The discussion revolves around the behavior of gas as it passes through a porous plug, specifically focusing on the changes in pressure and temperature. Participants explore the underlying mechanisms of these changes, including concepts related to viscous flow and throttling, while considering both theoretical and practical implications.
Participants express varying levels of understanding regarding the concepts of pressure change and viscous flow. While some agree on the principles of gas behavior through porous media, there is no consensus on the specific mechanisms or implications of these changes, leading to ongoing questions and exploration.
Participants reference concepts such as viscosity, Darcy's law, and the Hagen-Poiseuille equation, indicating a reliance on these principles to explain the phenomena discussed. However, there are unresolved questions about the assumptions underlying these models and their applicability to the specific scenario of gas flow through a porous plug.
This discussion may be of interest to individuals studying fluid dynamics, thermodynamics, or related fields, particularly those looking to understand the behavior of gases in porous media and the effects of pressure and temperature changes in such contexts.
If it is an ideal gas, its exit temperature will be the same as its inlet temperature. Regarding the pressure change, the porous plug has tiny passages through which the gas flows. So there will be a viscous pressure drop between the inlet side and the outlet side of the plug. Flow through a porous medium is typically described using Darcy's law: $$\frac{dp}{dx}=-\frac{\mu}{k}v$$ where p is the pressure, x is the axial distance along the plug, v is the volume flow rate divided by the cross sectional area of the plug, k is the "permeability" of the plug (a physical property related to the microscopic geometry of the pore channels), and ##\mu## is the viscosity of the gas.Vivek98phyboy said:Consider a high pressure gas is passing through a tube of small diameter. Now, you are trying to block its passage by placing a cotton wool at the half of its way but it'll pass through the cotton wool as it is having high pressure. The gas that emerges on the other side of the cotton wool will be of low pressure and low temperature. My question is ' why is it so?'
Can you explain that viscous drop much more clear?Chestermiller said:If it is an ideal gas, its exit temperature will be the same as its inlet temperature. Regarding the pressure change, the porous plug has tiny passages through which the gas flows. So there will be a viscous pressure drop between the inlet side and the outlet side of the plug. Flow through a porous medium is typically described using Darcy's law: $$\frac{dp}{dx}=-\frac{\mu}{k}v$$ where p is the pressure, x is the axial distance along the plug, v is the volume flow rate divided by the cross sectional area of the plug, k is the "permeability" of the plug (a physical property related to the microscopic geometry of the pore channels), and ##\mu## is the viscosity of the gas.
Are you familiar with the term viscosity and the concept of viscous fluid flow? Do you know that the inlet pressure of a fluid flowing through a pipe has to be higher than the outlet pressure?Vivek98phyboy said:Can you explain that viscous drop much more clear?
Then what is it about what I said that you do not understand?Vivek98phyboy said:Yeah I have a little knowledge about that
The porous plug can be envisioned as an array of tiny pipes in parallel. The flow rate of gas through each pipe is proportional to the pressure drop across the porous plug. The sum of the flows through the pipes is equal to the total flow of gas through the plug. Have you learned about viscous flow through a pipe, and are you aware of the Hagen Poiseuille equation? If not Google it. You need to understand viscous flow in pipes before you can understand throttling through a porous plug.Vivek98phyboy said:My problem is how does the pressure of the gas changes on the other side of the porous plug? What is the state of molecules before and after passing through the porous plug? What actually causes this differences? All these doubts of mine arised from the topic of throttling