Abstract:
A cooler for fluids uses multiple internal channels to increase the time a hot fluid is contained in the cooler, thus increasing cooling efficiency, and allowing the length of the cooler to be shorter than an equivalent cooler with fewer passes. The cooler uses external and internal heat-exchanging fins to increase surface area for contact with both the fluid and the external environment. The cooler is designed around a cylindrical vessel, equipped with a set of internal baffles, forming the multiple channels. End caps, one of which contains inlet and outlet ports, are welded to the cooling vessel, increasing ability to contain pressure. The small channel size and fluid flow-path holes cut through the baffles prevent air bubbles, which would reduce cooling efficiency. Coolers with four channels are provided for higher-pressure applications and coolers with six channels are provided for lower-pressure applications. Some coolers have an air flow assembly with a fan, to direct more cooling air around the cooler vessel. An airflow assembly with a fan controlled by a thermostat on the cooler is also disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority from U.S. Provisional Patent Application No. 60/490221, filed Jul. 26, 2003, entitled Multi-Pass Fluid Cooler, to inventor Charles Sanders, the contents of which are incorporated by reference herein in their entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     1. Field  
         [0003]     Embodiments relate to the field of cooling systems, and in particular to fluid coolers.  
         [0004]     2. Related Art  
         [0005]     FIG. 1, from U.S. Pat. No. 4,207,187, to Booth, shows a combination oil-filter and cooler. Oil flows into housing  3 , though fitting  17  of end cap  9 , which is screwed into housing  3 . End cap  9  and filter cartridge  24  seat against O-ring  47 . Oil flows through central opening  31  into filter cartridge  24  and element  25  (held in place with cap  27  and spring  35 ). Oil flows out of end cap  13  (though fitting  19 ) in direction  6 . Cylinder  3  includes outer fins  5  and inner fins  7 , to facilitate heat conduction.  
         [0006]     The Booth cooler requires a filter, which is no longer a requirement for many modern coolers, because the machinery to which they will be attached already contains sufficient filtering. Including a filter inside a cooler can lead to problems with clogging and requires the use of at least one O-ring seal to facilitate changing the filter element. Under high-pressure flow, O-ring seals tend to leak, potentially resulting in fluid loss and danger to users. Further, the Booth cooler is a single-pass cooler, resulting in fluid being retained in the cooler structure for a limited period of time, lowering cooling efficiency, and requiring hose connections at both ends of the long cooler structure.  
         [0007]      FIG. 2  illustrates a transmission oil cooler, marketed by Specialty Auto Tech (SAT), Inc., of Rancho Cucamonga, Calif. In the SAT cooler, a single, axial, wall divides the cooler in half, routing the transmission oil in and out of the same end of the cooler.  
         [0008]     Oil flows into housing  203 , in direction  270 , though fitting  264  and hole  265  of end cap  262 , which is welded into housing  203 . Housing  203  is divided into upper chamber  253  and lower chamber  255  by wall  250 . Wall  250  is provided with upward dimples  251  and downward dimples  252 , which direct oil toward inner fins  207 , away from wall  250 . Oil proceeds in direction  271 , through aperture  254 . Oil returns through lower chamber  255  and exits housing  203  in direction  272 , through hole  266  and fitting  267  in end cap  262 , which is welded to housing  203 . The other end of vessel  203  is capped by end cap  260 . Outer fins  205  (bare aluminum) conduct heat to the air.  
         [0009]     The SAT cooler sends oil through two passes (channels  253  and  255 ). While the two passes do increase cooling efficiency, the cooler is still required to be long to increase surface area to further increase efficiency. Further, the large channel size in both the Booth and SAT coolers contribute to formation of air bubbles, which keep liquid away from the heat-exchanging surfaces (e.g., fins  7  and  207 ), further lowering cooling efficiency.  
         [0010]     Typical automobile radiators use bent metal tubes to create desirable multiple fluid cooling passes. However, the tube structures in typical radiators are difficult to bend over tight radii, require several assembly steps to bend and mount to heat-exchanging structures, take up significant volume (because each part of the tube must withstand fluid pressure), and do not typically achieve high conduction efficiency to the structures to which they are attached.  
         [0011]     Therefore, what is required is a compact cooler with small multiple channels, requiring minimal wall material, to provide safe and highly efficient cooling.  
       SUMMARY  
       [0012]     Embodiments include coolers for cooling hot fluids, comprising a vessel provided with multiple inner channels for fluid flow and heat exchange. In some embodiments, the vessel is formed by extrusion.  
         [0013]     Embodiments include low-pressure coolers, provided with six inner channels, formed by a baffle assembly, in which cooling fluid makes four passes through the six channels of the cooler. Embodiments include high-pressure coolers, provided with four inner channels, formed by a baffle assembly, in which cooling fluid makes four passes through the four channels of the cooler.  
         [0014]     Embodiments include methods of cooler manufacture, comprising cutting a piece of extruded vessel material to a desired length, inserting a baffle assembly, and welding on end caps.  
         [0015]     Embodiments include fluid coolers, surrounded by airflow assemblies, to facilitate exchange of heat with the ambient environment. In some embodiments, cooling is further facilitated with an air fan. In some embodiments, the fan is switched on and off by means of a temperature sensor integrated in contact with the cooler. 
     
    
     BRIEF DESCRIPTION OF THE ILLUSTRATIONS  
       [0016]      FIG. 1  (prior art) is an illustration from U.S. Pat. No. 4,207,187 to Booth.  
         [0017]      FIG. 2  (prior art) is an illustration of a double-pass transmission fluid cooler.  
         [0018]      FIG. 3A  is an assembly view of a six-channel fluid cooler, according to of the present invention.  
         [0019]      FIG. 3B  is an external view of a six-channel fluid cooler, according to the present invention.  
         [0020]      FIG. 4A  is an end-view of a six-channel baffle assembly, according to the present invention.  
         [0021]      FIG. 4B  is a lateral view of a six-channel baffle assembly, according to the present invention.  
         [0022]      FIG. 4C  is a diagram of six-channel fluid flow, according to the present invention.  
         [0023]      FIG. 5A  and  FIG. 5B  are end and side views of an end cap, according to the present invention.  
         [0024]      FIG. 6A  and  FIG. 6B  are end and side views of an end cap with inlet and outlet ports, according to the present invention.  
         [0025]      FIGS. 7A and 7B  are end views of a cooling vessel with and without baffles inserted, according to the present invention.  
         [0026]      FIG. 8  is a schematic diagram of an application of a fluid cooler, according to the present invention.  
         [0027]      FIG. 9A  is a perspective view of a four-channel fluid cooler baffle assembly, according to of the present invention.  
         [0028]      FIG. 9B  is an end view of a four-channel fluid cooler vessel and baffle assembly, according to the present invention.  
         [0029]      FIG. 10  is a perspective view of a cooler with an airflow assembly, according to the present invention. 
     
    
     DESCRIPTION  
       [0030]      FIG. 3A  and  FIG. 3B  are assembly and external views of a six-channel, four-pass, fluid cooler, according to the present invention. Multi-pass cooler  300  is formed of vessel  310 , baffle assembly  320 , first end cap  340 , and second end cap  342 . Vessel  310  includes internal cylindrical chamber  314 , capable of withstanding the pressure of hot, compressed fluid being pumped through it. For example, a wall thickness of approximately 0.072 in. (0.065-0.080) of a two-inch aluminum vessel provides sufficient strength for vessel  310  to be used for a cooler, under a static pressure of 3000 psi. Vessel  310  may be formed by many processes, including casting, extrusion, machining, or any other method of creating a robust vessel. In some embodiments, vessel  310  is formed out of aluminum, for improved heat transfer, strength, low-weight, and relative ease of welding. However, other materials, such as steel, copper, ceramic, silicon carbide, alumet, high temperature plastics, or other materials with appropriate strength and relatively high thermal conductivity (e.g., similar to or greater than that of aluminum) may be used.  
         [0031]     By flowing the fluid through multiple (more than two) channels, multi-pass coolers lower the occurrence of air bubbles and effectively increase the length (and therefore efficiency) of cooling, by maintaining fluid in the cooler for a longer time than a single or double pass cooler.  
         [0032]     In some embodiments, vessel  310  includes outer fins  312 , to facilitate conduction of heat from vessel  310  to the ambient environment, or another external heat-conducting medium (e.g., water, oil). In some embodiments outside surface  316  of vessel  310  is coated with high-temperature, high-emissivity paint (such as produced by Aremco) to facilitate radiation of heat to the ambient environment. In some embodiments, outer surface  316  is left as bare metal, brushed, or coated (e.g., anodized, glazed, painted). In some embodiments, mounts  318  are attached to (or formed as part of) vessel  310 , in order to allow it to mount to another piece of machinery, for example, to the frame rail of a vehicle.  
         [0033]     In some embodiments, baffle assembly  320  is formed of baffles  321 ,  322 ,  323 ,  324 ,  325 , and  326 , arranged around center axis  328 , forming six channels. Sets of holes  330  and  332  allow fluid to flow between channels.  
         [0034]     In some embodiments, baffle assembly  320  and vessel  310  are formed as separate pieces. Extrusion, particularly of long, complex assemblies, having small internal volumes can be challenging. Therefore, vessel  310  is extruded, but baffle assembly  320  is formed separately. In some embodiments, baffle assembly  320  is inserted into vessel  310  and tack-welded, so it will not rotate. Vessel  310  is sealed by end cap  340  (equipped with inlet port  344  and outlet port  346 ) and end cap  342 , which are welded in-place. Inlet port  344  and outlet port  346  are capable of attaching to lines  350  and  354 , to allow fluid to enter in direction  352  and exit in direction  356 .  
         [0035]      FIG. 4A  is an end-view of a six-channel, four-pass, baffle assembly, according to the present invention. Baffle assembly  320  is shown in chamber  314  of vessel  310 . Baffle assembly  320  divides chamber  314  into axial channels (a-f).  
         [0036]     In some embodiments baffles  321 - 326  are arranged at equal angular spacing, 60 degrees apart. In some embodiments, channels a and d occupy 72 degrees, while channels b, c, e, and f occupy 54 degrees, allowing extra space for fluid input and output. However, intermediate or exaggerated angular spacing may be used, if sufficient room remains for input and output ports, and if there is consistent flow of fluid through the channels. In some embodiments (for example, for transmission fluid cooling), baffles  321 - 326  are formed of aluminum, with a thickness of 0.040 to 0.060 inches.  
         [0037]     Heat conduction from baffle assembly  320  to vessel  310  is very high, and issues of differential expansion between baffle assembly  320  and vessel  310  are reduced. There is also no issue of rotational alignment between baffle assembly  320  and vessel  310 . An additional benefit is that if long extrusions (vessel blanks) are produced, they can be cut into vessels (segments of the vessel blank) of any desired length, simplifying the manufacture of varying lengths of coolers. However, the state-of-the-art of metal extrusion may limit the sizes, lengths, and quality of these embodiments as extrusions with complex internal structures are difficult to cool uniformly.  
         [0038]      FIG. 4B  is a lateral view of six-channel baffles, according to the present invention. In some embodiments, baffles  321 ,  323 ,  324 , and  326  have semi-circular holes,  330 , at the first end of baffle assembly  310 , near cap  342 . Baffles  322  and  325  are shown with semi-circular holes  332  at the second end of baffle assembly  320 , near cap  340 . Holes  330  and  332  allow fluid-flow to transfer to the next channel and return the other direction. In the example of an approximately 2-inch transmission fluid cooler, holes  330  and  332  have approximately {fraction (5/32)}-inch radii, to provide even distribution of fluid into multiple channels.  
         [0039]     In some embodiments, holes  330  and  332  are replaced or supplemented with other apertures (e.g., semi-circles, circles, squares, rectangles, ovals) in other locations, or baffles  321 - 326  are shortened at the appropriate end to provide a means for fluid to pass between channels. For example, baffles  321 ,  323 ,  324 , and  326  can be cut (e.g., ground, sawed, snipped, welded) at line  431  and baffles  322  and  325  can be cut at line  433 . In some embodiments, where vessel  310  and baffle assembly  320  are a single extrusion, holes  330  and  332  are ground or cut from the ends of baffles  321 - 326  after vessel  310  is cut to the desired length from the extruded vessel blank.  
         [0040]     In some embodiments, baffle assembly  310  is formed by welding baffles  321 - 326  together at a common axis. In some embodiments, baffle assembly  310  is formed of three V-shaped sections welded together.  
         [0041]      FIG. 4C  is a diagram representing fluid flow through a six-channel, four-pass, baffle assembly, according to the present invention. Referring to  FIG. 4B , fluid flows into channel a, between baffles  321  and  326 , through holes  330  in baffles  321  and  326 , then back through both channel b, between baffles  321  and  322 , and channel f, between baffles  326  and  325 . Fluid then flows through holes  332  in baffles  322  and  325  to channel e, between baffles  324  and  325 , and channel c, between baffles  322  and  323 . Fluid then flows along channels e and c, through holes  330  in baffles  323  and  324  to channel d, and returns along channel d, between baffles  323  and  324 . By dividing axial volume  314  into small channels (a-f), air bubbles, which may form in large channels, are discouraged.  
         [0042]     The length of time hot fluid is contained in the vessel, in part, determines the amount of cooling. Increasing time in the vessel increases heat transfer. Therefore the four passes through six-channel cooler  300  effectively lengthens cooler  300 , providing efficient cooling than a single or double pass cooler. In the example of automotive transmission fluid cooling, an 18-inch-long cooler, having an approximately 2-3 inch diameter chamber significantly increases vehicle cooling. While some types of coolers use bent metal tubes to increase fluid travel length, it is difficult to bend tubes in a small space. Thus, cooler  300  provides efficient cooling by virtue of multiple passes and takes up a small space by virtue of baffle assembly  320  being used in preference to tubes.  
         [0043]     Small channels force fluid against the walls of vessel  310 , providing good heat-exchange, whereas larger channels may result in lower pressure fluid flowing away from the walls of vessel  310 .  
         [0044]      FIG. 5A  is an end view of an end cap, according to the present invention. In some embodiments, end cap  342  is formed out of the same material as vessel  310  (e.g., aluminum), in order to minimize differential expansion as cooler  300  is heated by hot fluid. In some embodiments, end cap  342  has a diameter of 1¾-inches.  
         [0045]      FIG. 5B  is a side view of an end cap, according to the present invention. In some embodiments, end cap  342  is provided with bevel  543 , for aesthetic and safety purposes. End cap  342  is formed with a stepped shape in order to facilitate welding and to provide increased pressure containment by allowing increased fill with weld.  
         [0046]      FIG. 6A  is an end view of an end cap with inlet and outlet ports, according to the present invention. End cap  340  is formed with inlet port  344  and outlet port  346 . Inlet port  344  is positioned to line up with channel a, and outlet port  346  is positioned to line up with channel d. Inlet port  344  and outlet port  346  may be threaded with thread  348  or provided with any convenient fluid interface. Port and thread sizes can be chosen to accommodate standards in the industry or type of machine for which cooler  300  is intended. For example, for use in vehicle cooling, some embodiments have thread  648  cut as ¼-inch National Pipe Thread (NPT) standard threads.  
         [0047]     In some embodiments, end cap  340  is ⅛-inch larger than end cap  342  (1 and ⅞-inches) to provide sufficient space for inlet port  344  and outlet port  346  without weakening its structure.  
         [0048]      FIG. 6B  is a side view of an embodiment of an end cap provided with a transition, according to the present invention. End cap  340  is formed with a stepped shape in order to facilitate welding and to provide increased pressure containment by allowing increased fill with weld. In some embodiments, end cap  340  is provided with bevel  543 , for aesthetic and safety purposes.  
         [0049]      FIG. 7A and 7B  are end views of a cooling vessel with and without baffles inserted, according to the present invention. Internal cooling fins  411  and  413 , of different lengths, are added to increase heat transfer from the fluid.  
         [0050]     In some automotive applications, cooler  300  is sized per the following example. In an approximately 2-inch cooler, twenty outer fins  312 , set at even spacing  740  (18 degrees), extend to diameter  702 , 3-inches. Fins  312  join vessel  310  at bend radius  732  (0.060 inches), in preference to a right angle, to maximize conduction and to add strength to vessel  310 . Outer fins  312  are formed with width  720 , 0.060-inches, and terminate in an arc of radius  730 , 0.020 inches.  
         [0051]     Vessel  310  is approximately 18-inches long and has outer diameter  704  of 1.9 inches and inner diameter  706  of 1.75 inches. Inner fins  411  extend to limit diameter  708  of 1.26 inches, and inner fins  413  extend to limit diameter  710  of 1.06 inches. Fins  411  and  413  are approximately 0.040 inches thick, terminating in an arc of radius  730 , 0.020 inches.  
         [0052]     In some embodiments, vessel  310  is formed for later insertion of baffle assembly  320  by extrusion, machining, or casting, and internal fins  412  and/or  413  are used to hold baffle assembly  310  in correct rotational alignment, baffles  321 - 326  being tack-welded between pairs of fins  411 ,  413 .  
         [0053]      FIG. 8  is a schematic diagram of an application of a multi-pass fluid cooler, according to the present invention. As an example, vehicle  800 , having transmission  820 , is shown equipped with cooler  300 . In some embodiments, mounts  318  of cooler  300  are suitable for mounting cooler  300  to frame rail  810 . Pump  821 , representative of any fluid pump in a system to be cooled, pumps fluid out of transmission  820 , through line  352 , which is attached to inlet port  344  of cooler  300 . The fluid exchanges heat through cooler  300  to the ambient environment, and exits cooler  300  through outlet port  346 . Fluid returns through line  356 , attached to outlet port  346 , to transmission  820 . In vehicular applications, it can be advantageous to mount cooler  300  outside vehicle  800 , where cooler  300  can receive the benefit of flowing air as the vehicle moves, to further facilitate cooling.  
         [0054]     While  FIG. 8  shows transmission  820  and vehicle  800  as an illustrative example application and location of cooler  300 , those skilled in the art will appreciate that cooler  300  is applicable for use with many different types of machinery (e.g., vehicle engines, machinery engines, hydraulic equipment), and mounted in many different locations, where it could be attached to cooling lines, such as  352  and  356 , and maintain contact with a heat exchanging medium (e.g., air, water, oil). Those skilled in the art will also appreciate that cooler  300  can cool many types of fluids (e.g., engine oil, hydraulic fluid, water). While the above-described approximately 2-inch diameter, approximately 18-inch long, six-channel, four-pass cooler is exemplary of coolers for transmission fluid cooling. The approximate 2-inch size conveniently fits under or in the engine compartment of a typical automobile. However, embodiments of different sizes and/or proportions have many different applications.  
         [0055]      FIG. 9A  is a perspective view of a four-channel, four-pass internal baffle assembly, according to of the present invention. In some embodiments, cooler  300  is provided with four-channel, four-pass baffle assembly  900  rather than six-channel baffle-assembly  320 . In some embodiments, upper baffle  910  includes planes  912 ,  914 , and  916 , and forms the first of the four channels. In some embodiments, planes  912  and  916  are  72  degrees apart.  
         [0056]     Upper baffle  910  is joined to lower baffle  930  (including planes  932 ,  934 , and  936 ) by middle baffle  920 . Plane  916  is provided with aperture  918 . In some embodiments, aperture  918  is an elongated slit, as shown in  FIG. 9A . Providing a high pressure, four-channel cooler baffle assembly with slits, rather than semicircles (see  FIG. 3A ), provides less resistance to fluid flow and facilitates cooler of higher flow rate liquids, such as automotive oil. Middle baffle  920  and plane  936  are similarly provided with apertures  928  and  938 , respectively.  
         [0057]      FIG. 9B  is an end view of a four-channel fluid cooler vessel and internal baffle assembly, according to the present invention. Fluid enters baffle assembly  900  from port  344  and flows along the first channel, formed between planes  912 ,  914 , and  916  (and a portion of the internal wall of vessel  310 ). Fluid then flows through aperture  918  in plane  916  into and along the second, intermediate, channel, formed between plane  916 , middle divider  920 , and plane  932  (and a portion of the internal wall of vessel  310 ). Fluid then flows through aperture  928  in middle divider  920  and into and along the third, intermediate, channel formed by plane  912 , middle divider  920 , and plane  936  (and a portion of the internal wall of vessel  110 ). Fluid then flows through aperture  938  in plane  936  and into and along the fourth, last, channel formed by planes  936 ,  934 , and  938  (and a portion of the internal wall of vessel  310 ), exiting through port  346 .  
         [0058]     As fluid passes through the channels, it exchanges heat with baffle assembly  900 , and vessel  310 . Heat exchange with vessel  310  is facilitated by larger internal fins  411  and smaller internal fins  413 . In some embodiments, baffle assembly  900  is made from material approximately 0.049 to 0.058 inches thick. Baffle assembly  900  is secured in vessel  310  against larger internal fins  411 , and can be tack-welded to keep it from shifting position in cooler  300 .  
         [0059]     Embodiments including four-channel, four-pass coolers are efficient for cooling of high-flow-rate coolants, for example, automobile oil and water cooling systems. An advantage of four-channel embodiments is that fewer, larger channels facilitate higher-flow-rates, and it is possible to cut larger apertures (as shown in  FIG. 9A ) between the baffles of four-channel assemblies.  
         [0060]      FIG. 10  is a perspective view of a cooler air flow assembly, according to the present invention. In some embodiments, cooler  300  is surrounded by air pipe  1010 . Air pipe  1010  directs air to pass by outer fins  312  of cooler  300 , drawing heat out of cooler  300  more efficiently than would static air. Air pipe  1010  has an inner diameter matching the outer diameter of fins  312 , for example 3-inches and can form a friction fit to cooler  300 . In some embodiments, air pipe  1010  has a wall thickness of 0.062 inches.  
         [0061]     In some embodiments, air pipe  1010  includes fan  1020 . Fan  1020  provides airflow through air pipe  1010  when there is no (or little) air flowing in direction  1011 . As an example, fan  1020  may be a 2.8 amp fan, operating at approximately 9500 rpm. In embodiments where cooler  300  is mounted on a vehicle, fan  1020  is capable of providing air flow when the vehicle is stopped or moving too slowly to provide sufficient air for heat exchange with cooler  300 . Heated air exits through air-port  1028 .  
         [0062]     In some embodiments, fan  1020  includes blade  1024  and is mounted in fan housing  1026 , by fan mount  1022 . Fan  1020  is provided with power over lines  1021 , which may be provided by a vehicle power system.  
         [0063]     In some embodiments a relay or switch (for example in vehicle  800 ) determines when power is provided to fan  1024 . In some embodiments, cooler  300  is provided with thermostat  1030  and control electronics  1032  (e.g., relay, electronic switch), so that fan  1020  may be switched on and off according to the temperature of cooler  300  (and thus the fluid inside it).  
         [0064]     While various embodiments of the invention have been described, it should be understood that they have been presented by way of example and not limitation. Those skilled in the art will understand that various changes in forms or details may be made without departing from the spirit of the invention. Thus, the above description does not limit the breadth and scope of the invention as set forth in the following claims.