Author Topic: Fighting Nature's Refrigerator (Read 11965 times)

valterra · « **on:** January 20, 2007, 04:23:26 PM »

I'm looking into propane refrigerators. Just for the heck of it, since my regular fridge is working fine.

I had a hair-brained idea awhile ago, and I would like your guys' feedback.

In Nebraska, during the winter, it's freezing cold. I run the heater in my house, which is burning propane and electricity to try to keep the house warm. Meanwhile, in the kitchen, my refrigerator is burning electricity, desparately trying to keep everything inside it from getting warm.

In other words, I'm paying to freeze air that I just paid to heat up! That seems ridiculous.

So, here's my hair-brained idea. Why wouldn't we build a refrigerator that had vents that ran to the outside. On freezing cold days, a small DC fan (think: computer case fan) could run to bring freezing air in from the outside. My fridge is literally 2 feet away from the outdoors (with drywall and siding in the way). You could filter the air to keep dust and smells out. And you could devise some kind of door to block hot air from entering during the summer months.

Am I nuts? I mean 2 computer fans (one for fridge and one for freezer) use less than 5 watts total. Than means all winter long, if your fridge ran continuously, it'd cost about 30 cents PER MONTH to run.

thefinis · « **Reply #1 on:** January 20, 2007, 09:53:58 AM »

Well the heat the fridge makes helps heat the house too so it is not all lost energy. One problem with the idea that I see is the temp control as the outside temp can vary from too darn cold to too warm in just hours. You can buy lots of electricity for one fridge full of food ruined.

I have my freezer out in a nonheated part of the house and it saves energy in the winter to keep it cool but I lose heat evey time the door is opened to go out there. I have wondered about making a closet for the fridge that has the backside vented as the cold air in winter would help keep it cold and in the summer the hot air the unit makes could be vented outside.

Finis

vawtman · « **Reply #2 on:** January 20, 2007, 09:57:29 AM »

The compressor on the fridge needs a warm side to function properly.Freezer temps usually run around zero degrees.

The fan will be heating the intake air abit plus the friction from the duct.

New fridges are pretty efficient nowadays

With the doors closed how would it bring the air in?

windstuffnow · « **Reply #3 on:** January 20, 2007, 09:59:04 AM »

I think its a great idea... I had similar thoughts a few years back and I don't think it would be a major project overall. I haven't, however, had the nerve to cut some holes in my frig and through the wall for the transformation.

You would need a temp controller of sorts to monitor the outside air and inside air temp. Two systems would be needed, freezer and frig. Only one hole through the wall would be needed for both systems. A simple "if and" sensor to control the fans, possibly a combination of 2 thermal sensors. "If" its cold enough outside "and" the frig's internal temp is high enough to turn on the fan.

The odor problem I haven't quite figured out as yet. We quite often have some pesky skunks running around out here, sometimes they get hit by a car and the smell outside is quite distastful... I really don't think opening up the frig to a "fresh skunk" smell would be very pleasing. It doesn't happen often but it would be nice not to experience it.

Overall it would take very little money to set the system up for quite a bit of savings through the cold months. I think its doable...

I think there are alot of ways to "combine" systems as opposed to using each appliance to do a separate job. I believe a single system could be made to generate electric, heat the house, heat the hot water needed and quite possibly frig and freezer as well as possibly inclucing an airconditioning system.

May as well maximize the use of the energies we already use instead of wasting the excess from each different appliance....

.

Jon Miller · « **Reply #4 on:** January 20, 2007, 10:10:53 AM »

Hi there,

Been thinking same thing for a while. So i turned my freezer around so the radiator on the back faced out. my thinking is that the heat from the radiator can get out easier so it dosnt have to run for so long. Where as if it was turned facing the wall the heat would build up acting as a insulation, increasing the time the compressor is on.

A freezer should be located in a cold room any way i think. Your idea is a good one, maybe like cut an old freezer to be able to pump cold air into the house with out cooling it of. Then place ur current freezer, fridge inside that?

Regards

valterra · « **Reply #5 on:** January 20, 2007, 10:15:08 AM »

As far as air coming in AND out at the same time, you would need two vents.

I'm talking about replacing the compressor (functionally at least) during the really cold months. Should be easy (I'd think) to make some kind of switch that (during the winter months) turns the vent fans off when the compressor turns on.

In other words, if it gets warm enough for the compressor to start, the vent system will shut itself off. So if it gets hot out, and the vent system starts bringing in (relatively) warm air, that'll trip the sensor on the compressor, which will take over.

Make sense?

valterra · « **Reply #6 on:** January 20, 2007, 10:15:51 AM »

It's REALLY cold here. I don't think the fan's gonna make much difference! :-)

Nando · « **Reply #7 on:** January 20, 2007, 10:38:53 AM »

Prior refrigerators,in the cold winter months, it was common to have a cool box aired to the outside.

Indeed, the idea of bringing cold air to keep food properly refrigerated is good.

The freezer cools to around -2 to -10 F, this for long life storage and if the meat is wrapped no cold burning.

The refrigerator side may run from 36 to about 44 Fahrenheit.

To bring cold air to a zone that needs to have low temperature, the air coming in should be dried to avoid the icing as you may seen in those refrigerators that do not have automatic de-icing.

A fellow I helped with his hydro in Canada, several years ago, had a system where he brought air with a blower into a chamber that had piping to cool the material in the pipe (one system was for the refrigerator, the second was to cool the house in summer).

To do a good job, one needs to have ways to accurately control and limit the air as needed, other wise one may "freeze" the refrigerator section, for this reason the air should go to the freezer section and from there to the refrigerator section.

This way the air coming in should be at lower temperature than 0 Fahrenheit.

For your "Hair-brained idea" as you defined it.

You could use those flexible ducts used for the cloth drier going to the outside ( available in several diameters) on for the intake and a second for the exhaust, two blowers, one to push and the other to suck the air out.

A small temperature detector to operate the fans that at the same time could open a gate to allow the air movement when needed, also another external temperature sensor to decide if the outside temperature is low enough for the "cooling" service and if not, to allow the refrigerator pump to operate and at the same time not allowing the gates and/or the Fans to be working.

The controlling logic is simple to do.

Nando

willib · « **Reply #8 on:** January 20, 2007, 10:41:26 AM »

I have made some modifications to my fridge

first i have disconnected the defroster(which heats the evaporator ? )and consequently uses a lot of electricity.

second i have insulated the rear where the condenser (cooling fins) tend to heat the back of the fridge.

third i built a box out of foam encasing the temp module and most of the upper part of the fridge.

the fridge is a standard over/under freezer/fridge.

I believe i have saved a lot of money since last spring when i made the modifications. Because when it does come on it only comes on for the minimum ,what, two minuits?

the downside is when warm weather gets here i have to manually defrost it (which dosent take long).

it takes time and effort to save electricity

Ahto · « **Reply #9 on:** January 20, 2007, 10:53:43 AM »

I have had similar idea for a while but instead of circulating outside air I'm thinking of using air from cellar or some sort of buried chamber, this way it would continue to work for the summer months too I believe. Cellars and pantrys have done their job for hundreds of years, haven't they? It's just the matter of having little part of it in terms of air space inside your kitchen.

RP · « **Reply #10 on:** January 20, 2007, 11:46:35 AM »

I think if I was going to do this I'd use a glycol loop. Two small holes punched in the refrigerator, a pump and an old radiator outside in a shady spot. Only need a simple thermostat to run the pump when needed AND when it's colder outside than the freezer chamber.

When it's too warm out, the pump stops and the regular compressor takes over. The pump could be run off a small solar bank. As far as it goes, you could lay in the copper glycol tubing in the existing evaporator section and the autodefrost would work for it too.

vawtman · « **Reply #11 on:** January 20, 2007, 12:36:16 PM »

Nice idea RP but wouldnt he be trying to cool the whole loop when its warm out say above 0?

windstuffnow · « **Reply #12 on:** January 20, 2007, 01:26:53 PM »

I had given the coiled transfere some minor thoughts as well. As long as you had a "bleed back" system built in it should be ok. When the pump went off the fluid would fall to the lowest portion of the resivour, the higher coil being outside. Similar to a drain down solar water heating system. This would bring the costs up a bit with the pumps, still saving a bunch on the cold months.

I've been tossing around a similar idea for a stirling engine mounted on my wood burner flue and piping in the cold water from outside.

Interesting ideas going on here !

.

jonas302 · « **Reply #13 on:** January 20, 2007, 02:59:21 PM »

I agree an antifreeze loop would work way better than air if just for smells and humidity I'm thinking a truck radiator on the outsie with an electric fan if needed and maybe a tranny cooler or heater core ac evaporator, ect on the inside with a mall fan to circulate and a t-stat to control a pump maybe if set up just right it would slowly circulate by itself as the antifreeze warmed in the fridge

Jonas

Countryboy · « **Reply #14 on:** January 20, 2007, 03:10:37 PM »

Isn't it easier to store your food outside, rather than trying to bring the outside and put it in your fridge?

I know many people who store stuff on their porch or breezeway during the wintertime. As long as animals can't get to the food, it will store just fine if the weather is cold.

valterra · « **Reply #15 on:** January 20, 2007, 03:27:30 PM »

Yep, we've often left our cases of bottled water out on the table on the back porch. BUT, animals could get into your regular food, you do still have to go outside in the snow / wind just to grab something, and if it warms up, you'd have to move everything back in!

My idea was trying not to change the routine too much, but improve on an appliance that we will continue to use.

But yeah, if it was cold here ALL the time, I'd just build a "fridge" that was really just an insulated door to a box that sat outside of the house.

jmk · « **Reply #16 on:** January 20, 2007, 07:08:49 PM »

I would worry about what is going to grow in the duct during the warm seasons like mold, and bacteria I wouldn't want to get legionnaires, or contaminate the food. I think a cool oil transfer sounds better.

jmk · « **Reply #17 on:** January 20, 2007, 07:20:18 PM »

If you put a transmission cooler in the refrigerator and another one outside at a higher placement and hooked the tops together with lines , and the bottoms together with lines the one in the fridge would hold the cooler of the oil as the warmer oil will try to go to the top which is outside in the cold. no pumps required

RP · « **Reply #18 on:** January 20, 2007, 11:17:03 PM »

Yes it could but that's why I said "AND when it's colder outside than the freezer chamber."

If it's too warm out the pump stays off. jmk pointed out below however that with a thermosiphon system you wouldn't have to do anything if the outside coil is higher since no water would flow unless it was colder outside than the freezer chamber.

If you want to get even more fancy:

Use a heat pipe system. You still have a coil inside and one outside located higher than the in-freezer coil but this time you pump it down to vacuum and fill it with enough freon (134-a would be fine) to fill the freezer coil with liquid. Heat (yes, there is heat in a freezer) from inside the freezer cause the freon to evaporate to gas which then travel to the outside coil where it condenses back to liquid and flows by gravity back to the freezer chamber. When it's warm out nothing happens since there's no liquid in the upper (outside) coil to evaporate and there's no gas convection since the freezer coil is still full of liquid.

There is a precedent for a passive system like this on the Alaska oil pipeline. They were worried about the permafrost that the pipeline is built on thawing and causing breakages so the pipe is supported on pairs of heatpipes. These heatpipes suck the heat out of the ground all winter but so not transfer the heat back down in the summer.

I've done some of the math on heat pipes to explore using them to freeze an enormous amount of in-ground ice in winter for summer airconditioning. It turns out you need a swimming pool size chunk of ice but if it could be frozen for free in the winter then all is not lost...

terry5732 · « **Reply #19 on:** January 21, 2007, 02:02:50 AM »

A refrigerator does not cool air. It moves heat from inside of it to outside the box. In the process it creates a little heat from electricity. It is a net heater. Electric heating is inherently less efficient than direct combustion due to conversion/transmission losses. But you are getting essentially free heat from your fridge as this heat is a byproduct of normal running for it's intended purpose.

Ducting cold air into your house to cool your fridge is crazy. You may as well put the fridge outside then and have to go out to get things - same as opening fridge door which is connected to outside.

There is an old wives tale about not putting a deep freeze in a cold garage because the oil in the compressor will be too stiff. This could only be a problem if your thermostat is set to -20. It doesn't matter what the viscosity of the oil is if it isn't going to run. They will be fine running at 0 to 10 degress, where it should normally be set.

The cat likes to lay by the fridge to warm up.

jonas302 · « **Reply #20 on:** January 21, 2007, 09:43:05 AM »

The heat coming off the back of the fridge has nothing to do with electricity it is the heat that is removed from the air inside the fridge that is the prosses of cooling air same as your car it would be a whole lot cheaper to heat your house with an electric space heater than the fridge

Countryboy · « **Reply #21 on:** January 21, 2007, 08:38:26 PM »

Back in my younger days, we didn't buy ice for our beer during the winter.

We had beer on snow, instead of beer on ice. We'd leave our beer outside in the snow. Dogs that would go out and pull a beer for you were always appreciated.

terry5732 · « **Reply #22 on:** January 22, 2007, 12:37:22 AM »

Did you invent a cold running compressor?

PART of the heat is 'waste' from the process of moving the heat.

During heating season the fridge is 110% efficient - it does it's job PLUS gives off some usable heat.

Bringing in cold from outside is BRINGING IN COLD

codesuidae · « **Reply #23 on:** January 29, 2007, 02:45:25 PM »

I'm also in Nebraska (west Omaha) and am considering doing something similar.

I recently bought a new house and fridge. The house has an unfinished basement, and the fridge has an internal heat exchanger with a fan to circulate the air. It occured to me that during the winter I could probably save some power by allowing the fan on the fridge to draw cold air from outside through some ducts installed in the floor (easily acessable from the unfinished basement). In the summer I can let the fridge draw cool air from the basement.

I don't want to pipe the cold outside air directly into the fridge, partially because I don't want the trouble of filtering, and partially because of the extra trouble involved in plumbing such a solution. By allowing the fridge's existing fan to do most of the work the modification is pretty simple, just some carefully placed ducts in the floor under the fridge, and maybe a very minor modification of the ductwork in the fridge itself.

I tried to find some figures indicating how much of an impact the cooler air would make, but the best I could find was a statement that a 10degF reduction in air temperature can reduce the power requirement by as much as 40%. The temperature difference between inside and outside ranges between 20 and 60 degrees here, so as a rough guess I'd put the savings at 50%.

Since it's easier to bring in just one duct from outside for testing, I'm planning to do that and I'll just deal with the cold draft for a while. If it saves power I'll rework the duct to keep the cold air out of the living spaces.

cyplesma · « **Reply #24 on:** February 12, 2007, 02:28:41 PM »

Just a brainstorm.

If you use plumbing (purple) to draw cold air in from either outside or basement in to the frige, make a box outside (green) and one in basement. run some pipe through the box and then into the fridge. that should keep the bugs and mice out.

Or is this the assumed type of plumbing that is explained above?

of course the box outside, keep out of the sun.

valterra · « **Reply #25 on:** February 18, 2007, 08:25:18 PM »

picture, please! :-)

cyplesma · « **Reply #26 on:** February 19, 2007, 10:09:41 AM »

SmoggyTurnip · « **Reply #27 on:** February 19, 2007, 01:31:52 PM »

I don't think the idea is a good one.

Taking cold outside air into the refrig and expelling warm air is putting valuable BTUs to the outside of the house that you are trying to heat. It is much better to move those BTUs into the living area.

The amount of heat required to heat your house is exactly the same amout of heat that leaves the house. Using this method results in more heat leaving the house.

.

deconstructer · « **Reply #28 on:** February 21, 2007, 02:49:27 PM »

I have constructed a "Cold Room" under my house that is well insulated from the rest of the house. I plan to install the chest freezer into this room. The room is just like the old root celler idea. It stays around 46 degrees all the time right now, which is better that the 68 degree most keep there house at. I also plan to store apples in sand or sawdust and all my canned food in the cold room. I do know that if the freezer enviroment is too cold the compressors will have trouble running. It is important to have a control system even if it is a manual one.

Dennisd · « **Reply #29 on:** February 21, 2007, 04:41:51 PM »

My big freezer is located in the root cellar, improving its efficiency but I find that the cellar heats up in the summer more than I like.

valterra · « **Reply #30 on:** February 23, 2007, 08:27:54 PM »

The "hot" air can be vented inside the house. Basically this is turning the refrigerator into something more like an ice chest. The idea isn't providing colder air for the compressor to remove heat from - it's about functionally replacing the compressor during ongoing cold weather.

I mean, didn't I see a picture on this board (or maybe it was a beer commercial) of guys sticking bottles into the snow drifts that filled a doorway. I just think it's silly to involve the "hot" air of the house at all. For all intents and purposes, this is an outdoor refrigerator - albeit phyisically sitting inside the house.

Tritium · « **Reply #31 on:** February 26, 2007, 10:39:37 AM »

The problem stated as an "old wives tale" about operating a compressor in sub freezing temps is a valid issue not because of oil viscosity but because during off times liquid freon will migrate to the "Coldest" part of the system. If it is the crankcase of the compressor (usually is when in an unconditioned space like a garage or porch) then the freon can cause a temporary lack of lubrication to critical compressor parts during startup leading to failure of crank bearings and motor bearings in the compressor. Crankcase heaters are installed in commercial compressors to prevent this occurance.

Thurmond

roughrider3 · « **Reply #32 on:** March 06, 2007, 06:12:33 AM »

put a old refig out side drill holes through frezzer compartment .

put small 12v auto heater in frig side with a thermast set to keep at a good temp

for milk not to freez,once set tranfer food then unplug inside refrig,will

saveprobly $20 dollars through winter months,then set back and listen to the oldlady compain (polity put)about haveing togooutside to get food to cook for

your dinner, unless power is not available your headed for a divorce

News:

Author Topic: Fighting Nature's Refrigerator (Read 11965 times)