This disclosure relates generally to heat exchangers and, more particularly, to a heat exchanger configured for use as an outdoor heat exchanger in residential air conditioning and heat pump applications.
In recent years, much interest and design effort has been focused on the efficient operation of heat exchangers of refrigerant systems, particularly condensers and evaporators. A relatively recent advancement in heat exchanger technology includes the development and application of parallel flow (such as microchannel, minichannel, brazed-plate, plate-fin, or plate-and frame) heat exchangers as condensers and evaporators.
According to a first embodiment, a heat exchanger is provided including a first header, a second header, and a plurality of heat exchange tubes arranged in a spaced parallel relationship and fluidly coupling the first and second headers. At least one of the first header, second header and the plurality of heat exchange tubes includes a bend. The heat exchanger having an aspect ratio between about 2 and 6 after formation of the bend.
In addition to one or more of the features described above, or as an alternative, in further embodiments the plurality of heat exchange tubes have a tube depth between about 8 mm and about 20 mm.
In addition to one or more of the features described above, or as an alternative, in further embodiments when the heat exchanger is configured for use in a refrigerant system having a capacity less than three tons, the depth of the plurality of heat exchange tubes is about 10 mm.
In addition to one or more of the features described above, or as an alternative, in further embodiments when the heat exchanger is configured for use in an refrigerant system having a capacity less than three tons, the depth of the plurality of heat exchange tubes is about 12 mm.
In addition to one or more of the features described above, or as an alternative, in further embodiments when the heat exchanger is configured for use in a refrigerant system having a capacity of at least three tons, the depth of the plurality of heat exchange tubes is about 16 mm.
In addition to one or more of the features described above, or as an alternative, in further embodiments the plurality of heat exchange tubes have a height of about 1.3 mm±0.3 mm.
In addition to one or more of the features described above, or as an alternative, in further embodiments the plurality of heat exchange tubes have a tube pitch between about 8.9 mm and about 15.5. mm.
In addition to one or more of the features described above, or as an alternative, in further embodiments the plurality of heat exchange tubes have a tube pitch of about 9.3 mm.
In addition to one or more of the features described above, or as an alternative, in further embodiments the heat exchanger is configured for use in an air conditioning system.
In addition to one or more of the features described above, or as an alternative, in further embodiments the first header and the second header are oriented generally vertically and the plurality of heat exchange tubes extend generally horizontally and include the at least one bend.
In addition to one or more of the features described above, or as an alternative, in further embodiments the plurality of heat exchange tubes are bent to form a C or U-shape.
In addition to one or more of the features described above, or as an alternative, in further embodiments the heat exchanger is configured with a first pass and a second pass. A first portion of the plurality of heat exchange tubes is configured for the first pass, and a second portion of the plurality of heat exchange tubes is configured for the second pass. A ratio of a number of heat exchange tubes within the first portion and the second portion is about 2.5 to 6.
In addition to one or more of the features described above, or as an alternative, in further embodiments the heat exchanger is configured for use in a heat pump system.
In addition to one or more of the features described above, or as an alternative, in further embodiments the first header and the second header are oriented generally horizontally and include the at least one bend, the plurality of heat exchange tubes extend generally vertically there between.
In addition to one or more of the features described above, or as an alternative, in further embodiments the first header and the second header are bent to form a C or U-shape.
In addition to one or more of the features described above, or as an alternative, in further embodiments the heat exchanger is configured with a first pass and a second pass. A first portion of the plurality of heat exchange tubes is configured for the first pass, and a second portion of the plurality of heat exchange tubes is configured for the second pass. A ratio of a number of heat exchange tubes within the first portion and the second portion is about 0.3 to about 3.
In addition to one or more of the features described above, or as an alternative, in further embodiments a plurality of fins is disposed in thermal communication with the plurality of heat exchange tubes.
In addition to one or more of the features described above, or as an alternative, in further embodiments the plurality of fins have a louver length between about 80% and 90% of a fin height.
In addition to one or more of the features described above, or as an alternative, in further embodiments the plurality of fins have a louver pitch between about 1 mm and 1.7 mm.
In addition to one or more of the features described above, or as an alternative, in further embodiments wherein the plurality of fins have a louver angle between about 28 degrees and about 45 degrees.
In addition to one or more of the features described above, or as an alternative, in further embodiments when the heat exchanger is configured for use in an air conditioning system, the plurality of fins have a louver angle of about 32 degrees.
In addition to one or more of the features described above, or as an alternative, in further embodiments when the heat exchanger is configured for use in a heat pump system, the plurality of fins have a louver angle of about 43 degrees.
In addition to one or more of the features described above, or as an alternative, in further embodiments the plurality of fins have a fin density between about 10 fins per inch and about 25 fins per inch.
In addition to one or more of the features described above, or as an alternative, in further embodiments the plurality of fins have a fin thickness between about 0.07 mm and about 0.1 mm.
In addition to one or more of the features described above, or as an alternative, in further embodiments the heat exchanger is configured for use in an air conditioning system, the plurality of fins have a fin density of 23 fins per inch.
In addition to one or more of the features described above, or as an alternative, in further embodiments when the heat exchanger is configured for use in a heat pump system, the plurality of fins have a fin density of 16 fins per inch.
In addition to one or more of the features described above, or as an alternative, in further embodiments one of the first header and second header includes the bend and the bend further comprises a ratio of bend radius divided by a total thickness of the heat exchanger. The ratio of the bend radius to the total thickness of the heat exchanger is greater than 4.
In addition to one or more of the features described above, or as an alternative, in further embodiments the plurality of heat exchange tubes includes the bend and the bend further comprises a ratio of bend radius divided by a total thickness of the heat exchanger. The ratio of the bend radius to the total thickness of the heat exchanger is greater than 10.
In addition to one or more of the features described above, or as an alternative, in further embodiments, the heat exchanger is part of an air management system. The air management system is in fluid communication with the heat exchanger and is configured to impart an airflow having an average face velocity of greater than or equal to 200 feet per minute over an outer surface of the heat exchanger when the system is operating.
In addition to one or more of the features described above, or as an alternative, in further embodiments the air management system comprises a fan.
In addition to one or more of the features described above, or as an alternative, in further embodiments a noise level of the system at a measurement distance of 1 meter from the system is less than or equal to 65 dBa.
The subject matter, which is regarded as the present disclosure, 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 present disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the present disclosure, together with advantages and features, by way of example with reference to the drawings.
Microchannel heat exchangers as outdoor coils entered residential cooling only air conditioning applications and are being considered for the residential heat pump applications as well. Due to regulatory efficiency requirements, sound constraints, and a non-optimized heat exchanger design, the size of the outdoor heat exchanger is typically large. As a result, the heat pump and air conditioning systems incur higher costs and have a higher refrigerant charge. Current legislation limits the amount of charge of refrigerant systems, and heat exchangers in particular, containing most low global warming potential refrigerants (currently classified as A2L substances).
Microchannel heat exchangers have a small internal volume and therefore store less refrigerant charge than conventional round tube plate fin heat exchangers. Although a lower refrigerant charge is generally beneficial, the smaller internal volume of microchannel heat exchangers makes them extremely sensitive to overcharge or undercharge situations, which could result in refrigerant charge imbalance, degrade refrigerant system performance, and cause nuisance shutdowns. In addition, the refrigerant charge contained in the manifolds of the microchannel heat exchanger, particularly when the heat exchanger operates as a condenser, is significant, such as about half of the total heat exchanger charge. As a result, the refrigerant charge reduction potential of the heat exchanger is limited.
Referring now to
Referring now to
As known, a plurality of heat transfer fins 70 (
Referring again to
Due to the vertical orientation of the heat exchange tubes 50 in evaporator or heat pump applications, configurations of a parallel flow heat exchanger 20 having a multi-pass flow orientation have not been feasible due to refrigerant maldistribution, which is particularly challenging at high vapor qualities, such as in the intermediate manifolds for example. With reference now to
To form a multi-pass flow configuration, at least one of the first manifold 30 and the second manifold 40 includes two or more fluidly distinct sections or chambers. In an embodiment, the fluidly distinct sections are formed by coupling separate manifolds together to form the first or second manifold 30, 40. Alternatively, a baffle or divider plate (not shown) known to a person of ordinary skill in the art may be arranged within at least one of the first header 30 and the second header 40 to define a plurality of fluidly distinct sections therein.
With reference now to
As shown in
The heat exchanger 20 is generally optimized to minimize size and cost while similarly reducing refrigerant charge for a variety of air management systems and airflow configurations. Regardless of the pass configuration, the heat exchanger 20 may have a face area between about 30% and about 60% of a baseline round tube plate fin heat exchanger. In addition, an air management system including a fan is configured to move air over an outer surface of the heat exchanger 20 with a face velocity of up to three times that of a baseline conventional propeller fan. For example, when the air management system is configured as an air conditioning system, the minimum face velocity is about 270 ft/min and when the air management system is configured as a heat pump system the minimum face velocity is about 220 ft/min. The heat exchanger 20 may also be configured such that a ratio of the heat exchange tubes 50a in the first pass to the heat exchange tubes 50b in the second pass is about 2.5 to 6. In another embodiment, a ratio of the length of the heat exchanger 20 to the height of the heat exchanger 20 measured in a plane coinciding with the face area of the heat exchanger 20 (e.g. a plane perpendicular to the dimension along which the tube depth is measured) when folded in the bent configuration, also referred to as the aspect ratio, is between about 2 and 6.
With reference now to
Although the heat exchanger 20 of
As the refrigerant flows sequentially through the second and first groups 50b, 50a of heat exchanger tubes 50, or alternatively, through the second and third groups 50b, 50c of heat exchanger tubes 50, heat from an adjacent flow of air A, is transferred to the refrigerant. As a result, a substantially vaporized refrigerant is provided at the outlets 80. Alternatively, refrigerant is configured to flow in a reverse direction through the heat exchanger 20 when operated as a condenser.
The face area of the heat exchanger 20 configured for use in a heat pump is between about 30% and about 70% of the baseline round tube plate fin heat exchanger with a higher face velocity of up to three times a baseline conventional propeller fan. This increased face velocity occurs as a result of the combination of increased air flow and the smaller face area of the heat exchanger 20. In addition, the noise generated by the heat exchanger 20 may be reduced compared to conventional heat exchangers. As a result, the noise of a system containing by the heat exchanger 20 is at or below an allowable noise level for residential applications. For example, the noise level of a refrigerant system measured at a distance of 1 meter from the system is less than or equal to 65 dBa.
The heat exchanger 20 may also be configured such that when operated as a condenser, a ratio of the heat exchange tubes 50 in the first pass (50a and 50c) to the second pass (50b) is about 0.3 to 3. In another embodiment, the aspect ratio of the heat exchanger 20 is between about 2 and 6.
To further optimize the heat exchanger 20, for example a heat exchanger 20 configured for use in any heat transfer application and having any tube depth, the size of the headers 30, 40 may be reduced, such that the headers 30, 40 have an inner diameter equal to a width of one of the heat exchange tubes 50 plus 1-4 mm (millimeters). In addition, the tubes 50 of the heat exchangers 20 may have a depth between about 8 mm and 16 mm, and in an embodiment between about 10 to 12 mm, or 10 mm. Further, in embodiments where the heat exchanger 20 is configured for use in a system having a capacity between about three tons and five tons, the tubes 50 may have a depth between about 12 mm and 22 mm, more specifically 14 to 16 mm. In another embodiment, the tubes 50 may have a height of about 1.3 mm±0.3 mm The tubes of the heat exchanger 20 may additionally have a tube pitch between about 8.9 mm and 15.5 mm, e.g., 9.3 mm.
With respect to the fins 70, the fins 70 mounted to each of the plurality of tubes 50 may have a louver length between about 80%-90% of the fin height, a louver pitch between about 0.8 mm and 1.7 mm, e.g., 1.3 mm, and a louver angle between 28 degrees and 47 degrees. In an embodiment, the louver angle of the fins 70 in a heat exchanger 20 configured for use in an air conditioning system is about 30 degrees and the louver angle in a heat exchanger configured for use in a heat pump is about 45 degrees. The fin density in a heat exchanger 20 for use in an air conditioning system may be between about 18-25 fins/inch, e.g., 23 fins per inch. Alternatively, the fin density of a heat exchanger 20 configured for use in a heat pump may be between about 12-18 fins/inch, e.g., about 16 fins per inch.
The heat exchangers 20 provided herein result in a substantial size and therefore cost reduction, between 30 and 70% compared to other heat exchangers.
Further, this reduced size can allow for refrigerant charge of the system to be reduced from 50-70% compared to the baseline heat exchanger. The heat exchangers 20 additionally have a higher performance due to improvements in both refrigerant and air distribution, along with the optimal heat transfer and hydraulic resistance balance by optimizing the number of refrigerant passes and airflow.
In an embodiment, the heat exchanger 20 has a multi-slab configuration such that the heat exchanger 20 includes at least a first slab 80 and a second, substantially identical slab 82 arranged downstream from the first slab 80 relative to an airflow A. In an embodiment, the plurality of heat exchange tubes 50, or alternatively, the headers 30, 40 include at least one bend to form the first heat exchanger slab 80 and the second heat exchanger slab 82. However, in alternate embodiments, the first slab 80 and the second slab 82 may be distinct. Various configurations of a heat exchanger 20 having a first and second heat exchanger slab 80, 82 are illustrated in
A total thickness of the heat exchanger 20 is measured between an exterior surface of a first heat exchanger slab and an exterior surface of the furthest heat exchanger slab of the heat exchanger 20. In embodiments where the plurality of tubes 50 are bent, the ratio of the bend radius (measured to a centerline of the heat exchanger 20) to the total thickness of the heat exchanger 20 at the bend is greater than 10, and in an embodiment is equal to about 15±4. In embodiments where the headers 30, 40 of the heat exchanger 20 are bent to define a plurality of heat exchanger slabs, the ratio of the bend radius to the total thickness of the heat exchanger at the bend is greater than 4, and in an embodiment is equal to about 7±2.5. In addition, when the header 30, 40 is bent about 180 degrees, a spacer may be positioned on opposing sides of the bend to prevent the adjacent portions from contacting one another. By forming the one or more bends of the heat exchanger tubes 50 or the headers 30, 40 with a minimum bend radius, the formation of sharp bends that may constrict the flow of a fluid there through are eliminated.
A heat exchanger, comprising a first header; a second header; a plurality of heat exchange tubes arranged in spaced parallel relationship and fluidly coupling the first header and second header; wherein one of the first header, second header and the plurality of heat exchange tubes include a bend, the heat exchanger having an aspect ratio between 2 and 6 after formation of the bend.
The heat exchanger according to an embodiment, wherein the plurality of heat exchange tubes have a tube depth between about 8 mm and about 20 mm.
The heat exchanger according to embodiment 2, wherein when the heat exchanger is configured for use in a refrigerant system having a capacity less than three tons, the depth of the plurality of heat exchange tubes is about 10 mm.
The heat exchanger according to embodiment 2, wherein when the heat exchanger is configured for use in an refrigerant system having a capacity less than three tons, the depth of the plurality of heat exchange tubes is about 12 mm.
The heat exchanger according to embodiment 2, wherein when the heat exchanger is configured for use in a refrigerant system having a capacity of at least three tons, the depth of the plurality of heat exchange tubes is about 16 mm.
The heat exchanger according to any of the preceding embodiments, wherein the plurality of heat exchange tubes have a height of about 1.3 mm±0.3 mm.
The heat exchanger according to any of the preceding embodiments, wherein the plurality of heat exchange tubes have a tube pitch between about 8.9 mm and about 15.5. mm.
The heat exchanger according to claim 7, wherein the plurality of heat exchange tubes have a tube pitch of about 9.3 mm.
The heat exchanger according to any of the preceding embodiments, wherein the heat exchanger is configured for use in an air conditioning system.
The heat exchanger according to embodiment 9, wherein the first header and the second header are oriented generally vertically and the plurality of heat exchange tubes extend generally horizontally and include the at least one bend.
The heat exchanger according to embodiment 10, wherein the plurality of heat exchange tubes are bent to form a C or U-shape.
The heat exchanger according to any of embodiments 9-11, wherein the heat exchanger is configured with a first pass and a second pass, a first portion of the plurality of heat exchange tubes being configured for the first pass, and a second portion of the plurality of heat exchange tubes being configured for the second pass, wherein a ratio of a number of heat exchange tubes within the first portion and the second portion is about 2.5 to 6.
The heat exchanger according to any of the preceding embodiments, wherein the heat exchanger is configured for use in a heat pump system.
The heat exchanger according to embodiment 13, wherein the first header and the second header are oriented generally horizontally and include the at least one bend, the plurality of heat exchange tubes extend generally vertically there between.
The heat exchanger according to embodiment 14, wherein the first header and the second header are bent to form a C or U-shape.
The heat exchanger according to any of embodiment 13-15, wherein the heat exchanger is configured with a first pass and a second pass, a first portion of the plurality of heat exchange tubes being configured for the first pass, and a second portion of the plurality of heat exchange tubes being configured for the second pass, wherein a ratio of a number of heat exchange tubes within the first portion and the second portion is about 0.3 to about 3.
The heat exchanger according to any of the preceding embodiments, wherein a plurality of fins is disposed in thermal communication with the plurality of heat exchange tubes.
The heat exchanger according to embodiment 17, wherein the plurality of fins have a louver length between about 80% and 90% of a fin height.
The heat exchanger according to any of embodiments 17-18, wherein the plurality of fins have a louver pitch between about 1 mm and 1.7 mm.
The heat exchanger according to any of embodiments 17-19, wherein the plurality of fins have a louver angle between about 28 degrees and about 45 degrees.
The heat exchanger according to embodiment 20, wherein when the heat exchanger is configured for use in an air conditioning system, the plurality of fins have a louver angle of about 32 degrees.
The heat exchanger according to embodiment 20, wherein when the heat exchanger is configured for use in a heat pump system, the plurality of fins have a louver angle of about 43 degrees.
The heat exchanger according to any of embodiments 17-22, wherein the plurality of fins have a fin density between about 10 fins per inch and about 25 fins per inch.
The heat exchanger according to any of embodiments 17-23, wherein the plurality of fins have a fin thickness between about 0.07 mm and about 0.1 mm.
The heat exchanger according to embodiment 24, wherein when the heat exchanger is configured for use in an air conditioning system, the plurality of fins have a fin density of 23 fins per inch.
The heat exchanger according to embodiment 24, wherein when the heat exchanger is configured for use in a heat pump system, the plurality of fins have a fin density of 16 fins per inch.
The heat exchanger of any of the preceding embodiments, wherein one of the first header and second header includes the bend and the bend further comprises a ratio of bend radius divided by a total thickness of the heat exchanger, wherein the ratio is greater than 4.
The heat exchanger of any of claims the preceding embodiments, wherein the plurality of heat exchange tubes includes the bend and the bend further comprises a ratio of bend radius divided by a total thickness of the heat exchanger, wherein the ratio is greater than 10.
A system comprising: the heat exchanger according to any of the preceding embodiments; and an air management system in fluid communication with the heat exchanger and configured to impart on an airflow having an average face velocity of greater than or equal to 200 feet per minute over an outer surface of the heat exchanger when the system is operating.
The system of embodiment 29, wherein the air management system comprises a fan.
The system of any of embodiments 29-30, a noise level of the system at a measurement distance of 1 meter from the system is less than or equal to 65 dBa.
While the present disclosure 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 present disclosure. 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.
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/IB2015/002175 | 10/12/2015 | WO | 00 |