Creating a temperature differential on SF6 to evacuate a cylinder

In summary, the speaker is trying to transfer SF6 from one cylinder to another using temperature differential. They are attempting to calculate the flow rate using the ideal gas law, but realize that valves must be closed for this calculation to be accurate. They are seeking help or direction in finding the correct method for calculating the flow rate.
  • #1
co0ldood
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I have a 50KG cylinder with 1-2LB of SF6 at 15PSI. I want to transfer it into another cylinder by temperature differential.

Keeping it simple. I try to model it with two cylinders that has a valve on each cylinder. Connecting the cylinder with a 1/4" hose. Both valves are closed. The cylinder with the SF6 is at ambient temperature (25C). I cool the other cylinder to -40C (~-50C is solidifying point).. Open both valves.

How would I go about calculating the flow rate?

I try to find the pressure differential using ideal gas law

PV=nRT; P1/T1 = P2/T2, 15 PSI / 298.15K = P2/233.15K; P2 = 11.73PSI.

This is the wrong way since I know it is a compressible gas and the pressure should be much lower. Any help or direction would greatly be appreciated.

Thanks!
 
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  • #2
Weird unit system :(.

PV=nRT takes compression into account, but you won't get a pressure difference if your valves are open. You just get a density difference, while the total amount of SF6 is constant (and known).

Your calculation would require the same amount of SF6 in both cylinders and closed valves.
 

1. How do you create a temperature differential on SF6?

To create a temperature differential on SF6, you can use a heat source such as a heater or hot plate to warm up one side of the cylinder while the other side remains at room temperature. This will create a temperature difference between the two sides, causing the gas to expand on the warmer side and contract on the cooler side.

2. Why is it important to create a temperature differential on SF6?

Creating a temperature differential on SF6 is important because it allows for the efficient evacuation of the gas from the cylinder. The expansion of the gas on the warmer side will create a pressure difference, pushing the gas towards the cooler side where it can be evacuated more easily.

3. What is the purpose of evacuating a cylinder of SF6?

The purpose of evacuating a cylinder of SF6 is to remove any residual gas or impurities that may be present. This ensures that the gas inside the cylinder is pure and free of contaminants, making it suitable for use in various applications such as electrical insulation or as a dielectric medium.

4. How long does it take to create a temperature differential and evacuate a cylinder of SF6?

The time it takes to create a temperature differential and evacuate a cylinder of SF6 can vary depending on the size of the cylinder and the temperature difference being created. In general, it can take anywhere from a few minutes to several hours to complete the process.

5. Are there any safety precautions to take when creating a temperature differential on SF6?

Yes, there are several safety precautions that should be taken when creating a temperature differential on SF6. It is important to handle the gas and equipment carefully to avoid any accidents or leaks. It is also recommended to wear protective gear, such as gloves and goggles, when handling SF6 as it can be harmful if it comes into contact with skin or eyes.

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