Pneumatic conveying is based on the principle of a flowing gas through a pipeline, exerting a drag force on a material particle.
The drag force, acting on the particle, transfers impulse from the air to the particle, changing the momentum.
As the mass of the particle is constant, the transferred impulse changes the velocity of the particle.
The change in the particle velocity, changes the kinetic energy of that particle.
The changed kinetic energy of the particle is at cost of the internal energy of the flowing gas.
As in pneumatic conveying the flow resistances are converted back into energy and heat up the gas and the heat stored in the particle keeps the flowing gas close to the material temperature, the gas will expand at approx. a constant temperature.
Along the pipeline, heat energy will be lost or gained through the pipe wall by the difference in the mixture temperature and the environment temperature, influence by the degree of insulation of the pipeline.
To create a gas flow through a pipeline, the inlet pressure must be increased by a compressor (pressure system) or the end pressure must be decreased (vacuum system)
The compression in a pressure system heats the conveying gas temperature, which is cooled to, at least, the material temperature and the required conveying energy is supplied by the internal energy of the gas.
The internal energy of a gas is given by the gas temperature.
Without friction losses in the gas/material flow, the temperature would decrease but as described here before, the conveying temperature is close to the material temperature along the pipeline.
This observation (supported by calculations) indicates that the internal energy of the gas at an almost constant temperature requires heat flows along the pipeline between the particles and surroundings.
For an accurate calculation, these various heat flows at different pressures and conditions must be accounted for.
A compressor principle in a pressure system is important, because of different compression temperatures (with or without aftercooling).
Thermo dynamics of pneumatic conveying.
Pneumatic conveying is based on the principle of a flowing gas through a pipeline, exerting a drag force on a material particle.
The drag force, acting on the particle, transfers impulse from the air to the particle, changing the momentum.
As the mass of the particle is constant, the transferred impulse changes the velocity of the particle.
The change in the particle velocity, changes the kinetic energy of that particle.
The changed kinetic energy of the particle is at cost of the internal energy of the flowing gas.
As in pneumatic conveying the flow resistances are converted back into energy and heat up the gas and the heat stored in the particle keeps the flowing gas close to the material temperature, the gas will expand at approx. a constant temperature.
Along the pipeline, heat energy will be lost or gained through the pipe wall by the difference in the mixture temperature and the environment temperature, influence by the degree of insulation of the pipeline.
To create a gas flow through a pipeline, the inlet pressure must be increased by a compressor (pressure system) or the end pressure must be decreased (vacuum system)
The compression in a pressure system heats the conveying gas temperature, which is cooled to, at least, the material temperature and the required conveying energy is supplied by the internal energy of the gas.
The internal energy of a gas is given by the gas temperature.
Without friction losses in the gas/material flow, the temperature would decrease but as described here before, the conveying temperature is close to the material temperature along the pipeline.
This observation (supported by calculations) indicates that the internal energy of the gas at an almost constant temperature requires heat flows along the pipeline between the particles and surroundings.
For an accurate calculation, these various heat flows at different pressures and conditions must be accounted for.
A compressor principle in a pressure system is important, because of different compression temperatures (with or without aftercooling).
The same theory applies for vacuum systems. ■
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