crazy 3rd-world idea: aircon from small fridge [Archive]

lsemprini

07-05-2006, 07:21 PM

Hello esteemed refrigeration engineers,

I have an interesting MacGyver-style problem
relating to refrigeration and air condtioning,
and would like to dip into this incredible pool
of theoretical and practical knowledge to
see if it can...somehow...be made to work.

BUT WAIT...READ ON BEFORE YOU RESPOND...

In order to avoid triggering certain
understandable and very reasonable instincts
that you have, I need to set the scene first...

Imagine for a moment that you are suddenly
transported from your modern, highly professional
world of precise measurements, refined,
specifically optimized-for-purpose design,
unbelievably thorough and conservative safety
analysis, and high expectations for performance
and efficiency, into a third world backwater where
even the most basic resources such as refrigerators,
aircon units, refrigerant, and spare parts are scarce
luxuries.

Picture yourself in a world where a 7000 BTU
window aircon unit costs 6 months of a family's
wages and is therefore unthinkable for them.

In this world, everywhere you look, the locals
have devised fiendishly clever means of keeping
their old equipment working, and adapting old
equipment to effectively do things no engineer ever
imagined it to do. In this world, there are NO
inspectors, NO liability lawsuits, and
absolutely NO expectation that any technology
will work for any significant length of time; instead,
there is enormous gratitude any time any technology
can be adapted to help people for any period
of time.

I live in a place like this in a backwater of
rural Northern Thailand.

My observation here is that aircon units in
the 7000 BTU range which eat 600W of power
cost upwards of $500, while used (but working)
small 80-200 W fridges regularly cost $25.
I have not seen any cheaper aircon solutions.
I have not seen any evaporative/swamp
coolers at all (presumably because they don't
work at all in the humid climate).

Many locals seek a way to cool one small room.

My question is:

If you only had access to small fridges and wanted
to cool your room, how would you go about it?

How can one rip apart a fridge and MacGyver it up,
perhaps with an electric fan, into a device to cool
the air? Is there a better way to do this?

What are the theoretical issues of this? Is there
anything fundementally different about a fridge's
compressor/refrigerant/condenser specs compared
with those of an air conditioning unit, other than
simply the BTUs, that would prevent this from
working? If a small fridge's compressor were
running all day instead of intermittently,
would it burn out?

What about mechanical and practical issues?
I am assuming (correct me if I'm wrong) that
the condenser coil would have to end up outside
the room, while the evaporator coil (or freezer
tray!) would have to be inside the room with
warm air blowing through it. After disassembling
the fridge, can its coils and tubes be "bent" into
some appropriate shape without causing those
coils to break or lose their proper charge? Or, is
there a way to do it on a typical small fridge without
bending the copper tubing?

There are some local repair shops here which can
work on fridges, but "local" means a 4 hour bus ride
away, and "repair" is primitive at best. If AT ALL
possible,we are looking for a procedure that a non-
fridgie can do. If it takes a LOT of labor, that is
NO problem--labor is almost free. If it takes a lot
of troubleshooting and trial and error, no problem.
If it takes any specialized expensive equipment, it is
instantly out of range.

All the fridges I have seen use R12 and are of the
"hermetic (the motor & mechanical parts are sealed
within the case)" type, not belt-drive. I can provide
a typical photo of the compressor setup if it will help,
and I will be happy to research any other data points
you need. I am not a fridgie so please explain any
stats that you need.

Remember--LOW expectations. Anything you can
provide, any little improvement, will be met with
nothing but appreciation, for the alternative is
nothing at all.

Let me give you some perspective: when you
have a flat tire here, you pull over to the local
"ba yang," where some old guy fires up a tiny
concrete cooking barbeque (the same one he
uses to make super-tasty barbequed pork
satay), heats up a chunk of rubber from someone
else's old tire in a homemade iron press tool
resembling a nutcracker, clamps and melts the
"patch" into your tube with satisfying hiss,
you pay up to 10 baht (25 cents US), and you're
off for another few weeks/days before it happens
again. Some people patch their tubes 10-20 times
before they feel it's necessary (or can afford)
to replace them. They are grateful that
"ba yang" are so ubiquitous and helpful.

Looking forward to some great ideas, or at least
some clear explanations of the limits of the idea!

Thanks!

Dan

07-05-2006, 08:00 PM

I suspect your question is a good one, but you have over-explained your dillemma.

Copper can be bent.
A refrigerator can condition air.

Having explained your environment, you can ask a specific question and get some good answers.

lsemprini

07-05-2006, 08:30 PM

Having explained your environment, you can ask a specific question and get some good answers.

Well, these are my specific questions from the post:

How can one rip apart a fridge and MacGyver it up,
perhaps with an electric fan, into a device to cool
the air? Is there a better way to do this?

What are the theoretical issues of this? Is there
anything fundementally different about a fridge's
compressor/refrigerant/condenser specs compared
with those of an air conditioning unit, other than
simply the BTUs, that would prevent this from
working? If a small fridge's compressor were
running all day instead of intermittently,
would it burn out?

What about mechanical and practical issues?
I am assuming (correct me if I'm wrong) that
the condenser coil would have to end up outside
the room, while the evaporator coil (or freezer
tray!) would have to be inside the room with
warm air blowing through it. After disassembling
the fridge, can its coils and tubes be "bent" into
some appropriate shape without causing those
coils to break or lose their proper charge? Or, is
there a way to do it on a typical small fridge without
bending the copper tubing?

I am appealing to the experience of folks here
to find problems with and suggest a design for
this MacGyver task. Your post is a start!
You said:

Copper can be bent.
A refrigerator can condition air.

Does the first part mean that one should be able
to (carefully) bend the copper tubing of an
already-charged fridge without causing it to
discharge or otherwise break?

Does the second part mean that the answer to
my question is "no, there is no difference"?

Are my assumptions about the placement
of the two coils correct? Is there another way
to do it that might be easier and involve
less tweaking of the original fridge?

As to the mechanical/practical issues, I am looking
for specific suggestions about how to rig up a
disassembled fridge to make it a good air cooler.
Since I am not a specialist in this area, possibilities
that are obvious to you might not be obvious
to me. For example, there could be many ways to
blow air through -- a fan behind the freezer tray,
unwind the evaporator coil and wind it around the
grille of a fan, place a fan in front of the freezer
tray and have it suck air, etc... I'll bet there's some
easier, better way that I have not even considered.
Maybe there's even some way that involves
minimal disassembly of the fridge.

My post hopes to get the engineers here
thinking about a free-form design problem,
as opposed to being a request for specific
data on a formula or material property.

Unfortunately, that means I can't give you
super-specific questions as you may
have hoped.

Fortunately, free-form design is by far
the most fun aspect of engineering!
Hope that's okay for this forum.

Thanks again.

The MG Pony

07-05-2006, 09:07 PM

If you take great great care at dismantling it you can extract the whole cooling unit as one peice.

Secondly insulate the chosen room very very well

Set the condencer and comdressor where it will have much air flow perhaps even a fan

gently bend the tubes into a air handler of any sort into the room of coice after this insulate it heavily.

It will take it a long time to reach a cold tem in said room and will make the system work hard so cooling the compressor as much as possible will be wise.

I my self made a water cooled air handler out of an old fridge evap and a larg card boad box that I ran tap water through the coil! works well at both dehumidifying anf cooling the small place

Brian_UK

07-05-2006, 10:33 PM

Hi lsemprini

The copper tubeing should be able to be bent with care without too much problem. Work slowly and gently.

The evaporator section may be made from two sheets of aluminium pressed together into the shape of the ice box. Bending or straightening this may cause a breakage so be very, very careful.

Thinking sideways for a minute..... if you can get the icebox section out of the fridge in one piece - good.

Place it inside a well insulated box so that it becomes a small freezer box on its own. Now fit a fan to one end of the box, with a hole in the box, and an opening at the other end to let the cooled air out. Does that make sense to you? - Its's easier to draw than to write!!

You may need to add some baffles of some kind to keep the air against the coldest part of the coil.

Regarding the compressor; it should be able to run 24 hours a day without problem providing - it needs to be kept as cool as possible. An electric fan is good but obviously cost more to run. So, clamp some cooling fins to the compressor body, fit it inside a tube of some sort which is open at top and bottom. This will then act as a chimney using the natural draft effect to move cooling air over the compressor body.

How are we doing so far? :)

Peter_1

08-05-2006, 06:39 AM

Problem I see, 7000 BTU = 2000 W and is small, very small for a window unit, especially in humid climates and in poor or non-isolated rooms.

So, a small fridge has perhaps a capacity of 150 W, so you need 10 fridges to do the job.

It's like a Norway guy tries to heat his house with a lighter or a match.

Don't forget also that the climate is very humid, so you will have a lot of latent heat to remove before the air wants to cool, or in other words, before you will notice a noticeable temperature drop.

Second, the condenser was designed to handle a load on the evaporator of +/- 0°C (32°F). You will blow air over it much, much warmer. Can the compressor handle this and especially, can the condenser handle this very high load, again, in a very hot climate.

Another problem, most of the evaporators of the cheap units are inside the covering, just behind the inner walls. These are mostly foamed in the isolation of the cabinet.

If it's a plate evaporator, then it will be very difficult to bend it in another shape without leaking because the tubes are pressed in the plates.

What's your job over there anyway because you write fluent English which seems strange for me.
I was in your country in 1999 or 2000 to visit the factory of Mitsubishi Electric. (Phuket, Patong, Phi-Phi, Bangkok as far as I can remember)

lsemprini

08-05-2006, 07:04 AM

How are we doing so far? :)

Great! These are the just the kind of ideas
I was hoping for. Thanks MG Pony and
Brian_UK.

Your description of the "small freezer box" makes
sense but can you give me a little more detail on
what you mean by:

The evaporator section may be made from two sheets of aluminium pressed together into the shape of the ice box. Bending or straightening this may cause a breakage so be very, very careful.

Do you mean aluminum foil or sheet material?
By 'pressed together' do you mean that the
two sheets sandwich the evaporator coil
or something else? Having trouble picturing
this.

Regarding the compressor; it should be able to run 24 hours a day without problem providing - it needs to be kept as cool as possible. An electric fan is good but obviously cost more to run. So, clamp some cooling fins to the compressor body, fit it inside a tube of some sort which is open at top and bottom. This will then act as a chimney using the natural draft effect to move cooling air over the compressor body.

MG Pony also mentioned water cooling the condenser
coils.

Here are my questions on this:

From your posts, it sounds like you think the
compressor might actually overheat and break if,
say, the the compressor and condenser coils
were just hanging out a window, open
to the (warm to hot) outside air and slight breeze,
but without any additional form of cooling
such as a fan or water. Have I understood
that correctly, or did you just mean that the
system won't cool very well but the compressor
is not likely to break? I'd like to get a sense
of how 'tough' a compressor is and what causes
it to break.

I wonder if there might be some way to jerry
rig the fridge's thermostat to make the
compressor run all the time unless it reaches
a dangerous temperature range?

Next question is more theoretical:

The fridge itself is already using the compression
and expansion of a refrigerant to move heat to
the condenser coils.

You have suggested further refinements such
as an outside fan or water stream to help the
condenser shed heat.

My question is: are these strictly additive?

In other words, let's say the fridge by itself
can cool the 90F air down to 70F. Then let's
say I start cool water flowing over the condenser
coils.

Will the cooling power of the water REPLACE
the work done by the condenser/refrigerant
or ADD to it? Should I expect to get air that's
still about 70F or much cooler than 70F?

Put another way, will the compression and
expansion of the refrigerant material add
and subtract a certain number of degrees
from the air temperature regardless of what
the air temperature is (e.g. 90F -> 70F
or 60 F -> 40F), or does the refrigerant
have a narrow operating range, outside
of which it is not able to further cool
the air?

Thanks much!

lsemprini

08-05-2006, 08:24 AM

Wow, this forum sure has a lot of moderators :)

Thanks Peter_1, these are good points.

As far as the capacity, I agree it's a long shot
but I'll probably try to make one prototype just
to see. Thanks for the calculations.

I don't understand the theory well enough
to know: if the system is underpowered to
that extent, is it likely to cool the air
extremely slowly or not at all?

Another problem, most of the evaporators of the cheap units are inside the covering, just behind the inner walls. These are mostly foamed in the isolation of the cabinet.

Previously I had assumed that the entire evaporator
coil of small fridges was wrapped around the freezer
tray, as opposed to there being more parts to the
evaporator coil elsewhere such as inside the
fridge walls. I will have to check out some
local units (with freezer trays) to see which way
they are designed.

Second, the condenser was designed to handle a load on the evaporator of +/- 0°C (32°F). You will blow air over it much, much warmer. Can the compressor handle this and especially, can the condenser handle this very high load, again, in a very hot climate.

Hey, that's my question :) .

What's your job over there anyway because you write fluent English which seems strange for me.
I was in your country in 1999 or 2000 to visit the factory of Mitsubishi Electric. (Phuket, Patong, Phi-Phi, Bangkok as far as I can remember)

I am a software engineer by training and escaped
the US for a bizarre but rewarding life in the Thai
countryside. I am hoping that I can act as an
(albeit non-expert) bridge of knowledge because
anything I find out here I can convey to the
local non-English-speaking technicians/monkey
wrench types in the Thai language.

phil68

08-05-2006, 06:30 PM

I did this about 20 years ago when I'd just started as an apprentice. I got hold of an evaporative air cooler, the type that you fill with water or ice, gutted it & fitted a domestic fridge compressor, wound quarter tube inside a tube with a small fan on the end for the condenser with a hose that ran outside to exhaust the warm air & fitted a small evaportor in front of the existing cooler fan. It didn't work. As Peter said the compressor, condenser etc. need to to be sized for the job. A domestic fridge compressor is way too small.
The only other way I can think of doing it using a domestic fridge compressor is to cool a large amount of water overnight (do you get cheaper overnight electricity where you are?) & then circulate that cooled water through some sort of heat exchanger with a fan during the day.

The MG Pony

08-05-2006, 10:03 PM

You realize you can use propan as a refrigerant? If you got a bunch of compressers and hook them paralell and us a mix of R600a & R-290 and then use a water chiller set up like Fill said.

It can chill a room but it must be massively insulated and will take a loooooong time to cool, but once cooled it will make a nice temperary retreat from the heat.

What I put in the picture there is get three fridge compressors make a large condencer that can be air cooled, then couple some fridge evaps togeather and use any type of silver bering plumbing solder. Thing will be horidly inaefficeint by most terms but will work, use propane and isobutane as the refrigerant to charge it fifty fifty mix by weight as this will be easier for you. Use a fourth compressor to vacuum the system out and break the vacuum with propane , do that a fiew times over.

So for that all you need is 4 empty fridges, buntch of 3/8th pipe and 1/4 pipe, a drill, with 3/8 and 1/4th bits, tourtch, solder, pipe cutter, flare tool or punch (To widen tubes for soldering in odd ways), propane & butane, and lots of insulation or a mud brick room with 4foot thick walls and some more reading to learn the rest.

The MG Pony

08-05-2006, 10:20 PM

Oh and hook like three cap tubes in peralel to increas the net flow for higher capacity.

Ireland

08-05-2006, 10:20 PM

It's amazing how we take things for granted over this side of the world.

Best of luck Isemprini and I hope it works out for you.

Brian_UK

08-05-2006, 11:33 PM

Be VERY CAREFUL about using propane or butane PLEASE.:)

Things can go BANG if you make a mistake.:eek:

Also a few points on refrigeration equipment that you may or may not know so apologies if I am repeating stuff to you.;)

Inside the system must be dry, that means no air or moisture. Moisture will kill a compressor quickly, it will also block up thin pipes with ice, so, you don't want moisture.

If you do break open a system then beware of the gas. It shouldn't hurt you directly but R12, R22 etc together with a flame will produce phosgene gas and that HURTS BIG TIME.

NEVER put oxygen inside a system, it will mix with the oil inside and EXPLODE, it really will, no joke.:mad:

Ideal situation is:-

With system empty, use low pressure nitrogen bled through the pipework whenever you are brazing (soldering) a joint together. This will stop the formation of scale/oxides inside the pipe.

Nitrogen at higher pressure can be used to pressure test the system after all the bits are stuck together.

Release the nitrogen pressure and evacuate the system, yeah right he says... If you haven't got a vacuum pump then you could use a spare compressor to suck out any air/moisture from the system.

With the system under a vacuum you can then add your refrigerant back into the system.

Sorry to do this but a bit of Health and Safety was required before we go much further i think.

Cheers

herefishy

08-05-2006, 11:57 PM

The fridge refrigeration system is a low temp system. I don't suggest using it for a high temp application (directly cooling the air) - the compressor will cr*p.

Get a barrel of water and insert the evaporator into the water in order to form ice. recirculate the (cold) water from the barrel through some copper pipes (or a coil that you should be able to find from a gutted aircon) with a recirc pump. blow a fan over the cooled coils with the circulating cooled water running through it.

That would be the most effective use of your fridge to cool air.

First of all, for proper occupied space conditions - a 45degF coil is typical for 75degF at 55% relative humidty (comfortable). Any colder than that - your are wasting capacity on latent work (removal of water from air).

Do what I say - and you may have some success. You can let the unit run overnight when the conditioned air is not needed, building up an ice bank, and essentially storing the energy. I don't know if the machine will keep up without stored ice, but you can double the capacity of the machine if you only need it to cool 12 hours a day - triple it if you need it only 8 hours a day - quadruple it if you need it only 6 hours a day, etc - by storing the work in frozen water when the need to cool air is not present.

Do you have a water well on your property? Perhaps that water is cold - you can recirc that.

Cheers!

herefishy

09-05-2006, 12:18 AM

OH!

and if you're really good - you will adjust the freeze point of the (water) solution with antifreeze, glycol, or salt to lower the melt point of the water to about 10F - that would give you better coil tempertures - you might adjust the freeze point of the system in order to maximize the efficiency of the system without sacrificing capacity by obtaining unnecessarily low freezing temps.

Good Luck!

Andy T

09-05-2006, 12:19 AM

As we are knocking ideas around.What about using a Normal compressor fridge but wind the discharge pipe through a domestic Ammonia absorption Fridge were the heater normally fits, to get some free cooling.Hold on! I'm Off to the patent office.:p

star882

09-05-2006, 02:01 AM

I think the idea of storing "cold" as ice and circulating it when needed is the best idea.

Now, this thread reminded me of the time when someone in Survivor (a video system benchmark) improvised an evaporative "A/C" by using an empty coconut shell to fetch water from a nearby lake and pouring the water on themselves. Then they either relied on the wind or used some object as a makeshift fan.

Lc_shi

09-05-2006, 04:19 AM

third world ,i understand the meaning. In most of our countryside,AC is a foreign language:). In summer,it's very happy if have a electric fan. In winter, burn something to keep the essential temp. So the "free cooling "is worthy of endeavour to offer to 3rd world. I've heard that someone uses well water to cool room which consumes very little energy,it's not a bad idea. In some area, water evaporative cooler can offer cooing air for room AC. There is no real"free cooling" ,it depends what you pay for it:( Develop proper tech for 3rd world is a great work.

regards
LC

guapo

09-05-2006, 07:43 AM

Hi,

Here in the other side of the 3rd world we do not do crazy ideas like that.

Andy T

09-05-2006, 09:11 AM

What about dig a deep well with pourus walls insert an air duct to just above the water.Use a fan to draw the air from the bottom.The wicking effect and evaporation of the pourus walls will produce cooling. Or with an outer pipe led on its side sealed at both ends with a water feed filled with water.An Inner pourus pipe Draw the air though it for evaporation.

lsemprini

09-05-2006, 12:09 PM

These are all great ideas! Keep 'em coming!

Here are some thoughts I have on ideas I saw
above, both the air-cooling and water-cooling
ones:

Butane and Recharging

I myself will definitely be sticking to the options
that don't involve silver soldering, recharging
the refigerant, etc...but I can certainly pass on
any ideas in that category to any folks here
who actually have tanks of nitrogen, torches,
etc!

Blowing Air Through the Evaporator Coils

In the category of cooling the air directly with
the fridge's evaporator, many of you are
doubtful that the amount of cooling offered
would be at all useful (or that the compressor
would die if it were). Fair enough.

It occurred to me that it's not actually
that hard to try and could be done without
disassembling the fridge at all. Refining
ideas from 2 posters above, one could:

1. take a typical cube-shape dorm fridge
that has a freezer tray,
2. place it in a window with the
condenser coil and compressor sticking
outside
3. seal the whole window area around the
fridge (as well as the rest of the room!)
4. remove the door of the fridge
5. replace the door with a thick, door-sized
piece of wood, sealed around the edge of the
fridge opening with weatherstripping or
the rubber gasket from the original door.
the piece of wood has one hole (say 4 in diameter)
about where the freezer cabinet is, and one hole
(say 4 in diameter) lower down.
6. blow the warm air from the room into the top
hole (e.g. with a short corrugated duct pipe going
up near the ceiling, and a blower)
7. place some sort of baffle inside the fridge
that forces that air to move over the freezer
tray before it can escape out the lower hole.
perhaps augment the freezer tray with
fins (gee just like the 50s).
8. theoretically cool air will come out the
bottom hole.
9. theoretically the compressor will be
running continuously
10. see if the compressor gets very hot and
if so rig up some kind of air or water cooling
mechanism outside.

This method has the advantage that we don't
have to take apart the fridge, and we can take
advantage of the fridge walls' insulating properties
to keep the outside heat out.

This method also gets around the problem one
poster mentioned--that many cheap fridges have
some of their evaporator coils embedded in the
fridge wall and are hard to get out.

Freezing Water with the Evaporator Coils

In the category of using the fridge to cool
water and then blowing air over copper tubes
or a grille full of the cool water, a similar,
slight refinement of an above idea occurred:

1. start with any fridge that has a freezer tray
2. place it in a window with the
condenser coil and compressor sticking
outside
3. seal the whole window area around the
fridge (as well as the rest of the room!)
4. find the largest bucket you can that fits
inside the fridge
5. fill the bucket with water [optional: put
in antifreeze, glycol, or salt for better chillin']
6. place the bucket inside the fridge such that
the freezer tray is submerged in the water.
this may involve slightly bending the freezer
try and evaporator coils wrapping the freezer tray,
or finding a wacky-shaped bucket.
7. now rig up a small circulation pump that pumps
water out of the bucket, sneaks through the
insulation of the fridge door, leads to
a copper coil or grille attached to the front
of a fan sitting right on top of the fridge,
and then sneaks back through the
fridge insulation to empty back into the bucket.

This is essentially a fridge-powered version of
this very funny college-dorm budget aircon unit:

http://www.eng.uwaterloo.ca/~gmilburn/ac/

The advantage of this is, again, there is no
need to disassemble the fridge (much :) ) and
we can use the fridge's insulation to perhaps
keep the ice cold longer if we intend to
"store up ice" overnight and then use it
the next day.

One slight problem might be if the entire bucket
freezes and there is no water to circulate!

Why is the water-based solution better?

There is a more general matter though that
I was hoping the engineers here could explain:

At an intuitive level there's something odd about
the water-based solution: assume for the moment
that we do NOT store up ice when it's cool
out, and only run the system when it's hot out.

It seems like any time we add more mechanism
between the evaporator coils and our air, we're
just going to add heat and waste potential cooling
(from 2nd law of thermodynamics). If the
compressor would die if we tried to blow warm air
past the evaporator coils, then that means
either a. the compressor would ALSO die with
our water-based solution, or b. our water-based
solution must cool much less effectively than
blowing the air right over the evaporator coils.

Have I missed something here? Is there something
magical about going via water/ice that makes
the water-based solution overall more effective?
Something about the operating temperature ranges
of the components involved? I'd like to understand
this better.

Does the water-based solution ONLY make sense
if we also take into account the ability to
"store up cold" overnight? Or would it offer benefits
over an air-based solution in either case?

Wells, underground tubes, and thermal mass

As to using the thermal mass of the ground
to cool (e.g. via a well or underground pipes),
yes I have also considered that and of course
it's always good not to require electricity for
cooling! Some, but not all, folks around here do
have wells.

I hadn't pursued that avenue much because
I was assuming that the cooling ability
of well water would always be significantly
less than that of a fridge (which in turn
would be significantly less than a real aircon
unit), but please correct me if I am wrong
there!

--

Thanks again, keep the cool ideas coming!

phil68

09-05-2006, 05:09 PM

When you are cooling a mass of water overnight you are basically storing energy in the water, the same as storage heating but in reverse (ok guys I know you've actually removed energy from the water but this makes it easier to understand). The domestic fridge compressor is not powerful enough to cool the air directly (it will a tiny amount but not enough to cool a room sufficiently) but it can slowly cool an amount of water given time (overnight). That stored energy can then be used during the day by running the cooled water through a fan-assisted heat exchanger by day when it's needed. As someone else said you could make it even more efficient by using glycol & cooling it below the freezing point of water. That way it would still be fluid & be able to be circulated & yet be colder than using just chilled water alone.

These are all great ideas! Keep 'em coming!

Here are some thoughts I have on ideas I saw
above, both the air-cooling and water-cooling
ones:

Butane and Recharging

I myself will definitely be sticking to the options
that don't involve silver soldering, recharging
the refigerant, etc...but I can certainly pass on
any ideas in that category to any folks here
who actually have tanks of nitrogen, torches,
etc!

Blowing Air Through the Evaporator Coils

In the category of cooling the air directly with
the fridge's evaporator, many of you are
doubtful that the amount of cooling offered
would be at all useful (or that the compressor
would die if it were). Fair enough.

It occurred to me that it's not actually
that hard to try and could be done without
disassembling the fridge at all. Refining
ideas from 2 posters above, one could:

1. take a typical cube-shape dorm fridge
that has a freezer tray,
2. place it in a window with the
condenser coil and compressor sticking
outside
3. seal the whole window area around the
fridge (as well as the rest of the room!)
4. remove the door of the fridge
5. replace the door with a thick, door-sized
piece of wood, sealed around the edge of the
fridge opening with weatherstripping or
the rubber gasket from the original door.
the piece of wood has one hole (say 4 in diameter)
about where the freezer cabinet is, and one hole
(say 4 in diameter) lower down.
6. blow the warm air from the room into the top
hole (e.g. with a short corrugated duct pipe going
up near the ceiling, and a blower)
7. place some sort of baffle inside the fridge
that forces that air to move over the freezer
tray before it can escape out the lower hole.
perhaps augment the freezer tray with
fins (gee just like the 50s).
8. theoretically cool air will come out the
bottom hole.
9. theoretically the compressor will be
running continuously
10. see if the compressor gets very hot and
if so rig up some kind of air or water cooling
mechanism outside.

This method has the advantage that we don't
have to take apart the fridge, and we can take
advantage of the fridge walls' insulating properties
to keep the outside heat out.

This method also gets around the problem one
poster mentioned--that many cheap fridges have
some of their evaporator coils embedded in the
fridge wall and are hard to get out.

Freezing Water with the Evaporator Coils

In the category of using the fridge to cool
water and then blowing air over copper tubes
or a grille full of the cool water, a similar,
slight refinement of an above idea occurred:

1. start with any fridge that has a freezer tray
2. place it in a window with the
condenser coil and compressor sticking
outside
3. seal the whole window area around the
fridge (as well as the rest of the room!)
4. find the largest bucket you can that fits
inside the fridge
5. fill the bucket with water [optional: put
in antifreeze, glycol, or salt for better chillin']
6. place the bucket inside the fridge such that
the freezer tray is submerged in the water.
this may involve slightly bending the freezer
try and evaporator coils wrapping the freezer tray,
or finding a wacky-shaped bucket.
7. now rig up a small circulation pump that pumps
water out of the bucket, sneaks through the
insulation of the fridge door, leads to
a copper coil or grille attached to the front
of a fan sitting right on top of the fridge,
and then sneaks back through the
fridge insulation to empty back into the bucket.

This is essentially a fridge-powered version of
this very funny college-dorm budget aircon unit:

http://www.eng.uwaterloo.ca/~gmilburn/ac/

The advantage of this is, again, there is no
need to disassemble the fridge (much :) ) and
we can use the fridge's insulation to perhaps
keep the ice cold longer if we intend to
"store up ice" overnight and then use it
the next day.

One slight problem might be if the entire bucket
freezes and there is no water to circulate!

Why is the water-based solution better?

There is a more general matter though that
I was hoping the engineers here could explain:

At an intuitive level there's something odd about
the water-based solution: assume for the moment
that we do NOT store up ice when it's cool
out, and only run the system when it's hot out.

It seems like any time we add more mechanism
between the evaporator coils and our air, we're
just going to add heat and waste potential cooling
(from 2nd law of thermodynamics). If the
compressor would die if we tried to blow warm air
past the evaporator coils, then that means
either a. the compressor would ALSO die with
our water-based solution, or b. our water-based
solution must cool much less effectively than
blowing the air right over the evaporator coils.

Have I missed something here? Is there something
magical about going via water/ice that makes
the water-based solution overall more effective?
Something about the operating temperature ranges
of the components involved? I'd like to understand
this better.

Does the water-based solution ONLY make sense
if we also take into account the ability to
"store up cold" overnight? Or would it offer benefits
over an air-based solution in either case?

Wells, underground tubes, and thermal mass

As to using the thermal mass of the ground
to cool (e.g. via a well or underground pipes),
yes I have also considered that and of course
it's always good not to require electricity for
cooling! Some, but not all, folks around here do
have wells.

I hadn't pursued that avenue much because
I was assuming that the cooling ability
of well water would always be significantly
less than that of a fridge (which in turn
would be significantly less than a real aircon
unit), but please correct me if I am wrong
there!

--

Thanks again, keep the cool ideas coming!

herefishy

10-05-2006, 04:26 AM

I was assuming that the cooling ability
of well water would always be significantly
less than that of a fridge (which in turn
would be significantly less than a real aircon
unit), but please correct me if I am wrong
there!

--

Thanks again, keep the cool ideas coming!

if the well water is <45degF - that is what you are looking for - ideal.

Peter_1

10-05-2006, 06:46 AM

if the well water is <45degF - that is what you are looking for - ideal.
Herefishy, we did some drills and the temperature from 10m (30 ft) till 30 m (100 ft) is almost the same in teh wole world: 12°C (55°F), but still usefull for cooling.
Make some holes and insert copper pipes in it and circulate on it with a pump through a coil.

This will work better then a fridghe (which will never work)
You asked: what will be the effect with the fridge...well...temperature in teh room will perhaps drop from 35°C(95°F) to 34.7°C (94.5°F)
Does it cool?
But, you will feel some cold coming out the fridge but the effect on the room will be zero. And I think it even won't drop, it will only dry a little bit.
First thing you have to do if you only have a small capacity available is isolate the place very, very good.

lsemprini

10-05-2006, 05:54 PM

Herefishy, we did some drills and the temperature from 10m (30 ft) till 30 m (100 ft) is almost the same in teh wole world: 12°C (55°F), but still usefull for cooling.
Make some holes and insert copper pipes in it and circulate on it with a pump through a coil.

This will work better then a fridghe (which will never work)

Interesting.

Can you make an estimate of how the temperature
changes between the surface and 10m in a tropical
climate? I wonder what the benefit in terms of
degrees is for each additional meter that we dig down
(and 2 meters of pipe that we purchase)? Is it
roughly linear from the surface air temperature down
to 12C at 10m?

The reason I ask is: the cost of the pipe starts
to possibly be relevant because for some reason,
copper pipe here is crazy expensive (USD $1.32 per
meter ($0.40/foot) for 10mm (3/8") od pipe) as
opposed to about $0.38/meter for uPVC pipe.
Galvanized is also much less than copper but I didn't
check the price recently. I think the reason is
that nobody has public natural gas or public potable
water service here, so nobody has any reason to use
copper pipe except for the "rich folk" with aircon!

What other materials would work nearly as well
as copper pipe? I can go check the price
for them.

How much worse would uPVC be than copper pipe?

lsemprini

10-05-2006, 06:06 PM

Ah, and here's question #2 about the undeground
pipes:

It's more of a construction question than an
engineering question.

Anyone have any good suggestions on how to dig a
10m+ deep hole, big enough to fit two pipes side
by side, without special drilling equipment?

For those people who do not have existing
wells, or whose wells are too shallow, I believe
that the cost of renting out the customized
well-finding and well-digging machines which
periodically pass through town would be
prohibitive.

I am assuming, but haven't actually confirmed,
that the technique of manually pounding some
object like a metal pipe into the ground will not
work after you get a few meters deep. But maybe
there's some simple trick I don't know of to
make this work.

I haven't asked any locals here about this yet;
for all I know they might have some cool
technique involving bamboo and a coke can :)
But I thought I'd ask the engineers as well.

Peter_1

10-05-2006, 06:34 PM

http://www.dimplex.de/downloads/download.php3?file=handbuecher/projektierungshandbuch-wp-kuehlen/PHB_WP_Kuehlen_Jun05.pdf&download_bezeichnung=Handbuch%20WP%20Kuehlen

See page 8,

Andy T

10-05-2006, 11:15 PM

It's a bit more complex than that.You will have to go down to 10m with any pipe plastic would be best.Then at 10m you would need a coil of good thermal transfer pipe like copper.This will allow the warm water to tranfer it's heat before returning to the surface.If it was straight up and down the water would cool on the way down and warm up on the way up with no net effect.

Andy T

11-05-2006, 12:01 AM

The size of the coil would depend on the amount of cooling you would require.Also other factors would be the heat transfer.The poorer the heat transfer of the ground or coil material the longer the pipe must be.If the ground around was pourus it may be posible to pump the water out the ground at the water table.Run that through a coil in the room and then dump the waste water into another hole or fields to return it to the water table some distance away.Try getting the temp of the water that comes from your nearest well and see if it is lower than ambiant it should be at least 5C lower to be any good.Would the well run dry if you tried to pump water out at a flow rate that the water leaving the room coil was equal to the room temp and let the waste run into another well metres away?You could experiment with two holes a distance apart down to the water table with a gravel filled trench running between to let the water flow.Cover the gravel with normal soil.pump water from one hole.let the waste down the other allow the water to flow underground through the gravel,cooling as it moves along underground, to be pumped up again.

cryptojoe

12-05-2006, 12:58 AM

lsemprini

12-05-2006, 04:36 AM

A Fresnel (pronounced frhttp://cache.lexico.com/dictionary/graphics/AHD4/GIF/amacr.gif-nhttp://cache.lexico.com/dictionary/graphics/AHD4/GIF/ebreve.giflhttp://cache.lexico.com/dictionary/graphics/AHD4/GIF/prime.gif - or - FRAY-NEL) lens could help you to prevent pumping the guts out of that little compressor. All it takes is a little sunshine, caution, and experimenting. I can tell you where to get them for nothing.

Email me some rough sketches of the rooms floor plan, with window dimensions and height off the ground, position of where magnetic north is at and the nearest city and I can then do some work in Rhino and possibly come up with some inexpensive solutions to use solar heat as your friend. You can move fluids with heat. Both Air and Liquids are Fluids.

This is very do-able. Gosh, it makes me which I could get to Bangkok.

sounds intriguing!

in general, how can one use the heat of the
sun to cool (other than lots of expensive solar
electricity panels which not even the rich folk
can afford here)? what would one use the
fresnel for? something to do with boiling water?

this is potentially for many folks here in this
mountainous region of northern Thailand
including cities such as Mae Hong Son,
Soppong, Pai, and Mae Malai.

These cities are hard to find with Google Maps!

Pai is at 19.3167N,+98.4500E, altitide 1597 feet.

http://maps.google.com/maps?f=q&hl=en&q=19.3167N,+98.4500E&ll=19.316732,98.450031&spn=0.047708,0.099993&t=h&om=1

for starters you could just assume some idealised,
simple room/window conditions, to give us some
idea of what you have in mind.

Peter_1

12-05-2006, 05:52 AM

Cryptojoe,there are some naturelaws you can't change which excists since the beginning of earth.
But I'm eager to learn and listen.
Because your idea is patented, provide us the the patent number and we can have a look.

You ran out of DVD's, why not post a free link on the net:confused:

Looked onc to your artist site, well...very nice made.

cryptojoe

12-05-2006, 06:00 AM

Okay, when you turn on an AC unit some form of a pump comes on to produce pressure on a fluid. Pressure and temperature rise at a constant rate to one another. This is why it takes less electricity to cook using a pressure cooker.

Here's an experiment you can try to prove this. Its a little trick I learned in the Army as a combat engineer which also proves that the suns core is ice.

If you can still find a clean, metal 55 gallon drum/barrel, put a case of Pepsi or Beer in the bottom of the drum. Fill it to about 20 Centimeters from the top with water.

Now find some old used motor oil nobody wants, enough to fill the rest of the barrel another 10cm or sop (its not an exact science experiment). Now put about 1 cm of gasoline on the top, and carefully set the gasoline on fire in a safe manner, like a long stick with a rag and lighter fluid on it.

The gasoline will set the very high octane motor oil ablaze. This will take awhile so, sit back and watch, making sure nothing else catches fire.

After it stops burning, reach down to the bottom and grab one of the drinks. You will notice it is ice cold, and should frost right over. Hurry and open it or else it may freeze!.

How did that happen???

Gasoline burns at a lower temperature, therefore it is a lower octane than motor oil. The motor oil then super heats the top of the water it is floating on, causing it to boil. As the steam is released into the oil, hydrogen and oxygen separate and feeds to fire even more.

As the water rapidly evaporates, it gives off the latent energy stored in it. Heat is energy. The lack of energy is cold. So as the water gives off its stored energy (heat) the bottom of the water becomes cold.

I'm sure there are very complicated or even simpler ways to describe this action. but even if you do not do this experiment, it simply describes how nature tries to balance things out, first by giving off the stored energy in your warm water (before you started the fire) and the reaction at the bottom of the barrel as the energy is sucked out of it.

This is a simple demonstration of "Hot Side - Cold Side" principle of AC.

Now, once you get a good grip on how to use heat, you can use this same principle to cool your home. There is a cooling effect to evaporating water. But it is limited to the relative humidity of the ambient air. In humid climates an air-conditioning unit cools in two ways, one by the cold air itself, the other by removing water from the air.

If you need energy at the cheapest price available, always remember the term "Solar Thermal Dynamics."

Does you community have a public library? If so, find if they have a book on Air Conditioning/Refrigeration they are both the same. If you understand why they work, you will better understand how to make the energy we call heat, work for you instead of against you.

Also remember that one of the best places to find the parts you need for refrigeration can be found in the automobile junk yard. Compressors, collectors, condensers, tubing, orifice, its all there just waiting to be cobbled back together and given a second life, to be liberated and resurrected.

Andy T

12-05-2006, 09:00 AM

I have got to try that at my next BBQ :cool:

Abe

12-05-2006, 09:09 AM

Ive just stumbled on this thread, very interesting..........

cryptojoe

12-05-2006, 09:40 AM

Be warned Andy, I don't want your wife coming back and suing me if you blow yourself up. If you've ever deep fried anything and put water into oil and watch as it hydrogenates (makes snapping and popping sounds) stand back!!! Its not an exact science, its crude but it works.

Mind you, the first time I did it was under the directions of a man 5 years older than me and fresh back from Viet Nam (right over there in Siam, that is next to Thailand). We didn't take out a tape measure and the last time I did this was way back in 1979 at the ripe old age 21, so, use caution. It does work for Texas Lone Star in the Long Neck bottle, but my proportions may be off a tad.

As my attorney might (meaning I ain't practicing law without a license) say; "This information is provided for entertainment purposes only"

ROFLMAO!!!!

lsemprini

12-05-2006, 12:02 PM

Hi,

Cryptojoe,there are some naturelaws you can't change which excists since the beginning of earth.
But I'm eager to learn and listen.
Because your idea is patented, provide us the the patent number and we can have a look.

You ran out of DVD's, why not post a free link on the net:confused:

Looked onc to your artist site, well...very nice made.

For those reading this thread who are now
as confused as me, Peter_1 was referring to
this thread:

http://www.refrigeration-engineer.com/forums/showthread.php?t=4706

where cryptojoe introduces himself and says:

I really don't want to be known as a Professional Inventor, inventors are like starving artists. Being on the back side of forty, disabled, ill health and so forth, I need a way to keep patents, copyrights on works and inventions; so, I formed a Nevada LLC (Limited Liability Company) with my wife and I as the principles.

I call it Dynamic Earth because I deal primarily in Solar Thermal Dynamics. PV Cells will never pay for themselves as long as nothing more than 14% efficiency can ever be reached.

I've produced an animated video I called "Energy Through Resource Reclamation." I'm running low on DVD's and will need to get another batch made up soon. I'll be sure to make some kind of an announcement when they become available again.

cryptojoe, if you send me one DVD I can make an
internet streamable movie file for you, which
you can host on your website.

in the meantime, after tempting us with that,
what more can you tell us about a technique that
might work in this remote environment?

Andy T

12-05-2006, 03:06 PM

OK I understand,I'll stick to a fridge so I won't lose my eye brows . I can just see a fireman throwing cans of beer into a petrol fire somewhere before they put it out so they could have a chilled beer after.:-)

The MG Pony

13-05-2006, 05:39 AM

You are miserably wrong on solar cells, now days the repay rate is oft less then ten years total energy is not only fully returned but continue to return 100% pollution free energy. I put too much energy in researching solar cells to allow such a claim.

Links >
Search terms "Solar Cell payback Data"
Links:

- http://en.wikipedia.org/wiki/Solar_cell (Basic explanation of current data )
- http://www.csudh.edu/oliver/smt310-...n/pvpayback.htm < Dead link
- http://www.ecotopia.com/apollo2/knapp/PVEPBTPaper.pdf (Download of PDF) < Works
- http://www.ecotopia.com/apollo2/pvepbtne.htm < Works
- http://www.greenbiz.com/news/news_t...FTOKEN=97796295 < Dead

I really don't want to be known as a Professional Inventor, inventors are like starving artists. Being on the back side of forty, disabled, ill health and so forth, I need a way to keep patents, copyrights on works and inventions; so, I formed a Nevada LLC (Limited Liability Company) with my wife and I as the principles.

I call it Dynamic Earth because I deal primarily in Solar Thermal Dynamics. PV Cells will never pay for themselves as long as nothing more than 14% efficiency can ever be reached.

I've produced an animated video I called "Energy Through Resource Reclamation." I'm running low on DVD's and will need to get another batch made up soon. I'll be sure to make some kind of an announcement when they become available again.

As for the barrel Idea it makes sense and when I have the time I will test it and will post the results

Fixed quote = Upper part of peragraph got omited

cryptojoe

13-05-2006, 06:34 AM

Have solar cell reached more than 14% efficiency? If so, this is a very recent development, and I stand corrected. I often forget about the recent rises in electrical prices which I suspect may have allot to do with lowered costs, unless production of PV's has increased.

Don't get me wrong, I use solar cells to trickle charge my electric lawn mower. I am in the process of changing over many of my ambient lights to LED's which draw little power compared to a conventional bulb and could run my LED's, but the cost of the battery systems is a large drawback.

Sorry for going way off topic and hijacking the thread.

I'll check the links and give you many thanx for the reference materials.

lsemprini

13-05-2006, 07:37 AM

The MG Pony

13-05-2006, 10:34 AM

(Solar cells have gotten to 26% and some rather insanely expensive ones have gotten 36% or so)

Sorry for the lack of info guys twas insanely tired.

36% is max theoretical Ideal situation with the current high end cells, not very applicable to this discussions context

How ever the 26% is the Current high end applicable Cell rate, IE it is usable for the home owner.

So in the end: 26% In Field use and currently mass manufactured

36% Space and or Highly optimized situations and in the lab using the very tip of high end technology

cryptojoe

13-05-2006, 10:36 AM

"Are you envisioning some kind of clear tube where the fresnel is used to boil water at one end?"

No, no! The barrel thing I discussed was meant to demonstrate the Hot End/Cold End principle, how cooling can be produced by very crude means.

The reason for telling you about the Fresnel Lens was because I'm certain that you can find them manufactured over there relatively cheaply. You may even be able to pick them up used for nothing if you can find a television repair shop nearby.

If you had a Fresnel Lens like the ones used in big screen projection television sets or the smaller ones used in flat screen TVs, you could set up a passive solar heater to assist in heating up the hot/high pressure side of your refrigeration unit and relieve some of the work on your compressor, thereby reducing your total electric consumption for the unit as well.

Provided you supplied your snail-mail address in your reply to me, I will be sending a book written by a man who assisted an impoverished man and his family in Haiti to make a portable refrigeration unit mostly from scrap materials, that he now uses to make ice, and, thereby, make an income to support his family with.

As I mentioned in my reply to your email, I am married to a Korean woman I met while serving inside the DMZ between the north and the south. I fully comprehend the poverty of a third world nation.

However, compared to Haiti, Thailand is a paradise. At least you have a stable government, and currency.

So, make sure to give me that reply with snail mail address, and you can expect some information you can sink your teeth into. You never know, if you are determined and work hard, you could wind up becoming a mogul of sorts in your own community. By asking questions here, you are definitely on the right track.

When stationed in Korea as an Engineer, we had a motto that went like this:

"We the willing, lead by the unknowing; doing the impossible, for the ungrateful; have done so much, with so little, we can calculate the day when we shall be able to do positively anything with absolutely nothing."

Andy T

13-05-2006, 03:02 PM

"We the willing, lead by the unknowing; doing the impossible, for the ungrateful; have done so much, with so little, we can calculate the day when we shall be able to do positively anything with absolutely nothing."
Sounds like the last contract I bid for :)

US Iceman

13-05-2006, 04:09 PM

It also sounds like an ex-bosses opinion of what we should have been able to accomplish in R&D.:p

cryptojoe

13-05-2006, 08:17 PM

Roflmao!!!

tsangep

14-05-2006, 01:27 PM

It may be more efficient to go to the comercial equipment junk yard and find a few large machines which has been discarded and build one good one. If your lucky you may be able to find a fully working split system which someone has thrown out because the computer is unserviceable. The compressor and fans can simply be connected straight to the power supply.

Darshi

17-06-2006, 03:48 AM

Friends,there could be another way of reducing the load on the fridge.
I live in Thailand for last 6 months.Most of the people in places like SriRacha put on the air con for sleeping in the night.During the day it is mostly the table fan or padestal fan.

Third world homes are not built for coling or heating.So let us not cool the whole building instad cool the sleeping place.If one can use the insulated cover instead of Mosquito net ,the space is reduced to let us say 6 X 5X 4 ft a volume of 120 cft.Typically in tropics the one tonne air con handles a 1200 cft room and two occupants.So we need a system 10 times smaller for the bed.say 120 btu/hr .The refrigerator will do the trick

I have designed an AC bed for an indian TV show it may be aired in about two to three months.
There is no need to cool tons of brick and mortar ,when all you need is removing less than 400 btu per hour (two peple sleeping)

I am planning to offer the product as a "head borad Air Con"containing refrigeration system using automotive components and a refrigeration compressorhere in thailand ,it will cost less than damaging a fridge and experimening.May be made as akit that people can assemble DIY

I am using an air to air heat exchanger to bring in fresh air and reduce the internal load by heat recovery

Dan

17-06-2006, 09:42 PM

head borad Air Con"containing refrigeration

Head board air conditioning strikes me as ingenious, Darshi. I would love to see some pictures or sketches of it someday. What automotive parts are you going to use, the evaporator and condenser?

DeB

18-06-2006, 02:35 AM

As a frequent visitor to Korat province (visiting again shortly after my visit to China even more shortly)I am well aware of the technologie problems and also the heat. Domestic fridges generally have a small, low starting torque motor due to the low evaporating temperatures of most domestic fridges.Trying to run this at high evap temperatures will eventually overload the motor. Rather than revamp a fridge to do what it was not designed to do.I would look at another method. Maybe putting a watertank in the fridge attached to a simple coil and fan with a pump, using the refrigerator to build a large icebank overnight and then recirculating water through the tank and coil to produce cooling.The cool condensate could be piped back to the tank to offset evaporation in the tank and therby reducing the cooling time needed to cool ambient water. Reinsulating the fridge with some cheaper local source EG saw or of granulated rice husks? maybe would reduce heat transmission through the cabinet and increase unit efficiency as would limiting air ingress and water vapourization. This will decrease the latent load and increase sensible heat transfer. Obviously the fridge would need to operate as as a freezer.

Darshi

21-06-2006, 03:39 AM

Dan
NO unfortunatly they are over size for he application.On a second thought ,I may be able to use the evaporator as a condensor perhaps. I am looking at using air con blower motors to have smooth speed control and also manage the pressure drop across the evaporator coil without getting into too much of calculations.
I also plan to use wind shield washer pump for indirect evaporative cooling of exhaust air by saturating it to near the ADP. That way ,we have 100% fresh air .
The latent heat removed by the evaporator is converted to condensate and I plan to use the condensate to pre cool the fresh air after the heat recovery module but before the evaporator. I expect 20 to 30% saving in the capacity of te cooling unit at the steady state conditions.Here again I plan to use wind shield washer pump for direct evaporative cooling,above the system ADP.The pump will go off automatically ,when the ambient dew oint is higher than the space dew point.

Please give suggestions to improve my thinking .I will have the protos ready in 2 months or so and will surly post the images on our site .

US Iceman

22-06-2006, 12:32 AM

Why not knock a hole in the wall the size of the fridge, stick the fridge in it so the coils are on the outside, open the door off the fridge and place a fan in front of it. You can still use as a fridge when not needed to cool the room

That is about the same as telling someone to live in a reefer container to have air conditioning.:rolleyes:

Darshi

22-06-2006, 09:06 AM

what motive power the farmers use in this area?
Oxen ,Horsesor tractors?

cold stratum

13-08-2006, 08:28 PM

Watering the condensor will scale it up, if you use untreated water, within weeks!

I think you don't have enough cooling capacity, you will build just a de humifier with this setup.

The superheat will be to big, and therefor it will cool the compressor unefficient.

Sorry i don't see it work, in the conditions you set.

cold stratum.1111

Darshi

26-11-2006, 06:05 AM

Head board air conditioning strikes me as ingenious, Darshi. I would love to see some pictures or sketches of it someday. What automotive parts are you going to use, the evaporator and condenser?

Dan,
Thanks for the encouragement :D
My bed air con was assembled last week .
I will be doing some trial runs for an other week .
Should be able to post pictures and some performance data .
look forward to help from every one on the RE , for improving it further.

TSK

03-12-2006, 05:19 PM

Domestic fridges work at freezing temperatures, so the simplest suggestion I can think of is to strip several down as someone as already suggested and place the evaprators in an insulated tank of water, if there is enough capacity in the fridges you have available the water should start to freeze around the coils making blocks of ice. The ice would provide stored cooling effectivly. You would then need an old blower coil from a small coldroom to pass the water through. Limited effective running time but that depends on how large the tank is and how many fridges you can get hold of and manipulate the tubing, domestic fridges tend to have aluminium pipes which break easily. Best of luck.
Have you got a stream nearby that you could build a water wheel to drive an open type compressor from a comercial type unit, then you would have a much better chance with lots of btus at your disposal.
People in England are adapting water wheels to power homes, bit radical but if you have water power you might as well use it.

Lan1

05-01-2007, 12:19 PM

If the idea is for a sleeping area then two fridges hacked and joined would make a sleeping area, approapriatly vented with pre cooled air with light and escape built in it should be a comfortable sleeping bag

Doug

Lan1

05-01-2007, 12:24 PM

the idea about pulling water sounds good, small electrical conduit would be suitable for this with a pond pump or similar the Asian electrical conduit I have used was very thin but would be usefull , you may need to aquire the glue from somewhere else though as my experience is that glue as not used in Asia (Indonesia)

fridge doctor

10-06-2007, 08:04 PM

As our USA friend Pethereshy (apologies if name is wrong) suggests, stick to the water cooling principle. If as the last post suggests most people cope during the day and can manage with a cooler sleeping area, then storing cold water during the day is the answer. You can use any number of old fridges (stripped) and dunk their evaps into whatever tank you can lay hands on in order to pump the tank water through a fan coil of some sort (old car radiator, old fridge condenser... whatever). Glycol may be a problem for you, if so use the cheapest alcohol to enhance the water properties. Key points to remember are

Keep the fridge compressors cool - trickle droplets of water on them if you have to (away from the electrics of course)
Likewise the condenser, if the exit of the condenser (opposite end from where the compressor discharges) is hot, you need help. Cool it down to at least lukewarm. Use the chimney principle mentioned elsewhere, or water again (depending upon your water situation).
Insulation - The tank you choose.... Insulate it, and the pipes leading to/from the cooling coil. Use whatever materials are available... Old woolens if you must, Get the tank up to 10 inches thick and the pipes at least 5 inches.
Keep the cooled space small, and as well insulated as is practical.If your tank is big enough, you can always add another fridge or two as they become available at the right price, and as needs dictate.

Finally, just a thought which may not be relevant...

The usual method of cooling draught beer or dispensed soft drinks, is by passing the beverage through a 'flash cooler'. Small fridge unit, sits behind bar, or larger unit located in storage area. Perfect for the job, already contain all the ingredients you need, water tank, circ pump, cooling coil etc... just add fan coil and water pump and you're in business. These things are thrown away with abandon in some parts of the world, but I suspect not where you are.. Good luck.

Sledge

13-06-2007, 10:33 AM

I would lie the fridge on its back, plugging up the drain holes.
-First carefully move the compressor so that it will sit upright before the fridge is laid down. Be careful not to break the pipes
-Move the condensor onto one side of the fridge and refasten it there. If the condensor is the type that is built inside the outer shell (so that it is inaccessible) I would put a couple of sleepers down, and lay the fridge on that. This will allow some air flow around the condensor under the fridge
-leave the evaporator in place
-disconnect the fan and all the electric controls, wire the compressor direct to a plug/source.
-Fill the fridge with water.
-Hook up a pump that will draw the water out of the freezer section and pump it through an air coil with a fan in the room you want to cool, and circulate the water back to the fridge.
-Keep the door on the fridge and close it to keep out the heat.

One fridge will not have the capacity to achieve what you want, so do this with a lot of fridges, and fan coils.

The important issues will be
-dont break the pipes
-plug all the holes well
-good water circulation...freezing the coil is not what you want, ice is an insulator, aim for lots of water moving around the evaporator
-the condensor must be kept cool as possible, so shade would be good, air movement important, or ...perhaps put condensor in its own containor full of water, if available, (pond)
-

Sledge

14-06-2007, 05:26 AM

If you decide to try this, I would do one thing different;

Draw the water as far from the evaporator as possible, and direct the warm return water directly at the evap, to try and keep the evap from freezing up.

Darshi

14-06-2007, 01:03 PM

Excellent Sledge!:)
You can add 10% glycol to the water so that it does not freeze.Now you can keep the fridge "on" without fear of freezing.
It will also act as Thermal Storage .

theboss

23-06-2007, 01:24 AM

heat gained = heat lost is the principle of energy. A fridge compressor even charged with R290 will take days to lower temp by few degs.

kubae

27-06-2007, 08:43 PM

I've been building Ice block makers for awhile now. First as a Graduate student, and now as a business. Your climate is more humid and thus less friendly than even Nigeria. Whist this last idea is theoretically beautifully, it can't work using a fridge "as it comes". Reason: I use 2 (two) 2HP compressors to build ice (about 320 liters of water). In the first say, hour of operation, I noticed that the compressors were being overloaded. They survived if there was no power cut since the suction cooling kept coming. If there was a power cut, the internal components overheated and overloaded causing compressor failure. So I increased evap temp to reduce the load (BECAUSE I DESIGNED THE SYSTEM). Your case seems more complicated as the idea is that your evap sits right inside your water (thus drawing ALL the heat it could) yet you are using already designed evap temps.
Your water (what quantity will fill the fridge?) will enter the fridge initially at above 100F???. The evap will have to transfer the heat through the compressor (fridge = 1/x HP compressor) which will definitely overload.
But if you could reduce the evap temp so that there is less heat transfer, you might be able to keep the compressor alive. Note though that this means you make your ice slower or you start with already "iced" water. Plus if you really utilize the fan and cooling pipes, your returning water will be at much "hotter" temp adding to a really small compressors load. If you have power cuts, this idea won't last one summer day.