Name: vapor pressure and boiling behavior
Uploaded: 2025-02-13T15:43:08.000Z
Duration: 1 min 28 s
Channel: JoVE

끓는 점등과 캐비테이션에 영향을 미치는 증기압은 주어진 온도에서 액체와 평형 상태에 있는 증기가 가하는 압력이며 분자가 액체 표면에서 탈출하는 경향을 나타냅니다.
밀폐되고 배출된 용기에서 액체 분자는 우주로 탈출하여 평형에 도달할 때까지 압력을 높이고, 여기서 탈출하는 분자의 속도는 복귀 속도와 같습니다. 이 평형 압력이 증기압입니다.
증기압은 온도에 따라 다릅니다. 온도가 상승함에 따라 분자는 운동 에너지를 얻어 분자간 힘을 극복하고 증기상으로 더 쉽게 탈출하여 증기압을 증가시킵니다.
예를 들어, 100°C의 물은 증기압이 101.3kPa인데, 이는 해수면의 대기압과 일치하여 끓는 원인이 됩니다. 더 낮은 대기압과 함께 더 높은 고도에서는 증기압이 감소된 대기압과 더 빨리 일치하기 때문에 물은 더 낮은 온도에서 끓습니다.
증기압 모니터링은 캐비테이션을 방지하기 위해 펌프와 터빈을 설계하고 작동하는 데 매우 중요합니다.
캐비테이션은 국부 유체 압력이 증기 압력 이하로 떨어지면 격렬하게 붕괴되어 장비가 손상되는 증기 기포를 형성할 때 발생합니다.

유체의 증기압

유체의 증기압은 유체 역학에서 중요한 개념으로, 비등 및 캐비테이션과 같은 현상에 영향을 미칩니다. 증기압은 특정 온도에서 해당 액체상과 열역학적 평형 상태에서 증기가 가하는 압력을 말합니다. 분자가 유체 표면에서 증기상으로 빠져나가는 경향을 나타냅니다.

액체를 작은 공기 공간이 있는 밀폐된 용기에 넣고 공간을 비우면 증기 분자가 액체에서 공간으로 빠져나갑니다. 더 많은 분자가 빠져나갈수록 공간의 압력이 평형에 도달할 때까지 증가합니다. 여기서 액체에서 빠져나가는 분자의 속도는 액체로 돌아오는 분자의 속도와 같습니다. 이 평형 압력이 액체의 증기압입니다.

증기압은 온도에 따라 달라집니다. 온도가 상승함에 따라 분자의 운동 에너지가 증가하여 더 많은 분자가 분자 간 힘을 극복하고 증기상으로 빠져나갑니다. 따라서 증기압은 온도에 따라 증가합니다. 예를 들어, 100°C의 물은 증기압이 101.3kPa(1atm)이므로 표준 대기압에서 끓을 수 있습니다. 그러나 대기압이 더 낮은 더 높은 고도에서는 증기압이 더 높은 고도의 감소된 대기압과 같기 때문에 물이 더 낮은 온도에서 끓습니다.

끓는 점등과 캐비테이션에 영향을 미치는 증기압은 주어진 온도와 ...

Education

교육

JoVE Core

Civil Engineering

토목공학

Unit 1

제1단원

Fluid Properties

유체 특성

KEY TERMS AND CONCEPTS

주요 용어 및 개념

Vapor Pressure of Fluid

vapor pressure and boiling behavior

Vapor pressure and boiling behavior are closely linked in fluids. Vapor pressure is the pressure a vapor exerts when it is in thermodynamic equilibrium with its liquid at a given temperature. It shows how strongly molecules tend to leave the liquid surface and move into the vapor phase.

A closed container helps show how vapor pressure forms. If a liquid sits in a sealed space with a small air gap, and that space is evacuated, vapor molecules escape from the liquid into the empty space. The pressure rises as more molecules collect there. Soon, the rate of molecules leaving the liquid equals the rate returning to it. That balance creates the vapor pressure of the liquid.

Temperature changes vapor pressure. When temperature increases, the molecules gain kinetic energy. More molecules can overcome intermolecular forces and escape into the vapor phase. For that reason, vapor pressure increases as temperature increases.

Water gives a clear example. At 100°C, water has a vapor pressure of 101.3 kPa, or 1 atm. That is why it can boil at standard atmospheric pressure. At higher elevations, atmospheric pressure is lower. Water then boils at a lower temperature because its vapor pressure reaches the reduced outside pressure sooner.

Vapor Pressure and Boiling Behavior

characteristics of fluids

Fluid Behavior in Liquids and Gases

Fluids include liquids and gases, and they behave differently from solids because of how their molecules are arranged. In solids, molecules are tightly packed and held by strong intermolecular forces. That structure helps solids keep their shape and resist deformation. Fluids have molecules that are farther apart and held by weaker forces. Because of this, they can flow and change shape easily. A fluid is any substance that deforms continuously when shearing stress is applied. Shearing stress...

density, specific weight, specific gravity and compressibility of fluid

density-specific-weight-specific-gravity-and-compressibility-of-fluid

Fluid Properties: Density, Weight and Compression

Density, specific weight, specific gravity, and compressibility are key fluid properties. Density is the mass per unit volume of a fluid. It helps describe how much mass a fluid system contains and affects buoyancy, pressure, flow behavior, viscosity, thermal conductivity, and sound propagation. In pipeline design, knowing density helps engineers make sure the pipe can support the fluid’s mass. Specific weight is the weight per unit volume. It is found by multiplying density by gravitational...

viscosity of fluid

How Temperature Changes Fluid Viscosity

Viscosity describes how much a fluid resists flow and deformation. It comes from internal friction between fluid layers that move past each other. Dynamic viscosity, shown by the Greek letter mu (μ), measures the force needed to move one layer over another. Newtonian fluids, such as water and air, have a linear relationship between shearing stress and the rate of shearing strain. Their viscosity stays constant, even when the applied stress changes. Non-Newtonian fluids, like ketchup,...

types of fluids

Newtonian vs Non-Newtonian Fluid Behavior

Fluids can be grouped by how they respond to shear stress. Shear stress is a force that acts across a material, and shear strain rate describes how quickly it changes shape or flows. In this lesson, fluids are divided into Newtonian and non-Newtonian types. Newtonian fluids follow Newton’s law of viscosity. Their shear stress changes in a linear way as the shear rate changes. That means their viscosity stays constant, so their flow is predictable and easier to analyze. Water, air, oil, and...

newtonian fluid: problem solving

Newtonian Fluid Viscosity and Shear Stress

Newtonian fluids have a constant viscosity, so their shear stress and shear strain rate stay directly proportional. This creates a linear, predictable link between force and flow. Water, air, and light oils are common examples of Newtonian fluids. A simple way to study this behavior is to place the fluid between two parallel plates. One plate stays still, and the other moves at a constant velocity. The fluid forms a velocity gradient, which is the change in speed across the distance between...

vapor pressure of fluid

Vapor pressure and boiling behavior are closely linked in fluids. Vapor pressure is the pressure a vapor exerts when it is in thermodynamic equilibrium with its liquid at a given temperature. It shows how strongly molecules tend to leave the liquid surface and move into the vapor phase. A closed container helps show how vapor pressure forms. If a liquid sits in a sealed space with a small air gap, and that space is evacuated, vapor molecules escape from the liquid into the empty space. The...

surface tension of fluid

Why Water Drops and Needles Float

Surface tension helps explain why water forms drops, supports small objects, and moves in thin tubes. It is a property of fluids at the boundary between a liquid and a gas, or between two immiscible liquids. At the surface, molecules are pulled inward by neighboring molecules. That inward pull makes the surface act a little like a stretched elastic membrane. Inside a fluid, molecules are attracted in all directions. Surface molecules do not have the same balance of forces. They feel a net...

capillarity in fluid

Capillary Action in Narrow Spaces

Capillary action is the movement of liquid through narrow spaces without any outside force. It depends on surface tension and adhesion between the liquid and nearby solid surfaces. This effect is common in narrow tubes, porous materials, and fine particles. Surface tension comes from cohesive forces between liquid molecules at the liquid-air boundary. These forces create a thin skin that resists outside pressure. When a capillary tube is placed in a liquid, the liquid level changes because of...

design example: deciding thickness of lubricating fluid in a shaft

design-example-deciding-thickness-of-lubricating-fluid-in-a-shaft

Lubricant Film Thickness for Shaft Bearings

Lubricant film thickness for shaft bearings is calculated to keep a rotating shaft from touching its bearing housing. A controlled layer of lubricant reduces friction, wear, and energy loss. It also helps the machine run smoothly by preventing metal-to-metal contact. The calculation starts with the shaft’s tangential velocity. First, the rotational speed is converted to angular velocity. Then that value is multiplied by the shaft radius. The result is the shaft’s linear speed at its surface...

key terms and concepts

Learn how vapor pressure forms, why it rises with temperature, and how it explains boiling in water at sea level and higher elevations.

Vapor Pressure and Boiling Behavior | JoVE K12

JoVE Core Civil Engineering offers a foundational exploration of essential construction materials such as bricks, stones, steel, wood, and concrete, along with fluid mechanics topics like flow over immersed bodies, open channel flow, and dimensional modeling. It also covers key surveying concepts, including leveling, traverse adjustments, curve design, topographic mapping, and geospatial technologies (GPS & GIS). Science-in-action videos showcase laboratory research on materials, fluids, and surveying practices in real-world engineering systems.

civil engineering

Vapor Pressure and Boiling Behavior

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