WO2005114083A1

WO2005114083A1 - Heat exchanger

Info

Publication number: WO2005114083A1
Application number: PCT/JP2005/009600
Authority: WO
Inventors: Shigeharu Ichiyanagi
Original assignee: Showa Denko K.K.
Priority date: 2004-05-20
Filing date: 2005-05-19
Publication date: 2005-12-01
Also published as: DE112005000505T5

Abstract

A heat exchanger 1 comprises an outer tube 2, an inner tube 3 disposed inside the outer tube 2 with a space provided the two tubes, fins 4 provided on the outer peripheral surface of the inner tube 3, and two connectors 5 fixed to the two tubes 2, 3 at respective opposite ends of each of the tubes. The space between the two tubes 2, 3 serves as a first fluid passageway 6, and the interior of the inner tube 3 provides a second fluid passageway 7. The inner tube 3 has opposite end portions projecting outward beyond the outer tube 2, and the fins 4 are removed from the entire portion of each of the outward projections 3a to provide a finless portion 8. Each of the connectors 5 is provided with a through bore 14 and a channel 13. The through bore 14 has one end opening formed in an outer surface of the connector 5 and another end opening causing the finless portion 8 of the inner tube 3 to be inserted into the bore 14 therethrough. The channel 13 has one end opening formed in an outer surface of the connector 5 and another end opening communicating with the first fluid passageway 6. The heat exchanger is reduced in the number of components and achieves an improved heat exchange efficiency.

Description

DESCRIPTION

HEAT EXCHANGER

CROSS REFERENCE TO RELATED APPLICATION This application is an application filed under 35 ϋ.S.C. §111 (a) claiming the benefit pursuant to 35 U.S.C. §119 (e) (1) of the filing date of Provisional Application No. 60/574,566, filed May 27, 2004 pursuant to 35 U.S.C. §111 (b) .

TECHNICAL FIELD The present invention relates to heat exchangers, more particularly to those suitable for use as intermediate heat exchangers in supercritical refrigeration cycles wherein a supercritical refrigerant such as C0₂ (carbon dioxide) is used. The invention relates also to heat exchangers suited for use in heating engine coolants for motor vehicles with a supercritical heating medium such as C0₂. The term ""aluminum" as used herein and in the appended claims includes aluminum alloys in addition to pure aluminum.

BACKGROUND ART Supercritical refrigeration cycles are known which comprise a compressor, gas cooler, evaporator, vapor-liquid separator, pressure reducer and intermediate heat exchanger for subjecting to heat exchange the refrigerant flowing out ofthe gas cooler andthe refrigerant flowingout of the evaporator, For use in such supercritical refrigeration cycles, an intermediate heat exchanger is known which comprises a heat exchange tube having an inner fluid bore and a plurality of outer fluid bores formed around and spaced from the inner fluid bore, two inner bore connectors fixed to respective opposite ends of the heat exchange tube and each having a channel ' communicating with the inner fluid bore, and two outer bore connectors fixed to the heat exchange tube, positioned inwardly of the inner bore connectors with respect to the longitudinal direction of the tube and each having a channel in communication with the outer fluid bores (see the publication of JP-A No. 2000-2492) . However, the intermediate heat exchanger disclosed in the publication requires four connectors in addition to a heat exchange tube and therefore has the problem of being greater in the number of components. The heat- exchanger has another problem in that the area of heat transfer between the fluid flowing through the inner bore and the fluid flowing through the outer bores is relatively small to result in an insufficient heat exchange efficiency. An object of the present invention is to overcome the above problems and to provide a heat exchanger which is reduced in the number of components and improved in heat exchange efficiency. DISCLOSURE OF THE INVENTION To fulfill the above obj ect, the present invention comprises the following modes. 1) A heat exchanger comprising an outer tube, an inner tube disposed inside the outer tube with a space provided the two tubes, fins provided between the outer tube and the inner tube, and two connectors fixed to the two tubes at respective opposite ends of each of the tubes, the space between the two tubes serving as a first fluid passageway, interior of the inner tube providing a second fluid passageway, the inner tube having opposite end portions projecting outward beyond the outer tube, each of the outward projections having at least an outer end portion providing a finless portion, each of the connectors being provided with a through bore and a channel, the through bore having one end opening formed in an outer surface of the connector and another end opening causing the finless portion of the inner tube to be inserted into the bore therethrough, the channel having one end opening formed in an outer surface of the connector and another end opening communicating with the first fluid passageway. 2) A heat exchanger according to par. 1) wherein the inner tube is inserted through the outer tube, and the fins are formed on an outer peripheral surface of the inner tube. 3) A heat exchanger according to par. 1) wherein the fins are formed on an outer peripheral surface of the inner tube integrally therewith and arranged at a spacing circumferentially of the inner tube so as to extend longitudinally of the inner tube. 4) A heat exchanger according to par. 1) wherein each of the connectors has an outer tube fitting cavity formed in an outer surface thereof, and the outer tube has an end fitted in the cavity and an outer periphery j oined to an inner peripheral edge of the connector defining an opening of the cavity. 5) A heat exchanger according to par .1) wherein the finless portion includes a portion of the inner tube positioned within the channel of the connector in addition to the portion of the inner tube inserted in the through bore. 6) A heat exchanger according to par . 1) wherein the entire outward projection of the inner tube is the finless portion. 7) A heat exchanger according to par. 1) wherein an outer periphery of the inner tube is joined to an inner peripheral edge portion of the connector defining said one end opening of the through bore. 8) A heat exchanger according to par .7) wherein the finless portion of the inner tube has an outer end portion projecting outward from the opening of the through bore in the connector outer surface, and the outer periphery of the inner tube is joined to an inner peripheral edge portion of the connector defining the through bore opening in the connector outer surface . 9) A heat exchanger according to par. 8) wherein a union screw is fitted over the portion of the inner tube projecting outward from the opening of the through bore in the connector outer surface and joined to the connector. 10) A heat exchanger according to par. 1) wherein the finless portion of the inner tube has an outer end positioned at an intermediate portion of the through bore of the connector, and a portion of the through bore closer to the connector outer surface than the finless portion outer end provides a channel communicating with the second fluid passageway. 11) A refrigeration cycle which comprises a compressor, a gas cooler, an evaporator, a vapor-liquid separator, a pressure reducer and an intermediate heat exchanger for subjecting to heat exchange a refrigerant flowing out of the gas cooler and a refrigerant flowing out of the evaporator and wherein a supercritical refrigerant is used, the intermediate heat exchanger comprising a heat exchanger according to any one of pars. 1) to 10) . 12) A refrigeration cycle according to par. 11) wherein the refrigerant flowing out of the evaporator and having low pressure is passed through the first fluid passageway of the intermediate heat exchanger, and the refrigerant flowing out of the gas cooler and having high pressure is passed through the second fluid passageway of the intermediate heat exchanger. 13) A vehicle having installed therein the refrigeration cycle according to par. 11) as an air conditioner. 14) A heating cycle comprising a compressor, an outdoor heat exchanger, a vapor-liquid separator, a pressure reducer, and a coolant heating heat exchanger for subjecting to heat exchange a supercritical heating medium compressed by the compressor and having a high temperature and high pressure and an engine coolant sent from an engine to a heater core, the coolant heating heat exchanger comprising a heat exchanger according to any one of pars. 1) to 10) . 15) A heating cycle according to par. 14) wherein the engine coolant is passed through the first fluid passageway of the coolant heating heat exchanger, and the supercritical heating medium compressed by the compressor is passed through the second fluid passageway of the coolant heating heat exchanger. 16) A vehicle having installed therein a heating cycle according to par. 14) as an air conditioner. The heat exchanger according to pars. 1) and 2) comprises an outer tube, an inner tube and two connectors and is therefore smaller in the number of components than the heat exchanger disclosed in the publication. The fins provided between the inner tube and the outer tube give an increased area of heat transfer between the fluids flowing through the first and second fluid passageways to achieve an improved heat exchange efficiency. The heat exchanger according to par. 3) has an increased area of heat transfer between the fluids flowing through the first and second fluid passageways and accordingly achieves, an improved heat exchange efficiency. Since the fins are formed on the inner tube integrally therewith, this construction results in a further reduction in the number of components. When the portion of the inner tube positioned within the connector channel is in the form of a finless portion as described in par. 5) , the fluid led through the channel flows uniformly into the portions between respective adjacent pairs of fins to achieve an improved heat exchange efficiency. With the heat exchanger according to par. 4), the fluid flowing through the first fluid passageway can be prevented from leaking. The heat exchanger according to pars. 5) and 6) offers reduced flow resistance to the fluid flowing in or out through the channel. If the inner tube has fins on the portion thereof positioned within the connector channel, the fluid flowing in or out through the channel encounters increased flow resistance, entailing a lower heat exchange efficiency. With the heat exchanger according to par. 7), the fluid flowing through the second fluid passageway can be prevented from leaking. With the heat exchanger according to par. 8), the inner tube outer periphery can be joined to the connector reliably with ease, and the fluid can be reliably prevented from leaking when flowing through the second fluid passageway. It is relatively difficult to join the inner tube outer periphery to the connector inside the connector. With the heat exchanger according to par. 9), the union screw is usable for connecting a pipe or the like of the piping system to the second pas.sageway portion.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary front view partly broken away and showing the overall construction of Embodiment 1 of heat exchanger of the invention. FIG. 2 is an enlarged fragmentary view of FIG. 1. FIG. 3 is an enlarged view in section taken along the line A-A in FIG. 2. FIG. 4 is an enlarged view in section taken along the line B-B in FIG.2. FIG. 5 is a diagram showing a supercritical refrigeration cycle having an intermediate heat exchanger which is the heat exchanger of Embodiment 1. FIG. 6 is a view corresponding to FIG. 2 and showing Embodiment 2 of heat exchanger of the invention. FIG. 7 is a view corresponding to FIG. 2 and showing Embodiment 3 of heat exchanger of the invention.

BEST MODE OF CARRYING OUT THE INVENTION Embodiments of the invention will be described below with reference to the drawings. In the following description, the upper and lower sides and left- and' right-hand sides of FIGS.

1, 2, 6 and 7 will be referred to as "upper," "lower," "left" and "right," respectively. Throughout the drawings, like parts will be designated by like reference numerals and will not be described repeatedly. Embodiment 1 This embodiment is shown in FIGS. 1 to 5. FIG. 1 shows the overall construction of a heat exchanger of the invention, and FIGS. 2 to 4 show the constructions of main parts of the exchanger. FIG. 5 shows a supercritical refrigeration cycle wherein the heat exchanger of FIG. 1 is used as an intermediate heat exchanger. FIGS. 1 to 4 show a heat exchanger 1 comprising an outer tube 2, an inner tube 3 inserted through the outer tube 2 concentrically therewith and spaced apart therefrom, fins 4 provided on the outer peripheral surface of the inner tube 3, and two connectors 5 fixed to the two tubes 2, 3 at respective opposite ends thereof. The interior of the outer tube 2 around the inner tube 3 provides a first fluid passageway 6, and the interior of the inner tube 3 a second fluid passageway 7. The outer tube 2 is made of a metal, i.e., an aluminum extrudate according to the embodiment. The inner tube 3, which is made of a metal, i.e., an aluminum extrudate in this embodiment, has a plurality of fins 4 arranged at a spacing circumferentially thereof and formed on the outer peripheral surface of the inner tube 3 integrally therewith so as to extend longitudinally thereof. There is a small clearance between the outer end of each fin 4 and the inner peripheral surface of the outer tube 2 (see FIG.3) . The inner tube 3 has opposite end portions projecting outward beyond the outer tube 2. The fins 4 are removed from these entire outward projections 3a to provide finless portions 8. The inner tube 3 has a plurality of inner fins 9 formed on the inner peripheral surface of the tube 3 integrally therewith, arranged at a spacing circumferentially thereof and extending over the entire length thereof (see FIGS. 3 and 4) . Each of the connectors 5 is in the form of a block of metal, i.e., of aluminum, and comprises a lateral solid cylindrical portion 5a and a rectangular parallelepipedal portion 5b integral with the upper end of the cylindrical portion 5a. The left connector 5 will be described below. The solid cylindrical portion 5a of the connector 5 has an annular wall 11 formed integrally with the right end wall thereof and projecting rightward, whereby an outer tube fitting cavity 12 is formed for one end of the outer tube 2 to fit in. The end of the outer tube 2 is fitted into the cavity 12 of the connector 5. The outer end of the annular wall 11, i.e., the peripheral edge of the wall 11 defining the opening of the cavity 12, is joined to the outer periphery of the outer tube 2 by brazing, i.e., by torch brazing in this case. The connector 5 is provided with a channel 13 having one open end formed in the area of the right endwall of the cylindrical portion 5a surrounded by the annular wall 11 and another open end formed in the top wall of the rectangular parallelepipedal portion 5b. The channel 13 communicates with the first fluid passageway 6. A through bore 14 extends from the inner wall of the cylindrical portion 5a defining the left end of the lateral portion of the connector channel 13 to the left end face (outer surface) of the cylindrical portion 5a. The leftward part of the finless portion 8 of the inner tube 3 is inserted through the bore 14. The finless portion 8 has a left end projecting outward from the opening of the through bore 14 in the left end face of the cylindrical portion 5a. The outer periphery of the finless portion 8 of the inner tube 3 is joined to the edge of left end face of the cylindrical portion 5a which edge defines the through bore 14 by brazing, i.e., by torch brazing. An annular wall 15 proj ecting leftward is formed integrally with the left end face of the connector cylindrical portion 5a around the through bore 14. The left end of the finless portion 8 of the inner tube 3 projects leftward beyond the annular wall 15. A union screw 16 is provided around and covers the annular wall 15 and the left end projection of the finless portion 8 projecting outward beyond the annular wall 15. The union screw 16 has a bore 17 extending therethrough and having a large-diameter portion 17a at its right end and a small-diameter portion 17b communicating with the portion 17a. The annular wall 15 is fitted in the large-diameter portion 17a, andthe left endofthe finless portion 8 inthe small-diameter portion 17b. The union screw 16 has a right end fitting in an annular recessed part 18 formed in the left end face of the cylindrical portion 5a around the annular wall 15. The right end of outer peripheral surface of the union screw 16 is joined to the inner periphery of the recessed part 18 of the cylindrical portion 5a by brazing, i.e., torch brazing. The union screw 16 of one of the connectors 5 is used for connecting a pipe of a piping system for supplying a fluid to the second fluid passageway 7, and the union screw 16 of the other connector 5 for connecting another pipe of the piping system for discharging the fluid fromthe second fluid passageway 7. Each connector 5 has a threaded bore 19 extending downward from the top wall of the rectangular parallelepipedal portion 5b. The threaded bore 19 of one of the connectors 5 is used for connecting another pipe of the piping system for supplying a fluid to the first fluid passageway 6, and the threaded bore 19 of the other connector 5 for connecting another pipe of the piping system for discharging the fluid from the first fluid passageway 6. The right connector 5 is reverse to the left connector 5 in construction with respect to the left-right direction, and is secured to the outer tube 2 and the inner tube 3 in the same manner as the left connector 5. FIG. 5 shows a supercritical refrigeration cycle wherein the heat exchanger 1 described is used as an intermediate heat exchanger. With reference to FIG. 5, the supercritical refrigeration cycle, wherein C0₂ is used as a supercritical refrigerant, comprises a compressor 21, gas cooler 22, evaporator 23, accumulator 24 serving as a vapor-gas separator, expansion valve 25 serving as a pressure reducer and intermediate heat exchanger 1 for subjecting to heat exchange the refrigerant flowing out of the gas cooler 22 and the refrigerant flowing out of the evaporator 23. The cycle is installed in vehicles, for example, in motor vehicles, as an air conditioner. The intermediate heat exchanger 1 is adapted to pass the refrigerant having low pressure and flowing out of the evaporator 23 through the first fluid passageway 6, and the refrigerant of high pressure flowing out of the gas cooler 22 through the second fluid passageway 7. The supercritical refrigerant to be used is carbon dioxide in the present case but is not limited thereto; also usable are ethylene, ethane, nitrogen oxide, etc. Embodiment 2 This embodiment is shown in FIG. 6. The embodiment, i.e., a heat exchanger 30. has a through bore 31 extending through the left connector 5 and having an end opening in the inner wall of the cylindrical portion 5a defining the left end of the lateral portion, formed in the portion 5a, of the channel 13 and another end opening in the left end face of the cylindrical portion 5a . The finless portion 8 of the inner tube 3 has a left end positioned at an intermediate portion of the length of the connector through bore 31. The bore 31 has a large-diameter portion 31b on the left side of the bore portion having the finless portion 8 inserted therein, with a small-diameter portion 31a formed between this bore portion and the portion 31b. The small-diameter portion 31a and the large-diameter portion 31b provide a channel communicating with the second fluid passageway 7. The outer periphery of the inner tube 3 is joined to the peripheral edge of the inner wall of the cylindrical portion 5a defining the right-end opening of the connector through bore 31 bybrazing, i.e., preplaced brazing. The connector 5 has a threaded bore 32 formed at the junction of the solid cylindrical portion 5a and the rectangular parallelepipedal portion 5b and extending rightward from the left end face of the junction. The large-diameter portion 31b and the threaded bore 32 of one of the connectors 5 are used for connecting a pipe of a piping system for supplying a fluid to the first fluid passageway 6, and the large-diameter portion 31b and the threaded bore 32 of the other connector 5 for connecting another pipe of the piping system for discharging the fluid from the first fluid passageway 6. Incidentally, neither of the annular wall and the recessed part indicated respectively at 15 and 18 in Embodiment 1 are formed in the connectors 5. The right connector 5 is reverse to the left connector 5 in construction with respect to the left-right direction, and is secured to the outer tube 2 and the inner tube 3 in the same manner as the left connector 5. With the exception of the above features, the heat exchanger 30 has the same construction as the heat exchanger 1 of Embodiment 1 and is used as an intermediate heat exchanger in supercritical refrigeration cycles like Embodiment 1. Embodiment 3 This embodiment is shown in FIG. 7. The embodiment, i.e., a heat exchanger 40. has a through bore 41 provided in the left connector 5 and having an end opening in the inner wall of the cylindrical portion 5a defining the left end of the lateral portion, formed in the portion 5a, of the channel 13 and another end opening formed in the top face of the rectangular parallelepipedal portion 5b and positioned on the left side of the threaded bore 19. The finless portion 8 of the inner tube 3 has a left end positioned at an intermediate portion of length of a lateral portion 41a of the through bore 41 which portion 41a extends in the left-right direction. The part of the bore lateral portion 41a on the _r left side of the left end of the finless portion 8, and a vertical portion 41b of the through bore 41 provide a channel communicating with the second fluid passageway 7. The bore vertical portion 41b has an upper end portion providing a large-diameter portion 41c. The large-diameter portion 41c of one of the connectors 5 is used for connecting a pipe of a piping system for supplying a fluid to the first fluid passageway 6, and the large-diameter portion 41c of the other connector 5 for connecting another pipe of the piping system for discharging the fluid from the first fluid passageway 6. Incidentally, neither of the annular wall and the recessed part indicated respectively at 15 and 18 in Embodiment 1 are formed in the connectors 5. The right connector 5 is reverse to the left connector 5 in construction with respect to the left-right direction, and is secured to the outer tube 2 and the inner tube 3 in the same manner as the left connector 5. With the exception of the above features, the heat exchanger 40 has the same construction as the heat exchanger 1 of Embodiment 1, and is suited for use as an intermediate heat exchanger in supercritical refrigeration cycles as is the case Embodiment 1. The heat exchangers of Embodiments 1 to 3, which are useful for supercritical refrigeration cycles as described above, are usable also in heating cycles as will be described below. Heating cycles comprise a compressor, outdoor heat exchanger, vapor-liquid separator, pressure reducer, and coolant heating heat exchanger for subjecting to heat exchange a supercritical heating medium having a high temperature and compressed by the compressor and an engine coolant sent from an engine to a heater core. The heat exchangers of Embodiments 1 to 3 are used as the coolant heating heat exchanger. In the heating cycle, the engine coolant is passed through the first fluid passageway 6 of the coolant heating heat exchanger, and the supercritical refrigerant compressedbythe compressor is passed through the second fluid passageway 7 of the exchanger. The compressor, the accumulator 24 serving as a vapor-liquid separator, and the expansion valve 25 serving as a pressure reducer of the supercritical refrigeration cycle shown in FIG. 5 may be used in common for the heating cycle as the compressor, vapor-liquid separator and pressure reducer thereof, along with the gas cooler 22 for use as the outdoor heat exchanger. The piping system and change-over valves, etc. may be provided for this purpose.

INDUSTRIAL APPLICABILITY The heat exchanger of the invention is suited for use in supercritical refrigeration cycles wherein a supercritical refrigerant, such as C0₂ (carbon dioxide) , is used to serve as an intermediate heat exchanger.

Claims

CLAIMS 1. A heat exchanger comprising an outer tube, an inner tube disposed inside the outer tube with a space provided the two tubes, fins provided between the outer tube and the inner tube, and two connectors fixed to.the two tubes at respective opposite ends of each of the tubes, the space between the two tubes serving as a first fluid passageway, interior of the inner tube providing a second fluid passageway, the inner tube having opposite end portions projecting outward beyond the outer tube, each of. the outward projections having at least an outer end portion providing a finless portion, each of the connectors being provided with a through bore and a channel, the through bore having one end opening formed in an outer surface of the connector and another end opening causing the finless portion of the inner tube to be inserted into the bore therethrough, the channel having one end opening formed in an outer surface of the connector and another end opening communicating with the first fluid passageway. 2. A heat exchanger according to claim 1 wherein the inner tube is inserted through the outer tube, and the fins are formed on an outer peripheral surface of the inner tube. 3. A heat exchanger according to claim 1 wherein the fins are formed on an outer peripheral surface of the inner tube integrally therewith and arranged at a spacing circumferentially of the inner tube so as to extend longitudinally of the inner tube. 4. A heat exchanger according to claim 1 wherein each of the connectors has an outer tube fitting cavity formed in an outer surface thereof, and the outer tube has an end fitted in the cavity and an outer periphery j oined to an inner peripheral edge of the connector defining an opening of the cavity. 5. A heat exchanger according to claim 1 wherein the finless portion includes a portion of the inner tube positioned within the channel of the connector in addition to the portion of the inner tube inserted in the through bore. 6. A heat exchanger according to claim 1 wherein the entire outward projection of the inner tube is the finless portion. 7. A heat exchanger according to claim 1 wherein an outer periphery of the inner tube is joined to an inner peripheral edge portion of the connector defining said one end opening of the through bore. 8. A heat exchanger according to claim 7 wherein the finless portion of the inner tube has an outer end portion projecting outward from the opening of the through bore in the connector outer surface, and the outer periphery of the inner tube is joined to an inner peripheral edge portion of the connector defining the through bore opening in the connector outer surface. 9. A heat exchanger according to claim 8 wherein a union screw is fitted over the portion of the inner tube projecting outward from the opening of the through bore in the connector outer surface and joined to the connector. 10. A heat exchanger according to claim 1 wherein the finless portion of the inner tube has an outer end positioned at an intermediate portion of the through bore of the connector, and a portion of the through bore closer to the connector outer surface than the finless portion outer end provides a channel communicating with the second fluid passageway. 11. A refrigeration cycle which comprises a compressor, a gas cooler, an evaporator, a vapor-liquid separator, a pressure reducer and an intermediate heat exchanger for subjecting to heat exchange a refrigerant flowing out of the gas cooler and a refrigerant flowing out of .the evaporator and wherein a supercritical refrigerant is used, the intermediate heat exchanger comprising a heat exchanger according to any one of claims 1 to 10. 12. A refrigeration cycle according to claim 11 wherein the refrigerant flowing out of the evaporator and having low pressure is passed through the first fluid passageway of the intermediate heat exchanger, and the refrigerant flowing out of the gas cooler and having high pressure is passed through the second fluid passageway of the intermediate heat exchanger. 13. A vehicle having installed therein the refrigeration cycle according to claim 11 as an air conditioner. 14. A heating cycle comprising a compressor, an outdoor heat exchanger, a vapor-liquid separator, a pressure reducer, and a coolant heating heat exchanger for subjecting to heat exchange a supercritical heating medium compressed by the compressor and having a high temperature and high pressure and an engine coolant sent from an engine to a heater core,

' the coolant heating heat exchanger comprising a heat exchanger according to any one of claims 1 to 10. 15. A heating cycle according to claim 14 wherein the engine coolant is passed through the first fluid passageway of the coolant heating heat exchanger, and the supercritical heating medium compressed by the compressor is passed through the second fluid passageway of the coolant heating heat exchanger. 16. A vehicle having installed therein a heating cycle according to claim 14 as an air conditioner.