쉐도잉 연습: Centrifugal Pump Basics - How centrifugal pumps work working principle hvacr - 영상으로 영어 말하기 배우기

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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

100

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

101

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.

103

For example if we have an insulation

104

and we calculate the NPSH A as 11

105

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

106

However if we installed a pump

107

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.

110

We know that water boils at around 100 degrees Celsius

111

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

112

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

113

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

114

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

115

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.

118

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.

124

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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영어로 기술적 내용을 이해하고 표현하는 능력을 키우고 싶은 중급 이상 학습자에게 적합합니다. 특히 기계 공학이나 HVACR 분야에 관심이 있거나, 전문 용어를 사용한 설명을 듣고 말할 기회가 많은 사람들에게 유용합니다. 비디오에서 사용된 단어와 문장 구조는 실제 전문가 간의 대화에서 자주 등장하므로, 영상 영어 공부를 통해 실용적인 언어 실력을 쌓을 수 있습니다.

배워서 쓸 수 있는 단어와 표현

Centrifugal force: 원심력. "The impeller imparts centrifugal force onto the fluid"에서 사용된 바와 같이, 유체를 움직이는 힘을 설명할 때 필수적인 용어입니다.
Induction motor: 유도 전동기. 전기 에너지를 기계 에너지로 변환하는 장치를 가리키며, 기계 관련 설명에서 자주 등장합니다.
Coupling: 커플링. "Separated shafts are joined using a connection known as a coupling"에서와 같이, 두 축을 연결하는 부품을 말합니다.
Stator & Rotor: 고정자와 회전자. 전동기의 주요 구성 요소로, "the stator holds the copper coils"와 "the rotor rotates"와 같이 사용됩니다.

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이 비디오의 스피커는 명료한 미국 영어 발음을 사용하며, 기술적 용어를 발음할 때 강세를 명확히 합니다. shadow speech 또는 영어 쉐도잉을 연습할 때는 다음 점을 주의하세요. 첫째, "centrifugal" (sen-TRIF-yoo-guhl)과 같이 중간 강세가 있는 단어는 올바른 위치에 강세를 두어야 합니다. 둘째, "impeller" (im-PEL-er)나 "casing" (KAY-sing)과 같은 단어의 끝 소리가 흐리지 않게 발음합니다. 셋째, 문장 전체의 리듬을 따라가며, "The motor is an electrical induction motor, which allows us to convert..."와 같은 긴 문장에서 쉼표의 위치에서 약간의 휴지를 가져가면 자연스러운 발음이 됩니다. shadowing site를 이용해 반복적으로 연습하면, 기술적 내용을 말할 때의 자신감도 높아질 것입니다.

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문형	영상 속 표현
수동태 be + 과거분사 — 누가 하는지보다 무슨 일이 일어나는지에 초점	are joined · is enclosed · is connected
관계절 who / which + 절 — 사람이나 사물에 대한 추가 정보	coils which are · along which is · vanes which will
현재완료 have/has + 과거분사 — 과거의 일이 지금도 관련이 있을 때	has reached · has reduced

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쉐도잉(Shadowing)은 원래 전문 통역사 훈련을 위해 개발된 언어 학습 기법으로, 다언어 학자인 Dr. Alexander Arguelles에 의해 대중화된 방법입니다. 핵심 원리는 간단하지만 매우 강력합니다: 원어민의 영어를 들으면서 1~2초의 짧은 지연으로 즉시 소리 내어 따라 말하는 것——마치 '그림자(shadow)'처럼 화자를 따라가는 것입니다. 문법 공부나 수동적인 청취와 달리, 쉐도잉은 뇌와 입 근육이 동시에 실시간으로 영어를 처리하고 재현하도록 훈련합니다. 연구에 따르면 이 방법은 발음 정확도, 억양, 리듬, 연음, 청취력, 말하기 유창성을 크게 향상시킵니다. IELTS 스피킹 준비와 자연스러운 영어 소통을 원하는 분들에게 특히 효과적입니다.

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쉐도잉 연습: Centrifugal Pump Basics - How centrifugal pumps work working principle hvacr - 영상으로 영어 말하기 배우기

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