1、ASHRAE STANDARDASHRAE ANSI/ASHRAE Standard 120-2008(Supersedes ANSI/ASHRAE Standard 120-1999)Method of Testing to Determine Flow Resistance of HVAC Ducts and FittingsApproved by the ASHRAE Standards Committee on June 21, 2008; by the ASHRAE Board of Directors onJune 25, 2008; and by the American Nat
2、ional Standards Institute on June 26, 2008. ASHRAE Standards are scheduled to be updated on a five-year cycle; the date following the standard numberis the year of ASHRAE Board of Directors approval. The latest copies may be purchased from ASHRAE Cus-tomer Service, 1791 Tullie Circle, NE, Atlanta, G
3、A 30329-2305. E-mail: ordersashrae.org. Fax: 404-321-5478. Telephone: 404-636-8400 (worldwide) or toll free 1-800-527-4723 (for orders in US and Canada). Copyright 2008 ASHRAEISSN 1041-2336American Society of Heating, Refrigeratingand Air-Conditioning Engineers, Inc.1791 Tullie Circle NE, Atlanta, G
4、A 30329www.ashrae.orgASHRAE STANDARDS COMMITTEE 20072008Stephen D. Kennedy, ChairHugh F. Crowther, Vice-ChairRobert G. BakerMichael F. BedaDonald L. BrandtSteven T. BushbyPaul W. CabotKenneth W. CooperSamuel D. Cummings, Jr.K. William DeanRobert G. DoerrRoger L. HedrickEli P. Howard, IIIFrank E. Jak
5、obNadar R. JayaramanByron W. JonesJay A. KohlerJames D. LutzCarol E. MarriottR. Michael MartinMerle F. McBrideFrank MyersH. Michael NewmanLawrence J. SchoenBodh R. SubherwalJerry W. White, Jr.Bjarne W. Olesen, BOD ExOLynn G. Bellenger, COClaire B. Ramspeck, Assistant Director of Technology for Stand
6、ards and Special ProjectsSPECIAL NOTEThis American National Standard (ANS) is a national voluntary consensus standard developed under the auspices of the AmericanSociety of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). Consensus is defined by the American National StandardsInstitut
7、e (ANSI), of which ASHRAE is a member and which has approved this standard as an ANS, as “substantial agreement reached bydirectly and materially affected interest categories. This signifies the concurrence of more than a simple majority, but not necessarily unanimity.Consensus requires that all vie
8、ws and objections be considered, and that an effort be made toward their resolution.” Compliance with thisstandard is voluntary until and unless a legal jurisdiction makes compliance mandatory through legislation.ASHRAE obtains consensus through participation of its national and international member
9、s, associated societies, and public review.ASHRAE Standards are prepared by a Project Committee appointed specifically for the purpose of writing the Standard. The ProjectCommittee Chair and Vice-Chair must be members of ASHRAE; while other committee members may or may not be ASHRAE members, allmust
10、 be technically qualified in the subject area of the Standard. Every effort is made to balance the concerned interests on all ProjectCommittees. The Assistant Director of Technology for Standards and Special Projects of ASHRAE should be contacted for:a. interpretation of the contents of this Standar
11、d,b. participation in the next review of the Standard,c. offering constructive criticism for improving the Standard, ord. permission to reprint portions of the Standard.DISCLAIMERASHRAE uses its best efforts to promulgate Standards and Guidelines for the benefit of the public in light of available i
12、nformation andaccepted industry practices. However, ASHRAE does not guarantee, certify, or assure the safety or performance of any products, components,or systems tested, installed, or operated in accordance with ASHRAEs Standards or Guidelines or that any tests conducted under itsStandards or Guide
13、lines will be nonhazardous or free from risk.ASHRAE INDUSTRIAL ADVERTISING POLICY ON STANDARDSASHRAE Standards and Guidelines are established to assist industry and the public by offering a uniform method of testing for ratingpurposes, by suggesting safe practices in designing and installing equipme
14、nt, by providing proper definitions of this equipment, and by providingother information that may serve to guide the industry. The creation of ASHRAE Standards and Guidelines is determined by the need for them,and conformance to them is completely voluntary.In referring to this Standard or Guideline
15、 and in marking of equipment and in advertising, no claim shall be made, either stated or implied,that the product has been approved by ASHRAE.ASHRAE Standard Project Committee 120Cognizant TC: TC 5.2, Duct DesignSPLS Liaison: Robert G. Baker*Denotes members of voting status when the document was ap
16、proved for publication.Herman F. Behls, Chair* Kevin J. Gebke*Bass Abushakra* Jason D. King*W. David Bevirt Marvin A. KoerberPatrick J. Brooks* Thomas E. Ponder*Richard A. Evans Gerald W. SadlerClifford D. SmithCONTENTSANSI/ASHRAE Standard 120-2008Method of Testing to Determine Flow Resistance of HV
17、AC Ducts and FittingsSECTION PAGEForeword 21 Purpose 22 Scope . 23 Definitions, Symbols, and Subscripts . 24 Compliance Requirements . 35 Applicability. 36 Instruments. 37 Flow-Measuring Systems and Test Setups 98 Observations and Conduct of Test . 189 Calculations 1910 Test Results and Report. 2311
18、 References . 23Informative Annex A: Error Analysis . 23Informative Annex B: Calibration 24Informative Annex C: Time-Weighted Average. 25 Informative Annex D: Leakage Measurement. 26Informative Annex E: Flexible Duct Test Setup Guide 29Informative Annex F: Example Test Systems. 30Informative Annex G
19、: Tables of Nozzle/Orifice Discharge Coefficients and Expansion Factors 33Informative Annex H: Example Calculations. 37Informative Annex I: Estimating Procedures for Experimental Data . 62Informative Annex J: Bibliography 62NOTEWhen addenda, interpretations, or errata to this standard have been appr
20、oved, they can be downloaded free of charge from the ASHRAE Web site at www.ashrae.org. Copyright 2008 American Society of Heating,Refrigerating and Air-Conditioning Engineers, Inc.1791 Tullie Circle NEAtlanta, GA 30329www.ashrae.orgAll rights reserved.ANSI/ASHRAE STANDARD 120-2008 2(This foreword i
21、s not part of the standard. It is merelyinformative and does not contain requirements necessaryfor conformance to the standard. It has not been pro-cessed according to the ANSI requirements for a stan-dard and may contain material that has not been subjectto public review or a consensus process. Unr
22、esolvedobjectors on informative material are not offered theright to appeal at ASHRAE or ANSI.)FOREWORD First published in 1999, ASHRAE Standard 120 estab-lishes uniform methods of laboratory testing of HVAC ductsand fittings to determine their resistance to airflow. The fittinglosses, which are rep
23、orted as local loss coefficients, are usedto update and refine the ASHRAE Duct Fitting Database. Todate at least six research projects have used the test methodsof Standard 120 to improve this database. This revision of the standard was undertaken primarily tocorrect some errors in the original edit
24、ion of the standard andclarify its language in places. 1. PURPOSEThis standard establishes uniform methods of laboratorytesting of HVAC ducts and fittings to determine their resis-tance to airflow. 2. SCOPE2.1 This standard may be used to determine the change intotal pressure resulting from airflow
25、in HVAC ducts and fit-tings. 2.2 The test results can be used to determine duct flowlosses in pressure loss per unit length. Fitting losses arereported as local loss coefficients. 2.3 This standard does not cover interpretation of test data. 3. DEFINITIONS, SYMBOLS, AND SUBSCRIPTS3.1 Definitions. Re
26、fer to ASHRAE Terminology ofHVAC within the stated uncer-tainty limits, it may be slightly convergent. 6.6.1.4 Ducted Nozzle. The distance between the pipewall and the outside face of the throat for a ducted nozzle shallbe greater than or equal to 3 mm.6.6.1.5 Interior Surface Finish. The surface of
27、 theinner face shall have a roughness of Ra0.075. Values of Ynare given for convenience inTable G-1, Annex G.9.3.1.4 Reynolds Number. The Reynolds number, Red,based on nozzle throat diameter, d, shall be calculated from .(9)The air properties shall be determined as in Section 9.2.Because the nozzle
28、throat velocity, V6, depends on Reynoldsnumber, an approximation must be employed. The nozzleReynolds number can be calculated using nozzle pressuredifferential ps, 5-6. Then, . (10)For a duct, 1/(1-4)0.5= 1.043. For a chamber, is takenas zero; then,.(1)A simplified approximation of Equation 11 suit
29、able forthe range of temperatures from 4C to 40C is Red = 70,900 d. (12)Equation 12 is based on Cn= 0.95, Yn= 0.96, 1/(1-4)0.5= 1.0, and 6 = 1.819 10-5Pas. 9.3.1.5 Discharge Coefficient. The nozzle dischargecoefficient, Cn, shall be determined using otototo topppepbtoto()1500-=opb0.378ppRto273.2+()-
30、=toxoto273.2+tx273.2+-psx1000pb+1000pb-=ps61000pb+ps51000pb+-1ps 56,ps51000pb+-=Yn 1- 2 ()1 1()()1 -1 41 4 2 -12-=ReddV666-=Red1.414Cnd Yn61 4- 5ps 56,=Red1.414Cnd Yn6- 5ps 56,=5ps 56,ANSI/ASHRAE STANDARD 120-2008 20Cn = 0.9965 - 0.00653 . (13)Va lue s of Cnare given for convenience in Table G-2,Ann
31、ex G. The calculation of Cnusing Redis an iterativeprocess using Equations 11 and 13. Use Equation 12 for theinitial calculation of Red. 9.3.1.6 Flow Rate for Ducted Nozzle. The mass flowrate, , at the entrance to a ducted nozzle shall be calculatedfrom .(14)Area, An, is measured at the plane of the
32、 nozzle throat.The volume flow rate, Q5, at the entrance to a ducted nozzleshall be calculated from .(15)9.3.1.7 Flow Rate for Chamber Nozzles. The massflow rate, , at the entrance to a nozzle or multiple nozzleswhen used with a chamber shall be calculated from.(16)The term Cnand area Anmust be dete
33、rmined for eachnozzle and the products summed as indicated. The area Anismeasured at the plane of the nozzle throat. The volume flowrate, Q5, at the entrance to a nozzle or multiple nozzles withchamber approach shall be calculated from .(17)9.3.2 Orifices. For orifices, the test flow rate shall be c
34、al-culated from the pressure differential, ps,5-6, measuredacross an orifice plate. 9.3.2.1 Alpha Ratio. The ratio, , of absolute orificeexit pressure to absolute approach pressure shall be calculatedusing Equation 6.9.3.2.2 Chi Ratio. The chi ratio, , the ratio of the ori-fice static pressure diffe
35、rential to the absolute approach pres-sure, can be calculated from = 1 . (18)9.3.2.3 Beta Ratio. The ratio of orifice diameter, do, tothe duct diameter, D5, is .(19)9.3.2.4 Expansion Factor. The expansion factor, ,for air shall be calculated using the equation Yo= 1 - (0.41 + 0.354) . (20)The specif
36、ic heat ratio for air may be taken as = 1.402.This formula is applicable only if the absolute pressure ratio. Values of Y0are given for convenience in TableG-3. 9.3.2.5 Reynolds Number. The Reynolds number, Re5,based on duct diameter, D5, shall be calculated from (21)9.3.2.6 Discharge Coefficient. T
37、he orifice dischargecoefficient, Co, for D and D/2 taps shall be calculated usingthe equation (22)The orifice discharge coefficient, Co, for flange tape shallbe calculated using the equation(23)The orifice coefficients for D and D/2 taps and for flangetaps are given for convenience in Tables G-4 and
38、 G-5. Thecalculation of Cois an iterative process using Re5with Equa-tions 21 and 22 or 23. Either a trial Coor Re5can be used asthe starting point. 9.3.2.7 Flow Rate. The mass flow rate, , shall be cal-culated using the equation . (24)The volume flow rate shall be calculated from. (25)9.4 Flow Rate
39、 at the Test Specimen. The flow rate at thetest specimen, Qx, shall be obtained by dividing the measuredmass flow rate by the density at the test specimen, x, whereplane x at the test specimen is106Red-msm51.414CnAnYn1 4- 5ps 56,=Q51000m55-=m5m51.414Yn5ps 56, CnAn()=Q51000m55-=doD5-=Y0-p6p5 0.75Re51
40、.801CoAoYoD551 4- 5ps 56.,=Co0.5959 0.03122.10.00292.5 106Re5-0.75+=0.184080.039041 4()- 0 . 0 1 5 8 4 3.+Co0.5959 0.03122.10.00292.5 106Re5-0.75+=0.1840822864D51 4()-856.03D5- .+m5m51.414CoAoYo5ps 56,1 4-=Q51000m55-=21 ANSI/ASHRAE STANDARD 120-2008.(26)9.5 Test Velocity. The test velocity shall be
41、calculated fromthe volume flow rate at the test specimen divided by the areaof the specimen:.(27)9.6 Test Reynolds Number. The Reynolds number at thetest specimen shall be calculated by (28)where the subscript x refers to the appropriate plane. 9.7 Test Velocity Pressure. The velocity pressure at an
42、yplane, x, in the test system shall be calculated by .(29)9.8 Pressure Loss of the Test Specimen at Test Condi-tions. The total pressure loss of a test duct or fitting shall bethe pressure measurement differential as shown on the testsetups (Figures 10 through 19) corrected for (l) the duct pres-sur
43、e losses between the test specimen and the pressure mea-suring stations and (2) density. 9.8.1 Duct Tare Pressure Loss. The pressure loss of theducts between the test specimen and the measuring stationsshall be determined by test in accordance with Section 9.9.5of this standard. A minimum of eight t
44、est points is required,including the extremes of the airflow rate test range. 9.8.2 Conversion to Nominal Density. During a test, theair density may vary slightly from one determination toanother. It may be desirable to convert the results calculatedfor the test conditions to those that would prevai
45、l at nominaldensity. This may be done provided the nominal density, , iswithin 10% of the actual density, x.9.9 Test Specimen Pressure Loss Calculations 9.9.1 Duct-Mounted Entry Fitting. The total pressureloss of a duct-mounted entry fitting shall be calculated by pt,o-2= (ps8+ pv8) - L2-8pf, 2-8(30
46、)where the subscripts refer to planes identified in Figure 10.Ve loc it y press ure , pv8, shall be at the same airflow rate andnominal density as the test fitting. Establish the total pressureloss for duct hydraulic diameter Dh8by test. Remove the fit-ting at Plane 2, add an inlet duct six diameter
47、s in length (min-imum), install a piezometer ring, and determine the duct tarepressure loss, pf, 2-8, in accordance with Section 9.8.1.Determine the single point local loss coefficients by . (31)Using the test data and calculations, determine C as theslope of a linear regression of pv8vs. pt,o-2, forcing thestraight line through the zero-zero intercept. The fitting losscoefficient is calculated by Equation 32, where x is at plane 8and is from
