Designing the perfect Icebox...?

[DMcCam]

I'm hoping get more input on icebox design concepts. I've been working on my icebox plans and came up with a list of stuff that I thought, "hey why don't I ask everybody what they think about all this?" I know most of this is going to sound pretty obvious but here goes.

No. 1 I noticed that all of the commercial ice boxes like the old Coleman and InstaFreeze units allow for a lot of air flow around the ice or ice compartment.

No. 2 They all place the ice on top of the cooling area. The logic would be that the more surface area of the ice in contact with the interior air, the more cooling possible.

No. 3 You need about 1" - 2" of air space for this design to work. None of the ice boxes have more than that at least when first loaded.

No. 4 The interior compartment can be any material impervious to water but most use either plastic or galvanized sheet metal.

No. 5 2" of rigid foam insulation would be about right for the average size icebox that would fit into a teardrop. More than that and you're headed into diminishing return land. This includes the door and it should overlap the insulation of the interior just like a refrigerator.

No. 6 The useful interior area to be cooled (width and depth) is the same area as the ice compartment plus the 1" - 2" of air space. This seems to be constant in all designs regardless of height.

No. 7 Good quality seals are absolutely important for the whole thing to work.

No. 8 All commercial units were designed to use block ice.

Did I miss anything guys and gals?

All the best,

Dave

[GPW]

Hard to beat the old Igloo style cooler eh ... Simple to make it better , just make a thick foam box and lid to put it in ... The more insulation , the longer the ice will last !!!! (Cowboy knows !!!) ... With the lid on top , when you open it up , the cold doesn't fall out as with a front door model ...
Don't think air circulation matters as much as Cold retention... JMHO...
Gotta' keep this stuff SIMPLE !!!

[aggie79]

Dave,

Depending upon your design, I think it would be nice, or maybe necessary, to add a drain for the ice compartment. Of course, this doesn't apply if your block ice is in a tray that you lift to get to the cold storage area.

A lot of times, we use two smaller coolers - one for drinks and another one for food. With the drinks, we just cover them with bagged ice. For the foods we don't want immersed in icy water, we use blocks of ice in a separate container that sits to the side of the food so we can access the food without lifting out the ice container.

For awhile I thought about building a cooler into my teardrop. If I had, I was going to have three compartments - one side for drinks, the middle for ice, and the other side for food..

I can't wait to see your build get underway.

Take care,
Tom

Tom

[DMcCam]

Well guys, if modern top loading ice chests are such a great idea, why are we trying to make them better? I have a 5-day white Igloo cooler that’s a pain in the ass to use. You can’t get to your food well and only works in the summer for 3 days before having to buy more ice. The best use for ice chests are for cooling drinks. For perishable foods they just don’t fit the bill.

After doing considerable research on iceboxes I settled on a front-loading, inner ice tray on top design. The early iceboxes had the ice stored on top or to one side open to the cooling area. Nothing changed with this layout until refrigeration came in so it must have worked pretty well.

When the engineers of the 50's revisited the icebox for camping, they went with interior ice tray, front door design with the small air space. If another design worked better, I would think they would have used it. They had the funds and manufacturing facilities to make the best icebox they could. With a name like Coleman, a lot was on the line. Many here on the board have touted the Coleman 3-way cooler as incredibly efficient, especially for the money. I’d use one if it would fit in my galley.

The design I'm working on is specifically to make the best use of the small spaces in teardrops. By using the latest technologies in insulation you can get the largest useful food cooling area. This is another reason you might want to build an icebox instead of re-purposing existing ice chests. If you use the spray foam type of insulation you can get as much as R6.5 per inch of the stuff. So 2" can give you up to R13. This way you are only loosing 4" of space around your cooling area. More insulation is not necessarily better. If you do an on-line search about the subject, you'll see that each additional inch adds less and less to the actual efficiency. So why would you take an ice chest and add more insulation around it thus loosing valuable food storage space?

Here’s the design so far. I used pink to represent the insulation even though it's likely to be spray foam:



Initially I was working with 4 blocks of ice but it just wouldn’t fit in the space. It would be nice to modify the design to use the extra 1.5â€

[Engineer Guy]

Here's a summary of what's been established to my 'critical thinking' satisfaction on this topic. The ideas above are really super!

1. Consumer Report-types have weighed in that Top Door Chest Freezers are more efficient/use less energy than Front Door types. If one had a 'Thermograph'-type Heat Viewer, one would see the cold air pour out when the Front Door type is opened.

The Chest arrangement of Food inside may be less convenient, but that's an entirely different issue from Physics 101 that cold air sinks and stays there [in the Chest type].

2. The issue of diminishing return on Insulation value is up for Barroom discussion.

Off Grid and Solar Home Geeks have created some thick wall Fridges and Freezers with Walls well beyond 2". Whether that's the best use in a TD is another Barroom discussion, but folks will argue this point pro & con.

3. The 'darling' of Insulation is Thermax. For years, it's been rated at R-8/inch. Easy to cut and work with, and easy to tape edges of to form a Box. Metal Duct Tape is good for this. Perhaps lining such a box with caulked, thin wall PVC Sheets from a Big Box Store would be one way to create a solid enclosure. The 1" version sold at Home Depot is rated at 7.2 R/inch, but folks round up and down for easy mental calcuation of total R. When you're trying to keep Food in the mid or high 30's and it's 110 outside [sealed, in the Sun], R-24 or R-32 is not crazy.

Taping Thermax around a commercial Cooler is one easy way to go; especially an old one gotten on the cheap...

4. Some water is usually encouraged, since it keeps Food colder than cold air. Nope, it's not 'all the same', despite what a Thermometer might say. Case in point: water cooled Engines were/are much better at cooling than good ole air-cooled VW Bug Engines. Water has 'more' heat-carrying capacity.

5. Hard plastic, square containers are a great way to pre-freeze Ice and lift out; especially if they have handles. No space is wasted. Leave them ~3/4 full and then freeze them. Put a tiny pinhole in the cap to allow air to escape as the freezing water expands.

Much of this has been worked out prior by Off Grid Geeks. Surf those sites for ideas to not recreate the Wheel.

Energy never lost never has to be replaced, by any means. Solar Electric Energy is mighty expensive/Watt. Super Insulation means 'excess' doesn't have to be generated by Rooftop Panels [or Propane, etc.]. Everything from Bricks to a few Cases of Beer is used by Off Grid Geeks as a chilling 'Thermal Flywheel' to keep a Fridge cold. The 'right' size of flat, square water/ice container in the bottom of a homemade Cooler could serve the same purpose.

Thermax Rigid Insulation

Sunfrost Refrigerators

[danlott]

It may not be as effiecent as a chest type cooler, but it sure will look neat in your teardrop.
I am sure it will work well enough.

Dan

[48Rob]

EG,

Very good post!

Rob

[DMcCam]

Hey Engineer Guy, thanks for the feed back sir. Of course you are right, any front door design is going to let the cold air pour out. The issue I was trying to address is about real world usage and design. If you place your ice in a separate ice area above your food compartment where by it has only the bottom surface area (or top if from inside the food compartment), will it cool the food better or less than the ice tray inside the food area? The older engineers of course weighed in on this.

It seems to me that there are only a few ways to improve the overall icebox design. Create a chest type icebox with a lid that houses the ice so it can be lifted off of the food chamber below (without breaking your arm) or make the entire food chamber pull out like a drawer from under the ice tray/chamber above it...yes?

I was also wondering about the use of those plastic curtains in commercial freezers. Would some kind of similar thing work with a front door icebox? Perhaps a set of thin slitted plastic material that would provide some cold air barrier just inside the icebox?

Hadn't heard of Thermax insulation only the vacuum. Sounds like a better working material for building, excellent. Sounds perfect.

I don't quite understand your last statement. Are you saying that By adding a lower 'catch' basin to the bottom of the cooler would make it work more efficiently? If so, you could add a double drain system so that a specific amount of water or ice would always be in the bottom? Interesting stuff here. If we can squeeze out every bit of tech for cooling, we should be able to add valuable camping time instead of extra ice runs.

Hi Dan, Thanks for the kudos sir. I'm hoping to make a real contribution to our little trailers. A very efficient easy to construct icebox would give us all a good alternative for off-grid camping.

Please keep those ideas coming everyone!

Dave

[Engineer Guy]

What I meant to convey is that any existing Home Fridge design I'd seen to date for Off Grid use put the Thermal Flywheel Mass in the bottom of the Fridge, due to ease of use and it being out of the way. Old Backs don't get strained reaching 'down' for Food; cold 'Mass' is down there instead. Mass helps get through cloudy days, when on Solar PVs, and can coast a TD Fridge through periods between charging, whether by the TV; Panels; or a Genny. However, Mass takes up some space. Thermal gradations in a Home Fridge exist [the top Shelf is a bit warmer], but can be ignored in a horizontal-style TD Cooler. Insignificant. Mass in limited space is likely overkill vs. super Insulation. We put Frozen Food and Cool Packs on top, last, when packing our Cooler.

I like the drawer idea; details being the devil, of course.

Water in the bottom, as we all 'remember' it, has that advantage of better thermal transfer that keeps Food in better contact with 'the cold' than does air. Lot's of folks are pretty passionate about leaving some water in conventional Coolers. I'm on the Fence on that detail due, not to the advantage thereof, but due to ease of use from not having everything be wet. Freezing Food and letting it thaw in the Cooler works for many of us. Edible Thermal Mass is 'all' Frozen Food is...

I think 2 'right' size shaped vertical plastic Containers about the size of one side of the Cooler would be nifty. It would be 'cold' throughout the Mass; would be easy to lift out; [if they had handles]; and would allow max Food storage. No moving parts, as with a lid of Ice. Food that tolerates warmer temps, like Veggies, could be packed in the middle. Milk, etc., could be packed to the left and right sides where the Ice Mass is.

Plastic Curtains, as used in walk-ins, have about '0' R value. Me, I'd skip the hassle of them.

Folks have caught on to 'super' Insulation. Case in point: 5 Day Coolers with nothing new but thicker Walls. Unheard of a few years ago. Take that idea and run with it into the future by using even more Insulation, or by using different R Values in your design. 2" Thermax for the Lid for ease of use; two doubled up to 4" total for only the bottom where the 'cool' is. Just a thought to think outside the box; no pun intended!

Check out Engels and other such Products to see their sliding Baskets for easier access while conforming to the top Lid advantage discussed above.

I absolutely agree that a front-opening, recycled old Door would have lots of style and cache while looking kewl. Perhaps you could have it both ways and put a stylin' Front Panel and Hinges on tastefully-done Thermax. The Lid/Door will get the duty cycles of [ab]use, so it's worth sweating the details of - like a good perimeter Seal Gasket - to ensure reliability.

Engel Products

Super Insulated Fridge References

Retro Appearance Appliances

[DMcCam]

I'm warming up to the idea of a pull out drawer. You'd make the ice loading from the top with a small hatch. The tray would look much like it does now with a back drain below it and removable for cleaning through the front door. The front door would be 1/3rd smaller in height and pull out on rails for access. This begs a question, when you pull the drawer out, would the air flow from the outside rushing in to fill the space negate the gains in cooling? I'd guess that the drawer would keep most of its cooling if it was a few inches shy of the top. What comes to mind are the lower freezers in refrigerators. Without the need for the door swing, I could make the thing a few inches wider to accommodate the slides.

Dave

[eamarquardt]

Crusing sailors have been optomizing the life of "ice cubes" for a long time.

Here is a summary of the accepted practices aboard cruising sailboats.

Top loading is the standard arrangement.

The more insulation, the better.

The lid should have as airtight seals as possible.

Ice should never be allowed to sit in water. The higher the ice is in the icebox, the better. The bigger your cube of ice, the better.

Water conducts heat 25 times better than air. Water standing in the bottom of your cooler is BAD as it optomizes the conduction of heat into your icebox. To get rid of the water that results from ice melting install a drain in the lowest point with a loop/trap that will allow the water to drain out, but not allow cold air to drain out much as a trap prevents sewer gasses from rising out of your drain pipes at home.

The cooling power of a pound of ice is 144 times the cooling power of a pound of water (due to the latent heat of fusion). My point: the cold water isn't doing a heck of a lot of cooling for you, hurts your efforts to minimize heat infiltration into your icebox, and you should get rid of it.

I've never seen it done on a boat, but you could put an insulated box under your ice chest, drain your melted icewater into that box, and use it to pre cool your drinks, etc. It would help, but given the cooling power of water (1 unit) versus the cooling power of ice (144 units) it's not gonna make that big a difference.

One trick I use when using ice is to put it into nylon mesh laundry bags. You can place the bags of ice on top of your food (keeping the ice on top and out of the water), remove the bag when you want to get to your food keeping all the ice together, and then replace the bag of ice on top of your food when your done rustling around in your icebox. Also, as the bag and ice cubes will conform to the stuff in your icebox, it's easy to use.

Better to learn from the experience of Sailors than to reinvent the wheel (or icebox).

Hope this helps.

Cheers,

Gus

[Shadow Catcher]

One of the factors that seems to be ignored in these discussions is the temperature of the ice. I tested a couple of store ice machines and found ice at about 30F. Ice coming out of our refrigerator when it is making ice is at -20F. That is a 50 degree difference, guess which will last longer.

[eamarquardt]

One of the factors that seems to be ignored in these discussions is the temperature of the ice. I tested a couple of store ice machines and found ice at about 30F. Ice coming out of our refrigerator when it is making ice is at -20F. That is a 50 degree difference, guess which will last longer.

The above statement is true but it's not as big a factor as one would think. It takes 1 btu to raise one pound of water 1 degree F. It takes 144 BTU to melt a pound of ice. It only takes 1/2 btu to lower/raise the temperature of one pound of ice one degree F.

So if you have 1 pound of ice at -20F, it will take 169 BTUs to melt it verusu 144 BTUs to melt a pound of ice at 30 degrees F. Better yes, but not as much as one would think without understanding the physics of what is taking place. Again, melting ice requires 144 units (which is a change of phase/state) which is a lot more than simply changing the temperature of water (1 unit) or ice (1/2 unit) one degree F.

If you want things colder, use salt water to make ice. The latent heat of fusion is about the same, but the ice will melt at a colder temperature.

Cheers,

Gus

[Kayperkay]

GREAT information people..! Thank you

[DMcCam]

Hi Gus, Thank you for your excellent information on the physics of heat, ice and water. No wonder none of the icebox designs have standing water anywhere and use block ice.

I can tell that you have a ton of experience with nautical ice chest design. There are great on-line how-to articles with excellent ideas to learn from. I’m planning on using the thermal loop in the drain line for sure. The ice chest design as used in boats does work better for keeping things cold. As I understand it you put your ice in the center of the chest with your food around it. Most all of these ice chests are custom made to fit the available space just like a trailer.

For camping on dry land the nautical versions are just as awkward as the standard ice chests. Yet, the old front-loading Coleman 3-way icebox purportedly keeps your perishable foods cold for 5-7 days. This would be much better than my modern top-loading extreme 5-day Igloo job that only works for 3 days. This it the crux of the entire thread, how to ‘refine’ not ‘re-invent’ the icebox design.

I think that most would agree that the front-loading icebox design is more ergonomic than the top loading ice chest. Your food is dry, cold and easy to get at. If the now 40-year-old Coleman design still outstrips the new chests in performance, it seems to me that it’s worth investigating. I noticed in your post you actually are using the icebox method with your nylon mesh bag on top of your food. This would work well but you still have to contend with your food sitting in water and lifting the ice each time you access it.

This is why I’m so interested in furthering the idea of the front-loading icebox. Here’s the link that got me going in this direction:

http://www.tnttt.com/viewtopic.php?t=35778&highlight=icebox

In my drawing above, I'd like everyone's thoughts on the wood framing between the insulation and the door. I've been wracking my brain as to a none wood solution like making the whole icebox from sheet metal or something. Is there a better way to make this connection work?

Regards,

Dave