1、 STD-AR1 GUIDELINE E-ENGL 1997 0352320 00LlLOb 039 M 1997 GUIDELINE for AIR-CONDITIONING thus increasing operating com by8Z. The impact couid be greater or less tim this, depending m the typeandamount of tube surface used in condenser and evaporam. waterchillingrefiigmoperatingfullyloadedat Section
2、5. Current Status Sevaal events have occurred in recent years to change the way the industry deals with fouling, as noted in the foUOwing paragraphs: 5.1 The air canditiang industry has beai under pressure to improve unit efficiency and has responded with signiflcant improvements. This has been done
3、 Uuough improved compressors and improved heat exchangers to reduce the approach temperatures within heat exchangers. Where heat exchangers used to have 5“ to 6F 2.7“ to now have and 2F l.l“C leaving temptwe differences. With these small leaving temperature diEerences the field fouling allowance of
4、O.ooO25 or 2.5 x 104 hr ff “F/Btu 4.4 x lo5 n? “C/Wl is now more of the total heat transfer resistance than it was when designs were based on 5F and 6F 2.7“C and 3.3“CJ leaving temperature differences. Due to this, the use of a field fouling allowance of 0.00025 or 2.5 x lo4 hr ff“F/Btu 14.4 x 18 m2
5、 “C/wJ can in some cases result in the selection of different equipment than if the field fouling allowance were lower. This will then result in equipment that may not be as efficient when operating with clean tubes. 3.3“C leawig tnnperatirre differences, many applications 5.2 As a result ofa lack o
6、fhdamental data to justify the use ofa field fouling allowance of 0.00025 or 2.5 x lo“ hr ff “F/Btu 4.4 x lo- m2 “Cm, a research project was undertaken by ASHRAE to evaluate water quality and its effecs on fixding and to experimentally study the tubside fouling resistance in water chiilex flooded ev
7、aporators. The detailsofthesestudiesare Summarized in ASHRAE papers listed in Appendix B. 53 in the work associated with refemce B1.2, several experimental tests wererun with various connbinations of clean water, dirty water, different tube types, and 3 ft/sec. 0.9 ds and 7 ft/sez. 2.1 ds water veio
8、cities. The results inciicateci that even in the worst Case, the levei of fouing aftaexteridedoperation was less than 11.6% of the standard practice of using 0.00025 or 2.5 x IV hr HZ“FBtu 4.4 x 10 m2 “C/WJ. This result indimes that fa evapmtm, the O.ooo25 a 2.5 x lo- hr ft2“F/Btu 4.4 x 10-5 m2 “Cm
9、is overly conservative and is counter to the efforts to impwe opemtng efciency of chillers. From these results, a field fouling allowance of O.OOO1 or 1.0 x lo4 hr ffF/Btu 1.8 x lo- m2 “C/wJ appears to be more appqrbte for evaporators and is the recommendation of this guideline. This does not apply
10、to condensers, as experimental data for condensers has not bem developed. It is expected that the condenser would most likely have a higher fouling due to the higher temperatures of the water and the formation of biological fcung. Natethatresearchhas shown that temperanire can be a strong amhibutor
11、to the rate of fouling and condenser waterismuchwannerdianevaporator water. Ais0 mling tom tend tohave more contaminants in the water due to the loss of water due to evaporation in the tower. 5.4 ASHRAE is pianning to Continue fouling research on condensers, but results are now conclusive that a fou
12、ling allowance for evaporators of 0.00025 or 2.5 x 104 hr ft2“F/Btu 4.4 x lo d “Cm is overly conservative and should be reduced to the O.OOO1 or 1.0 x lV hr ff “F/Btu f1.8 10-5 rn2 ocm . Section 6. Implementation 6.1 In response to the above mentioned developments, Al began an effart to moncile the
13、treatment of fouling in its product standards with current lmowiedge and methods. By so doing, it was anticipated that old unsupported practices would be dropped and the new evaporam field fouling allowances adopted. This effort will ailow for the continued improvement and opthkation of air- conditi
14、oning and refiigdon equipment and the reduction in energy operating costs through proper selection of equipment. Section 7. Conclusions 7.1 The air-conditioning and refrigeration industry will adopt the new evaporam field fouling allowance of O.OOO1 or 1.0 x 104hr*?“F/Btu 1.8 x los m2 “C/Wl under th
15、e assumption that closed-loop systems are used. if other systems are used then different field fouling allowances may be required. 2 Copyright Air-Conditioning and Refrigeration Institute Provided by IHS under license with ARINot for ResaleNo reproduction or networking permitted without license from
16、 IHS-,-,-STD-AR1 GUIDELINE E-ENGL 1777 W U352120 ROLL111 4Tb AR1 GUIDEUNE E-1997 7.2 Until rther research is completed on umdensers, the 7.4 Manufactcrers, in adjusting fim “as industry wiii continue to use the previous field fouling aiiowanced0.00025 or 2.5 x 104 hr d FBtu 4.4 x lu5 m2 “Cm. 73 The
17、air conditioning and refrigerarion industry should suppat additionai ASHRAE research on fouling of umdensers, leading to further improvements to the field performance to prediaed field fouling performance, should usethecalcula?ionmethodsoutluiedinARIStandards450 and 480. This as sume that all fktory
18、 tests wiU have clean tubes with no fouling. - fouling allowance. 3 Copyright Air-Conditioning and Refrigeration Institute Provided by IHS under license with ARINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-STD-AR1 GUIDELINE E-ENGL 1777 0352320 OOL1112 332 AR1 GU
19、IDELINE E-1997 APPENDIX A. REFERENCES None. = NORMATIVE APPENDIX B. REFERENCES - INFORMATIVE B1 Listed here are standards, handbooks, and other publications which may provide useful infarrnation and Wgramd but are not considered essential. AU references in this appendix are not considered as part of
20、 this guideline. B1.1 A Survey of Water Qualig And Its Effect On Fouling in Flooded Water Chiller Evaporators by S.I. hider, R.L. Webb, A.K. Meiiz, American Society of Heating,R&igating and AirConditioning Engineers, 1791 Tuiiie Cile, N.E., Atlanta, GA 30329, U.S.A. B1.2 An Experimental Study of Tub
21、e-Side Fouling Resistance in Water-Chilled Flooded Evaporators by SI bider. ILL. Webb, A.K. Meia, American Society of Heating, Refrigerating and Air-conditioning Engineers, 1791 We Circle, NE, Atlanta, GA 30329, U.S.A. B13 ARi Standard 450-93, Water-Cooled Refrigerant Condensers, Remote Type, 1993,
22、Air- Conditioning and Refrigeration Institute, 4301 North Fairkx Drive, Suite 425, Arlington, VA 22203, U.S.A. B1.5 AR Standard 550/590-97, Water Chilling Packages Using the Vapor Compression Cycle, 1997, Air-conditioning and Refrigeration Institute, 4301 North Fairfax Drive, Suite 425, Arlington, V
23、A 22203, U.S.A. B1.6 ARI Sandard 560-92, Absorption Water Chilling and Water Heating Packages, 1992, Air- Conditioning and Reigeration Institute, 4301 North FaE.fax Drive, Suite 425, Arlington, VA 22203, U.S.A. B1.7 AR Guideline E-1988, Fouling Factors: A Survey Of Their Application in Todays Air- c
24、onditioning And Refrigeration Industry, 1988, Air- Conditioning and Refrigeration Institute, 4301 North Fairfix Drive+ Suite 425, Arlington, VA 22203, U.S.A. B1.8 Standards of the Tubular Exchangers Manufacturers Association, Tubular Exchanger Manucturers Asochtion, 25 North Broadway, Tarrytown, NY
25、10591, U.S.A. B1.4 AM Standard 480-95, Refrigerant-Cooled Liquid Coolers, Remote Type, 1995, Air-ConditiOning and Refrigeration Institute, 4301 North FairEax Drive, Suite 425, Arlington, VA 22203, U.S.A. 4 Copyright Air-Conditioning and Refrigeration Institute Provided by IHS under license with ARIN
26、ot for ResaleNo reproduction or networking permitted without license from IHS-,-,-STD.ARI GUIDELINE E-ENGL 1,777 m 0352220 OOI,J,I,I, 277 rn ARI Guideline E-1988 AR1 GUIDELINE E-1997 Condensers Ev&mators 0.00025 or 0.00025 or 2.5 x i 2.5 x lo4 hr*ft20F/Btu hr*ft2“F/Btu 14.4 x io- m2 14.4 x io- mz “C
27、/Wl “C/Wl APPENDIX C. FIELD FOULING ALLOWANCE CALCULATION ARI Guideline E-1997 C.l Rating Basis. 0.00025 ur o.Ooo1 or 2.5 x lo4 1.0 x io4 hr*ftZ“F/BtU hr*“F/BtU E4.4 x lu5 m2 C1.8 x i mz “CN “W Q = U&,LhrlTD u0 = 1R where: Q = Heattransferrate & = Surface area outside, fP mT L,M“D = Log mean tempera
28、ture difference U, = Overall heat transfer coefficient based on outside area Tw = Temperanne of water, OF “CI Tr = Temperamre of refngetant, OF “Cl = Overail themal resistance, hr*f?“F/Btu mz “C/wl an2 “c/w cm2 “cm Rf = Field fouling allowance, hr*ft2oF/Btu Rm= Tube metai resistance, hr*“F/Btu hw =
29、Water-side heat transfer coefficient hr = Refrigerant heat transfer coefficient & = l/hW+Rf+Rm+lh l/hw Rf Rrn ihr TW Tr Refrigerant Side 5 Copyright Air-Conditioning and Refrigeration Institute Provided by IHS under license with ARINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
