Improving one refrigeration compressor's performance

[bdgWesternMass]

Well I have now been around long enough, to piece together the controversy in refrigeration, that I could sense, but not understand

I'm grateful for all the information that has been provided and thank all participants for the information.

Now that the topic is multi-generational, I'm kind of curious how old was the previous thread?

[wsmurdoch]

Originally Posted by OzeLouie

Sorry to confuse you Bill, this data chart was part of a broader explanation so easily misunderstood. It is a printout of a data logger recording daily power consumption with the day's day number at the base, and was part of that broader report.
The 4577 watts and 9940 watts as shown in different colours, are accumulated consumption for each system type to maintain the cabinet at under 4C., and each for a total of 30 days.
X -axis relates to days being 60 in total, 30 powered as a cyclic system and 30 as eutectic but each in 8 to 10 day periods as colour coding indicates. Y -axis indicates watts consumed for the day (24hr) period.

It is the "Y -axis indicates watts consumed for the day (24hr) period." that I don't understand. If the refrigeration system draws 400W and runs for 12 of the 24 hours in a day, is that reported as 12hr x 400W = 4800W?

Bill

[OzeLouie]

Originally Posted by wsmurdoch

It is the "Y -axis indicates watts consumed for the day (24hr) period." that I don't understand. If the refrigeration system draws 400W and runs for 12 of the 24 hours in a day, is that reported as 12hr x 400W = 4800W?

Bill

Bill the Y axis refers to the daily (24hr) consumption in total as compiled by a digital data recorder. This recorder tallies the watts consumed for each day as shown in each days column and also the total consumption for each systems total trial period. It, like most similar quoting in metric, relates to watts as amps can be confusing. Amps relies on supply voltage and that varies making amp-hr consumption rates dubious at best. .

BTW when 'watts' or 'amps' is quoted bare, that is without a time reference, it is usually assumed by most that the related period is one hour. Check out all industry data, fridge / air con ratings, compressor manufacturers etc for confirmation of this.

[dfelsent]

This is exactly why some of us are particular about units. 12hr x 400W is 4800 WH. Watt-hours.
A unit of energy.
A watt is a unit of power.

Not the same thing.

[RaymondR]

Originally Posted by Richard Kollmann

Raymondr If your interposition now is correct that eutectic plate evaporator systems and standard evaporator system could be made equal in daily energy consumption, I agree. The main advantage of eutectic plates is they can store surplus energy in the forum of low temperature 144 Btu per pound ice. It is unlikely we can take a source of energy and increase it in our refrigeration system.

Hi Richard.

I am slowly coming to the conclusion that we are not fully exploiting the capabilities of the small DC refrigeration compressors.

Both the TXV and capillary controlled refrigeration cycles were originally designed for AC mains driven compressors, that is compressors with motors whose speed is tied to the frequency of the mains AC distribution system and are consequently, single speed devices. In these systems the refrigerant flow control devices may only control a relatively narrow range of outputs from the condenser.

Consider a different system where flow out of the condenser was allowed for any compressor speed and only controlled so that the output was liquid ie a high side float. The TX valve could then be configured so that any flow rate into the evaporator was possible it, the TX valve being only used to control the superheat of the return vapor to the compressor to ensure it was liquid free.

The compressor speed could then be controlled so as to exploit the electrical power available whether by solar, wind or batteries.

[StuM]

Originally Posted by wsmurdoch

It is the "Y -axis indicates watts consumed for the day (24hr) period." that I don't understand. If the refrigeration system draws 400W and runs for 12 of the 24 hours in a day, is that reported as 12hr x 400W = 4800W?

Bill

Nope if a graph shows 400W for a day, that can only sensibly be taken as the average power draw. IOW, 400 x 24 = 9600Wh per day

This is the sort of confusion that arises when people insist on continuing to use incorrect units and not grasping the difference between power and energy.

(To add together different "wattages" at different times in nonsense, regardless of any ridiculous assertions about assuming other dimensions such as time!)

[StuM]

Originally Posted by OzeLouie

Bill the Y axis refers to the daily (24hr) consumption in total as compiled by a digital data recorder. This recorder tallies the watts consumed for each day as shown in each days column and also the total consumption for each systems total trial period.

Please provide a picture of a digital data recorder with a totalled consumption figure showing the unit as Watts or W.

[OzeLouie]

Originally Posted by Richard Kollmann

I would think even common sense would surly indicate that a eutectic plate tested to be 100% more energy efficient there must be things wrong with the test. Variable speed Coefficient Of Efficiency also applies to thin plate efficiency unless the plan was to over power plate with too large of a compressor. A properly designed system today cycles very few times a day and cycling pump down wattage lost except for the first start of the day hardly measurable once evaporator is at operating temperatures.

Now with your chart you indicate Eutectic plates again create energy within them selves not possible. Is it possibility the correct size compressor's output and matching correct size evaporator could achieve the same COP on your chart cycling less and still result an less daily energy. This assumes the same size box is used. And yes the compressor may run much longer with still less daily energy used.

Richard Kollmann;3440284]I would think even common sense would surly indicate that a eutectic plate tested to be 100% more energy efficient there must be things wrong with the test. Nothing wrong with the test Richard, just your usual twisting/ denial of the facts to try and discredit my company and product. It was NEVER claimed to be 100% more energy efficient.. and again..

Now with your chart you indicate Eutectic plates again create energy within them selves not possible. This also is simply NOT true and a creation of yours. We NEVER claimed any such thing. Suggest you inform yourself regards latent heat and phase change energy storage, then read our test report again. If you need just ask but in the meantime please restrict any quote to the truth instead of that sort of malicious nonsense.

[StuM]

Originally Posted by OzeLouie

It was NEVER claimed to be 100% more energy efficient

Hmmmm, problem with basic arithmetic as well as electrical units?

9940 / 4577 = 2.17 Looks like an actual claim of more than "100% more efficient" to me.

[RaymondR]

You will notice that the power consumption of both systems increased during the trial. Probably because of the onset of summer so there is another correction required to be made to the data to compensate for non time concurrency of the test over the long period. And probably another to account for the fact of the day/night operation of the compressor for the evaporator plate case versus the all daylight, when it's warmer operation, of the eutectic system.

I vaguely recall that the claimed increase in efficiency in respect of the non continuous cycling was 40% but don't recall where this number came from.

[Richard Kollmann]

The again, facts in post 129 should re confirm for those paying attention that the performance chart is unrealistic. Pointing out facts should not be considered a personal attack to anyone.

[valhalla360]

Originally Posted by wsmurdoch

It is the "Y -axis indicates watts consumed for the day (24hr) period." that I don't understand. If the refrigeration system draws 400W and runs for 12 of the 24 hours in a day, is that reported as 12hr x 400W = 4800W?

Bill

Are you trying to give him enough rope to hang himself?

PS: It's funny when they double down on a mistake rather than just admit the label was wrong.

[RaymondR]

I would not be to hasty to discount the results of the trials without a review of all the records from them. I believe they were originally run by Ozypete who is now battling serious health issues and probably does not want to reenter the battle.

My understanding of the experiment is that it used two identical condensing units. A single insulated enclosure contained an evaporator plate and a eutectic tank. One of the condensing units was connected to the evaporator plate and the other to the eutectic tank.
Instrumentation recorded relevant operating conditions ie the temperature for the insulated enclosure and the power consumptions of the two consensing units.

The individual systems were each run over ten day periods with the insulated box being held down to the same average temperature and the temperature and power consumption data recorded for each run. Three sets of trials were run for each system.

As a purely scientific data collection exercise one might consider further enclosing the test rigs in a second larger enclosure wherein temperature and humidity could be held constant in order to fix the operating environmental parameters constant however as a real world comparison of the two systems it was not necessary as with a little work on the daily data sets for each system the environmental factors could probably be normalized.

There was actually only a single check required to validate the comparison and this was to observe whether the power draws of the two condensing units were the same for the same environmental factors with the evaporators experiencing the same heat loads ie switch both condensing units on at the same time and see if the current draws and supply voltages were the came or a close match. Having gone to the trouble of setting up and running the experiment I'd be surprised if Ozypete had not done this.

It appears that Ozypete ran the experiment to confirm inferences made in relation to the relative power consumption efficiencies of constant cycling versus eutectic refrigeration as used with DC powered, solar sourced and battery stored low voltage electrical systems as are commonly used on pleasure vessels.

Ozypete's company manufactures and markets eutectic systems for the mobile refrigeration market so the outcome of the tests has commercial ramifications. However it should also be said that they could, and probably more easily could manufacture evaporator plate systems and my personal recollection is that they once did so and advertised same for sale.

The in service operations of the two systems are that the evaporator plate based system operates uninterruptedly to pull the temperature of the insulated enclosure down to a low temperature and then cycles on and off to average the temperature at this low point. The eutectic system also operates uninterruptedly to pull the temperature of the insulated enclosure down to a low value, however at this point the operating regimes differ. The evaporator plate system cycles on and off 24 hours per day in order to hold the insulated enclosure at an average low temperature and the eutectic system continues to operate after the initial pull down in order to change the state of the liquid eutectic fluid into a solid thereby creating a heat sink exploiting the heat of fusion phenomena to "store cold".

The significance of this is that by "storing cold" the eutectic system avoids the requirement to store sufficient electricity to carry the operation of the condensing unit through the night time hours when solar power is not available. It time shifts the period of electric power consumption entirely into the period of electric power generation in order to reduce the need for electrical power storage.

I repeat all this, which we are all aware of, in order to pose the question, was Ozypete's experiment a valid test of the hypothesis that it's cheaper to "store cold" than it is to store electricity?

In my opinion it was a valid test and can only be validly challenged by repeating the experiment to confirm or refute the collected data. Bickering endlessly about details will not do the job.

[wsmurdoch]

Originally Posted by valhalla360

Are you trying to give him enough rope to hang himself?

PS: It's funny when they double down on a mistake rather than just admit the label was wrong.

No!!! I am not trying to give him enough rope to hang himself. It difficult (perhaps impossible) to assign motive, and this is not my motive.

I am a 70 year old retired chemical engineer (BS MS PE) who has a boat with a PG/H2O holding plate freezer/refrigerator refrigeration system chilled by either an engine driven compressor and water cooled condenser or by a 125V air cooled condensing unit who is trying to make sense of the unexpected (by me) results of the testing done by Ozefridge. I want to understand the testing, do some maths, and analyze the results with the hope that I can improve my system and its performance in the Bahamas. irish-eyes-to-the-bahamas.blogspot.com

At age 70 and with a 1988 boat, I doubt that I will be an Ozfridge customer, and I am banking on the good will of the Ozfridge company to provide me with the data that I need.

Bill

[Richard Kollmann]

RaymondR you are assuming that the condensing unit for standard evaporator was operated by a less efficient compressor speed. The state of these new Danfoss variable compressor designed for today do not cycle often as would be indicated by the test in question.
You also did not explain their extraordinary thirty day one hundred percent energy differential. Your summarize of test comparison you agreed test was factual. Please speak to the 100% energy differential there must be a reasonable answer for this.