1、2008 Standard forPerformance Rating ofForced-CirculationFree-Delivery Unit Coolersfor RefrigerationARI Standard 420Copyright Air-Conditioning, Heating and Refrigeration Institute Provided by IHS under license with ARI Not for ResaleNo reproduction or networking permitted without license from IHS-,-,
2、-Copyright 2008, by Air-Conditioning, Heating and Refrigeration Institute Registered United States Patent and Trademark Office Price $10.00 (Members) $20.00 (Non-Members) Printed in U. S.A. IMPORTANT SAFETY DISCLAIMER AHRI does not set safety standards and does not certify or guarantee the safety of
3、 any products, components or systems designed, tested, rated, installed or operated in accordance with this standard/guideline. It is strongly recommended that products be designed, constructed, assembled, installed and operated in accordance with nationally recognized safety standards and code requ
4、irements appropriate for products covered by this standard/guideline. AHRI uses its best efforts to develop standards/guidelines employing state-of-the-art and accepted industry practices. AHRI does not certify or guarantee that any tests conducted under its standards/guidelines will be non-hazardou
5、s or free from risk. Note: This standard supersedes ARI Standard 420-2000. Copyright Air-Conditioning, Heating and Refrigeration Institute Provided by IHS under license with ARI Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-TABLE OF CONTENTS Section 1 Purpose 1 S
6、ection 2 Scope .1 Section 3 Definitions.1 Section 4 Test Requirements 3 Section 5 Rating Requirements .4 Section 6 Minimum Data Requirements for Published Ratings .5 Section 7 Marking and Nameplate Data .5 Section 8 Conformance Conditions 5 TABLES Table 1 Standard Rating Conditions 3 Table 2 Instrum
7、entation Accuracy .4 APPENDICES Appendix A References Normative 6 Appendix B References Informative 6 Appendix C Methods of Testing Forced-Circulation Free-Delivery Unit Coolers for Refrigeration Normative 7 TABLES FOR APPENDICES Table C1 Test Readings 9 Table C2 Additional Test Conditions .11 Table
8、 C3 Test Condition Tolerances 11 Table C4 Refrigerant Temperature Tolerances . 12 Copyright Air-Conditioning, Heating and Refrigeration Institute Provided by IHS under license with ARI Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-FIGURES FOR APPENDICES Figure C1
9、 Method 1: DX Dual Instrumentation .24 Figure C2 Method 2: DX Calibrated Box. 25 Figure C3 Method 3: Liquid Overfeed 26 Copyright Air-Conditioning, Heating and Refrigeration Institute Provided by IHS under license with ARI Not for ResaleNo reproduction or networking permitted without license from IH
10、S-,-,-ARI STANDARD 420-2008 1 PERFORMANCE RATING OF FORCED-CIRCULATION FREE-DELIVERY UNIT COOLERS FOR REFRIGERATION Section 1. Purpose 1.1 Purpose. The purpose of this standard is to establish for Forced-Circulation Free-Delivery Unit Coolers for Refrigeration: definitions; test requirements; rating
11、 requirements; minimum data requirements for Published Ratings; marking and nameplate data; and conformance conditions. 1.1.1 Intent. This standard is intended for the guidance of the industry, including manufacturers, engineers, installers, contractors, and users. 1.1.2 Review and Amendment. This s
12、tandard is subject to review and amendment as technology advances. Section 2. Scope 2.1 Scope. This standard applies to factory-made, Forced-Circulation, Free-Delivery Unit Coolers, as defined in Section 3, operating with a Volatile Refrigerant fed by either direct expansion or liquid overfeed at we
13、t and/or dry conditions. 2.1.1 Exclusions. This standard does not apply to: 2.1.1.1 Air-conditioning units used primarily for comfort cooling for which testing methods are given in other standards. 2.1.1.2 Unit Coolers operating at latent load conditions with Refrigerant Saturation Temperature 32 F
14、0.0 C to prevent frost. 2.1.1.3 Unit Coolers installed in or connected to ductwork. 2.1.1.4 Unit Coolers using zeotropic refrigerants with Glides greater than 2.0 F 1.1 C. 2.1.1.5 Field testing of Unit Coolers. Section 3. Definitions All terms in this document follow the standard industry definition
15、s in the current edition of ASHRAE Terminology of Heating, Ventilation, Air Conditioning and Refrigeration unless otherwise defined in this section. 3.1 Dew Point. Refrigerant vapor saturation temperature at a specified pressure. 3.2 Enthalpy Difference (HD). The difference between the enthalpy of t
16、he air entering the Unit Cooler and the calculated enthalpy of saturated air at the Refrigerant Saturation Temperature at the Unit Cooler outlet, Btu/lb J/kg. 3.3 Forced-Circulation Free-Delivery Unit Coolers (Unit Coolers). A factory-made assembly, including means for forced air circulation and ele
17、ments by which heat is transferred from air to refrigerant without any element external to the cooler imposing air resistance. These may also be referred to as Air Coolers, Cooling Units, Air Units or Evaporators. 3.3.1 Direct Expansion Unit Cooler. A Unit Cooler in which the leaving refrigerant vap
18、or is superheated. 3.3.2 Liquid Overfeed Unit Cooler. A Unit Cooler in which the refrigerant liquid is supplied at a Recirculation Rate greater than 1. 3.4 Glide. The absolute value of the difference between the starting and ending temperatures of a phase-change process (condensation or evaporation)
19、 for a zeotropic refrigerant exclusive of any liquid subcooling or vapor superheating. Copyright Air-Conditioning, Heating and Refrigeration Institute Provided by IHS under license with ARI Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-ARI STANDARD 420-2008 2 3.5
20、 Gross Total Cooling Effect (Cooling Capacity). The heat absorbed by the refrigerant, Btu/h W. This is the sum of the Net Total Cooling Effect and the heat equivalent of the energy required to operate the Unit Cooler. This includes both sensible and latent cooling. 3.6 Net Total Cooling Effect. The
21、refrigeration capacity available for space and product cooling, Btu/h W. It is equal to the Gross Total Cooling Effect less the heat equivalent of energy required to operate the Unit Cooler. This includes both sensible and latent cooling. 3.7 Overfeed Ratio. The mass ratio of liquid to vapor at the
22、outlet of the Liquid Overfeed Unit Cooler. This may also be referred to as overfeed rate. 3.8 Published Rating. A statement of the assigned values of those performance characteristics, under stated Rating Conditions, by which a unit may be chosen to fit its application. These values apply to all uni
23、ts of like nominal size and type (identification) produced by the same manufacturer. The term Published Rating includes the rating of all performance characteristics shown on the unit or published in specifications, advertising or other literature, controlled by the manufacturer, at stated Rating Co
24、nditions. 3.8.1 Application Rating. A rating at conditions other than Standard Rating Conditions. 3.8.2 Standard Rating. A rating at one of the Standard Rating Conditions shown in Table 1 that is an accurate representation of test data. 3.9 Rated Power. 3.9.1 For single phase motors, total fan motor
25、 input power, W or kW. 3.9.2 For polyphase motors, individual fan motor output power, hp kW. 3.10 Rating Conditions. Any set of operating conditions under which a single level of performance results and which causes only that level of performance to occur. 3.10.1 Standard Rating Conditions. Rating C
26、onditions listed in Table 1 that can be used as a basis of comparison for performance characteristics. 3.10.1.1 Dry Rating Condition. Rating Condition where latent cooling is not present. 3.10.1.2 Wet Rating Condition. Rating Condition where both sensible and latent cooling are present and the coil
27、surface temperature is above freezing. 3.11 Recirculation Ratio. (Recirculation Rate) The mass ratio of liquid circulated to the amount of liquid vaporized. 3.12 Refrigerant Saturation Temperature. Refrigerant temperature at the Unit Cooler inlet or outlet determined either by measuring the temperat
28、ure at the outlet of the two-phase refrigerant flow, for a Liquid Overfeed Unit Cooler, or by measuring refrigerant pressure and determining the corresponding temperature from reference thermodynamic tables or equations for the refrigerant F C. For zeotropic refrigerants, the corresponding temperatu
29、re to a measured pressure is the refrigerant Dew Point. 3.13 “Shall” or “Should”. “Shall” or “Should” shall be interpreted as follows: 3.13.1 Shall. Where “shall” or “shall not” is used for a provision specified, that provision is mandatory if compliance with the standard is claimed. 3.13.2 Should.
30、“Should” is used to indicate provisions which are not mandatory but which are desirable as good practice. 3.14 Standard Air Conditions. Dry air at 70 F 21 C and absolute pressure 29.92 in Hg 101.3 kPa. Under these conditions, dry air has a mass density of 0.075 lb/ft3 1.2 kg/m3. Copyright Air-Condit
31、ioning, Heating and Refrigeration Institute Provided by IHS under license with ARI Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-ARI STANDARD 420-2008 3 3.15 Steady-State Conditions. An operating state of a system, including its surroundings, in which the extent
32、of change with time is within the limits specified in Tables C3 and C4. 3.16 Temperature Difference (TD). The difference between the dry-bulb temperature of the air entering the Unit Cooler and the Refrigerant Saturation Temperature at the unit cooler outlet, F C. 3.17 Test Measurement. The reading
33、of a specific test instrument at a specific point in time. The Test Measurement may be averaged with other measurements of the same parameter at the same time to determine a Test Reading or averaged over the duration of the test to determine the value for the Test Run. 3.18 Test Reading. The recordi
34、ng of one full set of the Test Measurements required to assess the performance of the test unit. 3.19 Test Run. Test Readings compiled during Unit Cooler operation during which steady-state conditions have been maintained. It shall last for a minimum of 30 minutes with at least 15 consecutive Test R
35、eadings, all of which shall comply with the requirements of Tables C1, C2, C3 and C4. It includes all the information required to determine Unit Cooler performance at a specific rating condition. 3.20 Test Series. A group of Test Runs, performed on the same test unit, to determine performance at all
36、 required rating conditions. 3.21 Volatile Refrigerant. A refrigerant which changes from liquid to vapor in the process of absorbing heat. Section 4. Test Requirements 4.1 Test Requirements. All Standard Ratings of Unit Coolers shall be verified by tests conducted at Standard Rating Conditions in ac
37、cordance with one of the methods set forth in Appendix C. Table 1. Standard Rating Conditions Condition number Coil condition Entering Air Refrigerant Saturation Temperature2 Temperature Difference Dry-bulb temperature Wet-bulb temperature Relative humidity1 Dew Point temperature1 F C F C % F C F C
38、F C 1 Wet 50 10 46.1 7.83 75 - - 35 1.7 15 8.3 2 Dry 50 10 - - 45 30 -1.1 35 1.7 15 8.3 3 Dry 35 1.7 - - 50 20 -6.7 25 -3.9 10 5.6 4 Dry 10.0 -12.2 - - 46 -5.0 -21 0.00 -17.8 10 5.6 5 Dry -10.0 -23.3 - - 43 -25 32 -20.0 -28.9 10 5.6 Notes: 1. The dry coil condition can be confirmed by measuring eith
39、er the entering air dew point or relative humidity according to the instrumentation requirements of Table 2. At wet coil condition, relative humidity is for reference only. 2. Measured at coil outlet. 4.1.1 All regularly furnished equipment that will affect performance shall be in place during the t
40、est. 4.1.2 The refrigerant used during the test shall be one that is published for use with the Unit Cooler. 4.1.3 Each Standard Rating test shall be performed at either 50 Hz or 60 Hz and at the highest rated voltage as specified by the manufacturer on the unit or motor nameplate. 4.1.4 Instrumenta
41、tion Requirements. Precision instruments and automated electronic data acquisition equipment shall be used to measure and record temperature, pressure and refrigerant flow rate test parameters. The use of advanced technologies or methods of measurement not described in this appendix are acceptable,
42、provided the accuracy requirements of this appendix are achieved by the alternative method. Copyright Air-Conditioning, Heating and Refrigeration Institute Provided by IHS under license with ARI Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-ARI STANDARD 420-2008
43、4 4.1.4.1 Calibration All measuring instruments and instrument systems (e.g. data acquisition coupled to temperature, pressure, or flow sensors) shall be calibrated by comparison to primary or secondary standards with calibrations traceable to National Institute of Standards and Technology (NIST) me
44、asurements, other recognized national laboratories, or derived from accepted values of natural physical constants. All test instruments shall be calibrated annually, whenever damaged, or when the accuracy is called into question. 4.1.4.2 Selection and Accuracy. All measuring instruments shall be sel
45、ected to meet or exceed the accuracy criteria listed in Table 2 for each type of measurement. Table 2. Instrumentation Accuracy Measurement Medium Minimum Accuracy Instrument Examples I-P SI Temperature Air dry-bulb 0.10 F 0.06 C Resistance Temperature Device (RTD) Thermistor Air wet-bulb Refrigeran
46、t liquid Refrigerant vapor 0.5 F 0.3 C Special calibrated thermocouple Air Dew Point 0.5 F 0.3 C Chilled mirror hygrometer Others 1.0 F 0.6 C Liquid-in-glass thermometer Relative humidity1 Air 3 % points rh Capacitive or resistive rh sensor Pressure Refrigerant Pressure corresponding to 0.2 F of sat
47、uration temperature Pressure corresponding to 0.1 C of saturation temperature Transducer Air 0.05 inches of mercury 169 Pa Barometer Flow Refrigerant 1 % of reading Mass flow meter Liquids 1 % of reading Venturi Electrical Motor kilowatts/amperes/voltage 1 % of reading Power meter Auxiliary kilowatt
48、 input (e.g. heater) Amp probe Multimeter Speed Motor / fan shaft 1 % of reading Tachometer Weight Oil / refrigerant solution 0.5 % of reading Gravimeter (scale or analytical balance) Specific Gravity Brine 1 % of reading Hydrometer Time Hours / minutes / seconds 0.5 % of time interval Electronic cl
49、ock Note: 1. Relative humidity and air dew point measurements are intended to confirm the dry coil condition for test condition numbers 2 through 5. Section 5. Rating Requirements 5.1 Standard Ratings. Standard Ratings shall include Rated Power and Gross Total Cooling Effect established at all applicable St
