Vortex airflow

The airflow pattern in rooms ventilated by linear attached jets with L/H ratio greater than that for effectively ventilated rooms was studied by Schwenke and Muller. The results of their air velocity measurements ami visualization studies indicate that there are secondary vortexes formed downstream in the room and in the room corners. The number of downstream vortexes and their size depend upon the room length (Fig. 736b). Mas,s transfer between the primary vortex and the secondary vortex depends upon the difference in characteristic air velocities in the corresponding flows (/, and Ui and can be described using the Stanton number, St . ... 

An increase of the capture airflow rate normally results in increased capture efficiency, but the relationship between these quantities is not linear. A case-by-case evaluation is necessary to establish this relationship. In every case an increase of the airflow rate causes an increase of the operating costs. Analogously, a decrease in airflow rate leads to a decrease in capture efficiency and in some cases, a total breakdown of the capture effect (e.g., capture dev ices working with the vortex principle require minimum airflow rates). 

It has also been shown, using visual illustrative methods, that accumulation can occur in the wake of people or objects, provided that the contaminants are emitted in the vortex region. Special consideration must be taken with instabilities and vortices generated by the working person. Vortices can also occur in empty open unidirectional airflow benches. 

However, one should be cautious when comparing the Reynolds number from regular Karman vortex streets with the Reynolds number calculated from factual situations in clean benches as the airflow from behind an obstacle is usually not the typically formed Karman vortex street predicted for an indefinitely long circular cylinder. The wake situations during actual conditions often seem to have a three-dimensional stmcnire. 

Egg crate straighteners A lattice device inserted in a ductwork run to straighten the airflow vortex after a bend or other directional change. 

Figure 8.10. Airflow in a hydraulic kiln, (a) On the left, the recirculating air ft om the fans has to take a right-angle bend to enter the plenum space and the airstream breaks free from the surface to form a vortex. This hinders air moving thought the upper layers of the stack, (b) On the right, more uniform airflow with a radiused edge and wide plenum space (Nijdam, 1998).

The installation parameters of pneumatic fan has a significant impact on the effect of eliminating the vortex zone, the optimum parameters of pneumatic fan are as follows the vertical distance from pneumatic fan to the outer side wall in upper roadway is 5 meters, exit velocity is 25 in/s, the angle between airflow direction of pneumatic fan and main airflow direction is 0°. 

Compared with model one, because of lack of shunt plate, movement of vortex pairs of model two is very unsteady, which will influence the continuity and stability of high-speed airflow, through velocity is swifter because of the change of filter layout, the distance between the first filter and entrance extended segment become small, the vortex make the first filter nearly useless, which cause the velocity of air flow reduce about 1/3. 

Stream and generated a vortex flow which leads to a faster droplet freezing as well as a droplet deflection to prevent droplet collisions. The temperature was reduced at the nozzle position from room temperature to —75 °C for gas flows ranging between 17 and 34 L/min (Fig. 10.12). Different nozzle positions inside the vortex were evaluated experimentally. Additionally, the influence of the airflow of the cold gas... 

The vortex method, one existing vacuum generation technique, allows mobile robots to maintain a solid grip by means of a constant airflow that creates a suction that in turn produces negative pressure in this closed area, resulting in the necessary force of attraction between the robots and the wall. 

Figure 9. (a) Airflow in the impeller (b) centrifugal impeller used in the vortex attractor... 

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