Patent Application
20150377249
The field of this disclosure relates generally to a diffuser for use in an air handling system, and more specifically, to a diffuser for directing and expanding the cross-sectional area of an airstream circulating in a heating, ventilating, and air conditioning (HVAC) system.
Some HVAC systems include portions of the system that increase the cross-sectional area of the airstream, such as where the airstream exits a blower assembly. However, as the area of the airstream increases, the velocity decreases, i.e., the downstream air loses momentum. Since airstream pressure is inversely proportional to airstream velocity, the pressure in the airstream increases as the velocity decreases. This non-ideal expansion and subsequent increases in pressure generate adverse flow structures. The term “adverse flow structures” designates flow structures in an airstream that have negative effects on HVAC system operation, such as recirculation, vortexes, turbulence, and eddies. These adverse flow structures and the increased pressure result in energy losses for the HVAC system and, therefore, decrease the efficiency of the system. The energy losses are more pronounced in HVAC systems without expansion or transition pieces to optimally change the cross-sectional area of the airstream.
Diffusers are commonly used as expansion or transition pieces for expanding the cross-sectional area of airstreams flowing through HVAC systems. Diffusers are coupled with exhaust outlets or duct sections. Instead of an immediate change in cross-sectional area, traditional diffusers use an inclined wall to gradually change the cross-sectional area. However, in some HVAC systems the airstream separates from the inclined wall causing areas of low pressure, i.e., vacuum pockets, along the inclined wall. Higher-pressure air recirculates to fill the vacuum pockets, resulting in the generation of unfavorable flow structures in the airstream.
Additionally, it is sometimes necessary to change the direction of an airstream in an HVAC system at the same location as a change in cross-sectional area, for example, when the airstream exits the blower assembly. The change in direction also causes the airstream to separate from a wall of the HVAC system and the separation generates unfavorable flow structures.
In one aspect, a diffuser for expanding the cross-sectional area of an airstream comprises an inlet comprising an inlet cross-sectional area and an outlet comprising an outlet cross-sectional area. The outlet cross-sectional area is greater than the inlet cross-sectional area. A curved sidewall extends from the inlet to the outlet and at least partially defines an inner passageway. The curved sidewall comprises a convex portion and a concave portion. The convex portion is adjacent the inlet and the concave portion is adjacent the outlet.
In another aspect, a method for expanding and directing an airstream in a diffuser comprises channeling an airstream through a diffuser. The airstream is channeled into the diffuser through an inlet. The airstream has a first cross-sectional area when the airstream enters the diffuser at the inlet. The diffuser includes a first curved wall with a first curve and a second curve. The airstream is channeled in a first direction along the first curve of the first curved wall. The cross-sectional area of the airstream is expanded to a second cross-sectional area as the airstream moves along the first curved wall. The airstream is channeled in a second direction as the airstream moves along the second curve of the first curved wall. The airstream is exhausted from an outlet.
In yet another aspect, an air handling system comprises a diffuser, a radial blower configured to move an airstream and a blower housing configured to house the blower and channel the airstream around the blower. The blower housing includes a blower outlet configured to exhaust the airstream. The diffuser comprises a curved wall, a diffuser inlet configured to receive the airstream from said blower, and a diffuser outlet configured to exhaust the airstream. The diffuser comprising a first cross-sectional area at the diffuser inlet and a second cross-sectional area at the diffuser outlet. The second cross-sectional area is greater than the first cross-sectional area. The curved wall includes a first curve and a second curve.
Described below are a diffuser with a curved wall and a method of using a diffuser with a curved wall. The diffuser with a curved wall can simultaneously change the cross-sectional area and the direction of an airstream. The curved wall redirects the airstream prior to expanding the cross-sectional area, which helps the airstream maintain a laminar flow along the curved wall, i.e., the airstream does not separate from the curved wall. The curved wall also smoothly transitions the airstream to a new direction while minimizing separation of the airstream from the curved wall and maintaining a substantially constant air pressure along the curved wall. The separation of the airstream from a traditional diffuser wall causes unfavorable flow structures and inefficient flow of the airstream. Therefore, by maintaining a laminar flow, the diffuser's curved wall increases the efficient flow of the airstream and minimizes the generation of unfavorable flow structures.
In the exemplary embodiment, the cross-sectional area of interior space 18 gradually increases from diffuser inlet 20 to diffuser outlet 22. Sidewalls 12 are spaced equidistant from each other along their entire area. Top wall 14 and curved bottom wall 16 are coupled between sidewalls 12 and spaced a varying distance from each other. The distance between curved bottom wall 16 and top wall 14 increases from diffuser inlet 20 to diffuser outlet 22. In the exemplary embodiment, top wall 14 is flat along its entire area. In alternate embodiments, top wall 14 and sidewalls 12 are curved and/or inclined.
In the exemplary embodiment, first curved portion 24 has an upper radius Ru. In one embodiment, upper radius Ru gradually changes along first curved portion 24 to enable an airstream (not shown) to follow first curved portion 24. In the exemplary embodiment, second curved portion 28 has a lower radius RL. In one embodiment, lower radius RL gradually changes along second curved portion 28 to enable the airstream to follow second curved portion 28. In another suitable embodiment, the shape of first curved portion 24 and second curved portion 28 may be based on mathematical formulas to give first curved portion 24 and second curved portion 28 an elliptical, parabolic, or other mathematical curve shape.
In the exemplary embodiment, housing 134 includes a first sidewall 142 and an opposite second sidewall 144. First sidewall 142 and second sidewall 144 are generally flat, parallel sidewalls disposed at axially opposite ends of fan impeller 136. Outer peripheries 146 of both first sidewall 142 and second sidewall 144 are shaped substantially the same and generally form a volute shape. A scroll wall 148 is coupled between first sidewall 142 and second sidewall 144. More specifically, scroll wall 148 is coupled to outer periphery 146 of first sidewall 142 and second sidewall 144, thereby forming an increasing expansion angle for airstream 140 through housing 134 around fan impeller 136.
Housing 134 includes an air inlet opening 150 provided in first sidewall 142. First sidewall 142, second sidewall 144, and scroll wall 148 define, at least in part, an air outlet opening 152. In the exemplary embodiment, blower assembly 132 exhausts airstream 140 through air outlet opening 152. Further, motor 138 of blower assembly 132 is disposed in air inlet opening 150 and is coupled to housing 134. In an alternate embodiment, second sidewall 144 includes an opening (not shown) to facilitate accommodating motor 138.
In the exemplary embodiment, diffuser 110 includes a turning vane 156 having two vane panels 158, 160 spaced apart to enable a portion of airstream 140 to pass between vane panels 158, 160. Each vane panel 158, 160 includes a metal plate extending between and coupled to sidewalls 112. Vane panel 158 angles in relation to the direction of airstream 140 to direct airstream 140 towards vane panel 160 and curved bottom wall 116; the angle between vane panel 158 and the direction of airstream 140 is an acute angle, i.e., an angle between 0° and 90°. In contrast, vane panel 160 curves similar to curved bottom wall 116 to facilitate airstream 140 expanding efficiently and following curved bottom wall 116. In an alternate embodiment, diffuser 110 includes any number of turning vanes 156 having any size, shape, and material that enables turning vanes 156 to function as described herein. For example, in an alternate embodiment, a turning vane (not shown) could have a vane panel with a straight angled section similar to vane panel 158 and a curved section similar to vane panel 160. Furthermore, in an alternate embodiment, turning vane 156 is coupled to housing 134 and/or diffuser 110. Additionally, turning vane 156 may be used independently of diffuser 110 in any section of an HVAC system to direct an airstream.
In the exemplary embodiment, curved bottom wall 116 has a first curved portion 124, a straight portion 126, and a second curved portion 128 similar to first curved portion 24, straight portion 26, and second curved portion 28 of diffuser 10. In alternate embodiments, one or more of sidewalls 112 and top 214 are curved.
In operation, fan impeller 136 rotates to draw air into housing 134 through air inlet opening 150 and generates high velocity airstream 140 that is exhausted from air outlet opening 152 into diffuser 110. After exiting housing 134, airstream 140 enters diffuser 110 through diffuser inlet 120 and is exhausted through diffuser outlet 122. The cross-sectional area of diffuser 110 gradually increases from diffuser inlet 120 to diffuser outlet 122. As airstream 140 flows through diffuser 110, airstream 140 expands to fill the larger cross-sectional area of diffuser outlet 122.
In the exemplary embodiment, as seen in
Curved top wall 364 has a first curved portion 366, a straight portion 368, and a second curved portion 370. First curved portion 366 is located adjacent diffuser inlet 320 and gradually curves away from curved bottom wall 316. From the reference of interior space 318, first curved portion 366 is convex. Straight portion 368 extends between first curved portion 366 and second curved portion 370. Second curved portion 370 is located adjacent diffuser outlet 322. From the reference of interior space 318, second curved portion 370 is concave. In the direction of airstream 340 through diffuser 310, the distance between curved bottom wall 316 and curved top wall 364 increases. In alternate embodiments, sidewalls 312 curve similar to curved bottom wall 316 and curved top wall 364.
In the exemplary embodiment, diffuser 310 is coupled to a blower assembly 332 adjacent diffuser inlet 320. Blower assembly 332 forces airstream 340 into diffuser inlet 320. Additionally, diffuser 310 is coupled to a duct assembly 372 adjacent diffuser outlet 322. Accordingly, airstream 340 enters diffuser inlet 320, travels through interior space 318, and exits through diffuser outlet 322. After exiting diffuser 310 through diffuser outlet 322, airstream 340 enters duct assembly 372.
While passing through diffuser 310, airstream 340 follows the curves of both curved top wall 364 and curved bottom wall 316 to maintain its velocity as the cross-sectional area of diffuser 310 gradually increases. Following curved bottom wall 316, airstream 340 flows along first curved portion 324 to straight portion 326, follows straight portion 326 until it reaches second curved portion 328, and is gradually redirected. Following curved top wall 364, airstream 340 flows along first curved portion 366 to straight portion 368, follows straight portion 368 until it reaches second curved portion 370, and is gradually redirected again. Second curved portions 328, 370 curve airstream 340 to a desired direction for exiting diffuser 310 through diffuser outlet 322. Alternate embodiments may include any number of curved walls. Two or more curved diffuser walls allow for a greater change in area without generating more adverse flow structures and inefficiencies. Additionally, a combination of multiple curved walls can each include less of a curve and still efficiently change the airstream cross-sectional area.
Additionally, curved bottom wall 416 has a horizontal curve 474 in a direction perpendicular to the direction airstream 440 travels. Curved bottom wall 416 has a middle line 476 located equidistant from sidewalls 412 and curved bottom wall 416 curves up from middle line 476 to both sidewalls 412 to form horizontal curve 474, which is a general U-shape. Specifically, horizontal curve 474 is concave from the reference of interior space 418. Due to horizontal curve 474, airstream 440 flows across the entire width of curved bottom wall 416 without being backed up or trapped in corners. In alternate embodiments, horizontal curve 474 of curved bottom wall 416 may have other curved and straight configurations without departing from features of this disclosure. For example, an alternate diffuser (not shown) may have curved sections adjacent its sidewalls and a flat section extending between the curved sections. Alternately, a diffuser (not shown) comprising one horizontally curved sidewall that forms a general cylinder shape could also curve in the direction of an airstream.
In the exemplary embodiment, horizontal curve 474 has a horizontal radius RH. In one embodiment, horizontal radius RH varies along the horizontal direction of horizontal curve 474. Horizontal curve 474 may be based on a mathematical formula to give curved bottom wall 416 an elliptical, parabolic, or other mathematical curve shape. In other embodiments, horizontal curve 474 may have a circular shape, where horizontal radius RH is constant along all of horizontal curve 474.
Exemplary embodiments of the diffuser are described above in detail. The diffuser and its components are not limited to the specific embodiments described herein, but rather, components of the systems may be utilized independently and separately from other components described herein. For example, the components may also be used in combination with other machine systems, methods, and apparatuses, and are not limited to practice with only the systems and apparatus as described herein. Rather, the exemplary embodiments can be implemented and utilized in connection with many other applications.
Although specific features of various embodiments of the disclosure may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the disclosure, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing.
This written description uses examples to disclose the invention, including the best mode, and to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
