Prática de Shadowing: Air Conditioning System Basics hvacr how does it work - Aprenda a falar inglês com vídeo
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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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Vocabulário e dicas de fala para esta lição
Esta aula de conversação usa o vídeo “Air Conditioning System Basics hvacr how does it work”. As palavras que mais se repetem: refrigerant, liquid, valve, heat, evaporator. Este vídeo tem 85 frases e 1097 palavras para praticar shadowing. A fala dura 7:15. O falante fala em ritmo natural, cerca de 151 palavras por minuto, próximo de uma conversa do dia a dia. Apenas 77% das palavras estão entre as 3.000 mais comuns do inglês, por isso o vocabulário é exigente.
Vocabulário principal deste vídeo
15 palavras do vídeo que vale a pena aprender, com pronúncia e significado:
| Palavra | Pronúncia | Significado |
|---|---|---|
| liquid substantivo | /ˈlɪk.wɪd/ | líquido |
| valve substantivo | /ˈvælv/ | válvula |
| boil verbo | /bɔɪ(ə)l/ | ferver |
| pipe substantivo | /ˈpaɪp/ | flauta |
| vapor substantivo | /ˈveɪpɚ/ | vapor |
| mixture substantivo | /ˈmɪkst͡ʃɚ/ | mistura, misturação |
| spray substantivo | /spɹeɪ/ | borrifo, spray |
| adjust verbo | /əˈd͡ʒʌst/ | ajustar |
| regulate verbo | /ˈɹɛɡ.jə.leɪt/ | regular |
| evolution substantivo | /ˌiːvəˈluːʃ(ə)n/ | evolução |
| pump substantivo | /pʌmp/ | bomba |
| calculate verbo | /ˈkælkjʊleɪt/ | calcular |
| ambient adjetivo | /ˈæm.bi.ənt/ | ambiente |
| stable substantivo | /ˈsteɪ.bəl/ | estábulo, cavalariça |
| chart substantivo | /t͡ʃɑɹt/ | carta náutica |
Phrasal verbs que você vai ouvir
| Palavra | Pronúncia | Significado |
|---|---|---|
| pick up verbo | pegar | |
| run down verbo | atropelar | |
| set up verbo | /ˌsɛt ˈʌp/ | preparar |
Gramática neste vídeo
As estruturas que o falante mais usa, com as palavras exatas do vídeo:
| Estrutura | No vídeo |
|---|---|
| Voz passiva be + particípio passado — o foco está no que acontece, não em quem faz | being cooled · was picked · is located |
| Orações relativas who / which + oração — informação extra sobre uma pessoa ou coisa | refrigerant, which is · heat which was · visit which is |
Pronúncia para ficar de olho
O falante usa 9 contrações e formas reduzidas, como can't, doesn't, I'll. Diga-as na forma curta, do jeito que você ouve.
- Os sons de “sh” e “zh”: evolution /ˌiːvəˈluːʃ(ə)n/, efficiency /ɪˈfɪʃ.ən.si/, specially /ˈspɛʃəli/, technician /tɛkˈnɪʃən/
- Palavras longas — acerte a sílaba tônica: evolution /ˌiːvəˈluːʃ(ə)n/, efficiency /ɪˈfɪʃ.ən.si/, manually /ˈmænj(u)əliː/, refrigerator /ɹɪˈfɹɪd͡ʒ.əˌɹeɪ.tɚ/, evaporator /ɪˈvæp.ə.ɹeɪt.ɚ/
Sons difíceis para falantes de português:
- Consoante final — sem acrescentar um “i” depois: liquid /ˈlɪk.wɪd/, pipe /ˈpaɪp/, expand /ɪkˈspænd/, adjust /əˈd͡ʒʌst/, regulate /ˈɹɛɡ.jə.leɪt/
- /l/ final — a língua toca o céu da boca, não vira “u”: boil /bɔɪ(ə)l/, stable /ˈsteɪ.bəl/, ideal /aɪˈdi(ə)l/, bicycle /ˈbaɪsɪk(ə)l/, optimal /ˈɑptɪməl/
- s + consoante no início — sem um “i” antes: spray /spɹeɪ/, stable /ˈsteɪ.bəl/, sponsor /ˈspɒn.səː/, specially /ˈspɛʃəli/, squeeze /skwiːz/
Como praticar com este vídeo
- Ouça o vídeo inteiro uma vez sem falar e anote as palavras que você não conhece.
- Comece na velocidade 0,75×, faça shadowing frase por frase e volte à velocidade normal quando ficar fácil.
- Grave a sua voz e compare com o original, prestando atenção a palavras como liquid, valve, boil.
O que é a Técnica de Shadowing?
Shadowing é uma técnica de aprendizado de idiomas com base científica, originalmente desenvolvida para o treinamento de intérpretes profissionais. O método é simples, mas poderoso: você ouve áudio em inglês nativo e repete imediatamente em voz alta — como uma sombra seguindo o falante com 1-2 segundos de atraso. Pesquisas mostram melhora significativa na precisão da pronúncia, entonação, ritmo, sons conectados, compreensão auditiva e fluência na fala.