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Old 15-06-2017, 15:05   #61
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Re: New Marine Refrigeration System

No. Sold the Coronado 23. The boat I care for now is a Hans Christian 48T hull #8, originally splashed in 1988.

Thanks for reminding me to update my profile.
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Old 15-06-2017, 15:36   #62
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Re: New Marine Refrigeration System

Disclaimer- I'm certainly not a refrigeration expert by any stretch. Many on this forum are certainly a lot closer to that definition than myself so perhaps they know more about it than me. I do do some work on 134a refrigeration systems as part of my job. This is just a bit of a pet interest of mine.

Will it work on a boat? In my limited knowledge opinion I cant see why not. Refrigeration systems essentially dont know or care if they are in a house, car or boat. The basic components and operation is the same.

Have I done it or know someone that has? That would be a no. Specifics, again nope. Only what I've read, and know of some people doing. Anyone interested google it. It's not a secret.

I can add a few things about it. Like most things it has its limitations and detractors (possibly CFC producers?). Its flammable. I know there has been some scare mongering relating to use in cars. My understanding is that it is a small quantity so an unlikely worst case would result in a very small puff. I guess the people pushing this line neglect to mention the gasoline tank most cars are sitting on top of.

It is starting to gain some traction in some corners of the globe but is still not commonly used or available. PS It is not your garden variety BBQ gas propane. It is a filtered drier version. As I'm sure most of us know moisture in fridge systems isnt the best. Hence vacuum evacuating and receiver dryers. Ice clogging the expansion orifice will mostly ruin your cooling day.

I'll let you guys decide if its got any traction. But it is perhaps a little bit of food for thought.

Ok having thrown that cat among the pigeons. Let me get really crazy.

Using heat to cool. Sounds like a perpetual motion to good to be true scam eh.

There are some really 'clever' people out there doing outlandish things like using solar thermal or other waste heat to run refrigeration set ups. The old kero camping absorption chiller set most people are aware of. So others have done some good research of using solar heat to run shopping centre air cond plants.

Steam jet cooling used on the old 1st class carriages on the Santa Fey steam trains a hundred years back. Again some research projects have used solar thermal to run a steam jet cooling. Solar heat energy source, with water as the refrigerant.

Hmm the hotter the weather the better it cools.

Anyway seeing I'm on a roll stirring ya'll up.

OK getting a little closer to reality. Solar thermal assisted air conditioning compressor units. Ie household split system with solar hot water heating up the R134. Why the hell would we want to heat up something that's meant to be cooling us or our food. Well the over simplified explanation is the compressor 'compresses' duh, raises the pressure. Which also heats it, according to Mr Boyle (isnt it?). What about if we start by heating it, the pressure would also increase. This is work the compressor doesnt have to do so unloads it, ie less amps (be they 110/240vac or 12vdc). They are all amps required to crank a loaded compressor, the more load the more amps. From my observations Amps always seem to be a rare and precious commodity on sailboats.

Also hotter refrigerant going into the condenser is a greater delta T so it will work better.

Some people claim around a 50%+ decrease in Watts used in a 24 hr period. I've seen 70% claimed by doing this and using R290. Call me sceptical about these numbers.

My crazy thinking is on a sailboat is maybe have a solar hot water panel helping your fridge and or Air cond sys. Solar thermal is not so fussy about shading so location is not as critical. I'm thinking cabin roof top under boom. But possibly better/ more practical is to use engine/ generator hot cooling water. What about store some hot water to use through the night to reduce batteries getting hammered more than they already will be.

Just looking for someone crazier than me, with more time and money to get some of this going. Please post results. I will be wholeheartedly emotionally supportive.

OK I'll bite if its so good why isnt it being done? Short answer it is by a limited number of 'fringe' enterprises. Dont ask me for specifics. In our information age given this many clues anyone interested can find out much more than me, some of it might be true too. It's not a secret.

I'm sure I will get enough responses saying its all a load of you know what for a plethora of reasons. I'm sure they are all right.

OK if it's so good why hasn't been snapped up by big manufactures? Well the conspiracy theory I heard was that all the big manufactures know about this. But its not a viable business model for them to stay competitive/ make money. Ie unloading their compressors to that extent would increase the average life cycle to 15 years from 4.3, making units sales plummet. You get the picture. Of course that would never happen- right?

Doable, viable, practical or scam? I'll let you guys decide.

Feel free to not take any of this seriously.
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Old 15-06-2017, 16:11   #63
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Re: New Marine Refrigeration System

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Refrigeration systems essentially dont know or care if they are in a house, car or boat. The basic components and operation is the same.
No sure that would go for propane, how flammable/explosive are the other refrigerants ?
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Old 15-06-2017, 16:53   #64
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Re: New Marine Refrigeration System

As Q Xopa said, using heat to compress the gass is one way to do it. I've seen it done in commercial applications. I have also seen the gass (propane) compressed using normal means.

Which is more efficient depends on if you have a ready means of expendable heat or horsepower to drive the compressor.

Aircraft also use compressed air (bleed air and at 400 degrees F, may I add) to cool the cabin. With out 35 degree valves, any moisture in the system will become a large block of ice.

So yes, you can cool with heat.

As far as explosive potential of a propane system, only if you have a leak and an ignition source.
Remember the fire triangle. You need fuel, ignition source and air. Take any one away and no threat.
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Old 15-06-2017, 17:31   #65
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Re: New Marine Refrigeration System

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As far as explosive potential of a propane system, only if you have a leak and an ignition source.
Remember the fire triangle. You need fuel, ignition source and air. Take any one away and no threat.
Boats are not impervious to leaks nor ignition sources. Hence my question on the flammability of the other common refrigerants on boats. I have no interest in refrigerants used in buildings or aircraft.
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Old 15-06-2017, 18:51   #66
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Re: New Marine Refrigeration System

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Boats are not impervious to leaks nor ignition sources. Hence my question on the flammability of the other common refrigerants on boats. I have no interest in refrigerants used in buildings or aircraft.
Fair enough.

Most if not all refrigerants used in recreational boats is nonflammable.
The oil in the system most likely is.
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Old 15-06-2017, 21:49   #67
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Re: New Marine Refrigeration System

Ah Aircraft air conditioning. Yes not strictly true that is an example of using heat to cool. Again not being an expert but I am an aircraft engineer so perhaps I know a little. You are referring to an 'Air cycle machine'. As apposed to the normal refrigeration systems are 'vapour cycle'. They are basically a turbo charger, 2 actually, driven centrifugal air compressor. So they use bleed air from the compressor section of the jet engine to spin up the compressor. Yes the air is quite hot. like 200C ish but its the pressure and flow they are using to make the compressor spin. I guess it could be said that indirectly they use heat by of burning kerosene to turn the compressor, But that is in the same way a car motor uses heat to turn it's air conditioning compressor.

In my humble opinion and experience working on such devices air cycle machines are brilliant devices. They never seem to give much trouble. The vapour cycle systems I work on, 134a air conditioning systems on helicopters, are frequently demanding my time. Fixing leaks, recharging, often, changing compressor drive belts and compressors, less often but still often enough. I've never changed, never had an air cycle machine break down. Although to be fair I havent seen them in my market for a while now. Mostly today they are car derived Nippondenso based systems. Cheap I guess.

No refrigerant to leak, its only air. Which isnt greenhouse destroying, toxic, flammable, expensive etc. Its also not limited by a boiling point so can be as cold as you want, ie cryogenic.

Some Brits did some research on Aircycle machines used for supermarket display case freezers. Using modern efficient elec motors it came out roughly similar in efficiency to vapour cycle units. So no gain there. However if no refrigerant is a gain then it could have an advantage in that regard.

Germans are using Air cycle machines in some passenger trains.

Anyway unfortunately it is not the established mass produced technology so we arent likely to see it. Apart from maybe people playing around. So it wont be able to be to compete on a cost basis.

So essentially more UFI, but seeing it was mentioned.
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Old 15-06-2017, 23:33   #68
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Re: New Marine Refrigeration System

Not a refrigeration expert but my understanding is that most refrigerants aren't flammable. People always seem to be nervous about this. Keeping this in perspective in the US, my understanding is R290 conversions are approved, with with a few changes. like warning labels stating the refrigerant is flammable. This is mainly for the benefit of the service guy that might be smoking when he releases the gas to atmosphere, so he doesnt end up having to paint on a new eye brow. Of course a big no no by a long shot. But I guess they are trying to make it idiot proof. (There's always a 'better' idiot around the next corner).

Again I never seem to hear the question like is my car gasoline tank flammable? Guess what the answer to this is. But mums all over the planet dutifully and responsibly strap the kids into the rolling bomb and shuttle them off to school all over the world. OK dramatics aside the risk is obviously very small. We dont hear of this being an issue do we. I would argue a R290 air cond sys is even less risk because of the minute volumes involved. Or if there is a leak into my car is it alright to breath? Or for the more environmentally conscious will my air conditioner gas hurt the ozone layer? The answer to these questions are pretty obvious.

Smokers carrying the humble lighter around in their pocket. Doesnt get questioned much either does it. But imagine the potential there. It reminds me of a poem about a boy standing on a burning deck.

Again a bit of perspective, statistical reality is far more likely be killed in your car form it crashing, or being crashed into a high speed. I dont hear many questions about that. But people love to zero in on the risk of singeing an eye brow from a leaky air cond.

OK let me scare you some more, lead acid batteries produce hydrogen, ala Hindenburg fame. We all know how that ended. I have personally seen (inadvertently initiated) blowing (ie loudly and dramatically exploding) the top off a lead acid battery. Picture this in a jungle camp, before dawn. I jumped in my trusty flat bed small utility truck to go to work. Anyway turned the key to start it and everyone, including me, that was asleep a millisecond before was immediately awake in the camp. The top of the battery landed perhaps 40 metres away in the centre of the camp. My assistant about to get in the passenger seat was more or less in front of the batt (mounted on chassis rail just behind cabin on passenger side), when it went. He got splashed, with some acid, not badly enough to burn him, after he rinsed off, but put lots of tiny holes in his overalls. His eyes were bulging when I looked over after hearing a big noise. We laughed about it later but we were accutely aware of how that could have ended up.

By the way upon further investigation later we noted the battery terminals were badly corroded, (not being of the highest quality to begin with). This was not in a developed country, but is possible anywhere. The local mechanic had 'fixed' that troublesome terminal that was causing starting problems by hammering some nails and other little bits of metal into the gap left by the corrosion. Gotta love their initiative eh.

Seeing I'm on this rant, statistically the biggest killer in the western world is heart disease. Cancer and car crashes are the next biggest. I havent heard people ask if this fast food hamburger is risky.

By the way talking about risks, you do know that sailing can be considered a bit risky.

Of course I'm not suggesting R290 should not be handled with some caution.

Anyway that's enough from me, now I've made everyone paranoid,

Have a happy and safe day all.

Cheers.
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Old 16-06-2017, 05:00   #69
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Re: New Marine Refrigeration System

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Ah Aircraft air conditioning. Yes not strictly true that is an example of using heat to cool. .
"Q"
I don't process the "gift of pen" like you do, so please excuse my short answers as just that. Short answers. I'm not trying to be glib or snotty.

You are half right about ACM's spinning because of pressure and volume. But the whole pack system operates off of Delta "T". If you don't have the correct inlet temp on the Primary Heat Exchanger, the whole systems performance deteriorates to the point of not working at all.

Hence the reason for multiple bleed air stages. Some think it is to maintain pressure. But the real reason is for temp control.

As far as ..."not giving much problems", Yeah right!!!!
They are a far cry better than the old "Freon packs" and "turbo compressors" of yester years. But still a PITA!
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