跟讀練習: Air Conditioning System Basics hvacr how does it work - 通過影片學習英語口語

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sponsored by danfoss when we look at a typical refrigeration system we have the compressor

the condenser the expansion valve and the evaporator the condenser

and the evaporator are both heat exchangers the condenser sits outside the property

and the evaporator sits inside the room being cooled the compressor circulates a refrigerant in the pipe work

which cycles between all of these components the expansion valve regulates

the flow of refrigerant the refrigerant is a specially designed fluid

which can change between being a liquid and a gas very easily and that's

because it has a very low boiling point for example refrigerant

are for 10 a will boil at negative 48 degrees Celsius

or negative 55 degrees Fahrenheit although this will change with pressure

but if the refrigerant is inside a pipe within a room

and the room is at 30 degrees Celsius

or 86 degrees Fahrenheit then this will be more than enough to cause it to boil from a liquid into a vapor.

By the way if you want some refrigerant charts you can download these for free from our website.

I'll link to these in the video description down below.

So the The refrigerant is entering the evaporator as a low pressure, low temperature liquid vapor mixture.

It flows on the inside of the pipe

and at the same time a fan is moving the ambient air of the room over the outside of the pipe.

This causes the refrigerant to boil.

It will absorb the heat from the air through the pipe wall and then it evaporates.

As the refrigerant evaporates, it carries away the heat.

It's similar to when we boiled water.

The water heats up, it evaporates and turns into steam and carries this heat away.

So the air on the outside is entering hot and it's leaving cold.

The refrigerant continues to travel through the evaporator, picking up more heat which boils it further until it becomes slightly superheated.

This basically means it's now completely gas and doesn't contain any droplets of liquid refrigerant.

Liquid damages the compressor, so we want to ensure it can't reach the compressor.

The compressor sucks in the refrigerant, which is leaving the evaporator as a low -pressure, low -temperature, slightly superheated vapour.

It then squeezes this together into a much smaller space, and so the pressure increases.

All the heat which was picked up in the evaporator is now contained in a much smaller volume, so the temperature will increase.

This is very important and we will see why in just a moment.

But if you've ever pumped up a bicycle tyre, you will notice the pump becomes hotter as it's compressing the air.

The refrigerant is then pushed into the condenser where it enters as a high -pressure, high -temperature, superheated vapour.

the condenser is located outside

and the outside air might be very warm on a summer's

day as heat always flows from hot to cold we need to ensure

that the refrigerant is hotter than the outside air otherwise the

unwanted heat will not be able to leave the refrigerant and leave our system

a fan will help to blow ambient air over the condenser to remove this heat

so the outside air is entering warm picking up heat

and leaving hot as the heat is removed by the air

this causes the refrigerant to condense back into a liquid it's a little bit like

when steam hits the window on a cold day the window is cold

so it condenses the steam from a vapor into a liquid

and then this liquid starts to run down the window the

refrigerant therefore exits as a high pressure medium temperature saturated liquid

and this heads to the expansion valve the expansion valve needs

to regulate the amount of refrigerant entering the evaporator to control the superheat

if it allows too much refrigerant to flow it can flood the evaporator

so the refrigerant doesn't evaporate a liquid reaches the compressor

and possibly destroys it but

if it lets in too little refrigerant the system won't provide enough cooling and

so it operates inefficiently the expansion valve regulates the refrigerant by

only allowing it to pass through a small hole this creates

a large pressure difference across the valve one side is the high -pressure liquid the other side is almost empty

The small hole causes it to almost spray into the evaporator as a part liquid, part vapor mixture.

The refrigerant will expand to try and fill the empty space on the other side

and this will cause it to drop in pressure as well as temperature.

It's a little bit like spraying a deodorant can or a spray paint can.

It flows through a small hole causing it to expand as a part vapor

and part liquid mixture

and then we can feel the can become cooler now the

original method to control this was by using a fixed orifice device

and you might still find these on the back of your

refrigerators the hole within this device was a fixed size

so the entire system would simply turn on

and off to meet the cooling demand it does work

but we can't maintain a stable temperature control

because the system is simply turning on

and off the next evolution was the thermostatic expansion valve this is still widely used today

and it senses the superheat at the outlet through a bulb

which is filled with another refrigerant this other refrigerant will expand to close the valve

when the superheat is too high and it condenses to open the valve when the superheat is too low.

This type of valve needs to be manually calculated and adjusted by a technician.

It does work very well but it's prone to mistakes.

It also takes a long time to calculate and set up

and it is also only adjusted once per service visit which is not ideal.

It will also not allow peak performance.

However it does work very well and these will continue to be used for many years.

And And so the latest evolution is to use electronic expansion valves.

These use a controller to measure the exact temperature and pressure

and adjust the valve position automatically in real time to ensure optimal performance and maximum system efficiency.

Okay that's it for this video but to continue learning about HVAC

and refrigeration engineering click on one of the videos on screen now and I'll catch you there for the next lesson.

Don't forget to follow us on Facebook, Twitter, LinkedIn, Instagram as well as theengineeringmindset .com

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本課的詞彙與口語要點

這節口語課以影片“Air Conditioning System Basics hvacr how does it work”為素材。影片中反覆出現的詞有：refrigerant, liquid, valve, heat, evaporator。這段影片共有 85 個句子、1097 個單詞可供跟讀。講話部分時長為 7:15。說話人語速自然，每分鐘約 151 個詞，接近日常對話。只有 77% 的單詞屬於英語最常用的 3,000 詞，詞彙難度較高。

影片中的重點詞彙

影片中 15 個值得學習的單詞，附發音和釋義：

單詞	發音	釋義
liquid 名詞	/ˈlɪk.wɪd/	液體 /液體, 液態 /液態
valve 名詞	/ˈvælv/	閥門 /閥門
boil 動詞	/bɔɪ(ə)l/	煮沸, 煮
pipe 名詞	/ˈpaɪp/	笛子, 管子
vapor 名詞	/ˈveɪpɚ/	蒸氣 /蒸氣
expand 動詞	/ɪkˈspænd/	擴充套件 /擴充套件, 擴張 /擴張
mixture 名詞	/ˈmɪkst͡ʃɚ/	混合
spray 名詞	/spɹeɪ/	噴霧器 /噴霧器
adjust 動詞	/əˈd͡ʒʌst/	調整 /調整
regulate 動詞	/ˈɹɛɡ.jə.leɪt/	調節 /調節
evolution 名詞	/ˌiːvəˈluːʃ(ə)n/	演變 /演變, 變遷 /變遷
pump 名詞	/pʌmp/	泵, 唧筒
calculate 動詞	/ˈkælkjʊleɪt/	計算 /計算, 算
ambient 形容詞	/ˈæm.bi.ənt/	氛圍 /氛圍
stable 名詞	/ˈsteɪ.bəl/	馬廄, 馬棚 /馬棚

影片中出現的短語動詞

單詞	釋義
pick up 動詞	拾取, 撿 /撿
heat up 動詞	加熱 /加熱

影片中的語法

說話人最常用的結構，並附上影片中的原話：

結構	影片中的用法
被動語態 be + 過去分詞 — 強調發生了什麼，而不是誰做的	being cooled · was picked · is then pushed
定語從句 who / which + 從句 — 補充說明人或事物	refrigerant, which is · heat which was · visit which is

需要注意的發音

說話人用了 9 次縮略和弱讀形式，例如 can't, doesn't, I'll。請按聽到的簡短形式來說。

“sh” 和 “zh” 音: evolution /ˌiːvəˈluːʃ(ə)n/, efficiency /ɪˈfɪʃ.ən.si/, specially /ˈspɛʃəli/, technician /tɛkˈnɪʃən/
長單詞——注意重音位置: evolution /ˌiːvəˈluːʃ(ə)n/, efficiency /ɪˈfɪʃ.ən.si/, manually /ˈmænj(u)əliː/, refrigerator /ɹɪˈfɹɪd͡ʒ.əˌɹeɪ.tɚ/, evaporator /ɪˈvæp.ə.ɹeɪt.ɚ/

中文母語者容易讀錯的音：

/v/ — 不要讀成 /w/，上齒輕觸下唇: valve /ˈvælv/, vapor /ˈveɪpɚ/, evolution /ˌiːvəˈluːʃ(ə)n/, evaporator /ɪˈvæp.ə.ɹeɪt.ɚ/, evaporate /ɪˈvæp.ə.ɹeɪt/
詞尾子音 — 要讀清楚，後面不要加母音: liquid /ˈlɪk.wɪd/, valve /ˈvælv/, pipe /ˈpaɪp/, expand /ɪkˈspænd/, adjust /əˈd͡ʒʌst/
/r/ 和 /l/ 的區別: regulate /ˈɹɛɡ.jə.leɪt/, controller /kənˈtɹoʊlɚ/, droplet /ˈdɹɑplət/

如何用這段影片練習

先完整聽一遍影片，不要開口，記下不認識的單詞。
先用 0.75 倍速逐句跟讀，熟練之後再回到正常速度。
錄下自己的聲音並與原聲對比，特別注意 liquid, valve, boil 這類單詞。

什麼是跟讀法？

跟讀法 (Shadowing) 是一種有科學依據的語言學習技巧，最初開發用於專業口譯員的培訓，並由多語言者Alexander Arguelles博士普及。這個方法簡單而強大：您在聽英語母語原聲的同時立即大聲重複——就像是一個延遲1-2秒緊跟說話者的影子。與被動聽力或語法練習不同，跟讀法強迫您的大腦和口腔肌肉同時處理並模模擬實的講話模式。研究表明它能顯著提高發音準確性，語調，節奏，連讀，聽力理解和口語流利度——使其成為雅思口語備考和真實英語交流最有效的方法之一。

影子跟讀法: 閱讀完整分步指南 →

跟讀練習: Air Conditioning System Basics hvacr how does it work - 通過影片學習英語口語

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