جستجوی مقالات مرتبط با کلیدواژه « افت فشار » در نشریات گروه « پزشکی »

Generally, geometrical parameters of the cyclone have a profound effect on determining its performance. The air outlet (Vortex Finder) as one of the cyclone’s components has a significant impact on the cyclone’s internal flow pattern, pressure drop and even dust removal efficiency.

Two different air outlets were designed in order to be easily installed and removed. The ribs (both in the opposite and the same swirl direction with the air flow) were inserted at the inner wall of the vortex finder. The step length of the blades was calculated to be 1.5. The dust feeder was injected the silica particles with a concentration about of 2.1 gr/m3 into the inlet air. The results of dust removal efficiency of the cyclone were calculated and compared for three groups of total dust, PM10 and PM2.5 in different experimental conditions.

Installation of spiral blades in same swirl direction as the air flow inside the cyclone increased 7.75, 7.73 and 6.75 percent in total efficiency, PM10 and PM2.5, respectively. The dust removal efficiencies for total dust, PM10 and PM2.5 increased by 2.6%, 2.33% and 1.5%, respectively, when the swirl direction of ribs and air flow was the opposite. The effect of helical blades on pressure drop for the first experimental setup (same direction) decreased by (- 2.5%) and in the second one (opposite direction) increased by (+ 2.03%). The best quality factor was also calculated for the cyclone with the blade aligned with the air flow direction.

Use of ribs in the inner wall of the cyclone vortex finder,  especially when the rotation direction of the ribs and airflow are the same, leads to a decrease in pressure drop and increase in dust collection efficiency which finally leads to improvement of cyclone performance.

Air pollution in industrial work environments has adverse effects on worker health, for example, chronic obstructive pulmonary disease and asthma. These diseases impose direct and indirect costs on society. In hierarchy controls, local exhaust ventilation is considered an "engineering control" to remove or control contaminants released in indoor work environments. It is one of the preferred ways to control employee exposure to air contaminants. The purpose of this research is to development a smart application for designing, selecting local exhaust ventilation systems.

At the first stage of this action research, was a developed visual Basic 6.0 based smart application for the design and selection of local exhaust ventilation systems. Then, for validation this application results obtained by the application were compared with the benchmarks. SPSS 22 software was used for statistical analysis and Bland–Altman plot was used to examine the agreement between the results.

Among the parameters, the maximum difference between similar results of the application and benchmark data was related to static pressure, which was 5% different in one series branch, which was balanced with another series branch. And the minimum difference was related to the calculated diameters with zero percent difference. . Bland – Altman plot showed that the standard deviation of the results of the four static pressure, velocity pressure and total pressure is in the range of (± 2 SD).

The application developed in this research has acceptable accuracy and its error is less than 5%.

Pulse jet systems are of interest due to their high filtration velocity,Theychr('39')re used as inlets from top and bottom. the purpose of this study was to compare the pressure drop and collection efficiency at the different inlet positions in a baghouse

In this experimental study, a pilot system was designed at 12ft/min permeability for MDF particles.For each inlet after several filtration-cleaning periods,pressure drop was measured by a manometer.Isokinetic sampling was also performed by Grimm1.108 monitor to determine the efficiency.To observe the behavior and Tyndall effect of particles, light and safety glass were used in one dimension of the baghouse

The mean pressure drop during the filtration-cleaning,the bottom inlet was 3CmWG, the top whit expansion inlet was 2.42CmWG,and the top flanged inlet was 2.57CmWG. but the particles settled on the expansion floor.The mean efficiency of top-expansion inlet was 99.995% and top-flanged 99.994%,significantly higher than the bottom inlet (99.974%).After several filtration-cleaning periods,The efficiency of  bottom inlet resulted 99.99%,top-expansion 99.97% and flanged 99.96%.There was no significant difference between the mean total efficiencies for different inlets.

The collection efficiencies were the same for baghouses with inlet from top and bottom.The pressure drop for baghouses with the top inlets was lower than the bottom inlet.It is recommended to use top inlets in case of predominantly fine particles with low density or in presence of a pre-separator,if  large particles,bottom inlet is recommended.Due to the slight difference of pressure drop and more functional limitation of the top inlet,bottom inlet in practice is preferred.

Air pollution is now recognized as an important environmental and health concern. Biological control processes, due to their durable, cost-effective and eco-friendly, have become a good alternative to physic-chemical methods. Biotechnology is based on the activity of microorganisms.
The aim of this study was to compare the capability of Pseudomonas Putida PTCC 1694 (bacteria) and Polarotus Stratus IRAN 1781C (mushroom) in the removal of toluene from the air stream and its biodegradation under same operating conditions. To this purpose, a bio filter containing two parallel columns was designed and constructed on a laboratory scale and the experiments were carried out based on measuring the removal efficiency (RE), elimination capacity (EC) and pressure drop in these two columns. Thus, the bacteria were inoculated in one of the columns and in the other the fungus was inoculated. The bacterial testing lasted for 20 days and the fungal testing lasted for 16 days. The contaminant loading rates (LR) for bacterial and fungal bio filters were 11.65±2.26 and 11.94±2.56 g/m3.h, respectively. The results showed that the fungal bio filter was more capable of eliminating of toluene vapor than bacterial bio filter (9.65±3.53 vs 9.18±2.6 g/m3.h). However, the pressure drop in the bacterial bio filter was lower than the fungal bio filter (1±0.28 vs 1.1±0.32 cm water). According to the results, fungal bio filtration appeared to be more successful than bacterial bio filtration in the removal of toluene.

Background and The emission of hydrogen sulfide (a malodorous and toxic pollutant) into the atmosphere is considered a public health concern due to its potential hazardous effects on human health. Therefore, the removal of hydrogen sulfide from polluted air streams is of paramount importance. This study aimed to evaluate the role of a polyurethane foam/palm fiber-based biofilter in the removal of hydrogen sulfide.
Air stream containing H2S was introduced into the biofilter at a flowrate of 7 L/min and an empty bed retention time (EBRT) of 47 seconds. The inlet and outlet concentrations of H2S were measured. Moreover, the amount of sulfate and pH in bed, leachate from the biofilter and pressure drop along the biofilter height were monitored.
In this study, the biofilter provided 100% removal efficiency for inlet H2S concentration of 288.0 mg/m3 at EBRT of 47 seconds. The maximum elimination capacity (ECmax) of the biofilter was 24.1 g/m3.h at a loading rate of 28.0 g/m3.h, corresponding to a removal efficiency of 86.1%. As the elimination capacity of H2S increased the sulfate content of packing bed increased to 10.8 mg/g bed and the pH reduced to The polyurethane foam/palm fiber mixture could be considered as a potential biofilter carrier, with low-pressure drop, to treat air streams containing H2S.

The goal of the present study was to develop nanofibrous media filters containing MgO nanoparticles for future application in removing particles from gas stream.
Electrospun nanofibers were fabricated using experimental design prepared by Response Surface Methodology. Optimization of electrospinning parameters was conducted for achieving the desired filter properties including fiber diameter, porosity, and bead number. After taking SEM images, the determination of fiber diameter and number of beads were performed through Image Analysis and the calculation of porosity percent was performed by MATLAB. A filter media was produced based on the optimized conditions of electrospinning and it was certified by the HEPA filter performance test.
In terms of morphological quality of fibers including fiber uniformity, absence of branching and lower numbers of beads, experiment standard No. 2 (STD 2: concentration 16 wt%, voltage 10 kV, and distance 15 cm) had the best combination. Maximum fiber diameter was also observed in STD 2. Among the electrospinning, the highest correlation coefficient was observed between solution concentration and response variables and the relationship between concentration and both fiber diameter and porosity percent was statistically significant (p 0.05) and a weak negative relationship was seen between fiber diameter and bead number (r=-0.2, p>0.05).
Solution concentration was found as the most affecting factor on the filter properties, so that the higher concentration leaded to the lower bead number and greater fiber diameter. Increase in fiber diameter resulted in larger pore size and higher porosity. Quadratic models were known for understudy variables. Efficiency of the optimized filter was comparable with the HEPA filter and it had the lower pressure drop.

The main goal of this study was to investigate the capability of regenerated rice husk silica after saturation to remove Hydrogen sulfide (H2S). For this purpose, rice husk silica and regenerated rice husk silica were used as adsorbents bed in filter. A poly vinyl chloride filter with one liter of prepared bed was tested. Rice husk silica was prepared in a furnace at temperature of 800 ºC for Four hours, after acid leaching. Saturated rice husk silica was regenerated in a furnace at temperature of 800 ºC for Four hours too. Removal efficiency, elimination capacity, and pressure drop were the three parameters to evaluate the filters bed. System were operated with empty bed residence time of 60 s and different inlet concentration of H2S from 10 to 300 part per million (ppm). More than 98% of removal efficiency was observed for both packed filters at inlet concentrations of H2S. The maximum elimination capacity was 7.02 gm-3h-1 with H2S mass loading rate of 9.0 gm-3h-1 in the both beds. This study showed that at a 1.0 lmin-1 flow rate and different concentration of inlet H2S. There is no significant difference between the rice husk silica and the regenerated rice husk silica beds in the amount of removal efficiency (p< 0.01). Also, there is no significant difference between these two beds in the amount of elimination capacity at the same condition (p< 0.01). Moreover, this study showed that the amount of pressure drop was undetectable (zero) in both filter’s bed. The results of this study showed the regenerated rice husk silica has the same performance of the primary rice husk silica, Therefore it can be considered as a suitable and inexpensive bed to remove H2S at low concentration.

In recent years researchers have shown that increasing in pressure drop and low amount of elimination capacity are two main limitations of biofiltration systems in pollutants treatment. Therefore, the main goal of this study was to investigate the relationship between pressure drop and hydrogen sulfide (H2S) elimination capacity with different mass loading rates in biofiltration system using activated sludge and mixed activated sludge and rice husk silica as packing materials. Two poly vinyl chloride (PVC) filters with one liter of prepared bed were tested for each filter. Dried activated sludge was collected from Putrajaya sewage treatment plant in Malaysia. The system was tested from different empty bed residence time (EBRT) from 30 to 90 sec and different H2S mass loading rate from 18.36 to 54 gm-3h-1. Based on the statistical analysis of Pearson correlation, there was a direct and very high relationship between the increasing hydrogen sulfide mass loading rate and the amount of pressure drop in the both packed filters (p<0.01). Also, with the H2S mass loading rate of 54 gm-3h-1 and EBRT of 30 s, the maximum elimination capacity was obtained in the activated sludge and mixed rice husk silica with dried activated sludge packed filters up to 52.32 and 44.33, respectively. Moreover, based on the statistical analysis of the Pearson correlation, there was a direct and very high corelatior between the increasing H2S mass loading rate and the amount of pressure drop in the both filters (p<0.01). After 53 days of operating time and 54 gm-3h-1 of mass loading rates, the maximum pressure drop reached to 3.0 and 8.0 (mm H2O) for the mixed rice husk silica with dried activated sludge packed and dried activated sludge packed filters, respectively. Based on the results of the study, there is a direct and positive relationship between the increasing H2S mass loading rate and the amount of pressure drop and elimination capacity in both filters, but mixed rice husk silica with dried activated sludge showed higher elimination capacity and lower pressure drop.

Dual media filters have two different layer beds consist of sand and Anthracite. Advantage of dual media filters is longer run duration and more filtration rate. The purpose of this study was to achieve a performable model to improve single media Filters in water treatment plants. in this cross-sectional study, two pilots; mono and dual media were made and in a 5 month period samples taking were done. Total samples taken from input and output of each pilot, was 40. The samples then introduced for the measurment of turbidity and total organic carbon. Meanwhile the filters head loss also quantified in 40 times head loss measurement was done. Average turbidity removal in mono and two layer pilots were 63 and 65 percent respectively. Average removal of Total Organic Carbon in mono and two media pilots were 40 and 66 percent respectively. Head loss in dual and single media pilots were 0. 68 and 1.15 m respectively. Although average torbidity removal disparity between two pilots was not significant the amount of total organic carbon removed was considerable. Average head loss in single media pilot was more than dual media type. Ratio of UFRV in dual media to mono media filter was 51:30 it shows that filtration rate capacity will be improved up to70 percent by changing media type