Patent Publication Number: US-2012037340-A1

Title: Heat Exchange Fan Apparatus

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to heat exchange devices, and more particularly to a heat exchange device that operates to effect both circulation of and heat exchange between two fluid streams without intermixing thereof. 
     BACKGROUND OF THE INVENTION 
     Air to air heat exchangers are used in ventilation and air conditioning systems. 
     Previous ventilation systems have often relied on separate pieces of equipment to perform conveyance of the fluid streams and the heat transfer therebetween, for example employing blower fans to circulate the two streams of air through a stationary heat exchanger unit. Applicant&#39;s previous patent issued under U.S. Pat. No. 5,000,253 discloses an example of a stationary air-to-air heat exchanger useful in a building ventilation system so that stale air being discharged from a building in exchange for fresh outside air undergoes heat exchange with the incoming fresh air to reduce the temperature difference between the two to minimize energy waste resulting from having already heated or cooled the inside air. 
     Other prior art includes heat exchange fan devices that operate to both convey the two air flow streams and effect the heat transfer therebetween. U.S. Pat. No. 4,431,048 of Mori et al. and U.S. Pat. No. 6,695,038 of Lopatinsky et al. teach two such devices. 
     In each these two devices, a double sided impeller draws in separate streams of air at axial inlets centered on the rotational axis of the impeller, and heat transfer between the steams occurs through the impeller as the air streams subsequently move outwardly away from the rotational axis on opposite sides of the impeller to exit the unit beyond the periphery of the thereof. The length of travel over which heat exchange occurs between the streams is dictated by the radial size of the impeller. 
     Applicant has developed a unique heat exchange fan apparatus in which a rotor likewise provides a heat exchange function while acting as an impeller to drive the fluid streams, but that instead provides a heat exchange path occurring along an axial, not radial, dimension of the unit. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the invention there is provided a heat exchange fan apparatus comprising: 
     a rotor supported for driven rotation about a central axis thereof, the rotor comprising:
         opposing end faces at opposite ends of the rotor;   a series of inlet openings in each end face that are spaced apart from one another around the central axis and that each extend outwardly away from the central axis toward a perimeter of the end face, each inlet opening in each end face aligning around the central axis with a respective closed portion of the other end face between two adjacent inlet openings therein;   a series of flow channels disposed adjacent one another around the central axis and extending therealong from one of the end faces to the other, each flow channel being disposed between a pair of flow channels thereadjacent and sharing a common boundary wall with each of said pair of flow channels, and each flow channel having an open end defined by a respective inlet opening spanning between the common boundary walls of the flow channel in one of the end faces and a closed end defined by the respective closed portion of the other end face; and   for each flow channel, a respective outlet opening provided at a periphery of the rotor adjacent the closed end of said flow channel; and       

     a drive system operable to drive rotation of the rotor, under which fluid is drawn from fluid sources exposed to the opposing end faces of the rotor into the flow channels through the inlet openings to create opposing fluid flows in adjacent flow channels. 
     Preferably there are provided fluid guiding passages at opposing end portions of the rotor, each fluid guiding passage communicating with either the inlet openings or the outlet openings at a respective one of the end portions of the rotor to prevent mixing of fluid exiting one of the opposing fluid flows with fluid entering one the other fluid flow. 
     Preferably there are provided two housings each closing around a respective end portion of the rotor adjacent a respective one of the end faces thereof with an interior spiral channel of the housing open to the outlet openings adjacent said respective end face to fluid from said outlet openings to a tangential outlet of the housing. 
     Each common boundary wall, as extends outwardly away from the central axis, preferably curves in a same direction about same central axis. 
     The drive system is preferably arranged to drive rotation of the rotor in the same direction in which the common boundary walls curve. 
     Preferably the device is used in combination with a building having an interior space separated from an external environment outside the building, the heat exchange fan apparatus having the inlet openings at one of the end faces in fluid communication with the interior space and the outlet openings adjacent said one of the end faces in fluid communication with the external environment, the inlet openings at the other of the end faces being in fluid communication with the external environment and the outlet openings at said other of the end faces being in fluid communication with the interior space. 
     Preferably the rotor comprises a cylindrical periphery wall closing around the central axis and extending between the end faces of the rotor, the outlet openings of the flow channels communicating through the cylindrical periphery wall. 
     Preferably the cylindrical periphery wall closes off each flow channel at the periphery of the rotor, except at the outlet opening of each flow channel, said outlet opening being provided in said cylindrical periphery wall. 
     Preferably each boundary wall extends away from the central axis to an outer end of the boundary wall where the boundary wall joins to the cylindrical periphery wall. 
     Preferably the rotor comprises a cylindrical sleeve closing around the central axis, each boundary wall being joined to the cylindrical sleeve at an inner end of the boundary wall and joined to the cylindrical periphery wall at an outer end of the boundary wall so that each flow channel is enclosed on four sides, except at the outlet opening of said flow channel, by the boundary walls of said flow channel, the cylindrical sleeve and the cylindrical periphery wall. 
     Preferably the rotor is fixed on a rotatably supported shaft that passes therethrough on the central axis, the shaft being coupled to the drive system for driven rotation of the rotor by driven rotation of the shaft. 
     Preferably the end faces and boundary walls of the rotor are of sheet metal construction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings, which illustrate a exemplary embodiments of the present invention: 
         FIG. 1  is a partially exploded perspective view of a heat exchange fan device of the present invention with one end cap thereof exploded therefrom for illustrative purposes. 
         FIG. 2  is a perspective view of a rotor of the heat exchange fan device. 
         FIG. 3  is a perspective view of a housing assembly of the heat exchange fan device with a second end cap, opposite that of  FIG. 1 , likewise exploded from the housing. 
         FIG. 4  is a schematic illustration of the heat exchange fan device installed as part of a ventilation system operating to exhaust stale indoor air from a building for replacement by fresh outdoor air. 
         FIG. 5  is a schematic cross-sectional view as taken along line V-V of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 to 3  illustrate the assembly of a heat exchange fan device  10  of the present invention, in which a longitudinal rotor or drum  12  is mounted on a shaft  14  for rotation therewith inside a housing assembly  16  that features two volute or scroll housings  18 ,  20  at opposite ends. The hollow interior of the rotor  12  is divided into separated channels  22  extending along the central longitudinal axis of the cylindrical rotor. The channels are disposed adjacent one another around the central axis, with each channel being open at a one of the rotor&#39;s two end faces  24  opposite that at which the next channel has one of its ends open. Driven rotation of the rotor  12  acts to draw air axially through the rotor  12  from each of the opposing ends  24  thereof through the internal channels  22  open at that end of the rotor, thereby allowing heat transfer through the channel walls between the air flows passing through the rotor in opposing axial directions. Each channel, adjacent its closed end at one of the end faces of the rotor, has an exhaust opening  26  in the peripheral wall  28  of the rotor, where the airflow in the channel  22  can thus exit the rotor to pass into the spiral channel  30  of the respective volute housing extending around at this portion of the rotor  12 . The air drawn into the rotor at each end of thereof is thus exhausted from the device at the tangential exhaust outlet  32  of the volute housing at the opposing end of the rotor. 
     The rotor of the illustrated embodiment is of a cylindrical sheet metal construction featuring two equally sized end faces  24  defined by flat circular sheets, and a third rectangular sheet having been wrapped into a cylindrical form and closed off at each end by a respective one of the circular end sheet to form a peripheral wall  28  of the rotor. Each end sheet  24  has a central circular hole  34  cut therein, through which the shaft extends. A cylindrical sleeve  36  smaller than the cylindrical periphery wall  28  is connected to the end faces  24  at the perimeters of the central circular holes therein, and closes around the shaft  14  to further support the rotor thereon. 
     With reference to  FIG. 2 , each of the twenty-four equally sized and shaped channels  22  of the illustrated rotor is bound on opposing sides thereof around the shaft  14  by two curved rectangular sheets of equal shape and dimension. Each curved sheet  38  is fixed to the end face sheets  24  at its opposing longitudinal ends  38   a ,  38   b  of the curved sheet  38 , and is fixed to opposites ones of the cylindrical sleeve and peripheral wall of the rotor at its opposing longitudinal sides  38   c ,  38   d . The curved sheets  38  each curve in the same direction about the central longitudinal axis on which the shaft and rotor turn so that the sheet&#39;s outer longitudinal side  38   d  radially furthest from the axis leads the sheet&#39;s inner longitudinal side  38   c  nearest the axis in this direction. 
     Each curved sheet  38  thus forms a shared or common boundary wall of two adjacent channels around the central axis. Adjacent pairs of the curved sheets around the central axis thus cooperate with portions of the inner cylindrical sleeve  36  and outer cylinder periphery wall  28  of the rotor spanning between these two curved sheets to enclose each channel  22  on four sides of its cross-section over most of the channel&#39;s length between the opposing end faces  24  of the rotor. The resulting channels have a non-circular, irregular cross-sectional shape that is elongated in the direction moving radially away from the rotor&#39;s axis. As shown in  FIGS. 1 and 2 , alternating channels around the axis at each end face of the rotor have open ends defined by cut out entrance or inlet openings  40  in that end face  24 . Each such inlet opening  40  spans fully from one curved sheet to the next curved sheet around the axis in the direction in which each curved sheet  38  curves around the central axis, and spans from near the inner cylindrical sleeve  36  to near the outer periphery wall  28  of the rotor. This arrangement of openings  40  leaves small annular rim portions of the end face sheet intact around the central shaft hole therein and the outer circular perimeter thereof, and curved radial portions of the same sheet intact between adjacent ones of the end face openings  40 . 
     The two end faces  24  of the rotor  12  are identical and are each positioned in a plane normal to the central axis of the shaft and rotor, and are oriented relative to one another so that each inlet opening  40  in one end face is aligned about the central axis with a respective closed portion of the other end face left intact between two adjacent inlet openings therein. Accordingly, each channel is closed at one end face and open at the other. With reference to  FIG. 2 , each channel has an outlet or exhaust opening  26  formed in the periphery wall  28  of the rotor adjacent the closed end of the channel. Accordingly, during rotation of the rotor  12 , air entering the channel  22  through the inlet opening  40  thereof in one end face  24  will flow through the channel, parallel to the central axis of the rotor, toward the other end face. As the air reaches the closed end of this other end face, it can then exit the channel in a more radial direction, passing outwardly through the exhaust opening  26  in the peripheral wall  28  of the rotor. 
     The volute housing  18 ,  20  at each end of the housing assembly of  FIG. 1  is positioned along the central axis so as to wrap around an end portion of the rotor  12  that includes the exhaust openings  26  adjacent the respective end face  24  of the rotor. The spiral channel  30  of the volute housing has a uniform width sufficient to span fully over the exhaust openings  26  in the rotor periphery in the direction of the central axis, and has an outer radial dimension increasing toward the tangential outlet  32  of the volute housing. The spiral channel is generally U-shaped in cross section, with the open side of the channel facing toward the central axis of the device so that the exhaust openings  26  of the rotor  12  open into this spiral channel through this open side. The volute housings are interconnected by a central cylindrical housing  42  interconnecting them at their facing-together sides around the axial passages through the volute housings  18 ,  20 . The volute housings are oriented so that their airflow directions are the same; that is, the direction around the central axis in which the spiral channel&#39;s cross-sectional area increases toward the tangential outlet  32  of the volute housing  18 ,  20  is the same for each volute housing. By way of the end portions of the shaft  14  projecting beyond the opposing ends of the rotor  12 , the rotor is rotatably suspended within the three sections of housing. 
     A respective end cap  44 ,  46  fastens onto each volute housing at an outer side thereof facing away from the other volute housing. The illustrated caps each feature a circular end plate  48  having a central circular shaft hole  50  therein for accommodating the respective end portion of the shaft axially projecting from the corresponding end of the rotor. A second hole in the end plate of the cap is positioned radially outward from the shaft hole on the central axis, and communicates with a stub duct  52  having one end fixed to the end plate  48  around this second hole so as to project from the end plate on a side thereof opposite the rotor. A cylindrical wall portion  54  of the end cap is fixed to the end plate along the circular perimeter thereof to project to the side of the end plate opposite that to which the stub duct  52  projects. When the end of this cylindrical wall portion opposite the end plate of the cap is fixed to the respective volute housing, for example using screws threaded into the side wall of the volute housing through an annular flange of the cap that encircles the cylindrical wall portion at the end thereof opposite the end plate in a plane parallel thereto, the end portion of the shaft  14  projecting out from the volute housing passes through the shaft hole  50  in the cap&#39;s end plate to a point where it is rotatably suspended outside the capped housing assembly. The cylindrical portion of the end cap carries the end plate of the cap axially outward from the rotor. Air entering the stub duct  52  and moving onward through the cap&#39;s end plate to the resulting space between the end face  24  of the rotor  12  and the end plate  48  of the cap is free to enter the channels  22  of the rotor that are open at this end face  24 , and then to flow through these channels to the exhaust openings  26  at the opposite ends thereof for exiting the housing assembly through the tangential outlet  32  of the volute housing at the end of the rotor opposite the end cap through which these air streams entered the housing assembly. 
     Under driven rotation of the rotor, the channel walls extending outward away from the central axis of the rotor act like impeller fan blades to induce this axial draw of air into the rotor through the openings in each of the two end faces, thus conveying counter-flow air streams through the rotor from opposite ends thereof and enabling heat transfer between these opposing air streams through the shared boundary walls between adjacent channels carrying these opposing air flows. 
       FIGS. 4 and 5  schematically illustrate use of the above described heat exchange fan device in a ventilation system for a building. A first duct or conduit  60  is coupled to the tangential outlet of a first one of the volute housings  18 , a second duct or conduit  62  is coupled to the tangential outlet of the second volute housing  20 , a third duct or conduit  64  is coupled to the stub duct  52  of a first one of the two end caps  44  and a fourth duct or conduit  66  is coupled to the stub duct of the second end cap  46 . The first and third ducts  60 ,  64  do not open to the interior space of the building, and instead pass through openings in a wall  68  of the building in order to open to the external environment outside the building. The second and fourth ducts  62 ,  66  remain indoors, communicating only with the interior space of the building and avoiding exposure to the outdoor environment. 
     This sets up an air exchange configuration of the ventilation system, where under driven rotation of the rotor of the heat exchange device, fresh outdoor air is drawn into the rotor via the third duct  64  and first end cap  44 , while stale indoor air is drawn into the rotor via the fourth duct  66  and second end cap  46 . These streams of air from separate sources flow through the rotor in opposing axial directions within neighboring internal channels of the rotor, so that the fresh air is then released into the interior space of the building via the second volute housing  20  and second duct  62  and the stale air is exhausted to the outside environment via the first volute housing  18  and first duct  60 . The ductwork or conduits thus provide passages connecting the inlet and outlets of the heat exchange fan device with suitably different, separated or spaced apart locations for drawing and exhausting air without mixing the entering and exiting streams of air at each end of the rotor. 
     When a difference in temperature exits between the inside and outside air, loss of energy put into heating or cooling the building is reduced compared to a ventilation system in which no heat exchanger is employed, as heat transfer takes place between the opposing air flows through the rotor via the common boundary wall between channels through which opposite ones of the fresh and stale air flows are passing. When the outside air is cooler than the inside air, heat from the inside air being drawn from the building interior for exhaust to the outside environment is transferred to the cooler outside air entering the building so that the incoming air is warmed to a temperature nearer the current indoor temperature. On the other hand, when the outside air is warmer than the inside air, heat from the outside air being drawn into the building interior from outdoors is transferred to the outgoing indoor air, thereby cooling the incoming fresh air to a temperature nearer the current indoor temperature. 
     The end portions of the shaft  14  of the device  10  outside the end caps  44 ,  46  thereof are rotatably supported by bearings  70  to enable rotation of the shaft-carried rotor inside the housing assembly, which is mounted, seated or otherwise installed in a fixed stationary position. In the illustrated embodiment, a drive system operable to effect rotation of the shaft  14  features an electric motor  72  coupled to the shaft by a drive belt  74  entrained around a pulley  76  fixed on an output shaft of the motor and another pulley  78  fixed on the shaft  14  of the heat exchange fan device  10 . The heat exchange device and the drive system may be mounted on a shared framework or enclosed within a common housing or enclosure for transport and installation of these components as a single assembled unit. Such a pre-assembled unit may have the axial inlets and tangential outlets at the ends of the rotor pre-routed to the exterior of the common housing to provide easily accessible connections to which suitable ducting or conduit components can be fastened as required to connect the resulting ventilation system to interior and exterior spaces at the location of the building concerned. 
     The illustrated heat exchange device of the ventilation system is shown inside the building, but it will be appreciated that it alternatively may be installed somewhere outside the building, and for example may be a rooftop unit mounted atop the building. In another possibility, the heat exchange device may be installed in a manner positioning it partially inside the building and partially thereoutside, for example via an opening in a wall structure of the building, so that the ends of the rotor are situated in opposite ones of indoor and outdoor environments. It will therefore be appreciated that it may not be necessary to connect a duct to each and every inlet and outlet of the device in order to have it arranged to exchange stale indoor air for fresh outdoor air. In such an installation, although there is not need to duct any inlet or outlet of the heat exchange fan device through an exterior wall of the building, it may still be desirable to duct at least one of the inlet and outlet at one or both ends to a respective location distanced from the device in order to space apart the collection point of the incoming air stream and the discharge or exhaust point of the outgoing air stream to prevent mixing thereof. 
     In the illustrated embodiment, the cross-sectional area of the circular bore of each inlet duct  52  and the area of the rectangular tangential outlet  32  of each volute or scroll housing are each notably less than half of the sum total area of the twelve curved inlet openings  40  in a one of the rotor end faces  24 . Accordingly, the incoming air stream at each end of the heat exchange fan slows down as it transitions from the smaller inlet duct into the channels of the rotor that are open at that end, meaning that a given volume of this air stream takes longer to pass fully through the rotor than it would if passing through at a higher velocity. 
     Although the illustrated embodiments are shown with the motivational central axis of the rotor oriented horizontally, it may be preferable to install devices with their rotors in a vertical orientation, especially when the device is to be used in an outdoor setting in environments or climates known to experience colder weather. This way, any moisture build up in the rotor will drain from the vertically oriented channels of the rotor to prevent the moisture from freezing inside the rotor when the device is not being driven. This will prevent detrimental effects of such frozen moisture buildup on the rotational balance of the rotor, which imbalance might otherwise cause vibration, lower the performance or efficiency of the device, or possibly lead to premature wear or failure of components. The device may be constructed substantially wholly from sheet metal, as such material may be used to form the rotor, the housing assembly, the end caps, and any external housing containing these elements. In one embodiment, steel sheet metal is used for the housings and end caps, while aluminum sheet is used for the rotor to provide a lighter weight rotating structure. The external housing containing the rest of the device may have employ insulated on its exterior walls. For extreme weather conditions, especially climates experiencing freezing, a unit installed outside or on the rooftop is preferably insulated and then covered with sheet metal for protection from the elements, and the ducting coming into and out of the building is preferably also insulated. In addition to improved efficiency, this would also reduce the chances of water vapor freezing in the unit when stopped, and throwing the rotor out of balance when started again. 
     Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without department from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.