FIELD OF INVENTION

This invention relates to air conditioning systems, and in particular to enhancing performance of outdoor air conditioner condenser fans and heat pump assemblies by using twisted shaped blades with optimized air foils for improving air flow andminimizing motor power with and without additional performance enhancement improvements to augment air flow and air efficiency and/or reduce undesirable sound noise levels.

BACKGROUND AND PRIOR ART

Central air conditioning (AC) systems typically rely on using utilitarian stamped metal fan blade designs for use with the outdoor air conditioning condenser in a very large and growing marketplace. In 1997 alone approximately five millioncentral air conditioning units were sold in the United States, with each unit costing between approximately $2,000 to approximately $6,000 for a total cost of approximately $15,000,000,000(fifteen billion dollars). Conventional condenser fan bladestypically have an air moving efficiency of approximately 25%. For conventional three-ton air conditioners, the outdoor fan motor power with conventional type permanent split capacitor (PSC) motors is typically 200 250 Watts which produces approximately2000 3000 cfm of air flow at an approximately 0.1 to 0.2 inch water column (IWC) head pressure across the fan. The conventional fan system requires unnecessarily large amounts of power to achieve any substantial improvements in air flow and distributionefficiency. Other problems also exist with conventional condensers include noisy operation with the conventional fan blade designs that can disturb home owners and neighbors.

Air-cooled condensers, as commonly used in residential air conditioning and heat pump systems, employ finned-tube construction to transfer heat from the refrigerant to the outdoor air. As hot, high pressure refrigerant passes through the coil,heat in the compressed refrigerant is transferred through the tubes to the attached fins. Electrically powered fans are then used to draw large quantities of outside air across the finned heat transfer surfaces to remove heat from the refrigerant sothat it will be condensed and partially sub-cooled prior to its reaching the expansion valve.

Conventional AC condenser blades under the prior art are shown in FIGS. 1 3, which can include metal planar shaped blades 2, 4, 6 fastened by rivets, solder, welds, screws, and the like, to arms 3, 5, and 7 of a central condenser base portion 8,where the individual planar blades (4 for example) can be entirely angle oriented.

The outside air conditioner fan is one energy consuming component of a residential air conditioning system. The largest energy use of the air conditioner is the compressor. Intensive research efforts has examined improvements to it performance. However, little effort has examined potential improvements to the system fans. These include both the indoor unit fan and that of the outdoor condenser unit.

Heat transfer to the outdoors with conventional fans is adequate, but power requirements are unnecessarily high. An air conditioner outdoor fan draws a large quantity of air at a very low static pressure of approximately 0.05 to 0.2 inches ofwater column (IWC) through the condenser coil surfaces and fins. A typical 3-ton air conditioner with a seasonal energy efficiency ratio (SEER) of 10 Btu/W moves about 2400 cfm of air using about 250 Watts of motor power. The conventional outdoor fanand motors combination is a axial propeller type fan with a fan efficiency of approximately 20% to approximately 25% and a permanent split capacitor motor with a motor efficiency of approximately 50% to approximately 60%, where motor efficiency is theinput energy which the motor converts to useful shaft torque, and where fan efficiency is the percentage of shaft torque which the fan converts to air movement.

In conventional systems, a 1/8 hp motor would be used for a three ton air conditioner (approximately 94 W of shaft power). The combined electrical air "pumping efficiency" is only approximately 10 to approximately 15%. Lower condenser fanelectrical use is now available in higher efficiency AC units. Some of these now use electronically commutated motors (ECMs) and larger propellers. These have the capacity to improve the overall air moving efficiency, but by about 20% at high speed orless. Although more efficient ECM motors are available, these are quite expensive. For instance a standard 1/8 hp permanent split capacitor (PSC) condenser fan motor can cost approximately $25 wholesale whereas a similar more efficient ECM motor mightcost approximately $135. Thus, from the above there exists the need for improvements to be made to the outdoor unit propeller design as well as for a reduction to the external static pressure resistance of the fan coil unit which can have large impactson potential air moving efficiency. Consumers also express a strong preference for quieter outdoor air conditioning equipment. Currently fan noise from the outdoor air conditioning equipment is a large part of the undesirable sound produced.

Over the past several years, a number of studies have examined various aspects of air conditioner condenser performance, but little examining specific improvements to the outdoor fan unit. One study identified using larger condenser fans aspotentially improving the air moving efficiency by a few percent. See J. Proctor, and D. Parker (2001). "Hidden Power Drains: Trends in Residential Heating and Cooling Fan Watt Power Demand," Proceedings of the 2000 Summer Study on Energy Efficiency inBuildings, Vol. 1, p. 225, ACEEE, Washington, D.C. This study also identified the need to look into more efficient fan blade designs, although did not undertake that work. Thus, there is an identified need to examine improved fan blades for outdoor airconditioning units.

Currently, major air conditioner manufacturers are involved in efforts to eliminate every watt from conventional air conditioners in an attempt to increase cooling system efficiency in the most cost effective manner. The prime pieces of energyusing equipment in air conditioners are the compressor and the indoor and outdoor fans.

Conventional fan blades used in most AC condensers are stamped metal blades which are cheap to manufacture, but are not optimized in terms of providing maximum air flow at minimum input motor power. Again, FIGS. 1 3 shows conventional stampedmetal condenser fan blades that are typically used with typical outdoor air conditioner condensers such as a 3 ton condenser.

In operation, a typical 3-ton condenser fan from a major U.S. manufacturer draws approximately 195 Watts for a system that draws approximately 3,000 Watts overall at the ARI 95/80/67 test condition. Thus, potentially cutting the outdoor fanenergy use by approximately 30% to 50% can improve air conditioner energy efficiency by approximately 2% to 3% and directly cut electric power use.

Residential air conditioners are a major energy using appliance in U.S. households. Moreover, the saturation of households using this equipment has dramatically changed over the last two decades. For instance, in 1978, approximately 56% ofU.S. households had air conditioning as opposed to approximately 73% in 1997 (DOE/EIA, 1999). The efficiency of residential air conditioner has large impacts on utility summer peak demand since air conditioning often comprises a large part of systemloads.

Various information on typical air conditioner condenser systems can be found in references that include:

DOE/EIA, 1999. A Look at Residential Energy Consumption in 1997, Energy Information Administration, DOE/EIA-0632 (97), Washington, D.C.

J. Proctor and D. Parker (2001). "Hidden Power Drains: Trends in Residential Heating and Cooling Fan Watt Power Demand," Proceedings of the 2000 Summer Study on Energy Efficiency in Buildings, Vol. 1, p. 225, ACEEE, Washington, D.C.

J. Proctor, Z. Katsnelson, G. Peterson and A. Edminster, Investigation of Peak Electric Load Impacts of High SEER Residential HVAC Units, Pacific Gas and Electric Company, San Francisco, Calif., September, 1994.

Many patents have been proposed over the years for using fan blades but fail to deal with specific issues for making the air conditioner condenser fans more efficient for flow over the typical motor rotational speeds. See U.S. Pat. No.4,526,506 to Kroger et al.; U.S. Pat. No. 4,971,520 to Houten; U.S. Pat. No. 5,320,493 to Shih et al.; U.S. Pat. No. 6,129,528 to Bradbury et al.; and U.S. Pat. No. 5,624,234 to Neely et al.

Although the radial blades in Kroger '506 have an airfoil, they are backward curved blades mounted on an impeller, typically used with a centrifugal fan design typically to work against higher external static pressures. This is very differentfrom the more conventional axial propeller design in the intended invention which operates against very low external static pressure (0.05 0.2 inches water column--IWC).

Referring to Houten '520, their axial fan describes twist and taper to the blades, and incorporates a plurality of blades attached to an impeller, rather than a standard hub based propeller design. This impeller is not optimal for standardoutdoor air conditioning systems as it assumes its performance will be best when it is heavily loaded and is located very close to the heat exchanger (as noted in "Structure and Operation", Section 50). In a standard residential outdoor air conditioner,the fan is located considerably above the heat exchange surfaces and the fan operates in a low-load condition under low external static pressure. This distinction is clear in FIG. 1 of the Houten apparatus where it is intended that the fan operateimmediately in front of the heat exchange surface as with an automobile air conditioning condenser (see High Efficiency Fan, 1, last paragraph). The blades also do not feature a true air foil with a sharp trailing edge shown in FIG. 4A 4B.

Referring to Shih et al. '493, the axial fan describes features twisted blades, but are designed for lower air flow and a lower as would be necessary for quietly cooling of office automation systems. Such a design would not be appropriate forapplication for air condition condenser fan where much large volumes of air (e.g. 2500 cfm) must be moved at fan rotational velocities of 825 1100 rpm. The low air flow parameters and small air flow produced are clearly indicated in their "DetailedDescription of the Invention." The speed and air flow requirements for residential airconditioning condensers require a considerably different design for optimal air moving performance.

Referring to Bradbury '528, that device encompasses an axial fan designed to effectively cool electronic components in a quiet manner. The fans feature effective air foils, but the specific blade shape, chord, taper and twist are not optimizedfor the specific requirements for residential air conditioning condensers (825 1100 rpm with 2000 4800 cfm of air flow against low static pressures of 0.10 0.15 IWC) Thus, the cross sectional shapes and general design of this device are not relevant tothe requirements for effective fans for air conditioner condensers. The limitations of Bradbury are clearly outlined in Section 7, 40 where the applicable flow rates are only 225 to 255 cfm and the rotational rates are 3200 to 3600 rpm. By contrast,the residential air conditioner condenser fans in the proposed invention can produce approximately 2500 to approximately 4500 cfm at rotational velocities of approximately 825 to approximately 1100 rpm

The Neely '234 patented device consists of an axial fan designed for vehicle engine cooling. Although its blades include a twisted design and airfoil mounted on a ring impeller, it does not feature other primary features which distinguished theproposed invention. These are a tapered propeller design optimized for an 825 1100 RPM fan speed and for moving large quantities of air (2000 2500 cfm) at low external static pressure. As with the prior art by Houten, the main use for this inventionwould be for radiator of other similar cooling with an immediately adjacent heat exchanger. The Neely device is optimized for higher rotational speeds (1900 2000 rpm) which would be too noisy for outdoor air conditioner condenser fan application (seeTable 1). It also does not achieve sufficient flow as the Neely device produces a flow of 24.6 25.7 cubic meters per minute or 868 to 907 cfm--only half of the required flow for a typical residential air conditioner condenser (Table 1). Thus, the Neelydevice would not be use relevant for condenser fan designs which need optimization of the blade characteristics (taper, twist and airfoil) for the flow (approximately 2500 to approximately 4500 cfm) and rotational requirements of approximately 825 toapproximately 1100 rpm.

The prior art air conditioning condenser systems and condenser blades do not consistently provide for saving energy at all times nor sound reduction when the air conditioning system operates and do not provide dependable electric load reductionunder peak conditions.

Thus, improved efficiency of air conditioning condenser systems would be both desirable for consumers as well as for electric utilities.

For air conditioning manufacturers, reducing the sound produced by outdoor units is at least as large an objective as reducing unit energy consumption. In a detailed survey of 550 homeowners, researchers found that increases in the ambientbackground sound levels of 5 dB or more were associated with dramatic increases in the number of complaints about air conditioner noise levels. Similarly, the same study indicated that surveyed people would be willing to pay up to 12% more to purchase avery quiet air conditioner. See: J. S. Bradley, "Noise from Air Conditioners," Acoustics Laboratory, Institute for Research and Construction, National Research Council of Canada, Ottawa, Ontario, 1993.

Thus, achieving very low sound levels in outdoor air conditioning units and heat pump assemblies is a very important objective for air conditioning condenser fan system manufacturers.

Thus, the need exists for solutions to the above problems in the prior art.

SUMMARY OF THE INVENTION

A primary objective of the invention is to provide condenser fan blades for air conditioner condenser or heat pump systems and methods of use that saves energy at all times when the air conditioning system operates, provides dependable electricload reduction under peak conditions, and operates more quietly than standard air conditioners.

A secondary objective of the invention is to provide condenser fan blades for air conditioner condenser or heat pump systems and methods of use that would be both desirable for both consumers as well as for electric utilities.

A third objective of the invention is to provide air conditioner condenser blades and methods of use that increase air flow and energy efficiencies over conventional blades.

A fourth objective of the invention is to provide air conditioner condenser blades for air conditioning systems or heat pumps that can be made from molded plastic, and the like, rather than stamped metal.

A fifth objective of the invention is to provide systems and methods for operating air conditioner condenser or heat pump fan blades at approximately 825 rpm to produce airflow of approximately 2000 cfm using approximately 110 Watts of power.

A sixth objective of the invention is to provide a condenser or heat pump fan blade and methods of use that improves air flow air moving efficiencies by approximately 30% or more over conventional blades.

A seventh objective of the invention is to provide a condenser or heat pump fan blade and methods of use that uses less power than conventional condenser motors.

An eighth objective of the invention is to provide a condenser or heat pump fan blade and diffuser assembly and methods of use that allows for more quiet outdoor operation than conventional condenser or heat pump fans.

A ninth objective of the invention is to provide a condenser fan blade or heat pump assembly and methods of use which aids heat transfer to the air conditioner condenser that rejects heat to the outdoors.

A tenth objective of the invention is to provide a condenser or heat pump fan blade assembly and method of use that provides demonstrable improvements to space cooling efficiency.

An eleventh objective of the invention is to provide a condenser or heat pump fan assembly and method of use that has measurable electric load reduction impacts on AC system performance under peak demand conditions.

A twelfth objective of the invention is two diffuser design configurations to reduce pressure rise on the condenser fan and velocity pressure recovery to further improve air moving performance. Tests showed short conical exhaust diffuser canimprove air moving efficiency by a further approximately 21% (approximately 400 cfm) over a conventional "starburst" or coil wire type exhaust grill.

A thirteenth objective is to provide air conditioner condenser fan blades having an asymmetrical configuration and methods of use to achieve lower sound levels due to its altered frequency resonance, thus having reduced noise effects overconventional configurations.

A fourteenth objective of the present invention is to provide the exhaust diffuser interior walls with members and method of use which safely reduces fan blade tip clearance improving air moving performance while breaking up fan vortex sheddingwhich is largely responsible for high fan noise.

A fifteenth objective of the invention is to provide for methods and systems and components that achieve very low sound levels in outdoor air conditioning units having condenser fan systems.

Embodiments for the invention include an approximately 19 inch tip to tip condenser fan blade system, and an approximately 27 inch tip to tip condenser fan blade system. The higher efficiency fan produces a fan blade shape that will fit inconventional AC condensers (approximately 19 inches wide for a standard three-ton condenser and approximately 27 inches wide for a higher efficiency model) with the improved diffuser sections. The tested 19 inch fan provides an airflow of approximately850 rpm to produce approximately 1930 cfm of air flow at up to approximately 140 Watts using a 8-pole motor.

Using an OEM 6-pole 1/8 hp motor produced approximately 2610 cfm with approximately 145 Watts of power while running the blades at approximately 1100 rpm.

Asymmetrical air conditioner condenser fan blades are also described that can reduce noise effects over conventional air conditioner condenser or heat pump fan blades by allowing lower RPM (revolutions per minute) operation and reduction of bladefrequency resonance. A preferred embodiment shows at least an approximate 1 dB reduction using a five blade asymmetrical configuration.

Novel diffuser housing configurations can include a conical housing, a conical center body to aid air flow, and rounded surfaces for reducing backpressure problems over the prior art.

A porous surface liner, such as a foam strip can be provided on the interior facing walls of the diffuser housing to reduce vortex shedding and the associated noise produced therefrom. An open cell foam liner can be used having the extra doubleadvantage of reducing fan tip clearance and greatly improving air flow performance from the condenser fan. A porous edge, such as a foam strip can also be used on either or both the trailing edge or the tip edge of the rotating blades. The porous edgecan be used with or without the surface liner to reduce undesirable sound noise emissions as well as increase air flow performance of the rotating blades.

Further objects and advantages of this invention will be apparent from the following detailed description of the presently preferred embodiments which are illustrated schematically in the accompanying drawings.

BRIEF DESCRIPTION OF THEFIGURES

FIG. 1 is a perspective view of a prior condenser blade assembly.

FIG. 2 is a top view of the prior art condenser blade assembly of FIG. 1.

FIG. 3 is a side view of the prior art condenser blade assembly of FIG. 2 along arrow 3A.

FIG. 4 is a bottom perspective view of a first preferred embodiment of a three condenser blade assembly of the invention.

FIG. 5 is a side view of the three blade assembly of FIG. 4 along arrow 5A.

FIG. 6 is a perspective view of the three blade assembly of FIGS. 4 5.

FIG. 7 is a perspective view of a single twisted condenser blade for the assembly of FIGS. 1 3 for a single blade used in the 19'' blade assemblies.

FIG. 8 is a top view of a single novel condenser blade of FIG. 7.

FIG. 9 is a root end view of the single blade of FIG. 8 along arrow 9A.

FIG. 10 is a tip end view of the single blade of FIG. 8 along arrow 10A.

FIG. 11 shows a single condenser blade of FIGS. 7 10 represented by cross-sections showing degrees of twist from the root end to the tip end.

FIG. 12 shows an enlarged side view of the blade of FIG. 10 with section lines spaced approximately 1 inch apart from one another.

FIG. 13 is a bottom view of a second preferred embodiment of a two condenser blade assembly.

FIG. 14 is a bottom view of a third preferred embodiment of a four condenser blade assembly.

FIG. 15 is a bottom view of the three condenser blade assembly of FIGS. 4 8.

FIG. 16 is a bottom view of a fourth preferred embodiment of a five condenser blade assembly.

FIG. 17 is a bottom view of a fifth preferred embodiment of an asymmetrical configuration of a five condenser blade assembly.

FIG. 18 is a top view of the asymmetrical configuration blade assembly of FIG. 17.

FIG. 19 is a side view of a prior art commercial outdoor air conditioning compressor unit using the prior art condenser fan blades of FIGS. 1 3.

FIG. 20 is a cross-sectional interior view of the prior art commercial air conditioning compressor unit along arrows 20A of FIG. 19 showing the prior art blades of FIGS. 1 3.

FIG. 21 is a cross-sectional interior view of the compressor unit containing the novel condenser blade assemblies of the preceding figures.

FIG. 22 is a side view of a preferred embodiment of an outdoor air conditioning compressor unit with modified diffuser housing.

FIG. 23 is a cross-sectional interior view of the diffuser housing inside the compressor unit of FIG. 22 along arrows 23A.

FIG. 24 is a cross-sectional interior view of another embodiment of the novel diffuser housing inside the compressor unit of FIG. 22 along arrows 23A.

FIG. 25 is a cross-sectional interior view of another embodiment of a novel diffuser housing with both a conical outwardly expanding convex curved diffuser wall, and a hub mounted conical center body.

FIG. 26 is a cross-sectional bottom view of the housing of FIG. 25 along arrows F26.

FIG. 27 is an enlarged view of the wall mounted vortex shedding control strip of FIG. 25.

FIG. 28 is a top perspective view of the housing of FIG. 25 along arrow F28.

FIG. 29 is a top view of another embodiment of a porous foam strip along either or both a blade tip edge or a blade trailing edge.

FIG. 30 is another cross-sectional view of another embodiment of the compressor housing of FIG. 25 with blade rotation temperature control unit.

FIG. 31 is a condenser fan speed control flow chart for use with the blade rotation temperature control unit of FIG. 30.

FIG. 32 is a bottom perspective view of another preferred embodiment of a three condenser blade assembly of the invention.

FIG. 33 is a side view of the three blade assembly of FIG. 32 along arrow 33A.

FIG. 34 is a top view of a single condenser blade of FIGS. 32 33.

FIG. 35 is a tip end view of the single blade of FIG. 34 along arrow 35A.

FIG. 36 is a side view of the single blade of FIG. 35 along arrow 36A.

FIG. 37 is a bottom perspective view of still another preferred embodiment of a three condenser blade assembly of the invention.

FIG. 38 is a side view of the three blade assembly of FIG. 37 along arrow 38A.

FIG. 39 is a top view of a single condenser blade of FIGS. 37 38.

FIG. 40 is a tip end view of the single blade of FIG. 39 along arrow 40A.

FIG. 41 is a side view of the single blade of FIG. 40 along arrow 41A.

FIG. 42 is a graph of performance with ECM motors in the fan embodiments in condenser airflow (cfm) versus motor power (Watts).

FIG. 43 is a graph of impact of the reduced blade tip clearance from use of the foam strip of the fan embodiments in condenser airflow (cfm) versus motor power (Watts).

FIG. 44 is a graph of the impact on sound of the fan embodiments in condenser airflow (cfm) versus sound pressure level (dBA).

FIG. 45 is a graph of relative fan performance of the fan embodiments in condenser airflow (cfm) versus motor power (Watts).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before explaining the disclosed embodiments of the present invention in detail it is to be understood that the invention is not limited in its application to the details of the particular arrangements shown since the invention is capable of otherembodiments. Also, the terminology used herein is for the purpose of description and not of limitation.

Unlike the flat planar stamped metal blades that are prevalent in the prior art as shown in FIGS. 1 3, the subject invention can have molded blades that can be twisted such as those formed from molded plastic, and the like.

Novel fan blades attached to a condenser hub can rotate at approximately 840 rpm producing approximately 2200 cfm of air flow and 2800 cfm at 1100 rpm.

The standard stamped metal blades in as shown in the prior art of FIGS. 1 3 can produce approximately 2200 cfm with approximately 190 Watts of power at approximately 1050 rpm.

The improved fan of the invention with the improved diffuser and with exactly the same OEM 6-pole 1/8 hp PSC motor produced approximately 2610 cfm with approximately 195 Watts of power at approximately 1100 rpm. Direct power savings areapproximately 45 Watts (an approximately 24% drop in outdoor unit fan power).

Our tests showed that the novel fan blades with the improved diffuser can also be slowed from approximately 1100 to approximately 850 rpm and still produce approximately 1930 cfm of air flow with only approximately 110 Watts, an approximately 51%reduction in fan power for non-peak conditions. The lower rpm range with an engineered diffuser results in substantially quieter fan operation approximately 14 dB lower sound. Another fan was designed which provides a 40 W power savings than thestandard fan, but without the sound reduction advantages.

For a typical 3-ton heat pump, total system power (compressor, indoor and outdoor fans) would typically drop from approximately 3,000 Watts at design condition (95 O.D., 80,67 IDB/IWB) to approximately 2950 Watts with the new fan, anapproximately 2% reduction in total cooling power. For a typical heat pump consumer with approximately 2,000 full load hours per year, this would represent an approximately $10 savings annually. The fabrication of the fan assembly is potentiallysimilar to fabricated metal blades so that the payback could be virtually immediate. Additionally, the condenser fan motor can also be less loaded than with the current configuration improving the motor life and reliability. When coupled with anelectrically commutated motor (ECM), the savings are approximately doubled.

When the fan blades are coupled to an ECM motor, the measured savings increase from roughly 45 Watts to approximately 100 Watts with the test apparatus. Not only are saving increased, but it is then possible with the ECM motor to varycontinuously the motor speed without sacrificing its efficiency. Within the preferred embodiment of the invention, the fan speed would be low (approximately 750 rpm) when the temperature outdoors was less than a factory preset level (e.g. 90 F). Thiswould provide greatest fan power savings (greater than approximately 110 Watts) as well as very quiet operation during sensitive nighttime hours and other times when occupancy and neighbors are likely to be outdoors. However, when the temperature wasabove approximately 90 F, the ECM motor could move to a higher speed (e.g. approximately 1000 rpm) where the produced air flow would result in greatest air conditioner efficiency and cooling capacity with fan-only power savings still greater thanapproximately 80 Watts.

Thus, this control scheme would provide both maximum AC efficiency in the hottest periods as well as most quiet operation at other times which is highly desirable for home owners.

Thus, the invention achieves a significant performance improvement that can be readily adaptable to use within current lines of unitary air conditioners to cut outdoor AC unit fan power by approximately 24% or more over standard condenser fanblade assemblies.

The novel invention embodiments can provide power savings with little change in the cost of the fans and also provide substantially better flow at low speed operation which is something the better motors cannot provide.

Condenser Fan Assemblies with Twisted Blade

FIG. 4 is a bottom perspective view of a first preferred embodiment of a three condenser blade assembly 100 of the invention. FIG. 5 is a side view of the three blade assembly 100 of FIG. 4 along arrow 5A. FIG. 6 is a perspective view of thethree blade assembly 100 of FIGS. 4 5.

Referring to FIGS. 4 6, a central hub 90 can include a bottom end 95 for attaching the assembly 100 to standard or novel condenser housing which will be described later in reference to FIGS. 19 23. The central hub can include a top end and sides92 on which three novel twisted blades 10, 20, 30 can be mounted in an equally spaced configuration thereon. For example, the blades can be spaced approximately 120 degrees apart from one another. The blades 10, 20, 30 can be separately molded andlater fastened to the hub 90 by conventional fasteners as described in the prior art. Alternatively, both the novel blades 10, 20, 30 and hub 90 can be molded together into the three blade assembly 100.

Table 1 shows the comparative performance of the novel condenser fan 19'' blades AC-A@, AC-B@, and 27.6'' blades AC-5@, and AC-D and AC-E blades compared to standard 19'' and 27.6'' condenser fans. All fans were tested for flow with anexperimental set up in accordance with ASHRAE ANSI Standard 51-1985 "Laboratory Methods of Testing Fans for Ratings." A setup was used with an outlet chamber setup with the calibrated nozzle on one end of the chamber. Power was measured with acalibrated watt hour meter with a resolution of 0.2 Watts. Condenser sound levels were measured for the fan only in accordance with ARI Standard 270-1995 using a precision sound meter with A-weighting.

TABLE-US-00001 TABLE 1 Comparative Performance of Air Conditioner Fans Against Conventional Models (External Fan Static Pressure =