Refrigeration - Evaporator vs. Holding Plate

[newhaul]

Originally Posted by RaymondR

"As has been pointed out earlier, these are not the correct units. The specific heat of water (the sensible heat) is 4184 J/kg-°C or 1 cal/g-°C or 1 Cal/kg-°C or 1 BTU/lb-°F. The heat of fusion of water (the latent heat of freezing) is 333,550 J/kg or 79.7 cal/g or 79.7 Cal/kg or 144 BTU/lb. Watts are not an amount of energy, watts are an amount of energy flowing in a period of time. An amount of heat is expressed in joules, small calories, large calories, or BTUs."

We would not have these problems if we stuck to BTUs and Ions or fractions of and leave the Watts for electrical definitions.

Really well there are a few dozen solar physics that would really like to know that

[RaymondR]

Originally Posted by OzeLouie

Oh come on Raymond, do you also want to go back to 'pounds, shillings, pence',......... 'ounces, pounds',........... 'inches, feet, yards, miles' etc ect.? The imperial system is a nightmare, with all of its crazy interacting factors. Decimal weights and measures are a God send.

A lot of the SI stuff has a problem for folks without any science background.

The problem is that by the time you wend your way from LMT to heat and heat flow in refrigeration any connection is lost in a forest of obscurity. And since Watts is used to define various physical but apparently unrelated properties it is a recipe for confusion.

The old imperial system was free of much of this obscurity.

One British Thermal unit being the heat required to raise the temperature of one pound of water by one degree fahrenheit and a ton of refrigeration is the amount of heat flow required to change the ice state of water to fluid in one day.

What could be simpler and more easily comprehended and is the system still in use in the largest western industrial and consumer country.

[StuM]

Originally Posted by RaymondR

And since Watts is used to define various physical but apparently unrelated properties it is a recipe for confusion.

Only if the units are used incorrectly. A Watt has only one meaning and it relates to the rate of transfer of ANY form of energy in exactly the same way, whether it is the rate that heat is moving or the rate than electrical charge is moving.



Watt hours and BTUs are entirely equivalent.
1 Watt hour is 0.293071 BTU


And if you are regularly working in litres and degrees celsius as most of the world is, BTUs are a PITA


The confusion only comes in when people don't know the difference between power and energy and persist in incorrectly using Watts when talking about quantities of energy (heat or electrical, it's all the same)

[RaymondR]

Originally Posted by StuM

Only if the units are used incorrectly. A Watt has only one meaning and it relates to the rate of transfer of ANY form of energy in exactly the same way, whether it is the rate that heat is moving or the rate than electrical charge is moving.



Watt hours and BTUs are entirely equivalent.
1 Watt hour is 0.293071 BTU


And if you are regularly working in litres and degrees celsius as most of the world is, BTUs are a PITA


The confusion only comes in when people don't know the difference between power and energy and persist in incorrectly using Watts when talking about quantities of energy (heat or electrical, it's all the same)

I was wondering when we were going to hear from you mate.

"ANY form of energy" And that is fine when dealing with folks familiar with a bit of the science of heat and thermodynamics but there's probably a lot of participants in Cruiser Forum who, whilst without that knowledge, are interested in refrigeration and would like to know more about it.

Keeping it simple will assist them in this. I would guess that the forum is predominately US in membership and the US still uses the imperial system and its BTUs and Tons.

The steam age did a hell of a lot more for thermodynamics than thermodynamics ever did for the steam age.

[AKA-None]

My geothermal is measured in tons
For what it’s worth

[SV THIRD DAY]

As these threads always do, they devolve into what I call Dock Expert BS.
Technautics has been building Eutectic plate units since 1968 and are currently selling them faster than we can meet demands. If people want to think they are not as efficient as a rolled thin aluminum evaporator, hey...fine. But years of real life test data shows otherwise as does thousands, of happy customers both with our CoolBlue units and OzeFridge units. I've learned long ago that debating technical details on internet forums is a waste of time, although it is fun sometimes to poke the bears and watch people squirm and reach for thin air...ha ah ah. It's the same nay-sayers every time...people see through them quite easily honestly.

Now, back to trying to find a way to keep up with orders...anyone want a Job? We can't find employees with all the Free Government Cheese being spread around the USA these days.

Cheers

[newhaul]

Originally Posted by SV THIRD DAY

Now, back to trying to find a way to keep up with orders...anyone want a Job? We can't find employees with all the Free Government Cheese being spread around the USA these days.

Cheers

Sure you pay my slip fees just say where

[Richard Kollmann]

Yes, there are many ways to express energy, This thread was comparing energy efficiency of refrigerator evaporators Roll bond thin plate versus Eutectic solution ice plates? To simplify this question which plate results in the desired temperatures within the same exact box, when comparing Daily Electricity energy to melting Thermal energy of low temperature ice.

This well read thread has covered all of the advantages and disadvantages of the Eutectic versus Standard evaporator. It would be interesting to see your thoughts if you were to select a new evaporator in the future, witch one would you select for your present size insulated box?

Thank to everyone participating in this well worth pleasure boat refrigeration it oversize

[newhaul]

Originally Posted by Richard Kollmann

Yes, there are many ways to express energy, This thread was comparing energy efficiency of refrigerator evaporators Roll bond thin plate versus Eutectic solution ice plates? To simplify this question which plate results in the desired temperatures within the same exact box, when comparing Daily Electricity energy to melting Thermal energy of low temperature ice.

This well read thread has covered all of the advantages and disadvantages of the Eutectic versus Standard evaporator. It would be interesting to see your thoughts if you were to select a new evaporator in the future, witch one would you select for your present size insulated box?

Thank to everyone participating in this well worth pleasure boat refrigeration it oversize

Have had both and installed both for customers personally I will always go holdover plate for a few reasons . First and foremost I have an excess of solar and wind energy production in most afternoons.

Secondly and by far most importantly the ease of defrosting a stainless steel plate with an ice scraper vs a heat gun or hair dryer for a normal roll formed aluminum evap plate.

Frosts a great insulator reducing the effectiveness of either plate type significantly.

5 minutes defrosting of holdover and pick out the ice vs an hour and lots of water in the bottom of the box.

[kenbo]

I'm not a refrigeration expert but over the years I've had my share of failures and successes with various types of refrigeration systems. And I've learned a bit along the way. I now favor cycling evaporator plates over eutectic for one simple reason, they maintain tighter control over the box temperature and my refrigerated food lasts longer.

I'm probably mistaken but I don't feel it's a fair comparison to compare aluminum evaporators with critical orifices to eutectic plates with TXVs. I'd like to see two well-designed and sized, equal systems compared with both the evaporator plate and eutectic plate controlled by a TXV with internal box temperature and consumed energy logged.

[OzeLouie]

Originally Posted by newhaul

Sure you pay my slip fees just say where

Be careful Newhaul, I here that Rich's employees all have to wear one of 'those' company shirts!!!

[newhaul]

Originally Posted by OzeLouie

Be careful Newhaul, I here that Rich's employees all have to wear one of 'those' company shirts!!!

Independent contractor on a 1099 wear my own company shirts.

[RaymondR]

Originally Posted by kenbo

I'm not a refrigeration expert but over the years I've had my share of failures and successes with various types of refrigeration systems. And I've learned a bit along the way. I now favor cycling evaporator plates over eutectic for one simple reason, they maintain tighter control over the box temperature and my refrigerated food lasts longer.

I'm probably mistaken but I don't feel it's a fair comparison to compare aluminum evaporators with critical orifices to eutectic plates with TXVs. I'd like to see two well-designed and sized, equal systems compared with both the evaporator plate and eutectic plate controlled by a TXV with internal box temperature and consumed energy logged.

I'm a bit baffled as to why an evaporator plate refrigerator would maintain a more constant temperature than one using a eutectic tank.

Firstly the eutectic fluid in the tank constitutes a thermal mass which, even if not frozen, should slow changes in temperature within the box.

And secondly, during the freezing and melting process the eutectic fluid takes in and gives off heat at a constant temperature.

In contrast the constant cycling evaporator plate operates under a hysteresis regime wherein the temperature is allowed to rise to an upper level where the compressor starts and the system absorbs heat and pumps it to the outside environment and on attaining the lower temperature setting the compressor shut off. The temperature constantly cycles between the set points for the box interior.

Assuming that the refrigeration system in a eutectic is set up to maintain some ice in the eutectic tank at all times the temperature in the box should never cycle up and down at all.

[Richard Kollmann]

RamondR The reasons eutectic plates are not stable in maintaining box temperatures are most all of them use Glycol and water and not true eutectic solution.

Kenbo you are correct in believing TXV provides faster reaction time and far better super heat evaporator control over the less expensive Cap tube orifice. TXV also can compensate for climate changes.

[RaymondR]

Originally Posted by Richard Kollmann

RamondR The reasons eutectic plates are not stable in maintaining box temperatures are most all of them use Glycol and water and not true eutectic solution.

Kenbo you are correct in believing TXV provides faster reaction time and far better super heat evaporator control over the less expensive Cap tube orifice. TXV also can compensate for climate changes.

Hi Richard.

I suspect that the problem with pseudo eutectic solution made from glycol/water or alcohol/water mixtures might be related to the concentration of glycol in the mixture and that the concentration required for refrigeration temperatures do not exhibit the separation of constituents as badly readily as those required for freezer temperatures.

That being said the company that Ozylou, and Ozypete before him, is employed by appears to be willing to carry out the tests required to properly ascertain the severity of the problem at the concentrations required, after all it would simply require placing samples of the various concentration in clear plastic containers in a freezer and observing what happens.

As for the separation and stratification of constituents problem some convection and consequent remixing must occur in the molten portion of the pseudo eutectic solution must occur but whether or not this is sufficient to maintain homogeneity of the solution. Again a matter for testing rather than just intuition.