Articles
MODELING OF HEAT TRANSFER AND FLOW PATTERN IN A COOLING AIR JACKET OF SPRAY DRYER
Article number
1054_26
Pages
221 – 228
Language
English
Abstract
Spray-drying of selected liquids with sugar components is difficult, because these materials stick on the dryer wall.
Using a cooling air jacket decreases the stickiness and optimizes powder-deposition on the dryer wall; however, it cannot eradicate this problem completely.
In current research, a co-current spray dryer (tall-form) was modeled by the CFD method, and the flow-pattern in cooling the air jacket and the temperature variation were estimated.
The dryer chamber was surrounded by a cooling air jacket and the chamber wall jacket was cooled by a 1400 m3/h blower which provided ambient air to the jacket from the end of the conical part of the dryer, and extracted the air from the top of the cylindrical part of the dryer.
Temperature in the dryer was measured by several transmitters in order to verify the modeling results.
Numerical modeling of the heat transfer in a cooling air jacket of a spray dryer was achieved by employing the computational fluid dynamic method.
The k-ε standard model was considered for turbulence simulation.
Velocity magnitude and temperature variation, in the chamber and in the cooling air jacket, were investigated in this modeling.
Velocity variation for different heights of the chamber and for temperature were measured by a portable hot-wire anemometer and by some installed transmitters on the dryer wall in order to verify the numerical modeling results.
Given the flow path line in the air jacket, the air layer path lines had a harmonic motion relative to each other with minimum axial velocity variation.
Air velocity in the axes was also at the maximum.
In the conjunction of the cylindrical and conical parts of the dryer jacket, there was a small amount of flow deviation towards the wall.
The temperature contour indicated there was intensive temperature reduction around the core flow.
The flow in the cooling jacket caused a temperature reduction in the dryer wall, especially in the boundary of the chamber cone part.
Using a cooling air jacket decreases the stickiness and optimizes powder-deposition on the dryer wall; however, it cannot eradicate this problem completely.
In current research, a co-current spray dryer (tall-form) was modeled by the CFD method, and the flow-pattern in cooling the air jacket and the temperature variation were estimated.
The dryer chamber was surrounded by a cooling air jacket and the chamber wall jacket was cooled by a 1400 m3/h blower which provided ambient air to the jacket from the end of the conical part of the dryer, and extracted the air from the top of the cylindrical part of the dryer.
Temperature in the dryer was measured by several transmitters in order to verify the modeling results.
Numerical modeling of the heat transfer in a cooling air jacket of a spray dryer was achieved by employing the computational fluid dynamic method.
The k-ε standard model was considered for turbulence simulation.
Velocity magnitude and temperature variation, in the chamber and in the cooling air jacket, were investigated in this modeling.
Velocity variation for different heights of the chamber and for temperature were measured by a portable hot-wire anemometer and by some installed transmitters on the dryer wall in order to verify the numerical modeling results.
Given the flow path line in the air jacket, the air layer path lines had a harmonic motion relative to each other with minimum axial velocity variation.
Air velocity in the axes was also at the maximum.
In the conjunction of the cylindrical and conical parts of the dryer jacket, there was a small amount of flow deviation towards the wall.
The temperature contour indicated there was intensive temperature reduction around the core flow.
The flow in the cooling jacket caused a temperature reduction in the dryer wall, especially in the boundary of the chamber cone part.
Authors
O.R. Roustapour, M. Hosseinalipour
Keywords
spray dryer, computational fluid dynamic (CFD), cooling jacket, modeling, stickiness
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