Refrigeration - Evaporator vs. Holding Plate

[Typhoon]

After this falls boat show in Annapolis we will be doing a direct head to head accredited test by the SCC https://www.scc.ca/ with one of our systems against a popular keel cooled system .

Same box , same temperatures, water temperature will be held at 82F for the keel cooled test . We have been very busy lately but getting this Accreditation done is high on our list to do .

Also finishing up a better way of ascertaining clients current state of insulation. This will vastly improve results .

Regards John

[john61ct]

Eutectic plate design is not in and of itself more efficient, unless the overall system design features a source of "free" surplus power at least a few times a week.

In effect the "energy stored as cold" is like a specialized expansion of the House battery bank.

There certainly overall fridge system features that make Ozefridge and others' holding plate designs more efficient than lesser vendors, but that is also part of what makes them more costly.

wrt efficiency, nothing is more critical than the box's insulation

[OzePete]

Originally Posted by ColdEh Marine

Yes well put . Pete

Could you share with us your data , including ..

- box size
- R value of box
- average ambient
temperature
- box temperature range
- and of course AHs used
In 24 hrs

Regards John

Thanks John, What I was indicating are factors that determine power consumption / efficiency. Given a cabinet of whatever size, R factor, desired temperature etc., these factors will still apply specially the COP.
Regards specific testing we use a common 150 Lt domestic freezer with 70mm of urethane insulation for tests, (Approx R15). We remove the original 240VAC system then add two identical 12VDC condensing units, one coupled to a thin aluminium cyclic plate and the other to our mid range eutectic plate. These are separate air / water cooled systems but operating on air only. We run them one at a time each alternating one week on, one week off so there is equal work for each type of system while maintaining the cabinet at +2C to +4C. Each system is identically powered and data logged. This data includes total power consumed. Here are some pictures of an alum plate / eutectic plate comparison test.
Cheers,
OzePete ozefridge

[Bleemus]

As I suspected. Thanks Pete.

[poiu]

There is another big factor in the efficiency of cooling and that is coolant temperatures. The higher the temp the compressor can run at, the less power it will use. Modern high end domestic fridges seem to achieve this with enormous evaporators and I presume that is why they use less power, maybe half the power of marine fridges.

[OzePete]

Originally Posted by OzePete

Thanks John, What I was indicating are factors that determine power consumption / efficiency. Given a cabinet of whatever size, R factor, desired temperature etc., these factors will still apply specially the COP.
Regards specific testing we use a common 150 Lt domestic freezer with 70mm of urethane insulation for tests, (Approx R15). We remove the original 240VAC system then add two identical 12VDC condensing units, one coupled to a thin aluminium cyclic plate and the other to our mid range eutectic plate. These are separate air / water cooled systems but operating on air only. We run them one at a time each alternating one week on, one week off so there is equal work for each type of system while maintaining the cabinet at +2C to +4C. Each system is identically powered and data logged. This data includes total power consumed. Here are some pictures of an alum plate / eutectic plate comparison test.
Cheers,
OzePete ozefridge

Hi John, This trial has been completed and the results even surprised us.
Here is a chart indicating the power consumption of each type of system providing the same refrigeration outcome. (A full report is at my thread in the 'Commercial Posts' section)


Cheers OzePete

[SV THIRD DAY]

Originally Posted by OzePete

Hi John, This trial has been completed and the results even surprised us.
Here is a chart indicating the power consumption of each type of system providing the same refrigeration outcome. (A full report is at my thread in the 'Commercial Posts' section)
Attachment 168302

Cheers OzePete

In a way it's funny....
We have been telling folks this for 50 Years...yep Technautics is has been in the Marine Refrigeration business for 50 years now... but there's this false assumption out there that newer is better. And by newer I'm referring to the thin rolled evaporator capillary tube systems. When in truth they're just easier to mass-produce in China, so I guess that makes them better in terms of having a lower price and larger profit margin for the companies that sell them.

But this data confirms what we've known all along when it comes to power usage the most efficient system is a eutectic based holding plate system. How many Marine businesses have been around for 50 years that's not an accident there's a reason....

[Exile]

For those of us non-techy types out here in the cheap seats . . . kindly correct where I'm wrong (easy) or confirm where I'm right (rare). May just be a vocabulary problem on my part (bolded below).

I'm considering adding a 12v BD system but my only experience thus far is on my own boat which has a 12v engine drive compressor and a separate 110v "Shore Assist" unit. Both systems (Seafrost) use the same holding plates, with separate lines going into each, which I believe are eutectic plates which freeze the antifreeze type fluid therein for a period of time to keep the beer & Rich's ice cream cold. This is in contrast to evaporator-type plates which are the type found in common land-based ref rig units, and require a compressor which continuously cycles on & off to keep such items cold. How am I doing with the basic vocabulary so far?

For years Cleave at Seafrost has been telling me that using my generator and 110v system to cool the fridge is less efficient than running my engine for the 40 mins. or so it takes to freeze my holding plates off the main engine. This is because it takes 2-3 hours of generator run time @0.5g/hr. to freeze the plates off my 110v system vs. the 40m or so of engine time @1g+/hr to freeze them off the engine. So apparently "Shore Assist" is an apt name for my 110v system, since it's holding plate system works best if run on a continuous cycle 110v system that only shore power can provide (unless you like to run your genset all day). Still with me?

This is where a 12v BD system from either Rich (CoolBlue) or Cleave (Seafrost) potentially comes in. I'm generally loathe to run the main engine on passage and have plenty of battery capacity, so running a continuous cycle 12v system w/o having to use the engine or genset is appealing. I realize however, that absent solar/wind/hydro this will shorten the interval for relying on diesel to charge my batteries. So then the question comes down to whether I can tap into my existing holding plates to run the BD system (as Rich says will work I think) or add separate eutectic plates just for that system (as Seafrost strongly advises).

Big difference in cost & installation time so this inquiring (but limited) mind would like to know . . . .

[SV THIRD DAY]

We do 4-5 of what I call holding plate recycle projects a month. This involves reusing holding plates that are currently connected to either an engine driven system or a hundred and twenty volt system and converting those with a 12-volt compressor. There are some internet chat room experts it'll tell you went won't work it won't be as efficient so long ago I've stopped arguing let them believe what they want and continue to have more work doing these than we can almost keep up with. The holding play just doesn't care if it's being frozen by a engine driven 120 volt or 12 volt compressor. Is the heat transfer between the copper tubes and the eutectic solution better or worse with a higher or lower BTU compressor sure there's differences but at the end of the day it really doesn't matter. We've do enough of these to know that a holding plate conversion is going to cost somewhere between 2000 and $2,500 based exactly on what components you need.

cheers

[Richard Kollmann]

My advice is to contact John at Cold Ed marine and ask him about a 12 volt kit to adapt his condensing unit to replace the 115 volt AC compressor. As long as the Seafrost plate coil for the AC unit is 3/8 outside diameter or smaller any condensing unit with a Danfoss BD compressor will work as long as the refrigerant low pressure control valve is replaced with a Cap tube or TXV and receiver.

Unless you have a small well insulated box keeping the Seafrost engine drive and changing AC compressor to 12 volt is a smart move as 12 volt refrigeration alone is not truly as efficient as the engine driven Seafrost unit.

[Richard Kollmann]

Rich you and John should not get excited over Pete’s thirty day comparison of standard evaporator against a eutectic plate. The wide difference in watts consumed should tell you it is not a true comparison. If the difference was 6% to 10% and holding plate system had a TXV flow control this test could be a fare comparison. Facts that are missing are:
• When systems were operated separately were they started at ambient temperatures?
• Was it confirmed that Aluminum evaporator’s size and Btu capacity was equal to condensing unit’s Btu output. Overpowering evaporator with excessive flow wastes systems energy efficiency.
• An efficient 12 volt system with proper size standard evaporator will cycle off and on 1.5 times per hour when system is in balance.
• What good is a chart that only show Watts of power consumed and not compressor cycle times. Unnecessary cycling wastes daily energy.
• Anyone seeing an unused holding plate probable full of solution in the same test box as the aluminum evaporator must know this would count for a major test error in watts consumed. I have a 24 cu ft Samsung refrigerator with eutectic plates that are not connected to refrigerant lines relying on evaporator in back of box to keep these plates cold.

[missourisailor]

As I said on the other thread, I find it interesting that as the test progressed from one stage to the other, the average power usage kept going up.
Pete basically said that this was from the room heating up.

I interpreted this as meaning that the condenser was heating up due to warmer air flowing across it.
Which is exactly how I would expect a cap system to operate.

I would be most interested in seeing the same test with an expansion valve in at least one of the systems.
I would bet that the average power usage would be more consistent as the condenser's cooling air heated up.

But even with the faults of the test that Richard has pointed out, I think it still shows that holding plates are more "power" efficient over thin plate systems.

[Exile]

Originally Posted by Richard Kollmann

My advice is to contact John at Cold Ed marine and ask him about a 12 volt kit to adapt his condensing unit to replace the 115 volt AC compressor. As long as the Seafrost plate coil for the AC unit is 3/8 outside diameter or smaller any condensing unit with a Danfoss BD compressor will work as long as the refrigerant low pressure control valve is replaced with a Cap tube or TXV and receiver.

Unless you have a small well insulated box keeping the Seafrost engine drive and changing AC compressor to 12 volt is a smart move as 12 volt refrigeration alone is not truly as efficient as the engine driven Seafrost unit.

Swapping my 110v compressor for 12v, along with keeping my engine driven Seafrost, is probably the easiest & most cost-effective way to go. Especially since all my lines were likely installed when the boat was built and would be difficult to replace (or re-route). As I recall, Rich made this work for forum member a64.

My only question now is whether to ditch the 110v system which has proven itself very reliable over many years, albeit with limited usefulness on passage.

[Richard Kollmann]

Exile, I forgot to ask what size 115 volt SeaFrost compressor do you have they sold both a large 1/2 Horse power and a 1/6 HP compressor. Both were air cooled but the large one sometimes had a water tank attached to it and a water pump.

When I was still in the business I sold a few kits to make this conversion with new condensing units and capillary tube to replace Seafrost low pressure regulator valve. I charged $375 for the kit and serviced it when it was installed by owner.

[OzePete]

Originally Posted by Exile

For those of us non-techy types out here in the cheap seats . . . kindly correct where I'm wrong (easy) or confirm where I'm right (rare). May just be a vocabulary problem on my part (bolded below).

I'm considering adding a 12v BD system but my only experience thus far is on my own boat which has a 12v engine drive compressor and a separate 110v "Shore Assist" unit. Both systems (Seafrost) use the same holding plates, with separate lines going into each, which I believe are eutectic plates which freeze the antifreeze type fluid therein for a period of time to keep the beer & Rich's ice cream cold. This is in contrast to evaporator-type plates which are the type found in common land-based ref rig units, and require a compressor which continuously cycles on & off to keep such items cold. How am I doing with the basic vocabulary so far?[B]You are doing very well so far. If anyone needs to confirm if their 'holding plates' are eutectic, simply open the tanks filler cap and see if the 'eutectic' solution is frozen when the system finishes a refrigeration cycle (stops) then check again to see if it has thawed when it starts again. The process should be = Once frozen the unit stops, once thawed to liquid / slurry the unit starts again. This process is called 'Phase Change' [/B]

For years Cleave at Seafrost has been telling me that using my generator and 110v system to cool the fridge is less efficient than running my engine for the 40 mins. or so it takes to freeze my holding plates off the main engine. This is because it takes 2-3 hours of generator run time @0.5g/hr. to freeze the plates off my 110v system vs. the 40m or so of engine time @1g+/hr to freeze them off the engine. So apparently "Shore Assist" is an apt name for my 110v system, since it's holding plate system works best if run on a continuous cycle 110v system that only shore power can provide (unless you like to run your genset all day). Still with me?

This is where a 12v BD system from either Rich (CoolBlue) or Cleave (Seafrost) potentially comes in. I'm generally loathe to run the main engine on passage and have plenty of battery capacity, so running a continuous cycle 12v system w/o having to use the engine or genset is appealing. I realize however, that absent solar/wind/hydro this will shorten the interval for relying on diesel to charge my batteries. So then the question comes down to whether I can tap into my existing holding plates to run the BD system (as Rich says will work I think) or add separate eutectic plates just for that system (as Seafrost strongly advises). Rich SV Third Day, is an experienced hands on man and best to seek his advice on this one.

Big difference in cost & installation time so this inquiring (but limited) mind would like to know . . . .

Cheers OzePete ozefridge@ozemail.com.au