Filter Beta Ratio

카트리지 필터 등의 데이터시트를 보다 보면, B25=1000 라는 알수없는 계산식을 볼 수 있다.

매 번 볼때마다 찾아보고 이해해도 다음에 또 만나면 또 찾아보는... 멍청한-_-;

그래서 정리해보면..

아래 영문 설명에 따라 이해한 바로는, Bx의 x는 걸러지는 입자의 사이즈. Bx=Y에서 Y는, 총 몇개중 하나가 안걸러지고 지나가느냐는 것.

 

즉, 어떤 필터에 25마이크론짜리 파티클을 1000개를 흘려 보냈을 때 한 개만 통과된다면 이건

B25=1000 이 되는 것. 이때의 25micron은 absolute Fineness.

Absolute fineness는 거의 100%걸러낼 수 있는 입자 크기.

Nominal Fineness는 60~98%정도 걸러낼 수 있는 최소 입자 크기.

 

*Beta ratio가 클수록 필터의 성능이 좋은 것임.

*보통 Nominal이 Absoulte보다 작다(당연)

위는 표기가 그렇다는거고, 실제 beta ratio는 filter후단 파티클 수 대비 전단 파티클 수.

즉 1000이면, 입자 수가 후단이 1이고 전단이 1000. 1000개중 1개만 흘려보낸다는 뜻임. 마찬가지로 beta ratio가

클수록 성능이 좋음.

Beta ratio

Until recently there has not been any universally accepted test method to measure or describe the media pore size or the size of particles a filter media can capture and hold. Fortunately now a test procedure called multi-pass testing or Beta ratio testing is a universally accepted test method that yields readily comparable test results.

It was introduced with the object of giving both filter manufacturer and user an accurate and representative comparison amongst filter media.

Multi-pass testing uses a specified contaminate, of known sizes, added regularly in measured quantities to the fluid which is pumped continuously through the filter. Measured samples of the fluid are then taken at timed intervals from both the downstream and the upstream of the filter simultaneously, particles are measured and counted by electronic means using automatic particles counters.

From these measurements a Beta ratio (b) is formulated by dividing the number of particles of a particular size in the upstream flow by the number of particles of the same size in the downstream flow:

β = Nu / Nd

where bx is the beta ratio for contaminant larger than x mm

Nu is the number of particles larger than x mm per unit of volume upstream

Nd is the number of particles larger than x mm per unit of volume downstream.

The beta ratio is an indicator of how well a filter controls particulate: i.e., if one out of every two particles (>xmm) in the fluid pass through the filter, the beta ratio at xmm is 2, if one out of every 200 of the particles (>xmm) pass through the filter the beta ratio is 200.

Therefore, filters with a higher beta ratio retain more particles and have higher efficiency.

Efficiency for a given particle size (Ex) can be derived directly from the beta ratio by the following equation:

Ex = (βx-1)/x  * 100(%)

 

Read more: http://www.lenntech.com/library/fine/beta/beta-ratio.htm#ixzz3dPA7VrwW

 

출처: <http://www.lenntech.com/library/fine/beta/beta-ratio.htm>