heater and add ball valves to close off the loop not being used. I will then use a 12v pump to pump anti-freeze up to a coil of black tubing up on deck to absorb heat from the sun and circulate thru the water heater engine loop to heat the water in my on demand boat system. My question is if the top loop floods the engine, what kind of damage if any could this do to the engine? The engine overflow tank is higher than the engine but way lower than my proposed new loop. Has anyone done this? Thanks

[donradcliffe]

An interesting idea, but it would work a lot better with a hot water strorage tank than an on-demand system. If you have the engine loop valved off when you are using the solar system, there should be no problem--remember that the engine loop is designed for 12 psi, and the pressure in your solar loop should be lower than that unless it runs to the top of the mast.

[Stu Jackson]

Have you done the heat transfer calculations to see if it would work?

Someone came up with a similar idea here a month or so ago, it took us many pages to convince him it was not feasible, not worth the potential damage to his engine. His was based on a storage tank concept.

And if the heat transfer does work, why complicate it with connections to the engine system?

[MarkSF]

You could just get a couple of these :

http://www.target.com/p/coleman-5-ga...B&gclsrc=aw.ds

More comfortable with that than introducing a potential failure point into the cooling system.

[Clivevon]

Solar shower bags - my idea exactly. This is the equivalent of using a pencil to write in zero gravity orbit rather than spending millions to develop a ball point pen to do the same job, maybe?

[rossny]

Thanks for the comments but I have not explained my plan properly. I have a Yanmar 75hp Turbo diesel and a Isotherm Basic 40 11gal marine water heater with a 240v electric heat element for the dock and a heat exchanger for when the engine is running. I know Isotherm makes a water heater with 2 heat exchanger loops for a generator or solar like I want to do but I don't want to change the water heater again. So...
Don, yes it is a hot water storage tank, the on-demand system I refer to is my water pump plumbed to my 2 heads/showers and the galley hot/cold spigots. And that is exactly the advise I was looking for... are you sure that the pressure is 12psi in MY engine? The solar loop should not be higher than 8 ft above the tank, and about 5 ft above the little anti freeze overflow bottle.
Stu, do you remember the name of that thread? also where would one find the heat transfer calculations?
Mark, I am asking these questions first to avoid damaging my engine cooling system. I do have a camping bag solar shower but why would I use it with 2 built in pressure showers on my boat?
Thanks for the comments, all good !!!
Any diesel engineers want to comment ?

[rossny]

Hi Clive, I did not see your response when I began my further explanation. Yes, I think camp shower bags are great for backpacking. But you need to fill them some time before you need them and they can get too hot. I am preparing to move aboard full time and I prefer to anchor rather than dock. This will be our home and to have to go to the cockpit to shower is like going out to the driveway to shower at home. If I did not have 2 showers on the boat and the boat is a day/weekend sailor then camping shower bags in the cockpit it would be. Thanks.

[SeaSon]

Haven't thought about this too hard, but what about putting the ball valves and small circulating pump on the fresh water side - through through the heat loop and hot water heater?

Sent from my SAMSUNG-SGH-I537 using Cruisers Sailing Forum mobile app

[Stu Jackson]

Originally Posted by rossny

Stu, do you remember the name of that thread? also where would one find the heat transfer calculations?

http://www.cruisersforum.com/forums/...ne-165230.html

Heat transfer is a science. I vaguely remember heaps of courses in the subject in high school and college (I am an HVAC engineer). This forum is not the appropriate place to give you a course in it, and my fingers are tired!

One or two of the places one could find out, if one were curious, would be Google and wikipedia. Also the library.

[Stu Jackson]

There was a good heat transfer discussion in that link.

What many folks fail to realize is How Heating Systems work.

Regardless of where the heat comes from in systems with heating coils, the basic concept is air being passed over a coil that has A STEADY AND RENEWED SOURCE of hot water to it. As the air gets warmer, the water gets colder. THIS is the heat transfer. In traditional systems, the now cooler water is returned to the heating medium (i.e., a boiler) and reheated to the design temperature, and sent back again.

In most all of these Mickey Mouse ideas, there is no RECURRING reheat of the water, it is returned to the storage tank, so the source of the water continually gets cooler and cooler, which reduces the amount of heat available, ending up in a steadily diminishing law of return and failure of the system to heat anything.

That is why they simply do not work.

[Pizzazz]

Dear rossny,

While it would be good to avoid repeating the other thread (which I started), I would like to encourage you to try any ideas that reuse heat or collect energy from the sun. First, I strongly recommend not to touch the diesel cooling circuit. You will be introducing additional failure points and potentially running the engine at lower than optimal temperature (the thermostat is supposed to take care of this but still, leave that circuit alone to be on the safe side). Here I agree with Stu.

If you want to use the sun to heat up your hot water tank, just run a circuit off the hot water tap through a collector that you can put on deck, painted black, etc. and then return this water to the hot water tank. This is a very efficient system and many summer houses in Europe get hot water with a similar system.

Now, if you want to store more heat, just enlarge your hot water tank (this is what I am doing, going from 6 gallons to 40 gallons, so that I have more hot water, and enough heat to last me for the night in the winter).

These systems do work because it is just physics. You just need to have the right expectations in terms of ease of use, operating valves and dealing with the additional complexity.

[Djarraluda]

Originally Posted by Stu Jackson

http://www.cruisersforum.com/forums/...ne-165230.html

Heat transfer is a science. I vaguely remember heaps of courses in the subject in high school and college (I am an HVAC engineer). This forum is not the appropriate place to give you a course in it, and my fingers are tired!

One or two of the places one could find out, if one were curious, would be Google and wikipedia. Also the library.

ASHRAE (or CIBSE for the Poms) would be the source of the data, but really, it is too complex for most non-engineers. Look at the simplified data from the Pool Heating mobs.
To be honest, the raising of the water circuit on the engine is dubious. The closed loop there has a head tank and vent, so that needs to be raised as well. Getting a bit complex.
Tap into the domestic hot water side, run up to the polypipe loops on deck and back down to the tank again. You will need a pump and temp sensors. Energise the pump when and only when, the temp in the solar collector is greater than the temp in the hot water system.
To do this by gravity will not work, as the hot water cylinder will need to be above the solar collector. With the collector above the hot water storage, gravity will circulate the wrong way and you will loose the stored heat at night or during low solar gain periods.
This way you can not affect the engine.
Roger

[Captain Bill]

Rossny, your idea has a few flaws, but is generally workable. The problem you have is that the exposed coil system works fine when you're heating a pool because the pool is generally at a low temperature and you are not trying to raise the temperature very much, so the delta T is very low between the collector and the environment, As the water gets hotter in the loop you are radiating a lot of heat out of the loop so when you are trying to make hot water this does not work very efficiently. To work efficiently a collector must be placed in an insulated box with glazing that is opaque to infrared. Low E glass is sold for this very purpose. Getting all of the proper materials to do this well is not necessarily easy for a one off project. A company called Heliatos makes a 2 foot square solar collector which is just about right for a 10 gallon water heater. The unit is marinized and comes with a 12 volt pump, a solar panel to run the pump, and instructions on how to tie it in to your engine loop. All for about $420 USD. I think you would find it hard to duplicate on a one-off basis for the price.
I have no affiliation with the company.

Heliatos Solar

[deblen]

I built a system some yrs ago at my small off grid cottage. I used about 200ft of 1/2" polyethylene pipe & a 12V circ. pump into a 40gal water heater.
I just pumped the tank water around the loop.
Worked-but-you would not believe how hot the water gets if you are not using it regularly. It would build up enough pressure to either pop the tank pressure relief valve or blow a double hose clamped joint.

With enough thermostats,pop off valves,a cooling bypass loop(or other way of dumping excess heat) &,possibly, make up water,you can probably get a system to work & be stable.
I would be very cautious of involving the engine cooling ckt. because of the possibility of over 15lb pressure.

I don't mean to discourage you-I love to experiment-that's how progress happens.
Just passing on my experience. Good luck!

How about a applying 12V solar electric current direct to the 120/240 coil of your water heater-slow temp rise but,if water is already hot,might be enough maintenance watts for awhile??

[phorvati]

Originally Posted by rossny

My question is if the top loop floods the engine, what kind of damage if any could this do to the engine? The engine overflow tank is higher than the engine but way lower than my proposed new loop. Has anyone done this? Thanks

Antifreeze loop has no way to flood the engine. its the raw water side of heat exchanger that does.
I added a second loop of antifreeze. You still run the engine but its pretty fast. In the second loop, antifreeze flows from the block, through oil cooler, and then either through hot water tank or bypassing hot water tank, to another heat exchanger, and then back to the head.
This way, 6 gal fresh water tank gets to 80-90F range about half hour after running at idle. That's the best i could do. I let the oil heat the shower water via antifreeze, essentially.