Patent Publication Number: US-2004046038-A1

Title: Blending air apparatus

Description:
PRIOR APPLICATION  
     [0001] This application is a continuation of my co-pending patent application Ser. No. 10/237,276 filed Sep. 9, 2002 for Blended Air Machine (BAM). 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0002] 1. Field of the Invention  
       [0003] This invention pertains to air handling systems as generally in the HVAC field, and more specifically to improvements in air blending apparatus for blending different air streams for use in ventilation.  
       [0004] 2. Description of the Prior Art  
       [0005] Heating, ventilation and air conditioning systems (HVAC) for various building structures frequently require the mixing together of at least two different air streams before final conditioning and distributing the combined air flow through building air ducts. The two air streams most often mixed in an air handling system are return air that is recirculated back from inside the building, and fresh or makeup air brought into the unit from the outside ambient. Seasonal weather conditions produce a wide range of outside air temperatures from the winter cold to extremely hot summer conditions. In inefficient prior systems, the inherent momentum of the moving air streams tends to keep air streams of different temperature stratified in layers, producing false sensor readings and improper control of dampers proportioning the intake air inflow of the respective air streams.  
       [0006] Another problem is that various equipment and building machinery generate large heat loads and environment pollution in factories, assembly plants and other industrial and commercial buildings, and such machinery is often located in poorly ventilated small machine rooms. Even large plant areas are difficult to ventilate at a reasonable cost and can stay very hot all year round, and poor ventilation is known to adversely affect equipment and worker performance. Although thorough admixing of fresh outside air with recirculated inside air has been attempted in the past by using so-called mixing chambers, in actual practice the prior art devices do little more than coadunate the two streams.  
       BRIEF SUMMARY OF THE INVENTION  
       [0007] The invention is embodied in an air blending apparatus for air distribution in an enclosed building space comprising a housing having at least two air inlet chambers with controllable air inlets for proportioning the intake flow of recycled return room air and fresh ambient air in separate air streams, a common air blending chamber receiving the air streams and being constructed and arranged for the intimate intermixing and blending thereof, and air moving means for distributing the mixed, blended air to the enclosed space.  
       [0008] The invention is further embodied in the parts and the combinations of parts hereinafter described and claimed.  
       [0009] The principal object of the invention is to provide a blended air apparatus for mixing two different temperature air streams and produce a consistent volume of evenly blended, temperature controlled, air in an air handler system.  
       [0010] Another object is to blend separate air streams in an intimate manner to produce a selected temperature composite air flow for an air delivery system.  
       [0011] Another object is to provide an air blending unit that in the winter will blend an intake of relatively warm return air and an intake of relatively cold fresh ambient air and eliminate stratification thereof; and in other seasons will re-proportion the return and ambient air intake to thereby obtain optimum air temperatures for seasonal conditioning and ventilation of an enclosed building space.  
       [0012] These and other objects and advantages will become more apparent hereinafter.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0013] In the accompanying drawings, like numerals refer to like parts wherever they occur:  
     [0014]FIG. 1 is a perspective view showing a blended air apparatus embodying the invention,  
     [0015]FIG. 2 is a cross-sectional elevation of the blended air apparatus to illustrate the internal air chambers, dampers and baffles,  
     [0016]FIG. 3A is a view similar to FIG. 2, but showing the alternate maximum air flow patterns,  
     [0017]FIG. 3B is a view similar to FIG. 3A but showing a representative air flow blending pattern in the air blending apparatus, and  
     [0018]FIG. 4 is a diagrammatic view of the blended air apparatus as typically installed for air distribution to an enclosed space. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0019] This application is a continuation of my co-pending parent patent application Ser. No. 10/237,276 filed Sep. 9, 2002 for Blended Air Machine (BAM), that I prepared and filed pro se and the disclosure of which is incorporated by reference herein in its entirety. It may be noted that the drawings of the parent application include specific dimensions, as well as legends, in a best embodiment showing of my invention.  
     [0020] An air blending apparatus  20  embodying the present invention is shown mounted in an air handler or distribution system  10  for providing conditioned air to the selected enclosed space S of building B. Referring first to FIG. 4, the air distribution system  10  is diagrammatically illustrated for environmental purposes as being mounted at or near ceiling C, below roof R and adjacent to outside wall W of the building B. As illustrated, the basic components of the air handler system include an ambient or fresh air intake ductwork  11  having an intake filter rack  12  through which fresh ambient air is drawn from outside the building into the air blending apparatus  20 , generally at inlet  13 . Recycled return air from inside the building B is drawn into the air blending apparatus  20 , generally at inlet  14 . The intake of these separate air streams and the blending thereof will be described in greater detail.  
     [0021] The air blending apparatus also has an air delivery or discharge outlet, generally at  15 , that is connected by mating collar  16  to a direct drive axial fan (not shown) in fan housing  17 , which fan delivers a continuous output of high volume of conditioned air (i.e. 5000 CFM) to the main air distribution duct  18  for discharge into the enclosed space S through a suitable grill or duct openings  19 . A control panel  21  is suitably located for operating the apparatus, as will appear.  
     [0022] Referring now to FIGS.  1 - 3 , the air blending apparatus  20  comprises a main housing or cabinet  22  having a return air intake section  24 , an outside or fresh air intake section  26 , a central air blending section  28  and an outlet or air discharge section  30 . The return air section  24  forms a return intake air chamber  32  with its inlet  14  being open or otherwise connected to the enclosed space S from which room air is recirculated back through to the return air inlet  14  into the apparatus  20  in a typical negative pressure flow created by the primary air mover  17 , as is well known to those skilled in the art. The amount of return air entering the return air chamber  32  is controlled by ganged sets of normally closed horizontally extending dampers  34 . These dampers  34  are of the type having opposed pairs of blades  35  that are reversely acting to move from a first in-line planar relationship when fully closed to a second variable angled relationship during modulation toward open (as shown), and finally to a third parallel relationship when fully open. In the second or intermediate modulation position, the blades  35  form a series of tapering air passages or throats that, with the high speed fan  17 , contribute to an increased air velocity therethrough. The return air inlet  14  is shown as being on a horizontal top wall area of the housing  22 , but it will be understood that the inlet  22  could be constructed and arranged in a side wall ( 44  or  45 ) of the return air section  32 . Similarly, the fresh outside air section  26  forms a fresh air intake chamber  36  with its inlet  13  being connected to the fresh air intake ductwork  11  through which fresh ambient air is drawn into the air blending apparatus  20 . The amount of fresh ambient air entering the chamber  36  is controlled by ganged sets of normally closed vertically extending dampers  37 . These dampers  37  also have opposed pairs of blades  38  that are reversely acting to move from fully closed first in-line positions through second variable angled positions to a third fully open position, as described with reference to the blades  35 . The return air chamber  32  and make-up air chamber  36  both communicate directly to the central air blending section  28  at the upper region thereof. Air mixing driving damper modulation takes place generally in the control area of the air blending section  28 . The air discharge section  30  has a discharge chamber  39  that communicates with the lower area of the central air blending section  28  and has a circular discharge outlet  15  that accommodates the mating collar  16  connecting the fan housing  17 .  
     [0023] A principal feature of the invention is to provide for the intimate blending of the two separate incoming air streams from the return air intake chamber  32  and the fresh air intake chamber  36 . The air blending section  28  is centrally positioned in the main housing  22  and defines a main air intermixing and blending chamber  40  having its upper air inlet zone defined in part by air flow directing baffle means; namely, return air flow baffle  42  and fresh air flow baffle  43 . The return air baffle  42  is constructed and arranged to slope angularly from side wall  44  of the return air chamber  32  toward the opposed chamber side wall  45  and constricts air flow across line “a” as shown in FIG. 2. The baffle  42  has an air control surface  46  that is substantially aligned with the vertical center of the fresh air intake dampers  37 . Thus, the surface  46  slants directly toward the middle of the incoming fresh air flow in air chamber  36 , and the baffle  42  creates a plenum effect in the return air intake chamber  32  when the dampers  34  are fully open. The fresh air flow baffle  43  is also constructed and arranged to slope angularly from a side wall  47  of the fresh air chamber  36  toward the opposed chamber wall  48  and constrict air flow across line “b” (FIG. 2) to create a plenum effect in the fresh air chamber  36  when the dampers  37  are fully open. The angularity of the air control surface  49  is directed across the central chamber  40  to downstream of point “a” on the return air control surface  46  of baffle  42 .  
     [0024] Still referring to FIG. 2, the central chamber  40  is defined, in part, by opposed side walls  52  and  53  having substantially the same air flow cross-sectional area dimension as at the respective points “a” and “b”, and it may be noted that the outflow area from the central chamber  40 , at “c” in FIG. 2, is substantially the same as at “a” and “b” where an outflow baffle  56  is also formed in part by side wall  52 . Air flow is thus channeled to the air outflow or discharge chamber  39  which has a circular discharge outlet  15  from a square housing section  30 , whereby a further plenum effect is created back through the central chamber  40 .  
     [0025] The two opposed-blade sets of air dampers  34  and  37  at the return air inlet  14  and fresh air inlet  13  are reversely operated as through a bell-crank linkage  62  having crank arms (not shown) connected to the drive shafts  34   a ,  37   a  of the respective sets of dampers  34 ,  37 . This provides synchronized operation of both dampers in reversely opening and closing modulation. In one form of motor control for the dampers, a proportional modulation motor (not shown) may be mounted directly to one of the damper drive shafts ( 34   a ,  37   a ), and has a spring return that biases that damper to the closed position. It may also be noted that because of the reverse volume of air intake through both air inlets  34 ,  37  will be approximately the same and will not exceed the maximum volume that can be achieved through either inlet. Thus, because of the baffling constriction (at “a”-“b”-“c”), the volumetric air flow through the central chamber  40  will be controlled and less than the maximum intake potential since the cross-sectional area of either intake  34 ,  37  exceeds the cross-sectional area of the central chamber duct. Opposed sets of temperature sensors  64  are positioned in the air outflow section  39  for sensing the temperature of discharge air, and the control panel  21  has an electronic thermostat (not shown) receiving the sensed air temperature readings and is programmed to drive the actuator motor  60  to operate the dampers  34 ,  37 .  
     [0026] In operation each set of dampers  34  and  37  can be modulated from the first fully closed air blocking position to the third fully open (100%) air intake position. When one damper ( 34 ) is fully open, the other ( 37 ) is fully closed. The air blending apparatus  20  is designed to maximize the supply of fresh (oxygenated) outside air into the building space S for dissipation of excessive machinery heat and fumes and ventilation of dead air spaces in and around such machinery. It is known that the temperatures in such enclosed building spaces can often exceed 120° F. Thus, in spring-summer-fall operations when outside air temperatures may exceed a typical set point temperature in the range of 65° F. to 70° F.—and even reach summer heats of 100° F.—it is desirable to employ 100% fresh outside air to ventilate the building space. When the inside air temperature is 5° F. or more higher than the outside air temperature and exceeds the sensed set point temperature, the position of the respective dampers will generally be modulated in an intermediate range such as 40% open to 60% open to selectively proportion the return and fresh air to maintain supply air temperature set point. When the inside return air temperature drops below the set point, the fresh air inlet will be modulated closed to reflect up to 100% supply of return air. The reversely acting linkage  62  establishes a variable air intake ratio between the two inlets  13 ,  14  and is essential in providing an unrestricted flow of proportioned air to the main fan  17  for distribution. The dampers  34  and  37  are thus driven to the preselected positions necessary to approximate or achieve set-point temperatures in normal operation. It will be understood by those skilled in the art that other sensors (not shown) of ambient and return air temperatures can also be provided, and the controller  21  may be a programmed microprocessor to achieve optimum temperature and fresh air control.  
     [0027] An important feature of the present invention is to provide for a total blending of the two incoming air streams of return and fresh air. The air control means for achieving thorough admixing and blending includes the primary baffle means  42  and  43 . The air flow directions of air entering dampers  34  and  37  is substantially perpendicular to each other, but become non-orthogonal due to baffle surfaces  46  and  49 . Due to the extreme negative draw created by the fan  17 , the entire area of the central chamber  28  is consumed by the movement of at least 5000 cfm of air transitioning through it. The smooth interior surfaces within the apparatus pose little resistance except for baffling redirection. When either damper  34  or  37  is fully 100% open (in the third position), there is minimum turbulence in the air flow through the central chamber  28 . When the dampers  34 ,  37  are modulated into second air proportioning and blending positions, the angled damper blade sets ( 35 ,  38 ) produce an increase in velocity based on the variable throat opening. Thus return air entering area  32  through damper  34  has an increase in velocity as it channels through constricting point “a” formed by baffle side  46  and wall  45 . The outside air entering area  36  through damper  37  also has a similar increase in velocity due to constricting baffle side  49  at point “b”. With the two air streams converging at different volumes, velocities and directions, varying turbulence factors will be created in the central chamber  28  and these air streams will be blended together. As the co-mingled or blended air stream is formed in the central chamber, it will be channeled past point “c” by baffle walls  52 , 53  to the discharge chamber  30  where the restricted outlet size ( 15 ) will again influence blending enhanced again by the spiral or rotational air movement created by the fan  17 . This air blending is particularly relevant during winter operations when ambient temperatures can be extremely cold (i.e. below zero) and a complete blending of even small proportions of cold air into the return air is important to avoid false sensor readings. This air stream blending is achieved through the highly turbulent air flow conditions generated by the fan  17 , the veriable velocities created by damper blades  35 , 38 , and baffle means  42 , 43 , as illustrated in FIG. 3B.  
     [0028] The invention is intended to cover changes and modifications that will be apparent to those skilled in the art, and is of the full scope of the appended claims.