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Old 25-05-2018, 00:14   #1
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Warm water free from fridge unit

A client who often comes up with some great ideas, explained this one recently. He doesn't have a water heater on board and was getting to dislike cold showers, so he did a bit of plumbing and came up with this simple solution:
His Ozefridge AW480 refrigeration unit has an inbuilt a water heat exchanger to assist the condenser cooling process. The unit powers a micro pump once the condenser reaches 43C (and off when it reduces to 38C)

Now Bryan realised that by recycling this warmed water via a small insulated container he could enjoy a warm (not hot) shower and it costs nothing to run...
Water stays at around 39C.

Click image for larger version

Name:	<a title=Shower warmer.png Views: 200 Size: 181.4 KB ID: 170463" style="margin: 2px" />

Cheers OzePete and thanks Bryan
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Old 25-05-2018, 04:54   #2
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Re: Warm water free from fridge unit

That's a pretty clever solution.
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Old 25-05-2018, 09:01   #3
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Warm water free from fridge unit

Your not going to get much heat from an average Marine refrigeration system. The average system pulls about 60 W when operating.
Average Human radiates about 100W.
But every bit helps, just donít expect much.

I believe there are systems that use the boats fresh water system to cool their condensers or augment cooling anyway.
The heat gain is so small that thankfully they donít have to drink tepid water, I believe the tank loses the heat about as fast as itís added.
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Old 25-05-2018, 17:27   #4
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Re: Warm water free from fridge unit

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Originally Posted by a64pilot View Post
Your not going to get much heat from an average Marine refrigeration system. The average system pulls about 60 W when operating.
Average Human radiates about 100W.
But every bit helps, just donít expect much.

I believe there are systems that use the boats fresh water system to cool their condensers or augment cooling anyway.
The heat gain is so small that thankfully they donít have to drink tepid water, I believe the tank loses the heat about as fast as itís added.


Using energy which would otherwise be wasted is a great ecological practice.
In buildings we manage the potable water delivered from reverse osmosis process commercial plants is 40c. In summer with roof top tanks this water can reach 50c. So we circulate the water through a heat exchange using exhausting chilled water from the HVAC system. The potable water is then delivered to the building occupiers at 26c. Pleasantly cool!

What is described above is similar. The ambient temp and the rate of flow of the small energy source will limit the effective result. But if it works where you live then great. Running main engine raw water coolant (sea water) through a heat exchange - something most marine hot water heaters provide for - will have a better effect as there is more flow and the temperature of the exhausting water is much higher.
My boat has taught me so much about energy conservation. It's where I experiment. I use lessons learnt in tall buildings saving hundreds of thousands of dollars.
Understanding of battery charging and balancing transfers to battery bank management for firefighting emergency systems. The use of colour changing LEDs results in day /night lighting throughout the boat using the same light source. We get some funky party lighting also. Energy management of lighting of electronics like radar the turn off / turn on of same verses putting parts of the system to sleep saves significant energy. The use of waste water to heat is significant in certain ambient conditions. The use of variable frequency drives on pumps. The list goes on.
Saving milliamperes on the boat and converting the same principals to kilowatts in buildings I find most rewarding.
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Old 25-05-2018, 18:48   #5
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Re: Warm water free from fridge unit

If I remember right, water-cooled cooling systems lose their ability to cool when the recirc water gets somewhere around 35C. It would be interesting to do the math on whether it would use less energy to warm the water directly rather than run the circ pump. I also wonder if the fridge evaporative cooling system might have a heavier load because of the warm water?
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Old 26-05-2018, 05:53   #6
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Re: Warm water free from fridge unit

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If I remember right, water-cooled cooling systems lose their ability to cool when the recirc water gets somewhere around 35C.
No not correct Musky, A refrigeration system is ( or should be!) engineered to operate within an optimum condensing temperature /Pressure range to suit the application. Our Ozefridge systems are engineered to be most efficient with a condenser temperature between 38C & 43C. This is why our systems both air cooled only and air / water cooled have temperature controlled condensing. Without maintaining condensing within engineered parameters efficiency will decrease with a temperature rise but not cease.

It would be interesting to do the math on whether it would use less energy to warm the water directly rather than run the circ pump. Our sealed magnetic drive centrifugal micro circulation pump uses less than 3 watts (1/4 amp) and is used to store heat otherwise wasted... hard to be more frugal than that!

I also wonder if the fridge evaporative cooling system might have a heavier load because of the warm water No, as previous stated, the system is engineered to be optimum within the temperature parameters described?
Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems
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Old 26-05-2018, 08:48   #7
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Re: Warm water free from fridge unit

That's interesting, thank you for sharing!
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Old 26-05-2018, 10:51   #8
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Re: Warm water free from fridge unit

"cool" idea

but better be careful, if the water in the tank does not reach 60įC on a regular basis, sooner or later there will be an issue with Legionella ==> no fun
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Old 26-05-2018, 12:18   #9
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Re: Warm water free from fridge unit

Another way to capture "wasted" heat would be gluing copper or aluminum tubes to the underside of photovoltaic panels and running water through those with a micro pump. Since the best photovoltaics are about 20% efficient then 80% of what the are capturing becomes heat. So for every 100watt panel one could get a good part of 400watts of heat! Quite a bit more than the fridge waste heat. And in addition the efficiency of the photovoltaic panel would increase some Has any one tried this?
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Old 26-05-2018, 14:06   #10
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Re: Warm water free from fridge unit

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Another way to capture "wasted" heat would be gluing copper or aluminum tubes to the underside of photovoltaic panels and running water through those with a micro pump. Since the best photovoltaics are about 20% efficient then 80% of what the are capturing becomes heat. So for every 100watt panel one could get a good part of 400watts of heat! Quite a bit more than the fridge waste heat. And in addition the efficiency of the photovoltaic panel would increase some Has any one tried this?


I have not heard of it being done, itís talked about every so often, but I donít think anyone has done it.
Iíve only heard it being discussed as a way to increase panel efficiency, not harness waste heat. However as I look at just how much surface area I have in 1000 W of panels, I think surely there is a lot of heat absorbed by those dark panels.
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Old 29-05-2018, 11:08   #11
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Re: Warm water free from fridge unit

Quote:
Originally Posted by a64pilot View Post
Your not going to get much heat from an average Marine refrigeration system. The average system pulls about 60 W when operating.
Average Human radiates about 100W.
But every bit helps, just donít expect much.

I believe there are systems that use the boats fresh water system to cool their condensers or augment cooling anyway.
The heat gain is so small that thankfully they donít have to drink tepid water, I believe the tank loses the heat about as fast as itís added.

Exactly 39 įC = 102.2 įF
If the ďwarmĒ water reservoir is insulated, thatís not cold water , warm water shower as opposed to cold water shower? Gets my thumbs up !😎👍🏼
Iím collectin evap coils from shitcanned a/c units to use under solar panels to collect wasted heat . Will run this experiment by pumping with aquarium pump the a/c condensed water collected. In the reverse of the a/c process.
Iíve used old a/c evap coils for automatic transmission coolers, works great.
Just think out of the sandbox .....
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Old 29-05-2018, 11:31   #12
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Re: Warm water free from fridge unit

A friend of mine built a heat exchanger for the exhaust heat of a gas driven fridge. He said it works well, because the flame on the fridge burns most of the time.
The fridge is on a trimaran, so no issues with excess heeling.
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