Condensateurs électrochimiques (électrolytiques aluminium). Le 1er est de 1 000 µF pour une tension de service de 35 V (modèle axial), le 2e est de 10 µF pour 160 V (modèle radial).
Un condensateur est un composant électronique ou électrique élémentaire, constitué de deux armatures conductrices (appelées « électrodes ») en influence totale et séparées par un isolant polarisable (ou « diélectrique »). Sa propriété principale est de pouvoir stocker des charges électriques opposées sur ses armatures. La valeur absolue de ces charges est proportionnelle à la valeur absolue de la tension qui lui est appliquée. Le condensateur est caractérisé par le coefficient de proportionnalité entre charge et tension appelé capacité électrique et exprimée en farads (F). La relation caractéristique d'un condensateur idéal est :
Fox's Tales by Graeme Fox
Graeme Fox is an RAC contractor based in Dundee. He is a director at AREA (Air Conditioning & Refrigeration European Contractors' Association) and a member of the Institute of Refrigeration.
06/10/2009 09:25:01
What an interesting month its been. A number of people posted comments after my last blog - many of which followed the usual line these days: if you can't argue the case, just smear the name!
Some interesting technical points were made, but there are two things I'd like to say on the issue of the exploding fridges before I move on.
Firstly, despite the comments left by those who claim the small charge cannot possibly result in this damage - the fact remains that a very small leak has resulted in ignition in the past. This fact has been accepted by the manufacturers, hence the imminent tightening of the EN378 regulation. Interesting that those who argue against the facts refuse to leave their names or organisation names on the site. If you are so sure of the facts why hide behind a pseudonym? It only makes me suspicious that those who are arguing don't know the facts, only the spin.
Secondly, for anyone who attended the recent Cooling Industry awards it was obvious to all present how the industry feels about hydrocarbon refrigerants becoming the norm. When reference was made by some to the exploding fridge story highlighted here, there was a considerable swell of approval for raising the issue and getting the real arguments discussed for a change.
While wholesale changeover to hydrocarbons would conveniently tick a box and meet one target for our political classes, they would be left with a severe energy shortage crisis due to the lower efficiencies with split system air conditioners running on hydrocarbons compared with HFCs.
All of this is, of course, entirely avoidable if industry is given the power by government to properly and effectively police the F Gas Regulation. The argument is simple.
HFCs account for around 1.5% of greenhouse gas emissions worldwide.
Of that, car ac account for around 70%. Therefore, static ACR accounts for around 0.5%.
A properly implemented F Gas Regulation would result in a drop in emissions to around 10% that of present levels (based on the results of similar legislation abroad). Therefore, once the car ac industry has dealt with their phase out which is already agreed, the static acr industry will account for approximately 0.05% of the world's greenhouse gas emissions.
The message is clear: we're not the ones who are damaging the planet.
Concentrate on energy efficiency and we'll see real results in the carbon emissions reduction programme.
Finally, a message to John Wallis who seemed to enjoy referring to my blog as a fairy tale. There is no definitive answer to your question. Different manufacturers and different models of domestic fridge would hold varying amounts of hydrocarbon refrigerants. However, it is safe to say between 25 and 150 grammes. I know some readers find it incredulous that such a small amount of gas can cause this damage, but clearly it is possible.
Some industry figures have come out pointing out the small number of incidents compared to the vast numbers of fridges sold. This is true. But one incident is too many isn't it? Particularly when there is the real possibility of fatality.
And all we've seen in answer to the recent spate of bad publicity has been technical speak, which helps to confuse the political classes, insinuating this sort of thing cannot happen.
The editor of ACR News posts his own cold thoughts about the ACR industry and anything else he cares to air.
19/02/2010 11:34:45
Many will be aware of the struggle going on between environmental groups and the fluorocarbon industry to win the "hearts and minds" of the car makers over the imminent need to replace R134a in car air conditioning systems.
The environmental groups have been pushing CO2 but the fluorocarbon industry now appears to have trumped them with a new "fourth generation" refrigerant, the hydrofluoro-olefin HFO1234yf.
It is a struggle which is likely to be fought out in the stationary equipment market in the future as HFOs are being seen as having potential to replace HFCs in this market as well.
On the face of it, HFO1234yf ticks all the boxes of acceptability from an environmental standpoint. The car manufacturers love it because it will not increase their costs which, in today's cost-obsessed society is a major consideration. The fluorochemical producers love it because the last thing they want is a cheap, patent-free natural substitute for 134a. The development of HFOs will potentially provide good profits for them in the long term but that is what being in business is all about. They would also argue that it is what the industry wants.
HFO1234yf does, however, have one major drawback: it is flammable, althoughly only "mildly" as the chemical companies are quick to point out.
CO2 also ticks all the environmental boxes with the added benefit that it is non-flammable. As a high pressure refrigerant, though, CO2 will require more expensive equipment, increasing production costs, and the ac system will be heavier meaning greater car fuel usage and as a result making CO2 a less energy-efficient alternative.
The environmental groups appear to be against HFO1234yf purely on the grounds of its flammability. Their tests appear to show that there is a potential problem here. The chemical industry points to the fact that HFO1234yf has passed all the tests including ASTM and claims that tests by environmental groups are "not representative of real-world conditions".
I would applaud their persistence with this safety aspect of HFO1234yf. It is something that clearly needs airing before these refrigerants become universally accepted.
Now call me a confused, cynical, old journalist if you like but I am still confused by the enviromentalists' stance on HFO1234yf. Perhaps they could answer me the following questions?:
1. Environmentally, HFO1234yf ticks all the boxes, right? Concerns about safety are admirable but that is not an environmental issue. Therefore, why is it not being welcomed with open arms by environmental groups?
2. Why is so much being made of the safety of a refrigerant which is less flammable than any of the hydrocarbons so enthusiastically promoted by environmentalists and the natural refrigerant lobbyists?
3. When this magazine carried news of a propensity for hydrocarbon domestic refrigerators to "explode", many supposed "experts" claimed that this couldn't happen, others, irresponsibly, suggested that these news stories should be ignored. Are these same environmental groups now working with the domestic refrigerator manufacturers to overcome this safety issue?
4. Some rightly maintained that the cases of hydrocarbon domestic refrigerators exploding were very rare, particularly compared to the number which catch fire every year. The inference here being that as it was so rare it wasn't a problem. By the same token, if the chances of HFO1234yf catching fire in a car air conditioning system are equally as rare, should we be concerned?
5. The environmental groups are currently very busy promoting hydrocarbons as a suitable alternative to HFCs in all manner of refrigeration and air conditioning systems. Will these same environmental groups be carrying out similar tests to ensure that there are no safety risks with these far more flammable refrigerants in stationary applications?
Cotopaxi the highest active volcanoes in the world at 19,348ft (5897m) are located at the center of the most visited national park on the Ecuadorian mainland. Located 1 ½ to 2 hours south of Quito on the eastern flank of the Andes, Cotopaxi offers visitors the opportunity to enjoy a variety of activities including mountaineering, hiking, birding, horseback riding, camping and mountain biking.
HISTORY
For centuries the native people of the area worshiped Cotopaxi as a god. Foundations of homes built near the Rio Pita are evidence of the pre-Hispanic cattle herders in the area. The ruins show evidence of platforms built to worship the mighty mountain. These people also realized the strength and strategic position the mountain offered them by building fortresses high its flanks. El Saitre was built to control the passage into the area. As the Incas arrived in the area they too worshiped the mountainand built fortresses to control the surrounding area.
Much of the mountain's history surrounds its volcanic activity. Records indicate that in 1534 the conquistadors engaged in a war with the locals for control of what is now Ecuador. During a battle on the flanks of Cotopaxi the mountain began to erupt. The locals viewed this as a sign from their god and ran off in fear. The Spanish unused to volcanic activity and seeing the reaction of the locals ran off in terror.
Since the Spanish first experience with the fury of Cotopaxi there have been many eruptions. The most famous occurred in June of 1877. Smoke from the volcano could be seen from Quito to Latacunga. Ash filled the skies and covered the countryside all the way to Machachi. As the lava poured out of the crater it melted the glacial ice and created lahars (avalanches of mud) that sped down the mountain reeking havoc along the way. Much of the neighboring countryside was buried as a wave of mud cascaded over it. The city of Latacunga was demolished it's residents unable to escape were buried alive. The lahars continued with such a magnitude that within an 18-hour period the mudflows had reached the Pacific Coast town of Esmeraldes. Much of the countryside of the Sierras still show signs of that devastating flow.
CLIMATE
Temperatures on Cotopaxi vary little throughout the year. The average daytime temperature is 45°F (7°C). Seasonal variations and night-time temperatures range the temperatures between freezing and 68°F (20°C). Visitors to the Park are recommended to bring several layers of clothes including a warm sweater and protective rain-wind jacket, hat and gloves.
The rainy seasons run between January and May and October and November. The main dry season of June to September though the strong winds are known to occur. December also has a short dry season and the time around Christmas is normally considered the best weather of the year.
In general the best weather (least chance of rain or cloudy skies) is around the full moon. Climbers are recommended to plan assents around the full moon whenever possible.
The vegetation changes with the altitude and when we reach 11,500ft (3500m) we find arboreal species like Pumamaqui (Oreopanax s.p.p.), Quishar or "God's tree", Mortiño (Vaccinium floribundum) and Romerillo (Hypericum laricifolium).
In the Lake Limpio Pungo area there are many birds, especially the Galleteras, ducks, Andean Gull and Sparrow hawks. The rocky volcano Rumiñahui is one of the areas known for condors.
