Pratica di Shadowing: Air Conditioning System Basics hvacr how does it work - Impara a parlare inglese con i video
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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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Vocabolario e note di pronuncia per questa lezione
Questa lezione di conversazione si basa sul video “Air Conditioning System Basics hvacr how does it work”. Le parole che ritornano più spesso: refrigerant, liquid, valve, heat, evaporator. Questo video contiene 85 frasi e 1097 parole da ripetere con lo shadowing. Il parlato dura 7:15. Chi parla ha un ritmo naturale di circa 151 parole al minuto, vicino a una conversazione quotidiana. Solo il 77% delle parole rientra nelle 3.000 più comuni dell’inglese, quindi il lessico è impegnativo.
Vocaboli chiave di questo video
15 parole del video che vale la pena imparare, con pronuncia e significato:
| Parola | Pronuncia | Significato |
|---|---|---|
| liquid sostantivo | /ˈlɪk.wɪd/ | liquido |
| valve sostantivo | /ˈvælv/ | valvola |
| boil verbo | /bɔɪ(ə)l/ | far bollire |
| pipe sostantivo | /ˈpaɪp/ | cornamusa |
| vapor sostantivo | /ˈveɪpɚ/ | gas, vapore |
| expand verbo | /ɪkˈspænd/ | estendere, espandere |
| mixture sostantivo | /ˈmɪkst͡ʃɚ/ | mistura, amalgama |
| adjust verbo | /əˈd͡ʒʌst/ | adattare, adeguare |
| regulate verbo | /ˈɹɛɡ.jə.leɪt/ | regolare, registrare |
| evolution sostantivo | /ˌiːvəˈluːʃ(ə)n/ | evoluzione |
| pump sostantivo | /pʌmp/ | pompa |
| calculate verbo | /ˈkælkjʊleɪt/ | calcolare |
| ambient aggettivo | /ˈæm.bi.ənt/ | ambientale |
| stable sostantivo | /ˈsteɪ.bəl/ | stalla, scuderia |
| chart sostantivo | /t͡ʃɑɹt/ | carta, carta nautica |
I phrasal verb che sentirai
| Parola | Pronuncia | Significato |
|---|---|---|
| pick up verbo | tirare su, sollevare | |
| heat up verbo | scaldare | |
| pass through verbo | trapassare | |
| run down verbo | investire, mettere sotto | |
| set up verbo | /ˌsɛt ˈʌp/ | preparare, installare |
La grammatica di questo video
Le strutture che chi parla usa di più, con le parole esatte del video:
| Struttura | Nel video |
|---|---|
| Forma passiva be + participio passato — conta ciò che accade, non chi lo fa | being cooled · was picked · is located |
| Frasi relative who / which + frase — un’informazione in più su una persona o una cosa | refrigerant, which is · heat which was · visit which is |
Pronuncia a cui fare attenzione
Chi parla usa 9 contrazioni e forme ridotte, come can't, doesn't, I'll. Pronunciale nella forma breve, così come le senti.
- I suoni “sh” e “zh”: evolution /ˌiːvəˈluːʃ(ə)n/, efficiency /ɪˈfɪʃ.ən.si/, specially /ˈspɛʃəli/, technician /tɛkˈnɪʃən/
- Parole lunghe — attenzione all’accento: evolution /ˌiːvəˈluːʃ(ə)n/, efficiency /ɪˈfɪʃ.ən.si/, manually /ˈmænj(u)əliː/, refrigerator /ɹɪˈfɹɪd͡ʒ.əˌɹeɪ.tɚ/, evaporator /ɪˈvæp.ə.ɹeɪt.ɚ/
I suoni difficili per chi parla italiano:
- Consonante finale — senza aggiungere una vocale dopo: liquid /ˈlɪk.wɪd/, valve /ˈvælv/, pipe /ˈpaɪp/, expand /ɪkˈspænd/, adjust /əˈd͡ʒʌst/
- /æ/ — più aperta della “e”: valve /ˈvælv/, expand /ɪkˈspænd/, calculate /ˈkælkjʊleɪt/, ambient /ˈæm.bi.ənt/, absorb /æbˈsɔɹb/
Come esercitarsi con questo video
- Ascolta tutto il video una volta senza parlare e annota le parole che non conosci.
- Inizia a velocità 0,75×, fai shadowing frase per frase e torna alla velocità normale quando diventa facile.
- Registrati e confronta con l’originale, facendo attenzione a parole come liquid, valve, boil.
Cos'è la tecnica dello Shadowing?
Shadowing è una tecnica di apprendimento delle lingue supportata da studi scientifici, originariamente sviluppata per la formazione dei traduttori professionisti e resa popolare dal poliglotta Dr. Alexander Arguelles. Il metodo è semplice ma potente: ascolti un audio in inglese di madrelingua e lo ripeti immediatamente ad alta voce — come un'ombra che segue il parlante con un ritardo di solo 1–2 secondi. A differenza dell'ascolto passivo o degli esercizi di grammatica, lo shadowing costringe il tuo cervello e i muscoli della bocca a elaborare e riprodurre simultaneamente i modelli di discorso reale. La ricerca dimostra che migliora significativamente la precisione della pronuncia, l'intonazione, il ritmo, il discorso connesso, la comprensione dell'ascolto e la fluidità del parlato — rendendolo uno dei metodi più efficaci per la preparazione alla prova di speaking dell'IELTS e per la comunicazione reale in inglese.