Analysis of three commonly used test methods for filtration efficiency

Three test methods of filtration efficiency (weight method, colorimetric method and atmospheric dust counting method) 　　 The 'filtration efficiency' of an air filter is the ratio of the amount of dust captured to the original air dust content: 　　 the actual meaning of the filter efficiency and The specific value varies greatly from experiment to experiment. When determining the filtration efficiency, the meaning of 'quantity' is varied, and the efficiency values u200bu200bmeasured and calculated from this are also varied. In engineering, in order to save trouble and to reduce misunderstandings, there have been several methods of expressing efficiency specifications with codes.　　Test method: 　　　　Gravimetric method Arrestance: 　　The source of test dust is large particle size, high concentration standard dust. The main component of the dust is the sifted dust in the specified area, and then mixed with the specified amount of fine carbon black and short fiber. Most countries stipulate the use of 'Arizona Road Dust' from the Arizona desert in the United States. The Chinese standard once stipulated the use of dust from a village on the Loess Plateau, and the Japanese standard stipulated the use of 'Kanto Asian clay' originating from Japan. The measured 'quantity' is the dust weight.　　The filter is installed in the standard test wind tunnel, and dust is continuously generated at the upwind end. At regular intervals, measure the weight of dust passing through the filter or the amount of dust collected on the filter to obtain the filter efficiency calculated by the weight of dust at this stage. The final weighting efficiency is the weighted average of the efficiency of each test stage according to the amount of dust generated.　　 The conditions for the termination of the gravimetric test are: the agreed final resistance value, or when the efficiency is significantly reduced. The so-called 'agreement' here refers to the agreement between the client and the experimenter, or the experimenter's own regulations. Obviously, the agreed upon termination test conditions are different, the weight efficiency value will be different.　　 When the test is terminated, the weight of the test dust contained in the filter is called the 'dust holding capacity'. The 　　 gravimetric method is used to measure low-efficiency filters, and those filters are generally used for pre-filtration in central air-conditioning systems.　　 Gravimetric test is a destructive test and cannot be used in the daily product performance inspection of the manufacturer.　　Related standards: American ANSI/ASHRAE 52.1-1992, European EN779-1993, China GB12218-89.　　　　 atmospheric dust counting method: 　　 the source of dust is 'atmospheric dust' in the natural atmosphere. The 'quantity' of dust is the total number of particles greater than or equal to a certain particle size. The instrument for measuring dust is ordinary optical or laser dust particle counter. The efficiency value is the initial efficiency of the new filter.　　Name explanation　　A, B, C, D　　The classification of airborne molecular pollutants in the integrated circuit manufacturing industry. A stands for Acids, B stands for Bases, C stands for Condensables, and D stands for other dopants.　　Absolute Filter, Absolute Filter　　In the early days, a foreign company used the trade name for a partitioned high-efficiency filter, which corresponds to a filtration efficiency of 99.97% (0.3mm DOP).　　AC fine (Air Cleaner Test Dust, fine), AC fine ash　　The standard dust used in the performance test of filtration and dust removal equipment stipulated by the United States is common in all countries except China and Japan. The dust was taken from the desert area of u200bu200bArizona in the United States, commonly known as Arizona Road Dust.　　A specified amount of short fiber and carbon black are mixed into AC fine ash to become the ASHRAE standard dust commonly used in filter tests.　　 The International Organization for Standardization ISO stipulates that AC fine ash is used to measure the filtering effect of automobile filters.　　Aerosol, a relatively stable suspension system formed by solid or liquid particles and gas.　　 Internationally, most people engaged in filtration theory participate in the activities of the Aerosol Society, but those engaged in filtration applications prefer to get together in the HVAC industry.　　AFI (Air Filter Institute), the test method of filtration efficiency of the United States Air Filtration Institute 　　The gravimetric method and colorimetric method were first used by AFI, some people call AFI efficiency. If you see 'AFI efficiency　　AHU (Air Handling Unit), central air conditioner 　　　　 colorimetric method Dust-spot: 　　The test bench and test dust are the same as the gravimetric method. The 'quantity' of dust is the amount of light passing through the high-efficiency filter paper at the sampling point.　　 Sampling before and after the filter, there is a high-efficiency filter paper on the sampling head, obviously, the pollution degree of the high-efficiency filter paper at the sampling point before and after the filter will be different. In the test, after a period of dust generation test, the light transmission of the high-efficiency filter paper at the sampling points before and after the filter is measured in the non-dust state, and the so-called 'filtration efficiency' is obtained by comparing the difference in the light transmission of the filter paper with a prescribed calculation method. The final colorimetric efficiency is the weighted average of the efficiency values u200bu200bat each stage of the test process according to the amount of dust generated.　　 The conditions for terminating the test are similar to those of the weight method: the agreed final resistance value, or when the efficiency drops significantly. The 　　 colorimetric method is used to measure high-efficiency general ventilation filters. Most filters in air conditioning systems belong to this type of filter. The colorimetric method used to be a common test method abroad, and this method is gradually replaced by the counting method.　　Strict colorimetry is a destructive test.　　Related standards: American ANSI/ASHRAE 52.1-1992, European EN 779-1993.　　　

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