Compressed gas and heat transfer

In summary, compressing a cylinder of air would increase its temperature and pressure, but the heat generated through compression would be lost to the surroundings. The air would not return to atmospheric pressure once released and would reabsorb some of the heat energy, but not fully recover from the initial compression.
  • #1
ProtoBob
6
0
compressed gas...and heat transfer...

If you were to take a cylinder of air, at room temp, and let's say it is 100ml in volume.
If you were to take this cylinder of air, compress its volume to half its size, how much heat
would that create (btu's) and if the heat were to dissipate, would the air inside the cylinder then be back at atmospheric pressure?

If not back at atmospheric pressure, and (assuming there is still some pressure) the air were
then released, would it reabsorb the energy that was dissipated after it was compressed? i.e. would it then cool the surrounding room back to the original temperature?

Thanks!
 
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  • #2


ProtoBob said:
If you were to take a cylinder of air, at room temp, and let's say it is 100ml in volume.
If you were to take this cylinder of air, compress its volume to half its size, how much heat
would that create (btu's) and if the heat were to dissipate, would the air inside the cylinder then be back at atmospheric pressure?

If not back at atmospheric pressure, and (assuming there is still some pressure) the air were
then released, would it reabsorb the energy that was dissipated after it was compressed? i.e. would it then cool the surrounding room back to the original temperature?

Thanks!

Heat is not created (heat is a transfer mechanism for energy across a boundary), although there would be an increase in the temperature of the gas due to the compression along with the pressure increase. If the cylinder is non-adiabatic then energy would be lost due to heat transfer to the surroundings. This would result in a slight pressure loss but not back to atmospheric pressure.

Irreversibilities are never recoverd from a system once incurred. The air would be heated once released from the cylinder so it would "re-absorb" some of the heat energy.

CS
 
  • #3


I can provide a response to the question regarding compressed gas and heat transfer. When a gas is compressed, its volume decreases while its pressure and temperature increase. This is due to the gas molecules being forced closer together, resulting in an increase in collisions and therefore an increase in temperature. The amount of heat generated during compression can be calculated using the ideal gas law, which relates pressure, volume, and temperature.

In this specific scenario, if the volume of the air is compressed to half its size, the temperature will increase accordingly. The exact amount of heat generated will depend on the initial conditions and the gas used. For example, if the initial temperature of the air is 25°C and the pressure is 1 atm, compressing it to half its volume would result in a temperature of approximately 50°C. This increase in temperature would correspond to a certain amount of heat, which can be calculated using the ideal gas law.

Now, regarding the dissipation of heat, it is important to note that heat always flows from a higher temperature to a lower temperature. So, if the compressed air is allowed to dissipate its heat to the surrounding environment, it will cool down back to the original temperature. However, the exact amount of heat dissipated will depend on various factors such as the surrounding temperature and the rate of heat transfer.

As for the pressure, when the compressed air is released, it will not return to atmospheric pressure immediately. The pressure will decrease gradually as the gas expands to its original volume. This is known as adiabatic expansion and it is a process where no heat is exchanged with the surroundings. Therefore, the air inside the cylinder will not reabsorb the energy that was dissipated after compression. Instead, it will cool down due to adiabatic cooling as it expands back to its original volume.

In conclusion, compressed gas and heat transfer are closely related. Compressing a gas will result in an increase in temperature and therefore an increase in heat. If this compressed gas is allowed to dissipate its heat to the surroundings, it will cool down back to the original temperature. However, the pressure will not return to atmospheric pressure immediately and the gas will experience adiabatic cooling during expansion.
 

1. What is compressed gas?

Compressed gas is a form of gas that has been pressurized and stored in a container or cylinder. This increases the density and energy of the gas, allowing it to be used for various applications such as heating, cooling, and powering machinery.

2. How does compressed gas transfer heat?

Compressed gas transfers heat through a process called convection. When compressed gas is released from a container, it expands rapidly, causing the molecules to move faster and collide with each other. This movement produces heat, which can be used for heating or cooling purposes.

3. What factors affect the heat transfer of compressed gas?

The heat transfer of compressed gas is affected by several factors, including the volume and pressure of the gas, the surface area of the container, and the surrounding temperature. Higher pressure and larger surface area can result in more efficient heat transfer.

4. What are the safety considerations when working with compressed gas?

Working with compressed gas can be dangerous if proper safety precautions are not taken. It is important to follow storage and handling guidelines, wear protective gear, and be aware of potential hazards such as leaks or explosions. It is also crucial to have proper ventilation in the area where compressed gas is being used.

5. How is compressed gas used in different industries?

Compressed gas has a wide range of applications in various industries. It is commonly used in manufacturing for powering tools and machinery, in refrigeration and air conditioning systems, and in medical settings for anesthesia and respiratory therapy. It is also used in the food industry for packaging and preserving food products.

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