[0001] Reference is made to and this application claims priority from and the benefit of U.S. Provisional Application Serial No. 61/166,433, filed April 3, 2009, entitled "MULTI-CIRCUIT HEAT EXCHANGER" and U.S. Provisional Application Serial No.: 61/168,341, filed April 10, 2009, entitled "MULTICIRCUIT HEAT EXCHANGER", which applications are incorporated herein in their entirety by reference.

Field of the Invention

[0002] This invention relates generally to refrigerant vapor compression systems and, more particularly, to a parallel flow, multi-circuit tube heat exchanger for use in multiple circuit refrigerant vapor compression system, and more specifically to a parallel flow, multi-circuit tube heat exchanger adapted to prevent cross-contamination between the circuits within the heat exchanger.

Background of the Invention

[0003] Refrigerant vapor compression systems are well known in the art.

Air conditioners and heat pumps employing refrigerant vapor compression cycles are commonly used for cooling or cooling/heating air supplied to a climate controlled comfort zone within a residence, office building, hospital, school, restaurant or other facility. Refrigerant vapor compression systems are also commonly used for cooling air, or other secondary media such as water or glycol solution, to provide a refrigerated environment for food items and beverage products with display cases, bottle coolers or other similar equipment in supermarkets, convenience stores, groceries, cafeterias, restaurants and other food service establishments.

[0004] These systems normally constitute a refrigerant circuit including a compressor, a condenser, an expansion device, and an evaporator connected by refrigerant lines in a closed refrigerant circuit in refrigerant flow communication and arranged in accord with the refrigerant vapor compression cycle being employed. The expansion device, commonly an expansion valve or a fixed-bore metering device, such as an orifice or a capillary tube, is disposed in the refrigerant circuit upstream, with respect to refrigerant flow, of the evaporator and downstream of the condenser. The expansion device operates to expand the liquid refrigerant passing through the refrigerant line, connecting the condenser to the evaporator, to a lower pressure and temperature. The refrigerant vapor compression system may be charged with any of a variety of refrigerants, including, for example, R-12, R- 22, R- 134a, R-404A, R-410A, R-407C, R717, R744 or other compressible fluid. [0005] In operation, a fan associated with the condenser, which is typically located exteriorly of the climate-controlled space, passes ambient temperature air from the outside environment through the condenser in heat exchange relationship with hot refrigerant vapor discharged from the compressor. As the ambient air passes in heat exchange relationship with the hot refrigerant vapor, the refrigerant vapor is cooled and condensed to liquid and the ambient air is heated and discharged back into the atmosphere. A fan associated with an evaporator circulates air to be conditioned from a climate controlled environment and passes that indoor air, often mixed with an outside fresh air in various proportions, through the evaporator. As the air flows over evaporator, the air interacts, in a heat exchange relationship, with refrigerant passing through the heat exchanger, typically, inside tubes or channels. As a result, in the cooling mode of operation, the air is cooled, and generally dehumidified.

[0006] It is a common practice for air conditioning systems for providing conditioned air to large spaces, such as in office buildings, hospitals, schools, restaurants or other commercial establishments, to include multiple, independent refrigerant circuits, rather the a single refrigerant circuit, to provide sufficient capacity to meet the required cooling demands and/or serve independent zones within the climate-controlled space. In some multiple circuit refrigerant vapor compression systems, the heat exchanger forming the condenser is a multiple circuit heat exchanger having a plurality of refrigerant tubes extending in parallel relationship between a first manifold and a second manifold. For example, in a dual circuit refrigeration system, in the parallel flow heat exchanger, at least one of the manifolds is subdivided by a baffle into a first chamber and a second chamber. A first set of the plurality of the parallel refrigerant tubes is connected in fluid communication between the respective first sections of the first and second manifolds which are connected in a first refrigerant circuit of the refrigeration system. A second set of the plurality of the parallel refrigerant tubes is connected in fluid communication between the respective second sections of the first and second manifolds which are connected in a second refrigerant circuit of the refrigeration system.

[0007] The division baffle constitutes a flow impervious member and is disposed within the interior volume defined within the manifold to extend across the cross-section of the internal volume to prevent refrigerant flowing between the first and second chambers disposed on opposite sides of the baffle. Flow of refrigerant from one of the first and second chambers into the other thereof is undesirable. If refrigerant were to flow between the first and second chambers, for example through a leak in the baffle, cross-contamination of the independent refrigerant circuits would occur as refrigerant and oil passing from one refrigerant circuit into the other, which would cause a loss of performance, loss of lubricating oil and potential damage to one or both of the compressors.

Summary of the Invention

[0008] In an aspect of the invention, a method is provided for preventing fluid cross-contamination between independent heat exchange circuits in a multicircuit heat exchanger having a common manifold defining an interior volume having a first chamber associated with a first heat exchange circuit and a second chamber associated with a second heat exchange circuit. The method comprises the steps of: establishing a void space within the interior volume of the common manifold between the first chamber therein and the second chamber therein; and providing a vent passage between the void space and a region exterior of the common manifold.

[0009] In an aspect of the invention, a multi-circuit heat exchanger is provided having protection against cross-contamination from fluid leaking from between independent heat exchange circuits sharing a common manifold. In an embodiment of the invention, the multi-circuit heat exchanger includes first and second spaced apart and longitudinally extending manifolds, a plurality of heat exchange tubes arrayed in parallel relationship and extending traversely between the first manifold and the second manifold, and a baffle assembly disposed within one of the first and second manifolds. Each heat exchange tube defines at least one fluid flow passage between the first manifold and the second manifold. A first set of the plurality of heat exchange tubes defines a first heat exchange circuit and a second set of the plurality of heat exchange tubes defines a second heat exchange circuit. The baffle assembly is disposed within at least one of the first and second manifolds for dividing the interior volume of that manifold into a first chamber and a second chamber. The baffle assembly includes a first flow impervious member and a second flow impervious member. Each baffle member extends generally transversely across the interior volume of that manifold. The first baffle member and the second baffle member are disposed in spaced apart relationship thereby forming a void space within the interior volume of the manifold between the first baffle member and the second baffle member. The void space is in fluid communication with a region exterior of that manifold whereby any fluid leaking from either chamber into the void space will be vented therefrom.

[0010] In an aspect of the invention, a method is provided for safeguarding a refrigeration system having multiple independent refrigerant circuits having a multicircuit heat exchanger in common, including a first refrigerant circuit having a first compressor for circulating refrigerant through a first heat exchange circuit of the heat exchanger and a second refrigerant circuit having a second compressor for circulating refrigerant through a second heat exchange circuit of the heat exchanger, the heat exchanger having a common manifold defining an interior volume having a first chamber associated with the first heat exchange circuit and a second chamber associated with the second heat exchange circuit. The method includes the steps of: establishing a void space within the interior volume of the common manifold between the first chamber therein and the second chamber therein; venting refrigerant that may leak from the first chamber or the second chamber into the void space to a region exterior of the common manifold; sensing a refrigerant pressure within each of the first refrigerant circuit and the second refrigerant circuit; terminating operation of the first compressor in the event the sensed refrigerant pressure in the first refrigerant circuit drops below a specified low pressure limit; and terminating operation of the second compressor in the event the sensed refrigerant pressure in the second refrigerant circuit drops below a specified low pressure limit.

Brief Description of the Drawings

[0011] For a further understanding of the disclosure, reference will be made to the following detailed description which is to be read in connection with the accompanying drawing, where:

[0012] FIG. 1 is a schematic diagram illustrating an exemplary embodiment of a multiple circuit, refrigerant vapor compression system incorporating a multicircuit parallel flow heat exchanger;

[0013] FIG. 2 is a side elevation view, partly in section, illustrating an exemplary embodiment of a multi-circuit parallel tube heat exchanger in accordance with the invention;

[0014] FIG. 3 is a side elevation view, in section, showing the baffle assembly disposed within the manifold as in the heat exchanger of FIG. 2; and [0015] FIG. 4 is a side elevation, view, in section, showing the connection of a heat exchange tube with a manifold as in the heat exchanger of FIG. 2; and [0016] FIG. 5 is a side elevation view, partly in section, illustrating another exemplary embodiment of a multi-circuit parallel tube heat exchanger in accordance with the invention.

Detailed Description

[0017] Referring initially to FIG. 1 of the drawings, there is depicted exemplary embodiments of a multiple circuit refrigerant vapor compression system 10 including two separate refrigerant circuits 20, 30, each of which operates independently of the other under the direction of a system controller (not shown) for conditioning air within separate zones of a climate-controlled space. The refrigerant vapor compression system 10 includes a dual-circuit heat exchanger 40 having a first heat exchange circuit 42 that is interdisposed in the first refrigerant circuit 20 and a second heat exchange circuit 44 that is interdisposed in the second refrigerant circuit 30. The first refrigerant circuit 20 further includes a refrigerant vapor compressor 22, an expansion device 24 and an evaporator 26 connected, together with the first heat exchange circuit 42 of the heat exchanger 40, in a closed loop refrigerant circuit by refrigerant lines 21, 23 and 25. The second refrigerant circuit 30 further includes a refrigerant vapor compressor 32, an expansion device 34 and an evaporator 36 connected, together with the second heat exchange circuit 44 of the heat exchanger 40, in a closed loop refrigerant circuit by refrigerant lines 31 , 33 and 35. Although the first and second refrigerant circuits 20, 30 are illustrated in FIG. 1 are each configured as a simplified air conditioning cycle, it is to be understood that the multi-circuit heat exchanger described herein may be employed in refrigerant vapor compression systems of various designs, including, without limitation, heat pump cycles, economized refrigerant cycles, and many other cycles including various options and features, as well in applications other than air conditioning, including for example, but not limited to refrigeration applications and the chilling of water or other fluids.

[0018] The first and second refrigerant circuits 20, 30 incorporate separate, independent heat exchange circuits 42, 44, respectively, and operate independently of each other. In operation of the first refrigerant circuit 20, the compressor 22 discharges hot, high pressure refrigerant vapor through discharge refrigerant line 21 into and thence through the first heat exchange circuit 42 of the heat exchanger 40 wherein the hot refrigerant vapor is desuperheated, condensed to a liquid and typically subcooled as it passes in heat exchange relationship with a cooling fluid, typically ambient air from externally of the climate-controlled space, which is passed by a condenser fan 46 operatively associated with the first heat exchanger circuit 42, over the refrigerant conveying heat exchange tubes of the first heat exchanger circuit 42. Similarly, in operation of the second refrigerant circuit 30, the compressor 32 discharges hot, high pressure refrigerant vapor through discharge refrigerant line 31 into and thence through the second heat exchange circuit 44 of the heat exchanger 40 wherein the hot refrigerant vapor is desuperheated, condensed to a liquid and typically subcooled as it passes in heat exchange relationship with a cooling fluid, typically ambient air from externally of the climate-controlled space, which is passed by a condenser fan 48 operatively associated with the second heat exchanger circuit 44, over the refrigerant conveying heat exchange tubes of the second heat exchanger circuit 44.

[0019] The high pressure, liquid refrigerant leaving the first heat exchanger circuit 42 of the heat exchanger 40 passes through refrigerant line 23 to the evaporator heat exchanger 26, traversing the expansion device 24 wherein the refrigerant is expanded to a lower pressure and temperature to form a refrigerant liquid/vapor mixture. The lower pressure and lower temperature, expanded refrigerant thence passes through the heat exchanger tubes of the evaporator heat exchanger 26 wherein the refrigerant is evaporated and typically superheated as it passes in heat exchange relationship with air to be cooled (and, in many cases, dehumidified), which is passed over the heat exchange tubes of the evaporator heat exchanger 26 by an evaporator fan 28 operatively associated therewith. The refrigerant leaving the evaporator heat exchanger 26 passes therefrom through suction refrigerant line 25 to return to the compressor 22 through the suction port thereto.

[0020] The high pressure, liquid refrigerant leaving the second heat exchanger circuit 44 of the heat exchanger 40 passes through refrigerant line 33 to the evaporator heat exchanger 36, traversing the expansion device 34 wherein the refrigerant is expanded to a lower pressure and temperature to form a refrigerant liquid/vapor mixture. The lower pressure and lower temperature, expanded refrigerant thence passes through the heat exchanger tubes of the evaporator heat exchanger 36 wherein the refrigerant is evaporated and typically superheated as it passes in heat exchange relationship with air to be cooled (and, in many cases, dehumidified), which is passed over the heat exchange tubes of the evaporator heat exchanger 36 by an evaporator fan 38 operatively associated therewith. The refrigerant leaving the evaporator heat exchanger 36 passes therefrom through suction refrigerant line 35 to return to the compressor 32 through the suction port thereto.

[0021] The multi-circuit, parallel flow heat exchanger 40 will be described herein in general with reference to the illustrative embodiment of the dual circuit parallel flow heat exchanger depicted in FIGs. 2-4. It is to be understood, however, that the multi-circuit heat exchanger 40 may include more than two heat exchange circuits. As depicted in FIG. 2, the heat exchanger 40 includes a plurality of heat exchange tubes 70 arranged in a generally vertical array, each of which extends in a horizontal direction along its longitudinal axis between a generally vertically disposed, longitudinally extending first manifold 50 and a generally vertically disposed, longitudinally extending second manifold 60, thereby providing a plurality of refrigerant flow paths between the two manifolds. Each manifold constitutes an axially elongated, closed-end vessel defining an interior volume in which refrigerant collects. Although the first and second manifolds 50, 60, as depicted in FIGs. 2-4, have a cylindrical configuration, the first and second manifolds 50, 60 may have a rectangular cross-section, a half-cylinder cross-section, or any other cross-sectional shape.

[0022] Each heat exchange tube 70 has a first end connected in fluid communication to the first manifold 50, a second end connected in fluid communication to the second manifold 60. In the depicted exemplary embodiment, as best seen in FIG. 4, each of the heat exchange tubes 70 has a generally flattened cross-section, for example, a rectangular cross-section or oval cross-section, and defines an interior subdivided into a side-by-side array of independent flow channels 72. The plurality of parallel flow channels 72 extend longitudinally, i.e. along the generally horizontally disposed longitudinal axis of the tube, the entire length of the tube, whereby the each of the individual flow channels 72 provides a flow path in refrigerant flow communication between the first manifold 50 and the second manifold 60. The multi-channel tubes 70, also known as micro-channel or mini- channel tubes, are shown in FIG. 4, for ease and clarity of illustration, as having twelve channels 72 defining flow paths having a generally rectangular cross-section. However, it is to be understood that in application, each multi-channel tube 70 may have any desired number of flow channels 72 and may have a circular, rectangular, triangular, oval or trapezoidal cross-section, or any other desired non-circular cross- section. It is also to be understood that the heat exchange tubes 70 of the multicircuit heat exchanger 40 may be conventional round tubes, each tube defining a single flow passage, rather than flattened, multi-channel tubes. [0023] To improve heat transfer between the air flowing over the external surface of the heat exchange tubes 70 and the refrigerant flowing through the parallel flow channels 72 of the heat exchange tubes 70, the heat exchanger 40 may include a plurality of external heat transfer fins 75 extending between selected sets of the parallel- arrayed tubes 70. The fins may be brazed or otherwise securely attached to the external surfaces of the neighboring heat exchange tubes 70 to establish heat transfer contact, by heat conduction, between the fins 75 and the external surface of the heat exchange tubes 70. In the exemplary embodiment of the heat exchanger 40 depicted in FIG. 2, the fins 75 constitute a generally saw-tooth configuration, elongated ribbon- like plate disposed between the heat exchange tubes 70. However, it is to be understood that other fin configurations, such as, for example, generally corrugated serpentine wavy, offset or louvered fins forming triangular, rectangular, or trapezoidal airflow passages, or generally vertical plates may be used in the disclosed parallel flow heat exchanger.

[0024] In the exemplary embodiment depicted in FIG. 2, the interior volume of the first manifold 50 is divided into a first chamber and a second chamber; the first chamber further subdivided into a first inlet chamber 51 and a first outlet chamber 53 by a flow impervious wall 52, and the second chamber further subdivided into a second inlet chamber 55 and a second outlet chamber 57 by a flow impervious wall 56. The second manifold is divided into a first chamber 61 and a second chamber 63 by a flow impervious wall 62.

[0025] A first plurality of the heat exchange tubes 70 arrayed in parallel relationship extend generally horizontally between the first inlet chamber 51 of the first manifold 50 and the first chamber 61 of the second manifold 60 and a second plurality of heat exchange tubes 70, also arrayed in parallel relationship, extend generally horizontally between the first chamber 61 of the second manifold 60 and the first outlet chamber 53 of the first manifold 50. The first inlet chamber 51, the first plurality of the heat exchange tubes 70, the first chamber 61 of the second manifold 60, the second plurality of the heat exchange tubes 70 and the first outlet chamber 53 of the first manifold 50 in serial flow arrangement form the first heat exchange circuit 42.

[0026] A third plurality of the heat exchange tubes 70 arrayed in parallel relationship extend generally horizontally between the second inlet chamber 55 of the first manifold 50 and the second chamber 63 of the second manifold 60 and a fourth plurality of the heat exchange tubes 70, also arrayed in parallel relationship, extend generally horizontally between the second chamber 63 of the second manifold and the second outlet chamber 57 of the first manifold 50. The second inlet chamber 55, the third plurality of the heat exchange tubes 70, the second chamber 63 of the second manifold 60, the second plurality of the heat exchange tubes 70, and the second outlet chamber 57 of the first manifold 50 in serial flow arrangement form the second heat exchange circuit 44.

[0027] Referring now to FIGs. 2 and 3 in particular, a baffle assembly 54 disposed within the interior volume of the first manifold 50 divides the interior volume of the first manifold 50 into the first chamber and the second chamber of the first manifold. The baffle assembly 54 includes a first flow impervious member 54A and a second flow impervious member 54B. Each baffle member 54A, 54B extends generally transversely across the interior volume of the first manifold 50. The first baffle member 54A and the second baffle member 54B are disposed in spaced apart relationship so as to a void space 80 within the interior volume of the first manifold 50 between the first baffle member 54A and the second baffle member 54B. A vent port 90 opens through a section of the wall of first manifold 50 that extends between the first baffle member 54A and the second baffle member 54B. The vent port 90 establishes an open flow path between the void space 80 and a region exterior of the first manifold 50 whereby any refrigerant that may leak into the void space 80 from either the first chamber or the second chamber of the first manifold 50 through a fissure or crack or other hole in one of the first baffle member 54A or the second baffle member 54B is vented directly to the atmosphere exterior of the first manifold 50.

[0028] In the refrigeration system 10, the first heat exchange circuit 42 of the heat exchanger 40 is incorporated as a refrigerant heat rejection heat exchanger in the first refrigerant circuit 20 with hot, high pressure refrigerant vapor discharging from the compressor 22 being delivered via refrigerant line 21 to the first inlet chamber 51 of the first manifold 50 through inlet port 41 and cooled, high pressure refrigerant liquid passing from first outlet chamber 53 of the first manifold 50 through outlet port 47 into refrigerant line 23 of the first refrigerant circuit. The second heat exchange circuit 44 of the heat exchanger 40 is incorporated as a refrigerant heat rejection heat exchanger in the second refrigerant circuit 30 with hot, high pressure refrigerant vapor discharging from the compressor 32 being delivered via refrigerant line 31 to the second inlet chamber 55 of the first manifold 50 through inlet port 43 and cooled, high pressure refrigerant liquid passing from the second outlet chamber 57 of the first manifold 50 through outlet port 49 into refrigerant line 33 of the first refrigerant circuit. In the event that either one of the baffle members 54A or 54B develops a crack or other fissure, any high pressure refrigerant that leaks therethrough from either the first inlet chamber 51 or the second outlet chamber 57 into the void space 80 will vent through the vent port 90 directly to the atmosphere external of the first manifold 50. [0029] As a result of the venting of the leaking refrigerant from the void space to a region exterior of the first manifold 50, the leaking refrigerant does not leak into and contaminate the refrigerant in the other refrigerant circuit. Additionally, the refrigerant pressure within the refrigerant circuit from which the refrigerant is leaking drops steadily. A pressure switch 92 is provided in operative association with each of the refrigerant circuits 42 and 44 to monitor the refrigerant pressure in refrigerant lines 23 and 33, respectively. In the event that the refrigerant pressure in either refrigerant circuit drops below a preselected lower limit, the pressure switch 92 associated with that circuit will actuate and shut-down the compressor associated with that circuit before the loss of refrigerant charge is substantial enough as to result in damage to the compressor. [0030] In a conventional refrigeration system having multiple independent refrigerant circuits that have a conventional multi-circuit heat exchanger in common, including a first refrigerant circuit having a first compressor for circulating refrigerant through a first heat exchange circuit of the common heat exchanger and a second refrigerant circuit having a second compressor for circulating refrigerant through a second heat exchange circuit of the common heat exchanger, the refrigeration system is exposed to the potential of cross-contamination in the event that refrigerant leaks from one heat exchange circuit into the other heat exchange circuit. Such contamination will adversely impact system performance and can result in damage to one or more of the compressors in the refrigeration system. [0031] Referring now to FIGs. 2 and 3 in particular, a baffle assembly 54 disposed within the interior volume of the first manifold 50 divides the interior volume of the first manifold 50 into the first chamber and the second chamber of the first manifold. The baffle assembly 54 includes a first flow impervious member 54A and a second flow impervious member 54B. Each baffle member 54A, 54B extends generally transversely across the interior volume of the first manifold 50. The first baffle member 54A and the second baffle member 54B are disposed in spaced apart relationship so as to a void space 80 within the interior volume of the first manifold 50 between the first baffle member 54A and the second baffle member 54. A vent port 90 opens through a section of the wall of first manifold 50 that extends between the first baffle member 54A and the second baffle member 54B. The vent port 90 establishes an open flow path between the void space 90 and a region exterior of the first manifold 50 whereby any refrigerant that may leak into the void space 90 from either the first chamber or the second chamber of the first manifold 50 through a fissure or crack or other hole in one of the first baffle member 54A or the second baffle member 54B is vented directly to the atmosphere exterior of the first manifold 50.

[0032] Referring now to FIG. 5 in particular, a baffle assembly may also be disposed within the interior volume of the second manifold 60 to divide the interior volume of the second manifold 60 into the first chamber 61 and the second chamber 63. The baffle assembly includes a first flow impervious member 62 A and a second flow impervious member 62B. Each baffle member 62A, 62B extends generally transversely across the interior volume of the second manifold 60. The first baffle member 62A and the second baffle member 62B are disposed in spaced apart relationship so as to a void space 80 within the interior volume of the second manifold 60 between the first baffle member 62A and the second baffle member 62B. A vent port 90 opens through a section of the wall of first manifold 50 that extends between the first baffle member 62 A and the second baffle member 62B. The vent port 90 establishes an open flow path between the void space 80 and a region exterior of the second manifold 60 whereby any refrigerant that may leak into the void space 80 from either the first chamber 61 or the second chamber 63 of the second manifold 60 through a fissure or crack or other hole in one of the first baffle member 62A or the second baffle member 62B is vented directly to the atmosphere exterior of the second manifold 60.

[0033] The terminology used herein is for the purpose of description, not limitation. Specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as basis for teaching one skilled in the art to employ the present invention. While the present invention has been particularly shown and described with reference to the exemplary embodiments as illustrated in the drawing, it will be recognized by those skilled in the art that various modifications may be made without departing from the spirit and scope of the invention. Those skilled in the art will also recognize the equivalents that may be substituted for elements described with reference to the exemplary embodiments disclosed herein without departing from the scope of the present invention. [0034] Therefore, it is intended that the present disclosure not be limited to the particular embodiment(s) disclosed as, but that the disclosure will include all embodiments falling within the scope of the appended claims.