1、 UDC 534.61 : 66.045.5 :534.835.46 DEUTSCHE NORM June 1985Measurement of noise emitted by machinesAirborne noise emissionEnveloping surface methodCooling towersDIN45635Part 46Gerauschmessung an Maschinen; Luftschallemission; HGllflachenVerfahren; KuhlturmeIn keeping with current practice in standard
2、s published by the International Organization for Standardization (ISO),a comma has been used throughout as the decimal marker.ContentIContinued on pages 2 to 4I MA/I/Natural-draught cooling tower,water flow rate:40 to 60 103 m3/hT Up to 160 mv30t040m4 InstrumentationAs specified in DIN 45635 Part 1
3、.Page7 Evaluation. 48 Precision and uncertainty ofmeasurement results . . . . . . . . . . . . . . . . . . 49 Test report . . . . . . . . . . . . . . . . . . . . . . . . 410 Report on results . . . . . . . . . . . . . . . . . . . 4Standards referred to . . . . . . . . . . . . . . . . . . . . 43 Termi
4、nology, quantitiesAs specified in DIN 45635 Part 1.5 Object under test and test conditions5.1 Object under testThe object under test is the cooling tower consisting ofthe structure (generally the cell or tower) with the fill(recooling element in the case of a dry cooling tower orthe trickle grids, w
5、ater distribution system and basin inthe case of wet cooling towers). If other noise generatorshave to be included in the object under test or parts ofthe installation are not to be included, a particularreference shall be made to this fact (see subclause 6.3).Typical cooling tower designs are shown
6、 in figure 1.Circular mechanical draughtcooling tower, water flow rate:15 to 20.103m3/h. . :Oto20m JKI-L+-:i!-L+-l-r+1JCell cooling tower,water flow rate:about 5000 m3/h per unitFigure 1. Comparison of sizes of the three most common types of cooling towerI_I;CoeZPage1 Scope and field of application.
7、 . . . . . . . . . . . 12 Designation 13 Terminology, quantities . . . . . . . . . . . . . . . . 1.5 4 Instrumentation 15 Object under test and test conditions. . . . . . . 16 Test procedure . . . . . . . . . . . . . . . . . . . . . . 3“c:c:.CJ- en l:.Qf;-gZE.:Q,) :e?Q.LLc:-.0ogQJ:CuJ: t-1Beuth Verl
8、ag GmbH, Berlin. has the exclusive right of sale for German Standards (OIN-Normen).10.87DIN 45635 Part 46 Engl. Price group 5Sales No. 0105Page 2 DIN 45 635 Part 465.2 Operating condition of cooling tower(main operating condition)The measurement shall be made at rated load (ratedvolume flow of fans,
9、 if used, rated water flow rate andrated cooling power). In the case of natural-draught drycooling towers, the measurement shall be made at atemperature close to the design temperature, i.e. at therated cooling power 1) and rate of water flow throughthe cooling elements.5.3 Test siteMeasurement shal
10、l be carried out on site.5.4 Measurement surface and measuring pointsThe noise is radiated from cooling towers mainly throughthe air outlet and the air inlet and from the fan motorswhere these are fitted. If the level of noise radiated fromthe walls or the shell (particularly from diffuser walls) is
11、not low enough to be ignored, appropriate measurementsurfaces and arrangements of the measuring points shallbe defined. For separate determination of the partialsound power levels for each partial sound source, measure ment surfaces shall be defined and the measuring pointslying on them arranged as
12、shown in figures 2 and 3.In the case of large-size wet cooling towers, the soundpower passing through the air outlet is caused mainlyby the noise of the water distribution system and,because of sound absorption in the damp air, it dependson the height of the cooling tower, H, and on theformation of
13、water vapour inside the cooling tower.Since the latter is subject to substantial variationsaccording to weather conditions, the sound powerpassing through a measurement surface above theeliminator represents a better measure of noise emissionfor the purposes of ensuring comparability betweendifferen
14、t cooling towers and reproducibility of the testresults, than the sound power emerging directly throughthe air outlet. The measurement surface and the measuringpoints shell therefore be arranged above the eliminatorplate as shown in figure 3.Note. In the case of wet natural-draught cooling towers,th
15、e A-weighted partial sound power level at theair outlet is approximately (0,14H) dB lowerthan the A-weighted partial sound power leveldetermined by the method specified in thisstandard for the plane above the water distribu tion system, with H in m. This approximationdoes not take account of weather
16、-dependentfluctuations. Because of the directivity charac teristic of the radiation, the A-weighted partialsound power level so estimated for the air outletcannotautomatically be regarded as the A-weightedimmision-relevant sound power level.1) In some cases, cold operation is adequate for noisemeasu
17、rement if it can be taken from preliminaryinvestigations that the effect of the cooling power onthe test results is less than 1 dB. In such a case, a noteto this effect shall be included in the test report.Measurement surface for suction opening No.1,measurement surface area 81 equal to a . b + (2a
18、+ b) . cb1m-+- Measurement surface above air outlet, with. . -measurement surface area 83 equal to 2 1t r2A4 measuring points arranged on the circumference for. “, 83 (70il80)Measurement surface above fan casing, withmeasurement surface area 85equal to 2 n: r h2(4 measuring points arranged in each o
19、f three1m: measurement planes)For measurement surface for fan motor andmeasurement surface 84, see DIN 45635 Part 1, Section A-BApril 1984 edition, figure A.l.l2. l2. b4 4 I;Measurement surface for air inlet No.2,measurement surface area 82 equal to 81DiffuserFigure 2. Measurement surfaces and measu
20、ring points for a cell cooling tower with mechanical draught (the arrangementfor a natural draught cooling tower is similar, except for the measurement surface for the fan motor)DIN 45635 Part 46 Page 3Air outletWater distributionsystem and eliminatorwith catwalk2Erj E: ;jLJ1._-.- n- _-,L _ _ JMeasu
21、rement surface abovewater distribution system, withmeasurement surface area81equal to 1t Iff. 4 measuring points evenlydistributed along any straightline through the centre of thecircular measurement surfaceESound baffles 1mMeasurement surface for cooling tower with suctionopening provided with soun
22、d baffles, on which 9 meas uring points are arranged: 3 measuring points at each level, spaced 1200apart,measurement surface area 82 equal to 21t r2 (82 + C2)Measurement surface for cooling tower with suctionopening without sound baffles, on which 9 measuringpoints are arranged:0,6 3 measuring point
23、s at each level, spaced 1200apart,measurement surface 82 equal to 21tr1 (8, + C1 )Note. If the three measuring points 6 are difficult to reach (e.g. if 81 exceeds 10m), they may be omitted. In such cases,c1 =0 shall be used in the above formula.Figure 3. Measurement surfaces and measuring points for
24、 a natural draught cooling tower5.5 Test environmentAs specified in DIN 45635 Part 1 (grade 3 accuracy).Because cooling towers are normally of large dimensions,the measurements shall be carried out on site in the openair, except for small cooling towers on which measure ments may be taken indoors. I
25、n such cases, the notesregarding the environmental correction and the back ground noise correction as given in DIN 45635 Part 1shall be particularly taken into account.6 Test procedureThe cooling air velocity and the wind velocity at themeasuring points shall not exceed 5 m/s. With higherspeeds, if
26、necessary, a new measurement surface shall beselected at a greater distance from the object under test.Measurements made inside a natural draught coolingtower shall be carried out with a windscreen in front ofthe microphone.6.1 Measuring the A-weighted sound pressure levelThe weighted sound pressure
27、 level, LpA ,shall be meas ured as described in DIN 45635 Part 1. The measurementshall be such as to yield the A-weighted sound pressurelevel averaged over time as specified in DIN 45641 foreach measuring point; the averaging shall extend over atest period of at least 5 s.6.2 Measuring the sound pre
28、ssure spectrumThe sound pressure spectrum shall be determined, accord ing to requirements, as specified in subclause 6.1 inoctave or one-third octave bands, but without weighting,at one or more measuring points.6.3 Measuring the background noise levelThe background noise level,LAshall be measured as
29、described in DIN 45635 Part 1.Page 4 DIN 45 635 Part 466.4 Determining the measurement surface area and themeasurement surface ratioThe measurement surface area, 8, and the measurementsurface ratio, Ls, shall be determined as described inDIN 45635 Part 1.9 Test reportThe test report shall give the d
30、esignation of the methodand the details specified in subclauses 9.1 to 9.5.9.1 Family and description of cooling tower under test.9.4 Instrumentation used.92 Data, conditions of erection and operation ofcooling tower.9.3 Description of test location, arrangement of coolingtower, position of measurin
31、g points (drawing),(1)52Ls2=10Ig-dBSoFrom the measurement surface areas 81 to 85shown infigure 2, or, in the case of natural draught cooling towers,from the measurement surface areas 81 and 82 shown infigure 3, the measurement surface ratios shall be deter mined as follows:51LS1= 10lg -dB,Sowhere 80
32、 shall be taken as 1 m2,with LWA 1, LWA2. , in dB7 EvaluationAs described in DIN 45635 Part 1.The appropriate partial measurement surface soundpressure levels shall be determined separately from theA-weighted sound pressure levels measured at themeasuring points on the partial measurement surfaces.F
33、or each partial measurement surface, from the asso ciated measurement surface ratio and measurementsurface sound pressure level, the A-weighted partialsound power level shall be calculated and stated sepa rately.The various partial sound power levels can be aggregatedto give the total sound power le
34、vel as specified inDIN 45635 Part 1, April 1984 edition, Appendix F:LWAges = 10 19 (100,1 LWA 1 + 100,1 LWA2 + .)dB(2)8 Precision and uncertainty ofmeasurement resultsWhen the A-weighted sound power level is determinedby the method specified in this standard (without repeatmeasurements) a (two-sided
35、) uncertainty of about 3 dBmay be assumed (see DIN 45635 Part 1, clause 8).9.5 Measured values and measurement results, such asa) A-weighted sound pressure level,L;A;bl where applicable, background noise level,LA;c) where applicable, environmental correction,K2;d) surface sound pressure level, LpA,
36、for each partialsound source;e) measurement surface ratio,Ls, for each partial soundsource;f) A-weighted sound power level, LWA for each partialsound source and, where appliable, the A-weightedtotal sound power level,LwAgeS;g) where applicable, the octave or one-third octave bandsound pressure spect
37、ra at selected measuring points.10 Report on resultsThe report on results shall give the following details:a) designation of method as in clause 2;b) place, date and person responsible for the test;c) information as in subclause 9.1 ;d) A-weighted sound power level for each partial soundsource and,
38、where applicable, the A-weighted totalsound power level;e) where applicable, octave or one-third octave soundpressure spectrum at selected measuring points.Standards referred toDIN 45635 Part 1 Measurement of noise emitted by machines; airborne noise emission; enveloping surface method;basic method, divided into 3 grades of accuracySupplement 2 toDIN 45635DIN 45641Measurement of noise emitted by machines; explanatory notes on noise emission parametersAveraged levels and rating levels of sound varying with timeInternational Patent ClassificationG 01 H 1/00E04H5/12
