US Postal Service halts air conditioner shipments to soldiers

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Author	Topic: US Postal Service halts air conditioner shipments to soldiers
Eboy Member	posted 08-23-2003 12:36 PM " . . . the Postal Service says the machines contain compressed gas, which is banned on international air shipments." Big wow. Remove the ban, or grant a waiver. Freon. Oooooooh. I'm scaaared. When I was a kid my friends and I would beat the bejesus out of air conditioners at the junkyard to see the freon come out. Seems rather benign. Don't see it downing a plane. http://abclocal.go.com/wpvi/news/82103-postalac.html IP: Logged
Frank2941 Member	posted 08-23-2003 04:26 PM I am not sureif it does, or should, make a difference, but air conditioners are no longer made using freon. IP: Logged
green riley Member	posted 08-23-2003 05:36 PM One other thing: When the air conditioner is not operating, there is no compressed gas.. only a liquid in the accumulator. Why wouldn't the USPS know that? IP: Logged
col22 Member	posted 08-23-2003 09:15 PM quote: Originally posted by green riley: One other thing: When the air conditioner is not operating, there is no compressed gas.. only a liquid in the accumulator. Why wouldn't the USPS know that? Maybe because it isn't true. If you compress a gas it becomes a liquid(apart from high temperature situations not discussed here). The liquid in the accumulator is only just at enough pressure(relative to apmospheric) to remain a liquid, and the rest of the system is filled with high pressure gas! When the unit is started then there is a pressure differential created. (one side is at greater pressure than the other, but both are greater than apmospheric) Freon (and it's brothers and sister refigerants) are gas at room temperature(and atmospheric pressure) which means if there were no pressure they would be a gas and not a liquid. PS. I don't use the naive icon normally! ed(and atmos)and rest of system... [This message has been edited by col22 (edited 08-23-2003).] [This message has been edited by col22 (edited 08-23-2003).] IP: Logged
annef Moderator	posted 08-24-2003 10:33 AM Thank you, col22. I will now go light the charcoal grill with my disposable butane lighter. Anne IP: Logged
green riley Member	posted 08-24-2003 04:56 PM quote: Maybe because it isn't true. If you compress a gas it becomes a liquid(apart from high temperature situations not discussed here). What? The principal that air conditioners operate on is that when a gas is expanding, it is cooling (absorbing heat). quote: The liquid in the accumulator is only just at enough pressure(relative to apmospheric) to remain a liquid, and the rest of the system is filled with high pressure gas! Get out! The liquid in the accumulator is just like the liquid in your barbeque propane cylinder. It is a function of temperature, not pressure. When the compressor compresses the liquid and allows it to escape through an expansion valve, it becomes a gas which in turn, goes to the condensor where it absorbs heat, changes back to a liquid (oil line) and returns to the compressor to repeat the cycle. When the unit is started then there is a pressure differential created. (one side is at greater pressure than the other, but both are greater than apmospheric) The compressor unit is hermatically sealed from atmospheric pressure. However, the compressor does create pressure (up to 250 psi). The return side is a vacuum, not a pressure. When the compressor shuts off, the pressure is relieved, not unlike an air compressor. This prevents the unit from starting up against pressure. Freon (and it's brothers and sister refigerants) are gas at room temperature(and atmospheric pressure) which means if there were no pressure they would be a gas and not a liquid. I don�t agree. What is LP gas? Liquid Propane. There is a state change from liquid to a gas when pressure is created. If the refrigerant gas were exposed to the atmosphere, it would boil off because all refrigerant gasses, and even propane, boil at a very low temperature. Shipping small air conditioners would not violate the policy of not shipping pressurized gases. In fact, the airlines themselves regulary transport pressurized oxygen bottles in the passenger �overhead compartments. IP: Logged
col22 Member	posted 08-24-2003 09:26 PM Anne, why you rolling eyes at me? You press the button on your disposable and the high pressure gas part of your lighter ejects the gas for you to ignite and the liquid boils in the lowered pressure. Where's the problem? (and after I seconded you as the mom!) green, quote: The principal that air conditioners operate on is that when a gas is expanding, it is cooling (absorbing heat). nearly right, the principal is when a specific liquid is acted on by a lower pressure then the liquid turns to a gas and removes heat to do so. quote: The liquid in the accumulator is just like the liquid in your barbeque propane cylinder. It is a function of temperature, not pressure. If you heat your propane cylinder or cool it the liquid will not change it is liquid because of the pressure(that will change) and if you change the pressure ie. open the valve to atmospheric then it will all boil off no imposed temperature difference required. quote: The compressor unit is hermatically sealed from atmospheric pressure. However, the compressor does create pressure (up to 250 psi). The return side is a vacuum, not a pressure. It is only a vacuum relative to the compressed side. quote: I don�t agree. What is LP gas? Liquid Propane. There is a state change from liquid to a gas when pressure is created. If the refrigerant gas were exposed to the atmosphere, it would boil off because all refrigerant gasses, and even propane, boil at a very low temperature. Hey, you're all over the place here, 'liquid to gas when a pressure is created'? surely you mean when a pressure is reduced? and I thought you said it was a function of temperature not pressure! Although as you say refrigerant gasses boil at a low temperature, pressure varies boiling temperature also, so if there was no pressure the refrigerant would be boiling permanently in the air conditioner and the LP cylinder and would be a gas and not a liquid!(which it isn't) quote: Shipping small air conditioners would not violate the policy of not shipping pressurized gases. eboy's first post quoted " . . . the Postal Service says the machines contain compressed gas, which is banned on international air shipments." Well they are wrong or you are! I wonder who it is? [This message has been edited by col22 (edited 08-24-2003).] IP: Logged
annef Moderator	posted 08-24-2003 11:47 PM Whoops. Sorry, col. I obviously sent a mixed message with my inadequate attempt at sarcasm. Should know better before I have my third cup of coffee. I'll have you know that I successfully released the pressure in my lighter in order to light my charcoal fire with a flammable gas. Actually, I just lit the newspaper in the charcoal bucket -- but the principle remains the same. I feel as if we should all hold hands and chant a ditty about thermodynamics (emphasis on 2nd law, please) with a chorus singing the praises of COMPRESSION refrigeration v steam-jet. Do you think this discussion would make more sense if we looked at refrigerators rather than ACs? As resident mother, I recommend drying the inside of your tennies by placing by them facing the heat exhaust grill of your 'rator, assuming it's on the floor. Your humble correspondent, who will now go pour a glass of wine (it's too late for coffee to do any good) and hunker down with a very creepy police novel while being grateful that she doesn't have to recharge her refrigerator if the power goes out. Anne IP: Logged
llamas Member	posted 08-25-2003 06:34 AM col22's description is 100% correct. green riley's description is so throughly confused that it is essentially 100% incorrect. A portable electric air conditioner, unplugged, at rest and turned off, may contain refrigerant in both the liquid and gaseous state. If left for long enough, pressure will equalize in the system, but it will always be at some pressure considerably higher than atmospheric - typically 50-100 psig. If the regrigerant system is breached, a mixture of liquid and gaseous refrigerant will be expelled, and the part of the refrigerant that is liquid will boil off to gas. This description: 'Get out! The liquid in the accumulator is just like the liquid in your barbeque propane cylinder. It is a function of temperature, not pressure. When the compressor compresses the liquid and allows it to escape through an expansion valve, it becomes a gas which in turn, goes to the condensor where it absorbs heat, changes back to a liquid (oil line) and returns to the compressor to repeat the cycle.' is total garbage, from start to finish. Here's a straightforward description of the refrigerant cycle: http://www.warmair.com/html/refrigeration_cycle.htm Note that while there are high- and low-pressure areas in the system, these are relative terms and there is no part of the system which is below, or even near to, atmospheric pressure. green riley, when you don't know what you're talking about, it's best to just keep quiet. The USPS may have a point. All common refrigerants are more-or-less flammable. Air conditioners could be a safety issue in air freight. However, it does seem an awfully stringent interpretation of safety rules, especially if they are in their original packing and palletized for air freight. llater, llamas ------------------ . . . a truly bad and evil man. "All things are ready, if our minds be so." King Henry V, Act 4, scene 3 "Let us labour, then, to think well, for such is the foundation of morality" Pascal, "Pensees", sec. VI IP: Logged
setnahkt Member	posted 08-25-2003 11:46 AM quote: Originally posted by Eboy: " . . . the Postal Service says the machines contain compressed gas, which is banned on international air shipments." Although no Federal regulations are easy to understand the hazmat transport rules are especially egregious, reading as if someone had taken a reasonable and comprehensive set of safety rules and then randomly rearranged all the sentences. However, if the USPS would look hard enough, they would find find a table entry (at 49CFR172.101) that specifically mentions "Refrigerating machines, containing non-flammable, nontoxic, liquefied gas or ammonia solution (UN2672)" and allows transport of up to 450 kg of such machines on either passenger or cargo aircraft, as long as they are properly labeled, etc. AFAIK there's no specific prohibition of "compressed gas on international flights" as the USPS spokesperson claims. It could be that the USPS has its own rules that are more restrictive than DOT rules. Someone mentioned aircraft oxygen bottles and oxygen generators as examples of aircraft transport of compressed gas. The rules always distinguish between hazmat being transported as cargo, which is regulated, and hazmat involved in operation of the transport vehicle, which isn't. IP: Logged
Nightman Member	posted 08-25-2003 01:38 PM quote: All common refrigerants are more-or-less flammable I don't think so. Certainly propane and butane which are now frequently used in small scale so called 'green' units are, but the HCFC and HFA replacements for CFCs are, AFAIK non flammable. ------------------ Nightman Who doesn't usually believe everything that he sees in the media. IP: Logged
llamas Member	posted 08-25-2003 02:25 PM quote: Originally posted by Nightman: I don't think so. Certainly propane and butane which are now frequently used in small scale so called 'green' units are, but the HCFC and HFA replacements for CFCs are, AFAIK non flammable. Depends what you call 'flammable' Here's the flammability rating system and results for the most common refrigerants: http://www.iifiir.org/2endossiers_fiches_classification.htm I have before me a service warning regarding the use of R134a, which is now the de-facto standard in auto air-conditioning. It warns agaisnt the use of compressed air to purge systems using R134a, because potentially-flammable vapour mixtures may be formed. R152a, the 'next-generation' refrigerant which is supposedly ozone-safe AND greenhouse-safe, suffers from the nigglin' drawback that it is quite flammable indeed. There have been vapourings in the trade press about 'refrigerator bombs' and suchlike. Most of this is hyperbole, no doubt, but there's truth to it. llater, llamas ------------------ . . . a truly bad and evil man. "All things are ready, if our minds be so." King Henry V, Act 4, scene 3 "Let us labour, then, to think well, for such is the foundation of morality" Pascal, "Pensees", sec. VI IP: Logged
setnahkt Member	posted 08-25-2003 07:28 PM quote: Originally posted by llamas: Depends what you call 'flammable' Exactly so. The DOT (see 49CFR173) uses a different definition of "flammable" and "toxic" than the linked article. Rumor has it the the definitions were juggled to ensure that anhydrous ammonia remained a nonflammable, nontoxic gas to facilitate shipments for farming. This has contributed to a least one fatal accident; firefighters responding to a ammonia leak in a refrigerated warehouse assumed that the "nonflammable" label for ammonia meant it wouldn't burn under any circumstances. Their SCBAs were protecting them against toxicity, so they used a forklift to get up to leak. Bang. IP: Logged
ECHOALPHA Member	posted 08-26-2003 01:30 AM The USPS may have a point. Most of the rules re hazmat shipping were highly modified for political/economic reasons and one can only shake your head and mumble under your breath about the stupidity of the final result. Yes I transport some of the hazmat materials in the course of making money. [This message has been edited by ECHOALPHA (edited 08-26-2003).] IP: Logged
Nightman Member	posted 08-26-2003 04:16 AM I don't like to quibble, but I will because loose statements get taken up by others and are a cause of a lot of junk science support. The initial statement was: quote: All common refrigerants are more-or-less flammable which implies that all have potential flammability risks. The qualifying statement was: quote: Depends what you call 'flammable' This is true but still misleading, a look at the link provided shows that out of 21 refrigerants only 3 are Class 3 with a further 6 rated as Class 2. 9 out of 21 does not constitute 'most' ------------------ Nightman Who doesn't usually believe everything that he sees in the media. IP: Logged
llamas Member	posted 08-26-2003 06:39 AM quote: Originally posted by Nightman: I don't like to quibble, but I will because loose statements get taken up by others and are a cause of a lot of junk science support. The initial statement was: [QUOTE]All common refrigerants are more-or-less flammable which implies that all have potential flammability risks. The qualifying statement was: quote: Depends what you call 'flammable' This is true but still misleading, a look at the link provided shows that out of 21 refrigerants only 3 are Class 3 with a further 6 rated as Class 2. 9 out of 21 does not constitute 'most' [/QUOTE] Nightman - no, that's fine. Quibble away. As setnahkt has already linked, 'flammable' means different things to different people, and you cannot make the assumption that because a refrigerant is rated '1', and the '1' rating is called 'non-flammable', that it will not burn in the right circumstances. As I noted, I have a flammability warning notice before me right now concerning R134a, which has a flammability rating of '1'. Here's what the Mobile Air Conditioing Society says about that: 'HFC-134a is considered as safe or safer than CFC-12 in motor vehicle uses, including involvement in collisions. Like CFC-12, HFC-134a is not flammable at ambient temperature and atmospheric pressures. However, HFC-134a service equipment and vehicle A/C systems should not be pressure tested or leak tested with compressed air. Some mixtures of air and HFC-134a have been shown to be combustible at elevated pressures. These mixtures may be potentially dangerous, causing injury or property damage.' However, your point is well-taken, and I will modify what I said, to wit: Many common refrigerants are flammable to a greater or lesser degree, depending on circumstances, while some are essentially non-flammable (and then, to encompass something you said earlier) some materials are now being used for refrigerants (eg butane and propane) which are far more flammable than the materials which have been commonly used in the past. How's that? llater, llamas ------------------ . . . a truly bad and evil man. "All things are ready, if our minds be so." King Henry V, Act 4, scene 3 "Let us labour, then, to think well, for such is the foundation of morality" Pascal, "Pensees", sec. VI [This message has been edited by llamas (edited 08-26-2003).] IP: Logged
Nightman Member	posted 08-26-2003 07:57 AM Thats fine. By the way the most alarming thing to happen to the refrigerant industry in the last few years is the move towards the more flammable gases for small scale installations and to the much more toxic ammonia for large scale installations. ------------------ Nightman Who doesn't usually believe everything that he sees in the media. IP: Logged
llamas Member	posted 08-26-2003 09:00 AM quote: Originally posted by Nightman: Thats fine. By the way the most alarming thing to happen to the refrigerant industry in the last few years is the move towards the more flammable gases for small scale installations and to the much more toxic ammonia for large scale installations. Move towards? Isn't that 'move backwards'? I once toured the refrigeration facility at Billingsgate fish market in London - this was 25 years ago. The heart of the system was a monstrous refrigeration unit from the 30's which used ammonia as the working fluid. Some of the piping had ice on it several feet thick, and they remarked at the time that all they did to it was to keep adding ammonia - they were frightened to death to defrost it and update it since the ice was all that was stopping the leaks. No doubt it has since been modernized, but I'll bet that it was a horrible job to shut it down and clean it out. llater, llamas ------------------ . . . a truly bad and evil man. "All things are ready, if our minds be so." King Henry V, Act 4, scene 3 "Let us labour, then, to think well, for such is the foundation of morality" Pascal, "Pensees", sec. VI IP: Logged
gorgas Member	posted 08-29-2003 09:57 PM quote: Originally posted by llamas: Move towards? Isn't that 'move backwards'? I once toured the refrigeration facility at Billingsgate fish market in London - this was 25 years ago. The heart of the system was a monstrous refrigeration unit from the 30's which used ammonia as the working fluid. Some of the piping had ice on it several feet thick, and they remarked at the time that all they did to it was to keep adding ammonia - they were frightened to death to defrost it and update it since the ice was all that was stopping the leaks. No doubt it has since been modernized, but I'll bet that it was a horrible job to shut it down and clean it out. llater, llamas Indeed, I believe some of the first efficient, practical refrigeration units were aboard naval vessels in the 1890's, and utilized ammonia. IP: Logged
John LeBlanc Member	posted 08-30-2003 08:30 PM Just wondering- how does electro-cooling (such as with those coolers that plug into a car) compare to compression-type refrigeration in terms of efficiency? ------------------ Earth first! We can mine the other planets later. IP: Logged
ECHOALPHA Member	posted 08-30-2003 10:17 PM quote: Originally posted by John LeBlanc: Just wondering- how does electro-cooling (such as with those coolers that plug into a car) compare to compression-type refrigeration in terms of efficiency? The direct electro cooling units currently available will only give you approx 40degrees below ambient temperatures which is inadequate for many things and they use a lot more energy to do so. The amperage draw of the direct cool sys will deplete my battery in approx 20 hours while the unit that uses a compressor is still happy with the same battery after 48 hours. Engine off in both cases. soda cooler in compressor driven model cubic inch capacity very close. IP: Logged
dave fitz Member	posted 08-31-2003 01:01 AM My own researches have indicated Peltier effect coolers to have a thermal efficiency of .8 to 1- that is, for each one BTU you kick out of the icebox, you spend .8 to 1 BTU worth of power. Not remotely efficient. A compressor-type unit regularly has efficiencies in the .2-.3 range. Absorption fridges, like the RV units that run off propane, can be as bad as 2.5-3 for rock-bottom low-grade heat sources. Their only selling point is quiet and grid-free operation. Only gas being cheaper than electricity per BTU makes them make any sense. dave IP: Logged
billholt Member	posted 08-31-2003 03:14 AM If anyone's interested, Shreve Systems has peltier coolers on sale for 5 for $10. I bought some and haven't quite figured out what I'm going to do with them yet. Considering adding a cooling element to my favorite beer coozy ... and maybe one in a hat, which makes the propeller more than a classical decoration. IP: Logged
col22 Member	posted 08-31-2003 02:09 PM Peltier rubbish 3 to 4% if you keep them happy, compressors upwards of cop10(coefficient of performance)that's 9 times more heat moved than you put in (in circum cirtainstances). But at those prices bill, I'll have a dozen! It feels like I have been holding out messing with them. Forever waiting for the cold chip to arrive but it just keeps on not doing. IP: Logged
ECHOALPHA Member	posted 08-31-2003 09:29 PM quote: Originally posted by col22: [B]Anne, why you rolling eyes at me? You press the button on your disposable and the high pressure gas part of your lighter ejects the gas for you to ignite and the liquid boils in the lowered pressure. Where's the problem? (and after I seconded you as the mom!) green, [QUOTE]The principal that air conditioners operate on is that when a gas is expanding, it is cooling (absorbing heat). nearly right, the principal is when a specific liquid is acted on by a lower pressure then the liquid turns to a gas and removes heat to do so. sorry but you better review your gas laws because allowing a gas to expand does reduce it's temperature so it is able to absorb heat energy. This is different from the energy absorbed by the change from a liquid to a gas which is called a phase change. The older ammonia based cooling units used the phase change for it's cooling but all of the compressor type units use the gas expansion through a small orofice to cool. IP: Logged
ECHOALPHA Member	posted 08-31-2003 09:34 PM quote: Originally posted by billholt: If anyone's interested, Shreve Systems has peltier coolers on sale for 5 for $10. I bought some and haven't quite figured out what I'm going to do with them yet. Considering adding a cooling element to my favorite beer coozy ... and maybe one in a hat, which makes the propeller more than a classical decoration. Have you thought about their use to cool especially portable computers?? Just a thought. IP: Logged
billholt Member	posted 09-01-2003 01:31 AM Echo, You're not exactly on track with the heat exchange issue. Yes, you are correct in saying that an expanding gas absorbs heat. However, Col22 was correct in saying that that is not the major factor in air conditioning. The major factor is the change of phase from liquid to gas which requires a lot of heat and is accomplished by the reduction of pressure. The peltier chips are designed for cooling CPUs but they're too bulky for portables of any configuration I'm familiar with. Those things are tight on the inside. Col22, I have no idea what efficiency to associate with these peltiers. In the original advertising on the site - no longer there - they said that some low double digit cooling was accomplished, 10� or 20� I think. I haven't had time to play with them yet. The site is www.shrevesystems.com. added by edit: found the old verbiage. It says quote: Peltier Junction with Heat Sink For all you tech-heads here's the original Peltier Junction and heat sink for the PowerPC 601+ processor. A Peltier Junction is also known as a thermo-electric cooler. Through the miracle of work-a-day physics it uses electric current to make itself at least 20� to 40� cooler than the ambient air temperature; often cold enough to freeze water. Cool your processor or be the life of Physics 101. Great for Peltier experiments! [This message has been edited by billholt (edited 09-01-2003).] IP: Logged
ECHOALPHA Member	posted 09-02-2003 12:04 AM quote: Originally posted by billholt: Echo, You're not exactly on track with the heat exchange issue. Yes, you are correct in saying that an expanding gas absorbs heat. However, Col22 was correct in saying that that is not the major factor in air conditioning. The major factor is the change of phase from liquid to gas which requires a lot of heat and is accomplished by the reduction of pressure. The peltier chips are designed for cooling CPUs but they're too bulky for portables of any configuration I'm familiar with. Those things are tight on the inside. Col22, I have no idea what efficiency to associate with these peltiers. In the original advertising on the site - no longer there - they said that some low double digit cooling was accomplished, 10� or 20� I think. I haven't had time to play with them yet. The site is www.shrevesystems.com. added by edit: found the old verbiage. It says [This message has been edited by billholt (edited 09-01-2003).] Hey I explained before wake up the phase change is the primary cooling function in the old ammonia based systems. But it isn't significent at the poerating pressures and temperatures in any of the compressor using systems because during normal operation there is no liquification of the freon by the heat exchanger unless you are also talking about a few heat sink type commercial large plant or large building air conditioning units. Just because the exchanger is called a comdenser doesn't mean it actually completes the job in a typical refrigerator or automotive a/c unit. IP: Logged
billholt Member	posted 09-02-2003 02:29 AM I hate it when things don't do what their name says they do. IP: Logged
llamas Member	posted 09-02-2003 06:18 AM quote: Originally posted by ECHOALPHA: [QUOTE]Originally posted by billholt: [b]If anyone's interested, Shreve Systems has peltier coolers on sale for 5 for $10. I bought some and haven't quite figured out what I'm going to do with them yet. Considering adding a cooling element to my favorite beer coozy ... and maybe one in a hat, which makes the propeller more than a classical decoration. Have you thought about their use to cool especially portable computers?? Just a thought. [/B][/QUOTE] Already commercialized, works quite well but expensive. The next family of Intel processors now in development may require a dedicated refrigeration system with working fluid, compressor, condensor etc. Peltier-effect devices can't make the differentials required, as noted previously. llater, llamas ------------------ . . . a truly bad and evil man. "All things are ready, if our minds be so." King Henry V, Act 4, scene 3 "Let us labour, then, to think well, for such is the foundation of morality" Pascal, "Pensees", sec. VI IP: Logged
Village Idiot Member	posted 09-02-2003 01:44 PM quote: Originally posted by billholt: I hate it when things don't do what their name says they do. Garbage disposal clogged again, Bill? IP: Logged
SPQR Moderator	posted 09-02-2003 03:14 PM I have a CCD camera for astrophotography that I built using the plans written by Richard Berry that uses a Texas Instruments CCD array cooled by a Peltier chip I swiped from one of those twelve-volt portable coolers. IP: Logged
col22 Member	posted 09-03-2003 10:07 AM Still wrong echo! Here have a read and see if you can spot where! IP: Logged
billholt Member	posted 09-03-2003 11:42 AM Sorry VI, apparently I aimed a bit high. A major component of ac/refrig units is something called a "condenser." That's the part of the unit where the gas is put under pressure until it converts to a liquid, or condenses, giving up substantial heat in the process. The heat transfer due to phase change - gas to liquid - is much, much greater than the heat transfer due to a similar pressure being applied to a gas without the phase change. Garbage disposal? That's what a back yard is for. The squirrels and rabbits love my little contributions to their diet. IP: Logged
ECHOALPHA Member	posted 09-06-2003 02:06 AM quote: Originally posted by col22: Still wrong echo! Here have a read and see if you can spot where! If I can find a phase diagram showing of course the relationship between pressure and temperature in relation to the liquid vs gas phases then I can check whether the pressure that is used in modern a/c for cars and room a/c units actually do condense to a liquid or as I was told many years ago that the theoretical change to the liquid phase doesn't actually occur at the available pressures of the "high side" and your are left with compressing the gas dumping energy in the condenser, and then the gas pressure is radically reduced by the orofice or "expansion valve" if you prefer so the low pressure side is able to absorb energy. By the way I am in agreement with you on the rest of Green Riley's statement being balderdash but even though I may be wrong I think he got that one thing correct. IP: Logged
col22 Member	posted 09-06-2003 10:36 AM ECHO, Here's a car a/c specific pdf. The second page has this on it. For example, when the gaseous refrigerant is compressed from 2.1 kg/cm2 to 15 kg/cm2, the temperature also increases from 0degC to 80degC.The boiling point of refrigerant at 15 kg/cm2 is 57degC . The temperature (80degC,) of compressed gaseous refrigerant is higher than its boiling point (57degC) and also higher than the surrounding air. The refrigerant stays in gaseous state. The compressed gaseous refrigerant releases heat to the surrounding air and is condensed back into a liquid. At this time, the refrigerant temperature becomes lower than the boiling point (around 57degC). The liquid refrigerant then returns to the receiver. Are these the figures you were after? IP: Logged
ECHOALPHA Member	posted 09-07-2003 01:15 AM quote: Originally posted by col22: ECHO, Here's a car a/c specific pdf. The second page has this on it. For example, when the gaseous refrigerant is compressed from 2.1 kg/cm2 to 15 kg/cm2, the temperature also increases from 0degC to 80degC.The boiling point of refrigerant at 15 kg/cm2 is 57degC . The temperature (80degC,) of compressed gaseous refrigerant is higher than its boiling point (57degC) and also higher than the surrounding air. The refrigerant stays in gaseous state. The compressed gaseous refrigerant releases heat to the surrounding air and is condensed back into a liquid. At this time, the refrigerant temperature becomes lower than the boiling point (around 57degC). The liquid refrigerant then returns to the receiver.Thank you this is the data I was looking for noting how close the B.P. is to the ambient temperatures (actually the temp of anything sitting just in front of an automobile radiator) I can see where condensation to the liquid phase is probable but not always going to occur especially if the compressor is worn so I will concede that the phase change should always occur in the room a/c units that were the original topic but may not occur in a car a/c system if the system is not working at near 100%. This also explains the tendency to overfill automotive systems to make them cool better, even though the result is a short compressor life or if you are lucky just eating the drive belts. Are these the figures you were after? IP: Logged

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