| Orifice boundary layer suction method and system -> Monitor Keywords |
|
|
  Orifice boundary layer suction method and systemUSPTO Application #: 20070015455Title: Orifice boundary layer suction method and system Abstract: An air-conveying device for use in an HVAC system having an interior surface and an exterior surface. An air-moving device is arranged and disposed to move air through the air-conveying device adjacent to the interior surface of the air-conveying device. The air-conveying device conveys air having passed through an HVAC heat exchanger. The air-conveying device includes one or more openings disposed and arranged to provide a pressure differential sufficient to cause passage of air through the openings from an area adjacent to the interior surface to an area adjacent to the exterior surface in order to decrease aerodynamic drag. (end of abstract) Agent: Mcnees Wallace & Nurick, LLC - Harrisburg, PA, US Inventors: John Terry Knight, Anthony William Landers, Stephen Blake Pickle USPTO Applicaton #: 20070015455 - Class: 454292000 (USPTO) Related Patent Categories: Ventilation, Having Inlet Airway, Including Specific Air Distributor (e.g., Register, Etc.), Ceiling Type The Patent Description & Claims data below is from USPTO Patent Application 20070015455. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] The present invention is related to devices for conveying air. In particular, the present invention is directed to a diffuser and/or orifice for use in HVAC heat exchanger units. BACKGROUND OF THE INVENTION [0002] HVAC systems will typically include a heat exchanger unit having a fan arranged to pass air over a heat exchanger. As air is discharged from the unit, the air typically passes through a diffuser/orifice. The diffuser/orifice is a device that permits the passage of air out of a heat exchanger. Diffuser/orifices are typically fabricated with a geometry, which results in less backpressure and an increased airflow. One drawback of the diffuser/orifice is that the flow at or near the diffuser/orifice surface experiences undesirable flow characteristics. In particular, the fluid near the surface of the diffuser/orifice experiences boundary layer formation. Boundary layer separation may also occur further increasing the thickness of the boundary layer region. [0003] Air passing over flat surfaces may flow in a laminar flow profile. Laminar flow profiles experience low drag and results in larger, desirable flow rates. A boundary layer forms as a result of friction between the air and the surface. The boundary layer thickness is defined as the locus of points where the velocity parallel to the flow surface reaches 99% of the mean stream velocity. Therefore, the thicker a boundary layer is, the less area there is available for flow at maximum velocity when passing through the orifice. Separation of the boundary layer from the surface, called boundary layer separation, causes recirculation and/or turbulent flow. Boundary layer separation is a particular problem in applications where the flow of a fluid diverges. In diffusers, boundary layer separation may occur as air passes out of the unit and experiences an air pressure differential. Diverging flow typically occurs when the flow of air out of the heat exchanger unit is diffused through a diffuser/orifice having a flared outlet. The diverging flow provides a reduction in air pressure, which also reduces backpressure against the fan, but may increase the amount of undesirable turbulent flow and susceptibility to boundary layer separation. Air traveling out of a heat exchanger unit through a diffuser/orifice may experience an adverse pressure gradient along the surface of the orifice. The result is that the boundary layer breaks away or separates from the orifice surface forming a broad pulsating wake. [0004] Another type of known diffuser/orifice device is a cylindrical orifice, which conveys air from spaces within heat exchanger units to outside of the heat exchanger units. In diffuser/orifice devices having a substantially cylindrical geometry, the air passing through the cylinder has a relatively large boundary layer. The large boundary layer is due to the friction between the air and the surface of the cylinder. The shape of the entrance to the cylinder plays a large role in determining the eventual thickness of the boundary layer. A smooth and curved orifice entrance will result in less resistance to fluid flow through the orifice. Sharp edges at the orifice entrance result in increased resistance to flow. This resistance is due to the formation of a large boundary layer region that forms just past the orifice entrance. The large boundary layer is susceptible to boundary layer separation and/or turbulent flow, particularly at larger flow rates. In addition, the cylindrical geometry results in a backpressure against the fan that decreases the quantity of air flowing through the diffuser orifice. [0005] As the boundary layer is drawn away from the surface of the diffuser/orifice, the flow loses at least a part of the laminar flow profile and becomes more turbulent. Turbulent flow has increased drag at the surface, has a lower airflow rate and increases backpressure against the fan. The turbulent flow characteristics of the boundary layer are undesirable for heat exchanger unit applications because a significant amount of energy present in the fluid is lost to aerodynamic drag and recirculation of the turbulent flow. The fan blades may extend at least a portion of the way into the orifice. This extension places the tips of the fan blades within this turbulent region rendering this portion of the blade less efficient and may result in increased fan noise. As a result, the fan requires a greater amount of energy to move the air through the diffuser/orifice. [0006] What is needed is a system and method for decreasing the amount of boundary layer separation and/or turbulent flow occurring in orifice/diffusers in order to more efficiently move air out of a heat exchanger unit. SUMMARY OF THE INVENTION [0007] The invention includes an air-conveying device for use in an HVAC system having an interior surface and an exterior surface. An air-moving device is arranged and disposed to move air through the air-conveying device adjacent to the interior surface of the air-conveying device. The air-conveying device conveys air having passed through an HVAC heat exchanger. The air-conveying device includes one or more openings disposed and arranged to provide a pressure differential sufficient to cause passage of air through the openings from an area adjacent to the interior surface to an area adjacent to the exterior surface in order to decrease aerodynamic drag. [0008] Another embodiment of the invention includes a method for reducing aerodynamic drag in an air-conveying device. The method includes providing an air-conveying device having an interior and exterior surface. A flow of air is provided with an air-moving device from a heat exchanger through the air-conveying device and along the interior surface. Flow of a portion of air through the air-conveying device is permitted from an area of higher pressure air adjacent to the interior surface to an area of lower pressure air adjacent to the exterior surface through openings in the air-conveying device to reduce aerodynamic drag. [0009] An advantage of the present invention is that the air flowing through the diffuser/orifice experiences reduced boundary layer separation because the boundary layer is drawn closer to the surface of the diffuser/orifice. The reduction in boundary layer permits the air to flow through the diffuser/orifice in a substantially laminar flow profile, reducing the backpressure against the fan and decreasing the power required by the fan to exhaust the air out of the heat exchanger unit. [0010] Another advantage of the present invention is that the fan capacity in a heat exchanger unit may be decreased without decreasing the total amount of airflow through the system. [0011] Another advantage of the present invention is that cylindrical diffuser/orifices may be used with substantially the same fan power requirements as diffuser/orifices having a flared geometry, and without the expensive manufacturing costs associated with flared diverging outlet diffuser/orifices. [0012] Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS [0013] FIG. 1 schematically illustrates a cutaway view of a known diffuser/orifice system. [0014] FIG. 2 schematically illustrates a cutaway view of an embodiment of the present invention. [0015] FIG. 3 schematically illustrates a cutaway view showing airflow through a diffuser/orifice of the present invention. [0016] FIG. 4 schematically illustrates a profile of airflow over a surface of a diffuser/orifice of the present invention. [0017] FIG. 5 schematically illustrates a perspective view of an embodiment of the present invention. [0018] FIG. 6 schematically illustrates a perspective view of an alternate embodiment of the present invention. [0019] FIG. 7 schematically illustrates a cutaway view of a known diffuser/orifice system. [0020] FIG. 8 schematically illustrates a cutaway view of an alternate embodiment of the present invention. Continue reading... Full patent description for Orifice boundary layer suction method and system Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Orifice boundary layer suction method and system patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Orifice boundary layer suction method and system or other areas of interest. ### Previous Patent Application: Ventilator Next Patent Application: Exhaust vent bird guard Industry Class: Ventilation ### FreshPatents.com Support Thank you for viewing the Orifice boundary layer suction method and system patent info. IP-related news and info Results in 2.74867 seconds Other interesting Feshpatents.com categories: Tyco , Unilever , Warner-lambert , 3m |
||
