第一章 奈米微粒穿透海綿濾材特性研究
第五節 結論與建議
1.在相同海孔隙度與表面風速之下，填充密度越高其產生壓降會越大，且壓降變化會 與其填充密度成二次方的關係。在相同表面風速之下，海綿孔隙度越大壓降越大，
且在相同孔隙度，表面風速與壓降會成一線性關係。
2.微粒穿透率會隨著表面風速的減小而降低。相同表面風速之下，微粒越小擴其穿透 率越低。海綿濾材過濾品質隨表面風速增加而下降。
3.海綿填充密度越大其微粒穿透率越低，不過因為其所產生壓降與填充密度成二次方 正比關係，因此反而使得過濾品質降低。因此，若以過濾品質觀點而言，增加海綿 填充密度反而會增加能源消耗。
4.在相同操作條件之下纖維直徑越小其微粒穿透率越低，不過若要達到與高孔隙度的 海綿相同微粒收集率必須增加低孔隙數海綿數量達數倍。
5.論以實驗結果或是從單一纖維理論推估，在不同操作條件所得的趨勢均相同。只是 單一纖維理論其假設狀況與實際狀況有些許差異，如：單一纖維假設纖維直徑均 一，而實際上海棉纖維交接處直徑並非與纖維直徑相同；單一纖維理論的假設為二 維與實際上海綿纖維構成三維的骨架結構並不相同等。這些結果也造成了單一纖維 理論值與實驗值並無法完全符合的狀況。
6.微粒在海綿濾材中隨著氣流運動，同時受到擴散沈積、慣性衝擊沈積與攔截沈積等 機制影響。因此，不同大小微粒在不同表面風速之下雖然擁有相同佩雷數其微粒穿 透率也有一定差距。
7.本研究利用小型雙鋸齒狀靜電集塵器由實驗結果觀察到，在不同電場電壓在靜電集 塵器的穿透率，微粒的靜電飄移速度與電場強度和微粒帶電量的乘積成正比，因此 電場強度越低則收集效率就越差。另外當微粒小至某一程度之後，常會有充電不足 的現象，因此靜電集塵器的收集效率反而會有下降趨勢。
8.利用海綿濾材串接於靜電集塵器之後，在一定的操作條件之下確實可以有效控制奈 米微粒。以海綿過濾品質而言，使用靜電集塵器可以有效增加各粒徑微粒的過濾品 質，其過濾品質隨著流量減少而增加。
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Figure 1. Schematic diagram of the experimental setup for filter foam and ESP penetration test.
High Voltage Power Supplier
Filtered Air
Filter Foam Honeycomb
Kr-85
Exhaust Air
Constant Output Atomizer
SMPS
(A) Dual Saw-like Electrode ESP
25
Figure 2. Schematic diagram of the home-made holder for filter foa .
O Honeycomb F
Aerosol
Figure 3. Pressure drop of filter foams as a function of packing density (A) and face velocity (B).
Packing density
0.0 0.1 0.2 0.3 0.4 0.5 0.6
Pressure drop, mmH 2O
0 50 100 150 200
Face velocity, cm/sec
0 10 20 30 40 50 60 70
Figure 4. Effect of the face velocity on aerosol penetration and filter quality.
Po=100 ppi, T= 2.54 mm, α= 0.36
Aerosol penetration, %
0
Aerosol Diameter, nm V, cm/sec
Aerosol diameter, nm
10 100
Filter quality, mmH2O-1
0.001
Figure 5. Effect of the packing density on aerosol penetration and filter quality.
Figure 5. Effect of the packing density on aerosol penetration and filter quality.
Po= 100 ppi, V= 9.5 cm/sec
Aerosol penetration, %
0
Aerosol diameter, nm
10 100
Filter quality, mmH2O-1
0.001
Figure 6. Effects of the foam porosity on aerosol penetration and filter quality.
Figure 6. Effects of the foam porosity on aerosol penetration and filter quality.
V=22 cm/sec, T=4.23 mm, α=0.216
Aerosol penetration, %
0 20 40 60 80 100 120
Po, ppi 110 100 80 60 40
Aerosol diameter, nm
10 100
Filter quality, mmH2O-1
0.01 0.1 1 10
10 100
Model Experiment
Figure 7. Peclet number versus aerosol penetration under different velocity.
0.001 0.01 0.1 1 10 100
Aerosol penetration, %
0 20 40 60 80 100
Peclet Numbers
0 20 40 60 80
100 Model
Expermental 5.6 9.4 23.7 33.8 63.2 V, cm/sec
Figure 8. Aerosol penetration curves under different applied electrode voltages at a flow rate of 80 L/min.
Aerosol diameter, nm
10 100
Aeros ol penet rat ion, %
0 20 40 60 80 100
120
Va, -kV Q= 80 L/min
6 5 4 3
Figure 9. Aerosol penetration curves of ESP under different flow rates at an applied electrode voltage of -6 kV.
Va= -6kV
Aerosol diameter, nm
10 100
Aerosol penetration, %
0 20 40 60 80 100 120
Q, L/min
120 100 80 60 40
Figure 10. Aerosol penetration curves through filter foam and ESP at an applied electrode voltage of -6 kV.
Dual saw-like ESP : Va= -6kV
Foam filter media: Po= 110ppi, T= 25.4 mm, α=0.036
Aerosol diamerer, nm
10 100
Aerosol penetration, %
0 10 20 30 40 50
100 60 40 Q, L/min
Figure 11. Collection efficiency curves of ESP, foam, and both in series.
Aerosol diameter, nm
10 100
Collection efficiency , %
0 20 40 60 80 100 120
Foam
ESP+ Foam
ESP
Foam( Po= 110 ppi, T= 25.4 mm, α= 0.036) ESP (Va= -6 kV, Q= 100 L/min)
Figure 12. Filter quality curves of foam and ESP plus foam.
Aerosol diameter, nm
10 100
Filter quality, mmH
2O -1
0.01 0.1 1
Q, L/min ESP+Foam Foam
Porous foam( Po= 110 ppi, T= 25.4 mm, α= 0.036) ESP ( Va= -6 kV)
100 60 40
ESP+Foam
Foam