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MrsM

Cooling

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2 hours ago, Tony Brooks said:

The heat exchanger has two pairs of connections. The return from the calorifier to engine goes through one pair and the other pair is inserted into a wet central heating system. Heat from engine coolant is thus transferee to the central heating allowing the central heating pump to circulate it. On a gravity system positioning of the heat exchanger is important so the hot water it produces can rise in the pipework.

Thanks Tony, succinct reply.

Even with the boat warm, you can dump more heat as the temperature difference between the air ambient temperature and the cooling water temperature of 82+ degrees is significant. Radiators do what it says on the tin!

TD'

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2 hours ago, Tracy D'arth said:

Thanks Tony, succinct reply.

Even with the boat warm, you can dump more heat as the temperature difference between the air ambient temperature and the cooling water temperature of 82+ degrees is significant. Radiators do what it says on the tin!

TD'

 

Great, just what you want on a hot summer's day! 

 

On a similar recommendation from a forum member I did actually try the heat exchanger to C/H system to dump engine heat before giving up on the idea and installing an extra skin tank. It was a tubular heat exchanger and once I'd sorted the pump out the rads got hot, but as soon as the calorifier and the 4 rads were hot it made little difference to the engine cooling. Those who've made it work are obviously better heating engineers than me, but even if you do get it to work you just end up with a sweltering cabin on a hot summer's day, so it's not really the best idea unless you want to turn your boat into a sauna.

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11 minutes ago, blackrose said:

 

Great, just what you want on a hot summer's day! 

 

On a similar recommendation from a forum member I did actually try the heat exchanger to C/H system to dump engine heat before giving up on the idea and installing an extra skin tank. It was a tubular heat exchanger and once I'd sorted the pump out the rads got hot, but as soon as the calorifier and the 4 rads were hot it made little difference to the engine cooling. Those who've made it work are obviously better heating engineers than me, but even if you do get it to work you just end up with a sweltering cabin on a hot summer's day, so it's not really the best idea unless you want to turn your boat into a sauna.

 

I think its best thought of as an additional heat source when winter cruising if you normally heat by diesel or gas. If the rads got close to the engine running temperature then they could not dump enough heat so you would have overheated. It would also depend upon the ambient cabin temperature because the amount of heat transferred depends upon temperature difference.

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This is what I did and connected it in series to the existing skin tank. Completely solved the problem. It never gets above about 88C on the gauge now. Obviously on a NB you wouldn't have space to weld it on the inside and would need to get the boat lifted out to weld it on the outside.

P1000823 - Copy.JPG

3 minutes ago, Tony Brooks said:

 

I think its best thought of as an additional heat source when winter cruising if you normally heat by diesel or gas. If the rads got close to the engine running temperature then they could not dump enough heat so you would have overheated. It would also depend upon the ambient cabin temperature because the amount of heat transferred depends upon temperature difference.

 

But if the OP's problem is engine overheating then that will happen in summer too and an additional heat source for the cabin in winter is not their primary concern and will just be a nuisance in summer.

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I might have missed it but were the dimensions of the skin tank in question ever mentioned? If not I'd help!


The engine may be rated at 40HP but I cannot imagine that you could ever expect to apply 30Kw to the water.

Here I am working on the rule of thumb assumption that 1/3 of the calorific value of the fuel produces useful power, 1/3 goes up the exhaust and the other 1/3  has to be shed via the cooling system. That of course is the bit we are talking about.


My old 70ft Les Alllen with its old National DM2 weighed  in at 23 tons.  The National was rated, if memory serves, at a miserly 14/15 bhp. There was no way you could apply even that modest amount of power before the tail squatted and a serious wake was created. Under normal conditions 1/4 throttle was quite enough so there is no way that the OP is going to be able to apply 30Kw even if it is available,. The cooling required is proportional to the power you can apply, the skin tank my be undersized for 30 Kw but is it undersized for the power you can usefully apply? Try it out before spending money!


Remember that my National engine for all its modest power once coped with two 70ft working boats and maybe 60 tons of cargo.


If the engine does overheat then I'd be looking at the circulation system before adding another skin tank.

 

 

 

 

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1 hour ago, Man 'o Kent said:

I might have missed it but were the dimensions of the skin tank in question ever mentioned? If not I'd help!


The engine may be rated at 40HP but I cannot imagine that you could ever expect to apply 30Kw to the water.

Here I am working on the rule of thumb assumption that 1/3 of the calorific value of the fuel produces useful power, 1/3 goes up the exhaust and the other 1/3  has to be shed via the cooling system. That of course is the bit we are talking about.


My old 70ft Les Alllen with its old National DM2 weighed  in at 23 tons.  The National was rated, if memory serves, at a miserly 14/15 bhp. There was no way you could apply even that modest amount of power before the tail squatted and a serious wake was created. Under normal conditions 1/4 throttle was quite enough so there is no way that the OP is going to be able to apply 30Kw even if it is available,. The cooling required is proportional to the power you can apply, the skin tank my be undersized for 30 Kw but is it undersized for the power you can usefully apply? Try it out before spending money!


Remember that my National engine for all its modest power once coped with two 70ft working boats and maybe 60 tons of cargo.


If the engine does overheat then I'd be looking at the circulation system before adding another skin tank.

 

 

 

 

Hi there. The tank is exactly 7 sq/ft. I'm planning to try not worry too much this season, learn how the boat handles rivers and take it from there. Everyone's advice has been invaluable. 

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7 hours ago, Tracy D'arth said:

Thanks Tony, succinct reply.

Even with the boat warm, you can dump more heat as the temperature difference between the air ambient temperature and the cooling water temperature of 82+ degrees is significant. Radiators do what it says on the tin!

TD'

About 3 Kw or 4 Hp

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58 minutes ago, ditchcrawler said:

About 3 Kw or 4 Hp

Enough to hold the engine temperature down, its more than you get with a single coil in a calorifier dumping hot water overboard which is often quoted a solution to overheating engine.

TD'

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On 16/07/2020 at 09:28, Bee said:

As a long term solution a bigger skin tank is the answer but I have seen car / van engines installed pretty much straight out of the vehicle complete with fans and rads and they worked sort of OK. Nowadays most car rads are complete with electric fans and shrouds so I reckon a bit of basic plumbing and bodged wiring would assist the cooling just fine. Might make the engine compartment a bit warm though.

there used to be a lot of rogue eel fishing boats on Lough Neagh that were designed to be able to outpace the official fisheries high-speed patrol boat.

 

they were lightweight clinker open boats with a socking great truck engine dropped in, including the rad and the gearbox.

 

 

neagh.jpg

Edited by Murflynn

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1 minute ago, Murflynn said:

there used to be a lot of rogue eel fishing boats on Lough Neagh that were designed to be able to outpace the official fisheries high-speed patrol boat.

 

they were lightweight clinker open boat with a socking great truck engine dropped in, including the rad and the gearbox'

 

 

neagh.jpg

I have seen a Narrowboat with a similar setup, great big rad in the engine room. Remember cranes and draglives worked like that with a fan drawing the air through the rad.

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23 hours ago, MrsM said:

That sounds like a good setup. I could see all the way round ours but it sounds like it shouldn't be much of a problem. Great idea to have a heated wet locker on your old boat.

I fitted my boat out with a wet locker. Trouble was that it soon filled up with everything except wet oillies. Now use the shower compartment for wet gear.

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On 16/07/2020 at 09:34, The Happy Nomad said:

The prime method of cooling a car radiator is air flow surely? The fan is just for assistance, usually when stationary. The fan would be running permanently and the heat would not dissipate.

Here is one with a radiator and fan, the thread is live at the moment 

 

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1 hour ago, ditchcrawler said:

Here is one with a radiator and fan, the thread is live at the moment 

 

As the OP The issue with this system and overheating seems to be that it was loosing water and coolant from a poorly attached hose the black one over the top of the engine  The fan mentioned comes on when the engine gets hot to cool the engine  and it does work. The system will be available at the end of August as we are swapping out our engine. 

Here is another picture of it 

 

FB_IMG_1595415500146.jpg.afe89a69518b27685d966a4f6bb9a127.jpg

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