Adding a Phase Change Material (PCM) to the icebox/refer

[Hayden Watson]

I was at a trade show recently where they were demonstrating a Phase Change Material (PCM) for use in heating and cooling applications. it is like what happens when water freezes in that it takes a lot of BTU's to freeze or thaw the stuff except that it can be formulated to "freeze" at any desired temperature. This is basically how the cold plates work. I am thinking of using this material to surround my evaporator. http://store.puretemp.com/matvesl/
I would then put the temp probe on the outside of this blanket which would cause my cold machine to run until it froze the blanket at either 1C or 4C depending on which I get.

Anyone else try this?

 

[Jackdaw]

Very interesting. Latent heat is a wonderful thing.

That might work great for ICEC boxes, which drag the the temp down to 34f when the D.C. System is charging. Those things changing state at 34f would absorb huge amounts of heat.

The 'warmest' they list is 29f. Wonder if them make them at above the freezing point of water.

 

[dlochner]

Haven't tried this specifically, however, our refrigeration is a Grunnert and it has 2 massive cold plates. Once the box is chilled to about 32f it takes about 12 hours for the temp to rise to 38f at which point it runs again. Each cycle is about 30 minutes or less.

There is no free lunch in this method. In order for it work it the stuff has to be chilled. The advantage would be while sailing the box would stay colder longer without draining the battery or needing to run the engine. For coastal sailing, from marina to marina, shore power could be used to chill everything, again avoiding the use of the battery or engine to remove the heat.

It is also probably less messy than ice that has to be drained from the ice box.

 

[Hayden Watson]

Very interesting. Latent heat is a wonderful thing.

That might work great for ICEC boxes, which drag the the temp down to 34f when the D.C. System is charging. Those things changing state at 34f would absorb huge amounts of heat.

The 'warmest' they list is 29f. Wonder if them make them at above the freezing point of water.

Jackdaw, the temps listed are in Centigrade so I am looking at either 1C (33.8º) or 4C (39.2º). I am thinking that the 1C would be too close to freezing so am more inclined to the 4C model. These things have more Latent heat than water so the storage is really good. I was planning on adding an ICEC control to my AB Cold Machine with the temp probe in the refrige box instead of mounting to the evaporator like the standard AB P-tube control. with the PCM in direct contact with the evaporator, my hope is that it will absorb all the cooling until the PCM is frozen and then start to cool the box which will shut down the compressor. what I am not sure about is whether I can keep the stuff inside the evaporator frozen.

 

[walt]

These things have more Latent heat than water

Do happen to know how much better than water? I could not find anything on the web site and if its a lot more than water. even more interesting. FYI, the number for water is below.

The heat of fusion for water at 0 °C is approximately 334 joules (79.7 calories) per gram,

Edit.. I got this from that web site for latent heat of PCM's http://www.puretemp.com/stories/understanding-pcms

The average latent heat ranges from 170 to 270 J/g.

If Im interpreting this correctly, these PCM are less effective than water.??

FYI, I was also somewhat looking at this from the ice chest perspective..

 

[Hayden Watson]

I looked on their website and found this table. Not as high as the sales tech led me to believe. (Imagine that!)
http://www.puretemp.com/stories/puretemp-technical-data-sheets
The 1C has 301 J/g with melting point of 34º
The 4C is much lower at 187 J/g with melting point of 39º That is quite a hit for 5º difference. Still given that you get 462 sq-in and 1-KG for $20 that will give me 187-kJ if latent heat which ain't bad,
I am concerned that the 34º might lead to freezing temps in the refer or not freezing the PCM.

 

[sesmith]

As dlochner said, no free lunch, so unless you're using electricity at marinas and were counting on extra time between refrigeration runs, you wouldn't gain anything. Adding insulation to the box would do more.

On my isotherm cold plate installation, they take it a step further, though. At times when the battery voltage is higher, like when the motor is running or my solar panels are putting out in bright sun, the system goes into freeze mode, where it runs the compressor on high speed and freezes the cold plate. At other times, it runs in a maintenance mode, running the compressor at a lower speed, and using about half the power. Makes the system very efficient. Now, if you could add those type of electronic controls to what you have, along with the phase change material...

 

[LeslieTroyer]

I think blue ice should work as good. It is also a phase change material. That is to say it freezes solid and melts to a liquid. Fancy words for marketing.

 

[Jackdaw]

I think blue ice should work as good. It is also a phase change material. That is to say it freezes solid and melts to a liquid. Fancy words for marketing.

Sort of. And regular ice is as well. The trick is that that do it an VERY convenient temperatures. Imagine a wall in an office that would 'freeze' at 68 degrees with cheap AC during the night, and then absorb 40x the heat slowly warming to 69 the next day.

 

[Jackdaw]

As dlochner said, no free lunch, so unless you're using electricity at marinas and were counting on extra time between refrigeration runs, you wouldn't gain anything. Adding insulation to the box would do more.

On my isotherm cold plate installation, they take it a step further, though. At times when the battery voltage is higher, like when the motor is running or my solar panels are putting out in bright sun, the system goes into freeze mode, where it runs the compressor on high speed and freezes the cold plate. At other times, it runs in a maintenance mode, running the compressor at a lower speed, and using about half the power. Makes the system very efficient. Now, if you could add those type of electronic controls to what you have, along with the phase change material...

The potential big gain here is for people with ICEC controlled boxes, which bring the temps (while under charge) down to 34F (1C). If you put the 1C PCM sheets in the box and THEY FROZE, you would gain all that latent heat from doing that, and it would probably double the time the box chilled before it had to run in regular compressor mode.

I might get one and wrap it round the inside of my box.

 

[Hayden Watson]

The potential big gain here is for people with ICEC controlled boxes, which bring the temps (while under charge) down to 34F (1C). If you put the 1C PCM sheets in the box and THEY FROZE, you would gain all that latent heat from doing that, and it would probably double the time the box chilled before it had to run in regular compressor mode.

I might get one and wrap it round the inside of my box.

I am planning on installing an ISEC control module to my Cold Machine. My hope is that I can reduce my run time while on battery and do the refreezing of the PCM while motoring. My plans is to cover all exterior surfaces with a loose sheet over the top of the evaporator box and then have the thermostat probe out in the refer box. My one concern is whether I will be able to keep frozen stuff in the evaporator.

 

[Hayden Watson]

The potential big gain here is for people with ICEC controlled boxes, which bring the temps (while under charge) down to 34F (1C). If you put the 1C PCM sheets in the box and THEY FROZE, you would gain all that latent heat from doing that, and it would probably double the time the box chilled before it had to run in regular compressor mode.

I might get one and wrap it round the inside of my box.

Jackdaw. with your experience with the ISEC control module, do you think the 1C would be a better choice than the 4C?

 

[dlochner]

Sort of. And regular ice is as well. The trick is that that do it an VERY convenient temperatures. Imagine a wall in an office that would 'freeze' at 68 degrees during the night, and then absorb 40x the heat slowly warming to 69 the next day.

That is an advantage when ambient temperature changes cause the phase change. Also if energy can. Be purchased off peak and efficiently stored for later use.

 

[Jackdaw]

Jackdaw. with your experience with the ISEC control module, do you think the 1C would be a better choice than the 4C?

I would. I have a digital thermostat probe in the the ISEC sensor housing and it goes (along with the whole box I assume) to 34f while charging. After a day on the water sailing, it controls at 40.5F.

 

[Hayden Watson]

Does your unit have an evaporator or cold plate? It seems to me that this will make my evaporator work more like a cold plate but one thing that I wonder about is will still be able to keep frozen items inside the evaporator. Those of you will cold plate refers, do you have a freezer section or is everything at refer temps.

 

[walt]

Wondering if you ever tried the phase change material?

I started recent thread where Im trying to run a fridge off a solar panel at a marina where I dont have reliable access to shore power and have the power to the fridge shut off at night with the intention of not beating the heck out of the batteries doing this long term (four or five months).

This phase change material is looking interesting for my application. I could improve the fridge by better insulation (too late for that..). I have noticed that I am really wasting a lot of the solar panel output on a typical day simply because Im not using as much power as the solar panel is outputting.

I also checked the website for these phase change bladders http://store.puretemp.com/matvesl/ and unlike batteries for energy storage, the phase change material pretty much never wears out. They mentioned 65000 cycles with no degradation.

So Im liking the idea of the 39F material like the Puretemp 4 http://www.puretemp.com/stories/puretemp-technical-data-sheets which was already suggested.

The hope would be that it would work the fridge harder on a typical day where Im just not taking advantage of the all the solar available and store that energy in the phase change material for the night when the fridge power was shut off. Batteries wear out.. this stuff does not.

On cloudy days when I didnt have lots of sun and excess from the solar but the fridge power was turned on, hopefully the Isec would somewhat limit running the fridge hard...

 

[Hayden Watson]

Wondering if you ever tried the phase change material?...

So Im liking the idea of the 39F material like the Puretemp 4 http://www.puretemp.com/stories/puretemp-technical-data-sheets which was already suggested.

The hope would be that it would work the fridge harder on a typical day where Im just not taking advantage of the all the solar available and store that energy in the phase change material for the night when the fridge power was shut off. Batteries wear out.. this stuff does not.

On cloudy days when I didnt have lots of sun and excess from the solar but the fridge power was turned on, hopefully the Isec would somewhat limit running the fridge hard...

I have not yet experimented with this concept because this summer my AB started leaking refrigerant. once I get that resolved I will do some experiments.

One thing to remember is that in order for this to work properly you need to be sampling the box temperature like what the ISEC control module does and not the standard AB temperature probe that is attached evaporator like I have. I was thinking that I may try some phase change matts and move the thermostat probe to the box side of the matt to see how that does until I get an ISEC. Too many boat bits!

 

[JRacer]

Interesting stuff. I'll be interested in you guys outcomes. I don't have refrigeration but go through lots of ice through the summer. Mixing Dry and Wet ice to maximize the cold while keeping it above the freezing level.

 

[Hayden Watson]

Interesting stuff. I'll be interested in you guys outcomes. I don't have refrigeration but go through lots of ice through the summer. Mixing Dry and Wet ice to maximize the cold while keeping it above the freezing level.

Before I had refrigeration, I used the built-in icebox as the refrige and a good quality ice chest for the freezer. I would line all side/top/bottom of both with the foil-backed bubble wrap insulation. We pre-made most meals such as stew, stroganoff, lasagna, etc and packed them in vacuum bags and froze them in the deep freeze at least 3 days in advance. This all went into the “freezer” with 20 lbs. of dry ice on top. I then filled any unused space with gallon jugs of milk and water that were also deep frozen.

I used frozen water and milk to cool the icebox. The freezer was at -107ºF and when the gallon jugs of water in the icebox would start to thaw I would swap them for jugs in the freezer. I would also place the frozen food in the icebox a full day before using it so that it was also ice” for cooling the box.

This would allow me to go for a full week without adding any ice. This also had the added advantage of putting all ice in containers so that we never used bags of ice with the problem of water in the icebox.

Tip, when using dry ice fill all open space in the dry ice chest with balled up newspaper to minimize convection stirring which will make the dry ice last longer.