Fridge that uses little, if any, of your battery!

[Richard Kollmann]

Have you ever noticed that when lower than normal refrigerator amp/hrs are concerned there is no reference to desired sustained temperature inside that refrigerated area. I would think it is more important to know temperature in areas of box rather than evaporator temperature, say 40 to 60 degrees drink cooler, 33 to 36 degrees refrigeration temperatures , 10 to 22 degrees for short term freezer and below zero degrees F for a one month to six month storage.

[OzeLouie]

Originally Posted by Richard Kollmann

Have you ever noticed that when lower than normal refrigerator amp/hrs are concerned there is no reference to desired sustained temperature inside that refrigerated area. I would think it is more important to know temperature in areas of box rather than evaporator temperature, say 40 to 60 degrees drink cooler, 33 to 36 degrees refrigeration temperatures , 10 to 22 degrees for short term freezer and below zero degrees F for a one month to six month storage.

Have you ever noticed that when some want to discredit another they will make incorrect quotes without any data or reference to fact:

Richard, read the OP which clearly states the cabinet operating between +2 & +5C as does the spread sheet estimator.

[StuM]

Originally Posted by RaymondR

I notice the metric performance specs for the Danfoss BD series of refrigeration compressors are quoted in "Watts" with no indicator of a time period. The specs from a US Danfoss site uses "BTU" and again no mention of a time period. One can only assume that they mean "Watts/hr" and BTU/hr". I had similar problems with TXV specs.

One shouldn't assume that.

Watts is the correct metric for the energy requirements and cooling capacity of a compressor. There is no meaningful unit of "Watts/hr".


You are however correct in that it should be BTU/hr (or BTUH) not BTU.
(1 BTU/hr or BTUH = 0.3W)
(As I mentioned earlier, this is a very common misuse which is even made by many manufacturers in their advertising - see how many aircons are sold as 2000 BTU units etc)

[RaymondR]

Originally Posted by Off Trail

Watts sounds right in this case since it's the rate at which it can transfer energy while running.

Pretty well all disciplines have their "shorthands" which are used and understood perfectly between regular practitioners.

[OzeLouie]

Originally Posted by Uncle Bob

Louie, I wouldn't get too worked up about the nay Sayers that are here, most if not all have never encountered your product yet feel that they are able to denigrate it based on, of all things the units used to describe its performance, and ,laughingly the suggestion that the holding plate system is so yesteryear and simply doesn't work with a 12 volt system, regardless of the many happy clients that are happy to attest to its actual performance. I guess that you are not alone, Rich Boren also produces a similar holding plate system that receives good reviews, yet Richard continues to insist that the holding plate is incapable of performing with a 12 volt compressor, that it needs to cycle many times a day contrary to reviews posted here.
Keep up the development and I wish you well.
Cheers Bob.

Thanks Bob, very true. This thread has had approx. 1000 views per day and I am sure most were attracted to the theme regards running a fridge with little or no battery involvement and not to be subjected to the ongoing 'what's watt, what's not or whatever' stuff! I had earlier acknowledged my OP error and had hoped we could get back to what this is all about.
And as Raymond (P116) indicated I am no orphan with Watts quoted widely in reference to Watts/Hr in many metric refrigeration publications so perhaps I can expect some company back here in 'the naughty corner'
As for the anti eutectic brigade, there are many thousands of eutectic users out there who know better and comments from those who don't know yet refuse to understand the basic fundamentals, don't faze me.

[Richard Kollmann]

Originally Posted by OzeLouie

Have you ever noticed that when some want to discredit another they will make incorrect quotes without any data or reference to fact:

Richard, read the OP which clearly states the cabinet operating between +2 & +5C as does the spread sheet estimator.

I did read and forgot refrigeration mean's
different things to different people 2 to 5 degrees C box temperature is a good cooler but without ice production or ability to extend sensitive food's useful life. What other facts are you looking for?

[RaymondR]

Originally Posted by StuM

One shouldn't assume that.

Watts is the correct metric for the energy requirements and cooling capacity of a compressor. There is no meaningful unit of "Watts/hr".


You are however correct in that it should be BTU/hr (or BTUH) not BTU.
(1 BTU/hr or BTUH = 0.3W)
(As I mentioned earlier, this is a very common misuse which is even made by many manufacturers in their advertising - see how many aircons are sold as 2000 BTU units etc)

The very raison d'être for the SI system is that practitioners of science and the derived sciences are able to express themselves in a manner readily understandable without confusion. Hopefully all these "shorthands" will eventually fall into disuse and correct the situations you identify.

In my professional life in the oilfields I was cursed by the multiplicity of systems in use. I recall one incident where a fairly large welded structure would not fit into it's intended home. I measured and remeasured the structure with their tapes and found it complied with the drawings then checked the installation and was baffled as to why it did not fit. Eventually one of the Danes pointed out that there is a Danish foot which is slightly different from the imperial foot.

[StuM]

Originally Posted by RaymondR

Pretty well all disciplines have their "shorthands" which are used and understood perfectly between regular practitioners.

Maybe, but using that "shorthand" when addressing a wide audience of non-"regular practioners" is ill-considered* to say the least.

*I'm being very polite for me!

[StuM]

Originally Posted by OzeLouie

T
And as Raymond (P116) indicated I am no orphan with Watts quoted widely in reference to Watt/Hr in many metric refrigeration publications so perhaps I can expect some company back here in 'the naughty corner'

Sigh!
As pointed out, Raymond was incorrect - as any competent engineer would realise. The Watts he quoted in his reference was correct; and no reputable publication would use the meaningless Watt/Hr.
You however have consistently misused these units.
You apparently still don't "get it"

[StuM]

Originally Posted by RaymondR

Eventually one of the Danes pointed out that there is a Danish foot which is slightly different from the imperial foot.

And best not mention the Scandinavian Mile
https://en.wikipedia.org/wiki/Scandinavian_mile

[Stu Jackson]

A perfect summary.


I'm an engineer and using incorrect units is like fingernails on a blackboard to me and seriously detracts from whatever marketing might be happening. SERIOUSLY detracts, like in "Why should I believe anything this guys says if he can't get his units straight?"

Originally Posted by Dockhead

I would politely suggest that the OP should keep his units straight. Sure, it's a common mistake, and not a death penalty case. But as Stu and others have pointed out, it makes a really bad impression coming from a pro in a technical field who is trying to make convincing technical points. By "really bad impression", I mean an impression that even really basic engineering concepts are not mastered, stuff that anyone with even a semester of engineering training could never mess up. I think it really detracts from otherwise really good points. I do agree with Off Trail that some good technical stuff has come out of this thread despite the kerfuffle about units.

Originally Posted by OzeLouie

Thanks Bob, very true. This thread has had approx. 1000 views per day and I am sure most were attracted to the theme regards running a fridge with little or no battery involvement and not to be subjected to the ongoing 'what's watt, what's not or whatever' stuff! I had earlier acknowledged my OP error and had hoped we could get back to what this is all about.
And as Raymond (P116) indicated I am no orphan with Watts quoted widely in reference to Watts/Hr in many metric refrigeration publications so perhaps I can expect some company back here in 'the naughty corner'
As for the anti eutectic brigade, there are many thousands of eutectic users out there who know better and comments from those who don't know yet refuse to understand the basic fundamentals, don't faze me.

It is a CREDIBILITY issue, Louie. Please understand that while you may have a great idea, if you can't express it clearly and have to take two shots at it as you have, PLUS the incorrect engineering terms when you're trying to sell your ENGINEERING, then please, please, please, don't dismiss it so cavalierly.

It does matter.

You never know when a potential customer could be a bloody engineer!!!

[StuM]

Originally Posted by Stu Jackson

A perfect summary.
I'm an engineer and using incorrect units is like fingernails on a blackboard to me and seriously detracts from whatever marketing might be happening. SERIOUSLY detracts, like in "Why should I believe anything this guys says if he can't get his units straight?"

It is a CREDIBILITY issue, Louie.

You got it. People may like to re-read posr #2 and the supposed rebttal in post #3 to draw their own conclusions about credibilty.

Originally Posted by StuM

> " indicates 433 watts per day"
> ...
>"85 watts per litre, is approx. 433 watts."

And incorrect units in almost every line of the attachement

You still haven't learnt the meaning of the basic electrical units I see.

Which makes any advice involving electricity dubious.

Originally Posted by OzeLouie

The reference refers correctly to watts of heat.
...

[rgleason]

Just to help move this along, I forget what size Danfoss Unit our Ozifridge Model C150/ T45-30 with 9 litres of eutectic solution mixed to freeze at 23 degF or -5degC with polypropylene glycol with the controls set for cut out temp+-7c and cut in temp= -2c but in thinking about how to improve the system, I considered the possibility of a more powerful compressor to take advantage of the times when we have plentiful power (ICE powered alternator in/out of harbor, or 1-2 hours power battery (initially 140 FLA amp-hr later changed to 214 ah fla) charging when voyaging.

Compressor: Danfoss BD50, Capacity 934 btu/hr (274 watts) <--there it is! If the manuf. wrote w/hr that would help
3.41 btuh/watt x 274watts (watt-hr or watt/hr) = 934

Our box is top entry, reasonably insulated but old insulation, fairly large 4.55 cu.ft. 2634 sq.in. surface area with an R-value=9 and delta T of about 53f and is not a freezer, but we can keep steaks somewhat frozen against the eutectic tank for a several days, but that is not the intent.

Would a larger Danfoss Compressor be advantageous to faster drawdown, or would it be impaired too much by requiring greater power during the longer periods when we are dependent on our battery?

Louie, I have no doubt that I have used confused or wrong units at times. Your points were completely clear to me, regardless. I think this units thing it beaten to death now.

I have also considered getting some of the more advanced premixed food industry eutectic solutions which phase change less gradually and over a smaller temp range than the polyprop glycol. I think that might be an improvement.

I have considered removing the counter top and fiberglass chest and rebuilding (big job) using
Aerogel - Pyrogel XTE Blanket 5mm x 5= 25mm= 1 inch, Pyrogel XTE - 0.14 BTU-in/hr-ft2-°F

[Richard Kollmann]

rgleason, your desire to improve your refrigeration system offers some real technical challenges for the design engineers on this thread. I believe there is only one lodgical answer but first lets look at the facts:
1. Nine liters of eutectic water and glycol with freeze point set to 23 F.
Considering changing solution to a true eutectic solution.
The total energy stored with glysol or a true eutectic or even water when phase changed to ice, each will contain almost the same amount of energy of 144 Btu per pound.
All three liquids will have the same rate of heat absorption be cause of this one plates design
The real difference between the three ice formations will be in the length of time it takes to phase change back to liquid. Glycol solution will melt the fastest and least efficient with almost no stable level plat-ow. My tests of true eutectic solution drained from Glaser Bay, Frigoboat, and Dole boat refrigeration plates showed a 15% longer melting time. And of course water in equal quantity lasted far longer but of the three temperature of ice and water was stable at 32 degrees F as long as there was some ice in plate.

The Btu output of any compressor is never steady Cap tube or TXv as assumed because the Btu flow rate reduces as the eutectic solution temperature drops and continues to reduce if compressor is not stopped by compressor.

[EngNate]

Panasonic U-Vacua Panels

About 9 times the R of urethane foam