Effects and New Applications of Pulsed Flow

Abstract

Pulsed flow has been widely applied in the past for special applications as in jigging or sorting devices, extraction columns, and fluidized-bed dryers. Recent developments and detailed examinations demonstrate several effects which can be achieved in pulsed operation modes. Here, low-frequency oscillations are considered, providing a more or less uniform phase state along the flow. Secondary flow is induced at obstacles and can be widely controlled by pulsation parameters keeping the backmixing effect low, despite of high transversal mass or heat exchange intensification. At walls, lift forces on particles within the thin boundary layers are beneficial for keeping particles from building deposits on surfaces or on permeable membranes. Broken symmetry devices generate a directed flow even when operated by a harmonically pulsed fluid. At oscillating interfaces, a distinct secondary flow is observed, well-suited to intensify mass transfer.

Enhancing fluidization stability and improving separation performance of fine lignite with vibrated gas‐solid fluidized bed

“…[25][26][27][28] Several investigators proposed pulsing air separation technology to improve segregation efficiency. [29] Nevertheless, introducing vibration energy to a dense medium gas-solid fluidized bed, named a vibrated gas-solid fluidized bed, shows great advantages and application potential. [30] Generally, the bed utilizes material with a broad particle size and steady density composition as the main separating medium solids.…”

“…A few researchers introduced external force fields to improve separation efficiency of fine coal, such as vibration, magnetic, and electric force fields . Several investigators proposed pulsing air separation technology to improve segregation efficiency . Nevertheless, introducing vibration energy to a dense medium gas‐solid fluidized bed, named a vibrated gas‐solid fluidized bed, shows great advantages and application potential .…”

Influence of Nozzle Parameters on Spray Pattern and Droplet Characteristics for a Two‐Fluid Nozzle

“…High liquid density at constant nozzle parameters results in a more compact spray that is less affected by the atomization gas 2. In literature, different droplet size correlations for nozzles with external mixing are present based on various fluid properties as well as methods of droplet size measurement 3, 11, 14–17. However, the influence of the parameters on the resulting droplet size as well as spray angle is strongly dependent on the design and size of the nozzle 10.…”

Slip and Characteristic Velocities in a Horizontal Pulsed‐Plate Extraction Column

“…The efficiency of liquid-liquid contactors is primarily dependent on the degree of turbulence imparted to the system and the interfacial area available for mass transfer. Pulsed columns have a clear advantage over other mechanical contactors due to their high separation efficiency by reducing axial mixing and increasing the drop breakup and coalescence rate [3][4][5][6][7]. The absence of moving mechanical parts in such columns slightly obviates repair and servicing.…”