Refrigeration - Evaporator vs. Holding Plate

[OzePete]

Richards QUOTE:
Pete's marketing chart and page 30 chart was unfair marketing in my opinion. If you really want an independent test Sales personal should not be involved in or during the test. If testing different types of evaporator, and yes eutectic plates are evaporators, they both must be sized to except the condensing unit,s Btu output.[/QUOTE]

Again your comment is wrong and in this case also personally insulting.
I am a refrigeration engineer and only I and other qualified refrigeration persons were involved in the two month test / trial quoted in the 'Commercial Posts'
BTW, you must have missed the point in that post that we manufacture both system types!

Now I know it must be annoying when someone posts solid data that contradicts what some have been wrongly preaching but as I invited several times previously, please provide your alternate data along with application notes, pictures, a chart and simple 1 to 9 points like I did, that most can understand. Check original post of trial data here: http://www.cruisersforum.com/forums/...se-200041.html

To simply contradict such an extensive trial with only conjecture and without fact, does nothing but confuse those seeking information.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

[OzePete]

Originally Posted by hellosailor

Pete-
Although I'd expect the comparative efficiency of any two systems to remain the same, won't the actual measured efficiency (and therefore COP) vary according to the ambient temperature around the evaporator? Leaving a gap where one manufacturer may rate their system at 20C while another rates it at 25C, etc?

Hi HS, sorry for delay in responding, appreciate your input to the discussion.
You are correct.

Variations of ambient will alter COP somewhat but both systems in our trial were in near identical environments so that is not an issue. The higher the ambient beyond engineered value, the poorer the COP and that is why we advocate fresh water cooling assist for systems operating in the tropics where high side system pressures will exceed 200PSIG if air cooled only.

The 2 month trial mentioned in this thread, http://www.cruisersforum.com/forums/...se-200041.html was conducted in the one cabinet, each system run in 10 day consecutive periods in near identical day / night temperatures and each with identical condensing units which have their high side temperature controlled to between 38C and 43C.
I doubt there is a more fairer way of conducting such a test and reporting it clearly for all to understand, as we did in this report.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

[SV THIRD DAY]

Originally Posted by a64pilot

It just seems illogical to me that cold plates are not used way more often in refrigeration if they are so much more efficient.
Can’t you see the advertising, “Our refrigerator uses 50% less power than brand X”
I think if true then it would sell a LOT of house refrigerators and more than cover the cost of holding plates.
Plus you get to advertise how much better your technology is than everybody else’s if true.

Two answers to that question:
1. Can you auto-defrost a hold over plate? No not easily.
and
2. The manufacturers are not paying the utility bill, so there isn't an incentive since as long as they meet the "government standards" that's good enough.

[SV THIRD DAY]

Originally Posted by kmacdonald

The answer is obvious. Cold plate refrigeration is not more efficient. .

Completely wrong statement that the side by side data presenting in this and other threads proves to be the case.

But hey...its the internet and anyone is an expert....right....

[SV THIRD DAY]

Originally Posted by a64pilot

For the nay sayers.
He explained, logically the reason for the difference in efficiency in his test.
If we continue to treat manufacturers who share their test data like this, don’t be surprised when you don’t see any more test data.

It why I don't anymore Amigo...
Because people (despite what they say) really are not looking to learn, they are looking to validate what they already think. So I don't mess with it anymore. The truth and data is out there, but if people want to call those companies LIARS who have been in business for 50Years....fine....why do I care what they think anyway, I can't keep up with orders as it is!

[transmitterdan]

If we stipulate that a holding plate system and an evaporator plate system are to hold identical boxes at exactly the same time at the exact same product temperature then it would seem not possible for the holding plate version to consume less watt-hours. Why? The holding system has to reduce the refrigerant to a much lower temperature to freeze the solution. The amount of energy consumed by a refer is a function of heat transfer and the delta T that the refrigerant must achieve to effect that transfer. The amount of heat (Q) transferred in such a test is determined by the box temp, insulation and the external environment not the type of evaporator. So how can one system remove the same Q with a higher delta T and be more efficient? Whatever does that can be also done to the evaporator and make it more efficient too. The evaporator will always win on total energy consumption if the test is designed properly.

Holding plate systems can reduce the need to self generate energy if solar is available. But the total electrical watt-hours consumed by the holding system must always be higher unless the evap system has a flaw.

[a64pilot]

Originally Posted by transmitterdan

If we stipulate that a holding plate system and an evaporator plate system are to hold identical boxes at exactly the same time at the exact same product temperature then it would seem not possible for the holding plate version to consume less watt-hours. Why? The holding system has to reduce the refrigerant to a much lower temperature to freeze the solution. The amount of energy consumed by a refer is a function of heat transfer and the delta T that the refrigerant must achieve to effect that transfer. The amount of heat (Q) transferred in such a test is determined by the box temp, insulation and the external environment not the type of evaporator. So how can one system remove the same Q with a higher delta T and be more efficient? Whatever does that can be also done to the evaporator and make it more efficient too. The evaporator will always win on total energy consumption if the test is designed properly.

Holding plate systems can reduce the need to self generate energy if solar is available. But the total electrical watt-hours consumed by the holding system must always be higher unless the evap system has a flaw.

I think you may have it backwards.
Depending on size of the evaporator the thin plate may have to be much colder to keep the box cold, colder refrigerant temps make the compressor much less efficient of course. No free lunch.
It is really, really tough to make a test be dead equal.
In Pete’s case I believe what was done was he was comparing two products they manufacture, and doing so honestly.

However as with most tests, I believe all that can be certainly determined is that with Pete’s equipment, the cold plate is more efficient.

Although as I keep trying to point out, there is more to the story.
To quote Paul Harvey, the rest of the story, and in my opinion, the most important part is the ability of the hold over plate to absorb “excess” power to be released when there is a shortage of power.

If you have a thin plate evaporator, you can do similar by adding in another battery or tow to the bank

[OzePete]

Originally Posted by transmitterdan

If we stipulate that a holding plate system and an evaporator plate system are to hold identical boxes at exactly the same time at the exact same product temperature then it would seem not possible for the holding plate version to consume less watt-hours. Why? The holding system has to reduce the refrigerant to a much lower temperature to freeze the solution. The amount of energy consumed by a refer is a function of heat transfer and the delta T that the refrigerant must achieve to effect that transfer. The amount of heat (Q) transferred in such a test is determined by the box temp, insulation and the external environment not the type of evaporator. So how can one system remove the same Q with a higher delta T and be more efficient? Whatever does that can be also done to the evaporator and make it more efficient too. The evaporator will always win on total energy consumption if the test is designed properly.

Holding plate systems can reduce the need to self generate energy if solar is available. But the total electrical watt-hours consumed by the holding system must always be higher unless the evap system has a flaw.

I suggest you study the report at http://www.cruisersforum.com/forums/...se-200041.html and particularly note the effect that a lower COP and excessive start ups have on power consumption. Also you might like to discuss the points numbered 1 to 9 raised to support the findings. You could also describe how the process presented is wrong and display your trials / data that supports your criticism.

Cheers OzePete

[OzePete]

Originally Posted by a64pilot

I think you may have it backwards.
Depending on size of the evaporator the thin plate may have to be much colder to keep the box cold, colder refrigerant temps make the compressor much less efficient of course. No free lunch. Exactly and as described in the test notes the cyclic plate ONLY refrigerates while the compressor is running and therefore operates at a much lower temperature and therefore lower COP
It is really, really tough to make a test be dead equal. Agree, but we applied each system to single cabinet controlled by the one digital controller and driven by identical condensing units with condenser temperature control, so how much fairer could such a test be?
In Pete’s case I believe what was done was he was comparing two products they manufacture, and doing so honestly. Exactly and we do manufacture both types

However as with most tests, I believe all that can be certainly determined is that with Pete’s equipment, the cold plate is more efficient. Not just my tests but tests from Rich and others, but the best test is the users and they report greater power efficiencies with eutectic systems in near all cases

Although as I keep trying to point out, there is more to the story.
To quote Paul Harvey, the rest of the story, and in my opinion, the most important part is the ability of the hold over plate to absorb “excess” power to be released when there is a shortage of power.

If you have a thin plate evaporator, you can do similar by adding in another battery or tow to the bank. There are several easy ways to improve the efficiency of those thin aluminium cyclic systems, but that's another thread!

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

[SV THIRD DAY]

Pete.....
As it always happens.
Data doesn't matter when people won't want to believe it.

[a64pilot]

Originally Posted by SV THIRD DAY

Two answers to that question:

1. Can you auto-defrost a hold over plate? No not easily.

and

2. The manufacturers are not paying the utility bill, so there isn't an incentive since as long as they meet the "government standards" that's good enough.

In truth, I think the evaporator on a modern house fridge is I think behind a heated plastic wall, I know the exterior is often heated as is I think the door seals.
You could put a cold plate behind the same heated plastic wall.
As far as not being efficient, now that I am in a big city for awhile, the Earth loving types seem to be everywhere, you know have to buy organic everything and whatever the heck gluten is, it must be toxic.
I have never seen as many Tesla’s as I have here etc.
Seems theses not poor lovers of the Earth would buy something that is advertised to be earth friendly, saving the ozone layer, low carbon emissions etc.
You know these people actually believe an electric car causes zero emissions?

[OzePete]

Originally Posted by SV THIRD DAY

Pete.....
As it always happens.
Data doesn't matter when people won't want to believe it.

You sure have got that right Rich... Geeeez.. And I thought my wifey was a bit hard headed!
It sure does create a reaction when we dare to let facts and indisputable data spoil the fake religion of some..

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

[a64pilot]

I have a related question.
How do these multi speed compressors “know” when to run on high, or low speed.
I know by changing the resistance on the thermostat line you can make it run on low, but it seems from watching the amp meter that mine runs on low speed almost always once it hits equilibrium, so how does it know to do that?

The difference in current draw is quite dramatic, only time I see it drawing very high current is if it’s been off for quite awhile and the cold plates are at room temp, then it draws a lot, but by the next day it’s drawing 1/3 the current or seems to.

[OzePete]

Originally Posted by a64pilot

In truth, I think the evaporator on a modern house fridge is I think behind a heated plastic wall, I know the exterior is often heated as is I think the door seals.
You could put a cold plate behind the same heated plastic wall.
As far as not being efficient, now that I am in a big city for awhile, the Earth loving types seem to be everywhere, you know have to buy organic everything and whatever the heck gluten is, it must be toxic.
I have never seen as many Tesla’s as I have here etc.
Seems theses not poor lovers of the Earth would buy something that is advertised to be earth friendly, saving the ozone layer, low carbon emissions etc.
You know these people actually believe an electric car causes zero emissions?

Spot on.. Many modern refrigerators use as much or more energy via heaters than they do via the compressor. They are stacked with all sorts of devices like mullion heaters (usually several), defrost heaters, defrost water tray heater, butter compartment heaters etc etc. They are what the punter wants (wanted) and power consumption was not an issue, having the latest device was more important.

Cheers OzePete

[a64pilot]

You know I guess your right, cause what these city dwellers seem to want is the huge sub zero “commercial” separate fridge and freezer.
This for a couple that usually eats out anyway, they are a status symbol, as is the Tesla.
If you look at the average US house size size WWII, it’s astonishing, that coupled with the decrease in size of the average family has You wondering what’s the logic?