Abstract:
A fluid liquid/fluid gas heat exchanger includes a hollow housing through which one of the fluids flows and whose exterior is exposed to the other fluid. The housing rotates about one or more non-rotating tubes which form inlet and outlet openings.

Description:
BACKGROUND  
       [0001]     The present invention relates to a heat exchanger for transferring heat between a first liquid fluid and a gaseous fluid such as, for example, ambient air, and more particularly to a heat exchanger which has a hollow housing through which one of the fluids flows and whose exterior is exposed to the other fluid.  
         [0002]     Such heat exchangers are used as coolers in vehicles. For example, published German patent application DE10139315 describes a heat exchanger in an engine cooling circuit. In such heat exchangers the coolant flows through tubing in a fixed, thin-walled cooler. The cooler is normally a flat, slab-shaped body and includes openings through which ambient air is blown. The cooler separates the two media, air and coolant. In order to attain a good heat exchange there is an advantage in a high flow velocity of the two media, coolant and ambient air, a high heat conductivity of the cooler and a large surface area of the cooler. Since the heat exchange between a fluid and a fixed body, as a rule, is very much easier than the heat exchange between a gas and a fixed body, the latter determines the dimensions of the cooler required for the transfer of a given amount of heat. Ribs can be used to increase the surface area of the cooler. But, for agricultural applications in which the ambient air is highly contaminated, ribs can become contaminated very rapidly, Thus, reducing the transfer of heat.  
         [0003]     A blower may be used to blow air through the heat exchanger. The heat transfer performance is determined primarily by the amount of air conveyed, the flow velocity and the temperature difference between the outer surface of the cooler and the ambient air. A pump may be used to convey the fluid through the heat exchanger.  
         [0004]     The disadvantage of these heat exchangers is the requirement for a large surface area for the side of the heat exchanger that is in contact with the ambient air. This surface area is considerably larger than the surface area that is in contact with the fluid. As a result, the heat exchanger must be large. A considerable amount of energy is also required in order to convey the two fluids, particularly the ambient air, through the heat exchanger. Contamination is a considerable problem in an agricultural application. There is a high cost in components and configuration as a result of the requirement for a pump, a blower and a cooler.  
       SUMMARY  
       [0005]     Accordingly, an object of this invention is to provide a heat exchanger which has small dimensions with a high heat transfer performance capability.  
         [0006]     A further object of the invention is to provide such a heat exchanger which requires relatively little operating energy, contain few costly components and reduces the danger of contamination.  
         [0007]     These and other objects are achieved by the present invention, wherein a heat exchanger exchanges heat between a liquid fluid and a gas fluid. The heat exchanger includes a rotating hollow housing through which one of fluids flows and whose exterior is exposed to the other fluid. Preferably, the fluid flowing through the hollow housing is preferably a liquid, the gas flows around the hollow housing. The high circumferential velocity which is possible with a rotating hollow housing produces high flow velocities along its outer or inner circumferential surface, and an effective heat exchange. Thus, the performance of the heat exchange can be increased with a reduced surface area and smaller unit size compared to common conventional heat exchangers. The danger of contamination is reduced since the contaminant particles are not deposited in narrow penetration channels, but are blown away. It is furthermore possible to combine the functions of cooler, pump and blower in a unit, resulting in a simple design in which separate drives for pump and blower are omitted and that require considerably less energy to operate.  
         [0008]     Preferably, in order to provide a good heat transfer, the hollow housing consists of aluminum, for example, of cast aluminum. The hollow housing preferably includes an axial inlet opening and an axial outlet opening for fluid flowing through it, where one fluid is conducted into the hollow housing through a first axial tube and is conducted out through a second tube which is coaxially with respect to the first tube, thus forming an annular channel between the tubes. With such a coaxial unit, only a single seal and a one bearing are required. Fluid can be supplied through the inner tube and then drained out through the annular channel, although fluid may flow in the opposite direction.  
         [0009]     Preferably, overflow ports in the inlet tube communicate fluid directly from the inlet opening to the outlet opening. Thus, the cross sectional areas of the inlet and the outlet are designed so that a part of the fluid flows directly from the inlet to the outlet and not through the interior of the hollow housing on the basis of differing flow velocities in the inlet and the outlet. Preferably, a section of the return line can be configured as an injector to reduce the diameter near the bearing and seal area, while maintaining the same volume flow in the outer cooling circuit.  
         [0010]     An alternate embodiment includes a single undivided tube which extends axially through the hollow housing and forms inlet and outlet openings located outside the hollow housing. Radial ports are formed in the portion of the tube inside the hollow housing so that fluid can flow out of the tube, into the hollow housing and back into the tube.  
         [0011]     Preferably, the hollow housing includes a closable filler opening in an outer surface through which the hollow housing can be filled and drained. An elastic membrane may be mounted in the interior of the hollow housing to separate a part of the volume enclosed by the hollow housing from the fluid. The membrane may be preloaded, for example, by a spring or by a pressurized gas to equalize volume changes of the fluid flowing through the hollow housing.  
         [0012]     A pump impeller may be rigidly fastened to the interior of the rotating hollow housing, and bearings can support both the pump impeller and the hollow housing, so that no additional bearing support of the pump impeller is required. The pump impeller is used to convey the fluid through the hollow housing.  
         [0013]     The hollow housing may be connected rigidly to an external blower impeller which rotates with the housing. A single bearing may support both the blower impeller and the hollow housing. The pump impeller conveys the gas which flows along the outside of the hollow housing.  
         [0014]     Preferably, a non-rotating guide impeller or guide housing is provided inside or outside the hollow housing upstream or downstream of the pump impeller or the blower impeller. The guide impeller and the guide housing interact with the associated pump impeller or blower impeller in order to assure an optimum guidance of the fluid. If the guide impeller is located within the hollow housing it may be necessary to configure the hollow housing as a multiple piece component so that the hollow housing can be disassembled in order to make an installation of the guide impeller possible.  
         [0015]     In order to increase the surface area available for heat exchange, projections and recesses are provided on a (preferably cylindrical) outer surface and/or on a (preferably cylindrical) inner surface of the hollow housing. Preferably, these projections are helical blades arranged at an angle with respect to the axis of rotation, so that they can help convey either of the fluids. A non-rotating guide impeller or guide housing may also be arranged upstream and/or downstream of the blades.  
         [0016]     The hollow housing can be driven by drives such as, for example, spur gears, flat belts, toothed belts, V-belts, toothed V-belts or roller chains. It is also possible to drive the hollow housing electrically and, in particular, to connect it rigidly with the rotor of an electric motor. The electric motor and the housing can be supported by the same bearings.  
         [0017]     Preferably, the hollow housing is connected to the rotor of an asynchronous motor and simultaneously forms a short circuit ring of the asynchronous motor. A collar formed onto the hollow housing may be used as short circuit cage for the asynchronous motor. The housing may be manufactured as a one-piece cast aluminum unit with the collar used as short circuit cage. A second short circuit ring can be poured simultaneously during this manufacturing process. The stator of the asynchronous motor is inserted into a housing of a material with high heat conductivity (for example, cast aluminum), where the housing is in good heat conducting contact with the fluid flowing through the hollow housing. The rotor of the motor is also cooled very well by the fluid flowing through the hollow housing. The asynchronous motor can be operated with a frequency converter at a variable speed, stopped completely and/or to be operated in the reverse direction.  
         [0018]     The temperature of the first and/or second fluids can be sensed by temperature sensors at the inlet and the outlet. Temperature signals may be transmitted to a control unit which controls the rotational speed of the asynchronous motor and as a function of the temperature measurements.  
         [0019]     Preferably, the hollow housing is configured as a one-piece component together with a pump impeller, blower impeller, or projections and recesses, impeller blades and the short circuit cage and the short circuit ring of an electric motor. This one-piece component can be manufactured by casting, die casting, pressure die casting, forging, sintering from a material with good heat conductivity such as aluminum, an aluminum alloy, copper, a copper alloy, zinc, a zinc alloy, glass-fiber or carbon fiber-reinforced plastic or ceramic.  
         [0020]     The invention increases the velocity of fluid gas flow around the hollow housing because the hollow housing rotates about an axis. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]      FIG. 1  is a schematic cross-sectional view of a first embodiment of a heat exchanger;  
         [0022]      FIG. 2  is a side view of the hollow housing of a heat exchanger according to the invention;  
         [0023]      FIG. 3  is a schematic cross-sectional view of a second embodiment of heat exchanger according to the invention;  
         [0024]      FIG. 4  is a schematic cross-sectional view of a third embodiment of a heat exchanger according to the invention; and  
         [0025]      FIG. 5  is a schematic cross-sectional view of a fourth embodiment of a heat exchanger according to the invention. 
     
    
     DETAILED DESCRIPTION  
       [0026]      FIG. 1  shows a cylindrical hollow housing  10  which includes an inlet port  12  and an outlet port  14 . The inlet port  12  is supported for rotation by bearings  16  on a non-rotating inlet tube  18  and is sealed by a seal  20  with respect to the inlet tube  18 . The outlet port  14  is supported for rotation by bearings  22  on a non-rotating outlet tube  24  and is sealed by a seal  26  with respect to the outlet tube  24 . Thus, the housing  10  is supported by bearings for rotation about the central axis  28 .  
         [0027]     Inlet tube  18  forms an axial inlet opening  30 , through which coolant can enter into the housing  10 . Outlet tube  24  forms an axial outlet opening  32 , through which coolant can leave the housing  10 .  
         [0028]     The housing  10  is driven by an asynchronous motor  34 . A short circuit cage  36  is formed onto the outlet side of the housing  10  concentric with the housing  10 , and cage  36  engages the rotor  38  of the asynchronous motor  34 . A portion of the housing  10  is used as short circuit ring  40 . A further short circuit ring  42  is formed onto the short circuit cage  36 . The housing  10 , short circuit cage  36  and short circuit ring  42  consist of a single component of cast aluminum. The stator  44  of the asynchronous motor  34  is inserted into a housing  46  of cast aluminum. The housing  46  is rigidly connected to the outlet tube  24 , which also consists of aluminum with good heat conductivity. By means of this configuration the components of the asynchronous motor are in good heat conducting contact with the fluid flowing through the housing  10  and are very well cooled by the fluid. The bearing  24  supports both the asynchronous motor  34  and the housing  10 .  
         [0029]     The asynchronous motor  34  is connected to a control unit (not shown), that permits the asynchronous motor  34  to operate with variable rotational speed. Temperature sensors (not shown) are arranged near the inlet opening  30  and the outlet opening  32  to detect the inlet temperature and the outlet temperature of the fluid flowing through the housing  10 . Moreover, a temperature sensor (not shown) is located near the circumferential surface of the hollow housing, and detects the temperature of the ambient air flowing around the housing  10 . The signals of the temperature sensors are detected by the control unit and are utilized to control the rotational speed of the housing  10 .  
         [0030]     The exterior surface of the housing  10  is exposed to a flow of surrounding ambient air which cools the fluid flowing through the housing  10 . The cooling effect depends on the dimensions of the housing  10 , particularly its wall thickness and its heat conducting characteristics. With a high circumferential velocity of the rotating housing  10  an effective heat exchange occurs at its outer surface with the surroundings. The heat exchange depends crucially on the size of the outer surface of the housing  10  that is exposed to the cooling air. Therefore, the outer circumferential surface of the housing  10  is provided with a multitude of projections  48  and intervening recesses  50 , that are in good heat conducting contact with the housing  10  and preferably are integral with the housing  10 . As shown in  FIG. 2 , the projections  48  are configured as blades which are inclined with respect to the axis of rotation  28  which simultaneously operate to convey the cooling air and increase the cooling effect.  
         [0031]     Referring now to  FIG. 3 , a single undivided tube  52  extends axially through and is received by the housing  10 . Tube  52  forms at one end an inlet  30  and at its other end an outlet  32 . The tube  52  includes ports  54  near inlet  30  which communicates fluid out of the tube  52  into the housing  10 . Tube  52  also includes ports  56  near outlet  32  for communicating fluid from housing  10  back into tube  52 , as indicated by arrows. The central portion of the tube  52  located between the ports  54 ,  56  is closed by a barrier (not shown), or is restricted by a throttling restriction (not shown) in order to prevent a flow of fluid through tube  52 . Bearings  16  and  22  and seals  20  and  22  are installed between the tube  52  and housing  10 .  
         [0032]     To increase the effective surface in the interior of the housing  10 , a plurality of projections  58  and intervening recesses  60  are formed on the inner wall of the housing  10 . Projections  58  are in good heat conducting contact with the housing  10 , and are preferably integral with the housing  10 . The projections  58  are configured as blades which are inclined to the rotation axis  28 , so that they help convey the fluid.  
         [0033]     A V-belt pulley  62  is fixed to the outlet port  14  for rotation with the housing  10 . Pulley  62  may be used to drive the housing  10  in rotation. The bearing  22  supports the pulley  62  and the housing  10 . Instead of pulley, the housing  10  could be driven by other elements, such as, for example, a gear, a flat belt pulley, a toothed belt pulley, a chain sprocket and the like.  
         [0034]     A blower impeller  64  is fixed to the inlet port  12  for rotation with the housing  10 , and blows a flow of air across the surface of the housing  10  in order to cool the housing  10 . Thus, a separately driven blower or blower impeller is not required. The bearing  20  supports both the blower impeller  64  and the housing  10 . Non-rotating, non-rotating guide housings  66 ,  68  are positioned upstream and downstream of the blower impeller  64  for guiding the flow of air. In many applications, a single guide housing ahead of or behind the blower impeller  64  may be sufficient.  
         [0035]     Referring now to  FIG. 4 , a pump impeller  70  is fastened to and rotates with a central portion of an inner surface of the housing  10 . The pump impeller  70  can be manufactured as a one-piece unit with the housing  10  in a pressure die casting process. The bearings  16  and  22  support both the pump impeller  70  and the housing  10 . The pump impeller  70  conveys the fluid through the housing  10 , so that a separate fluid pump is not required.  
         [0036]     Non-rotating impeller fluid flow guides  72 ,  74  are positioned upstream and downstream of the pump impeller  70  and are mounted on tube  10 . It may be sufficient to provide only one guide  72  ahead of the pump impeller  70  or only one guide  74  behind the pump impeller  70 . The housing  10  may be configured as a multi-piece component to permit assembly of the guides  72 ,  74 .  
         [0037]     Referring now to  FIG. 5 , hollow housing  80  includes a port  82  on one side only that is concentric to the axis of rotation  81 . Two non-rotating concentric tubes  84 ,  86  are mounted in port  82 . Coolant is supplied through the interior  85  of inner tube  84  into the housing  80 . Coolant flows out of housing  80  through an annular passage formed between tubes  84  and  86 . The port  82  is supported by a bearing  88  on the outer tube  86  and is sealed by a seal  90  against the outer tube  86 . Additional bearings and seals can be omitted.  
         [0038]     The inner tube  84  includes radial overflow ports  92  which permit fluid to flow between the inlet and the outlet. Due to differing fluid flow velocities in the supply and the drainage, a portion of the fluid flows directly from the inlet through the overflow channels  92  into the annular outlet channel  87  and not into the interior of the housing  80 . Moreover the ends of the outer tube  86  are flared in a conical shape and the bearings and seals are located on the reduced diameter portion of tube  86 . The fluid pressure will be reduced as it exits out of flared end of tube  86  and this lower pressure helps draw fluid through radial ports  92 .  
         [0039]     A filler opening  94  and a stopper  96  is located in the upper outer surface of the housing  80 , according to  FIG. 5 . The filler opening  94  is used to fill and drain the housing  80  and the entire cooling arrangement with coolant. When being filled, the housing  80  is rotated into a position in which the filler opening  94  opens generally upward. When being drained, the housing  80  is rotated until the filler opening  94  opens downwardly.  
         [0040]     As also shown in  FIG. 5 , an elastic membrane  98  in the interior of the housing  80  separates the housing  80  into two separate chambers  99  and  101 . Chamber  101  is not exposed to fluid within housing  80 . The elastic membrane  98  is preloaded by a spring  100  which permits changes in the volume of the chambers  99  and  101  as a result of differing temperatures. Alternatively, or in addition to the spring  100 , chamber  101  could also be filled with a gas.  
         [0041]     While the present invention has been described in conjunction with a specific embodiment, it is understood that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, this invention is intended to embrace all such alternatives, modifications and variations which fall within the spirit and scope of the appended claims.  
       Assignment  
       [0042]     The entire right, title and interest in and to this application and all subject matter disclosed and/or claimed therein, including any and all divisions, continuations, reissues, etc., thereof are, effective as of the date of execution of this application, assigned, transferred, sold and set over by the applicant(s) named herein to Deere &amp; Company, a Delaware corporation having offices at Moline, Ill. 61265, U.S.A., together with all rights to file, and to claim priorities in connection with, corresponding patent applications in any and all foreign countries in the name of Deere &amp; Company or otherwise.