AHRI 420-2008 Performance Rating of Forced-Circulation Free-Delivery Unit Coolers for Refrigeration.pdf

1、 ANSI/AHRI Standard 420 (Formerly ARI Standard 420) 2008 Standard for Performance Rating of Forced-Circulation Free-Delivery Unit Coolers for Refrigeration Price $10.00 (M) $20.00 (NM) Copyright 2008, by Air-Conditioning, Heating, and Refrigeration Institute Printed in U.S.A. Registered United State

2、s Patent and Trademark Office IMPORTANT SAFETY DISCLAIMER AHRI does not set safety standards and does not certify or guarantee the safety of any products, components or systems designed, tested, rated, installed or operated in accordance with this standard/guideline. It is strongly recommended that

3、products be designed, constructed, assembled, installed and operated in accordance with nationally recognized safety standards and code requirements appropriate for products covered by this standard/guideline. AHRI uses its best efforts to develop standards/guidelines employing state-of-the-art and

4、accepted industry practices. AHRI does not certify or guarantee that any tests conducted under its standards/guidelines will be non-hazardous or free from risk. Note: This standard supersedes ARI Standard 420-2000. TABLE OF CONTENTS Section 1 Purpose 1 Section 2 Scope .1 Section 3 Definitions.1 Sect

5、ion 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 Instrumentation Accuracy .4 APPENDICES Appendix A Ref

6、erences 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 C3 Test Condition Tolerances 11 Table C4 Refr

7、igerant Temperature Tolerances . 12 FIGURES FOR APPENDICES Figure C1 Method 1: DX Dual Instrumentation .24 Figure C2 Method 2: DX Calibrated Box. 25 Figure C3 Method 3: Liquid Overfeed 26 ANSI/AHRI STANDARD 420-2008 1 PERFORMANCE RATING OF FORCED-CIRCULATION FREE-DELIVERY UNIT COOLERS FOR REFRIGERAT

8、ION 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 requirements; minimum data requirements for Published Ratings; marking and nameplate data; and conformance cond

9、itions. 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 standard is subject to review and amendment as technology advances. Section 2. Scope 2.1 Scope. This standard app

10、lies 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 wet and/or dry conditions. 2.1.1 Exclusions. This standard does not apply to: 2.1.1.1 Air-conditioning units used

11、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 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 z

12、eotropic 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 definitions in the current edition of ASHRAE Terminology of Heating, Ventilation, Air Conditioning and Refrigeration unles

13、s 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 the air entering the Unit Cooler and the calculated enthalpy of saturated air at the Refrigerant Saturation Tempe

14、rature 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 elements by which heat is transferred from air to refrigerant without any element external to the cooler imposing a

15、ir 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 vapor is superheated. 3.3.2 Liquid Overfeed Unit Cooler. A Unit Cooler in which the refrigerant liquid is supplied

16、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) for a zeotropic refrigerant exclusive of any liquid subcooling or vapor superheating. ANSI/AHRI STANDARD 420-20

17、08 2 3.5 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 Effe

18、ct. The 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

19、 at the 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

20、 all units 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 R

21、ating Conditions. 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 f

22、an motor 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.

23、Rating Conditions 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 t

24、he coil 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

25、temperature 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 t

26、emperature 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

27、Should. “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/ft31.2 kg/m3. ANSI/AHRI STA

28、NDARD 420-2008 3 3.15 Steady-State Conditions. An operating state of a system, including its surroundings, in which the extent 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

29、 the Unit Cooler and the Refrigerant Saturation Temperature at the unit cooler outlet, F C. 3.17 Test Measurement. The reading 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

30、 Test Reading or averaged over the duration of the test to determine the value for the Test Run. 3.18 Test Reading. The recording 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 wh

31、ich steady-state conditions have been maintained. It shall last for a minimum of 30 minutes with at least 15 consecutive Test Readings, 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 spec

32、ific rating condition. 3.20 Test Series. A group of Test Runs, performed on the same test unit, to determine performance at all 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 T

33、est Requirements. All Standard Ratings of Unit Coolers shall be verified by tests conducted at Standard Rating Conditions in accordance with one of the methods set forth in Appendix C. Table 1. Standard Rating Conditions Condition number Coil condition Entering Air Refrigerant Saturation Temperature

34、2Temperature Difference Dry-bulb temperature Wet-bulb temperature Relative humidity1 Dew Point temperature1F C F C % F C F C 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

35、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 either 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.

36、 Measured at coil outlet. 4.1.1 All regularly furnished equipment that will affect performance shall be in place during the test. 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

37、 or 60 Hz and at the highest rated voltage as specified by the manufacturer on the unit or motor nameplate. 4.1.4 Instrumentation Requirements. Precision instruments and automated electronic data acquisition equipment shall be used to measure and record temperature, pressure and refrigerant flow rat

38、e test parameters. The use of advanced technologies or methods of measurement not described in this appendix are acceptable, provided the accuracy requirements of this appendix are achieved by the alternative method. ANSI/AHRI STANDARD 420-2008 4 4.1.4.1 Calibration All measuring instruments and ins

39、trument 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) measurements, other recognized national laboratories, or

40、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 selected to meet or exceed the accuracy criteria listed in

41、 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 Refrigerant liquid Refrigerant vapor 0.5 F 0.3 C Special calibrat

42、ed 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 humidity1Air 3 % points rh Capacitive or resistive rh sensor Pressure Refrigerant Pressure corresponding to 0.2 F of saturation temperature Pressure corresponding to 0.1 C of s

43、aturation 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 input (e.g. heater) Amp probe Multimeter Speed Motor /

44、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 clock Note: 1. Relative humidity and air dew point measure

45、ments 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 Standard Rating Conditions specified in Table 1. 5

46、.2 Application Ratings. Application Ratings shall include Rated Power and Gross Total Cooling Effect at conditions other than Standard Rating Conditions. Application Ratings with Refrigerant Saturation Temperatures below 32 F 0.0 C ANSI/AHRI STANDARD 420-2008 5 shall be rated at dry conditions. Appl

47、ication Ratings published by the manufacturer shall be clearly identified as Application Ratings. 5.3 Tolerances. To comply with this standard, any representative production unit selected at random, when tested at the Standard Rating Conditions, shall have a Gross Total Cooling Effect not less than

48、95 % of its published Standard Rating and not exceed 105 % of its Rated Power. Section 6. Minimum Data Requirements for Published Ratings 6.1 Minimum Data Requirements for Published Ratings. As a minimum, Published Ratings shall include all Standard Ratings at which the unit will be produced, market

49、ed or sold. All claims to ratings for products within the scope of this standard shall be accompanied by the statement “Rated in accordance with ARI Standard 420.” All claims to ratings outside the scope of this standard shall include the statement “Outside the scope of ARI Standard 420.” Wherever Application Ratings are published or printed, they shall include a statement of the conditions at which the ratings apply. 6.2 Required Published Ratings. All published Standard Ratings and Application Rating