跟读练习: Air Conditioning System Basics hvacr how does it work - 通过视频学习英语口语
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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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本课的词汇与口语要点
这节口语课以视频“Air Conditioning System Basics hvacr how does it work”为素材。 视频中反复出现的词有：refrigerant, liquid, valve, heat, evaporator。 这段视频共有 85 个句子、1097 个单词可供跟读。 讲话部分时长为 7:15。 说话人语速自然，每分钟约 151 个词，接近日常对话。 只有 77% 的单词属于英语最常用的 3,000 词，词汇难度较高。
视频中的重点词汇
视频中 15 个值得学习的单词，附发音和释义：
| 单词 | 发音 | 释义 |
|---|---|---|
| liquid 名词 | /ˈlɪk.wɪd/ | 液體 /液体, 液態 /液态 |
| valve 名词 | /ˈvælv/ | 閥門 /阀门 |
| boil 动词 | /bɔɪ(ə)l/ | 煮沸, 煮 |
| pipe 名词 | /ˈpaɪp/ | 笛子, 管子 |
| vapor 名词 | /ˈveɪpɚ/ | 蒸氣 /蒸气 |
| expand 动词 | /ɪkˈspænd/ | 擴展 /扩展, 擴張 /扩张 |
| mixture 名词 | /ˈmɪkst͡ʃɚ/ | 混合 |
| spray 名词 | /spɹeɪ/ | 噴霧器 /喷雾器 |
| adjust 动词 | /əˈd͡ʒʌst/ | 調整 /调整 |
| regulate 动词 | /ˈɹɛɡ.jə.leɪt/ | 調節 /调节 |
| evolution 名词 | /ˌiːvəˈluːʃ(ə)n/ | 演變 /演变, 變遷 /变迁 |
| pump 名词 | /pʌmp/ | 泵, 唧筒 |
| calculate 动词 | /ˈkælkjʊleɪt/ | 計算 /计算, 算 |
| ambient 形容词 | /ˈæm.bi.ənt/ | 氛圍 /氛围 |
| stable 名词 | /ˈsteɪ.bəl/ | 馬厩, 馬棚 /马棚 |
视频中出现的短语动词
| 单词 | 释义 |
|---|---|
| pick up 动词 | 拾取, 撿 /捡 |
| heat up 动词 | 加熱 /加热 |
视频中的语法
说话人最常用的结构，并附上视频中的原话：
| 结构 | 视频中的用法 |
|---|---|
| 被动语态 be + 过去分词 — 强调发生了什么，而不是谁做的 | being cooled · was picked · is located |
| 定语从句 who / which + 从句 — 补充说明人或事物 | refrigerant, which is · heat which was · visit which is |
需要注意的发音
说话人用了 9 次缩略和弱读形式，例如 can't, doesn't, I'll。请按听到的简短形式来说。
- “sh” 和 “zh” 音: evolution /ˌiːvəˈluːʃ(ə)n/, efficiency /ɪˈfɪʃ.ən.si/, specially /ˈspɛʃəli/, technician /tɛkˈnɪʃən/
- 长单词——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/
中文母语者容易读错的音：
- /v/ — 不要读成 /w/，上齿轻触下唇: valve /ˈvælv/, vapor /ˈveɪpɚ/, evolution /ˌiːvəˈluːʃ(ə)n/, evaporator /ɪˈvæp.ə.ɹeɪt.ɚ/, evaporate /ɪˈvæp.ə.ɹeɪt/
- 词尾辅音 — 要读清楚，后面不要加元音: liquid /ˈlɪk.wɪd/, valve /ˈvælv/, pipe /ˈpaɪp/, expand /ɪkˈspænd/, adjust /əˈd͡ʒʌst/
- /r/ 和 /l/ 的区别: regulate /ˈɹɛɡ.jə.leɪt/, controller /kənˈtɹoʊlɚ/, droplet /ˈdɹɑplət/
如何用这段视频练习
- 先完整听一遍视频，不要开口，记下不认识的单词。
- 先用 0.75 倍速逐句跟读，熟练之后再回到正常速度。
- 录下自己的声音并与原声对比，特别注意 liquid, valve, boil 这类单词。
什么是跟读法？
跟读法 (Shadowing) 是一种有科学依据的语言学习技巧，最初开发用于专业口译员的培训，并由多语言者Alexander Arguelles博士普及。这个方法简单而强大：您在听英语母语原声的同时立即大声重复——就像是一个延迟1-2秒紧跟说话者的影子。与被动听力或语法练习不同，跟读法强迫您的大脑和口腔肌肉同时处理并模仿真实的讲话模式。研究表明它能显着提高发音准确性，语调，节奏，连读，听力理解和口语流利度——使其成为雅思口语备考和真实英语交流最有效的方法之一。