The Research And Application On Optimization Design Method About The Push-pull Ventilation System In Workspace

Since the20thcentury, the number and the scale of the industrial building haveshown a trend of increase. During the production process the characteristics of thepollutant lie in the wide range of pollutants, the strong toxicity and the great pollutantemissions or transient emissions. In view of the above characteristics, local ventilationsystem in the emissions of the pollutants and workers’ operating zone has long beenregarded as the most efficient way to discharge the gas and dust. There exists a lot ofdesign methods of the local ventilation systems, in which the push-pull ventilationsystem has the advantage of saving energy and high ventilation efficiency. Due to thedesign methods of the push-pull ventilation system in operating zone are various and thesteps of design are relatively complex, it’s hard for this ventilation technology to getbroad used in practical engineering. The parallel air flow supply device has thecharacteristic of constant velocity and direction, so this paper focuses on the influenceof the disturbing airflow with angle and decrease of air suction to the flow field ofparallel push-pull ventilation system by methods of experimental tests and numericalsimulation. Then a practical project is analysed and optimal design methods are putforward.Firstly, the paper summed up the design methods of push-pull ventilation system inoperating zone recorded in classic papers. But by contrast it’s found that the designparameters calculated by using a combined consideration of push and pull air flowdesign method is more energy saving than using single push air flow design method.Economic and simple algorithm were calculated respectively and the result obtained bythe former is less than the latter. But in the practical engineering the simple algorithm ismore easily accepted by the designers because it has less parameters to be determined and ease of use.A parallel push-pull ventilation system test bench has been set up strictly according tothe flow rate ratio method of simple design method and installed in accordance with theexisting conditions, and use a small suction diffuser blowing parallel air flow as adisturbance airflow generator, and the flow field in the system testing, and the flowfield of the system was tested under different conditions to analysis the influence of thedisturbing airflow with angle and decrease of air suction to the flow field of parallelpush-pull ventilation system. By numerical simulation, the minimum suction air volumeof the equipment actually required under the design parameters was obtained. It wasfound that when the push-pull ventilation system flow field existed disturbing airflowwith angle under the condition of keeping other parameters constant, the whole flowfield did not change regularly with the change of the angle, illustrated that the simpledesign method has big safety margin. For the inherent size of the test bench in thelaboratory, the actual suction air volume required in the system Q3’ is63.6%of theoriginal design suction air volume Q3under the condition of keeping other parametersconstant and maintaining the same control effect. The optimal design method ofdecreasing the suction air flow relative to the original design method is put forward.The conclusion above is verified by using the existing push-pull ventilationexperiment results and proves the accuracy of the numerical simulation results. Thispaper calculates and obtains that the design suction air volume is greater than the actualair volume obtained by experiments under the condition of original installation size andequal polluted air flow (disturbing airflow) velocity using the simple design method andproves the numerical simulation method is accurate and reliable.