Overfill Differences for LDS - Question

[Tigerman]

That is not actually true. The first law of thermodynamics is heat can not be created or destroyed. There is not heat generated when transferring gas from one container to another other than the heat picked up from the piping and valves between the source and the destination container. Ever notice as you tranfer from a bank it gets cooler? There is more heat from compressed air because usually ambient air has more heat energy than compressed air that has been allowed to cool off for a period of time.

If heat can not be created or destroyed, why does a owen produce heat?
ENERGY can not be created or destroyed, only change forms. HEAT energy however is most certainly created from other forms of energy. Last time I checked a log of wood lying in my -5 celcius shed wasnt very hot, but it certainly is when I use it as firewood..

 

[wedivebc]

If heat can not be created or destroyed, why does a owen produce heat?
ENERGY can not be created or destroyed, only change forms. HEAT energy however is most certainly created from other forms of energy. Last time I checked a log of wood lying in my -5 celcius shed wasnt very hot, but it certainly is when I use it as firewood..

heat energy cannot be created out of nothing; ie. moving air from one container to another does not add energy to the system.
http://www.taftan.com/thermodynamics/FIRST.HTM

 

[Tigerman]

heat energy cannot be created out of nothing; ie. moving air from one container to another does not add energy to the system.
http://www.taftan.com/thermodynamics/FIRST.HTM

No, heat can not be created from nothing. However compressed air is potential energy (thats simplified).
Also moving air is moving energy, which of, in the case of filling scuba tanks, some change form and becomes heat.
Windmills work from the principle of transforming wind (kintetic energy) into electricity..

 

[PaulChristenson]

What everyone is refering to is GUY-LUSSAC'S LAW...

The pressure of a gas at constant volume is directly proportional to the absolute temperature.

Check out A Gas Laws Primer by Larry “Harris” Taylor, Ph.D

http://home.earthlink.net/~divegeek/primer.htm

 

[oly5050user]

heat energy cannot be created out of nothing; ie. moving air from one container to another does not add energy to the system.
http://www.taftan.com/thermodynamics/FIRST.HTM

moving air from one container to another can cause friction-which created heat-which is a form of energy..

 

[MikeFerrara]

moving air from one container to another can cause friction-which created heat-which is a form of energy..

Friction is not the main reason that things heat up when you compress gas into a container. What's going on is an adiabatic heating process.
The heat is a function of volume and pressure changes (short version, look it up for the long version).

When you open a tank valve fully and see the valve ice up, that's just the oposite...adiabatic cooling. Certainly there is friction involved here too but the result is still a cooling effect rather than heat.

 

[MikeFerrara]

What everyone is refering to is GUY-LUSSAC'S LAW...

The pressure of a gas at constant volume is directly proportional to the absolute temperature.

Check out A Gas Laws Primer by Larry “Harris” Taylor, Ph.D

http://home.earthlink.net/~divegeek/primer.htm

GUY-LUSSACS law and Charles law describe the relationship between pressure, volume and temperature. Combine them with Boyles law and we get P1V1/T1 = P2V2/T2 However, the adiabatic heating/cooling I refered to in my last post explaines the temporary change in temperature we see when we compress or expand a gas.

 

[MikeFerrara]

That is not actually true. The first law of thermodynamics is heat can not be created or destroyed. There is not heat generated when transferring gas from one container to another other than the heat picked up from the piping and valves between the source and the destination container. Ever notice as you tranfer from a bank it gets cooler? There is more heat from compressed air because usually ambient air has more heat energy than compressed air that has been allowed to cool off for a period of time.

No. The adiabatic heating/cooling caused by compressing or expanding gasses is completely compliant with the laws of thermodynamics and is why the target tank heats and the bank cools.

 

[wedivebc]

No. The adiabatic heating/cooling caused by compressing or expanding gasses is completely compliant with the laws of thermodynamics and is why the target tank heats and the bank cools.

Right of course. If the supply cylinder is getting cooler then the receiving cylinder is getting warmer. My point is no heat (energy) is being added to the sytem, just a change in temperature due the the movement of heat energy, whereas a compressor adds heat to the system due to compression (Guy-Lussacs Law mentioned above)
It is my belief that less temperature increase occurs when transfilling than when compressing since no heat energy is added to the system when topping up from banks.

 

[captain]

Right of course. If the supply cylinder is getting cooler then the receiving cylinder is getting warmer. My point is no heat (energy) is being added to the sytem, just a change in temperature due the the movement of heat energy, whereas a compressor adds heat to the system due to compression (Guy-Lussacs Law mentioned above)
It is my belief that less temperature increase occurs when transfilling than when compressing since no heat energy is added to the system when topping up from banks.

If the compressor cooling system is good enough to reduce the compressor outlet temperature to equal to the ambient inlet air temperature than the compressor has no effect on the increase in temperature in the cylinder being filled. It is the same as filling from a bank.