Curved heat exchanger with low frontal area tube passes

A curved heat exchanger for a vehicle has tubes generally sector shaped in cross section and arranged in an arcuate pattern to transmit heat exchanger fluid between laterally spaced tanks. One embodiment has discrete heat exchanger fluid sections respectively connected to a vehicle engine, torque converter transmission and between the air conditioner compressor and evaporator. The tubes are tilted to align air passages therebetween with the radial direction of air flow discharged from an interior fan so that there is improved fan-heat exchanger matching resulting in reduced separation of air from the surfaces of the heat exchanger tubes and turbulence in the air passages. The side walls of adjacent tubes are equally spaced from one another to receive standard width air centers therebetween. The tubes may have discrete inner and outer flow sections insulated from one another and respectively employed to conduct engine coolant and another heat exchanger fluid such as for the air conditioning system. This invention features air pressure drop through the core so that a low horse power motor drive can be effectively utilized to pump cooling air through the heat exchanger. In another embodiment of the invention, axial flow fans are mounted at the ends of the cylindrical heat exchanger.

FIELD OF THE INVENTION 
This invention relates to heat exchangers, and more particularly to a heat 
exchanger having tubes arranged in a curved pattern with sector shaped 
cross sections presenting low frontal areas and providing pressure drop 
for improved flow of cooling air directed by an associated fan through the 
air centers between the tubes to improve heat exchanger and fan 
performance. 
DESCRIPTION OF THE RELATED ART 
U.S. Pat. No. 4,909,311, issued Mar. 20, 1990, discloses a cylindrical 
shaped heat exchanger mounted in a forward compartment of a vehicle with 
axial discharge fans at opposite ends of the radiator for exhausting air 
drawn through the core of the heat exchanger. 
U.S. Pat. No. 4,062,401, issued Dec. 13, 1977, discloses a toroidal like 
and segmented heat exchanger for a vehicle with discrete sections for 
cooling engine and transmission fluids, as well as a third section for 
cooling other hydraulic fluids. 
U.S. Pat. No. 2,650,073, issued Aug. 25, 1953, discloses a heat exchanger 
having concentric tubes with segments to divide each tube into discrete 
flow conducting passages. 
Japan Patent, document 0193088, discloses a cylindrical heat exchanger 
having inclined rows of heat exchanger fluid flow tubes therein extending 
through flattened plate type fins through which air is pumped by an 
internal blower. 
SUMMARY OF THE INVENTION 
This invention is drawn to heat exchangers and to new and improved heat 
exchanger tubes, to the arcuate arrangement of such tubes relative to a 
fan or blower, and to the employment of such tubes and tube arrangements 
to provide a plurality of discrete heat exchangers in a unitized package. 
The present invention provides a new and improved heat exchanger with tubes 
of sector shaped cross section arranged in a circular pattern with the 
ends thereof in operative communication with flow tanks, and having 
heat-dissipating air centers formed from corrugated rectilinear stock of 
substantially uniform widths for uniform spaced line contact with adjacent 
sides of the tubes. 
In some preferred arrangements, the tubes are tilted or inclined with 
respect to radial planes so that the air flow passages between adjacent 
tubes have improved alignment with respect to the resultant velocity path 
of the air stream pumped from the center of the heat exchanger core 
outward by an internal blower or fan so that resistance and turbulence is 
advantageously reduced. 
In another embodiment, axial flow discharge fans are located at the ends of 
the heat exchanger core so that air is drawn from the exterior of the core 
through the air centers to the center thereof, and then outwardly through 
the ends of the core. With interior air centers larger in width than the 
outer air centers, the core acts as a diffuser with advantageous air 
pressure drop through the core reducing the horsepower requirements of the 
fan. 
The present invention also provides new and improved tubes for a heat 
exchanger, each having a sector shaped cross section so that when tubes 
are arcuately spaced the side walls of adjacent tubes are substantially 
parallel and provide substantially equal and constant spaces therebetween. 
With this construction standardized, air center construction generally 
rectilinear in plan view can be employed therewith in a curved heat 
exchanger design. The cross section of the tubes is preferably enlarged to 
increase flow capacity, and thereby reduce fluid velocity to increase 
transit time for increased heat transfer to the cross flow of ambient air 
passing through the air centers. 
The present invention additionally can be employed as an engine cooling 
radiator arrangement for automobiles, which can be used with a transverse 
engine and with an engine driven fan internal of the radiator for 
optimized streamlining of the vehicle with low hood lines and preferably 
with air intake beneath the vehicle such as below the front bumper. 
It is a further feature, object and advantage of this invention to provide 
a new and improved heat exchanger with discrete and independent sections 
to function with plural heat handling mechanisms. 
Another feature, object and advantage of this invention is to provide a new 
and improved heat exchanger and fan match with tailored alignment of the 
air passages in the heat exchanger core with the discharge flow of an 
associated fan. 
These and other features, objects and advantages of the present invention 
will become more apparent from the following detailed description and 
drawings in which:

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Turning now in greater detail to the drawings, there is shown in FIG. 1 a 
portion of an automotive vehicle 20 having a liquid cooled internal 
combustion engine 22 operatively mounted within an accessible front 
compartment 23 of the vehicle. The engine is adapted to drive a 
hydrodynamic torque converter and automatic change speed transmission 24 
that powers the driving road wheels of the vehicle through differential 
gearing, not illustrated. 
The vehicle may have an air conditioning system that includes an evaporator 
26 located in a modular housing 28 located within the front compartment. 
Conventional blower 29 is driven to force air through the evaporator to 
cool the occupant compartment of the vehicle. 
The air conditioning system further includes a compressor and an 
accumulator diagrammatically shown at 33, and a condenser that may be 
provided by a discrete section of a cylindrical heat exchanger unit 30 
operatively mounted within the front compartment forward of the, engine 
22. The heat exchanger unit may have various configurations which are 
described in some detail below. 
The engine 22 has a conventional coolant system operatively connected by 
hoses, diagrammatically illustrated at 32 in FIG. 1, to an end tank of the 
cylindrical heat exchanger unit 30 as a whole, or alternatively, to a 
discrete first section thereof that is completely separate from other 
sections such as a second section that may, for example, be an air 
conditioner condenser section connected to the evaporator 21 and 
compressor 33 by lines 34. The transmission, for example, may also be 
hydraulically coupled by lines 35 to a third section of the heat exchanger 
unit, as will be later described. 
While as stated above, the heat exchanger of this invention can effectively 
service different discrete heat producing units, such as the internal 
combustion engine 22 and the transmission 24, and also provide the 
condenser section of the air conditioning system, it may be employed 
primarily as a radiator for the internal combustion engine. Such a 
construction is illustrated in FIGS. 2 and 3 in the form of a cylindrical 
core 40 and a pair of toroidal and laterally-spaced end tanks 42 and 44 
hydraulically interconnected to one another by elongated tubes 46, which 
conduct heat exchanger fluid from one end tank to the other. The tanks 42 
and 44 are suitably baffled, as disclosed in my co-pending application 
U.S. Ser. No. 537,497 referenced above, so that the flow is serpentined 
through the core provided by the tubes from a tank inlet 47 to a tank 
outlet 47'. 
Each of the tubes 46 is sector shaped in cross section and has side walls 
48 which diverge outward from a low profiled and rounded leading nose 
portion 50 to an outer peripheral back wall 52. With this construction, a 
streamlined tubes is provided so that air flow, flow arrows A, from the 
rounded nose portion outward flows smoothly and will tend to be laminar or 
at least have reduced boundary layer separation and reduced resultant 
turbulence. The tubes 46 are spaced from one another so that the diverging 
sides 48 of each tube are substantially parallel with the side wall of the 
next adjacent tube, as illustrated in FIG. 2. 
With this tube configuration and arcuate arrangement thereof, the 
interfacing sides 48 are equidistant from one another so that 
standardized, commercially available corrugated air centers 54 of 
substantially constant widths, width W-1 in FIG. 3A, can be operatively 
installed between the tubes to increase their heat exchanging efficiency 
and to increase the burst strength of the heat exchanger unit. These 
corrugated air centers importantly conduct heat energy from the coolant 
flowing through the tube passes and their large surface areas provide 
advanced cooling capacity as compared to disk or plate type cooling fins. 
Cooling air is forced through the air centers of the heat exchanger by a 
powered fan which may be of any suitable construction, such as the 
transverse centrifugal fan 56 best illustrated in FIGS. 2, 3, 4 and 5. 
When rotatably driven, the fan with rearwardly inclined fan blades 57 
pumps intake air fed from opposite ends of the radiator core 40, flow 
arrows B in FIG. 3, and then in a general radial direction outward through 
the air centers and past the sides of each of the tubes to the exterior of 
the unit, as illustrated by flow arrows A. This air carries heat energy 
from the engine heated coolant circulating through the tubes 46 between 
the tank 42 and tank 44, which is in turn operatively connected by the 
coolant transmitting hoses 32 to the coolant jacket of the internal 
combustion engine. 
The fan can be driven by any suitable means, such as by power take off from 
the vehicle engine as shown and described in my above referenced 
co-pending application, or by an electric motor as is employed in many 
vehicle applications. 
In any event, this invention is compatible to a wide range of fan 
constructions, and fan drives, since the small radiused forward ends 50 of 
the tubes present low frontal resistance for air pumped outwardly from the 
interior to the exterior of the cylindrical heat exchanger. Also, the 
exiting flow from the fan is substantially aligned with the air passages 
provided between the tubes, and since there is no restriction other than 
the minimal restriction of the air centers, the fan 56 can pump air 
through the core with high efficiency and minimized horsepower 
requirements. 
In viewing FIGS. 2, 2a and 3, it will be understood that when the 
transverse fan 56 is driven in a counterclockwise direction "D" at a 
predetermined RPM, the pumped air has a resultant velocity "V" which 
enters the core at angle "e", which is the angle between the peripheral 
velocity vector "F" and the radial component of the exit velocity "G". The 
air at resultant velocity "V" being the vector sum of the peripheral 
velocity "F", and the radial component of the exit velocity "G", enters 
the air flow paths formed between adjacent tubes 46. 
This invention importantly has improved alignment or matching of the angle 
of the cooling air flow paths with the exit angle of air pumped by the 
fan. As best shown in FIGS. 2 and 2a, the blades 57 of the transverse fan 
56 are inclined or curved in a rearward direction so that the resultant 
velocity "V" of the discharged air is aligned with the air flow passages 
provided between adjacent tubes, and accordingly, enters at an 
advantageous angle into the core of the heat exchanger. More particularly, 
with the resultant velocity having a predetermined exit angle, the tubes 
46 are correspondingly inclined or tilted along their major axes at the 
same angle, 12.degree. for example, relative to radial lines through the 
core originating at the center 0 of fan drive shaft 60 so that the flow 
channels provided by the air centers are optimally aligned with the 
direction of air pumped by the fan. 
With the streamlined envelope of each of the tubes, and with the air 
entering the air centers between the tubes at an angle which approximates 
the tilt angle of the tubes, the boundary air flow through the air centers 
past the tubes is primarily laminar and turbulence is substantially 
reduced. Furthermore, since resistance or back pressure is eliminated or 
reduced, there is an advantageous pressure drop. The fan-heat exchanger 
construction of this invention accordingly provides for optimized matching 
of these components with the fan pumping air through the core of the 
radiator with minimized horsepower requirement. 
Since the present invention provides for improved flow of air past the 
tubes, the fan can be driven with a low horsepower motor or by employing a 
drive from the engine which requires minimized input from the engine. 
Resultantly, this provides more engine power to drive the vehicle and 
other components, such as the air conditioner compressor and pumps for the 
engine coolant and power steering. 
The embodiments of the invention illustrated by FIGS. 4 through 8, are 
generally similar to that of FIGS. 2 and 3 but features important changes 
in the tubes and the core and tank construction. In this construction, 
each of the tubes 100 of the heat exchanger core 102 that extend between 
header plates 103 and 104, are divided throughout their lengths to provide 
discrete inner and outer sections 106 and 107 providing separate flow 
passages 108 and 109 therethrough. These sections and their flow passages 
are separated and effectively heat insulated by a web portion 110. The 
side walls of the web portion are continuation of the side walls of the 
outer section 107 until connected with the outer wall 116 of the inner 
section 106. As shown, the web portion 110 is trapezoidal in cross section 
having an outer wall 112 defining the lower limit of passage 109 of the 
outer section 107 and having an inner wall which is formed by a central 
portion of the outer wall 116 of the inner section 106. 
In this embodiment, the outer sections 107 of the tubes 100 are used for 
the engine cooling radiator fluid while the inner sections 106 are 
employed for the cooling of other components of the vehicle, such as the 
transmission oil and as condenser tubes for the air conditioning 
refrigerant. These tubes 100 are employed with separate and concentric 
arrangements of corrugated air centers 120 and 122. The outer sections 107 
are larger in width than the inner sections 106. The air centers 120 
between the outer sections 107 have substantially equal widths and are 
slightly wider than the air centers 122 between the inner sections 106 so 
that there is a progressively increasing opening for the cooling air 
pumped by the transverse fan 123 operatively mounted in the center of the 
core 102 to provide a large pressure drop across the core so that the 
horsepower requirements of the fan drive will be minimized. 
The web portion 110 between the sections can be provided with the openings 
126, shown in FIG. 6, so that air can flow from one side of each tube to 
the other, as shown by air flow arrows H to provide improved heat 
isolation of outer flow section 107 of the tube 100 with respect to the 
inner section 106. The tubes, such as shown in FIG. 6, can be extruded and 
the holes 126 punched subsequently therein. 
In this embodiment of the invention, the cylindrical heat exchanger core 
has concentric inner and outer heat exchanger rings 130 and 132 which are 
hydraulically isolated from one another to service different components of 
the vehicle. 
As best shown in FIG. 4, the outer ring 132 includes the outer section 107 
of each tube 100, the header plates 103, 104 through which the opposite 
ends of the tubes extend and the outer end tanks 134, 136 that are secured 
to the header plates by brazing or by any suitable means. "O" ring seals, 
such as seals 138 illustrated in FIG. 4a, are employed to prevent leakage 
of any fluids from the end tanks. Engine coolant is conducted from the 
engine through a hose, such as shown in FIG. 1, that is secured to an 
inlet pipe 140 operatively connected into end tank 134. The end tanks 134, 
136 are suitably partitioned by partition plates 142, 144 to provide for 
the serpentine flow through the outer ring of the heat exchanger in 
clockwise and counterclockwise directions until discharged through 
discharge pipe 148 that is operatively connected by a hose to the engine 
for return of the engine coolant, cooled by the outer ring of the heat 
exchanger. 
In addition to cooling engine coolant, the outer ring is capable of cooling 
other fluids such as that of the power steering system. As shown in FIG. 
4, the tank 136 houses a plurality of cooler plates 149 through which oil 
line 151 of the power steering system extends. These plates are located in 
a compartment in the tank 136, as defined by adjacent pairs of partition 
plates 144. Accordingly, as the engine coolant is circulated in the tank, 
power steering fluid supplied to the compartment by inlet tube has its 
heat energy transferred to the plates and then to the circulating coolant. 
As shown, the cooled power steering fluid is returned by the return side 
line 151. 
The transverse fan 123 has a plurality of rearwardly inclined blades 150 
operatively mounted by spoked support 152 to a centralized drive shaft 
154, which is driven by an electric motor or by a power take-off from the 
engine to pump cooling air therethrough. 
The tubes 100 are also generally of sector shaped cross section and are 
inclined, 12.degree. for example, with respect to a normal or a radius 
normally bisecting each tube so that the air passages through the core 
have improved alignment with the direction of air discharged by the fan. 
As in the previous embodiments, this alignment provides for improved air 
flow through the core with pressure drop. Pressure drop is further 
augmented since the air passages through the core as provided by the air 
centers and the sides of the tubes progressively increases in area from 
the interior to the exterior of the core. 
The inner ring 130 of the core comprises the inner sections 106 of the 
tubes, the inner portions of the header plates through which the ends of 
the tubes extend and arched crossover plates 160, (see FIGS. 4a and 6), 
brazed or otherwise secured, to the header plates to hydraulically 
interconnect adjacent inner sections of the tubes. These crossover plates 
eliminate the requirement for a tank construction such as employed on the 
outer ring, and connecting adjacent tubes for fluids requiring cooling 
such as the transmission fluid or the air conditioner refrigerant. 
Accordingly, a first pipe 164 from the air conditioner compressor is 
connected to a cover plate 165 of a first tube 166 of the interior ring, 
and the refrigerant fed thereto circulates in a serpentined manner in a 
counterclockwise direction until it exits through a terminal tube 167 that 
is connected by pipe 168 for return to the evaporator, such as evaporator 
26 in FIG. 1. 
In addition to serving as a condenser section of the air conditioning 
system, the inner ring can further cool the fluids of the automatic 
transmission. To this end, the heated oil pumped from the transmission is 
fed into pipe 169 and is then circulated in a serpentine counterclockwise 
manner by the inner ring of tubes to a return pipe 170 after being cooled 
by air flowing past the inner ring portion of the heat exchanger. 
The construction of FIGS. 7 and 8 is substantially the same as that of FIG. 
4 with variation in the crossover plate construction. As shown, the intake 
pipe 164 from the air conditioner compressor is connected to the inner 
ring by cover plate 165, Crossover plates 160 brazed to the headers 103 
and 104 interconnect the flow passages 108 of the inner sections of the 
tubes 100. The refrigerant can then circulate from the intake 164 in a 
serpentine manner through the tubes to the outlet pipe 168 which connects 
into the evaporator inlet. 
In the FIGS. 7 and 8 construction, only a small segment of the inner ring 
of tubes is used for transmission cooling. To this end, transmission oil 
inlet pipe 169 is connected to a fitting ;72 of an inlet plate 174 
covering the ends of three of the inner flow passages of the tubes 100. A 
crossover plate 176 at the opposite end of these tubes cover six tubes so 
that fluid flowing through the first three tubes can crossover to the 
adjacent three tubes and there pass to an outlet cover plate 178 that is 
connected by a fitting 180 to a return pipe 170 leading back to the 
transmission. 
Another embodiment of the invention is shown in FIGS. 9 and 10 in which a 
heat exchanger 200, having a cylindrical core 201, is arranged with axial 
flow fans 202 and 204 operatively mounted at the opposite ends thereof, 
which are rotatably driven to pull air radially inward from the 
circumference of the core to the central cylindrical opening 208 thereof, 
and then axially exhaust this air through opposite ends of the heat 
exchanger. 
In this embodiment, the heat exchanger core has an outer ring 210 of 
arcuately spaced fluid flow conducting tubes 212 that extend through 
laterally spaced header plates and are operatively connected to laterally 
spaced end tanks 214 and 216, which are partitioned as in the other 
embodiments to effect the serpentine flow of fluid through the tubes from 
the inlet pipe 218 to the outlet pipe 220 that are in turn operatively 
connected to the cooling system of heat generating equipment, such as an 
internal combustion engine. 
In addition to the outer ring of tubes 210, the heat exchanger further 
includes in an inner ring 222 of fluid conducting tubes 224 that are 
entirely separate from the outer ring and are operatively connected to 
other equipment requiring a heat exchanger to effect the removal of heat 
energy from fluids circulating therethrough. Inlet and outlet pipes 226, 
228 and 230, 232 respectively, illustrate the feed and exhaust of the 
fluids from the inner ring of the heat exchanger. 
Importantly in this embodiment, a drop in air pressure occurs as the 
cooling air flows from the periphery of the core to the central opening. 
As shown in FIG. 9, the outer tubes 212 are sector shaped in cross 
section, and are arcuately spaced from one another so that constant width 
air centers 236 of corrugated thin wall sheet metal can be employed. With 
this construction, there is full contact by the apices of the air centers 
with the side walls of the tubes 212 for improved conduction of heat 
energy. 
The inner ring 222 of tubes is separate and concentric with respect to the 
outer ring and has arcuately spaced tubes 224 with sector shaped cross 
sections. The annular space 239 between the concentric rings of tubes 
provides effective insulation between these separate heat exchangers. 
As illustrated, the sides of each of these tubes 224 are also parallel to 
the sides of the next adjacent tube so that constant width air centers 240 
can be employed with the inner ring of tubes. These air centers are 
somewhat wider than the air centers 236 of the outer ring so that the air 
passages open as the fans pull air from the exterior of an core to the 
interior thereof so that the advantageous pressure drop is provided. 
While the above description constitutes preferred embodiments of the 
invention, it will be appreciated that the invention can be modified and 
varied without departing from the scope of the accompanying claims.