Using Waste Heat

[Dockhead]

Originally Posted by Dockhead

Thanks for all the useful comments. I'm especially pleased to have something from Nick besides a snide comment about sailing in cold climates

How about something like this:

Attachment 66018

I would use the main engine freshwater coolant loop for all heat exchange operations.

The big advantage of this is that it would be much simpler to install, and would not require me to maintain a Micky Mouse separate cooling loop going into the calorifier.

The downside would be that waste heat from the generator would only get into the central heating system indirectly.

Another downside is that all of the heat handled by this system would go through the main engine, which would absorb a lot of it if it is cold (it weighs a lot).

On the other hand, that would be at the same time an advantage in that the main engine would be kept warm for easier starting and less wear on startup.


The other way would be to cut the existing loop from the main engine through the calorifier, make a separate short loop through the calorifier (with its own header tank I guess), which would then need three heat exchangers instead of two.

Either that, or cut the generator loop only through the main central heating loop, with no direct heating of the calorifier. I probably reject that since in summer I may want hot water heating without central heat.

OK, I think this is Plan "A", so now I'm going to go on to costing it out so that I can see whether it makes any economic sense or not.

I've got two plate type heat exchangers at about $200 each, which I need to figure out how to size.

I'll need a few meters of heater hose, and I'll need "T" hose barbs for the generator cooling circuit. I'll need valves for that, and possibly a booster pump for the generator cooling circuit.

I need to find a boost pump for the engine coolant circuit -- can anyone give advice about this? I suppose the flow rate should be chosen carefully so that it is actually boosting the flow (not too little), and not so high as to screw up the way coolant flows through the engine. Anyone have any experience with this?

A starting point might be a school bus heater booster pump, like this:

Bergstrom Inc. introduces new booster pump for bus and specialty market

I don't know what the flow rate is, but surely this would be about right? It costs $125. Some wire, crimp connectors, switch, led pilot lamp -- I have all that on board anyway.

Cost of parts looks like not more than $800. If I want to monitor temperature in a few places to understand how the system is working, I could add a Maretron temperature monitoring box with four under-bolt sensors, which I can monitor with my existing Maretron DSM-250 -- another $400 or so, but I could also just use my laser thermometer.

As far as labor is concerned, I can't imagine it's more than a day's work. If I hire someone, then say $400.

So $1200? Might be worth it even just for the satisfaction of knowing I'm recovering some of the wasted heat. Remember I sail all winter long.

[atoll]

my wife and i have this discussion every year come september............

my answer is allways the same............left turn out the channel,right turn at the canaries...........late november!!!!

[atoll]

this one is probably most suited as the flow rate is adjustable

Jabsco Eco-Circ 12v central heating pump

[Kenomac]

You're chasing pennies with dollars.... or in your case, chasing pence with pounds.

[Dockhead]

Originally Posted by Kenomac

You're chasing pennies with dollars.... or in your case, chasing pence with pounds.

Indeed that is the main danger of this project, and if I don't do it -- it will be because it doesn't seem economically rational.

[Dockhead]

Plan 4:

Install two three-way solnoid valves and simply switch the main engine calorifier loop to the generator.

No heat exchangers, no fuss, no muss, minimal expense.

There would be some commingling of engine and generator coolant -- is the only downside I have thought of. But since I use exactly the same coolant in both, would this really be a problem?

[poiu]

I do not, however, have aircon, and don't plan on installing it unless I get enough time off work to go to the tropics. Aircon is totally unneeded up at these latitudes (above 50 degrees); in fact we heat sometimes even in the middle of the summer (which is why heat is such a big deal).[/QUOTE]

Sorry I shouldn't make assumptions. A non-cost advantage of your project if you ever do it, is redundnacy. When your Eberspacher heating fails as surely it must someday you will still have some heat.

You could buy the whole heating system for buttons from a car breaker's yard and this would work if you restricted the heat recovery to coolant heat. I'll bet a large engine saloon car heater system will put out a lot of heat.

I look forward to reading about the end result.

[Kenomac]

Come join us down here in the Med. Spain specifically. You can store your boat during the winter months and cruise four months on the hook for the price you're going to pay just for the heat transfer contraption that you're trying to design. And down here... you won't even need heat from May-October. Spain is very welcoming.

[Dockhead]

Originally Posted by Kenomac

Come join us down here in the Med. Spain specifically. You can store your boat during the winter months and cruise four months on the hook for the price you're going to pay just for the heat transfer contraption that you're trying to design. And down here... you won't even need heat from May-October. Spain is very welcoming.

LOL, thanks for the kind invitation! I'm sure it's extremly interesting, but I'm not retired! Still have to work for a living! So it's better for me to have the boat near me up here. The most I can take off at one time is a month -- and I feel lucky to be able to do even that -- and then snatch a long weekend here, and 10 days there, for cruising (I get an average of 50 sea days a year, and 90 days on board). Unless I can wangle a sabbatical, I'll be doing that for at least 10 more years.

The flip side of summer in the Med is I bet it can be pretty hot without aircon! It's funny that although I grew up in a really hot part of the U.S., I have come to dislike hot weather. Up here around 50 degrees latitude suits me quite well for the time being.

[Dockhead]

Latest version:



I think I've got it now. This version will require only:

1 pc plate-type heat exchanger $200
2 pcs booster pumps $350
2 pcs three-way solenoid valves ?
2 pcs 3/4" "T" fittings for generator cooling system ?

The system will work like this:

Switch the solenoid valves to choose between main engine and generator (which I never run at the same time anyway).

Switch on the booster pumps.

Hot coolant goes first to the calorifier (priority -- domestic hot water), then to a heat exchanger to give the rest of the waste heat to the central heating system. When the calorfier is hot, all of the heat will go into the central heating system.

Switch on both booster pumps to pre-heat main engine or generator with central heating.

To run central heating on main engine waste heat, have a way to switch on the main circulation pump without the furnace, or simply switch on the furnace and let it throttle itself down due to low demand for more heat in the system.


The parts will cost less than the cost of 1/2 tank of diesel fuel so I believe might even pay for themselves.


Some puzzles:

1. I am a little worried about the engine cooling loop through the calorifier -- it is very long and even now prone to air locks. The hoses are higher at one point than the engine. Maybe I should put in a bleed valve at the highest point? Will that work? Or how to deal with that?

2. Any harm in slight commingling of engine and generator coolant? I use exactly the same type and change them every two years at the same time.

3. I don't understand the dynamics of coolant and heat flow through the central heating system or how to splice in the heat exchanger. I guess I need the coolest part of the flow, so I would splice into the return side of the main branch, right? So the cooled-off coolant returning to the furnace will pick up heat from the heat exchanger, and arrive pre-heated at the furnace, reducing heat demand and invoking a lower furnace setting (or obviating the need to run the furnace at all). Does that sound right?

4. I will be boosting the flow of coolant through the central heating system with another pump. I guess the flow rate needs to be matched to the existing one? Or does it matter?

5. Similar question concerning the booster pump on the engine/generator loop. How to choose the flow rate? Can I screw up operation of the cooling system if the flow is too high?

What do y'all think?

[s/v Jedi]

Originally Posted by Dockhead

Latest version:

I think I've got it now. This version will require only:

1 pc plate-type heat exchanger $200
2 pcs booster pumps $350
2 pcs three-way solenoid valves ?
2 pcs 3/4" "T" fittings for generator cooling system ?

The system will work like this:

Switch the solenoid valves to choose between main engine and generator (which I never run at the same time anyway).

Switch on the booster pumps.

Hot coolant goes first to the calorifier (priority -- domestic hot water), then to a heat exchanger to give the rest of the waste heat to the central heating system. When the calorfier is hot, all of the heat will go into the central heating system.

Switch on both booster pumps to pre-heat main engine or generator with central heating.

To run central heating on main engine waste heat, have a way to switch on the main circulation pump without the furnace, or simply switch on the furnace and let it throttle itself down due to low demand for more heat in the system.

The parts will cost less than the cost of 1/2 tank of diesel fuel so I believe might even pay for themselves.

Some puzzles:

1. I am a little worried about the engine cooling loop through the calorifier -- it is very long and even now prone to air locks. The hoses are higher at one point than the engine. Maybe I should put in a bleed valve at the highest point? Will that work? Or how to deal with that?

2. Any harm in slight commingling of engine and generator coolant? I use exactly the same type and change them every two years at the same time.

3. I don't understand the dynamics of coolant and heat flow through the central heating system or how to splice in the heat exchanger. I guess I need the coolest part of the flow, so I would splice into the return side of the main branch, right? So the cooled-off coolant returning to the furnace will pick up heat from the heat exchanger, and arrive pre-heated at the furnace, reducing heat demand and invoking a lower furnace setting (or obviating the need to run the furnace at all). Does that sound right?

4. I will be boosting the flow of coolant through the central heating system with another pump. I guess the flow rate needs to be matched to the existing one? Or does it matter?

5. Similar question concerning the booster pump on the engine/generator loop. How to choose the flow rate? Can I screw up operation of the cooling system if the flow is too high?

What do y'all think?

I highly recommend you do not do this. Use a series-loop with additional heat exchangers for wngine and genset, or don't do it at all. Installing a heat-pump makes more sense; just put your mind so that while you realize it can be reversed to function as an air conditioner, you only use it for it's main function as heat pump.

[goboatingnow]

1. Long runs in themselves are not much of an issue, as long as air locks arnt currently an issue, Mine are about 10 feet engine to calorifier.

2.co-minging, hmm, operating pressures would be similar,so on the face of it it wouldn't be an issue, valves need to be rated for the pressure, but that shouldn't be difficult

3.for max heat transfer , you want the greatest difference of temperature across the exchanger, so hot to cold.

4. why are you boosting the central heating flow, the Ebespacher unit has a pump

I don't see the need for booster pumps at all.


you will need to fit a thermostatic valve controlled by a strap thermostat so to redirect the flow when the calorifier comes up to temp.

dave

[DeepFrz]

Check out this site. Somewhere on here there is a diagram of what you want, if my memory serves.
Sure Marine Service, Inc. | Webasto Marine Diesel Heaters

[DeepFrz]

Go to this page and click on the Olympia OL-60 link it will bring up a pdf file.
Sure Marine Service, Inc. | Marine Deluxe Heater Kits


Actually the Proheat X-45 shows the engine heat exchanger. The other pdf doesn't.

[Dockhead]

Originally Posted by goboatingnow

1. Long runs in themselves are not much of an issue, as long as air locks arnt currently an issue, Mine are about 10 feet engine to calorifier.

2.co-minging, hmm, operating pressures would be similar,so on the face of it it wouldn't be an issue, valves need to be rated for the pressure, but that shouldn't be difficult

3.for max heat transfer , you want the greatest difference of temperature across the exchanger, so hot to cold.

4. why are you boosting the central heating flow, the Ebespacher unit has a pump

I don't see the need for booster pumps at all.


you will need to fit a thermostatic valve controlled by a strap thermostat so to redirect the flow when the calorifier comes up to temp.

dave

It seems to me that I do need booster pumps, because:

1. The engine coolant loop through the calorifier is very long -- about 40 feet round trip I reckon -- and is subject to airlocks as it is. I suspect the flow is weak since movement in this loop depends on pressure differential in the engine cooling system and one little fresh water pump.

2. I have no idea how to tap the generator cooling circuit in a way to have the necessary pressure difference. If I'm using a booster pump, it won't matter.

3. I suspect the heating system of weak flow as it is. Adding a heat exchanger with a certain amount of resistance will make it still weaker. Surely a booster pump -- properly sized! -- is indicated there.


As to the thermostat -- I have one, which I disabled a long time ago. The main engine runs at a rock-steady 80C and I just let the calorifier run at 70 or 75 or whatever it is capable of getting up to with that system. I have a thermostatic mixer on the output side which lowers the temp of the domestic hot water. Seems to work fine. A diversion loop would be a PITA to rig up. The genset is even cooler -- 70 degrees.