1、ASHRAE STANDARDANSI/ASHRAE Standard 28-1996 (RA 2010)(Reaffirmation of ANSI/ASHRAE Standard 28-1996 RA 2006)Methods of Testing Flow Capacity of Refrigerant Capillary Tu b e sApproved by the ASHRAE Standards Committee on June 21, 1996, and reaffirmed on January 23, 2010.Approved by the ASHRAE Board o
2、f Directors on June 27, 1996, and reaffirmed on January 27, 2010.Approved by the American National Standards Institute on September 6, 1996, and reaffirmed on January 28,2010. ASHRAE Standards are scheduled to be updated on a five-year cycle; the date following the standard numberis the year of ASHR
3、AE Board of Directors approval. The latest edition of an ASHRAE Standard may be pur-chased on the ASHRAE Web site (www.ashrae.org) or from ASHRAE Customer Service, 1791 Tullie Circle,NE, Atlanta, GA 30329-2305. E-mail: ordersashrae.org. Fax: 404-321-5478. Telephone: 404-636-8400(worldwide) or toll f
4、ree 1-800-527-4723 (for orders in US and Canada). For reprint permission, go towww.ashrae.org/permissions. Copyright 2010 American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.ISSN 1041-2336American Society of Heating, Refrigeratingand Air-Conditioning Engineers, Inc.1791 Tu
5、llie Circle NE, Atlanta, GA 30329www.ashrae.orgASHRAE STANDARDS COMMITTEE 20092010Steven T. Bushby, ChairH. Michael Newman, Vice-ChairRobert G. BakerMichael F. BedaHoy R. Bohanon, Jr.Kenneth W. CooperK. William DeanMartin DieryckxAllan B. FraserKatherine G. HammackNadar R. JayaramanByron W. JonesJay
6、 A. KohlerCarol E. MarriottMerle F. McBrideFrank MyersJanice C. PetersonDouglas T. ReindlLawrence J. SchoenBoggarm S. SettyBodh R. SubherwalJames R. TaubyJames K. VallortWilliam F. WalterMichael W. WoodfordCraig P. WrayWayne R. Reedy, BOD ExOThomas E. Watson, COStephanie Reiniche, Manager of Standar
7、dsSPECIAL 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 StandardsInstitute (ANSI), of which ASHR
8、AE 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 views and objections be co
9、nsidered, 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 members, associated societies
10、, 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 be technically qualifi
11、ed in the subject area of the Standard. Every effort is made to balance the concerned interests on all ProjectCommittees. The Manager of Standards of ASHRAE should be contacted for:a. interpretation of the contents of this Standard,b. participation in the next review of the Standard,c. offering cons
12、tructive 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 information andaccepted industry practices. However, ASHRAE does not gu
13、arantee, 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 Guidelines will be nonhazardous or free from risk.ASHRAE INDUSTRIAL ADVERTI
14、SING 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 equipment, by providing proper definitions of this equipment, and by providin
15、gother 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 and in marking of equipment and in advertising, no claim shall be mad
16、e, either stated or implied,that the product has been approved by ASHRAE.ASHRAE Standing Standard Project Committee 28Cognizant TC: TC 8.8, Refrigerant System Controls and AccessoriesSPLS Liaison: William E. Murphy*Denotes members of voting status when the document was approved for publicationPiotr
17、A. Domanski, Chair* Thompson J. Matambo*Byron R. Horak, Secretary* Michael B.Pate*Chinmoy Banerjee Roberto Pereira*Robert L. Cushman* Clyde Wayne Siltanen*William H. Mapes, III* R. Eddie Stanton* American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). For pe
18、rsonal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAEs prior written permission.CONTENTSANSI/ASHRAE Standard 28-1996 (RA 2010)Methods of Testing Flow Capacity of Refrigerant Capillary TubesSECTION PAGEForeword. 21 Purp
19、ose 22 Scope . 23 Definitions. 24 Apparatus for Traditional Method . 25 Test Procedure for Traditional Method . 36 Data to Be Recorded for Traditional Method 37 Correction to Standard Basis for Traditional Method 38 Presentation of Data. 49 Suggestion for Acceptable Variation in Test Results 410 App
20、aratus for Alternative Method . 511 Test Procedure for Alternative Method. 512 Correction to Standard Basis for Alternative Method . 513 References . 6NOTEWhen addenda, errata, or interpretations to this standard have been approved, they can be downloaded free of charge from the ASHRAE Web site at w
21、ww.ashrae.org/technology. Copyright 2010 American Society of Heating,Refrigerating and Air-Conditioning Engineers, Inc.1791 Tullie Circle NEAtlanta, GA 30329www.ashrae.orgAll rights reserved. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). For person
22、al use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAEs prior written permission.2 ANSI/ASHRAE Standard 28-1996 (RA 2010)(This foreword is not part of this standard. It is merelyinformative and does not contain requirements
23、 necessaryfor conformance to the standard. It has not beenprocessed according to the ANSI requirements for astandard and may contain material that has not beensubject to public review or a consensus process.Unresolved objectors on informative material are notoffered the right to appeal at ASHRAE or
24、ANSI.)FOREWORDThis is a reaffirmation of ASHRAE Standard 28-1996(RA 2006). This standard was prepared under the auspicesof the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). It may be used, in wholeor in part, by an association or government agency with duecredit
25、 to ASHRAE. Adherence is strictly on a voluntary basisand merely in the interests of obtaining uniform standardsthroughout the industry. This version updates the referencessection, removes the dates of the references from the body ofthe standard, includes additional verbiage for Section 3 Def-initio
26、n of capillary tube “with length over diameter ratiogreater than 20”, capitalizes the term section and correctsthe I-P units in section 4c and 10d.1. PURPOSEThis standard provides uniform methods for laboratorytesting of the flow capacity of refrigerant capillary tubes. 2. SCOPE2.1 This standard pre
27、scribes two test methods, a traditionalmethod and an alternative method, for determining the flowcapacity of capillary tubes such as are used for refrigerantmetering in refrigeration systems. Both methods use drynitrogen and provide comparable results, but the alternativemethod is more convenient if
28、 electronic devices are used. 2.2 The results obtained by the prescribed procedures areindicative of the refrigerant flow characteristics of the tubebut are not intended to represent the actual refrigerant flowcharacteristics in a refrigerating cycle. 2.3 The scope of this standard does not include
29、specifica-tions of tolerances on tube diameters or nitrogen flow capac-ity; however, acceptable variation in test results is suggested. 3. DEFINITIONScapillary tube: tube of small bore (diameters generally rang-ing down to 0.50 mm 0.02 in. ID with length over diameterratio greater than 20) used for
30、the simultaneous purposes ofmetering the refrigerant and of accomplishing the expansionprocess between condenser and evaporator in those refrigera-tion systems in which it is used.nitrogen capacity: the volumetric flow rate, L/s (cfm), equiv-alent to the mass flow rate of dry nitrogen that would be
31、passedfor a specified inlet pressure if discharge had been to standardatmospheric pressure of 101.325 kPa (14.696 psi) absolute. 4. APPARATUS FOR TRADITIONAL METHODThe arrangement of the traditional test apparatus shall bein accordance with Figure 1. The apparatus is described interms of basic measu
32、rement devices (e.g., thermometers, pres-sure gauges) with the understanding that more sophisticateddevices can be used if they satisfy the required measurementaccuracy specified in this standard.The essential elements of the apparatus are listed below.a. A supply of dry nitrogen (1) at a minimum pr
33、essure of850 kPa gauge (123.3 psig) and a maximum dew point of-32C (-25.6F).b. A filter (2), which will remove any solid or liquid con-taminants that may inadvertently be in the supply lines.c. An adjustable regulator (3) by means of which any testpressure between 15 and 700 kPa gauge (2.2 and 101.5
34、psig) can be maintained steadily (+5% or +7 kPa 1 psi,whichever is smaller) during the test.d. A tempering coil (4) (if necessary) to ensure that thenitrogen entering the test specimen is maintained at theambient temperature of the apparatus, which shall be21C + 3C (70F + 5F).e. A temperature-measur
35、ing instrument (5) with an accuracyof +0.3C (0.5F). Mounting shall ensure that the temper-Figure 1 Test apparatus for determining nitrogen flow capacity of capillary tube (traditional method). Connectingtubes and packing glands shall be sized to ensure negligible pressure drop between the inlet pres
36、sure gauge andthe capillary tube entrance and between the capillary tube exit and the wet-test meter. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). For personal use only. Additional reproduction, distribution, or transmission in either print or dig
37、ital form is not permitted without ASHRAEs prior written permission.ANSI/ASHRAE Standard 28-1996 (RA 2010) 3ature-measuring device is placed in the nitrogen stream toaccurately measure the temperature of the flowing nitro-gen.f. A pressure-gauging instrument (6) for pressures below175 kPa gauge (25.
38、4 psig) with the gauge accuracy of+0.7 kPa (0.10 psi) or better.g. A pressure-gauging instrument (7) with scale divisions of2 kPa (0.29 psi) or better at any pressure between 175 and700 kPa gauge (25.3 and 101.5 psig).h. A leak-free means (8) for connecting the test specimen(9) into the nitrogen str
39、eam. Flow restriction must not beintroduced by the connection.i. A gas flowmeter (10) calibrated to an accuracy of+0.5%. A gas flowmeter of the wet-test type shall beused. It shall incorporate a thermometer (11) and a watermanometer (12) for measuring the temperature and pres-sure of the nitrogen. N
40、ote: Tested flow capacity must be within the flow rangespecified by the wet-test meter manufacturer and within therange for which the meter was calibrated. Calibration may beagainst a precision volume standard or follow the wet-testmeter manufacturers recommendations. j. A barometric device that has
41、 been calibrated in accor-dance with the ASME Power Test Codes, PTC 19.2,Pressure Measurement.1k. A stopwatch, or other suitable timing device, accurate andreadable to 0.1 second.5. TEST PROCEDURE FOR TRADITIONAL METHODThe test procedure, using a wet-test meter for determiningthe nitrogen flow capac
42、ity of the capillary tube specimen, shallbe as follows.5.1 The tube shall be incorporated into the test apparatus,arranged as shown in Figure 1. Unless otherwise dictated bydesign considerations, the tube shall preferably be tested as astraight length. If the limitations of the test apparatus make i
43、tnecessary to coil or bend the specimen, the minimum radiusof bend shall not be less than 300 mm (11.8 in.).5.2 Adjust the ambient temperature of the apparatus and thetempering coil temperature to the specified value of 21C+3C (70F + 5F).5.3 Adjust the inlet pressure to the desired value. The inletp
44、ressure for various lengths and inside diameter shall beselected using Figure 2 as a guide. (Refer to Section 5.7 ifmultipoint nitrogen flow capacities are desired.)5.4 Allow nitrogen to flow through the meter during twocomplete revolutions of the indicator.5.5 Check and adjust as necessary the wate
45、r level in the wet-test meter according to the manufacturers specification.5.6 Each test run shall consist of determining the time (tothe nearest 0.1 second) it takes a predetermined volume ofnitrogen to pass through the wet-test meter.5.7 If multipoint dry nitrogen flow capacities are desired,flow
46、rates shall be determined at additional values of inletpressure as guided by Figure 2.5.8 A laboratory standard capillary tube developed in-houseafter equipment installation and calibration should be kept forsubsequent equipment check.6. DATA TO BE RECORDEDFOR TRADITIONAL METHOD6.1 Record a volume o
47、f not less than 30 L (1.1 ft3) during aperiod of not less than 120 seconds during any test.6.2 Observe the time for four consecutive metered volumesand compute each flow rate.6.3 Record the ambient temperature, the nitrogen tempera-ture at the tube inlet, and the pressure and temperature at thewet-t
48、est meter.Note: All temperature readings should be within the specifiedrange of 21C +3C (70F +5F). Pressure at the wet-testmeter normally is so small it is unreadable. 6.4 Record the barometric reading and the temperature ofthe barometer. Correct the barometric reading for temperatureonly.7. CORRECT
49、ION TO STANDARDBASIS FOR TRADITIONAL METHOD7.1 Average the four rates obtained in section 6.2, then cor-rect the average for the calibration of the wet-test meter (seeSection 4, item (i).Figure 2 Inlet pressures for determining capillarytube flow rate (see Section 5.3). Plot the insidediameter and length of the specimen tube on thegraph. The band within which the point falls shall bethe inlet pressure at which the flow rate is to bedetermined. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). For personal use
