HEAT EXCHANGER
BACKGROUND OF THE INVENTION
[0001] The subject matter disclosed herein relates to a heat exchanger and  more particularly  a heat exchanger for an electrical machine.
[0002] Heat exchangers typically employ tube bundles that are aligned with or orthogonal to an electrical machine shaft direction where there is a single entrance and a single outlet for cooling media. The tube bundles are generally separated into a first group and a second group. Each tube in the first group of tube bundles removes heat from heated airflow being directed away from the electrical machine. The cooled air is then carried back to the electrical machine and cooled again by the second group of tubes.
[0003] With this configuration  a pressure drop due to distributed friction loss or drag normally occurs along at least the first group of tubes. Also  a temperature difference between the heated air and the cooling media of the first group of tubes decreases along the tube lengths. As a result  a degree of cooling of the heated air is decreased given a volume of heated air and a volume of cooling media.
BRIEF DESCRIPTION OF THE INVENTION
[0004] According to one aspect of the invention  a heat exchanger is provided and includes a housing disposed proximate to a heat source  the housing having sidewalls forming an enclosure  a baffle defining in the enclosure a ventilation circuit thermally communicative with the heat source  and central walls defining a main channel bisecting the ventilation circuit along which cooling media flows and a tube extending through a bisected portion of the ventilation circuit and fluidly coupled to the main channel and a housing exterior to direct the cooling media from the main channel  through the bisected portion of the ventilation circuit and to the housing exterior.
[0005] According to another aspect of the invention  a heat exchanger is provided and includes a housing disposed proximate to a heat source  the housing having sidewalls forming an enclosure  at least one baffle defining in the enclosure a ventilation circuit having at least one first section along which heated air flows away from the heat source and at least one second section along which cooled air flows toward the heat source  and central walls defining a main channel bisecting each of the at least one first and second sections of the ventilation circuit along which cooling media flows and a plurality of tubes respectively extending through bisected portions of the at least one first and second sections of the ventilation circuit  each of the plurality of tubes being fluidly coupled to the main channel and a housing exterior to direct the cooling media from the main channel through the bisected portions of the at least one first and second sections of the ventilation circuit and to the housing exterior.
[0006] According to yet another aspect of the invention  an apparatus is provided and includes an electrical machine  a heat exchanger having a housing disposed proximate to the electrical machine and having sidewalls forming an enclosure  at least one baffle defining in the enclosure a ventilation circuit having at least one first section along which heated air flows away from the electrical machine and at least one second section along which cooled air flows toward the electrical machine  and central walls defining a main channel bisecting each of the at least one first and second sections of the ventilation circuit along which cooling media flows and a plurality of tubes respectively extending through bisected portions of the at least one first and second sections of the ventilation circuit  each of the plurality of tubes being fluidly coupled to the main channel and a housing exterior to direct the cooling media from the main channel through the bisected portions of the at least one first and second sections of the ventilation circuit and to the housing exterior.
[0007] These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The subject matter  which is regarded as the invention  is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features  and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
[0009] FIG. 1 is a side sectional view of an electrical machine;
[0010] FIG. 2 is an axial view of the electrical machine of FIG. 1; and
[0011] FIG. 3 is a perspective view of a heat exchanger of the electrical machine of FIGS. 1 and 2.
[0012] The detailed description explains embodiments of the invention  together with advantages and features  by way of example with reference to the drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0013] In accordance with aspects of the invention  two cooling circuits are provided in parallel with one another to reduce a length that cooling airflow travels. As a result  a pressure drop due distributed friction loss or drag is reduced and  as a length of a bundle is reduced  a more uniform temperature difference between cooling media and tube walls is available.
[0014] With reference to FIGS. 1-3  an apparatus 10 is provided. The apparatus 10 includes a heat source  such as an electrical machine 20 or some other similar machine and a heat exchanger 30. The heat exchanger 30 has a housing 40 disposed proximate to and in thermal communication with the electrical machine 20. The housing 40 includes sidewalls 41 that cooperatively form a volumetric enclosure 42 therein  at least one baffle 43 and central walls 44. The at least one baffle 43 is supported by the sidewalls 41 and defines in the enclosure 42 a ventilation circuit 45 having at least one first section 450 along which heated air flows away from the electrical machine 20 and a second section 451 along which cooled air flows toward the electrical machine 20. The central walls 44 are also supported by the sidewalls 41 and define a main channel 46. The main channel 46 bisects each of the at least one first and second sections 450  451 of the ventilation circuit 45. Cooling media  such as air pumped by an external fan  flows along the main channel 46 and through ventilation circuit 45 as will be discussed below.
[0015] The heat exchanger 30 further includes a plurality of tubes 50 that respectively extend through bisected portions of the at least first and second sections 450  451 of the ventilation circuit 45. Each of the plurality of tubes 50 is fluidly coupled to the main channel 46 and a housing exterior 460 and is thereby configured to direct the cooling media from the main channel 46 through the bisected portions of the at least one first and second sections 450  451 of the ventilation circuit 45 and to the housing exterior 460.
[0016] As shown in FIGS. 1 and 2  the electrical machine 20 may include a ventilation system  components 202 and rotor 203 that generate heat with the rotor 203 being rotatable about an axis thereof. The ventilation system 201 pumps heated air away from the components 202 and into the first section 450 of the ventilation circuit 45 and drives cooled air from the second section 451 of the ventilation circuit 45 back toward the components 202. The main channel 46 may be disposed substantially in parallel with the rotor 203  with each of the plurality of tubes 50 being orthogonally oriented relative to the main channel 46 and the rotor 203.
[0017] The plurality of tubes 50 may include at least one first tube 60  at least one second tube 70  at least one third tube 80 and at least one fourth tube 90. The at least one first tube 60 extends through a first bisected portion 4501 of the at least one first section 450 of the ventilation circuit 45. The at least one second tube 70 extends through a second bisected portion 4502 of the at least one first section 450 of the ventilation circuit 45. The at least one third tube 80 extends through a first bisected portion 4511 of the at least one second section 451 of the ventilation circuit 45. The at least one fourth tube 90 extends through a second bisected portion 4512 of the at least one second section 451 of the ventilation circuit 45.
[0018] In accordance with aspects of the invention  the at least one first  second  third and fourth tubes 60  70  80  90 are substantially similar in shape and size. However  it is to be understood that in alternative embodiments one or more may have a unique shape and size as compared to one or more of the others. Each of the at least one first  second  third and fourth tube 60  70  80  90 may also have a substantially uniform geometry from end-to-end. However  it is again to be understood that in alternative embodiments one or more may have a varied geometry from end-to-end. Each of the at least one first  second  third and fourth tube 60  70  80  90 may also include a tube bundle 100. This tube bundle 100 may be arranged in an in-line or staggered formation. Also  the at least one first tube 60 and the at least one second tube 70 may each extend in substantially opposite directions on either side of the main channel 46 and may be substantially coaxial and parallel. Similarly  the at least one third tube 80 and the at least one fourth tube 90 may each extend in substantially opposite directions on either side of the main channel 46 and may be substantially parallel and coaxial.
[0019] With the construction described above  the housing 40 is formed with the main channel 46 and bisected portions of the ventilation circuit 45 on either side of the main channel. In operation and as shown in the exemplary embodiment of the FIG. 3  heated air may flow away from the electrical machine 20 along the first and second bisected portions 4501  4502 of the at least one first section 450 of the ventilation circuit 45 while cooling media flows from the main channel 46  into and through the at least one first and second tubes 60  70. Heat is therefore removed from the heated air by the cooling media across the respective thermally conductive surfaces of the at least one first and second tubes 60  70. The partially cooled air then flows around the at least one baffle 43 and back toward the electrical machine 20 along the first and second bisected portions 4511  4512 of the at least one second section 451 of the ventilation circuit 45. The cooling media flows from the main channel 46  into and through the at least one third and fourth tubes 80  90 whereby additional heat is removed from the partially cooled air by the cooling media across the respective thermally conductive surfaces of the at least one third and fourth tubes 80  90.
[0020] Since the cooling media travels through the ventilation circuit 45 by way of the at least one first  second  third and fourth tubes 60  70  80  90  a distance the cooling media must travel from the main channel 46 to the housing exterior 460 is reduced as compared to a width of the heat exchanger 30. As such  a pressure drop along the lengths of the at least one first  second  third and fourth tubes 60  70  80  90 is reduced or avoided and a temperature differential between the cooling media and the heated air along the lengths of the at least one first  second third and fourth tubes 60  70  80  90 is maintained. That is  the at least one first  second third and fourth tubes 60  70  80  90 may each have a length which is substantially equal to a length from the central walls 44 to the housing exterior 460. Since this length is substantially shorter than the width of the heat exchanger 30 and the ventilation circuit 45  a pressure and a temperature of the cooling media flowing through the at least one first  second third and fourth tubes 60  70  80  90 each have less opportunity to decrease and increase  respectively.
[0021] While the invention has been described in detail in connection with only a limited number of embodiments  it should be readily understood that the invention is not limited to such disclosed embodiments. Rather  the invention can be modified to incorporate any number of variations  alterations  substitutions or equivalent arrangements not heretofore described  but which are commensurate with the spirit and scope of the invention. Additionally  while various embodiments of the invention have been described  it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly  the invention is not to be seen as limited by the foregoing description  but is only limited by the scope of the appended claims.

WE CLAIM:
1. A heat exchanger (30)  comprising:
a housing (40) disposed proximate to a heat source (20)  the housing (40) having:
sidewalls (41) forming an enclosure 
a baffle (43) defining in the enclosure a ventilation circuit (45) thermally communicative with the heat source (20)  and
central walls (44) defining a main channel (46) bisecting the ventilation circuit (45) along which cooling media flows; and
a tube (60  70  80  90) extending through a bisected portion of the ventilation circuit (45) and fluidly coupled to the main channel (46) and a housing exterior (460) to direct the cooling media from the main channel (46)  through the bisected portion of the ventilation circuit (45) and to the housing exterior (460).
2. The heat exchanger (30) according to claim 1  wherein the tube (60  70  80  90) is plural in number and comprises:
at least one first tube (60) extending through a first bisected portion of the ventilation circuit; and
at least one second tube (70) extending through a second bisected portion of the ventilation circuit.
3. The heat exchanger (30) according to claim 2  wherein the at least one first and second tubes (60  70) each extend in substantially opposite directions.

4. The heat exchanger (30) according to claim 1  wherein the ventilation circuit (45) comprises:
at least one first section (450) along which heated air flows away from the heat source; and
at least one second section (451) along which cooled air flows toward the heat source.
5. The heat exchanger (30) according to claim 4  wherein the at least one first and second sections (450  451) are each bisected by the main channel (46).
6. The heat exchanger (30) according to claim 5  wherein the tube (60  70  80  90) is plural in number and comprises:
at least one first tube (60) extending through a first bisected portion (4501) of the at least one first section (450) of the ventilation circuit (45);
at least one second tube (70) extending through a second bisected portion (4502) of the at least one first section (450) of the ventilation circuit (45);
at least one third tube (80) extending through a first bisected portion (4511) of the at least one second section (451) of the ventilation circuit (45); and
at least one fourth tube (90) extending through a second bisected portion (4512) of the at least one second section (451) of the ventilation circuit (45).
7. The heat exchanger (30) according to claim 6  wherein the at least one first  second  third and fourth tubes (60  70  80  90) are substantially similar.
8. The heat exchanger (30) according to claim 6  wherein each of the at least one first  second  third and fourth tube (60  70  80  90) has a substantially uniform geometry.
9. The heat exchanger (30) according to claim 6  wherein each of the at least one first  second  third and fourth (60  70  80  90) tube comprises a tube bundle (100).
10. The heat exchanger (30) according to claim 6  wherein the at least one first tube (60) and the at least one second tube (70) each extend in substantially opposite directions and are substantially parallel  and
wherein the at least one third tube (80) and the at least one fourth tube (90) each extend in substantially opposite directions and are substantially parallel.