Patent Application
20120037340
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.
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'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.
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:
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.
In the accompanying drawings, which illustrate a exemplary embodiments of the present invention:
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
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'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's axis. As shown in
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
The volute housing 18, 20 at each end of the housing assembly of
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'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'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.
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.
