Expansion Cooling

Expansion cooling is demonstrated by observing fog formation inside a glass flask as the air pressure is suddenly released.
Equipment:
- Large syringe
- Pressurized air
- Rubber hose
- Special glass flask
- Matches
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This video is part of the project "Videos of Physics Demonstrations", which is created by Dr. Galli and Dr. Amiri of Physics Department, Weber State University. To access the full library of the videos, please visit this link: www.weber.edu/physics/amiri_g...
Links to University and Department:
Weber State University Homepage: www.weber.edu/
WSU Physics Department: www.weber.edu/physics

[@TheShikerWolf]

Twisting an empty plastic bottle until the lid pops off has the exact same effect! Now I know why that happened! So cool

[@ScoutSniper3124]

Expansion Cooling is the reverse process of Heat of Compression. Heat of Compression provides the ignition for Diesel Engines by compressing the Fuel/Air Mixture until its Auto-Ignites... Expansion Cooling provides for Refrigeration by expanding the Refrigerant until it is cool enough to absorb heat as it passes through coils inside the Refrigerator.

[@user-xy7bt8qg8k]

⚠️ God has said in the Quran: 🔴 { O mankind, worship your Lord, who created you and those before you, that you may become righteous - ( 2:21 )} 📖Quran

[@informationcollectionpost3257]

Thought it was a video from one of my alamada and as an ex-Mechanical Engineer with a minor in heat and fluids I have an interest in Stirling engines which if energy is applied as an input produce significant cooling. Instead you gave a simple principle and an experiment of why this works. Most students don't realize how well this principle works as an energy input into a Stirling engine to produce cooling is the basis for cyro-genic cooling systems. ( Liguid oxygen, nitrogen, & etc manufacturing) Of course the theory revolves around Boyls ( probably misspelled it ) law.

[@isvvc_]

Fascinating

[@dangillam8918]

But what if you don't move the wall back, but suddenly remove it. allowing the gas to flow into the previously empty part of the container eventually hitting stationary walls (not moving walls). The gas will still cool (molecules will move slower) but not due to hitting a receding surface?

[@DanielLaLiberte]

My thought exactly. If the gas molecules make the piston move, then they lose energy. But if the volume of gas suddenly increases and expands into a vacuum, then gas will cool, so no impact is required.

[@jon-williammurphy9780]

I am also not satisfied with the mechanistic reasoning provided. Although it seems you mean “suddenly” as in a speed of sound removal of the plunger? Or do you mean “blinking it out of existence” type removal? I agree that the thought experiment of the latter would still cool the air and refute his argument. Or better yet, an actual experiment could be to use an aperture like on a camera, or other sliding seal, such that the molecules are exposed to a second chamber that starts as a vacuum and then wouldn’t have the receding plunger to love energy on.

[@PhysicsYogi24]

you cleared my doubt

[@imrankhanimrankahn3220]

waooo..best

[@timetostudywithme]

Wowww

[@krisanderson5636]

Nice explanation, although you didn't explain that the cylinder is being allowed to expand by the gas molecules pushing out the piston.

[@NutsandGuts]

Yes it wasn't a very good explaination because he referred to the piston and managed the terms "at rest" and "moving to the right" which is kind of misleading since we're not dealing with piston speed but rather pressure balance between inside and outside of the cylinder.

[@liumai1966]

why do the cooling air can expantion at turbine stages?

[@kimbalcalkins6903]

I am trying to solve the following. A sealed vessel contains a gas at P1=23.4PSI and temperature T1=300K. If a valve is opened so that in say 20 seconds the pressure drops to 15PSI. If the valve closes quickly, what is the gas temperature in the vessel? Does the Gay Lussac's Law apply giving T2=(P2/P1)*T1=210K?

[@sneekmuch]

Where do the particles get their energy from? And why does compressing a material cause it to heat up? Expansion cooling I’m assuming cools because of greater surface area to dissipate heat? I’ll edit after watching video If I have more questions

[@maruti8636]

It's because of the internal energy of the gas which is used to break the van der Waals attraction and hence when it expands the gas molecules has lesser internal energy.... that's what cause the cooling sneek

[@hakunamatata2000]

that pointing device

[@raico6890]

Got this recommended?

[@ethanputman3471]

But why does it work molecularly. When most releases of energy produce heat?

[@SadhuBiochemist]

I disagree with the analysis of the experiment. The air molecules in the cylinder are colliding with each other and the walls of the cylinder. After each collision, there is a loss of heat. A compressed gas will gradually cool. When the volume is suddenly expanded, there are less collisions and less heat produced.

[@a-boardmanshawn7314]

There may be a loss of heat as they collide with each other and the walls of the cylinder but doesn't the cylinder also have its own heat that it can transfer to the gas molecules? Also your final analysis agrees with the purpose of the video to show how expansion cools gas

[@SadhuBiochemist]

@@a-boardmanshawn7314 The heat transferred from the cylinder to the gas is negligible. To be honest, I'll have to watch the video again. It's been 2 months.