ฝึกพูดภาษาอังกฤษด้วยเทคนิค Shadowing จากวิดีโอ: Centrifugal Pump Basics - How centrifugal pumps work working principle hvacr
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Hey there guys, Paul here from TheEngineeringMindset .com.
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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.
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You can get more information on centrifugal pumps, shop for parts and accessories or talk to experts on top pump brands like Bell & Gossett,
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Taco and more by visiting Statesupplier .com who have kindly sponsored this video.
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Simply click on the link in the video description down below to find out more.
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Centrifugal pumps come in many shapes, colors, and sizes, but they typically look something like this.
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The pumps consist of two main parts, the pump and the motor.
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The motor is an electrical induction motor, which allows us to convert electrical energy into mechanical energy.
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This mechanical energy is used to drive the pump and move the water.
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The pump pulls water in through the inlet
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and pushes it out through the outlet as we take the unit apart we can see
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that we have a fan
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and a protective casing mounted at the back of the electrical
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motor then inside the motor we have the stator the stator holds the copper coils
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and we're going to look in detail at that a little later in this video
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concentric to this we have the rotor and shaft the rotor rotates
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and as it rotates so does the shaft the shaft runs the entire length from the motor and into to the pump.
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This then connects into the pump's impeller.
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Some models of centrifugal pumps, like this one, will have a separate shaft for the pump and the motor.
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Separated shafts are joined using a connection known as a coupling.
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Coupled pumps will usually have a bearing house which, as the name suggests, houses the bearings.
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The shaft continues into the pump casing.
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As it enters the casing, it passes through a gland, packing, and the stuffing box, which combine to form a seal.
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The shaft then connects onto the impeller.
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The impeller imparts centrifugal force onto the fluid which enables us to move liquids, such as water, through a pipe.
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The impeller is enclosed within the pump casing.
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The casing contains and directs the flow of water as the impeller pulls it in and pushes it out.
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Therefore, we have a suction inlet and a discharge outlet.
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At the back of the electrical motor, we see that the fan is connected to the shaft.
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When the motor rotates the shaft, the fan will therefore also rotate.
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The fan is used to cool down the electrical motor
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and it will blow ambient air over the casing to dissipate the unwanted heat.
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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.
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The fins on the outside perimeter of the casing increase the surface area of the casing
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which allows us to remove more unwanted heat.
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The electrical motor comes in either three phase or single phase configuration depending on the application.
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We're going to look at three phase as this is the most common.
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Inside the three phase induction motor, we have three separated coils which are wound around the stator.
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Each coil set is connected to a different phase to produce a rotating magnetic field.
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When we pass AC or alternating current through each coil, the coil will produce an electromagnetic field
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which changes in intensity as well as polarity as the electrons passing through it change direction between forwards and backwards.
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But if we connect each coil to a different phase then the electrons will change direction between forwards
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and backwards at a different time compared to the other phases.
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This means
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that the magnetic field of each coil will change in intensity
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as well as polarity at a different time compared to the other phases.
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To distribute this magnetic field we rotate the coils 120 degrees from the previous phase
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and insert them into the stator of the motor casing.
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This will create the effect of a rotating magnetic field.
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At the center of the stator we place the rotor and shaft.
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The rotor will be affected by the rotating magnetic field and will force it to also rotate.
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The rotor is connected to the shaft
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and the shaft runs from the fan through the rotor all the way up to the impeller.
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This way when the rotor rotates so will the impeller.
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So now by creating the rotating magnetic field within the motor we spin the rotor
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which spins the shaft and this spins the impeller.
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Looking at the pump casing we find a channel for water to flow along which is called the volute.
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This volute spirals around the perimeter of the casing up to the pump outlet.
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This channel increases in diameter as it makes its way to the outlet.
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The shaft passes through the seals and into the pump casing where it connects to the impeller.
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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.
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These backward curved vanes do not push the water.
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The curves rotate with the outer edge moving in the direction of the expanding volute.
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These vanes will provide the fluid with a smooth path for the water to flow.
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We'll see that a little later in this video.
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The impeller is submerged in water.
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When the impeller rotates, the water within the impeller also rotates.
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As the water rotates, the liquid is radially pushed out in all directions to the edge of the impeller
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and into the volute.
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As the water moves outwards off the impeller, it creates a region of low pressure which pulls more water in through the suction inlet.
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The water enters into the eye of the impeller and it's trapped there between the blades.
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As the impeller rotates, it imparts kinetic energy or velocity onto the water.
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By the time the water reaches the edge of the impeller, it has reached a very high velocity.
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This high speed water flows off the impeller and into the volute, where it hits the wall of the pump casing.
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This impact converts the velocity into potential energy or pressure.
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More water follows behind this and so a flow develops.
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The volute channel has an expanding diameter as it spirals around the circumference of the pump casing.
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As it expands, the velocity of the water will decrease, resulting in pressure increasing.
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This expanding channel therefore allows more water to keep joining and converting into pressure.
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So the discharge outlet is therefore a higher pressure than the suction inlet.
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The high pressure at the discharge allows us to force the fluid through pipes
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and into a storage tank or around a pipe system.
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The thickness of the impeller and the rotational speed affects the volume flow rate from the pump.
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But the diameter of the impeller and the rotational speed will increase the pressure it can produce.
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Centrifugal pumps are represented in engineering drawings with symbols like these.
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They can vary slightly from this, so do check the drawings information section.
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NPSH A term you're going to hear is the NPSH, which is the acronym for Net Positive Suction Pressure.
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We'll briefly cover what this means.
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There are two letters at the end of the acronym, the NPSHR and the NPSHA.
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The R is the required NPSH.
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Each pump is tested for this value, and this can be obtained from the pump manufacturer by the pump's operating chart.
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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.
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Links to that in the video description down below.
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The R value is basically a warning or danger point.
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As the water enters the pump and flows into the impeller's eye, it experiences a lot of energy due to the friction.
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This will give us a pressure drop.
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at certain conditions the water flowing through this section can reach boiling point
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when this occurs we refer to this as cavitation we're going to see more on that in just a moment
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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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เกี่ยวกับบทเรียนนี้
ในบทเรียนนี้ คุณจะได้เรียนรู้เกี่ยวกับการทำงานของปั๊มเซ็นทริฟูจัล ซึ่งเป็นอุปกรณ์ที่สำคัญในหลายสาขา โดยเฉพาะในระบบ HVACR คุณจะได้ฝึกฟังและพูดตามการสนทนาในวิดีโอ ซึ่งจะช่วยให้คุณ ปรับปรุงการออกเสียงภาษาอังกฤษ ได้อย่างมีประสิทธิภาพ นอกจากนี้ยังมีข้อมูลเกี่ยวกับส่วนต่างๆ ของปั๊มและรายละเอียดการทำงาน เพื่อให้คุณเข้าใจและสามารถนำไปใช้ในภาษาอังกฤษได้ดีขึ้น
คำศัพท์และวลีสำคัญ
- centrifugal pump - ปั๊มเซ็นทริฟูจัล
- motor - มอเตอร์
- impeller - อิมเพลเลอร์
- inlet - ช่องเข้าของน้ำ
- outlet - ช่องออกของน้ำ
- cooling fan - พัดลมระบายความร้อน
- electromagnetic field - สนามแม่เหล็กไฟฟ้า
- shaft - แชฟต์
เคล็ดลับการฝึก
การฝึก ชาโดว์อิ้งภาษาอังกฤษ หรือ shadow speak เป็นวิธีที่ยอดเยี่ยมในการพัฒนาทักษะการพูดของคุณ โดยเฉพาะเมื่อคุณฟังบทสนทนาจากวิดีโอนี้ คุณควรเริ่มต้นโดยการฟังเนื้อหาอย่างตั้งใจ จากนั้นให้พยายามพูดตามในจังหวะและน้ำเสียงเดียวกับผู้พูด แม้ว่าจะมีความเร็วที่แตกต่างกันบ้าง แต่การฝึกซ้ำ ๆ จะช่วยให้คุณสามารถจับจังหวะและพัฒนาความมั่นใจในการพูดภาษาอังกฤษได้อย่างรวดเร็ว
อย่าลืมว่า ความสำเร็จในการเรียนรู้ เรียนภาษาอังกฤษจากวิดีโอ ขึ้นอยู่กับความตั้งใจและการฝึกฝนอย่างต่อเนื่อง การทำให้การฝึกเป็นส่วนหนึ่งของกิจวัตรประจำวันจะช่วยให้คุณเห็นความก้าวหน้าอย่างรวดเร็ว!
ไวยากรณ์ในวิดีโอนี้
โครงสร้างที่ผู้พูดใช้บ่อยที่สุด พร้อมคำพูดจริงจากวิดีโอ:
| โครงสร้าง | ในวิดีโอ |
|---|---|
| Passive voice be + กริยาช่อง 3 — เน้นสิ่งที่เกิดขึ้น ไม่ใช่ผู้กระทำ | are joined · is enclosed · is connected |
| Relative clauses who / which + อนุประโยค — ข้อมูลเพิ่มเติมเกี่ยวกับคนหรือสิ่งของ | coils which are · along which is · vanes which will |
| Present perfect have/has + กริยาช่อง 3 — เหตุการณ์ในอดีตที่ยังเกี่ยวข้องกับปัจจุบัน | has reached · has reduced |
เทคนิค Shadowing คืออะไร?
Shadowing เป็นเทคนิคการเรียนรู้ภาษาที่ได้รับการรับรองทางวิทยาศาสตร์ พัฒนาขึ้นสำหรับการฝึกนักแปลมืออาชีพ วิธีการนี้เรียบง่ายแต่ทรงพลัง: คุณฟังเสียงภาษาอังกฤษจากเจ้าของภาษาและพูดตามทันที — เหมือนเงาที่ตามผู้พูดด้วยช่วงเวลาห่าง 1-2 วินาที การวิจัยแสดงว่าเทคนิคนี้ปรับปรุงความแม่นยำในการออกเสียง ทำนองเสียง จังหวะ การเชื่อมเสียง การฟังเข้าใจ และความคล่องแคล่วในการพูดได้อย่างมีนัยสำคัญ