heat and pressure.

[dannobee]

I want to know how you would heat up a scuba tank immersed in water!

Boil the water.

 

[SparticleBrane]

I had a thought yesterday. I just happen to think about something odd ball but I wonder if it can also apply in the scuba world. In the automotive world people run nitrous which comes in a tank. People put heat pads on them to build up more pressure.

When your getting your tank filled I see they put them in cold water to lower pressure. HERES MY THOUGHT: If a person is diving deep and starts using are up at a faster rate. Couldn't someone put a heat pad on there tank to bring the pressure up some. I'm not talking putting alot of heat but enough to bring the pressure up. Is there something I'm missing that makes my thought a complete miss?

Awhile back, someone posted in in the basic scuba section about their amazing discovery -- leaving their tanks in the sun gave them another 200psi before getting in the water.

What they somehow didn't connect is that the simple act of heating up the cylinder does not give you more gas, which seems to be your idea here.


So, I'm not really seeing what you are asking. Does heating up a cylinder give you more gas? No -- it just means the pressure goes up due to the heat. Just because the pressure of a gas goes up does not mean that you have more gas in the cylinder.

 

[fppf]

You don't have more gas, but its not as dense so you can get more of it out of the tank.

 

[Luis H]

Awhile back, someone posted in in the basic scuba section about their amazing discovery -- leaving their tanks in the sun gave them another 200psi before getting in the water.

What they somehow didn't connect is that the simple act of heating up the cylinder does not give you more gas, which seems to be your idea here.


So, I'm not really seeing what you are asking. Does heating up a cylinder give you more gas? No -- it just means the pressure goes up due to the heat. Just because the pressure of a gas goes up does not mean that you have more gas in the cylinder.

When you breath, you need the volume not the actual mass. If the air is a bit warmer it will fill your lung volume with a bit less mass needed (per breath). In reality the difference would be minimal and the water temperature will dictate the tank / gas temperature.

 

[Luis H]

For ideal gas law to work, the temperature unit is in Kelvin. Celcious and Kelvin are offset by 273 degree. But the unit of K is the same as unit of C. 0C = 273K, 10C=283K, ie #K = #C+273. In F, things get a bit more complicated, convert F to C: #C=(#F-32)/1.8. So from F to K: #K = (#F-32)/1.8 + 273. Not just simplely add 460.

The same calculations can be done with metric or imperial units.

In the metric system the absolute temperature scale is the Kelvin which as you mention, zero Kelvin is equal to -237 degrees Celsius.

In the imperial system the absolute temperature scale is the Rankin scale. Zero Rankin is -460 degrees Fahrenheit.

In the US most engineers still use imperial units for many calculations, while most scientist and some engineering have converted to the metric system.