Patent Publication Number: US-2022221188-A1

Title: Fan powered exhaust hood

Description:
FIELD 
     This disclosure relates to an air handling unit of a heating, ventilation, air conditioning and refrigeration system, particularly to directing exhaust out of the air handling unit. 
     BACKGROUND 
     Air handling units typically include an exhaust fan in a cabinet space where return air is received from a building. The exhaust fan directs some of the return air towards an exhaust damper section, through an exhaust damper, and out of the air handling unit through an exhaust hood. 
     BRIEF SUMMARY 
     In an air handling unit, the air from the return air duct is drawn through an exhaust damper by a fan mounted on a wall in the air handling unit, and expelled through an exhaust hood. The fan draws air into a chamber connected to the exhaust hood or the exhaust hood itself, where it exits the air handling unit. This design provides a shorter required length and more efficient use of space by removing a traditional blower as the exhaust fan, and placing the fans into the space already provided for the exhaust hood. 
     Air handling unit embodiments may include a return air inlet, a wall having a first side facing the return air inlet chamber and a second side facing away from the return air inlet chamber, and fans mounted on the second side of the wall. In air handling unit embodiments, the fans have inlets on the first side of the wall. An exhaust hood is attached to an outside of the air handling unit. The fans may be one or more fans, or three fans or six fans. In an embodiment, the fans are arranged in one horizontal row of three. In an embodiment, the fans are arranged in two horizontal rows of three, with the two rows being vertically offset from one another. Each of the horizontal rows may be in a separate exhaust hood. Each of the fans may be a motorized impeller including a fan wheel, a motor, and a variable-frequency drive. 
     Rooftop air handling unit embodiments include a return air inlet, a chamber in fluid communication with the return air inlet, the chamber defined in part by a first wall. In rooftop air handling unit embodiments, the first wall has a first side facing the return air inlet chamber and a second side facing away from the return air inlet, with one or more fans mounted on the first wall such that they extend outwards on the second side of the wall. In rooftop air handling unit embodiments, the one or more fans each have an inlet in fluid communication with the first side of the wall. In rooftop air handling unit embodiments, an exhaust hood in fluid communication with the outlets of the one or more fans is mounted on an outside of the air handling unit. In rooftop air handling unit embodiments, a mixbox damper is located on a second wall of the chamber, the mixbox damper providing fluid communication between the chamber and a mixbox. In rooftop air handling units, there is a supply blower and a coil located between the mixbox and the supply blower. In rooftop air handling unit embodiments, there is a supply air outlet in fluid communication with a conditioned space. In rooftop air handling unit embodiments, the first wall may be a back wall of the air handling unit. In rooftop air handling unit embodiments, the exhaust hood may be mounted on the back wall of the air handling unit. In rooftop air handling unit embodiments, a filter may be located between the mixbox and the coil. 
     A method embodiment for directing airflows within an air handling unit of a heating, ventilation, air conditioning, and refrigeration (HVACR) system includes drawing an exhaust airflow including a portion of a return air flow through an exhaust damper, using one or more fans positioned cantilevered on a wall of the air handling unit, and directing the exhaust airflow into an exhaust hood. The wall may be a wall of the air handling unit that divides the inside of the air handling unit from the outside of the air handling unit. The exhaust hood may contain the fans. The air may pass through a screen in the exhaust hood as it exits the air handling unit. Each of the fans may be a motorized impeller including a fan wheel, a motor, and a variable-frequency drive. There may be multiple exhaust dampers. Each exhaust damper may be associated with one or more of the fans. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  shows a schematic of an air handling unit embodiment having one exhaust hood. 
         FIG. 1B  shows a schematic of an air handling unit embodiment wherein there are two exhaust hoods, stacked on top of one another. 
         FIG. 2  shows a schematic of another air handling unit embodiment. 
         FIG. 3  shows a motorized impeller used in an embodiment. 
         FIG. 4  shows airflow through the air handling unit shown in  FIG. 1A  during operation. 
         FIG. 5  shows airflow through the air handling unit shown in  FIG. 2  during operation. 
         FIG. 6  shows a prior art air handling unit. 
     
    
    
     DETAILED DESCRIPTION 
     Air handling units for heating, ventilation, air conditioning and refrigeration (HVACR) units receive a flow of return air from the building to which they provide conditioned air. At least a portion of this return air flow is exhausted from the air handling unit. 
       FIG. 1  shows a schematic of an air handling unit embodiment from a side view. The air handling unit  10  is part of a HVACR system providing air to a conditioned space, for example, a rooftop HVACR unit providing air to a building. Return air duct  12  brings air from the conditioned space into the air handling unit  10 . The air from the return air duct  12  travels through a return air inlet  14  and enters a return inlet air chamber  16  of the air handling unit  10 . On a back wall  18  of the air handling unit  10 , which in part defines return inlet air chamber  16 , there are one or more exhaust dampers  20 . Fan  22  is located cantilevered on a portion of the back wall  18  outside of return inlet air chamber  16 . An exhaust hood  24  encloses fan  22  and receives air drawn through an exhaust damper  20  by fan  22 . The outlet of fan  22  is in fluid communication with the exhaust hood  24 . The damper(s)  20  are shown on the inlet side of fan(s)  22 . It will be appreciated that the damper(s)  20  may be located on the a surface of the exhaust hood  24  where the fan(s)  22  blow air through the damper(s)  20 . In the embodiment shown in  FIG. 1 , air that is not drawn through the one or more exhaust dampers  20  and exhausted via the exhaust hood  24  instead travels into mixbox  26  through mixbox damper  28 , where it may combine with outdoor air brought in through outdoor air damper  30 , then travels through filter  32 , coil  34 , supply fan  36 , into discharge plenum  38  and ultimately is provided to the conditioned space, such as a building, through supply air outlet  40 . 
     Return air duct  12  is a duct carrying air from the conditioned space into the air handling unit. Return air duct  12  receives air from the conditioned space serviced by the HVACR system including air handling unit  10 , and directs the air back towards and into the air handling unit  10 . 
     Return air inlet  14  is located where the return air duct  12  opens into air handling unit  10 . The return air inlet  14  may be at the end of the return air duct  12 . Air from return air duct  14  enters return inlet air chamber  16  of the air handling unit  10 . Return inlet air chamber  16  may be located between a back wall  18  of the air handling unit  10  and the mixbox  26  of the air handling unit  10 . It will be appreciated that the fan(s) and damper(s) may be located on another wall other than the back wall  18  (e.g. side wall, top wall) A mixbox damper  28  may control flow of air between the return inlet air chamber  16  and mixbox  26 . An exhaust damper  20  may, in part, control flow between the return inlet air chamber  16  and exhaust hood  24 . 
     Back wall  18  is a back wall of the air handling unit  10 . Back wall  18  may divide the inside of the air handling unit  10 , including return inlet air chamber  16 , from the outside of the air handling unit  10 . Exhaust hood  24  may be mounted on an outside side of back wall  18 , opposite the return inlet air chamber  16  receiving air from return air duct  14 . Back wall  18  may be formed from foam injected panels, with structural supports foamed in. In an embodiment, additional structural supports may be foamed into the panels and/or joined to the panels using adhesives. 
     Exhaust damper  20  may be located between the return inlet air chamber  16  and the exhaust hood  24 . In an embodiment, exhaust damper  20  may be located on a surface of exhaust hood  24 , and air may be blown through exhaust damper  20  into exhaust hood  24  by fan  22 . In an embodiment, the exhaust damper  20  is located at an inlet of fan  22  and air is drawn through the exhaust damper into fan  22 . There may be more than one exhaust damper, for example with the exhaust dampers arranged along the back wall  18  aligned in the vertical direction of the back wall  18  and arranged in a line extending in the horizontal direction of the back wall  18 . In the view shown in  FIGS. 1A and 1B , the horizontal direction of the back wall  18  extends into and out of the page. 
     Fan  22  may be, for example, a motorized impeller or a direct drive fan. There may be one or more fans located on back wall  18 . One or more fans  22  may be located with an inlet facing an exhaust damper  20 . In an embodiment, there are an equal number of fans  22  and exhaust dampers  20 , and each individual fan  22  has its inlet facing an individual exhaust damper  20 . Fan  22  may be powered by, for example, a variable speed electric motor. In an embodiment, fan  22  is powered by a motorized impeller. In an embodiment, fan  22  is powered by an electrically communicated motor. In an embodiment, fan  22  is an axial fan. The one or more fans may be in one or more rows in the horizontal direction of the back wall  18 . For example, there may be a single horizontal row of three fans  22  mounted on back wall  18  and extending into exhaust hood  24 . In an embodiment, fan  22  and exhaust damper  20  may be located on a side wall of the air handling unit  10 . 
     Exhaust hood  24  encloses one or more of the fans  22 . Exhaust hood  24  has an opening  42  through which exhaust air may leave the air handling unit  10 . The opening  42  may be, for example, at the bottom of the exhaust hood  24 , such that the exhaust air travels downwards as it leaves the exhaust hood  24 . It will be appreciated that the opening  42  may be in other locations. In an embodiment, the opening  42  may be located on the side of the exhaust hood  24 . It will also be appreciated that the damper(s)  20  may be located where the opening  42  is. The opening may be covered by a screen, grate, filter, etc. in order to prevent unwanted material such as, for example, debris, animals, etc. from entering the air handling unit  10 . There may be multiple exhaust hoods  24  forming a horizontal line across, with each exhaust hood receiving air from one or more of the fans  22 . 
     Mixbox  26  is where outside air may enter the air handling unit  10  through outdoor air damper  30 , and where the portion of the return air that is not drawn into exhaust hood  24  may be mixed with outside air before continuing through the air handling unit  10 . 
     Filter  32  is a filter through which the air passes before being circulated over the coil  34  and eventually into the building serviced by the HVACR system including air handling unit  10 . Coil  34  heats or cools the air traveling through the air handling unit  10 . Coil  34  is, for example, a heat exchanger through which a fluid travels to exchange heat with the air in air handling unit  10 . 
     In the embodiment shown in  FIG. 1A , return air inlet chamber  16  is in fluid communication with exhaust hood  24  through exhaust damper  20 . In an embodiment, exhaust damper  20  is located on a wall of return air inlet chamber  16 . In an embodiment, return air chamber  16  does not contain a blower. 
     Air passing through coil  34  is drawn into and driven by supply fan  36 , which expels air into discharge plenum  38 . Discharge plenum  38  is connected to supply air outlet  40 , which carries air into the building serviced by the HVACR system including the air handling unit  10 . 
       FIG. 1B  shows a side view of a variation of the embodiment of  FIG. 1A  in which there are two separate exhaust hoods, first exhaust hood  24 A and second exhaust hood  24 B, mounted vertically displaced from one another. The first exhaust hood  24 A and second exhaust hood  24 B are each mounted on back wall  18 . First one or more fans  22 A may draw air from return inlet air chamber  16 , through back wall  18 , through first exhaust damper  20 A, and into the first exhaust hood  24 A. Second one or more fans  22 B may draw air from return inlet air chamber  16 , through back wall  18 , through second exhaust damper  20 B and into the second exhaust hood  24 B. Air may be exhausted from exhaust hood  24 A via opening  42 A. Air may be exhausted from exhaust hood  24 B via opening  42 B. The one or more fans in each exhaust hood may be arranged in horizontal rows. In an embodiment, one or more fans  22  in each exhaust hood  24  are arranged in a vertical column. For example, each of first exhaust hood  24 A and second exhaust hood  24 B may contain a horizontal row of three fans  22 A and  22 B, respectively. Air that is not drawn into the first exhaust hood  24 A or second exhaust hood  24 B may enter mixbox  26  through mixbox damper  28 , where it may mix with outside air entering through outside air damper  30 , then travel through filter  32 , coil  34 , and then be driven by supply fan  36  into discharge plenum  38  and into the building via supply air outlet  40 . 
       FIG. 2  shows a side view of a schematic of an embodiment of an air handling unit. Air handling unit  50  includes the return air duct  12  and return air inlet  14  as shown and described in  FIG. 1 . One or more fans  22  may be mounted on diagonal wall  52 , drawing air into the space  54  defined by wall  52  and back wall  18 . Air in space  54  may travel through openings  56  into exhaust hood  24 , and leave the air handling unit  50  via the exhaust hood  24 . 
     Diagonal wall  52  runs from a position at the floor of the air handling unit  50  between the return air duct  14  and the back wall  18  towards a position at the ceiling of the air handling unit  50  and away from the back wall  18 , towards the mixbox  26 . Diagonal wall  52  separates space  54  from the return air duct  14  and mixbox damper  28 . In an embodiment, diagonal wall  52 =extends the full height of the air handling unit, from the floor to the ceiling. In an embodiment, diagonal wall  52  connects to a sidewall and/or the wall supporting mixbox damper  26 , while separating the exhaust path from the path of the return air inlet  14  to the return or mixbox damper  28 . Diagonal wall  52  may extend from one side wall of the air handling unit to another. Diagonal wall  52  and back wall  18  of the air handling unit  50  define a space  54 . 
     One or more fans  22  are mounted on diagonal wall  52 . The one or more fans are mounted such that their inlet is towards the return inlet air chamber  16  receiving return air from the return air duct  14 , and that their outlet is towards the space  54 . The fans  22  draw a portion of the air within return inlet air chamber  16  into space  54 . This may pressurize the air in space  54 . 
     Air leaves space  54  through openings  56  which connect space  54  with the exhaust hood  24 . In the embodiment shown in  FIG. 2 , the outlets of the one or more fans  22  are in fluid communication with the exhaust hood  24  via openings  56 . Air then leaves air handling unit  50  through an opening  42  in the exhaust hood  24 . Exhaust hood  24  may include screens, grates, filters, etc. to prevent the entry of unwanted material, such as, for example, debris, animals, etc. into the air handling unit  50  through the opening  42 . There may be multiple exhaust hoods  24 , arranged horizontally in a line or vertically displaced from one another, for example as shown in  FIG. 1B . Each exhaust hood  24  may exhaust air from one or more openings  56  between space  54  and the exhaust hood  24 . 
     Air that is not drawn into the space  54  may enter mixbox  26  through mixbox damper  28 , mix with outside air entering through outside air damper  30 , then travel through filter  32 , coil  34 , and then be driven by supply fan  36  into discharge plenum  38  and into the building via supply air outlet  40 . 
       FIG. 3  shows a motorized impeller  70  which may be used in an embodiment as a variable speed electric motor of one or more of the fans  22 . The motorized impeller includes inlet  72 , fan wheel  74 , integrated motor  76 , and variable-frequency drive  78 . 
     Inlet  72  is an opening through which air can be drawn into the motorized impeller  70 . Motorized impeller  70  may be mounted on a back wall  18  or a diagonal wall  52  of an air handling unit  10  or  50 . The inlet  72  may be positioned towards the return inlet air chamber  16  that receives return air flow through the return air inlet  14 . 
     Fan wheel  74  includes the blades. Fan wheel  74  is driven by integrated motor  76 . Integrated motor  76  is located partially within the fan wheel. This positioning of the motor may provide a more compact design for the motorized impeller  70 . The integrated motor may be an electric motor. The integrated motor  76  may be a brushless electric motor, for example an electronically commutate (EC) motor. The integrated motor  76  drives fan wheel  74  such that the blades of the fan wheel draw air through the inlet  72  and expel the air on the opposite side of back wall  18  or diagonal wall  52  from the inlet  72 . 
     Variable-frequency drive  78  controls the integrated motor  76  to achieve a desired fan speed. The fan speed at which integrated motor  76  is operated affects the amount of air that is drawn through the motorized impeller  70  and exhausted via the exhaust hood  24 . The variable frequency drive  78  may be connected to a controller  80  providing the desired fan speed at which to operate the integrated motor  76 . The desired fan speed may be based on, for example, pressure within the building having the HVACR system including the air handling unit  10  or  50 . 
       FIG. 4  shows airflow through the embodiment shown in  FIG. 1 . Return air flow  90  travels towards the air handling unit  10  through return air duct  12 . The return air flow  90  travels through into air handling unit  10 . A portion  92  of return air flow  90  is drawn through the fans  22  located on back wall  18 . The portion  92  exits the fans  22  inside of exhaust hood  24 . Airflow  92  leaves the exhaust hood  24  through an opening  42 , for example at the bottom of the exhaust hood  24 . Return air that is not part of the portion  92  drawn by the fans  22  into exhaust hood  24  forms airflow  96 , entering the mixbox  26  through mixbox damper  28 , where it mixes with outside airflow  98  drawn in through outside air damper  30 . The combined airflow  100  then travels through filter  32 , coil  34 , and then is driven by supply fan  36  into discharge plenum  38  as supply airflow  102 , which then travels into the building via supply air outlet  40 . 
       FIG. 5  shows airflow through the embodiment shown in  FIG. 2 . Return air flow  110  travels towards the air handling unit  50  through return air duct  12 . The return air flow  110  is deflected by diagonal wall  52  and travels along diagonal wall  52 . A portion  112  of the return air flow  110  is drawn in by the fans  22 . The portion  112  is expelled into space  54  between diagonal wall  52  and the back wall  18  of the air handling unit  50 . Airflow  114  in space  54  travels through one or more openings  56  in the back wall  58  of the air handling unit  50 , into the exhaust hood  24 . Airflow  116  leaves the exhaust hood  24  via one or more openings  42 , for example at the bottom of the exhaust hood  24 . Return air that is not part of the portion  112  drawn by the fans  22  into space  54  forms airflow  118 , entering the mixbox  26  through mixbox damper  28 , where it mixes with outside airflow  120  drawn in through outside air damper  30 . The combined airflow  122  then travels through filter  32 , coil  34 , and then is driven by supply fan  36  into discharge plenum  38  as supply airflow  124 , which then travels into the building. 
       FIG. 6  shows a prior art air handling unit. Air enters the air handling unit  150  via the return air duct  12 . Air from the return air duct is driven by exhaust fan  152 , directing a portion into exhaust chamber  154 . Exhaust chamber  154  may be pressurized by the portion of air directed into it from exhaust fan  152 . Air in exhaust portion  154  may travel through exhaust damper  20  into exhaust hood  24 , and exit the air handling unit  150  via an opening  42  in the exhaust hood  24 . Prior art air handling unit  150  requires an additional exhaust chamber  154  and must accommodate exhaust fan  152 , causing it to be longer and less space-efficient than the present invention. In the prior art embodiment shown in  FIG. 6 , air that is not directed into exhaust chamber  154  then travels through the mixbox damper  28  into the mixbox  26  where it may be mixed with outside air drawn in through outside air damper  30 , and the air from the mixbox  26  travels through filter  32 , coil  34 , into supply fan  36  which drives the air into discharge plenum  38  and then into the building via supply air outlet  40 . 
     Aspects: It is understood that any of aspects 1-8 may be combined with any of aspects 9-13 and/or aspects 14-20, and that any of aspects 9-13 may be combined with any of aspects 14-20. 
     Aspect 1: An air handling unit, comprising: 
     a return air inlet, 
     a wall, having a first side facing return air inlet chamber and a second side facing away from the return air inlet, 
     one or more fans, mounted on the wall such that they extend outwards on the second side of the wall, the one or more fans each having an inlet in fluid communication with the first side of the wall, and 
     an exhaust hood mounted on an outside of the air handling unit. 
     Aspect 2: The air handling unit according to 1, wherein the one or more fans are each motorized impellers comprising: 
     a fan wheel, 
     a motor, and 
     a variable-frequency drive controlling a speed of the motor. 
     Aspect 3. The air handling unit according to any of aspects 1-2, further comprising a damper associated with each of the one or more fans, and wherein the damper is located between the return air inlet and the inlet of a fan associated with the damper. 
     Aspect 4. The air handling unit according to any of aspects 1-3, wherein the one or more fans are three fans. 
     Aspect 5. The air handling unit according to aspect 4, wherein the three fans are located on the wall in a horizontal line. 
     Aspect 6. The air handling unit according to any of aspects 1-4, wherein the one or more fans are six fans. 
     Aspect 7. The air handling unit according to aspect 6, wherein the six fans are located on the a back wall of the air handling unit in two horizontal lines of three fans each, and wherein the horizontal lines of three fans are vertically displaced from one another. 
     Aspect 8. The air handling unit according to of aspects 1-8, wherein the wall is a back wall of the air handling unit and wherein the first side faces an inside of the air handling unit and the second side faces an outside of the air handling unit. 
     Aspect 9. The air handling unit according to aspect 8, wherein the exhaust hood is mounted on the second side of the wall. 
     Aspect 10. The air handling unit according to any of aspects 1-9, wherein at least a portion of the one or more fans extends into the exhaust hood. 
     Aspect 11. A rooftop air handling unit, comprising: 
     a return air inlet, 
     a chamber in fluid communication with the return air inlet, the chamber defined in part by a first wall, wherein the first wall has a first side facing return air inlet chamber and a second side facing away from the return air inlet, 
     one or more fans, mounted on the first wall such that they extend outwards on the second side of the wall, the one or more fans each having an inlet in fluid communication with the first side of the wall, 
     an exhaust hood mounted on an outside of the air handling unit, 
     a mixbox damper, located on a second wall of the chamber, the mixbox damper providing fluid communication between the chamber and a mixbox, 
     a supply blower, 
     a coil, located between the mixbox and the supply blower, and 
     a supply air outlet in fluid communication with a conditioned space. 
     Aspect 12. The rooftop air handling unit according to aspect 11, wherein the first wall is a back wall of the air handling unit having a first side facing an inside of the air handling unit and a second side facing an outside of the air handling unit. 
     Aspect 13. The rooftop air handling unit according to any of aspects 11-12, wherein at least a portion of the one or more fans extend into the exhaust hood. 
     Aspect 14. The rooftop air handling unit according to any of aspects 11-13, further comprising a filter located between the mixbox and the coil. 
     Aspect 15. A method of exhausting air from an air handling unit, comprising: 
     drawing an exhaust airflow including a portion of a return air flow through an exhaust damper, using one or more fans positioned cantilevered on a wall of the air handling unit, and 
     directing the exhaust airflow into an exhaust hood. 
     Aspect 16. The method according to aspect 15, wherein the exhaust hood surrounds the one or more fans. 
     Aspect 17. The method according to any of aspects 15-16, wherein the exhaust airflow exits the air handling unit through a screen in the exhaust hood. 
     Aspect 18. The method according to any of aspects 15-17, wherein each of the one or more fans is a motorized impeller comprising: 
     a fan wheel, 
     a motor, and 
     a variable-frequency drive controlling a speed of the motor. 
     Aspect 19. The method according to any of aspects 15-18, wherein the exhaust damper is associated with one of the one or more fans. 
     Aspect 20. The method according to any of aspects 15-19, wherein the wall divides an interior of the air handling unit from an exterior of the air handling unit. 
     The examples disclosed in this application are to be considered in all respects as illustrative and not limitative. The scope of the invention is 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 intended to be embraced therein.