ASHRAE Standard 41.8 2016 RA2019
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ASHRAE Standard 41.8-2016 (RA 2019) – Standard Methods for Liquid Flow Measurement (ANSI Approved)
| Published By | Publication Date | Number of Pages |
| ASHRAE | 2019 | 28 |
Standard 41.8 prescribes methods for liquid flow measurement and applies to laboratory and field liquid flow measurement for testing heating, ventilating, air-conditioning, and refrigerating systems and components.In the 2016 edition of Standard 41.8, the scope was expanded to cover the breadth of liquid flow measurement devices used for testing HVAC&R systems and components, except for refrigerant liquid flow measurement devices, which are the focus of ASHRAE Standard 41.10.This 2019 reaffirmation of the 2016 edition of Standard 41.8 includes no changes.
PDF Catalog
| PDF Pages | PDF Title |
|---|---|
| 1 | ANSI/ASHRAE Standard 41.8-2016 (RA 2019) |
| 3 | CONTENTS |
| 4 | FOREWORD 1. PURPOSE 2. SCOPE 3. DEFINITIONS 4. CLASSIFICATIONS 4.1 Liquid Flow Operating State. As stated in Section 2, the entire flow stream of liquid entering and exiting the flowmeter shall be in a liquid-only state during liquid flow data recording. Verify that the total pressure is greater than the vapor p… 4.2 Liquid Flow Measurement Applications. Liquid flow measurement applications that are within the scope of this standard shall be classified as one of the types described in Sections 4.2.1 and 4.2.2. 4.3 Liquid Flowmeter Categories |
| 5 | 4.4 Liquid Flow Measurement Methods. Liquid flow measurement methods that are within the scope of this standard are the methods listed below. Each of these liquid flow measurement methods are described in Section 7.5. 5. REQUIREMENTS TABLE 5-1 Measurement Values and Units of Measure 5.1 Test Plan. A test plan is required. The test plan shall specify the test points and the required measurement system accuracy at each test point. A test plan is a document or other form of communication that specifies the tests to be performed and… 5.2 Values to Be Determined and Reported. The test values to be determined and reported shall be as shown in Table 5-1. Use the unit of measure in Table 5-1 unless otherwise specified in the test plan in Section 5.1. 5.3 Test Requirements 6. INSTRUMENTS 6.1 Instrumentation Requirements for All Measurements |
| 6 | 6.2 Temperature Measurements. If temperature measurements are required by the test plan in Section 5.1, the measurement system accuracy shall be within the following limits unless otherwise specified in the test plan: 6.3 Pressure Measurements 6.4 Time Measurements. Time measurement system accuracy shall be within ±0.5% of the elapsed time measured, including any uncertainty associated with starting and stopping the time measurement unless (a) otherwise specified in the test plan in Secti… 6.5 Mass Measurements. If mass measurements are required by the test plan in Section 5.1, the measurement system accuracy shall be within ±0.2% of the reading unless otherwise specified in the test plan. 7. LIQUID FLOW MEASUREMENT METHODS 7.1 Liquid Properties. If not specified in the test plan in Section 5.1, the source of the liquid property data shall be recorded in the test report. 7.2 Operating Limits. Operating conditions during liquid flow data measurements shall not exceed limits for liquid velocity, temperature, pressure, pressure differential, or pressure pulsations specified in the test plan in Section 5.1 or by the liqu… 7.3 Leakage Requirement. Unless otherwise specified in the test plan in Section 5.1, there shall be no liquid leakage out of the test apparatus. 7.4 Liquid Flowmeter Installation. The selected liquid flowmeter shall be installed in accordance with instructions from the manufacturer, or the uncertainty calculations shall include estimated uncertainties for installations that are not in accorda… 7.5 Liquid Flowmeter Descriptions |
| 7 | FIGURE 7-1 Orifice section of an orifice flowmeter. (Reprinted with permission of ASME) |
| 8 | FIGURE 7-2 Examples of flow nozzles used in nozzle flowmeters. (Reprinted with permission of ASME) |
| 9 | FIGURE 7-3 Geometric requirements for Venturi tube flowmeters. (Reprinted with permission of ASME) |
| 10 | TABLE 7-1 References in ASME MFC-3M 4,5 for ISA 1932 Nozzles, Venturi Nozzles, and Venturi Tubes |
| 11 | FIGURE 7-4 Variable-area flowmeter. |
| 12 | FIGURE 7-5 Example of a pitot-static tube. |
| 13 | FIGURE 7-6 Pitot-tube traverse measuring points. |
| 14 | 8. UNCERTAINTY REQUIREMENTS 8.1 An estimate of the measurement uncertainty, performed in accordance with ASME PTC 19.1 6, shall accompany each liquid flow measurement. Installation effects on the accuracy of the instrument shall be included in the uncertainty estimate for each … 8.2 Method to Express Uncertainty. All assumptions, parameters, and calculations used in estimating uncertainty shall be clearly documented prior to expressing any uncertainty values. Uncertainty shall be expressed as follows: 9. TEST REPORT 9.1 Test Identification 9.2 Liquid Flow Measurement System Description 9.3 Ambient Test Conditions 9.4 Test Operating Conditions if Required by the Flowmeter |
| 15 | 9.5 Test Results 10. REFERENCES |
| 16 | INFORMATIVE ANNEX A: INFORMATIVE REFERENCES AND BIBLIOGRAPHY |
| 17 | INFORMATIVE ANNEX B: AN UNCERTAINTY ANALYSIS EXAMPLE FOR A CORIOLIS FLOWMETER B1. Define the Measurement Process B1.1 Review the Test Objectives and Duration. The test objectives are clearly stated in the description above. B1.2 List All Independent Measurement Parameters and Their Nominal Levels. The only independent measurement is the frequency output from the Coriolis flowmeter. The full- scale output of the flowmeter was set by the manufacturer to 4.0 kg/s (8.82 lbm… B1.3 List All Calibrations and Instrumentation Setups that Will Effect Each Parameter. The manufacturer verified basic flowmeter operation on its test facility that has a stated uncertainty (URSS) of ±0.05% per ISO 5168 A11. The calibration data pro… B1.4 Define the Functional Relationship between the Independent Measurement Parameters and the Test Results. As the mass flow is a direct measurement, there is no functional relationship between multiple measurements and the final test result. B2. List Elemental Error Sources B2.1 Make a Complete List of All Possible Measurement Error Sources. The number of possible error sources for this system is small due to the simplicity of the overall system. Measurement error sources may include the manufacturer’s calibration res… B2.2 Group the Error Sources According to the Following Categories B3. Estimate Elemental Errors B3.1 Obtain an estimate of each error identified in Section B2.2(b). B3.2 If data are available to estimate the precision index, tentatively classify the error as a precision error. Otherwise, classify it as a bias error. |
| 18 | TABLE B-1 Manufacturer’s Initial Liquid Flowmeter Calibration Data FIGURE B-1 Flow error vs. flow rate. TABLE B-2 Error Estimates as a Function of Flow Rates |
| 19 | TABLE B-3 Data Reduction Curve Fit Error Comparison TABLE B-4 Bias and Precision Error Summary |
| 20 | TABLE B-5 Propagation and Final Uncertainty Estimate B3.3 Calculate the Bias and Precision Errors for Each Parameter. The results from the previously defined elements are summarized at each of the four calibrated flow rates in Table B-4. The summing of the terms is by the root-sum- square method, as a … B4. Propagate the Bias and Precision Errors B4.1 The bias and precision errors of the independent parameters are propagated separately all the way to the final test result. The individual terms are now summed together again by the root-sum-square method, as a 95% confidence level is desired as… B4.2 Error propagation is performed, according to the functional relationship of Section B1.4, via a Taylor series. This requires a calculation of the sensitivity factors, either by differentiation or by computer perturbation. As the mass flow rate i… B5. Calculate Uncertainty B6. Report B6.1 The report summary shall contain the nominal level of the test result, bias limit, precision index, degrees of freedom, and uncertainty of the test result, stating the model used. B6.2 The report shall include a table of the elemental errors included in the uncertainty analysis along with the bias limit, precision index, and degrees of freedom of each parameter. The report for this analysis would include the average value dete… |
| 21 | INFORMATIVE ANNEX C: AN UNCERTAINTY ANALYSIS EXAMPLE FOR A DIFFERENTIAL PRESSURE FLOWMETER C1. Identify experimental goals and acceptable accuracy C2. Identify the important variables and appropriate relationships C3. Establish the quantities that must be measured and their expected range of variation C4. Tentatively select sensors/ instrumentation appropriate for the task C5. Document uncertainty of each Measured variable C6. Perform a preliminary uncertainty analysis C6.1 Calculate the Bias and Precision Errors for Each Parameter. The estimates from the previously defined elements in Table C-3 are now summarized for each elemental term using the root-sum-square method, as 95% confidence is desired. The degrees of… |
| 22 | TABLE C-1 Independent Parameters Descriptions TABLE C-2 Relationship of the Calculated Parameters |
| 23 | TABLE C-3 Uncertainty of Each Measured Parameter |
| 24 | TABLE C-4 Calculated Density at Minimum, Nominal, and Maximum Temperature and Pressure C6.2 Propagate the Bias and Precision Errors. The individual parameter errors are propagated into the flow rate according to a Taylor series expansion. The relative bias limit for the mass flow equation is as follows: C7. Study uncertainty results and reassess the ability of the measurement methods and instrumentation to meet acceptable accuracy C8. Install selected instrumentation in accord with relevant standards or best practices |
| 25 | TABLE C-5 Summary of Calculations C9. Perform initial verification of data quality C10. Collect experimental data subject to ongoing quality control criteria C11. Accomplish data reduction and analysis C12. Perform final uncertainty analysis C13. Report experimental results |
| 26 | INFORMATIVE ANNEX D: INFORMATION REGARDING LIQUID FLOW MEASUREMENT UNCERTAINTIES FOR INSTALLATIONS THAT DO NOT MEET THE FLOWMETER MANUFACTURER’S REQUIREMENTS D1. Introduction D2. Previous Research Results and Technical Papers D2.1 Technical Paper: Flowmeter Installation Effects— Wild Claims, Bright Ideas, and Stark Realities. The authors of this 1995 paper describe an eight-year project sponsored by a NIST-industry consortium that addressed the pipe flow distortions pro… D2.2 Laser Doppler Velocimeter Studies of the Pipe Flow Produced by a Generic Header. This 1995 paper reported Laser Doppler Velocimeter measurements for the pipe flows produced downstream of a header with and without a conventional 19-tube concentri… D2.3 Effects of a Conventional 45-degree Elbow. This report describes the effects of a conventional 45-degree elbow and includes discussion regarding a 19-tube and 7-tube concentric tube bundle flow conditioner. D2.4 Pipe Elbow Effects on the V-Cone Flowmeter. This 1993 paper presents installation effects on a special type of flowmeter with baseline comparisons to orifice plate differential pressure flowmeters. |
