ASHRAE Standard 41.9 2021

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ASHRAE Standard 41.9-2021 — Standard Methods for Refrigerant Mass Flow Measurements Using Caloriemeters (ANSI Approved)

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ASHRAE	2021

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Description

Standard 41.9 prescribes methods for measuring mass flow rates for refrigerants and refrigerant/lubricant mixtures using calorimeters. The 2021 edition is a comprehensive update that includes changes to steady-state criteria and the lubricant circulation rate measurement methods.

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3	CONTENTS
4	FOREWORD 1. PURPOSE 2. SCOPE 2.1 This standard applies to measuring mass flow rates for refrigerants and refrigerant/lubricant mixtures using calorimeters in laboratories. 2.2 This standard applies where the entire flow stream of the refrigerant or the refrigerant/ lubricant mixture enters the calorimeter as a subcooled liquid and leaves as a superheated vapor (evaporator type). 2.3 This standard applies where the entire flow stream of the refrigerant or the refrigerant/ lubricant mixture enters the calorimeter as a superheated vapor and leaves as a subcooled liquid (condenser type). 3. DEFINITIONS
5	4. CLASSIFICATIONS 4.1 Calorimeter Types. Calorimeters that are within the scope of this standard are classified as one of the following types: 5. REQUIREMENTS 5.1 Test Plan. A test plan shall include the test points, targeted set points, and corresponding operating tolerances to be performed. The test plan shall be one of the following options: 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 Refrigerant Mass Flow Rate. Determine the refrigerant mass flow rate, kg/s (lbm/h), through the unit under test using one of the test methods described in Sections 7 through 10 unless otherwise specified in the test plan in Section 5.1. 5.4 Measurement Uncertainty. The uncertainty in each refrigerant mass flow rate measurement, kg/s (lbm/h), shall be estimated using the methods described in Section 12 for each test point unless otherwise specified in the test plan in Section 5.1. Al… 5.5 Lubricant Circulation Rate
6	5.6 Lubricant Sampling Port. A sampling port shall be provided for extracting samples of liquid refrigerant and circulating lubricant for use in determining lubricant circulation rates if required by Section 5.5. 5.7 Steady-State Criteria for Refrigerant Mass Flow Rate Measurements. Refrigerant mass flow rate test data shall be recorded at steady-state test conditions unless otherwise stated in the test plan in Section 5.1. Section 5.8 describes unsteady-stat…
10	5.8 Unsteady-State Refrigerant Mass Flow Rate Measurements. If required by the test plan in Section 5.1, refrigerant mass flow rate test data shall be recorded 5.9 Refrigerant Properties. Refrigerant properties shall be obtained from NIST Reference Fluid Thermodynamic and Transport Properties Database (REFPROP) 1 or from the refrigerant supplier if a constituent of the refrigerant being tested is not includ… 5.10 Input Power. Compressor input power shall be measured in compliance with ASHRAE Standard 41.11 2 if required by the test plan in Section 5.1. 5.11 Safety Requirements. Test apparatus shall be designed in compliance with ASHRAE Standard 15 3. Materials of construction shall be selected based on refrigerant flammability, toxicity, structural strength, rigidity, corrosion resistance, chemical… 6. INSTRUMENTS 6.1 Instrumentation Requirements for All Measurements 6.2 Temperature Measurements. If temperature measurements are required by the test plan in Section 5.1, the temperature measurement system accuracy shall be within the following limits unless otherwise specified in the test plan.
11	6.3 Pressure Measurements 6.4 Coolant Liquid Flow Rate Measurements. If the unit under test (UUT) or the selected calorimeter method includes coolant liquid flow rate measurement, the measurement system errors shall be measured within ±1.0% of reading in laboratory applicati… 6.5 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 Sect… 6.6 Mass Measurements. If mass measurements are required by the test plan in Section 5.1, the measurement system errors shall be within ±0.2% of the reading unless otherwise specified in the test plan. 7. SECONDARY REFRIGERANT CALORIMETER METHOD 7.1 Equipment Description. A secondary refrigerant calorimeter method, shown schematically in Figure 7-1, shall consist of two independent fluid circuits located in heat exchange relationship to each other. The primary refrigerant evaporator coil is … 7.2 Calorimeter Safety Features. The calorimeter shall be equipped with (a) a safety switch that will stop the flow of heat into the secondary refrigerant and (b) a spring-actuated or rupture-disk-type pressure relief valve. The pressure settings for… 7.3 Test Data. Test data to be recorded at each steady-state test condition in compliance with Section 5.7 are as follows:
12	7.4 Heat Leakage. The heat leakage to the surroundings for each calorimeter shall be measured once, and the results shall be applied to all subsequent refrigerant mass flow rate measurements. The heat leakage shall be less than 5% of the heat input t…
13	7.5 Preparations 7.6 Operating Procedures 7.7 Test Condition Tolerances During Data Recording 7.8 Refrigerant Mass Flow Rate Calculations. Refrigerant mass flow rates measured using the secondary refrigerant calorimeter method shall be calculated using Equation 7-3.
14	7.9 Measurement Uncertainty. Measurement uncertainty in the refrigerant mass flow rate measurement shall be estimated using the procedures prescribed in Section 12 as required by Section 5.4. 8. SECONDARY FLUID CALORIMETER METHODS 8.1 Equipment Description. A secondary fluid calorimeter shall consist of two independent fluid circuits located in heat exchange relationship to each other. The refrigerant enters the calorimeter as a subcooled liquid and leaves the calorimeter as a… 8.2 Calorimeter Safety Features. The calorimeter shall be equipped with a safety switch that will stop the flow of heat into the secondary fluid, and a spring-actuated or rupture-disk type pressure relief valve. The pressure settings for the safety s… 8.3 Test Data
15	8.4 Heat Leakage. The heat leakage to the surroundings for each calorimeter shall be measured once, and the results shall be applied to all subsequent refrigerant flow rate measurements. The heat leakage shall be less than 5% of the heat input to the…
17	8.5 Preparations 8.6 Operating Procedures 8.7 Test Condition Tolerances During Data Recording 8.8 Calculations. Refrigerant mass flow rates measured using the secondary fluid method shall be calculated using Equation 8-3a for a single-phase liquid and using Equation 8-3b for a two-phase fluid:
18	8.9 Measurement Uncertainty. Measurement uncertainty in the refrigerant mass flow rate measurement shall be estimated using the procedures prescribed in Section 12 as required by Section 5.4. 9. PRIMARY REFRIGERANT CALORIMETER METHOD 9.1 Equipment Description. The primary refrigerant calorimeter method, shown schematically in Figure 9-1, consists of an arrangement of refrigerant tubes or tubular vessels designed to evaporate the refrigerant flow. Heat input shall be provided by a… 9.2 Calorimeter Safety Features. The calorimeter shall be equipped with a safety switch that will stop the flow of heat input, and a spring-actuated or rupture-disk type pressure relief valve. The pressure settings for the safety switch and the press… 9.3 Test Data. Test data to be recorded at each steady-state test condition in compliance with Section 5.7 are as follows:
19	9.4 Heat Leakage. The heat leakage to the surroundings for each calorimeter shall be measured once, and the results shall be applied to all subsequent refrigerant flow rate measurements. The heat leakage shall be less than 5% of the heat input to the… 9.5 Preparations 9.6 Operating Procedures
20	9.7 Test Condition Tolerances During Data Recording 9.8 Calculations. Refrigerant mass flow rates measured using the primary refrigerant calorimeter method shall be calculated using Equation 9-3. 9.9 Measurement Uncertainty. Measurement uncertainty in the refrigerant mass flow rate measurement shall be estimated using the procedures prescribed in Section 12 as required by Section 5.4. 10. CONDENSER CALORIMETER METHOD 10.1 Equipment Description. The condenser calorimeter method, shown schematically in Figure 10-1, consists of a heat exchanger that is cooled by a single-phase liquid with known transport properties and capable of condensing superheated refrigerant v… 10.2 Calorimeter Safety Features. The calorimeter shall be equipped with a safety switch that will stop the flow of heat into the refrigerant, and a spring-actuated or rupture-disk type pressure relief valve. The pressure settings for the safety swit… 10.3 Test Data. Test data to be recorded at each steady-state test condition in compliance with Section 5.6 are as follows:
21	10.4 Heat Leakage. The heat leakage to the surroundings for each calorimeter shall be measured once, and the results shall be applied to all subsequent refrigerant flow rate measurements. The heat leakage shall be less than 5% of the heat input to th… 10.5 Preparations
22	10.6 Operating Procedures 10.7 Test Condition Tolerances During Data Recording 10.8 Refrigerant Mass Flow Rate Calculations. The refrigerant mass flow rate measured using the condenser calorimeter method shall be calculated using Equation 10-2. 10.9 Measurement Uncertainty. Measurement uncertainty in the refrigerant mass flow rate measurement shall be estimated using the procedures prescribed in Section 12 as required by Section 5.4. 11. LUBRICANT CIRCULATION RATE MEASUREMENTS 11.1 Symbols. Table11-1 defines the symbols used in Section 11. 11.2 Lubricant Circulation Rate Measurement without an Auxiliary Lubricant Separator 11.3 Lubricant Circulation Rate Measurement with an Auxiliary Lubricant Separator
25	12. UNCERTAINTY REQUIREMENTS 12.1 Uncertainty Estimate. An estimate of the measurement uncertainty, performed in accordance with ASME PTC 19.1 8, shall accompany each refrigerant mass flow measurement. 12.2 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: 13. TEST REPORT 13.1 Test Identification 13.2 Unit Under Test Description 13.3 Calorimeter Description and Instrument Descriptions 13.4 Measurement System Description 13.5 Test Conditions 13.6 Test Results
26	14. NORMATIVE REFERENCES
27	INFORMATIVE APPENDIX A: INFORMATIVE REFERENCES AND BIBLIOGRAPHY
28	INFORMATIVE APPENDIX B: FRAMEWORK FOR UNCERTAINTY ANALYSIS FOR A PRIMARY REFRIGERANT CALORIMETER AND A SECONDARY FLUID REFRIGERANT CALORIMETER
32	INFORMATIVE APPENDIX C: EXAMPLE OF UNCERTAINTY ESTIMATE FOR A SECONDARY REFRIGERANT CALORIMETER
35	INFORMATIVE APPENDIX D: EXAMPLE OF UNCERTAINTY ESTIMATE FOR A CONDENSER CALORIMETER D1. Baseline Case
37	D2. Second Case D3. Third Case
40	INFORMATIVE APPENDIX E: SOURCES OF TEMPERATURE MEASUREMENT ERROR

Additional information

Standard Title	ASHRAE Standard 41.9-2021 — Standard Methods for Refrigerant Mass Flow Measurements Using Caloriemeters (ANSI Approved)
Published Code	ASHRAE
Publication Date	2021

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ASHRAE Standard 41.9 2021

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