Temperature and pressure change in an air vessel

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• AmeenBassam
In summary, the conversation is about modeling an air vessel with a constant volume and compressed air. The equations in the attached photo are being questioned for their suitability, and there is also a discussion about the charging and discharging processes occurring simultaneously. The person mentions finding the equation in a published paper and confirming it using the open system version of the first law of thermodynamics.
AmeenBassam
Hello All,

I am trying to model an air vessel with a constant volume during charging and discharging with compressed air. Are the equations in the attached photo are suitable?
where m is the air mass, Gc and Gt are the mass flow rate in and out of the air vessel with a volume V. Tac is the temperature of the Air in air storage device.

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AmeenBassam said:
Hello All,

I am trying to model an air vessel with a constant volume during charging and discharging with compressed air. Are the equations in the attached photo are suitable?
where m is the air mass, Gc and Gt are the mass flow rate in and out of the air vessel with a volume V. Tac is the temperature of the Air in air storage device.
Let's see your derivation. Also, are the charging and discharging occurring simultaneously?

Chestermiller said:
Let's see your derivation. Also, are the charging and discharging occurring simultaneously?
I found this equation in a published paper in Elsevier and I just wanted to make sure of it and thank you for your reply.

AmeenBassam said:
I found this equation in a published paper in Elsevier and I just wanted to make sure of it and thank you for your reply.
Using the open system version of the 1st law of thermodynamics, I confirmed the temperature equation, even for combined charging and discharging.

Last edited:

1. How does temperature change affect the pressure in an air vessel?

When the temperature of the air in a vessel increases, the kinetic energy of the air molecules also increases, causing them to move more rapidly and collide with the walls of the vessel with greater force. This results in an increase in pressure. Conversely, if the temperature decreases, the kinetic energy of the air molecules decreases, leading to a reduction in pressure. This relationship is described by Gay-Lussac's Law, which states that the pressure of a gas is directly proportional to its absolute temperature when volume is held constant.

2. What is the ideal gas law and how does it relate to changes in temperature and pressure in an air vessel?

The ideal gas law is a fundamental equation in thermodynamics given by PV = nRT, where P represents pressure, V represents volume, n is the number of moles of the gas, R is the universal gas constant, and T is the absolute temperature. This law shows the relationship between the pressure, volume, and temperature of an ideal gas. In a closed air vessel, if the volume remains constant, any change in temperature will directly affect the pressure, and vice versa.

3. What happens to the pressure when the volume of an air vessel is decreased while the temperature remains constant?

When the volume of an air vessel is decreased while the temperature remains constant, the pressure inside the vessel increases. This is described by Boyle's Law, which states that the pressure of a gas is inversely proportional to its volume when the temperature is held constant. As the volume decreases, the air molecules have less space to move around, leading to more frequent collisions with the vessel walls, thereby increasing the pressure.

4. How can changes in temperature and pressure in an air vessel be measured accurately?

Changes in temperature can be measured using thermometers or thermocouples, which provide precise readings of the temperature inside the vessel. Pressure changes can be measured using manometers or pressure sensors/transducers, which can detect variations in pressure with high accuracy. These instruments are essential for monitoring and controlling the conditions within the air vessel in various scientific and industrial applications.

5. What safety precautions should be taken when dealing with significant changes in temperature and pressure in an air vessel?

When dealing with significant changes in temperature and pressure in an air vessel, it is crucial to follow safety precautions to prevent accidents. These include ensuring the vessel is designed to withstand the expected pressure ranges, using pressure relief valves to prevent over-pressurization, monitoring temperature and pressure continuously, and wearing appropriate personal protective equipment (PPE). Additionally, it is important to follow proper procedures for heating or cooling the vessel to avoid rapid changes that could lead to structural failure or other hazards.

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