Name: fire extinguisher nozzle flow and pressure
Uploaded: 2025-02-13T15:43:18.000Z
Duration: 1 min 12 s
Channel: JoVE

消火器は、加圧水を使用してノズルから強力な流れを発生させます。
内部の水は周囲の大気よりもはるかに高い圧力で貯蔵されているため、消火器が作動すると水が強制的に流れます。
流体力学方程式を適用して、水がノズルから出る速度と、時間の経過とともにどれだけ排出されるかを決定します。
最初のステップは、消火器の内部とノズルの外側の圧力との間の圧力差を理解することです。
この圧力差が水の動きを駆動します。圧力と速度に関連するベルヌーイ方程式を適用することにより、ノズルから出る水の速度が計算されます。
ノズルの直径が小さいと、水が出るときに加速し、圧力が速度に変換されます。
出口速度を計算した後、流量が決定されます。流量は連続方程式を使用して計算され、ノズルを流れる水の量が一定であることを保証します。
流量は、水の速度にノズルの断面積を掛けて計算されます。

設計例: 消火器の流れ

Design Example: Flow Through a Fire Extinguisher

加圧水を使用する消火器は、流体力学の原理を利用して、炎を鎮火できる高速の流れを生成します。消火器内の水は、周囲の大気よりもはるかに高い圧力で貯蔵されます。この圧力差により、消火器が作動すると水が急速に流れ、ノズルから出る水の動きは流体力学の基本方程式を使用して理解できます。

 水がどのように加速するかを理解する鍵は、消火器の内部と外部環境の圧力差にあります。圧力と速度を関連付けるベルヌーイの方程式は、水がノズルから出る速度を計算します。

<img alt="Equation 1" src="/files/ftp_upload/18047/18047_Equation_1.svg" style="text-align: center; height: 45px;">

 この原理によると、圧力が低下すると速度が増加します。つまり、消火器内の高い内部圧力が、流出する水の速度に変換されます。水がノズルに近づくと、ノズルの直径が小さくなるため、流れがさらに加速され、圧力エネルギーが運動エネルギーに変換されます。

 水の出口速度を決定した後、流量、つまり時間とともに排出される水の量が計算されます。計算では連続方程式を使用し、システムを流れる水が一定に保たれるようにします。流量は、水の速度とノズルの断面積の積です。

<img alt="Equation 2" src="/files/ftp_upload/18047/18047_Equation_2.svg" style="text-align: center; height: 40px;">

 ノズルの直径が小さいため、水は高速で排出され、消火に必要な一定で強力な水流を提供します。これらの原理を適用することで、消火器の性能を最適化し、効果的な動作を確保できます。

消火器は、加圧水を使用してノズルから強力な流れを発生させます。
内部の水は、...

design-example-flow-through-a-fire-extinguisher

Education

JoVE Core

Civil Engineering

土木工学

Unit 1

ユニット1

Fluid Kinematics

流体運動学

KEY TERMS AND CONCEPTS

主要用語と概念

fire extinguisher nozzle flow and pressure

A pressurized water fire extinguisher uses fluid dynamics to create a fast stream of water. The water is stored at a much higher pressure inside the extinguisher than the surrounding air. When the extinguisher is activated, that pressure difference forces water to flow out quickly.

Bernoulli's equation helps predict the exit speed of the water. This equation links pressure and velocity. As pressure drops, velocity increases. In the extinguisher, the high internal pressure is converted into the water's speed as it leaves the nozzle.

The nozzle also plays an important role because its diameter becomes smaller near the exit. A smaller opening increases the flow speed even more. This turns pressure energy into kinetic energy, which is the energy of motion.

After the exit velocity is found, the flow rate can be calculated. Flow rate is the volume of water expelled each second. The continuity equation is used to keep track of how much water moves through the system, and the flow rate equals the water speed times the nozzle's cross-sectional area. Because the nozzle is small, the water comes out at high velocity and forms a strong, steady stream for fire suppression.

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design example: flow through a fire extinguisher

A pressurized water fire extinguisher uses fluid dynamics to create a fast stream of water. The water is stored at a much higher pressure inside the extinguisher than the surrounding air. When the extinguisher is activated, that pressure difference forces water to flow out quickly. Bernoulli's equation helps predict the exit speed of the water. This equation links pressure and velocity. As pressure drops, velocity increases. In the extinguisher, the high internal pressure is converted into the...

key terms and concepts

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Fire Extinguisher Nozzle Flow and Pressure

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