How much mass is released to decrease the pressure

In summary, the problem involves determining the amount of vapor mass released when lowering the pressure from 1 MPa to 0.9 MPa in a pressure vessel containing saturated water and vapor. The proposed solution involves finding the water height and assuming it remains constant while calculating the new density of water and vapor to determine the difference in mass. However, the assumption of constant water height is incorrect and alternative methods should be considered, taking into account the presence of air in the head space and the temperature conditions of the system.
  • #1
wasmaro
2
0
Homework Statement
I have a pressure vessel with saturated water and vapor at 1 MPa. I'd like to determine how much vapor mass is released if I lower the pressure to .9 MPa.

Any ideas how I can do that?
Relevant Equations
First law of Thermodynamics
My best estimate was to find the water height and assume it remains constant when venting the air. I know the initial weights of vapor and liquid ( I know the total mass of substance inside the vessel), so I find the new density of water and vapor and calculate the "new" mass and take the difference from the initial mass. However, that's obviously wrong since the water height should not be constant.
Any suggestions?
 
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  • #3
wasmaro said:
Problem Statement: I have a pressure vessel with saturated water and vapor at 1 MPa. I'd like to determine how much vapor mass is released if I lower the pressure to .9 MPa.

Any ideas how I can do that?
Relevant Equations: First law of Thermodynamics

My best estimate was to find the water height and assume it remains constant when venting the air. I know the initial weights of vapor and liquid ( I know the total mass of substance inside the vessel), so I find the new density of water and vapor and calculate the "new" mass and take the difference from the initial mass. However, that's obviously wrong since the water height should not be constant.
Any suggestions?
Are you saying that there is air in the head space? Is the temperature remaining constant, or is the system insulated? or something else?
 

FAQ: How much mass is released to decrease the pressure

How does the release of mass affect pressure?

The release of mass can decrease pressure because it reduces the number of molecules in a given volume, resulting in fewer collisions and therefore lower pressure.

Is there a specific amount of mass that needs to be released to decrease pressure?

The amount of mass that needs to be released to decrease pressure depends on the initial pressure and volume of the system, as well as the properties of the released mass.

Can releasing mass increase pressure?

In some cases, releasing mass can actually increase pressure. This can occur if the released mass has a higher density than the surrounding gas, causing it to sink and compress the gas below.

How does the temperature of the released mass affect pressure?

The temperature of the released mass can have a significant impact on pressure. If the mass is released at a higher temperature, it will add more energy to the system and increase pressure.

What is the relationship between mass release and pressure in a closed system?

In a closed system, the release of mass will typically result in a decrease in pressure. This is because the total number of molecules in the system remains the same, but the volume increases, leading to a decrease in pressure.

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