Patent Publication Number: US-4319521-A

Title: Air distribution system

Description:
REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of U.S. patent application Ser. No. 944,134, filed on Sept. 20, 1978. That application is related to U.S. patent application entitled &#34;Branch Take-Off And Silencer For An Air Distribution System&#34;, Ser. No. 944,133 filed on Sept. 20, 1978 which is now U.S. Pat. No. 4,182,430. The related application is incorporated by reference herein. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     The field of this invention is air distribution systems, and more particularly air handling units for air distribution systems for multiple story buildings. 
     Conventional air distribution systems for buildings typically include an air handling unit having discrete functional elements coupled together in series at a central location in the building. By way of example, such a unit might include an input plenum for mixing outside and return air, a filter bank, a conditioner unit (for heating and cooling), an airflow silencer, a fan and an output silencer. Generally, the various units are provided with rectangular cross-section geometry and outer packaging. 
     In multiple story building applications, a horizontal interconnection of all of these discrete elements typically requires relatively large space on a floor, and also requires a high velocity (and hence lossy) elbow interconnection between the output silencer and the vertical main distribution duct of the system. For air handling units having vertical interconnection of the discrete elements, a multiple story housing is typically required. 
     In addition to the relatively large space requirements for conventional systems, the various units impose severe floor loading constraints. There are also restrictive fan power constraints (due to relatively high losses in the silencers and through elbow connections). The serial combination of elements, interspersed with conventional silencers, requires several high-to-low and low-to-high air velocity changes. Such configurations have relatively high energy requirements for achieving the velocity control. Furthermore, the dispersed element configuration establishes a correspondingly dispersed source of noise, particularly in view of the generally rectangular geometry typically used for the various elements. In addition, each of the elements provide acoustical paths for transmission of noise to the rest of the building. 
     In typical applications, the conventional systems may be roof mounted, with each of the series-connected units having relatively large rectangular cross-section enclosures, and separate access doors for servicing. In severe weather environments, such systems are difficult to service, due to the number of separate elements which must be accessed, and the relatively large area in which the elements are dispersed. 
     It is an object of the present invention to provide an energy efficient air handling unit. 
     Another object is to provide a space efficient air handling unit. 
     Still another object is to provide an air distribution system with improved silencing characteristics. 
     SUMMARY OF THE INVENTION 
     Briefly, the present invention is directed to an air distribution system for a building. The system includes a mixing plenum for receiving and mixing outside and return air. An input flow concentrator and integral silencer is disposed within and coupled to the mixing plenum. The flow concentrator and integral silencer is adapted to establish a substantially axially symmetrical flow path for air from the plenum to an output port. A fan is coupled to the output port to drive the air from the output port to the main duct for distribution throughout the building. 
     In one form of the invention, the input flow concentrator and silencer includes inner and outer sections which are coaxial about a central axis. The outer section has a substantially conical inner surface which is disposed about the substantially conical outer surface of the inner section. In alternative embodiments, the inner and outer sections may be generally similar in shape but have polygonal cross-sections. The polygonal cross-section forms of the invention are considered to be axially symmetrical in the description below. 
     The flow concentrator and silencer has a substantially annular input port and an output port. The mean radius of the output port is less than that of the input port. To provide this configuration, the inner and outer sections are mutually separated so that their opposing surfaces define a flow path characterized by a substantially annular cross-section (with either circular, or elliptical or polygonal boundaries) which is coaxial with the central axis. The flow path has a decreasing mean radius from the annular input port to the output port. 
     In these forms of the invention, the flow concentrator includes an integral silencer. The silencer is provided by the inner and outer sections which have acoustically absorbent material forming their opposing surfaces. In accordance with the invention, further silencing may be provided by silencers distributed throughout the building. In some forms, the silencers may be conventional in-line silencers positioned in various branch ducts. In other forms combination branch take-off/silencers may be utilized in the form described in the incorporated reference. 
     Generally, the combination branch take-off and silencer apparatus couples a main supply (input) duct to one or more branch ducts and to a coaxial output duct having a similar but smaller cross-section than the input duct. In this configuration, coaxial extensions of the input and output ducts define a shell region. The shell region is closed at its downstream end and open at its upstream end to oncoming air in the input duct. The shell region is divided at that upstream end by porous acoustical material into a plurality of adjacent channels which lead to a plenum near the downstream end of the shell region. The plenum is coupled to the branch ducts. With this configuration, air is tapped from the input duct, and that air flows along the shell region to the plenum. In the plenum, the tapped air is driven into the branch duct by either static or velocity pressure, depending on the particular geometry of the take-off/silencer. The remaining airflow in the input duct continues along into the output duct. 
     In accordance with the present invention, the air handling unit may be relatively compact compared with the prior art systems providing similar airflow characteristics. The input concentrator/silencer and distributed silencers provide a high degree of noise reduction (partly due to the compact arrangement of the central air handling unit, and partly due to the axial symmetry of the air handling unit) yet are relatively efficient in terms of energy consumption. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects of this invention, the various features thereof, as well as the invention itself, may be more fully understood from the following description, when read together with the accompanying drawings in which: 
     FIG. 1 shows a top view of an air handling unit in accordance with the present invention; 
     FIG. 2 shows a side view of an air distribution system including the unit of FIG. 1, as installed in a multiple story building; 
     FIG. 3 shows an exemplary branch take-off and silencer for use in the system of FIG. 2 in accordance with the present invention; 
     FIG. 4 shows an alternative form of the air distribution system of FIG. 2; 
     FIGS. 5 and 6 show alternative exemplary flow concentrator, silencer and fan configurations for use in the system of FIG. 2; 
     FIG. 7 shows in cross-section, an alternative flow concentrator for use in the system of FIG. 2; and 
     FIG. 8 shows a sectional view of an alternative air distribution system in accordance with the present invention; and 
     FIG. 9 shows the system of FIG. 8 along section lines 9--9. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1 and 2 show an exemplary embodiment of the present invention. A multiple story building 10 is shown with a centrally located main air duct 12 vertically positioned in the core of the building. As shown, the building 10 includes a basement 14, a first floor 16 and a second floor 18. Additional floors may extend in a similar fashion. The basement 14 includes an enclosed chamber 20 which houses the principal elements for the air distribution system of building 10. 
     The air distribution system includes a conventional back draft exhaust assembly 30 including a silencer 32, axivane fan 34, back draft damper 36 and automatic adjustable louvre 38 coupled to the outside of the building. 
     In this configuration, the chamber 20 serves as the mixing plenum for outside air and return air. Return air is ducted in a conventional fashion through a silencer 26 and return duct 28 to the region 40 of chamber 20. In that region, air from the outside is drawn in through louvre 41 and joined with the return air. This mixture of outside and return air is then passed through a filter bank 42 to the region 44 within chamber 20. Both the chambers 40 and 44 function as the mixing plenum in the present embodiment. 
     The air distribution system further includes an air handling unit having input flow concentrator and integral silencer 50 and fan 51 positioned within the chamber 44. The concentrator/silencer 50 includes an outer section 52 and an inner section 54, with both sections being substantially axially symmetrical about a vertical axis 56. Concentrator/silencer 50 includes an input port 58 which extends symmetrically about the axis 56, and an output port 60. The outer section 52 is hollow and has a substantially conical inner surface. The inner section 54 has a substantially conical outer surface. The outer section 52 and inner section 54 are positioned so that their respective inner and outer surfaces establish a substantially axially symmetrical airflow path from the plenum provided by region 44, through the input port 58 to the output port 60. 
     In the present embodiment, the outer and inner sections 52 and 54 are lined with an acoustically absorbing material. With the present configuration, the flow path provided by concentrator/silencer 50 is characterized by a mean radius at input port 58 which is greater than the mean radius at the output port 60. 
     In the illustrated embodiment, cross-sections of the flow path defined by sections 52 and 54 are bounded by circles. In alternative embodiments, the sections 52 and 54 may be configured so that cross-sections of the flow path provided by those elements have boundaries which are elliptical, or alternatively polygonal. In such embodiments, although the inner and outer surfaces of elements 52 and 54, respectively, are not strictly speaking conical, for the present invention, such surfaces are effectively conical and are intended to be embraced within the meaning of the claims of this application. 
     An axivane fan 52 and associated ducting are coupled between the output port 60 of concentrator/silencer 50 and the main duct 12. In the present embodiment, a bank of heat exchange coils 64 is disposed adjacent to the input port 58. These coils may be conventional elements adapted to fit the particular dimensions of port 58, and may be used to conventionally condition (i.e. heat or cool) the air entering input port 58. In alternative embodiments, the filter bank 42 may take the form of filter elements mounted directly on the outer surfaces of the heat exchange coil bank 62. 
     The present embodiment includes a combination branch take-off and silencer 70 for the first floor 16 and a similar branch take-off and silencer 72 with the second floor 18 for supplying conditioned air from duct 12. In this embodiment, the branch take-off/silencers 70 and 72 are substantially of the form shown in the incorporated reference, with an exemplary form of one of those branch take-off and silencers shown in FIG. 3 of this application. In that figure, the reference designations are the same as those used in the incorporated reference. 
     In alternative forms of the invention, conventional static pressure operated, single function branch take-off elements may be used together with a conventional silencer in the various branch ducts. In both of the above configurations, the distributed silencers throughout the building provide a substantial lessening of the noise. 
     FIG. 4 shows an alternative configuration in accordance with the present invention, which is substantially similar to that shown in FIGS. 1 and 2 but wherein the air handling unit is mounted on roof 76 of the building and the main duct 12 extends downward to a branch take-off and silencer 78. In FIG. 4, the elements corresponding to elements in FIGS. 1 and 2 are denoted with identical reference numerals. 
     In FIG. 4, the flow concentrator 50 includes an inverting section 80 in addition to the other elements shown in the configuration of FIGS. 1 and 2. The mixing plenum is established by a generally cylindrical housing 82. With this configuration, a compact roof mounted unit is provided with the inverting section 80 arranged to efficiently feed the return and outside air to the input port 58 of concentrator/silencer 50. Additional elements may also be housed within the single housing 82, such as heating and condensing calls and other alternative elements conventionally requiring separate enclosures. Thus, a single access may be utilized to service the entire air handling unit. This form of the invention is particularly useful in applications in extreme environments. 
     FIG. 5 shows an alternative form for the input concentrator/silencer 50, fan 62 and heat exchange bank 64, where the fan 50 is an axivane fan having a blade assembly (indicated schematically by blade 82) which may be selectively controlled to drive from either of motors 84 (which is in a conventional configuration for an axivane fan with the motor in the same housing with the fan blade) or a separate motor 86 coupled at the other end of the drive shaft 88. In this configuration, energy efficiency of the system may be enhanced by selectively operating either of motors 86 and 88, depending on the demands on the air distribution system. 
     FIG. 6 illustrates in schematic form, an alternative form for the input concentrator/silencer and fan assembly and the heat exchanger bank. In this form, a centrifugal fan 90 of conventional form is shown with output port 92 for coupling to the main duct 12. Input ports for the fan 90 are shown by reference designations 94 and 96. With this conventional fan, two input flow concentrators/silencers 100 and 102 are shown coupled to the input ports 94 and 96, respectively, of fan 90. 
     Both concentrators/silencers 100 and 102 may be substantially the same form as that shown in FIGS. 1 and 2 for input concentrator/silencer 50. In FIG. 6, elements of concentrator/silencers 100 and 102 which correspond to similar elements of the concentrator/silencer 50 and heat exchanger bank 64 in FIG. 2 are denoted by identical reference numerals. 
     FIG. 7 shows a cross-section of an alternative form for the input concentrator/silencer 50 and heat exchanger bank 64 of the embodiment of FIGS. 1 and 2. Elements of FIG. 7 similar to elements in FIG. 2 are denoted by similar reference numerals. In FIG. 7, the outer and inner sections 52 and 54 include two stage surfaces. Although the upper portion of the outer surface of inner section 54 is substantially cylindrical as shown in FIG. 7, the overall effect of that outer surface (i.e. including the lower portion of that surface) is to provide a substantially conical surface. Furthermore, the overall flow path defined by the inner and outer surfaces of elements 54 and 52, respectively, in FIG. 7 is still an axially symmetrical airflow path from the input port 58 to the output port 60. 
     FIGS. 8 and 9 show a sectional view of portions of the air distribution system of the present embodiment adapted for installation in a multiple story building similar to building 10 shown in FIGS. 1 and 2. However, in the present embodiment, the building 10 is fitted with four return ducts 101-104 (shown in dotted lines in FIG. 9) which extend in the building core substantially parallel to a vertical duct 112. Only ducts 102 and 104 are shown in the sectional view of FIG. 8. The return ducts 101-104 are coupled to an enclosed chamber 120 in the lowermost floor. In the illustrated embodiment, each return duct is coupled to an associated one of fans 101a 104a for driving air through the ducts downward into chamber 120. 
     The system of FIGS. 8 and 9 further includes an air handling unit having an input flow concentrator an integral silencer 150 and axial fan 162. The fan 162 is adapted to drive air upwards through duct 112. The concentrator/silencer 150 includes an outer section 152 and an inner section 154, with both sections being substantially axially symmetrical about a vertical axis 156. Concentrator/silencer 50 includes an input port 158 which extends symmetrically about the axis 56, and an annular output port 160 output port 160 which extends symmetrically about axis 156. The outer section 152 and inner section 154 define an axially symmetrical input flow path for air entering with a substantially radial flow pattern through port 158 and exiting with a substantially axial flow pattern from port 160. 
     In the present embodiment, the outer and inner sections 152 and 154 are lined with an acoustically absorbing material. The concentrator/silencer 150 is shown in section to illustrate the acoustically absorbing material and the air flow path through that element. In the present embodiment, cross-sections of the flow path defined by sections 152 and 154 are bounded by circles. In alternative embodiments, the sections 152 and 154 may be configured so that cross-sections of the flow path have boundaries which are polygonal. For the purposes of this invention, such flow paths are considered to be substantially axially symmetrical where the polygonal deviation from circular is relatively small. 
     In the present embodiment, a bank of heat exchange coils 164 is positioned adjacent to the input port 158. These coils may be conventional elements adapted to fit the particular dimensions of port 15B and may be used to conventionally condition the air entering the input port 158. In addition, a bank of filter elements 166 is positioned adjacent to the bank of heat exchange coils 164. 
     The chamber 120 is divided into two regions (181a and 181b) by a partition 180. The partition 180 houses four damper assemblies 181-184 (only damper assemblies 181 and 182 are shown in FIG. 8). Damper assemblies 181-1B4 are adapted to permit passage of air from the return ducts 101-104 into the lower region 181a from upper region 181b. An exhaust air duct 188 is coupled to the upper region 181b to provide a flow path for expelling excess return air from ducts 101-104 (i.e. the air entering from ducts 101a-104a which is not passed through damper assemblies 181-184). 
     An outside air input duct 190 extends from the outside to the interior of chamber 120. Duct 190 includes a pair of tapered branch portions 191 and 192 (only 191 is shown in FIG. 8) extending on either side of the main duct 112. The tapered ducts 191 and 192 include a set of elongated slits on their upper surfaces, thereby permitting a series of exit ports for outside air to pass from duct 190 through ducts 191 and 192 and into the lower region 181a of chamber 120. This lower portion 181a of chamber 120 serves as a mixing region for the outside air provided by duct 190 and the return air provided by way of dampers 181-184 from ducts 101-104. With this configuration, highly efficient mixing occurs in the region 181a. The mixed air is then drawn through the filter bank 166 and heat exchange coil bank 164 and the integral concentrator/integral silencer, fan 162 and into duct 112 for distribution through the building. 
     It will be understood that the main duct 112 may include one or more branch take-off and silencers. In this embodiment, the branch take-off silencers are substantially of the form shown in the incorporated reference, with an exemplary form of one of those branch take-off and silencers shown in FIG. 3 of this application. In that figure, the reference designations are the same as those used in the incorporated reference. 
     The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.