Objective :


Static Expansion System (SES)
  1. To get familiarise with the pressure measurement system with the static expansion of the gas.
  2. To understand the principle of ideal gas equation.
  1. To get familiarise with the pressure measurement system with the static expansion of the gas.
  2. To understand the principle of ideal gas equation.

Theory :


From ideal gas equation, we have;
PV=nRT
For the same gas used, we can get;
P2 = P1* (T2/ T1) * (V1 / V1 + V2)

The above equation will be used to convert the inputted values to the output parameters.
Where;

P1 = pressure in a small chamber of volume V1

P2 = final pressure in chamber V1 and V2

T1 = temperature in the chamber 1

T2 = temperature in the chamber 2

From ideal gas equation, we have;
PV=nRT
For the same gas used, we can get;
P1V1 / T1 = P2V2 / T 2

The above equation will be used to convert the inputted values to the output parameters.

Procedure :

Table 1 : Observation table for the simulation:
S.No P1
(KPa) 		T1
(K) 		T2
(K) 		V1
(Litre) 		V2
(Litre) 		Simulated Pressure P2
(KPa)

There will be two kind of experiment on this Static Expansion System.
    Natural Pressure Generation: Following steps will be followed;
  1. First, gas will be in all the chambers and pressure line (3 valves in open state). At start of the experiment it will be shown with red colour
  2. Close NV1 while NV2 and NV3 are still in open state.
  3. Vacuum Pump will be switched on. This will create vacuum while removing the gas in the pressure chambers and pressure line upto NV1. It will create vacuum of the order of 10-7 torr
  4. Pressure P1 is the pressure of Volume, V1
  5. Input the values of pressure P1, T1 and T2
  6. Now close the valve NV2 and NV3. Then open the valve NV1 to get the gas pressure P1 from the pressure source
  7. After obtaining the pressure P1 in the chamber V1, NV2 will be opened. This will expand the gas available in V1 to the volume V2
  8. The pressure in the volume V2 will be P2
  9. This P2 is the required output
  10. After obtaining the P2 , NV3 can be opened so that the gas will be in all the pressure line as it was at the start of the experiment
  11. From step I to X will be repeated again for variations of P1. Plot will be for P2 vs P1
    Successive Pressure Generation: It has following steps;
  1. From step I to IX of the earlier method will be repeated
  2. Close the NV2. Set the pressure at double pressure of original P1 in the chamber V1
  3. Open the valve NV2 and let the gas again expand in the volume V2
  4. Again close the vale NV2 and set the pressure of V1 at 3 times of original P1.
  5. Again open the valve NV2 and let the gas expand into V2
  6. This way, step II and III can be repeated multiple times to get a higher pressure.
  7. After completing the experiment, NV3 can be opened. Then vacuum can be again created in the chamber and experiment can be repeated again
(Notes:For Natural pressure generation, graph will be P2 Vs P1 for repeated experiment while temperatures are different. For Successive pressure generation, graph will be P2 of each cycle vs cycles number used to get the final required pressure.)

There will be two kind of experiment on this Static Expansion System.
    Natural Pressure Generation: Following steps will be followed;
  1. First, gas will be in all the chambers and pressure line (3 valves in open state). At start of the experiment it will be shown with red colour
  2. Close NV1 while NV2 and NV3 are still in open state.
  3. Vacuum Pump will be switched on. This will create vacuum while removing the gas in the pressure chambers and pressure line upto NV1. It will create vacuum of the order of 10-7 torr
  4. Pressure P1 is the pressure of Volume, V1
  5. Input the values of pressure P1, T1 and T2
  6. Now close the valve NV2 and NV3. Then open the valve NV1 to get the gas pressure P1 from the pressure source
  7. After obtaining the pressure P1 in the chamber V1, NV2 will be opened. This will expand the gas available in V1 to the volume V2
  8. The pressure in the volume V2 will be P2
  9. This P2 is the required output
  10. After obtaining the P2 , NV3 can be opened so that the gas will be in all the pressure line as it was at the start of the experiment
  11. From step I to X will be repeated again for variations of P1. Plot will be for P2 vs P1
    Successive Pressure Generation: It has following steps;
  1. From step I to IX of the earlier method will be repeated
  2. Close the NV2. Set the pressure at double of original P1 in the chamber V1
  3. Open the valve NV2 and let the gas again expand in the volume V2
  4. Again close the vale NV2 and set the pressure of V1 at 3 times of original P1.
  5. Again open the valve NV2 and let the gas expand into V2
  6. This way, step II and III can be repeated multiple times to get a higher pressure.
  7. After completing the experiment, NV3 can be opened. Then vacuum can be again created in the chamber and experiment can be repeated again
(Notes:For Natural pressure generation, graph will be P2 Vs P1 for repeated experiment while temperatures are different. For Successive pressure generation, graph will be P2 of each cycle vs cycles number used to get the final required pressure.)
  1. Using dropdown, Close NV1 -> keep NV2 & NV3 Open
  2. Press Vacuum Pump ON
  3. Input the values of P1, T1 and T2
  4. Close NV2 & NV3 -> Open NV1 -> Open NV2
  5. Calculate the simulated pressure P2
  6. Open NV3
  7. Repeat steps 1 to 6 for different values of P1-> Plot P2 vs P1 graph

Natural Pressure Generation

Pressure (KPa)
T1
T2



NV1



NV2



NV3

Pressure Source
Volume, V1 (0.025 L)
Volume, V2 (100 L)

Quiz :


  1. A nitrogen gas is expanded from a chamber of small volume of 25cm3 to 100 litres of volume chamber and the initial pressure of the gas was 100KPa. What will be the final pressure (KPa) in the small volume chamber?
    1. 0.025000
    2. 0.2499375
    3. 0.024937
    4. None
  2. A nitrogen gas is expanded from a chamber of small volume of 25cm3 to 100 litres of volume chamber and the initial pressure (KPa) of the gas was 100KPa. What will be the final pressure in the large volume chamber?
    1. 0.025000
    2. 0.2499375
    3. 0.024937
    4. None
  3. Vacuum pump is needed for;
    1. To create pressure
    2. To remove the gas
    3. To compress the gas
    4. None
  4. If Oxygen and Nitrogen is expanded under same conditions with the same volume chambers with same initial pressure, which will producer lower pressure?
    1. Oxygen
    2. Nitrogen
    3. can’t be decided
    4. same pressure
  5. In order to obtain pressure by using static expansion system, the pressure will be dependent on
    1. Volume ratio of the chambers
    2. Initial pressure
    3. Temperature ratio of the chambers
    4. All of the above

Reference :


Mohan, P., Kumar, H. Static expansion primary vacuum standard — Part 1: Determination of the volume ratio of the expansion stage. MAPAN 24, 101 (2009).

 https://doi.org/10.1007/s12647-009-0013-y

Mohan, P., Kumar, H. Static expansion primary vacuum standard — Part 2: Characterization of two spinning rotor gauges. MAPAN 24, 111 (2009).

 https://doi.org/10.1007/s12647-009-0014-x

Video : Static Expansion System