Applying a PD compressor in a pressure system, the air mass flow is “constant”.
Applying a PD compressor in a vacuum system, the air mass flow is “constant” for a specific vacuum.
In case of applying a centrifugal pump, which is not controlled at “constant” gas mass flow the air mass flow changes with the pressure drop.
Then, still the pneumatic conveying is considered as a mass conveying system at a specific pressure or vacuum.
The actual gas mass flow through the conveying pipe changes with the compressor characteristics (Internal leakage), rotary valve leakage, air mass replacing unloaded material from a tank, filter pulse air in case of vacuum conveying, etc.
Therefore, a pneumatic conveying calculation is based on the compressor gas mass flow mines the pressure dependent leakages and gas masses left behind in the system.
This makes it possible to use the Solid Loss Ratio to be used in the ruling formulas.
The gas mass flow and the material mass flow is constant over the whole pipeline.
From the constant gas mass flow, the actual gas volume at a specific location in the pipeline is calculated with the gas laws, pressure drops and heat exchanges, resulting in the calculation of the local gas velocity.
The local gas velocity, together with the local absolute pressure determine, together with the local suspension velocity of the particle and the gravity component, the acceleration/deceleration of the particle, resulting in the particle velocity.
The above-described complexity is the cause that many articles and thesis’s often do not describe the core of the physics of pneumatic conveying and get trapped in measurements, resulting in regression formulas with low accuracy in the calculation of new installations for a new material.
When a mis-interpretation of the Froude number is also introduced, the chaos is complete.
Belt conveying is volume conveying. Pneumatic conveying is mass conveying.
Applying a PD compressor in a pressure system, the air mass flow is “constant”.
Applying a PD compressor in a vacuum system, the air mass flow is “constant” for a specific vacuum.
In case of applying a centrifugal pump, which is not controlled at “constant” gas mass flow the air mass flow changes with the pressure drop.
Then, still the pneumatic conveying is considered as a mass conveying system at a specific pressure or vacuum.
The actual gas mass flow through the conveying pipe changes with the compressor characteristics (Internal leakage), rotary valve leakage, air mass replacing unloaded material from a tank, filter pulse air in case of vacuum conveying, etc.
Therefore, a pneumatic conveying calculation is based on the compressor gas mass flow mines the pressure dependent leakages and gas masses left behind in the system.
This makes it possible to use the Solid Loss Ratio to be used in the ruling formulas.
The gas mass flow and the material mass flow is constant over the whole pipeline.
From the constant gas mass flow, the actual gas volume at a specific location in the pipeline is calculated with the gas laws, pressure drops and heat exchanges, resulting in the calculation of the local gas velocity.
The local gas velocity, together with the local absolute pressure determine, together with the local suspension velocity of the particle and the gravity component, the acceleration/deceleration of the particle, resulting in the particle velocity.
The above-described complexity is the cause that many articles and thesis’s often do not describe the core of the physics of pneumatic conveying and get trapped in measurements, resulting in regression formulas with low accuracy in the calculation of new installations for a new material.
When a mis-interpretation of the Froude number is also introduced, the chaos is complete.
See: https://forum.bulk-online.com/showth...atic-conveying
Yarca pcs has solved the calculation complexity over the last 40 years. ■
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