US20080153409A1

US20080153409A1 - Static air mixer

Info

Publication number: US20080153409A1
Application number: US11/614,493
Authority: US
Inventors: Edward Neal Koop
Original assignee: Individual
Current assignee: Ruskin Co
Priority date: 2006-12-21
Filing date: 2006-12-21
Publication date: 2008-06-26

Abstract

A static air mixing device is provided. The mixing device includes a rectangular array of louver systems. Each louver system includes a plurality of vanes defining through flow passages therebetween. The vanes are oriented to deflect incoming air in a direction toward an immediately adjacent louver system. The combination of louver systems effects vortex flow of air downstream of the static mixing device.

Description

BACKGROUND OF THE INVENTION

Static air blenders or mixers are well known in the art. Examples of these may be found for example, in U.S. Pat. Nos. 5,632,675 4,495,858, and 6,595,848. In common, they all use a series of fixed vanes forming flow louvers therebetween. The two latter patents use vanes that radiate radially from a central portion of a flow path while the first mentioned patent apparently uses parallel vanes providing flow louvers therebetween. Some of the vanes are pitched at an angle to effect deflection of the air flowing thereby to give the air flow a lateral or sideways component of movement downstream of the vanes. The function of such devices is to effect mixing of a gas typically air, as it flows from an upstream side of the mixer to a downstream side of the mixer. Often times, the incoming air is from a plurality of streams or sources, for example, a return air stream and an outdoor or fresh air stream in an air handling system, as for example, those air handling systems used in commercial air conditioning systems.
While such devices are somewhat effective in mixing air, they do have drawbacks. For example, most duct work in which the mixing systems are installed, is rectangular. One style of mixing device uses a radially radiating vane configuration which leaves zones within rectangular duct work that are outside of the tips of the vanes. To ensure mixing flow in these zones, additional vanes are added outside of the perimeter of the centrally located radiating vanes, see, e.g., U.S. Pat. No. 6,595,848. Support for the radiating vanes to keep them from bending under the influence of the flowing air, can require extra material within the vanes because of their long length to reach the edges of the ducts. If the vanes are self supporting, the vane width may need to be large, increasing the cost to construct the vane assembly.
It is well known that for laminar flow, the flow speed of the air varies by decreasing from the center of the duct outwardly. In theory, in a round pipe, the flow velocity profile for laminar flow is that of a parabola applying further load on the central portion of the vane assembly because of the increased speed of the air at the center.
In air handling units bringing two streams of air together for mixing, one stream may have a greater volume of flow than the other. Additionally the ducts that discharge streams of air into the chamber immediately preceding the air mixer are smaller in cross-section than the chamber. These two factors can result in the stream with greater flow volume dominating the central region of flow with the stream having lesser flow volume filling in around the perimeter. Mixers with radially radiating vanes arranged in two regions of the mixer, a central region and another in the perimeter, will induce vortex airflow in one sense (e.g., clockwise) with the radiating vanes in the central region and in the opposite sense (e.g., counter-clockwise) in the region of the outer perimeter with the perimeter vanes. Although mixing can occur as described above in certain circumstances, this arrangement is not ideal for thorough mixing.

BRIEF SUMMARY OF THE INVENTION

The present invention involves the provision of an air mixing system that includes an airflow inducing device such as an air pump which can be in the form of a bladed fan or a cage blower or any other suitable air pump. The air pump is operable to induce airflow within a duct system including at least one duct. The duct system is operable to conduct flow of air to an enclosure such as a room. An air mixing system is provided that is associated with the duct and is operable to mix air flowing through or to the duct. The mixing system includes at least one mixing device having a plurality of generally rectangular louver systems in which each louver system has at least two vanes defining the louver(s) therein. Each vane has a leading edge and a trailing edge and a respective deflection surface therebetween. At least two of the louver systems in a mixing system direct air flowing to an exit side of the mixing system toward a laterally immediately adjacent louver system to induce vortex airflow on the exit side about a central axis of adjacent louver systems.
The invention also involves the provision of an air mixing system that includes a plurality of separate air feeds and an air discharge. An air pump is provided to effect movement of air through at least one of the air feeds and the discharge. A mixing system is provided and is associated with an air pump positioned flow wise between the discharge and at least one of the air feeds. The mixing system includes a generally rectangular array of a plurality of louver systems. The louver systems are arranged in a plurality of rows and columns. Each of the louver systems has a plurality of vanes and each of the vanes has a leading edge and trailing edge with a respective deflection surface therebetween. The deflection surface is preferably curved and concave in the general direction of airflow through the mixing system. Adjacent vanes in each of the louver systems define the louvers therebetween. The longitudinal axes of the vanes in one louver system are generally normal to the longitudinal axes of the vanes in a laterally immediately adjacent louver system to induce vortex airflow in the discharge. The louver systems form a generally pinwheel arrangement without the vanes being in a radially extending pattern.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a perspective view of a mixing device having four louver systems and connected to duct shown in phantom.

FIG. 2 is a fragmentary side elevation view of a portion of the mixing device with portions broken away to show details thereof.

FIG. 3 is an exploded perspective view of the mixing device as seen in FIG. 1.

FIG. 4 is a perspective view of a modified form of mixing device as seen in FIG. 1 showing additional louver systems in rectangular arrays.

FIGS. 5A-F show various configurations of louver systems and induced flows using those louver systems.

FIG. 6 is a perspective view of a mixing device associated with a duct system and an enclosure with the enclosure shown in schematic form.

Like numbers throughout the various Figures designate like or similar parts and/or construction.

DETAILED DESCRIPTION OF THE INVENTION

The reference numeral 1 designates generally an air mixer system that is operable to mix air from at least one air source and preferably a plurality of air sources 2, 3. The air sources 2, 3 can be, e.g., a fresh air feed 2 and a return air feed 3. Additional air feeds may be provided as desired. The air mixer system 1 includes at least one duct system designated generally 4 which can be a single duct or a plurality of ducts 5 connecting sources 2, 3 to an enclosure designated generally 7 which can be in the form of one or more rooms 9 in a building 8. A suitable air pump 6, such as a fan or blower is associated with the duct system 4 to induce air flow therein. The air feeds 2, 3 preferably include the ducts 5A-C, each one being connected to a respective source of air. In the illustrated structure, the feed 2 opens to the exterior of the enclosure to allow the inflow of fresh inlet air and the feed 3 is connected to a room 9 of the enclosure 7 to permit return airflow from the enclosure to a mixing device 11 for mixing with fresh inlet air. Typically, the enclosure 7 will have sufficient air leakage, either intentional or unintentional, to permit the desired amount of inlet air to be fed into the enclosure 7 and room 9.
In the illustrated structure, the mixing system 1 includes the mixing device 11 that includes a plurality of rows and columns of generally rectangular flow openings 13 within a frame 10. The frame 10 is preferably attachable to one or more of the ducts, e.g., the duct 5C. The frame has sidewalls 12A-D. The walls 12A-D may also be used to secure the mixing device 11 into the duct system 4. In the air mixing system 1 of FIG. 1, the mixer 11 is divided into four rectangular quadrants arranged in rows and columns of discreet louver systems 14A-D. The louver systems 14 are positioned about a center point 15 basically in a generally pinwheel arrangement. The depth D of the walls 12A-D is sufficient to provide enough moment of inertia to resist excessive deflection under load and to force air to flow properly through the mixing device 11 louver systems.
Each louver system 14 includes a plurality of vanes 17. The vanes 17 in each louver system 14 are arranged in generally parallel relationship and are disposed relative to the longitudinal axis A of the mixing device 11 to turn the incoming air from a infeed side 18 and direct it as desired preferably to form a vortex flow on the downstream or outfeed side 19 of the static mixer 11. The angle of inclination B from the longitudinal axis A, is best seen in FIG. 2, is greater than about 20° and preferably in the range of between about 20° and about 35° and more preferably in the range of between about 23° and about 30° as measured from a plane P between the leading edge 21 and trailing edge 22 of a vane 17. As seen, a deflection surface 23 extends between the edges 21, 22 and is concave upstream or generally facing the inlet side 18. To conserve material in the manufacture of a vane 17 and provide flow space, the backside 25 of the vane 17 is convex. Outer disposed ends 28 of the vanes 17 are secured in a suitable manner to the walls 12A-D. In a preferred embodiment, the mounting is through the use of threaded fasteners 29 which may be conveniently threaded into formed longitudinally extending channels 31. Preferably each vane 17 has a plurality of formed channels 31 so that when mounted, torque on the vanes 17 can be resisted to the degree needed to prevent turning of the vanes about their fastening points.
One or more brace structures are provided, as best seen in FIGS. 3, 4, to support interiorly positioned ends 30 of the vanes 17. As shown in FIG. 3, the brace structures include brace members 32 (FIG. 3) extending between and secured to the walls 12A-D and to each other and have a depth approximately equal to the depth D. As shown, the brace members 32 are conveniently formed as L shaped members having free ends of the brace members secured to a respective wall 12 as with screw fasteners 29. The brace members 32 are also secured together adjacent a center 15 between louver systems 14. The interior ends 30 of the vanes 17 are secured to the brace members 32, as for example, with screw fasteners 29 secured in the channels 31. The brace members 32 may be secured to the walls 12 by any suitable means such as screw fasteners described above, rivets, welding or the like. The mixer 11 may be provided with a mounting flange structure 35 secured to the leading edge of the walls 12 as for example by being formed as an integral part thereof and shaped as by bending. The flange structure 35 may be secured to a duct or other structure by screw fasteners, rivets, welding or the like. In a preferred embodiment, the walls 12, flange structure 35 and braces 32 are formed of suitable metallic material as for example steel which can be coated for corrosion resistance as for example by galvanizing, painting or the like.
The louver systems 14 are arranged in rectangular arrays in the frame 10 with the louver systems 14 being positioned in rows and columns which are preferably horizontally and vertically configured. The vanes 17 in each louver system 14 have their longitudinal axes generally parallel and have their surfaces 23 spaced from adjacent vanes 17 defining louvers 33 therebetween for gas to flow through. As shown, the louvers 33 are generally rectangular. The longitudinal axes of vanes 17 in one louver system 14 are generally normal to the longitudinal axes of vanes in at least one immediately adjacent louver system. For example, as best seen in FIG. 1, the vanes 17 in the louver system 14A are generally normal to the longitudinal axes of vanes 17 in the louver systems 14B, 14D and generally parallel to the longitudinal axes of vanes in the louver system 14C which is positioned diagonally to the louver system 14A. The angle of inclination B, as described above, of the vanes 17 in a louver system 14 is such as to redirect the flow of air from the infeed side 18 to the outfeed side 19 immediately generally only toward one immediately laterally adjacent louver system 14. This can be seen in FIG. 1 where, for example, the vanes 17 in the louver system 14A direct flow of air toward the louver system 14B which in turn directs air generally toward the louver system 14C which in turn directs the flow of air generally toward the louver system 14D and the louver system 14D in turn directs the flow of air generally toward the louver system 14A forming a generally pinwheel arrangement of louver systems 14.
As shown, the vanes 17 in each louver system 14 have their longitudinal axes generally parallel, the deflection surfaces 23 generally concentric and the planes P extending between their leading and trailing edges 21, 22, respectively, also generally parallel. However, variations may be provided to suit a specific need in a specific system. For example, the vanes 17 in a louver system may each have a different angle B of inclination. The louvers 33 between the vanes 17 are generally rectangular in shape and the flow paths or louvers 33 between the vanes 17 are directed toward an immediately adjacent louver system (non diagonal) to effect vortex flow and mixing of the fluid flowing through the mixing device 11. The air flowing through the device 11 mixes on the downstream side 19 and if the duct 5A is long enough and the flow of the air is sufficiently slow, non turbulent or laminar flow may again be achieved in the duct 5C at some point downstream of the mixing device 11. However, turbulent flow is desired at least immediately adjacent the downstream side 19 of the mixing device 11. The walls 37 of the brace members 32 divide the flow path through the mixer 11 into a plurality of distinct or separate generally rectangular flow paths.
FIGS. 5A-F shows various rectangular arrays of louver systems 14 to illustrate various flow directing configurations of louver systems and vanes 17. The arrows indicate the direction of deflection of the air flowing out of particular adjacent louver systems 14. As seen in FIG. 5A, the vortex flow would be generally counter-clockwise, arrow 50, as seen from the leading face of the mixer 11 which would be generally opposite to the clockwise rotation which would be induced by the configuration of the louver systems 14 as seen in the version shown in FIG. 1. FIG. 5B adds two additional louver systems 14 to the right hand side of that shown in FIG. 5A which induce counter-clockwise rotation in the four louver systems on the left hand side as indicated by arrow 51. By adding the two additional louver systems 14, some clockwise rotation of air flow will be induced as seen by the arrows 52 and 53. FIG. 5C, shows a square arrangement of rectangular arrays of louver systems 14 providing one counter-clockwise flow at 54 and four clockwise rotations as seen in 55, 56, 57, 58. FIG. 5D, shows a rectangular arrangement of louver systems 14 oriented in rectangular arrays providing counter-clockwise rotation at 58 and 59 and clockwise rotation at 60, 61. FIG. 5E, illustrates a rectangular array of a series of rectangular arrays of louver systems 14 showing counter-clockwise rotations at 62, and 63 and clockwise rotations at 64, 65, 66, 67 and 68. FIG. 5F, shows a square arrangement of various rectangular arrays of louver systems 14 which are arranged to effect counter-clockwise rotations at 70, 71, 72 and 73 and clockwise rotations at 74, 75, 76, 77 and 78.
It has been found that the width of the vanes is on the order of between about 4 and about 6 inches and preferably the length of the vanes is in the range of between about 6 inches and about 20 inches. The curvature of the deflection surfaces 23 is on the order of an approximate radius in the range of between about 3 inches and about 7 inches. The ratio of radius of curvature to chord length is preferably in the range of between about 0.8 and about 1.2. In a preferred embodiment, the vanes 17 can be extruded providing a generally uniform transverse cross sectional shape along the length thereof. The vanes 17 may be extruded from a polymeric material or a metallic material.
Thus, there has been shown and described several embodiments of a novel invention. As is evident from the foregoing description, certain aspects of the present invention are not limited by the particular details of the examples illustrated herein, and it is therefore contemplated that other modifications and applications, or equivalents thereof, will occur to those skilled in the art. The terms “having” and “including” and similar terms as used in the foregoing specification are used in the sense of “optional” or “may include” and not as “required”. Many changes, modifications, variations and other uses and applications of the present construction will, however, become apparent to those skilled in the art after considering the specification and the accompanying drawings. All such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention which is limited only by the claims which follow.

Claims

1. An air mixing system comprising;

at least one air pump;

at least one duct associated with the air pump, said air pump being operable to cause air to flow in the duct;

an enclosure associated with the at least one duct for receiving air therefrom;

a mixing system associated with the at least one duct and operable to mix air flowing through the at least one duct, said mixing system including at least one mixing device having a plurality of generally rectangular louver systems with each louver system having at least two vanes defining louvers, each vane having a leading edge portion and a trailing edge portion and a respective deflection surface therebetween, at least two of the louver systems directing air flowing to an exit side of the mixing system toward a laterally immediately adjacent louver system to induce vortex airflow on the exit side about a central axis of the louver system.

2. The air mixing system as set forth in claim 1 including;

a support structure; and wherein;

the vanes are mounted to the support structure in a manner forming a generally rectangular array of louver systems wherein the vanes in each of the louver systems having their longitudinal axes generally normal to the longitudinal axes of the vanes in immediately adjacent louver systems and generally parallel to longitudinal axes of vanes in a diagonally positioned louver system.

3. The air mixing system as set forth in claim 2 including at least four louver systems arranged in rows and columns.

4. The air mixing system as set forth in claim 3 wherein the vanes in each louver system define generally rectangular louvers therebetween.

5. The air mixing system as set forth in claim 4 wherein the support structure including cross brace members separating the support structure into a plurality of separate flow paths.

6. The air mixing system as set forth in claim 5 including a fresh air feed and a return air feed operably associated with an inlet side of the mixing system.

7. The air mixing system as set forth in claim 6 wherein the enclosure includes at least one room of a building.

8. An air mixing system comprising;

a plurality of separate air feeds;

a discharge;

an air pump for effecting movement of air through at least one of the air feeds and the discharge; and

a static mixing device associated with and positioned flow wise between the discharge and at least one of the air feeds said mixing device including a generally rectangular array of a plurality of louver systems, said louver systems being arranged in a plurality of rows and columns, each said louver system having a plurality of vanes, each vane having a leading edge and a trailing edge with a respective deflection surface therebetween, adjacent vanes in each louver system defining a through louver therebetween, the longitudinal axes of the vanes in one louver system being generally normal to the longitudinal axes of the vanes in laterally immediate adjacent louver system to induce vortex airflow in the discharge.

9. The air mixing system as set forth in claim 8 wherein the vanes having an angle of inclination of at least about 20°.

10. The air mixing system as set forth in claim 9 wherein at least some of the vanes having a concave air deflection surface.