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Author Topic: How does a propane-powered camping refrigerator work?  (Read 37211 times)

Zsolt Munoz

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Zsolt Munoz  asked the Naked Scientists:
   
Hello Naked Scientists,

My name is Zsolt Munoz from Airdrie, Alberta, Canada.  I listen to your various podcasts everyday on my way to work and have really enjoyed them and share my learnings with my wife all the time.

Recently we purchased a travel trailer RV with a propane powered air conditioning unit and refrigerator.  I was wondering how does this work?  I remember learning about heat transference in school but I cannot remember how this works exactly.  I am not sure if this is what is actually occurring in this case.  Could you please shed some light on this for me?

Thanks,
Zsolt & Janice

What do you think?


 

lyner

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How does a propane-powered camping refrigerator work?
« Reply #1 on: 05/06/2009 14:04:08 »
Any refrigerator uses energy to pump heat from one place to another  (from the inside to the outside). The easiest one to describe uses a motor. Most fridge units use a compressor which compresses a gas (the refrigerant), this gets it hot. It circulates round the external cooling pipes and its temperature drops to room temperature. The gas then is allowed to expand through a nozzle, and drops in temperature, as a result - it may even condense into a liquid. It is then circulated around pipes inside the cold compartment, cooling the fridge down and raising the temperature of the  refrigerant. It then goes through the compressor and round the cycle again.
So you have used some Energy (in this case, electrical) to circulate a substance and the process will transfer heat. Using a compressor can be quite efficient - just a bit noisy at times. Air conditioners use the same system.

If you have no ready supply of electricity you can use an alternative system called an Absorption Refrigerator.
http://www.ehow.com/how-does_4572467_rv-refrigerator-work.html
In this case, you use the circulation of one substance to drive another substance, the refrigerant, around. The circulation is, basically, convection, which is driven by a heat source. It isn't as efficient as one with a compressor but it is better than nothing.
I had one in a Camper Van; it used three alternative heat sources: a gas flame, a mains heater and a 12V heater which you could only use with the engine running (or you'd flatten the battery).
Another link is here http://images.google.co.uk/imgres?imgurl=http://www.expeditionportal.com/equipment/equipment_reviews/fridge/Research/Research/smaller/fig1.gif&imgrefurl=http://www.expeditionportal.com/equipment/equipment_reviews/fridge/Research/index.php&usg=__0p7_1fXZwPhUcVt_HZ3nZmkFbeg=&h=425&w=420&sz=46&hl=en&start=6&um=1&tbnid=hPJ6YREVygskjM:&tbnh=126&tbnw=125&prev=/images%3Fq%3Dhow%2Bdoes%2Ban%2Babsorption%2Bfridge%2Bwork%26hl%3Den%26client%3Dfirefox-a%26rls%3Dorg.mozilla:en-US:official%26sa%3DN%26um%3D1
« Last Edit: 05/06/2009 18:32:51 by sophiecentaur »
 

Offline nicephotog

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How does a propane-powered camping refrigerator work?
« Reply #2 on: 06/06/2009 18:47:51 »
Three states of matter, Solid Liquid and Gas in between Gas and Liquid is vapour, but thats mor alike isotopes and chemical properties.

The point is that all matter , rocks , crystal , metal , water at room temperature is simply with the property of being a solid , a liquid a gas.
But that can change state with temperature change.

The easiest way to explian that point, is comparing propane alike boiling water in the property and behavior it has when heat is being transferred
or lost during a change of state from one state (e.g. water changing to steam , liquid to gas)  to another.

When scientists measured how much energy it took to heat water to 100 deg. centergrade (boiling point) they noticed it took a particular quantity
of time to change from 1 degrees of centergrade and a continually the same quantity of energy step after step per time unit.
But when it reached 100 degrees, for all of the quantity of water to change state required a much longer time and much more energy for the same
quantity of water to be gas.
To change state from liquid to gas at that point only and mantain gas state requires it to take in heat or the substance (this instance water)
cannot change state(that heat section they refer to as latent heat).

Waters boiling point is 100 deg. centergrade
Propanes boiling point is around -44 degrees centergrade at atmospheric temperature.
(anyone want to add Kelvins and pressure?)
When it is induced under pressure(compression) in an artificially created environment (pipes and reservior), it changes state to liquid.
When gases are compressed to liquid state they give off heat(the opposite of boiling) to change state.
The pump system in refrigeration commits a rise and fall of pressure on either side of the reservior in grid of low pressure (boiling heat reciever) side
Then pumped into the outside grid pipe set to cool them on the other side (High pressure reservior compressing side).
The mass area the fillaments of pumping pipe grid wrapped around the inside of the fridge have the ability to absorb the heat and then is drained into the
reservior side set and cooled to atmoshpere then re compressed to the reservior.
And so the cycle continues pumped around and around.
« Last Edit: 06/06/2009 19:02:28 by nicephotog »
 

Online Bored chemist

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How does a propane-powered camping refrigerator work?
« Reply #3 on: 06/06/2009 19:37:50 »
I'm fairly sure that this page
http://en.wikipedia.org/wiki/Absorption_refrigerator
will be more use than that last post of word salad.
 

lyner

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How does a propane-powered camping refrigerator work?
« Reply #4 on: 06/06/2009 23:14:37 »
nicefhotog
They just BURN the propane as the source of energy for the process. It is a rubbish refrigerant.

btw, Is your post a Scientific explanation or some sort of free verse?
 

Offline nicephotog

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How does a propane-powered camping refrigerator work?
« Reply #5 on: 07/06/2009 08:42:53 »
 
Quote
I remember learning about heat transference in school but I cannot remember how this works exactly.


Says he does not comprehend the system of state change of matter.
No word salad is it.

As anyone who knows anything from tech college
(not a brat exposed to millionaire level vacational quirks that could know about burning propane as a use in a process but it does not comprehend)  the high pressure and low pressure sides for latent heat or how a compression ignition engine operates either)
with automotive skill knows these types of yhings in some way at least.



re:http://en.wikipedia.org/wiki/Absorption_refrigerator
Both absorption refrigerators and compressor refrigerators use a refrigerant with a very low (sub-zero Fahrenheit) boiling point...


At -44 boiling point that makes propane quite possible to use as a refrigerant.

For the final time the person did say they did not have a good understanding of the use of pressure and latent heat as cooling or heating principles ANYHOW.
But thanks for the information on the drive mechanism betwixt high and low pressure sides in http://en.wikipedia.org/wiki/Absorption_refrigerator

In Australia CSIRO did a study in the late eighties on cold storage and found that warehousing fruit and other perishables was better done above freezing for supply and physical preservation of the foodstuffs, but that system used water evaporative cooling.
Refrigeration science is one of the most important unavoidable subjects to people in Australia as Black Saturday recently attested when Australia become the record holder for the hottest place on Earth. Anyone whom can think of a way here (such as bush fridges and small cans of fuel buried in the ground and shaded from the sun with another sealed can  inside) have a point to being here in this environment. The ways thought of here are endless.
« Last Edit: 07/06/2009 09:27:15 by nicephotog »
 

lyner

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How does a propane-powered camping refrigerator work?
« Reply #6 on: 08/06/2009 00:02:08 »
A 'Propane Powered Fridge' uses Propane as a fuel - in common practice.
If someone asks a simple question on these forums, they normally need a non-confusing answer. That's it.

The refrigerant in such fridges is ammonia.

I would suggest a separate thread if we want to talk about unusual refrigerants.
« Last Edit: 08/06/2009 00:04:03 by sophiecentaur »
 

Offline nicephotog

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How does a propane-powered camping refrigerator work?
« Reply #7 on: 08/06/2009 05:29:41 »
So your saying you should have simply written.

Propane is not used as refrigerant
Code: [Select]
(is probably the confusion...hmmmm), the propane is used to raise the pressure to compress the gas into the reservior on the high pressure side of the unit.

And the questioner should have written his question better(Only quite misses it, there is that contradictory point of knowing latent heat "Me,I'd say its finally about counterbalancing pressures in the system").

Quote
I know how an air conditioner operates but what is propane used to do in a propane powered fridge?

Me, i think not but now i am confused. to do that someone has to light the propane!
The quote above, later becomes contradictory!!! when you get to the second quote i have below.

As a flammable gas in the 2. region of "dangerous goods transportation and handling" laws, I hardly think it would (be cheap unless the guy is rolling in green filth in his bank accout) be allowed to light itself

So there is no possible way the bloke would ask the question in the context of it being about what he does not want to burn himself down with and ...propane powered... is what he has stated.

Either he needed to know about drive mechanism by heating(unlikley but possible) , or he needed to know about
Quote
... I remember learning about heat transference in school but I cannot remember how this works exactly....
  state change and latent heat (taught in most 1st and 2nd world countrys schools around the world)
but that still leaves the high and low pressure side and the difference betwixt drive by heating for compression drive and electricity for compressor drive but remains about latent heat anyhow.

In spending money, i'm sure he knows there is no electricity and why he uses propane.
....... excuse me  ... My son never calls  .... where did i leave my pants ... What did thread say about my pants?  .....   do they require latant heat?  .....  hullo! hullo!  ...  this isn't a phone its a computer   ....

==============================

I suppose the answers is
  [xx(]  [:o)] (society of the friends vodka propelants and vodka refrigerants)

The propane is burned to heat a part of the low pressure side to raise pressure to force the used(boiled gas) through a one way valve into the reservior side and cool it for a small period before re-allowing it to be boiled into the low pressure side inside the fridge.
(3 sections: 2-low-pressure, and 1 high-pressure).
There are two basic sides of refrigeration units(3 in this system) a boiling side and a compression side.

Then the piece about latent heat.

The parts in bold above here and below the "=====" line here are probably the best can be gathered to the meaning of what was requested. but...

note: but to answer the question can be an awfully large contradiction (particularly of the forums' context: we do the best we can)
Quote
...asks a simple question on these forums, they normally need a non-confusing answer...
« Last Edit: 08/06/2009 06:22:57 by nicephotog »
 

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How does a propane-powered camping refrigerator work?
« Reply #8 on: 08/06/2009 06:57:51 »
Why do you think the fact that someone needs to light the burner is any sort of problem?
Also, while the original post might not be perfectly clear, it's a lot clearer than your reply.
 

lyner

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How does a propane-powered camping refrigerator work?
« Reply #9 on: 08/06/2009 11:06:47 »
nicephotog
The original question was quite clear to me and to everyone else.
Do you really think your posts have answered the original question?
If you knew anything about the topic of actual fridges, you would know that absorption systems work almost continuously because they are just not very good. You light it when you start using it and you turn off the gas when you start driving (for safety reasons).
There are no brownie points for 'too clever'.
 

Offline antonette93

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How does a propane-powered camping refrigerator work?
« Reply #10 on: 27/08/2010 09:00:15 »
Well based on what I have search through internet, I have found out that a propane-powered camping refrigerator works by using propane burner, instead of the electrically powered pump which is commonly used in standard electrical refrigerators. This refrigerator are environment friendly and hence should be preferred over the electrical refrigerator. I am just not sure if this is so true.

« Last Edit: 31/08/2010 09:53:38 by antonette93 »
 

Offline Geezer

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How does a propane-powered camping refrigerator work?
« Reply #11 on: 28/08/2010 05:05:00 »
Well based on what I have search through internet, I have found out that a propane-powered camping refrigerator work it uses propane burner, instead of the electrically powered pump which is commonly used in standard electrical refrigerators. This refrigerator are environment friendly and hence should be preferred over their electrical counterparts.

Er, so why's that then? You wouldn't happen to be spamming for a propane producer would you?
 

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How does a propane-powered camping refrigerator work?
« Reply #11 on: 28/08/2010 05:05:00 »

 

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