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Old 23-01-2007, 15:53   #31
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An interesting idea and fun to do, but as someone else said, a big bank of batteries, an inverter and an air conditioning unit might be a lot easier in the long run.

Chris




But certainly not cheaper, ........or lighter

Those Honda 4 stroke gennies are very quiet, especially if in an insulated box.



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Old 23-01-2007, 17:45   #32
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i think it sounds reasonably plausible, it'd be interesting to follow youfr progress
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Old 23-01-2007, 18:51   #33
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Interesting idea... ignoring the problems associated with powering the compressor, he is talking about one mother of a holding plate, really, to keep his entire boat cool. Could work, so long as he doesn't use ice. Ice insulates, while liquid will readily absorb heat.
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Old 23-01-2007, 19:02   #34
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hes only talking about cooling down one room i think
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Old 23-01-2007, 19:16   #35
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Yup... meant the above post in a completely positive manner. I think it could be done, given the right way to cool the eutectic solution (need salt water at a min to store the requried BTUs). Aside from how to run the compressor, another huge drawback in my mind would be all the wasted space of the tank. But still... theoretically possible.
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Old 23-01-2007, 20:04   #36
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Chris-
" For every kW of electrical energy they consume they provide 4kW of cooling (or heating if you are in a heating climate). "
They may be very efficient, but you've just described a perpetual motion machine. There must be some misunderstanding involved, because NO machine can have an output power greater than the input power. Not here, not now, not according to the laws of thermodynamics and the universe as we know it.

From Honeywell, who make AZ-20 aka R410A "the refrigerant 410A is at least 5% more efficient than R-22,"

That's all there is, a 5% gain in efficiency and in order to get it, the entire system must be designed to operate at higher pressures--this is not a retrofit.
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Old 23-01-2007, 20:33   #37
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yes i was thining of that too but you could have a long wide skinny one as this would give it good surface area to absorb heat
as for the perpetual machine its realted to the cop
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Old 23-01-2007, 21:39   #38
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Quote:
Originally Posted by northerncat
yes i was thining of that too but you could have a long wide skinny one as this would give it good surface area to absorb heat
as for the perpetual machine its realted to the cop
sean
C'mon Sean, did'nt you say you are a chalkie?

What's the above mean ?

Bad spelling, or speaking in tongue's

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Old 23-01-2007, 21:53   #39
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ummmmmm

Typical heat transfer coefficient for such a system using thin walled tube and proper mass rate to achieve proper heat/mass transfer will be about 350-400 BTU / (hr) (ft.sq.) (deg F.)
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Old 23-01-2007, 23:25   #40
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HAHA yes but ive only just mastered 2 fingered typing, it was a bit of a drawback as a network engineer, always took a long time to write scripts and batch files

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Old 24-01-2007, 00:02   #41
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Nothing to do with perpetual motion

Quote:
Originally Posted by hellosailor
Chris-
Quote:
Originally Posted by hellosailor
" For every kW of electrical energy they consume they provide 4kW of cooling (or heating if you are in a heating climate). "
They may be very efficient, but you've just described a perpetual motion machine. There must be some misunderstanding involved, because NO machine can have an output power greater than the input power. Not here, not now, not according to the laws of thermodynamics and the universe as we know it.

From Honeywell, who make AZ-20 aka R410A "the refrigerant 410A is at least 5% more efficient than R-22,"

That's all there is, a 5% gain in efficiency and in order to get it, the entire system must be designed to operate at higher pressures--this is not a retrofit.
It's nothing to do with perpetual motion and all about moving heat. In a heating application using an R410A heat pump you typically use 1kW of heat to move 4kW heat from a low grade heat source, the sea, to where you want it in the boat. This is 400% more efficient than using that same kW to heat the boat using resistance heating (which is 100% efficient). This gives it a COP of 4.0. In a cooling application, you cannot say the same because there is no equivalent method of cooling, but you still move the heat from where you want it to where you don't. The latest generation of heat pumps using R410A refrigerants are significantly more efficient than older models. These new heat pumps are used extensively in Europe and Japan, where they care about energy usage, but not in the US I believe.

Regarding the space and weight issue. In a catamaran, you typically have a large void in both bows, separated from the rest of the boat by bulkheads. This maintains buoyancy at the bows to lift the boat on the wave rather than crashing through it. This shouldn't be used to store anything heavy while sailing as it will destroy the boats balance. Insulating both and installing a tank and filling both with seawater when at anchor, gives you the opportunity to heat one and cool the other with a heat pump moving heat between the two. Insert two heat exchangers in each tank. If one becomes too hot or too cold, depending on whether your primary use is heating or cooling, you pump in sea water replacing hot/cold water, to equalise the temperature and reduce the temperature gradient. Pump fresh water through one heat exchanger in each tank to provide hot and cold running water. Pump glycol water through the other pair of heat exchangers in a closed circuit and route them to a climate control fan coil unit in each cabin and you have your space heating or cooling. Next morning, you run down the heat and or coolth in your bow tanks, pump out the sea water, up anchor and away you go. All in all, it is a pretty efficient system, providing free heating or cooling depending on whether primary use is cooling or heating. However, it is complex. Didn't someone once say Keep it Simple Stupid.

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Old 24-01-2007, 17:19   #42
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Ah, so it was a translation error. I read "provide" heat to mean MAKING it. Heat pumps, which are on the US market and have been for years, simply are not effective for use below 40F and most of our population has traditionally been in the north where that's simply not good enough. On land, it also relies on subsurface water or access to drilling the heat exchange wells, again simply not available in population centers.

But if you are talking about heat pumps, and TRANSFERRING heat from the sea water to the (someplace?) in the boat...that's different, sure you can transfer more heated medium than the energy going into operating the pump.

At which point, I admit I have totally no idea why you would mix heat pump efficiency with heat transfer. Or, why you would be pumping heat from the ocean into a boat in order to cool the air in it. I would think you'd be transferring heat INTO the ocean in order to cool the boat, and using the ocean as a heat sink. Which still has nothing (that I can see) to do with pump efficiency. Regardless of the system you use, water cooled beats air cooled. And creates the problems of corrosion and contamination, requiring monel plumbing and other considerations.
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Old 30-11-2007, 19:39   #43
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I would consider this.

1) get your energy use down to an absolute minimum. Create a sleeping box (casket?) with 2" rigid foam. Preferably coat it with reflective foil (aluminium foil or buy rigid foam with it already on it). Or perhaps your hull has a partially enclosed berth already and just needs spray in foam and a hard foam door.

2) take apart a 12V refrigerator and use the parts as an air conditioner. Sea water cooling is preferred for the condenser.

3) use your generator during the day to charge a 12V battery. Add a wind generator for additional power.


If that's not radical enough, then I'd try this:

Make a water bed. Use an air mattress and run sea water through it. Put a blanket over you (in this case, the blanket is keeping you cool). Only energy cost is a small water pump. Deflate the water bed when weight is an issue. I have never been too hot in the water and this comes close to that.
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Old 30-11-2007, 20:03   #44
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On the foil note, I'm surprised I haven't seen shiny boats. Even white fibreglass absorbs most infrared heat.

There is a process "arc spray metalizing" where a very thin coat of aluminium can be put on fibreglass. Put a clear coat paint over it to keep it shiny and you have a low heat gain boat. Cool in both senses of the word.
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Old 30-11-2007, 20:07   #45
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I'm not trying to throw a monkey wrench into the works here but I was just curious why you want to use a gas engine.

I bought a Kubota 2 cyl diesel engine as an aux. I had a 150A alternator, fridge compressor (car A/C compressor) and dive compressor hookd up to it.
Kubota Engine America - Compact Diesel Engines
It doesn't take up much more room than that Honda and it uses about 8 oz of diesel an hour, it's sea water cooled. It's also 13hp.

I ran that thing 2 hours a day for 10 years. Had to replace 1 water pump impeller and have the injector serviced once.

I think they make a 1 cyl, 9hp model also.
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