Pratique du Shadowing: Air Conditioning System Basics hvacr how does it work - Apprendre l'anglais à l'oral avec la vidéo
Création de la leçon...
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sponsored by danfoss when we look at a typical refrigeration system we have the compressor
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the condenser the expansion valve and the evaporator the condenser
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and the evaporator are both heat exchangers the condenser sits outside the property
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and the evaporator sits inside the room being cooled the compressor circulates a refrigerant in the pipe work
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which cycles between all of these components the expansion valve regulates
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the flow of refrigerant the refrigerant is a specially designed fluid
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which can change between being a liquid and a gas very easily and that's
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because it has a very low boiling point for example refrigerant
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are for 10 a will boil at negative 48 degrees Celsius
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or negative 55 degrees Fahrenheit although this will change with pressure
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but if the refrigerant is inside a pipe within a room
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and the room is at 30 degrees Celsius
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or 86 degrees Fahrenheit then this will be more than enough to cause it to boil from a liquid into a vapor.
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By the way if you want some refrigerant charts you can download these for free from our website.
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I'll link to these in the video description down below.
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So the The refrigerant is entering the evaporator as a low pressure, low temperature liquid vapor mixture.
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It flows on the inside of the pipe
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and at the same time a fan is moving the ambient air of the room over the outside of the pipe.
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This causes the refrigerant to boil.
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It will absorb the heat from the air through the pipe wall and then it evaporates.
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As the refrigerant evaporates, it carries away the heat.
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It's similar to when we boiled water.
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The water heats up, it evaporates and turns into steam and carries this heat away.
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So the air on the outside is entering hot and it's leaving cold.
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The refrigerant continues to travel through the evaporator, picking up more heat which boils it further until it becomes slightly superheated.
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This basically means it's now completely gas and doesn't contain any droplets of liquid refrigerant.
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Liquid damages the compressor, so we want to ensure it can't reach the compressor.
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The compressor sucks in the refrigerant, which is leaving the evaporator as a low -pressure, low -temperature, slightly superheated vapour.
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It then squeezes this together into a much smaller space, and so the pressure increases.
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All the heat which was picked up in the evaporator is now contained in a much smaller volume, so the temperature will increase.
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This is very important and we will see why in just a moment.
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But if you've ever pumped up a bicycle tyre, you will notice the pump becomes hotter as it's compressing the air.
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The refrigerant is then pushed into the condenser where it enters as a high -pressure, high -temperature, superheated vapour.
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the condenser is located outside
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and the outside air might be very warm on a summer's
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day as heat always flows from hot to cold we need to ensure
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that the refrigerant is hotter than the outside air otherwise the
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unwanted heat will not be able to leave the refrigerant and leave our system
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a fan will help to blow ambient air over the condenser to remove this heat
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so the outside air is entering warm picking up heat
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and leaving hot as the heat is removed by the air
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this causes the refrigerant to condense back into a liquid it's a little bit like
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when steam hits the window on a cold day the window is cold
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so it condenses the steam from a vapor into a liquid
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and then this liquid starts to run down the window the
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refrigerant therefore exits as a high pressure medium temperature saturated liquid
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and this heads to the expansion valve the expansion valve needs
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to regulate the amount of refrigerant entering the evaporator to control the superheat
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if it allows too much refrigerant to flow it can flood the evaporator
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so the refrigerant doesn't evaporate a liquid reaches the compressor
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and possibly destroys it but
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if it lets in too little refrigerant the system won't provide enough cooling and
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so it operates inefficiently the expansion valve regulates the refrigerant by
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only allowing it to pass through a small hole this creates
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a large pressure difference across the valve one side is the high -pressure liquid the other side is almost empty
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The small hole causes it to almost spray into the evaporator as a part liquid, part vapor mixture.
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The refrigerant will expand to try and fill the empty space on the other side
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and this will cause it to drop in pressure as well as temperature.
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It's a little bit like spraying a deodorant can or a spray paint can.
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It flows through a small hole causing it to expand as a part vapor
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and part liquid mixture
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and then we can feel the can become cooler now the
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original method to control this was by using a fixed orifice device
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and you might still find these on the back of your
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refrigerators the hole within this device was a fixed size
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so the entire system would simply turn on
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and off to meet the cooling demand it does work
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but we can't maintain a stable temperature control
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because the system is simply turning on
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and off the next evolution was the thermostatic expansion valve this is still widely used today
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and it senses the superheat at the outlet through a bulb
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which is filled with another refrigerant this other refrigerant will expand to close the valve
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when the superheat is too high and it condenses to open the valve when the superheat is too low.
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This type of valve needs to be manually calculated and adjusted by a technician.
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It does work very well but it's prone to mistakes.
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It also takes a long time to calculate and set up
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and it is also only adjusted once per service visit which is not ideal.
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It will also not allow peak performance.
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However it does work very well and these will continue to be used for many years.
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And And so the latest evolution is to use electronic expansion valves.
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These use a controller to measure the exact temperature and pressure
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and adjust the valve position automatically in real time to ensure optimal performance and maximum system efficiency.
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Okay that's it for this video but to continue learning about HVAC
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and refrigeration engineering click on one of the videos on screen now and I'll catch you there for the next lesson.
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Don't forget to follow us on Facebook, Twitter, LinkedIn, Instagram as well as theengineeringmindset .com
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Vocabulaire et conseils d’expression pour cette leçon
Cette leçon d’expression orale s’appuie sur la vidéo « Air Conditioning System Basics hvacr how does it work ». Les mots qui reviennent le plus souvent : refrigerant, liquid, valve, heat, evaporator. Cette vidéo contient 85 phrases et 1097 mots à répéter en shadowing. La partie parlée dure 7:15. Le locuteur parle à un rythme naturel d’environ 151 mots par minute, proche d’une conversation courante. Seuls 77 % des mots font partie des 3 000 mots les plus courants en anglais, le vocabulaire est donc exigeant.
Vocabulaire clé de cette vidéo
15 mots de la vidéo à retenir, avec leur prononciation et leur sens :
| Mot | Prononciation | Sens |
|---|---|---|
| liquid nom | /ˈlɪk.wɪd/ | liquide |
| valve nom | /ˈvælv/ | clapet, soupape |
| boil verbe | /bɔɪ(ə)l/ | faire bouillir, porter à ébullition |
| pipe nom | /ˈpaɪp/ | cornemuse |
| vapor nom | /ˈveɪpɚ/ | vapeur |
| expand verbe | /ɪkˈspænd/ | agrandir |
| mixture nom | /ˈmɪkst͡ʃɚ/ | mélange |
| spray nom | /spɹeɪ/ | embrun, gouttelette |
| adjust verbe | /əˈd͡ʒʌst/ | ajuster |
| regulate verbe | /ˈɹɛɡ.jə.leɪt/ | régler |
| evolution nom | /ˌiːvəˈluːʃ(ə)n/ | évolution |
| pump nom | /pʌmp/ | pompe |
| calculate verbe | /ˈkælkjʊleɪt/ | calculer |
| stable nom | /ˈsteɪ.bəl/ | étable, écurie |
| chart nom | /t͡ʃɑɹt/ | carte |
Les verbes à particule que vous entendrez
| Mot | Prononciation | Sens |
|---|---|---|
| pick up verbe | soulever | |
| heat up verbe | chauffer | |
| pass through verbe | traverser | |
| run down verbe | heurter | |
| set up verbe | /ˌsɛt ˈʌp/ | mettre en place, installer |
La grammaire de cette vidéo
Les structures que le locuteur utilise le plus, avec les mots exacts de la vidéo :
| Structure | Dans la vidéo |
|---|---|
| Voix passive be + participe passé — l’accent est mis sur ce qui arrive, pas sur qui le fait | being cooled · was picked · is located |
| Propositions relatives who / which + proposition — une précision sur une personne ou une chose | refrigerant, which is · heat which was · visit which is |
Prononciation à surveiller
Le locuteur utilise 9 contractions et formes réduites, comme can't, doesn't, I'll. Prononcez-les sous leur forme courte, telles que vous les entendez.
- Les sons « sh » et « zh »: evolution /ˌiːvəˈluːʃ(ə)n/, efficiency /ɪˈfɪʃ.ən.si/, specially /ˈspɛʃəli/, technician /tɛkˈnɪʃən/
- Mots longs — placez bien l’accent: evolution /ˌiːvəˈluːʃ(ə)n/, efficiency /ɪˈfɪʃ.ən.si/, manually /ˈmænj(u)əliː/, refrigerator /ɹɪˈfɹɪd͡ʒ.əˌɹeɪ.tɚ/, evaporator /ɪˈvæp.ə.ɹeɪt.ɚ/
Les sons difficiles pour les francophones :
- /tʃ/ et /dʒ/ — à ne pas adoucir en « ch » et « j »: mixture /ˈmɪkst͡ʃɚ/, adjust /əˈd͡ʒʌst/, chart /t͡ʃɑɹt/, refrigerator /ɹɪˈfɹɪd͡ʒ.əˌɹeɪ.tɚ/
- /r/ anglais — langue recourbée, sans frotter la gorge: spray /spɹeɪ/, regulate /ˈɹɛɡ.jə.leɪt/, chart /t͡ʃɑɹt/, controller /kənˈtɹoʊlɚ/, prone /pɹəʊn/
Comment s’entraîner avec cette vidéo
- Écoutez la vidéo en entier une fois sans parler et notez les mots que vous ne connaissez pas.
- Commencez à la vitesse 0,75×, répétez phrase par phrase, puis revenez à la vitesse normale quand cela devient facile.
- Enregistrez-vous et comparez avec l’original, en faisant attention à des mots comme liquid, valve, boil.
Qu'est-ce que la technique du Shadowing ?
Le Shadowing est une technique d'apprentissage des langues fondée sur la science, développée à l'origine pour la formation des interprètes professionnels. Le principe est simple mais puissant : vous écoutez de l'anglais natif et le répétez immédiatement à voix haute — comme une ombre suivant le locuteur avec un décalage de 1 à 2 secondes. Les recherches montrent une amélioration significative de la précision de la prononciation, de l'intonation, du rythme, des liaisons, de la compréhension orale et de la fluidité.