シャドーイング練習: Centrifugal Pump Basics - How centrifugal pumps work working principle hvacr - 動画で英語スピーキングを学ぶ

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Hey there guys, Paul here from TheEngineeringMindset .com.

In this video, we're going to be looking at centrifugal pumps to learn the basics of how they work, the different types and where we use them.

You can get more information on centrifugal pumps, shop for parts and accessories or talk to experts on top pump brands like Bell & Gossett,

Taco and more by visiting Statesupplier .com who have kindly sponsored this video.

Simply click on the link in the video description down below to find out more.

Centrifugal pumps come in many shapes, colors, and sizes, but they typically look something like this.

The pumps consist of two main parts, the pump and the motor.

The motor is an electrical induction motor, which allows us to convert electrical energy into mechanical energy.

This mechanical energy is used to drive the pump and move the water.

The pump pulls water in through the inlet

and pushes it out through the outlet as we take the unit apart we can see

that we have a fan

and a protective casing mounted at the back of the electrical

motor then inside the motor we have the stator the stator holds the copper coils

and we're going to look in detail at that a little later in this video

concentric to this we have the rotor and shaft the rotor rotates

and as it rotates so does the shaft the shaft runs the entire length from the motor and into to the pump.

This then connects into the pump's impeller.

Some models of centrifugal pumps, like this one, will have a separate shaft for the pump and the motor.

Separated shafts are joined using a connection known as a coupling.

Coupled pumps will usually have a bearing house which, as the name suggests, houses the bearings.

The shaft continues into the pump casing.

As it enters the casing, it passes through a gland, packing, and the stuffing box, which combine to form a seal.

The shaft then connects onto the impeller.

The impeller imparts centrifugal force onto the fluid which enables us to move liquids, such as water, through a pipe.

The impeller is enclosed within the pump casing.

The casing contains and directs the flow of water as the impeller pulls it in and pushes it out.

Therefore, we have a suction inlet and a discharge outlet.

At the back of the electrical motor, we see that the fan is connected to the shaft.

When the motor rotates the shaft, the fan will therefore also rotate.

The fan is used to cool down the electrical motor

and it will blow ambient air over the casing to dissipate the unwanted heat.

If the motor becomes too hot, the insulation on the coils inside the motor will melt, causing the motor to short circuit and destroy itself.

The fins on the outside perimeter of the casing increase the surface area of the casing

which allows us to remove more unwanted heat.

The electrical motor comes in either three phase or single phase configuration depending on the application.

We're going to look at three phase as this is the most common.

Inside the three phase induction motor, we have three separated coils which are wound around the stator.

Each coil set is connected to a different phase to produce a rotating magnetic field.

When we pass AC or alternating current through each coil, the coil will produce an electromagnetic field

which changes in intensity as well as polarity as the electrons passing through it change direction between forwards and backwards.

But if we connect each coil to a different phase then the electrons will change direction between forwards

and backwards at a different time compared to the other phases.

This means

that the magnetic field of each coil will change in intensity

as well as polarity at a different time compared to the other phases.

To distribute this magnetic field we rotate the coils 120 degrees from the previous phase

and insert them into the stator of the motor casing.

This will create the effect of a rotating magnetic field.

At the center of the stator we place the rotor and shaft.

The rotor will be affected by the rotating magnetic field and will force it to also rotate.

The rotor is connected to the shaft

and the shaft runs from the fan through the rotor all the way up to the impeller.

This way when the rotor rotates so will the impeller.

So now by creating the rotating magnetic field within the motor we spin the rotor

which spins the shaft and this spins the impeller.

Looking at the pump casing we find a channel for water to flow along which is called the volute.

This volute spirals around the perimeter of the casing up to the pump outlet.

This channel increases in diameter as it makes its way to the outlet.

The shaft passes through the seals and into the pump casing where it connects to the impeller.

There are many types of impeller, but most will have these backward curved vanes which will either be open, semi -open, or closed with some shrouds.

These backward curved vanes do not push the water.

The curves rotate with the outer edge moving in the direction of the expanding volute.

These vanes will provide the fluid with a smooth path for the water to flow.

We'll see that a little later in this video.

The impeller is submerged in water.

When the impeller rotates, the water within the impeller also rotates.

As the water rotates, the liquid is radially pushed out in all directions to the edge of the impeller

and into the volute.

As the water moves outwards off the impeller, it creates a region of low pressure which pulls more water in through the suction inlet.

The water enters into the eye of the impeller and it's trapped there between the blades.

As the impeller rotates, it imparts kinetic energy or velocity onto the water.

By the time the water reaches the edge of the impeller, it has reached a very high velocity.

This high speed water flows off the impeller and into the volute, where it hits the wall of the pump casing.

This impact converts the velocity into potential energy or pressure.

More water follows behind this and so a flow develops.

The volute channel has an expanding diameter as it spirals around the circumference of the pump casing.

As it expands, the velocity of the water will decrease, resulting in pressure increasing.

This expanding channel therefore allows more water to keep joining and converting into pressure.

So the discharge outlet is therefore a higher pressure than the suction inlet.

The high pressure at the discharge allows us to force the fluid through pipes

and into a storage tank or around a pipe system.

The thickness of the impeller and the rotational speed affects the volume flow rate from the pump.

But the diameter of the impeller and the rotational speed will increase the pressure it can produce.

Centrifugal pumps are represented in engineering drawings with symbols like these.

They can vary slightly from this, so do check the drawings information section.

NPSH A term you're going to hear is the NPSH, which is the acronym for Net Positive Suction Pressure.

We'll briefly cover what this means.

There are two letters at the end of the acronym, the NPSHR and the NPSHA.

The R is the required NPSH.

Each pump is tested for this value, and this can be obtained from the pump manufacturer by the pump's operating chart.

Don't worry about this confusing looking chart at this point, we're going to break it down and cover that in detail in a dedicated video.

Links to that in the video description down below.

The R value is basically a warning or danger point.

As the water enters the pump and flows into the impeller's eye, it experiences a lot of energy due to the friction.

This will give us a pressure drop.

at certain conditions the water flowing through this section can reach boiling point

when this occurs we refer to this as cavitation we're going to see more on that in just a moment

the other letter was the a

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and this is the mpsh available this depends on the insulation of the pump

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and needs to be calculated it considers things such as insulation type

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and elevation liquid temperature liquid boiling point etc the available pressure should always be higher than the required value.

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For example if we have an insulation

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and we calculate the NPSH A as 11

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but the pump requires an NPSH R of 4 then the pump should be okay.

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However if we installed a pump

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that required an NPSH R of 13 then the available NPSH is insufficient and cavitation will occur.

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So what is cavitation?

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As we know water can turn from a liquid state into steam or a gas state.

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We know that water boils at around 100 degrees Celsius

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and that's because it's at sea level which has an atmospheric pressure of 101 .325 kPa.

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But if we went to the top of Mount Everest then water boils here at just 71 degrees Celsius

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and that's because the atmospheric pressure has reduced to 34 kPa.

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As the atmospheric pressure reduces it becomes easier for the water to boil.

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So at the suction inlet of the pump we know

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that there is going to be a pressure drop and

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if this pressure is less than the vapor pressure of the liquid being pumped then the water can reach boiling point.

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When this happens cavitation occurs.

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During cavitation air particles within the water will expand as they reach boiling point.

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These will then collapse in on themselves very rapidly.

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As they collapse they will damage the impeller as well as the pump casing.

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This remove small parts of metal from the surface and if this keeps occurring then it will eventually destroy the pump.

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Therefore we must ensure the available pressure is higher than the required pressure of the pump.

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We use centrifugal pumps everywhere.

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We use them to move liquids from one tank to another or around a system. For example,

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we might use a small in -line centrifugal pump in our domestic heating circuit to move heated water around the property.

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We might use a large centrifugal pump to move the condenser water from a chiller's condenser

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and up to the cooling tower on the roof as part of the centralized cooling system.

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We're going to look at the type of pumps and their application in our next video in this series.

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Okay, that's it for this video, but to continue your learning then check out one of the videos on screen now

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and I'll catch you there for the next lesson.

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Don't forget to follow us on Facebook, Twitter, Instagram as well as

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この動画で英語スピーキング練習する理由

機械工学の基礎知識を説明するこの動画は、shadow speech（シャドーイング）の理想的な教材です。話者は明瞭なアメリカ英語で、技術用語を含む説明を緩やかなペースで展開しています。日常会話だけでなく、専門的なコンテキストでのスピーキング能力を養うのに適しており、IELTS スピーキング対策にも役立ちます。また、「ポンプの構造」「電動機の原理」など、具体的なトピックを説明する際の語彙や文章構造を学べるため、実用的な英語力が身につきます。

文脈の中の文法と表現

「consist of」の使い方：「The pumps consist of two main parts...」のように、構成要素を説明する際に使われます。日本語の「～から成る」に相当し、技術的な説明で頻繁に登場します。
「which allows us to...」の関係代名詞節：「The motor... which allows us to convert electrical energy into mechanical energy.」のように、先行詞の働きや効果を説明する場合に使われます。この構造を使うと、文章がスムーズに繋がり、説明力が増します。
「as」による時間の表現：「As it rotates so does the shaft.」のように、2つの動作が同時に起こることを表します。「～すると同時に」という意味で、技術的なプロセスの説明に不可欠です。

発音の注意点

この動画にはいくつか発音が難しい単語があります。「centrifugal」（セントリフューガル）は語尾の「-gal」を強く発音せず、軽く「ガル」と言います。「impeller」（インペラー）は「インペラ」と短く発音することが多く、「ー」の音は弱めです。また、「stator」（ステーター）と「rotor」（ローター）の発音の違いに注意しましょう。「stator」は「ステーター」、「rotor」は「ローター」で、母音の長さが異なります。これらの単語を正しく発音することで、専門的な会話でのコミュニケーションがスムーズになります。

動画で英語学習する際は、シャドーイングを繰り返し行い、話者のリズムやイントネーションを真似ることが重要です。この動画を使ってshadowspeaksの練習を続けると、自然な英語の発音とスピーキング能力が向上します。

この動画の文法

話し手がよく使っている文型を、動画の実際の表現とともに紹介します。

文型	動画での表現
受動態 be + 過去分詞 — 誰がするかより、何が起きるかに焦点を当てる	are joined · is enclosed · is connected
関係詞節 who / which + 節 — 人や物について情報を加える	coils which are · along which is · vanes which will
現在完了形 have/has + 過去分詞 — 過去の出来事が今も関係している	has reached · has reduced

シャドーイングとは？英語上達に効果的な理由

シャドーイング（Shadowing）は、もともとプロの通訳者養成プログラムで開発された言語学習法で、多言語習得者として知られるDr. Alexander Arguelles によって広く普及されました。方法はシンプルですが非常に効果的：ネイティブスピーカーの英語を聞きながら、1〜2秒の遅延で声に出してすぐに繰り返す——まるで「影（shadow）」のように話者を追いかけます。文法ドリルや受動的なリスニングと異なり、シャドーイングは脳と口の筋肉が同時にリアルタイムで英語を処理・再現することを強制します。研究により、発音精度、抑揚、リズム、連音、リスニング力、そして会話の流暢さが大幅に向上することが確認されています。IELTSスピーキング対策や自然な英語コミュニケーションを目指す方に特におすすめです。

シャドーイングのやり方: ステップ別の完全ガイドを読む →

シャドーイング練習: Centrifugal Pump Basics - How centrifugal pumps work working principle hvacr - 動画で英語スピーキングを学ぶ

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この動画で英語スピーキング練習する理由

文脈の中の文法と表現

発音の注意点

この動画の文法

シャドーイングとは？英語上達に効果的な理由