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ASHRAE Standard25 2018

ASHRAE Standard25 2018

$38.46

ASHRAE Standard 25-2018 – Methods of Testing Forced-Circulation Free-Delivery Unit Coolers for Refrigeration (ANSI Approved)

Published By Publication Date Number of Pages
ASHRAE 2018 28
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Standard 25 establishes uniform methods of testing for obtaining performance data, lists and defines the terms used in testing, specifies data to be recorded and formulas to be used in calculations, and sets limits and tolerances in testing.The 2018 edition of ASHRAE Standard 25 incorporates technical revisions, including new requirements for glide refrigerants, and includes online access to supporting files for calculating the effect of temperature glide onto the average evaporation temperature.

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PDF Pages PDF Title
1 ANSI/ASHRAE Standard 25-2018
3 CONTENTS
4 1. PURPOSE
2. SCOPE
3. DEFINITIONS AND SYMBOLS
3.1 Definitions
5 3.2 Symbols
6 3.3 Subscripts
4. TEST REQUIREMENTS
4.1 Appurtenances. Unit coolers shall be factory made and furnished with all appurtenances that affect thermal performance and energy consumption.
4.2 Refrigerant. The refrigerant used during the test shall be recorded on the test report.
7 Table 1 Instrumentation Accuracy
4.3 Instrumentation. Instruments shall comply with the accuracy requirements in Table 1.
8 Table 2 Test Condition Tolerances
4.4 Calibration. Measurements from the instruments shall be traceable to primary or secondary standards calibrated by National Institute of Standards and Technology (NIST) or to the Bureau International des Poids et Mesures (BIPM) if a National Metro…
4.5 Test Chamber Dimensions. The unit cooler shall be installed in a room of sufficient size to avoid airflow restrictions or recirculation such that the following apply:
4.6 Test Condition Tolerances. Test acceptance criteria listed in Tables 2, 3, and 4 apply to all methods of test.
5. TEST INFORMATION
5.1 Measurement Intervals. Measurement intervals shall be in accordance with Table 4.
5.2 Test Data. The following data shall be recorded, where applicable, for each unit tested, including the units of measurement used.
9 Table 3 Refrigerant Temperature Tolerances
Table 4 Required Test Measurement Intervals
10 6. METHODS OF TESTING
6.1 DX Dual Instrumentation (Method 1)
6.2 DX Calibrated Box Test Procedure (Method 2)
Figure 1 Illustrative Method 1 setup.
11 Figure 2 Illustrative Method 2 setup.
12 Figure 3 Illustrative Method 3 setup.
6.3 Liquid Overfeed Test Procedure (Method 3)
13 7. CALCULATIONS
7.1 To calculate average measured power (all methods), use Equation 7-1:
7.2 Average Measured Temperatures
7.3 Average Measured Pressures
7.4 Average Air Density. Determine the test air density rtest (lbm/ft3[kg/m3]) using dry-bulb temperature Tdb (°F [°C]), barometric pressure Pb (in. Hg [kPa]), and wet-bulb temperature Twb (°F [°C]) by referencing the ASHRAE Psychrometric Analysi…
7.5 Calculated Saturation Temperatures. Thermophysical properties are to be determined from the current version of NIST Reference Fluid Thermodynamic and Transport Properties Database (REFPROP) 1 or from a reference that provides compliant properties…
14 7.6 Liquid subcooling entering expansion valve (all methods), use Equation 7-12.
7.7 Vapor superheat leaving unit cooler (Methods 1, 2), use Equation 7-13.
7.8 Enthalpies
7.9 Temperature Difference Calculation
7.10 To calculate Enthalpy Difference of air (Methods 1, 3), use Equation 7-16.
8. NORMATIVE REFERENCES
9. INFORMATIVE REFERENCES
15 NORMATIVE APPENDIX A: CALCULATION OF MEAN EVAPORATION TEMPERATURE
A1. Methods 1 and 2—Direct Expansion
A2. Method 3—Liquid Overfeed Operation
Table A-1 Symbols
16 Table A-2 Saturation Pressure for Tables 2 and 3 (I-P)
Table A-3 Saturation Pressure for Tables 2 and 3 (SI)
17 Table A-4 Offsets (t01 – ), Methods 1 and 2 (Direct Expansion) (I-P)
Table A-5 Offsets (t01 – ), Methods 1 and 2 (Direct Expansion) (SI)
18 Table A-6 Offsets (t0,m – ), Method 3 (Liquid Overfeed, Recirculation Ratio = 1) (I–P)
Table A-7 Offsets (t0,m – ), Method 3 (Liquid Overfeed, Recirculation Ratio = 2) (I–P)
19 Table A-8 Offsets (t0,m – ), Method 3 (Liquid Overfeed, Recirculation Ratio = 5) (I–P)
Table A-9 Offsets (t0,m – ), Method 3 (Liquid Overfeed, Recirculation Ratio = 10) (I–P)
20 Table A-10 Offsets (t0,m – ), Method 3 (Liquid Overfeed, Recirculation Ratio = 1) (SI)
Table A-11 Offsets (t0,m – ), Method 3 (Liquid Overfeed, Recirculation Ratio = 2) (SI)
21 Table A-12 Offsets (t0,m – ), Method 3 (Liquid Overfeed, Recirculation Ratio = 5) (SI)
Table A-13 Offsets (t0,m – ), Method 3 (Liquid Overfeed, Recirculation Ratio = 10) (SI)
22 Figure A-1 Direct-expansion cycle.
Figure A-2 Liquid overfeed process.
23 INFORMATIVE APPENDIX B: CAPACITY EQUATIONS
B1. Capacity Calculations for each method
B1.1 Temperature Correction Factor
B1.2 Air Enthalpy Correction Factor
B1.3 Gross Total Cooling Effect (Method 1)
B1.4 Gross Total Cooling Effect—Dry Condition only (Method 2)
B1.5 Gross Total Cooling Effect Calculation (Method 3)
25 Table B-1 Symbols

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