CA1044972A - Combination fan shroud and toroidal radiator - Google Patents

Abstract

A COMBINATION FAN SHROUD AND TOROIDAL RADIATOR
ABSTRACT OF THE DISCLOSURE
A contoured shroud exit having at least a part of a fan located therein is positioned generally within a round radiator. The fan generated air stream is directed substan-tially straight against and over all the inner face of the radiator core.

Description

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A COMBINATION FAN SHROUD AND TOROIDAL RADIATOR

SPECIFICATION
I
This invention rela-tes to a cooling assembly and more particularly to a round radiator having a contoured fan shroud exit section capable of pressure gradient bending and a fan located therein.
Most vehicles in general use today are driven by internal combustion engines. These engines being heat producing are for the most part water cooled, that is the engine is jacketed or otherwise suitably engineered such that water is accessible to take up the engine produced heat. A radiator is used for cooling the liquid circulating around the engine by dissipating the heat to an air stream. Air flowing through the core of the radiator absorbs the heat and carries it out into~the atmosphere. The amount of heat dissipate~ as a result is related to the size of the radiator core and the amount of air passing therethrough.
For the most part the radiators in use today -employ a flat type core. That is, the flat rectangular type of radiator found in an automobile or truck for example. It has been found, however, that rouncl radiators, ~0~97;~
that is a radiator wherein the core is wrapped in a circle xesembling a drum shell, can be positloned in the same location as a traditional flat radiator and presents a greater face area than the flat radiator. ~ore speci-fically, the flat radiator occupies a certain amount of space on a horizontal axis from the front face thereon to the trailing edge of the fan. If a round radiator is designed to fit within this same location it has been - determined a greater face and as a result greater core area can be contained herein because of the more expedient use of the available space.

In a standard type of round radiator employln~ a blower type Ean with a venturi type shroud air is drawn from the atmosphere into the plenum inside the radiator and is then bent and forced to exit radially through the core.
A barrier seals off the back part of the drum and thus E~rces the `
air within the plenum to flow outwardly throuqh the core. For the most part the fan generated air stream is generally directed axially back from the blades of the fan. Baffle means have been employed which attempt to deflect the air radially after it leaves the blades of the fan. These, however, have not met with a great success. Additionally, the entire core area of the radiator is not employed for cooling purposes simply because of the nature of the non-uniformly distributed air currents therein.

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For best efficiency, it is desirable tha-t the discharge of the fan be in a radial direction that is outwardly in a plane perpendicular to the face of the radiator core and spread or at least distributed uniformly across the entire face of the core from one end to the other.
In accordance with this invention a radia-tor and shroud capable of pressure yradient bending, such as described in a Canadian paten-t application Serial No. 184,880 by Harold Beck and filed on November 2, 1973, IIOW Patent No. 992,~09 of July 6, 1976, are employed in combination with a round radlator. The round radiator has a fxont side means, a rear side means and a core wherein are openings. A shroud means as described in the above identified application is , posi~ioned adjacent said front side means and the fan positioned within the shroud. The resulting air flow pattern generated by this arrangement is generally radial v in nature and directed straight against the face of the core of the round radiator in a plane generally parallel to that of the radiator core openings.
Therefore, it is an object of this invention to provide a round radiator having a shroud exit and fan located therein such that an air stream generally parallel to the core openings of the radiator is directed across the entire face of the core. Still another objec~t of this invention is to provide a round radiator and a contoured fan shroud exit and fan located therein wherein the diameter of the radiator and the diameter of the fan and shroud assembly are such that the radial discharge pattern of the air stream spreads across the entire face of the core of the radiator. Another obJect of this invention is to provide a vehicle having a round radiator ",~ ~o~s~z Q,)d a contoured shroud exit and fan means located therein.
Yet another object of this invention is to provide a ro~lnd radiator having a contoured shroud exit and fan located therein where said fan has a barrier means whereby recirculation in the hub areas is prevented. Still another object of this invention is to provide a round radiator wherein the plane of the cooling air stream is generally parallel with the plane of the core openings. Another object of this inven-tion is to provide a r round radiator having a shroud exit and fan located therein in combination with a flat radiator. Still another object of this invention is to provide a round radiator in combination with a contoured shroud exit having interrupted sections with a fan therein whereby air can be directed radially against a round radiator or axially against a flat radiator.
Yet another object of this invention is to provide A round radiator having an exit shroud section capable of pressure gradient bending and a fan located at least partially therein.
A further object of this invention is to provide a method for handling an air stream to direct it against a round heat exchanger to achieve maximum air flow therethrough.
Yet another object of this invention is to provide a cooling system wherein a cooling air stream entrains up to 20 X
its volume in additional air.
Thus broadly, the invention contemplates a heat exchange apparatus which comprises a heat exchanger means including a toroidal radiator structure with the toroidal radiator structure including a toroidal radiator core having a plurality of radially extending cooling air passageways formed therethrough and with the toroidal radiator structure further including a first radially extending wall and a second radially r; ~ i ) 9~7Z
extending wall axially spaced and substantially parallel .~
with respect to the first wall. The first and second walls ;
substantially define the axial limits of the toroidal radiator core and an air-receiving plenum chamber is disposed radially inwardly of the toroidal radiator core. A rotatable, axial flow fan has a plurality of circumferentially spaced, radially extending impeller blades, and a generally annular fan shroud means is supported within an opening formed through the first wall and encircling the fan. The fan shroud means includes a generally cylindrical, axially extending throat ,_ section, an annular, generally radially extending flat flange section with the flat flange section beiny spaced radially outwardly and axially from the throat section, and an annular intermediate section extending between and operatively interconnecting the throat section and the radial flat flange section. The throat section, intermediate section, and radial flat flange section are effective to produce a low pressure region between the air stream flowing over the surface thereof and such surface when the fan is in operation.
Other objects and advantages of the invention will become apparent upon reading the following de-tailed description and upon reference to the clrawings, in which:

FIGUP~ 1 is a side elevation of a vehicle having an internal combustion engine showing the device of my invention attached thereto;
FIGURE 2 iS a front view of a round radiator having a contoured shroud exit and fan located therein;
FIGURE 3 is a fragmentary cross sectional side ; elevation of the round radiator showing the contoured shroud exit with the fan therein some portions being shown in schematic and an air discharge graph thereabove;
FIGURE 4 iS also a fragmentary c~oss sectional side elevation with some portions being shown in schematic wherein the diameters of the contoured shroud assembly and the round radiator have been taken into ccnsicleration and an air barrier has been provided in the hub region and an air discharge graph thereabove;
FIGURE 5 is prior art design with an air discharge graph thereabove;
FIGURE 6 is a fragmentary cross se~tional side elevation of the round radiator having a suction type fan and a seconcl smaller round radiator carried therein; and FIGURE 7 is a front view of a contoured fan shroud exit having interruption section means.
While ~he invention will be described in con-nection with a preferred embodiment, it w-ll be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.

Turning first to Figure l wherein is shown a conventional water cooled heat producing internal combus-; tion engine means 10 forwardly carried on longitudinally extending parallel support means 12 of vehicle means 14.
As shown herein vehicle means 14 is a truck, however, as will hereafter become more apparent this invention can be applied to any type of vehicle employing a heat generating internal combustion engine or any portable or stationary device requiring an air moving fan means.
Forwardly mounted on vehicle means 14 i5 a water cooledround heat exchanger means 16 employed to dissipate t:he engine generated heat. Water flows thro~gh a water jacket in the engine (not shown) and through the heat exchanger or radiator in the preferred embodiment via a series of fluid communicating means 18 and 20. In this particular embodi-ment sheet metal means 22 encircles engine means lO thereby forming the engine compartment area 24.
Carried at the for~tard end of engine means lO
is a fan shaft means 26 which delivers power to drive fan means 28. As is apparent, the particular mode whereby power is transmitted from the engine or other source to the fan means is not critical and belts or pulley, etc. could be employed.
The radiator means 16 is of the round or toroidal radiator type, that is the core means 30 is wrapped in a circle resembling the shell of a drum. Air Elows through the core means 30 via channel means indicated by 32. These core channel means 32 generally extend straight through the core from inner face means 34 to J~

outer face means 36. The nature and construction of the core means 30 either in a round radiator or a standard flat radiator is substantially tne same with the exception being the toroidal configurat:ion of the overall design versus the generally flat rectangular design.
The radiator fan shroud exit section means 38 or contoured exit shroud means includes a tubular means 40, arcuated means portion 42 and flat flange portion 44 all shown in Figure 3. For the most part tubular means 40 forms the leading edge of the contoured exit shroud means while arcuated portion 42 extends generally rearwardly in a simultaneously expanding outwardly around an arc, the reference point of which is defined as point 46.
That is, arcuated section 42 has a general horn-shaped appearance being a section of a transition surface or some approximation thereof. In the preferred embodiment arcuated section 42 is a section of a constant radius arc. Flat flange portion 44 forms a trailing edge of exit shroud means 38 and has a major plane edge generally perpendicular to that of tubular section means 40. For purposes of simplicity, tubular means 40 will hereafter be referred to as the cylindrical throat means, arcuated portion 42 will be referred to as the radial expanding means and flat flange portion 44 will be referred to as the radial flat means. The leading edge means 48 of cylindrical throat means 40 defines a front of the plane generally parallel with that plane formed through radial flat portion 44.
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1044~72 It is believed that it is the function of the shroud exit to produce pressure gradient bendlng or more specifically the Coanda effect. As explained in my co-pending application S.N. 184,880, now Canadian Patent No. 992,409 of July 6, 1976, a fan shroud exit capable of producing pressure gradient bending can be employed with many beneficial results.

The fan means is rotatably carried within exit shroud means 38 and operates to establish a flow of cooling air. Fan means 28 includes a plurality of fan blade means 50 (only one of which is shown) as is well known in the~art and as shown in this example is a blower type fan. As shown in Figure 3 fan means 28 is surrounded by a contoured fan shroud exit section means 38. Additionally the tip clearance, that is the distance from the tip region of 52 of the fan to the contoured exit shroud 38 has been minimized to imp oved results.
The enclosure of fan means 28 within contoured exit shroud means 38 is such that a front plane is struck out by leading edge 54 which is coextensive and passes through the leading section of throat means 40 and a rear plane is struck out by a trailing edge means 56 is coextensive and parallel with the plane passing through said radial flat portion means 44. It should be noted, however, that there is a plus or minus error factor involved in this positioning of about 12 percent of the axial width AW of the fan blade. That is, the respective planes formed by the blade means can be within _ g _ :
about 12 percent of the optimum and still function satis-factorily within the scope of this invention.
It has been determined, however, that best results are obtained when the front plane struck out by leading edge means 54 passes through the plane formed by the leading edge 48 of the throat section 40. Even more determinative on the result is the relationship between the rear plane struck out by trailing edge means 56 and the radial flat portion 44. Overall per-formance is achieved when the rear plane and the radialflat portion 44 are coextensive and parallel. Deviations from this orientation causa the air stream to change more rapidly than corresponding percentage changes in the front plane location.
The following relationship exists between these parameters: RF = AW/3, CF = AW/3, and R = 2AW/3 where RF is the length of the radial flat portion 44, CF iS the length of the cylindrical throat section 4~ and R is a radius of the radial expanding section 42 or distance from the reference point to the transitior surface and AW is the projected axial width of fan 28. It should also be noted that these relations can vary by about as much as 12 percent of AW.
Referring now to Figure 5, the prior art design, it should be noted that the state of the art today is such that this is considered to ke a generallv efficient assemblage. That is the venturi shroud termina-ted at about the mid-point of the fan blade and the fan is generally forwardly located in the radiator. A disc 80 seals the engine ~0 side of the core so that the air collected in the core :is forced to exit through the radial openings 32 in the core. Positioned above the schematic of the assembly is a graph showing ~7 -10-the manner in which air is being forced through the radiator core. Air is passing through the rear parts of the radiator core at a high velocity while in the far forward section substantially less air passes through the core. As is apparent the forward section of the radiator is not serving its designed purpose.
Referring to Figure 3 wherein is shown an embodiment of the invention herein disclosed. Considera-tion is immediately directed to the velocity of the air flow leaving the radiator. As i5 apparent there is a substantial improvement over that shown in Figure 5 in that there is air flowing through all portions of the radiator core and not just the front or the back sections thereof. The contoured exit section means 38 can be secured to the radiator means 16 with any type of suitable bracket means, however, most suitable is a large ring member means such as 60 shown in (Figure 2). Because it is generally an annulus the outer edge 62 thereof may be secured to the radiator, the inner edge 64 to the contoured exit shroud 38 whereby the passage of any air into the plenum area must be through the fan blades or through the radiator core. Additionally an optional inlet shroud 66 (Figure 3) may be secured to the leading edge means 48 of contoured fan shroud 38 to provide a means whereby air can be funneled to the fan and take advantage of any kind of ram effect achieved by the vehicle's movement in a forward direction. With this particular arrangement of inlet means, shroud means, and ring carrier means 60, the shroud assembly follows movement of the radiator. The engine side or other end of the radiator core is capped by a disc or baffle 80 and the disc or baffle is secured to the engine so the entire 497~

assembly moves as a single uni~. The second disc 80 has an opening for connecting or power coupling the fan shaft 26 to the engine 10. Such an assembly is vital to maintaining a constant fan tip clearance. However, it should be understood that the invention would function if these components were independently linked or groups -thereof were independently secured to the vehicle frame.
Turning now to Figure 4 which shows another embodiment of this invention. Herein certain conditions have been optimized, most specifically the diameter of the radiator means 16 and the diameter of the fan shroud exit 38 and fan means 28 have been optimized to get full spread of the air stream across the face of the radiator.
This is shown in -the chart of the air velocity leaving the radiator. As is apparent it is more evenly spread over the full radiator core. This even distribution is achieved by centering the fan blast discharge in the round radiator 16 and by taking advantage of the fact that an air stream normally diverges at an angle of about 7 degrees, (3-1/2 to both sides oE centerline)~ from its source.
By choosing the relative diameters of the round radiator 16, the shroud, and fan assembly adequate distance can be left therebetween that the radially directed air stream diverges sufficiently such that it is spread entirely across the face of the radiator.
An additional feature of this embodiment is the barrier means 68 which prevents recirculation by the fan in the hub region 70. The air barrier prevents 1~4~972 the fan means 28, in the hub regions 70, from pulling air from the plenum axea or from behind it and recircu-lating it. The air barrier or disc 68 is of such dimensions that it does not interfere with the radial discharge of the air stream yet prevents such recirculation. Reference should be made to my co-pending Canadian patent application serial No.
213,118, filed November 6, 1974, wherein such barriers are more fully discussed. In the embodiment shown in Figure g it should be noted that the contoured fan shroud exi-t section 38 is positioned substantially inwardly such that the plane skruck out by the radial flat means 44 is about in the middle of round radiator 16.
The fan msans 28 being appropriately positioned with respect thereto, It is thus necessary to provide a bracket means 72 which bridges the distance between the circular ring means 60 and the leading edge 48 of the throat section.
As the ring means section 66 prevents the passage of air so does the kracket means 60, that is it is a solid section whereby no air can pass therethrough.
I-t should be noted that the assembly herein disclosed could be also employed with a suction type of fan. This embodiment is shown in Figure 6 wherein the fan means 28 draws air out of the plenum region ràther discharging into it. As shown the exit shroud means 38 is reversed in location. A second smaller round heat exchanger means 81 is shown in combination therewith.
As stated earlier it would be possible to use the assembly herein described in combination with a flat radiator located in an aperture in barrier means 73 as ~0 shown in Figure 1. In the art today it is very common ,972 to employ separate radiators to cool the hydraulic fluid, the air conditioning fluid etc., employed by the vehicle.
This is done most simply by positioning second, third, fourth, and etc., radiators in the area of the fan assembly.
It is disclosed in the patent application serial No. 184,881, filed on November 2, 1973, now Canadian Patent No. 989,264 of May 18, 1976, by Beck and Hanna, that by providing interruption section means in the contoured radial fan shroud it is possible to destroy the ability thereof to direct the air in the radial direction. As a result in these areas the air stream is essentially moving in the axial direction, that is generally parallel with the fan shaft in the examples herein disclosed. An overall assemblage is thus described wherein part of the air flow is radial in direction and part of the air flow is axial in direction. Thus if the design as shown in Figure 1 were pro~ided with a contoured exit section such as shown in Figure 7 with the interrupted section means 74 and the flat radiator means 71 were positioned directly behind this interrupted section means the flat radiator could be provided with a direct blast of cooliny air.

The cooling of a multiplicity of liquids could also be achieved by the employment of a radiator core which is multi-cooling. That is the radiator is divided into a number of sections which are not in the fluid communication with each section being employed for the cooling of a different liquid. That is a multi-coolan-t radiator, part of the core being employed to cool engine coolant, another section employed -to cool hydraulic fluid, and possibly a third section being employed to cool the air conditioning fluid.

~:14~72 Referring to the design shown in Figure 4 it should be noted that with the removal of the bafEle means 73, shown in Figure 1, the air stream created by the fan means will entrain additional air from the plenum region.
That is, the high speed air flow passing over the pressure gradient bending shroud surface will entrain other air creating a larger although slower moving air stream. With the removal of the barrier from the rear section of the round radiator means 16 an additional source entrainable air is provided. ~t this time it is known that a jet passing over a Coanda effect producincJ surEace entrains up to 20 times the amount of air in the original jet. When a fan means is employed to create the air stream i-t may be that some of the air moved by the fan contributes to this volume or all of it may come from the plenum region. The entrainment does, however, provide a substantial increase in the volume of cooling air moving through the core of the radiator.
A heat transfer system for an internal combustion engine comprising a round radiator, a contoured shroud exit means capable of pressure gradient bending, and a fan means generally or at least partially positioned therein has thus been described. The critical feature of the invention is that a contoured shroud exit means is employed which is capable, in combination with the fan, of pressure gradient bending. More specifically, the shroud must be designed such that a Coand~ like effect can be created thereby, when the high speed fan generated air stream is passed thereover. This air stream is then directed out radially in a direction generally perpen-dicular to the face oE the round radiator but parallel ,J;~

to the radiator core openings. By such tailoring of the air stream its cooling abilities are enhanced as well as the inherent benefits such as horsepower savings and noise reduction which are achieved with contoured fan shrouds capable of producing a Coanda effect. It should be understood that the term "pressure gradient bending" is broader than the term Coanda effect. That is, it is believed that the Coanda effect is a type of pressure gradient bending. ~or the lack of better ter-minology and a complete understanding of the phenomenonwhich is occurring in the tip portions of the fan blade, ; when these particular shroud configurations are employed ~pplicants have employe~ these -terms to describe what they believe is happening.
Thus it is apparent that there has been provided, in accordance with the invention, a heat transfer system that fully satisfies the objects, aims, an~ advantages set forth above. While the invention has been desc~ibed in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. ~ccordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.

Claims (22)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A heat exchange apparatus comprising:
a heat exchanger means including a toroidal radiator structure, said toroidal radiator structure including a toroidal radiator core having a plurality of radially extending cooling air passageways formed therethrough, said toroidal radiator structure further including a first radially extending wall and a second radially extending wall axially spaced and substantially parallel with respect to said first wall, said first and second walls substantially defining the axial limits of said toroidal radiator core and an air-receiving plenum chamber disposed radially inwardly of said toroidal radiator core;
a rotatable, axial flow fan having a plurality of circumferentially spaced, radially extending impeller blades; and a generally annular fan shroud means supported within an opening formed through said first wall and en-circling the fan, said fan shroud means including a gener-ally cylindrical, axially extending throat section, an annular, generally radially extending flat flange section, said flat flange section being spaced radially outwardly and axially from said throat section, and an annular inter-mediate section extending between and operatively inter-connecting said throat section and said radial flat flange section, said throat section, intermediate section. and (Claim 1 Cont'd.) radial flat flange section being effective to produce a low pressure region between the air stream flowing over the surface thereof and such suface when the fan is in operation.

2. A heat exchange apparatus as set forth in Claim 1, wherein said impeller blades have an effective axial width, AW, measured along the rotational axis of the fan between a first plane and a second plane, said planes being axially spaced and parallel with respect to each other and disposed substantially normal to the rotational axis of the fan, said first and second planes extending radially, respectively, through a point on the leading edge of each of the impeller blades at the radially outermost, tip region thereof and through a point on the trailing edge of each of the impeller blades at the radially outermost, tip region thereof, the radially outermost, tip region of each of said impeller blades having a radial length of approximately 1/3 of the radial length of the impeller blade, one of said first and second planes being substantially coincident with the radial plane containing a first axial end of said throat section; and wherein said intermediate section extends between and operatively interconnects a second axial end of said throat section and said radial flat flange section.

3. A heat exchange apparatus as set forth in Claim 2, wherein the other one of said first and second planes is substantially coincident with the radial plane containing the juncture of said intermediate section and said radial flat flange section.

4. A heat exchange apparatus as set forth in Claim 3, wherein said one of said first and second planes substantially coincident with the radial plane containing a first axial end of said throat section may be axially spaced from and on either axial side of such radial plane a dis-tance of 12 percent of AW, and said other one of said first and second planes may be axially spaced from and on either axial side of said radial plane containing the juncture of said intermediate section and said radial flat flange section a distance of 12 percent of AW.

5. A heat exchange apparatus as set forth in Claim 4, wherein in said intermediate section is radially curved, and wherein the following relationships exist:
RF = AW/3 plus or minus 12 percent of AW, CF = AW/3 plus or minus 12 percent of AW, and R - 2AW/3 plus or minus 12 percent of AW, where RF is is the radial length of the radial flat flange section, CF is the axial length of the cylindrical throat section, and R is the radius of curvature of the intermediate section.

6. A heat exchange apparatus as set forth in Claim 1, including air recirculation barrier means con-tiguous to the air discharge side of said fan for obstruct-ing axial flow of air from the air discharge side toward the air intake side of the fan at the hub region of the fan.

7. A heat exchange apparatus as set forth in Claim 2, including air recirculation barrier means for (Claim 7 Cont'd.) obstructing axial flow of air in one direction through the fan at the hub region thereof when the fan is in operation, said air recirculation barrier means including a generally flat and substantially imperforate circular disk, said disk lying generally in a radial plane disposed on the air discharge side of the fan, said disk being axially spaced and substantially parallel with respect to said second radial plane extending radially through a point on the trailing edge of each of the fan impeller blades at the tip region thereof.

8. A heat exchange apparatus as set forth in Claim 1, wherein said axial flow fan is of the blower type, said fan drawing air generally axially from the exterior of said toroidal radiator structure and discharging the same into said plenum chamber, said fan-generated air stream discharged into said plenum chamber having a major velocity component in a radially outward direction.

9. A heat exchange apparatus as set forth in Claim 1, wherein said axial flow fan is of the suction type, said fan drawing air generally axially form said plenum chamber and discharging the same exteriorly of said toroidal radiator structure, said fan-generated air stream discharged exteriorly of said toroidal radiator structure having a major velocity component in a radially outward direction.

10. A heat exchange apparatus as set forth in Claim 1, including auxiliary heat exchange means mounted on said toroidal radiator structure comprising, an auxiliary radiator structure including an auxiliary radiator core, said auxiliary radiator core having a plurality of cooling air passageways formed therethrough, said air passageways providing air communication between the exterior of said toroidal radiator structure and the interior of said plenum chamber.

11. A heat exchange apparatus as set forth in Claim 5, including auxiliary heat exchange means mounted on said toroidal radiator structure comprising, an auxiliary radiator structure including an auxiliary radiator core, said auxiliary radiator core having a plurality of cooling air passageways formed therethrough, said air passageways providing air communication between the exterior of said toroidal radiator structure and the interior of said plenum chamber.

12. A heat exchange apparatus as set forth in Claim 11, wherein said auxiliary heat exchanger means is mounted about an opening formed through said second wall of said toroidal radiator structure.

13. A heat exchanger apparatus as set forth in Claim 12, wherein said axial flow fan is of the suction type, said fan drawing air generally axially from said plenum chamber and discharging the same exteriorly of said toroidal radiator structure, said fan-generated air stream (Claim 13 Cont'd.) discharged exteriorly of said toroidal radiator structure having a major velocity component in a radially outward direction.

14. A heat exchange apparatus as set forth in Claim 13, wherein said auxiliary radiator core is of the flat slab type, and each one of said plurality of cooling air passageways formed through said auxiliary radiator core extends substantially in an axial direction therethrough.

15. A heat exchange apparatus as set forth in Claim 13, wherein said auxiliary radiator core is of the toroidal type, each one of said plurality of cooling air passageways formed through said auxiliary radiator core extends substantially in a radial direction therethrough.

16. A heat exchange apparatus as set forth in Claim 11, including air recirculation barrier means for obstructing axial flow of air in one direction through the fan at the hub region thereof when the fan is in operation, said air recirculation barrier means including a generally flat and substantially imperforate circular disk lying generally in a radial plane disposed on the air discharge side of the fan, said disk being axially spaced and sub-stantially parallel with respect to said second radial plane extending radially through a point on the trailing edge of each of the fan impeller blades at the tip region thereof.

17. A heat exchange apparatus as set forth in Claim 5, wherein said axial flow fan is of the blower type, said fan drawing air generally axially from the exterior of said toroidal radiator structure and discharging the same into said plenum chamber, said fan-generated air stream discharged into said plenum chamber having a major velocity component in a radially outward direction; and further including air recirculation barrier means for obstructing axial flow of air in one direction through the fan at the hub region thereof when the fan is in operation, said air recirculation barrier means including a generally flat and substantially imperforate circular disk lying generally in a radial plane disposed on the air discharge side of the fan, said disk being axially spaced and substantially parallel with respect to said second radial plane extending radially through a point on the trailing edge of each of the fan impeller blades at the tip region thereof.

18. A heat exchange apparatus as set forth in Claim 5, wherein said axial flow fan is of the suction type, said fan drawing air generally axially from said plenum chamber and discharging the same exteriorly of said toroidal.
radiator structure, said fan-generated air stream discharged exteriorly of said toroidal radiator structure having a major velocity component in a radially outward direction;
and further including air recirculation barrier means for obstructing axial flow of air in one direction through the fan at the hub region thereof when the fan is in operation, said air recirculation barrier means including a generally (Claim 18 Cont'd.) flat and substantially imperforate circular disk lying generally in a radial plane disposed on the air discharge side of the fan, said disk being axially spaced and sub-stantially parallel with respect to said second radial plane extending radially through a point on the trailing edge of each of the fan impeller blades at the tip region thereof.

19. A heat exchange apparatus as set forth in Claim 11, wherein said axial flow fan is of the blower type, said fan drawing air generally axially from the exterior of said toroidal radiator structure and discharging the same into said plenum chamber having a major velocity component in a radially outward direction.

20. A heat exchange apparatus as set forth in Claim 19, wherein said auxiliary heat exchanger means is mounted within an opening formed through said second wall of said toroidal radiator structure and each one of said plurality of cooling air passageways formed through said auxiliary radiator core extends substantially along an axis spaced and substantially parallel with respect to the rotational axis of the fan; and means for causing a portion of the fan-generated air stream discharged into said plenum chamber to have a major velocity component in an axial direction.

21. A heat exchange apparatus as set forth in Claim 20, wherein said opening formed through said second wall of said toroidal radiator structure in which said auxiliary heat exchanger means is mounted is located so as to position said auxiliary radiator core to be substantially in the path of that portion of the fan-generated air stream discharged into said plenum chamber having a major velocity component in an axial direction.

22. A heat exchange apparatus as set forth in Claim 21, wherein said means for causing a portion of the fan generated air stream discharged into said plenum chamber to have a major velocity component in an axial direction includes a discontinuity in the continuous annular contour of said fan shroud means, said discontinuity being in the form of an arcuately extending, notched section in said fan shroud means, said notched section being effective to cause that portion of the fan-generated air stream flowing there-over to flow generally in an axial direction.