6
votes
What makes something like water so hard to change its density?
Two factors contribute to the incompressibility of liquids. The first is the electrostatic repulsion between the electron fields of neighboring molecules keeping the molecules from getting closer to ...
- 4,031
6
votes
Accepted
How do gas flow regulators avoid choking?
The short answer is that they don't. Choking is not a bad thing. For a gas flow regulator, it's actually a good thing, because under choking conditions, the mass-flow rate is no longer dependent on ...
4
votes
Accepted
Shouldn't enthalpies be equal in isentropic process?
Constant entropy doesn't mean constant temperature, the gas flow through nozzle is subject to change in pressure and velocity (continuity equation) due to the variation in cross section, and being ...
- 2,150
3
votes
Accepted
How to determine the choke point in a compressed gas system?
How do I explain the fact that the flow chokes only at the nozzle?
To explain why the flow only chokes at a single point, it is important to remember that for a system at steady state, there can only ...
- 210
2
votes
Natural gas mass flow conversion
You can probably assume the natural gas is an ideal gas, then apply the corresponding equation of state on any arbitrary control volume of the flow:
$$
pV=mRT
$$
where $p$ is pressure, $V$ is volume,...
- 3,034
2
votes
Determining mass flow rate and exit velocity of compressible flow
You are correct that the Bernoulli equation will not work here because you're in the compressible flow regime. As you already learned, the flow through the orifice will become sonic when the pressure ...
- 3,034
2
votes
Why does exit pressure match back pressure in Converging Diverging Nozzles?
It's kind of a matter of semantics: if the fluid is still in a "jet" that's undergoing significant broadening or narrowing, and therefore significant acceleration that can match a pressure ...
- 831
2
votes
How do stators in axial compressors work?
Compressors are a combination of rotors and stators along a structure with reducing cross-section area. The rotors spin and push air down the compressor, but due to their spin there arises a ...
- 119
2
votes
Accepted
What are the Units of flow coefficient Cv? And relationship between flow coefficient Cv formulas of incompressible and compressible fluids
The compressible fluid flow coefficient formula is just the incompressible formula with different units and with the ideal gas law applied under a particular convention.
I can find references to the ...
- 369
2
votes
Methane Gas Density in Adiabatic Compressible Flow
The text book answer is correct.
I think you missed to calculate the density of the downstream of the shock.
the equation you entered is valid only in the region 1 or in region 2. means the ...
- 486
1
vote
Isentropic Flow and Conservation of Mass
As far as I understand, especially assuming steady conditions, your mass flow rate is held constant. The thing that is normally changing is the mass flow rate per unit area, or mass flux. Knowing that ...
- 11
1
vote
What are the Units of flow coefficient Cv? And relationship between flow coefficient Cv formulas of incompressible and compressible fluids
Flow coefficient is a way of expressing the relationship between flow rate and pressure drop. So we could say $Q$ is a function of $\Delta P$:
$$ Q = f(\Delta P) $$
For an incompressible fluid through ...
- 127
1
vote
What would be the flow rate of 5 L hydrogen at 20 bar being vented through a 1/4 inch (assumed smooth) stainless steel pipeline to standard pressure?
Assuming the hydrogen gas is incompressible, the perforation factor is 1, and the friction loss in the pipe is insignificant, we measure the discharge volume at the connection of the pipe to the tank.
...
- 21.6k
1
vote
Accepted
How are the conditions after the shock calculated for a shockwave formed on a cone?
To reiterate my edit and close the question:
Looking at the link suggested and a few textbooks, I found Modern Compressible Flow: with Historical Perspective by John D. Anderson explained conical flow ...
- 19
1
vote
Accepted
Why don't all gas pipe flows end up at sonic speed?
These are good questions to ask yourself.
The most succinct answer to your questions is: Mass Balance and Energy Balance.
Wall friction will actually cause a subsonic flow of gas through a
pipe ...
- 522
1
vote
Linear pneumatic actuator opening time - pressurise connection pipe
Flow rate of the gas into the cylinder will change according to the pressure drop. So first you have to model flow rate through the pipe to the cylinder, which you can probably model as a plenum. I ...
- 5,885
1
vote
What should be the density of a compressed gas while measuring the flow rate using Rotameter?
In, compressible flow, the mass flow rate remains constant throughout the flow. But volume flow rate is changed according to the local velocity and area of cross-section. So one can calculate the ...
- 486
1
vote
Determination of solid bed fluidisation
Use flow (which is a product of pressure).
If a single solid will be entrained at the flow rate then it will plug.
If the bed has a packing factor of 50% then flow velocity in the bed is twice ...
- 489
1
vote
Determination of blower mass flow from limited information
I think not really. You determine power by your choice of motor size, or if you use an FI, rpm. Motor power is propoertional to the third power of rpm (All else equal). So you really don't have value ...
- 4,687
1
vote
Why does exit pressure match back pressure in Converging Diverging Nozzles?
In order to answer the question, one more question needs to be answered. The exit pressure is present at the downstream of the shock, how does this information is transferred to upstream of the shock? ...
1
vote
Accepted
Using pressure drop to correlate mass flow
It is not entirely clear from the question, where the instrument readings take place. The following equations might need to be adapted in order to reflect the sensor positions.
The basic equation for ...
- 1,192
1
vote
Combustion Chamber Back Pressure due to gas injection
I believe that the Borda-Carnot equation is only valid for incompressible flows, while you mention that the injector orifice is choked. While the flow becomes incompressible pretty quickly after the ...
- 21
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