ASHRAE OR-10-037-2010 Effect of Dents in Condenser Fins on Air-Conditioner Performance《冷凝器翅板凹痕对于空调性能的影响》.pdf
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1、336 2010 ASHRAEABSTRACTExperiments demonstrated performance degradation inair-conditioning systems resulting from dents in the fins of theircondensers and the extent to which conventional fin repairmethods restore performance. Two different, commerciallyavailable residential-type air-conditioner con
2、densing unitswere tested. Flattening substantial areas of the fins caused areduction in capacity and efficiency of the cooling systemstested. Performance dropped appreciably after 60% of the finareas were pressed flat. With 100% of the fin area flattened,system capacity decreased by 27% and system S
3、EER by 34%for one of the systems. Combing the dented fins after theextreme case where all fins were flattened restored capacity towithin 1% and SEER to within 6% of the undented condition.Similar results were obtained for the second condenser unittested.INTRODUCTIONThe performance of residential and
4、 commercial air-conditioners has a large influence on electrical energyconsumption in the United States. In 2004, households in theU.S. used 216.8 billion kWh of electricity for air-condition-ing, accounting for 6.4 percent of all electricity consumed byresidences.1Commercial buildings in 2004 consu
5、med anadditional 169.9 billion kWh of electricity for air-condition-ing. In 2001, 80.8 million households within the U.S. were air-conditioned.2In 2003, 3.6 million commercial buildings wereair-conditioned.3Most of those were in the Southwest, southAtlantic, Midwest, and middle Atlantic states.2,3Th
6、e numberof air-conditioners found in any locale can be attributed to twoprimary factors: population and climate.Manufacturers rate the performance of their productsaccording to strict standards; however, there are many factorsthat can affect air-conditioning equipment performance afterinstallation.
7、One common condition found in the field is dentswithin fins of condensers. There are various causes of dents;one is impact from hail; others include strikes from wind-borne debris, and brushes of various items against the fins.Much of the continental United States experiences hail.Areas east of the
8、Rocky Mountains, particularly the south-western and midwestern states, are especially prone. In thoseareas, warm moist air from the Gulf of Mexico collides withcold air from the north, creating conditions that favor hail.Figure 1 is a map of the United States depicting locations of allreports of hai
9、l, inch (19.1 mm) in diameter and larger, from1981 to 1990.4Included on that same map is a breakdown bygeographical region of the number of residences and commer-cial buildings with air-conditioning. From the map, it is readilyapparent that hail-prone regions have many air-conditionedbuildings.Hails
10、 effect on crops, roofing, automobiles, and aircraftis well documented but there does not appear to be muchunderstanding of its impact on air-conditioning equipmentperformance. As far as the authors are aware of, no studieshave been published regarding hail effects on air-conditioners,specifically.
11、A related study reported by Dooley5indicatedthat fouling over time had minimal affect on efficiency andcapacity. Other than the common practice of combing dents inrepairing and maintaining air-conditioners, there does notappear to be published data quantifying effects dents in finshave on performanc
12、e.Hail physically alters air-conditioning systems by dentingtheir condenser coil fins. Typically, condenser coil assembliesEffect of Dents in Condenser Fins on Air-Conditioner PerformanceMatthew J. Sitzmann, PE Frank K. Lu, PE Steve R. SmithStudent Member ASHRAEMatthew J. Sitzmann is a senior engine
13、er and Steve R. Smith is an engineer at Haag Engineering, Co., Irving, TX. Frank K. Lu is a professorin the Mechanical and Aerospace Engineering Department at the University of Texas at Arlington, Arlington, TX.OR-10-037 2010, American Society of Heating, Refrigerating and Air-Conditioning Engineers
14、, Inc. (www.ashrae.org). Published in ASHRAE Transactions 2010, Vol. 116, Part 1. For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAEs prior written permission. ASHRAE Transactions 337comprise punched and press
15、ed aluminum fins fitted ontocopper coils. Fin spacing generally varies between 8 and 20fins per inch (3.1 and 7.9 fins per cm). The thin cross sectionsof the fins serve well to conduct heat from the refrigerant in thecoils and transfer it to air passing by them, but these fins areeasily bent. Figure
16、 2 is a photograph of a condenser with finsdeformed by hail. Not much has been reported on the extentair-conditioning system performance becomes degradedwhen fins are folded over in this way.A systematic study of the effect of fin dents on air-conditioning system performance is performed. Hail creat
17、esa wide range of dent shapes, sizes, and depths in condenserfins. Dent characteristics are governed by many variablesincluding properties of the impacting hailstones (size, hard-ness, and speed), orientation of the condenser to wind, andshielding features surrounding the condenser. The presentstudy
18、 does not fully replicate actual field conditions but islimited in scope in dealing only with a controlled, laboratorysituation to help in understanding the more complex dentingscenarios in practice. The study does incorporate severaldefining aspects of dents caused by hail such as a randomdistribut
19、ion of the dents, a discrete size of each dent, and adent characterized by fins folded on top of one another. Thelimited goals of this study are to determine the effects thatdents have on air-conditioning system performance and toFigure 1 Locations of hailstorms with 3/4-in. (19.1 mm) and larger dia
20、meter hail from 1981 to 1990.4Overlaid on the hail mapis the number of residences and commercial buildings with air-conditioning by region. 2,3Figure 2 Condenser fins of a rooftop air-conditioner thatwere dented by hail. 2010, American Society of Heating, Refrigerating and Air-Conditioning Engineers
21、, Inc. (www.ashrae.org). Published in ASHRAE Transactions 2010, Vol. 116, Part 1. For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAEs prior written permission. 338 ASHRAE Transactionsdetermine to what extent c
22、onventional fin repair methodscan restore performance.EXPERIMENTAL METHODTests were performed to determine the capacity andseasonal energy efficiency ratio (SEER) of two separate air-conditioning condensers as increasingly larger portions oftheir condenser fins were dented. All tests were conducteda
23、ccording to Air-Conditioning and Refrigeration Institute(ARI) standard 210/240.6,7In all cases, the indoor enthalpymethod was used for reporting performance, a schematic ofwhich is shown in Fig. 3. Figures 4 and 5 are photographs ofthe laboratory setup. The Outdoor Enthalpy Method was usedas a check
24、 of the accuracy of the indoor enthalpy method. Ducttraverses with pitot tubes mounted in accordance with ANSI/ASHRAE 41.1-2000 measured the airflow.7Figure 3 shows that a complete air-conditioning systemwas constructed using an outdoor condensing unit and anindoor air handler. The condensing unit a
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