ashrae~3method of test for measurement of flow gas

7/29/2019 ASHRAE~3Method of Test for Measurement of Flow Gas

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ASHRAE Standing Standard Project Commit tee41.7Cognizant TC: TC 1.2, Ins truments and MeasurementsHarris M. Sullivan, Chair*Dane Kramer, Vice-Chai/*RalphC.Downing*Mack H.Gray, III*

George H. Green*Victor J . J ohnson*Thomas Queitzsch*Henry J . Sauer, J r.*

*Denotes members of voting status when the document was approved for publication

ASHRAE STANDARDS COMMITTEE 1999-2000Arthur E. Mclvor, ChairMarthaJ. Hewett, Vice-ChairDean S. BorgesWaller S. ClementsPiotr A. DomanskiRichard A. EvansMarkC.HegbergJ ohn F.HoganDavid E. KnebelFrederick H. KohlossWilliamJ . LandmanNeil P. Leslie

Name C. owornAmanda K. MeitzDavor NovoselJ osephA. PietschJ ames A. RanfoneTerry E.Townsend

J ames K. VallortThomas E. WatsonBruceA. Wilcox

J . Richard WrightSamuelD. Cummings, J r., BOD E x 0Raymond E. Patenaude, CO

Claire Ramspeck, Manager ofStandardsSPECIAL NOTE

This 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 sdefined by the American National StandardsInstitute (ANSI), of which ASHRAE is a member and which has approved this standard as an ANS, as substantial agreement reachedby directly and materially affected nterest categories.This signifies the concurrence of more than a simple majority, but not necessarilyunanimity. Consensus requires that all views and objections be considered, and that an effort be made toward their resolution.Compliance with this standard is voluntary until and unless a legal urisdiction makes compliance mandatory through legislation.ASHRAE obtains consensus through participation of its national and international members, associated societies, and public.review.ASHRAE Standards are prepared by a Project Committee appointed specifically for the purpose of writing the Standard. TheProject Committee Chair and Vice-Chair must be members of ASHRAE; while other committee members may or may not be ASHRAEmembers, all must be technically qualified in the subject area of the Standard. Every effort is made to balance the concerned interestson all Project Committees.The Managerof Standards of ASHRAE should be contacted for:a. interpretation of the contentsof this Standard,b. participation in the next review of the Standard,c. offering constructive criticism for improving the Standard,d. 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 informationand accepted industry practices. However, ASHRAE does not guarantee, certify, or assure the safety or performance of anyproducts, components, or systems tested, installed, or operated in accordance with ASHRAEs Standards or Guidelines or thatany tests conducted under its Standards or Guidelines will be nonhazardous or free from risk.

ASHRAE INDUSTRIAL ADVERTISING POLICY O N STANDARDSASHRAE Standards and Guidelines are established to assist industry and the public by offering a uniform method oftesting for rating purposes, by suggesting safe practices in designing and installing equipment, by providing proper definitions

ofthisequipment, and by providing other information that may serve to guide the industry. The creation of ASHRAE Standardsand 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 made, eitherstated or implied, that the product has been approved by ASHRAE.

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CONTENTSANSVASHRAE Standard 41.7-1984 (RA 2000),

Method of est for Measurement of Flow of GasSECTION PAGE

1011

Purpose.......................................................................................................................................................... 2Scope ............................................................................................................................................................. 2Definitions ...................................................................................................................................................... 2Classifications .................... ......... ......... ...................... ............. .......,......................................... ..............2Instruments and Apparatus ................ ............................. ........ ... ....................................... ... ......,.......... ...2Measurements .... .. .,............... ...... .................. .... ......... ... ................................ .................................... ... 3Data to be R ecorded ...................................................................................................................................... 3Formulae ........................................................................................................................................................ 6Symbols .......................................................................................................................................................... 7Calculations ........................................................ ................... ........... .......................................................... .9References ..................................................................................................................................................... 9

O Copyright 2000American S ociety of Heating,Refrigerating and Air-Conditioning Engineers, Inc.1791 Tullie Circle NEAtlanta, GA 30329www.ashrae.orgAll rights reserved.

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1. PURPOSE of thermal expansion not exceeding 1.0 x in./in:"F(1.8 x m/(m.K)) and shall have a thickness in accordwith Table 3. The inlet edge of the orifice shall be squareand sharp, free from either burrs or rounding.

The purpose of this standard is to provide recommendedpractices for the measurement of the flow of dry gas for use inthe preparation of ASHRAE standards.2. SCOPE 5.3.2

Orifice plates over 1/8 in. (3 mm ) thick should bebeveled as shown i n Figure 1.

This standard provides flow-measunng techniques for the 5.3.3 The inlet face of the orifice plate shall be flat andshall remain so within 1%of inside pipe diameter adjacent toollowing:

a. volatile refrigerant, gaseous phase; the orifice.b. air under conditions where the methods for flow mea-Surement set forth in Stun-dard fo r LabOratoCY Ai@oware inconvenient or unsatisfactory.

5.3.4 The length of the inlet section in inches should beequal to or greater than the value given in Table 5 as "inlength" for the nominal pipe diameter selected. Interpolationfor intermediate values of B is satisfactory.

3. DEFINITIONS 5.3.5 The length of the outlet section should be 10xDi or3 ft (0.9 m), whichever is greater.o r i f i ce meter: an assembly of a meter tube, an orifice, andpressure taps for connection to a pressure differential measur-ing instrument, such as a manometer, for the flow ratemeasurementof a monophase fluid with known properties.

5.3-6 The orifice diameter shall be measured with the nec-essay accuracy in four equally spaced meridian planes toensure that no single diameter shall differ from the mean bymore than 0.05%.

For other definitions, refer to ASHRAE Terminology of 5,3., The ratio of the orifice diameter Do o orificemeter diameterD i hall not be less than 0.20 nor greater thanVAC&R (ASHRAE 1991).20.70.4. CLASSIFICATIONS

4.1 For the Purpose of this standard7 a gas is classified aswet if greater than 2% of liquid (based On the mass Of dry gasflowing) passes through the measuring device.

5.3.8 The orifice must have a valved drain hole flush withthe bottom of the pipe adjacent to the inlet sideof the onfice.The diameter of the drain hole shall be determined fromTable 2.

4.2 A dry gas is a gas wherein the amount of liquid flowingwith the gas through the measuring device is less than 2% ofthe mass of the gas flowing.

5. INSTRUMENTS AND APPARATUS5.1 Basic Instrument

This standard establishes the flow meter with asquare-edged orifice with flange taps as the basic instrumentfor dry gas flow measurement. Employing this instrument,other instruments, more convenient to use, can be calibrated inthe desired range of use. Flow measurements of unvaryingflows, made in accord with the procedures set forth herein, canbe expected to have a standard error-of-the-mean not exceed-

5.1.1 The square-edged orifice is selected because of itssimplicity, its long established reliability, and the con-venience with which any size can be constructed.

5.1.2 Flange taps are selected despite. the merits of othertap locations because of the assurance with which the locationof taps of this type can be checked.5.2 Meter Tube and Orifice Selection. Follow the proce-dure in 10.1 for the selection of meter tube and onfice dia-meter.

ing 1%.

5.3 Meter5.3.1 The orifice plate can be made of any metal not

corroded by the measured fluid and can have a coefficient

5.3.9 The meter assembly, including the required straightinlet and discharge section, shall be insulated to prevent morethan 2F (1.1 K) change of fluid temperature within theassembly.

5.3.10 The assembly shall be made in accord with Fig-ures 1 and 2.

5.3.11 The inside of 4 in. (100 mm ) and larger pipe (nom-inal size) assembly shall be bored to the diameters and toler-ances shown in Table 4 for a distance of at least 4 pipediameters,Di,receding the orifice and for a distance of atleast 2 pipe diameters beyond the inlet face of the orifice. Thebored portions shall be faired into the unbored pomon at anincluded angle not greater than 30".

+L OW\ \YI'

Figure 1 Orifice detail.

2 ANSVASHRAE STANDARD 41.7-1984 RA 2000)yright ASHRAE

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fLANGE TAPSTO MANOMETER

iet r i c Convers ion1 in . =25.4 m m nR*,l\lFigure 2 Orifice meter section.

5.3.12 The unbored internal surface of the pipe shall bestraight, free from mill scale, pits or holes, reamer scores orrifing, bumps, or other irregularities.

The meter assembly may use Type M copper tube,as indicated in the headings of Tables 1A through 1H.

The center of the orifice shall be concentric withthe axis of the tube or pipe. The flanges shall be recessed andthe orifice plates made to fit the recess to ensure concentricity.

The gasket material shall be stiff rather than soft.Inall cases, the inside diameter of the gasket shall be made largeenough and the gasket so positioned that, when in service, itwill not protrude at any point beyond the inner surface of thepipe.

The pressure tap holes shall be drilled perpen-dicularly to the axis of the pipe; must be free of burrs, wireedges, or irregularities where the holes penetrate the innersurface of the pipe; and must not be over 1/8 in. (3 mm) indiameter. The pressure tap hole must be straight and smoothfor at least 5/8 n. (16 mm) from where it penetrates the innersurface of the pipe.

Tubing connecting the pressure taps with themanometers shall be at least 1/4 in. (6 mm) in inside diameterand shall be pitched at least 1/2 in./ft (0.042 mm) with drainvalves installed at the low points.

5.3.18 Where the vapor entering the meter has fewer than15F (8.3"C) superheat ( t r7 ) ,visual means shall be providedto ensure that saturated liquid is not entrained with the vaporand in no case shall the vapor entering the meter havea super-heat less than 10F (5.6"C).5.4 Meter Installationand Operation.

The conditions under which orifices are instailed mayhave more effect on the accuracyof the test than the degree ofperfection of manufacture or the characteristics of the orificesthemselves. The rate of flow computed from the differentialpressure produced by the orifice may be in error to an unac-ceptable degree if the piping arrangements are such thatdistorted flow conditions result. Distortions of velocity

5.3.135.3.14

5.3.15

5.3.16

5.3.17

traverse, helical swirls, or vortices will all endanger the flowmeasurement accuracy. A projecting gasket, misalignment, ora burr on a pressure tap can cause considerable error. There-fore, the following rules shall be followed carefully.

5.4.1 The orifice shall be located in a pipe or tube selectedin accord with Section 10.

5.4.2 Toensure that the measurement of vapor flow is notinfluenced by entrained liquid particles, steps shall be taken toensure that less than 2% by mass of the vapor flowing is liq-uid.

A satisfactory superheat limit and test for the liq-uid phase of the vapor flowing is given in 5.3.18.

Where there is a possibility of oil or other liquidcirculating with the vapor, separation shall be provided aheadof the meter.

5.4.2.15.4.2.2

6. MEASUREMENTS6.1 Pressure shall be measured with an equal armmercurymanometer. Readings of less than 5 in. (127 mm) column dif-ference shall not be valid.6.2 Column readings shall be made from and checked foraccuracy with a high-grade steel scale marked to 0.05,in.(1 mm), and care in reading shall be used to avoid paral-lax.6.3 Mercury shall be used as the manometer fluid in ailcases where it is compatible with the vapor flowing and wherethe requirement of 6.1 does not force a meter selection thatimposes a permanent pressure loss greater than desired. SeeSection 10 for calculation of permanent pressure loss.6.4 Oil, water, or other manometer fluids may be used underthe exception of 6.3, provided the nonmercury column deflec-tion is compared with a 5 in. (127 mm) deflection of a mer-cury column before and after each test so that the observednonmercury deflections can be converted to inches (mm) ofmercury for flow computation.6.5 If the manometer reading varies, take at least two highdifferential and two low differential readings. Calculate theflow at the high and low differential conditions.6.6 If the flow at low differential is less than 96% of theflow at high differential, discard the runs and take steps to sta-bilize the flow.6.7 If the flow at low differential is greater than 96% of theflow at high differential, average the flows and use the mean.6.8 At least four readings at each flow shall be made. Thestandard deviation of these readings shall not exceed 2% ofthe mean.7. DATA TO B E RECORDED7.1 Initial Data

A. M i c e diameterB. Meter ID (inside diameter)C. Meter identification

ANSUASHRAE STANDARD 41.7-1984 (RA 2wO) 3yright ASHRAE



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-mD

0.2500.3000.3500.4000.4500.5000.5500.6000.6250.6500.6750.700

-

0.3000.350

TABLE 1FlangeTaps*

Values of the Flow Coefficient, K, as a Function of the Pipe Reynolds Number, RD, and Diameter Ratio, For 1-1/2 in . Pipe or 1-5/8OD Type M Copper Tube (40.9 mm to 38.8 mmID) Table IA

1000 I 1500 I 2000 I 2500 I 3000 I 4000 I 5000 I 6000 I 8000 I 10,000 I 15,000 1 20,000 1 25,000 I 50,000 I100,000 1500,000 I lo 60.6142 0.6112 0.6092 0.6068 0.6053 0.6043 0.6030 0.6023 0.6013 0.6008 0.6005 0.5999 0.5996 0.5994 0.5993

0.6113 0.6091 0.60770.6183 0.6155 0.6138

0.6152 0.6126 0.6094 0.6075 0.6062 0.6046 0.6036 0.6023 0.60170.6245 0.6212 0.6170 0.6145 0.6129 0.6108 0.6095 0.6078 0.6070

0.6229 0.6207 0.6179 0.6163 0.6141 0.61300.6342 0.6313 0.6276 0.6254 0.6225 0.62100.6406 0.6376 0.6336 0.6317

0.6577 0.6536 0.6482 0.64560.6675 0.66390.6793 0.6750

0.68760.70180.7177

0.6123 0.6106 0.6085 0.6073 0.6061 0.6055 0.6052 0.6045 0.6039 0.6039

0.60130.60650.61240.62020.63050.64390.66170.67250.68460.69830.7137

0.650

0.60050.60550.61100.61840.62810.64070.65730.66740.67870.69150.7058

0.6845 0.6805 0.6782 0.6737 0.6700 0.6695

0.6001 0.5998 0.59980.6050 0.6046 0.60460.6104 0.6099 0.60980.6175 0.6168 0.61670.6269 0.6259 0.62580.6391 0.6378 0.63760.6551 0.6533 0.65310.6648 0.6628 0.66250.5747 0.6734 0.67310.6881 0.6853 0.68500.7019 0.6987 0.6983

0.6750.700

~ ~

For2 in. Pipe or 2-1/8 OD TvDe M Comer Tube 52.5 mm to 51.0 mm ID

0.6938 0.6911 0.6898 0.6815 0.68090.7091 0.7058 0.6996 0.6946 0.6939

Table 1B

0.450 0.6218 0.6194 0.6182 0.6175 0.6161 0.6150 0.6148

0.60.58 0.6047 0.6032 0.60250.6110 0.6099 0.6089 0.60700.6185 0.6166 0.6142 0.61290.6284 0.6259 0.6225 0.62090.6419 0.6384 0.6339 0.6316

0.6553 0.6490 0.64580.6644

0.750

0.6018 0.6012 0.6007 0.6005 0.60040.6061 0.6053 0.6049 0.6043 0.60420.6117 0.6107 0.6099 0.6095 0.60930.6192 0.6179 0.6169 0.6161 0.61600.6293 0.6275 0.6361 0.6250 0.62490.6426 0.6402 0.6384 0.6368 0.63660.6601 0.6567 0.6541 0.6521 0.65180.6708 0.6668 0.6638 0.6614 0.66110.6828 0.6781 0.5746 0.6718 0.67150.6962 0.6908 0.6868 0.6836 0.6832

0.7461 0.7356 0.7272 0.7262

. .. 1 0.7053 0.7006 0.6968 0.6963For 3 in. PiDe or 3-1/8 OD TvDe M Comer Tube (77.9mm to 75.7 mm ID Table IC

0.3000.3500.4000.4500.5000.5500.6000.625

_ _ *. /F t~ 1 1000 1 2000 I 3000 I 4000 I 5000 I 6000 I 8000 1 10,000 I 15,000 I 20,000 I 30,000 I 40,000 1 50,000 ~100,000)500,000~0.250 I 0.6059 0.6038 0.6025 0.6006 0.5995 0.5989 0.5987 0.5984 0.5979 0.5975 0.5974

lo 6

0.5000.5500.6000.6250.6500.6750.7000.725

0.62% 0.6281 0.6271 0.6251 0.6235 0.62330.6439 0.6413 0.6400 0.6371 0.6350 0.6347

0.6590 0.6569 0.6530 0.6498 0.64940.6698 0.6674 0.6626 0.6588 0.6584

0.6790 0.6735 0.6690 0.66840.6923 0.6857 0.6804 0.67970.7071 0.6994 0.6932 0.69251.7253 0.7163 0.7081 0.7072

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TABLE 1 (Continued)Flange Taps*Values of the Flow Coeffici ent, K, as a Function of the Pipe Reynolds Number, RD, and Diameter Ratio,

0.4000.450

For 6 in. Pipe or 6-1/8OD Type M Copper Tube (154 mm to 149mm D) Table 1EmD I 2000 I 3000 I 4000 I 5000 I 6000 I 8000 I 10,000 I 15,000 I 20,000 I 301000 I 50,000 I 1 0 0 , m I500,OOO I0.250 I 0.6042 0.6020 0.6009 0.5998 0.5990 0.5982 0.5977 0,5976 0.5975

id 1 10

0.6124 0.6107 0.6095 0.6085 0.6083 0.60820.6202 0.6179 0.6161 0.6148 0.6146 0.6144

I0.300 0.6055 0.6041 0.6028 0.6018 0.6012 0.6003 0.6002 0.60010.350 I 0.6087 0.6071 0.6058 0.6048 0.6040 0.6039 0.6038

0.5000.5500.600

0.6276 0.6250 0.6231 0.6228 0.62260.6410 0.6372 0.6343 0,6339 0.63360.6587 0.6533 0.6490 0.6484 0.6481

0.7000.725

0.6250.6500.6750.7000.7250.750

I 0.6982 , 0.6918 0.6897 0.68780.7062 0.7036 0.7014

0.6632 0.6580 0.6573 0.65680.6741 0.6681 0.6673 0.66660.6857 0.6795 0.6786 0.67780.7003 0.6919 0.6908 0.68980.7163 0.7067 0.7053 0.70410.7361 0.7246 0.7231 0.7219

0.7236 0.7205 0.717;0.750Reprinted from ASME Flow MeasurementPTC-19.5.1959,able 4, p. 2023, y p e d s s i o n ofASME.

0.350

ANSVASHRAE STANDARD 41.7-1984 RA 000) 5

0.6073 0.6064 0.6059 0.6051 0.6047 0.6038 0.6037 0.6036

0.5000.5500.600

0.6262 0.6252 0.6229 0.6226 0.62230.6391 0.6376 0.6341 0.6336 0.63320.6561 0.6539 0.6486 0.6480 0.6474

0.6250.6500.6750.7000.725

0.6640 0.6575 0.6567 0.65600.6751 0.6676 0.6667 0.66580.6880 0.6790 0.6779 0.67680.7023 0.6918 0.6904 0.68920.7185 0.7062 0.7046 0.7032

0.4000.450

0.6122 0.6114 0.6102 0.6097 0.6089 0.6084 0.6083 0.60810.6199 0.6187 0.6171 0.6163 0.6152 0.6144 0.6142 0.6140

0.5000.550

0.6268 0.6257 0.6239 0.6229 0.6226 0.62230.6399 0.6381 0.6355 0.6339 0.6334 0.6329

0.6000.6250.6500.675

0.6548 0.6509 0.6486 0.6478 0.64710.6649 0.6602 0.6575 0.6566 0.65570.6766 0.6710 0.6676 0.6665 0.66550.6895 0.6828 0.6788 0.6775 0.6762

0.7000.7250.750

0.6963 0.6915 0.6899 0.68850.7116 0.7060 0.7055 0.70240.7245 0.7213 0.7202 0.719C

0.5000.550

0.6263 0.6241 0.6228 0.6224 0.622C0.6394 0.6361 0.6340 0.6333 0.6327

0.6000.6250.6500.675

0.6518 0.6487 0.6477 0.64680.6615 0.6577 0.6564 0.65530.6722 0.6678 0.6663 0.665C0.6844 0.6790 0.6772 0.6756

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7.2 Flow Data

5.001 to 6.0006.001 to 6.750

A.B.C. Temperature at mercury columnD.E.

Pressureof vapor entering onfice, P6Temperature of vapor entering meterHeight of high manometer legHeight of low manometer leg

TABLE 2Orifice Drain Hole Diameter

~ ~

127 to 152 4.8 3/16152to 171 5.6 1/32

Orifice Hole Diameter

3.501 to 4.125 89 to 105

6.751 to 7.5007.501 to 8.375

RecommendedMaximumDrain Hole Diameter

171to 191 6.4 114191to 213 7.1 9/32

I 4.126 to5.000 I 105 to 127 I 4.0 I 5/32 I

Pipe IDinches Millimetersup to 3 76

Over 3 to 6Over 6 to 8

76 to 150150to 200

Orifice Plate ThicknessInches Millimeters3/32 2.43/16 4.8114 6.4

9.251 to 10.00010.001to 10.875

I 8.376 to 9.250 I 213 to 235 I 7.9 I 5/16 I~

235 to 254 8.7 11/32254 to 276 9.3 318

10.876to 11.62511.626 to 12.50012.501to 13.250

276 to 295 10.3 13/32295 to 318 11.1 7/16318 to 337 11.9 15/32

I 13.251 andlarger I 337andlar~er 12.7 I 112 I Over 8 to 14

For each manometer reading, the foilowing data havealsoE Barometric pressureGH. Temperature at meter inlet

Manometer deflection for a 5 in. (127 mm) deflection of

been measured:Gauge pressure at meter inlet

7.3 Nonmercury Manometer Leg Calibration

200to 360 318 9.5

the mercury column.8. FORMULAE

M (lbh)=35 9 K Do2 Y,Jh-v'"M (kgs)=110K 02 Y m V

RD =6. 3 14 M/DiyMRD =(4/.~)(M/Zljj~) 1.273-iPY=1 - 0.41 +0.35 B4)(xi/k)

h , =0.01605 hoh , =0.001ho

TABLE 3Orifice Plate Thickness

(1)( 1 -SI)

(2)(2-SI)

(3 )(4)

(4-SI)

I I I

TABLE 4Internal Pipe Diameter

8 40 8.033 204 10.005-0.010 d.127-0.25480 7.706 196 20.005 -0.010 I O . 127-0.254

10 40 10.081 256 d.005 -0.010 10.127-0.25480 9.660 245 10.005-0.010 IO . 127-0.254

12 40 12.004 305 10.005-0.015 d. 127 -0.38180 11.488 292 d.005 -0.015 I0.127 -0.381

14 40 13.197 335 10.005-0.020 10.127-0.50880 12.622 32 1 &.O20 10.508

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K1 = m m h ( 5 )

(6)(See Sections 10.1.1, 10.1.2, 10.1.3, 10.1.4, and 10.1.5 forSI.)

Measured Orifice Dia.Measured Meter Tube Dia.=

9. SYMBOLSDiDo = onfice diameter, in. (m)h

= orifce meter tube, inside diameter, in. (m)= height of a column of mercury that will balance a

5 in. (127 mm) column of the manometer fluid to beused

ho = differential height of manometer fluid, in. (mm)

Nominal Pipe Diameter (in.) 1.5 2 3 4 6 8(ID) (Di in.) 1.61 2.067 3.068 4.026 6.065 8.070

h,K1 = orifice selection flow factor computed fromK = orifice flow factor (Table 1)k1112M

= differential height of the manometer converted to in.of water at 68F (m of water at 2OOC)Equation 6

= cdcy, ratio of the specific heats of a gas= higher level of liquid in U manometer, in. (mm)= lower level of liquid in U manometer, in. (mm)= mass flow of vapor, lbh (kg/s), calculated from= mass flow of vapor, lbh (kg/s), estimated

observationsm

10 1410.25 14.14

B =0.4K-Factor 329 543 1800 2060 4670 8380 13,300 25,400Drif. Dia. (in.) 0.644 0.827 1.227 1.610 2.426 3.250 4.100 5.656[niet Length (in.) 34 43 64 85 127 171 215 297Perm Loss Ratio 0.81 0.81 0.81 0.81 0.81 0.81 0.81 0.81B =0.5K-Factor 524 864 1900 3280 7440 13,400 21,300 40,490Orif . Dia. (in.) 0.805 1O34 1.534 2.013 3.033 4.063 5.125 7.070Inlet Length (in.) 38 49 73 97 145 195 246 339Perm Loss Ratio 0.73 0.73 0.73 0.73 0.73 0.73 0.73 0.73B =0.6K-Factor 784 1290 2850 4900 11,100 20,000 31,800 60,400Orif. Dia. (in.) 0.966 1.240 1.841 2.416 3.639 4.875 6.150 8.484Met Length (in.) 43 56 83 109 164 219 277 382PermLoss Ratio 0.63 0.63 0.63 0.63 0.63 0.63 0.63 0.63B =0.7K-Factor 1140 1880 4150 7140 16,200 29,100 46,300 88,100Orif. Dia. (in.) 1.127 1.447 2.148 2.818 4.246 5.688 7.175 9.898Met Length (in.) 48 62 92 121 182 244 308 424Perm Loss Ratio 0.52 0.52 0.52 0.52 0.52 0.52 0.52 0.52

ANSYASHRAE STANDARD 1.7-1984 RA 000) 7yright ASHRAE



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TABLE 5bOrifice Meter Selection Chart (SI)Nominal Pipe Diameter(in.)

(ID) Dimm)1.5 2 3 4 6 8 10 14

40.9 52.5 77.9 102.3 154.1 205.0 260.4 359.2

~

B =0.3K-FactorOrif. Dia. (mm)Inlet Length (m)Perm Loss Ratio

184 303 666 1150 2600 4670 7440 14,20012.27 15.75 23.37 45.92 46.23 61.93 78.11 107.750.737 0.940 1.397 1.829 2.769 3.708 4.699 6.4770.88 0.88 0.88 0.88 0.88 0.88 0.88 0.88

B =0.4K-FactorOrif. Dia. (mm)Inlet Length (m )Perm Loss Ratio

329 543 1800 2060 4670 8380 13,300 25,40016.36 21.01 31.17 40.89 61.62 82.55 104.14 143.660.864 1 O92 1.626 2.159 3.226 4.343 5.461 7.5440.81 0.81 0.81 0.81 0.81 0.81 0.81 0.81

B =0.5K-Factor 524 864 1900 3280 7440 13,400 21,300 40,490Ori f . Dia. (mm) 20.45 26.26 38.96 51.13 77.04 103.20 130.48 179.58Inlet Length (m) 0.965 1.245 1A54 2.464 3.683 4.953 6.248 8.611Perm Loss Ratio 0.73 0.73 0.73 0.73 0.73 0.73 0.73 0.73B =0.6K-Factor 784 1290 2850 4900 11,100 20,000 31,800 60,400Orif. Dia. (mm) 24.54 31.50 46.76 61.37 92.43 123.83 156.21 215.49Inlet Length (m) 1 O92 1.422 2.108 2.769 4.166 5.563 7.036 9.703Perm Loss Ratio 0.63 0.63 0.63 0.63 0.63 0.63 0.63 0.63B =0.7K-Factor 1140 1880 41 50 7140 16,200 29,100 46,300 88,100Orif. Dia. (mm) 28.63 36.75 54.56 71.58 107.85 144.48 182.25 251.41Met Length (m ) 1.219 1.575 2.337 3.073 4.623 6.198 7.823 10.770Perm Loss Ratio 0.52 0.52 0.52 0.52 0.52 0.52 0.52 0.52

= pressure of refrigerant entering onfice, psig (N/m2= absolute pressure at orifice inlet, psia (N/m2)= absolute pressure at orifice outlet, psia (N/m2)

V = specific volume of gas at flowmeter inlet, f?Ab

= ratio of Merentid pressure to absolute inletgauge) (m3/kg>

x1 pressure, Pa -PdPg- -= Reynolds number at orifce inlet= temperature of gas entering meter,"F ("C)= saturation temperatureof gas entering the flowmeter,

OF O C ) (saturation temperature is the temperaturecorresponding to the observed pressure)

= superheat, t A - 6, O F (OC)

YB

= expansion factor (see Equation 3)= ratio of orifke diameter to inside diameter of orifice

meter, DJDiGreek SymbolspP

= dynamic viscosity, centipoises (kg/(m.s))= density of manometer fluid, lb/f? (kg/m3)

ANSVASHRAE STANDARD41.7-1984RA 2000)yright ASHRAE

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Figure3 Orifice selection curve.1O. CALCULATIONS10.1 Selection of Meter and Orifice Size

10.1.1 Estimate the following quantities:(a) The minimum expected mass flow, m , to be mea-(b) The specific volume Vof the vapor in ft3/lb or m3/kg

Using Equation 6 and a mass flow 0.75 of theexpected minimum, calculate Kl,.

Enter Table 5 at B between 0.4 and 0.6 and selectthe column for the nominal pipe diameter where the K-factornearest the K1, factor calculated in 10.1.2 lies. The ID at thetop of the column is the meter inside diameter,D , n inches.

10.1.4 In the same column, drop down to the row for B=0.7 and read the K factor for B = 0.7. This is KlB+,7.Divide K15 determined from Equation 6 by KlB,o.7 andwith the quotient enter Figure 3. On the left read B . Multi-ply the meter diameter determined in 10.1.3 by this value ofB to get the exact orifice diameter.

SI System. To determine the meter diameter andorifice diameter in millimeters, use Table 5B .10.2

sured in lb h or ls

10.1.210.1.3

10.1.5

Calculation of Mass Flow from Manometer Read-Convert manometer readings giving pressure drop

across the orifice in inches (mm) of mercury ( 1 1 - 2) to col-umn heights in inches (mm) of water (using Equation4).

Calculate Y by Equation 3 from B , the ratio of ori-fice diameter and meter ID (consistent units); x1 from the ratioof orifice pressure drop to the absolute pressure of the gas atthe meter inlet (consistent units); and the value ofk =c p /c v orthe gas.

ings10.2.1

10.2.2

10.2.3 Estimate the mass flow m by a trial calculation, anduse this mass flow m and the viscosity p of the gas in centi-poises (kg/(ms)) to calculate the Reynolds number (Equation2 or 2-SI).

10.2.4 With the calculated value of the Reynolds num-ber and B (rounded to an even multiple of OSO ) , enterTables 1A-1H (select the table that corresponds to yourmeter tube size) and read K, he flow coefficient.

10.2.5 Calculate the mass flow for the reading by Equa-tion l .10.3 An estimate of the permanent pressure loss ratio acrossthe meter can be made using the following steps. This cal-culation is important only insofar as the expected permanentloss may affect system operation.

10.3.1 Enter Table 5 with the B for the onfice and meterused and read a value for permanent pressure loss ratio.

10.3.2 Multiply the observed manometer deflection bypermanent pressure loss ratio to get the permanent pressureloss ratio in the same units.

11. REFERENCESANSUASHRAE Standard 41.2-1987(RA 92), Standard

MethodsforLaboratory Airflow Measurement.2ASHRAE Terminology of HVAC&R, 1991.31997 ASHRAE Handbook-Fundamentals, chapter 36,

Principal Properties of Materials.

ANSUASHRAE STANDARD41.7-1984 (RA 2000) 9yright ASHRAE



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POLICY STATEMENT DEFINING ASHRAES CONCERNFOR THE ENVIRONMENTAL IMPACT OF ITS ACTIVITIESASHRAE is concerned with the impact of its members activities on both the indoor and outdoor environment. ASHRAEsmembers will strive to minimize any possible deleterious effect on the indoor and outdoor environment of the systems and

components in their responsibility while maximizing the beneficial effects these systems provide, consistent with acceptedstandards and the practical state of the art.ASHRAEs short-range goal is to ensure that the systems and components within its scope do not impact the indoor andoutdoor environment to a greater extent than specified by the standards and guidelines as established by itself and otherresponsible bodies.As an ongoing goal, ASHRAE will, through its Standards Committee and extensive technical committee structure,continue to generate up-to-date standards and guidelines where appropriate and adopt, recommend, and promote those newand revised standards developed by other responsible organizations.Through its Handbook, appropriate chapters will contain up-to-date standards and design considerations as the material issystematically revised.ASHRAE will take the lead with respect to dissemination of environmental information of its primary interest and will seekout and disseminate information from other responsible organizations that is pertinent, as guides to updating standards andguidelines.The effects of the design and selection of equipment and systems will be considered within the scope of the systemsintended use and expected misuse. The disposal of hazardous materials, if any, will also be considered.ASHRAEs primary concern for environmental impact will be at the site where equipment within ASHRAEs scopeoperates. However, energy source selection and the possible environmental impact due to the energy source and energy

transportation will be considered where possible. Recommendations concerning energy source selection should be made byits members.

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ashrae~3method of test for measurement of flow gas

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