AHRI 470-2006 Performance Rating of Desuperheater Water Heaters.pdf

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1、ANSI/AHRI Standard 470-2006 (Formerly ARI Standard 470-2006)2006 Standard for Performance Rating of Desuperheater/Water Heaters Price $10.00 (M) $20.00 (NM) Copyright 2006, by Air-Conditioning Heating and Refrigeration Institute Printed in U.S.A. Registered United States Patent and Trademark Office

2、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 products be designed, construc

3、ted, 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 accepted industry practices. A

4、HRI 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 470-2001. TABLE OF CONTENTS SECTION PAGE Section 1. Purpose .1 Section 2. Scope 1 Section 3. Definitions 1 Section 4. Test Re

5、quirements2 Section 5. Rating Requirements 2 Section 6. Minimum Data Requirements for Published Ratings.6 Section 7. Marking and Nameplate Data.7 Section 8. Conformance Conditions7 TABLES Table 1. Standard Rating Conditions2 APPENDICES Appendix A. References Normative .8 Appendix B. References Infor

6、mative .8 Appendix C. Method of Testing Desuperheater/Water Heaters Normative.9 AHRI STANDARD 470-2006 1 PERFORMANCE RATING OF DESUPERHEATER/WATER HEATERS Section 1. Purpose 1.1 Purpose. The purpose of this standard is to establish for Desuperheater/Water Heaters: definitions; test requirements; rat

7、ing 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

8、 standard is subject to review and amendment as technology advances. Section 2. Scope 2.1 Scope. This standard applies to Desuperheater/Water Heaters supplied as separate components, as defined in Section 3 and using single component and azeotropic refrigerants only. 2.2 Exclusions. This standard do

9、es not apply to Desuperheater/Water Heaters supplied as components of factory-assembled refrigeration or air conditioning units. This standard does not apply to systems using zeotropic refrigerants. Section 3. Definitions Definitions. All terms in this document follow the standard industry definitio

10、ns in the current edition of ASHRAE Terminology of Heating, Ventilation, Air Conditioning and Refrigeration unless otherwise defined in this section. 3.1 Desuperheater/Water Heater. A factory-made assembly of elements by which refrigerant vapor flow and water flow are maintained in such heat transfe

11、r relationship that the refrigerant vapor is desuperheated and the water is heated. 3.2 Field Fouling Allowance. Provisions for anticipated Fouling Factor during use. 3.2.1 Fouling Factor. The thermal resistance due to fouling accumulated on the heat transfer surface. 3.3 Net Heating Capacity. The u

12、seful heat exchanged between the refrigerant vapor and the water being heated. This value is the product of the mass flow rate of water, the specific heat of water and the water temperature rise, Btu/h W. 3.3.1 Clean Tube Capacity. This is the Net Heating Capacity of the heat exchanger, Btu/h W, wit

13、h clean tubes at the Standard Rating Conditions.3.4 Published Rating. A statement of 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 Desuperheater/Water Heaters of like nominal size

14、and type (identification) produced by the same manufacturer. As used herein, the term Published Rating includes all performance characteristics shown on the unit or published in specifications, advertising or other literature controlled by the manufacturer, at stated Rating Conditions. 3.4.1 Applica

15、tion Rating. A rating based on tests performed at application Rating Conditions. 3.4.2 Standard Rating. A rating based on tests performed at Standard Rating Conditions. 3.5 Rating Conditions. Any set of operating conditions under which a single level of performance results and which causes only that

16、 level of performance to occur. 3.5.1 Standard Rating Conditions. Rating Conditions used as the basis of comparison for performance characteristics. AHRI STANDARD 470-2006 2 3.6 “Shall“ or “Should.“ “Shall“ or “should“ shall be interpreted as follows: 3.6.1 Shall. Where “shall“ or “shall not“ is use

17、d for a provision specified, that provision is mandatory if compliance with the standard is claimed. 3.6.2 Should. “Should“ is used to indicate provisions which are not mandatory but which are desirable as good practice. Section 4. Test Requirements 4.1 Test Requirements. The tests shall be conducte

18、d in accordance with the test procedure contained in Appendix C. Section 5. Rating Requirements 5.1 Published Ratings. Published Ratings consist of Standard Ratings and Application Ratings. Such ratings shall be based on tests of Desuperheater/Water Heaters with the refrigerant specified in the rati

19、ngs. 5.2 Standard Ratings. Published Ratings shall include the Standard Rating, given for one of the Standard Rating Conditions shown in Table 1 and properly identified as the Standard Rating. Standard Ratings shall be based on tests with initially clean tubes. 5.3 Application Ratings. Application R

20、atings give performance data at operating conditions other than those shown in Table 1. Application Ratings shall contain all information shown in 6.2. When Application Ratings include water-side Field Fouling Allowance(s) they shall be calculated by the method specified in 5.4. Published Ratings sh

21、all be subject to the tolerances of this standard. 5.3.1 Either Application Ratings or a method of adjusting the clean tube ratings may be presented to show the effect of various water-side Field Fouling Allowances. These calculation methods or method of adjusting these ratings shall be calculated i

22、n accordance with 5.4. 5.4 Determination of Ratings. Ratings shall be determined in accordance with the following (where steady state operation is in a condensing mode, this analysis will be in error): 5.4.1 Clean Tube Ratings. Published Ratings shall be determined by test with initially clean tubes

23、 at conditions specified for the selected system in Table 1 and conducted in accordance with Appendix C. The results of these tests shall be accepted as including a Fouling Factor of zero. Table 1. Standard Rating Conditions Saturated Temperature of Entering Refrigerant Vapor Actual Temperature of E

24、ntering Refrigerant Vapor Temperature of Entering Water Temperature of Leaving Water Type System F C F C F C F C Air Cooled 125 51.7 220 104 90 and 120 32 and 48.9 140 60.0 Water Cooled 105 40.6 180 82.2 90 and 120 32 and 48.9 140 60.0 Note: Ratings are for single component and azeotropic refrigeran

25、ts only. Zeotropic refrigerants are excluded. AHRI STANDARD 470-2006 3 5.4.2 Fouled Tube Ratings. From the results of the clean tube tests, calculate the clean tube overall heat transfer coefficient, U . Then, mathematically add the specified Fouling Factor to the reciprocal of the clean tube U and

26、calculate the fouled ratings for publication, using the following methods, as applicable. c ca. Tube-in-tube (counter flow arrangement shown - parallel flow also covered). b. Single tube pass shell-and-tube (counter flow arrangement shown - parallel flow also covered). c. Coil-in-shell, single pass

27、(counter flow arrangement shown - parallel flow also covered). Obtain U from the following equation: cccq=UA(LMTD)1 where (LMTD) is defined by:cAHRI STANDARD 470-2006 4 for counter flow: ()re wl rl wecre wlrl we( - ) - ( - )tt ttLMTD = - ttln- tt2a for parallel flow: ()re we rl wlcre werl wl( - ) -

28、( - )tt ttLMTD = - ttln- tt2b The total thermal resistance is equal to the reciprocal of the overall coefficient of heat transfer:cccA(LMTD)1=RqU3The next step in determination of fouled ratings is the calculation of the total thermal resistance including fouling. This is found by adding the specifi

29、ed Fouling Factor to the clean-tube overall resistance, as illustrated below. 1. Refrigerant outside tubes (fouling inside): a. Basing calculations on outside surface area: ofo co fiiA= + RRrA4a b. Basing calculations on inside surface area: r+ R= R ficifi4b 2. Refrigerant inside tubes (fouling outs

30、ide): a. Basing calculations on outside surface area: r+ R= R focofo5a b. Basing calculations on inside surface area: AAr + R= Roifocifi5b Now calculate the following: Chot= ( cm&p)r= Hot fluid (refrigerant) capacity rate at Rating Conditions, Btu/(h F) W/C Ccold= ( cm&p)w= Cold fluid (water) capaci

31、ty rate at Rating Conditions, Btu/ (h F) W/C Cmin= The smaller of Chotor CcoldAHRI STANDARD 470-2006 5 Cmax= The larger of Chotor Ccoldqmax= Cmin(tre- twe), Btu/h W essdimensionl,CRA= NTUminf6 where Rfis based on area A. The actual heat transfer under fouled conditions, qf, is calculated from q = qf

32、 max 7 where is determined for either counter flow or parallel flow arrangements of the exchanger types shown in 5.4.2, items a, b and c. Counter flow, where Cmin Cmax( )()()min maxmin max-NTU 1 - /-NTU 1 - /min maxCCCC1-EXP=1- / EXPCC8a where Cmin= Cmax : ()NTU=1+ NTU8b Parallel flow: -NTUmin maxmi

33、n max(1+ / )CC1 - EXP = 1 + ( / )CC8c Now having the actual heat transfer under fouled conditions, the leaving water and refrigerant temperatures can be calculated from: fwl wecoldq=+ttC9a frl rehotq=-ttC9b The combination of qf, tweand tredefine the fouled ratings at the given operating conditions.

34、 5.5 Symbols and Subscripts. The symbols and subscripts used in Equations 1 through 9 are as follows: Symbols: A = Total heat transfer area, ft2m2 C = Flow-stream capacity rate ( m& cp), Btu/(h F) W/C cp= Specific heat at constant pressure, Btu/(lb F) kJ/(kg C) = Exchanger heat transfer effectivenes

35、s EXP = Base of natural logarithm, e LMTD = Log mean temperature difference, F C m& = Fluid mass flow rate, lb/h kg/s AHRI STANDARD 470-2006 6 NTU = Number of exchanger heat transfer units q = Total heat transfer rate, Btu/h W R = Total thermal resistance, h ft2 F/Btu m2 C/W r = Individual thermal r

36、esistance term, h ft2 F/Btu m2 C/W t = Temperature, F C U = Overall heat transfer coefficient, Btu/(h ft2 F) W/(m2 C) Subscripts: c = Clean e = Entering f = Fouled or fouling i = Inside l = Leaving o = Outside r = Refrigerant w = Water 5.6 Tolerances. To comply with this standard, published Net Heat

37、ing Capacity shall be based on data obtained in accordance with the provisions of this standard, and shall be such that any production unit selected at random and tested in accordance with this standard shall have a Net Heating Capacity not less than 95% of the Published Rating, a water pressure dro

38、p not more than 110% of the published water pressure drop and a refrigerant pressure drop not more than 110% of the published refrigerant pressure drop. Section 6. Minimum Data Requirements for Published Ratings 6.1 Minimum Data Requirements for Published Ratings. As a minimum, Published Ratings sha

39、ll include all Standard Ratings. All claims to ratings within the scope of this standard shall include the statement “Rated in accordance with AHRI Standard 470.” All claims to ratings outside the scope of this standard shall include the statement “Outside the scope of AHRI Standard 470.” Wherever A

40、pplication Ratings are published or printed, they shall include a statement of the conditions at which the ratings apply. 6.2 Published Ratings. Published Ratings shall state all the pertinent operating conditions and shall include the following: a. Refrigerant designation(s) per ANSI/ASHRAE Standar

41、d 34 with Addenda b. Entering refrigerant temperature, F C c. Entering refrigerant pressure, psig kPa gage d. Net Heating Capacity, Btu/h W e. Water flow rate, gpm L/s f. Water pressure drop, psi or ft H O kPa 2g. Refrigerant side pressure drop, psi kPa h. Refrigerant mass flow rate, lb/h kg/s i. Fo

42、uling Factor (water-side), ft2 h F/Btu m2 C/WPlus at least one of the following: j. Entering water temperature, F C k. Leaving water temperature, F C 6.3 Published Ratings shall be accompanied by the following information: a. Design pressures for water-side and refrigerant-side, psig kPa gage b. Min

43、imum water flow rate, gpm L/s, at minimum entering water temperature, F C c. Maximum recommended flow rate, gpm L/s d. If only clean tube ratings are published, a statement shall be included to contact the manufacturer if fouled tube ratings are required. AHRI STANDARD 470-2006 7 Section 7. Marking

44、and Nameplate Data 7.1 Marking and Nameplate Data. As a minimum, each Desuperheater/Water Heater shall have the following information shown in a conspicuous place: a. Name of manufacturer b. Manufacturers model number c. Design working pressure for the water side d. Design working pressure for the r

45、efrigerant side Section 8. Conformance Conditions 8.1 Conformance. While conformance with this standard is voluntary, conformance shall not be claimed or implied for products or equipment within the standards Purpose (Section 1) and Scope (Section 2) unless such product claims meet all of the requir

46、ements of the standard and all the requirements of the testing and rating requirements are measured and reported in complete compliance with the standard. Any product that has not met all the requirements of the standard shall not reference, state, or acknowledge the standard in any written, oral, o

47、r electronic communication. AHRI STANDARD 470-2006 8 APPENDIX A. REFERENCES NORMATIVE A1 Listed here are all standards, handbooks and other publications essential to the formation and implementation of the standard. All references in this appendix are considered as part of the standard.A1.1 ANSI/ASH

48、RAE Standard 34-2004 with Addenda, Designation and Safety Classification of Refrigerants, 2004, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., 1791 Tullie Circle N.E., Atlanta, GA 30329, U.S.A. A1.2 ANSI/ASHRAE Standard 41.1-1986 (RA 2006), Standard Method for Tempe

49、rature Measurement, 2006, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., 1791 Tullie Circle N.E., Atlanta, GA 30329, U.S.A. A1.3 ASHRAE Handbook Fundamentals, 2005, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., 1791 Tullie Circle N.E., Atlanta, GA 30329, U.S.A. A1.4 ASHRAE Terminology