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

Un extincteur utilise de l’eau sous pression pour générer un jet puissant à travers une buse.
L’eau à l’intérieur est stockée à une pression beaucoup plus élevée que l’atmosphère environnante, forçant l’eau à s’écouler lorsque l’extincteur est activé.
Des équations de dynamique des fluides sont appliquées pour déterminer la vitesse à laquelle l’eau sort de la buse et la quantité expulsée au fil du temps.
La première étape consiste à comprendre la différence de pression entre l’intérieur de l’extincteur et la pression à l’extérieur de la buse.
Cette différence de pression entraîne le mouvement de l'eau. En appliquant l'équation de Bernoulli, qui relie la pression et la vitesse, la vitesse de l'eau à la sortie de la buse est calculée.
Le diamètre plus petit de la buse fait accélérer l’eau lorsqu’elle s’en va, transformant la pression en vitesse.
Après avoir calculé la vitesse de sortie, le débit est déterminé. Le débit est calculé à l’aide de l’équation de continuité, qui garantit que la quantité d’eau qui s’écoule à travers la buse est constante.
Le débit est calculé en multipliant la vitesse de l'eau par la section transversale de la buse.

exemple de conception: écoulement à travers un extincteur

Design Example: Flow Through a Fire Extinguisher

Un extincteur qui utilise de l’eau sous pression s’appuie sur les principes de la dynamique des fluides pour générer un flux à grande vitesse capable d’éteindre les flammes. L’eau est stockée à une pression beaucoup plus élevée à l’intérieur de l’extincteur que l’atmosphère environnante. Cette différence de pression force l’eau à s’écouler rapidement lorsque l’extincteur est activé, et le comportement de l’eau lorsqu’elle sort de la buse peut être compris à l’aide d’équations fondamentales de la dynamique des fluides.

La clé pour comprendre comment l’eau accélère réside dans la différence de pression entre l’intérieur de l’extincteur et l’environnement extérieur. L’équation de Bernoulli, qui relie la pression et la vitesse, calcule la vitesse à laquelle l’eau sortira de la buse.

<img alt="Equation 1" src="/files/ftp_upload/18047/18047_Equation_1.svg" style="text-align: center; height: 45px;">

Selon ce principe, lorsque la pression diminue, la vitesse augmente. Cela signifie que la pression interne élevée à l’intérieur de l’extincteur est convertie en vitesse de l’eau lorsqu’elle s’écoule. À mesure que l'eau s'approche de la buse, la diminution du diamètre de la buse accélère encore le débit, transformant l'énergie de pression en énergie cinétique.

Après avoir déterminé la vitesse de sortie de l'eau, le débit, ou le volume d'eau expulsé au fil du temps, est calculé. Le calcul utilise l'équation de continuité, garantissant que l'eau qui s'écoule dans le système reste constante. Le débit est le produit de la vitesse de l'eau et de la section transversale de la buse.

<img alt="Equation 2" src="/files/ftp_upload/18047/18047_Equation_2.svg" style="text-align: center; height: 40px;">

Étant donné que la buse a un petit diamètre, l'eau est expulsée à grande vitesse, fournissant un jet constant et puissant nécessaire à la suppression des incendies. En appliquant ces principes, les performances de l'extincteur peuvent être optimisées pour assurer un fonctionnement efficace.

Exemple de conception: écoulement à travers un extincteur

Un extincteur utilise de l’eau sous pression pour générer un jet puissant à travers une buse.
L’eau à l’intérieur est stockée à une pression beaucoup plus élevée que le ...

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

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Fluid Kinematics

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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

Explore how pressure, Bernoulli's equation, and nozzle size control the water speed and flow rate in a pressurized fire extinguisher.

Fire Extinguisher Nozzle Flow and Pressure | JoVE K12

JoVE Core Civil Engineering provides a foundational exploration of essential construction materials in civil engineering, focusing on bricks, stones, steel, wood, and concrete through easy-to-understand animated videos. This collection covers the properties, manufacturing processes, and practical applications of these materials. Additionally, the accompanied science-in-action videos demonstrate the research experiments performed in laboratories.

Fire Extinguisher Nozzle Flow and Pressure

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