Heat exchanger assembly
A heat exchanger, includes a plurality of MCC microchannel tubes, each microchannel tube of the plurality of microchannel tubes having at least one microchannel fluid passage defined therein and having a chord, the chord being the orthogonal distance from a leading edge to a trailing edge, each microchannel tube of the plurality of microchannel tubes being disposed such that the chord is less than orthogonally disposed relative to a heat exchanger plane. A method of forming such a heat exchanger is further included.
This invention relates generally to cooling systems, and more particularly to heat exchangers usable in such cooling systems.
BACKGROUND OF THE INVENTIONTypical refrigeration systems often utilize conventional fin-and-tube heat exchanger coils to dissipate heat from refrigerant passing through the heat exchanger coils. Usually, in large-scale cooling systems, a single, oftentimes large, conventional fin-and-tube heat exchanger coil 100, as depicted in prior art
Usually, in large-scale cooling systems, the fin-and-tube heat exchanger coil(s) is/are positioned outside a commercial building, such as on a rooftop, to allow heat transfer between the fin-and-tube heat exchanger coil and the outside environment (i.e., to allow the heat in the refrigerant to dissipate into the outside environment). Further, natural or ram airflow may be augmented by a mechanical airflow that may be provided by a fan, for example, to assist in air-cooling the fin-and-tube heat exchanger coil.
Fin-and-tube heat exchanger coils, depicted generally at 100, in prior art
A more recent form of heat exchanger is the microchannel coil (MCC) heat exchanger. Microchannel coil (MCC) heat exchangers are typically made of aluminum, replacing the costlier copper of the fin-and-tube heat exchanger coils. Further, in similar heat exchange applications, MCC heat exchangers can be made significantly smaller than fin-and-tube heat exchanger coils that effect similar heat exchanges. To date, however, microchannel coil (MCC) heat exchangers are known to be quite sensitive to the direction of airflow relative to the plane of the MCC heat exchanger. Efficiency drops off dramatically as the direction of airflow varies from the normal relative to the plane of the MCC heat exchanger.
Currently, the major application of microchannel coils is in the automotive industry. Microchannel coils 110 may be used as a condenser and/or an evaporator in the air conditioning system of an automobile. See prior art
Referring to
The MCC tube heat exchanger 110 includes a plurality of microchannel tubes 112. Each microchannel tube 112 has a length dimension 114 extending from header 116 to header 118, as depicted in prior art
The prior art MCC tube heat exchanger 110 further includes fins 130, as depicted in prior art
The plane of adjacent fins 130 of some prior art MCC heat exchangers 110 is angled with respect to one another. The ribbon forming the fins 130 has very sharp bends. See U.S. Pat. No. 6,988,538. Such alternate angling reduces the number of heat transferring heat exchange surfaces 132 that can be included in a given length 114 of the microchannel tube 112 and the sharp bends 131 provide for only a minimal heat conducting joint with the respective microchannel tube 112. For these reasons the alternating angling disposition is not favored as being less efficient than the parallel array disposition of prior art
For most efficient heat exchange in the prior art, the flow of air through the MCC tube heat exchanger 110 is normal to the plane 125 of the heat exchanger 110, as depicted in prior art
Angling the known MCC tube heat exchanger 110 to the direction of airflow results in known and calculable reductions of efficiency, as compared to normal airflow with the same MCC tube heat exchanger 110. Such angling is noted in Prior art
The above reduction of mass flow has led engineers to angle known MCC heat exchangers 110 to the relative airflow, such as the 60 degree angle of prior art
There is a need in the industry for more efficient MCC tube heat exchangers in applications in which the flow of air is not normal to the plane of the heat exchanger. In this situation, the direction of airflow is altered from the intake side of the MCC tube heat exchanger to the exhaust side by as much as ninety degrees. As noted above, with known MCC tube heat exchangers, such non-normal air flow significantly diminishes the efficiency of the MCC tube heat exchanger as compared to normal air flow on both the intake and exhaust sides of the MCC tube heat exchanger.
SUMMARY OF THE INVENTIONThe present invention substantially meets the aforementioned needs of the industry by providing a high efficiency MCC tube heat exchanger for use with air flows that are not normal to the MCC heat exchanger. The present invention provides, in one aspect, a heat exchanger assembly adapted to efficiently condense a refrigerant in a refrigeration system where the flow of air to the MCC tube heat exchanger is not normal. The MCC tube heat exchanger assembly includes at least one microchannel heat exchanger coil including an inlet header and an outlet header, each microchannel of the coil being angled with respect to the plane of the MCC heat exchanger.
The present invention provides, in a further aspect, a method of assembling a MCC tube heat exchanger assembly. The MCC tube heat exchanger assembly may be adapted to condense a refrigerant for use in a refrigeration system. The method includes forming a MCC tube heat exchanger assembly with angled microchannel tubes and/or fins that provide for increased efficiency of the MCC tube heat exchanger assembly when the MCC tube heat exchanger assembly is angled with respect to the direction of airflow, i.e. the air flow is not normal to the plane of the MCC tube heat exchanger assembly.
The present invention provides, in addition to microchannel tubes and fins oriented to non-normal air flow, a greater heat transfer area of the respective microchannels and fins for a given depth of the headers of the MCC heat exchanger. Efficiency of the device of the present invention is therefore improved by two means. The first is angling the microchannel tubes and fins into the airflow and the second is the greater heat changer area of the microchannel tubes and fins presented to the air flow that is made possible by the angling of the microchannels and/or fins.
The present invention is a heat exchanger that includes a plurality of MCC microchannel tubes, each microchannel tube of the plurality of microchannel tubes having at least one microchannel fluid passage defined therein and having a chord, the chord being the orthogonal distance from a leading edge to a trailing edge, each microchannel tube of the plurality of microchannel tubes being disposed such that the chord is less than orthogonally disposed relative to a heat exchanger plane. The present invention is further a method of forming such a heat.
The heat exchanger assembly of the present invention is depicted generally at 10 in the figures. The heat exchanger assembly 10 may be used as a heat exchanger in a large-scale refrigeration system, such as that found in many commercial applications and multi-unit residences. In such a refrigeration system, the heat exchanger assembly 10 is frequently positioned outside the building, such as on the rooftop of the building, to allow heat transfer from the heat exchanger assembly 10 to the outside environment. The coils 14 of the heat exchanger assembly 10 may be advantageously disposed in a non-normal relationship relative to the incoming airflow. The usual role of the heat exchanger assembly 10 in the refrigeration system is to receive compressed, gaseous refrigerant from one or more compressors (not shown), condense the gaseous refrigerant back into its liquid form, and discharge the compressed, liquid refrigerant to one or more evaporators (not shown) located inside the store. The liquid refrigerant is evaporated when it is passed through the evaporators, and the gaseous refrigerant is drawn into the one or more compressors for reprocessing into the refrigeration system.
Refrigerants are typically given an R-XXX designation, such as “R-134a” or “R-22.” Additionally, other compounds, such as anhydrous ammonia, for example, may be used in such a refrigeration system to provide sufficient cooling to the refrigeration system. If any of the R-XXX designated refrigerants is used as the refrigerant of choice, the components of the refrigeration system in contact with the R-XXX may be made from copper, aluminum, or steel, among other materials. However, as understood by those skilled in the art, other refrigerants may not be compatible with some materials. If anyhydrous ammonia, for example, is used as the refrigerant of choice, copper components of the refrigeration system in contact with the anyhydrous ammonia may corrode. Alternatively, other refrigerants (including both two-phase and single-phase refrigerants or coolants) may be used with the heat exchanger assembly 10.
In addition to large refrigeration systems as noted above, the heat exchanger assembly 10 may also be used in various process industries, where the heat exchanger assembly 10 may be a portion of a fluid cooling system using a single-phase coolant (e.g., glycol). In such an application, the role of the heat exchanger assembly 10 in the fluid cooling system is to receive heated liquid coolant from one or more heat sources (e.g., a pump or an engine, for example), cool the heated liquid, and discharge the cooled liquid coolant to one or more heat sources. The cooled liquid coolant is again heated when it is put in thermal contact with the one or more heat sources, and the heated coolant is routed by the pump for re-processing into the fluid cooling system.
Further, the heat exchanger assembly 10 may be used with vehicles, including in applications using either two-phase or single-phase refrigerants or coolants. Such applications include, for example, air conditioning systems and the engine cooling system. The application of the heat exchanger assembly 10 is particularly desirable in low frontal profile vehicles where it may be desirable to angle the heat exchanger assembly 10 with respect to the incoming airstream, such angling being necessary to achieve sufficient cooling while maintaining a desired low frontal profile of the vehicle.
As depicted in
As shown in
Each of the microchannel tubes 30 extends between a respective header 22 and respective header 26. As depicted in
Referring to
The microchannel tubes 30 may be separated into about twenty or less microchannels 42, with each microchannel 42 being about 0.5-2.0 mm in height and about 0.5-2.0 mm in width, compared to a diameter of about 9.5 mm (⅜″) to 12.7 mm (½″) for the internal passageway of a coil in a conventional fin-and-tube heat exchanger coil. However, in other constructions of the flat microchannel tubes 30, the microchannels 42 may be as small as 0.4 mm by 0.4 mm, or as large as 4 mm by 4 mm.
Referring to
Referring to
The microchannel tubes 30 may be made from extruded aluminum to enhance the heat transfer capabilities of the flat tubes 30. In the illustrated construction, the flat microchannel tubes 30 are about 22 mm wide. However, in other constructions, the flat microchannel tubes 30 may be as wide as 50 mm, or as narrow as 10 mm. Further, the spacing between adjacent flat microchannel tubes 30 may be about 9.5 mm. In other constructions, the spacing between adjacent flat microchannel tubes 30 may be as much as 20 mm, or as little as 3 mm.
In distinction with respect to the prior art, the microchannel tubes 30 of the present invention are disposed at an angle of less than ninety degrees with respect to the plane 40 of the MCC tube heat exchanger 14, the plane 40 including the longitudinal axes 44 of the headers 22, 26 and an orthogonally disposed line 46 extending between axles 44. The microchannel tubes 30 are therefore disposed such that chords 32 are also disposed less than orthogonally with respect to the plane 40.
In distinction to the above prior art microchannel heat exchanger 110, the heat exchanger 10 of the present invention mounted as depicted in
For further efficiency improvement of the present invention, the fin stock comprising the fins 50, as depicted in
The tilted fin stock arrangement of the present invention provides for a larger heat exchange surface 56 within the limited installation space defined between adjacent microchannel tubes 30. As depicted in
A further benefit of the tilted fins 50 of the present invention is that the bends 54 and the ribbon 52 comprising the fins 50 are formed of a flat section 60 formed between two smaller radius bends 62. The full area of the flat section 60 may be joined in a heat conductive joint to the sides 38 of the adjacent microchannel tubes 30. Such joint has a significantly greater area as compared to the joint defined between the bin 131 and the side 124 of the microchannel 112 in the prior art. A larger heat conducting joint results in greater transfer of heat from the microchannel 30 to the fin 50.
A depiction of
Aerodynamic performance improved by 10-20%
Fin stock surface increased by 15.6%
Tube surface increased by 6.4%.
The total estimation of thermal improvement from both the tilted tube installation and the tilted fin stock installation is estimated to be greater than 12%.
The heat exchanger assemblies are described and shown for exemplary reasons only, and are not meant to limit the spirit and/or scope of the present invention.
Claims
1. A heat exchanger, comprising:
- a plurality of MCC microchannel tubes, each microchannel tube of the plurality of microchannel tubes having at least one microchannel fluid passage defined therein and having a chord, the chord being the orthogonal distance from a leading edge to a trailing edge, each microchannel tube of the plurality of microchannel tubes being disposed such that the chord is less than orthogonally disposed relative to a heat exchanger plane.
2. The heat exchanger of claim 1, the chord of each microchannel tube of the plurality of microchannel tubes being disposed at an angle relative to the heat exchanger plane that is between ten and sixty degrees.
3. The heat exchanger of claim 1, the angled disposition of the chord resulting in an increased length of the chord, the increased length dimension of the chord providing for improved thermal performance by means of the resulting greater heat exchange surface area of a respective microchannel tube.
4. The heat exchanger of claim 1, providing for improved thermal performance by means of an increased surface area of each microchannel tube resulting from the angled disposition that results from the chord being less than orthogonally disposed relative to the heat exchanger plane.
5. The heat exchanger of claim 1, including a plurality of fins extending between adjacent microchannel tubes, the fins having heat exchange surfaces, the heat exchange surfaces being less than orthogonally disposed with respect to the sides of the respective adjacent microchannel tubes.
6. The heat exchanger of claim 5, the heat exchange surfaces of the fins being disposed at an angle relative to the heat exchanger plane that is less than a right angle and greater than forty-five degrees.
7. The heat exchanger of claim 5, providing for improved thermal performance by means of the angled disposition resulting of the heat exchange surfaces of the fins being less than orthogonally disposed relative to the heat exchanger plane, thereby resulting in a greater heat exchange surface of the fins.
8. The heat exchanger of claim 5, providing for improved thermal performance by means of an increased surface area of the fin heat exchange surface resulting from the angled disposition that results from the heat exchange surface of the fins being less than orthogonally disposed relative to the heat exchanger plane resulting in a greater microchannel surface area as compared to an orthogonally disposed radiator elements of the fins.
9. The heat exchanger of claim 1, each of the plurality of microchannel tubes being formed with curved sides.
10. The heat exchanger of claim 1, each of the plurality of microchannel tubes being formed in an airfoil shape.
11. A heat exchanger, comprising:
- a plurality of microchannel tubes; and
- a plurality of fins disposed between adjacent microchannel tubes, the fins having heat exchange surfaces, the heat exchange surfaces being less than orthogonally disposed with respect to a side of an adjacent microchannel tube.
12. The heat exchanger of claim 11, the heat exchange surfaces of the fins being disposed at an angle relative to the heat exchanger plane that is less than a right angle and greater than forty-five degrees.
13. The heat exchanger of claim 11, providing for improved thermal performance by means of the angled disposition resulting of the heat exchange surfaces of the fins being less than orthogonally disposed relative to the heat exchanger plane, thereby resulting in a greater heat exchange surface of the fins.
14. The heat exchanger of claim 11, providing for improved thermal performance by means of an increased surface area of the fin heat exchange surface resulting from the angled disposition that results from the heat exchange surface of the fins being less than orthogonally disposed relative to the heat exchanger plane resulting in a greater microchannel surface area as compared to an orthogonally disposed radiator elements of the fins.
15. A method of forming a heat exchanger, comprising:
- forming a plurality of microchannel tubes, defining at least one microchannel fluid passage in each microchannel tube of the plurality of microchannel tubes;
- providing a microchannel dimension being a chord, the chord being the orthogonal distance from a leading edge to a trailing edge; and
- disposing each microchannel tube of the plurality of microchannel tubes such that the chord is less than orthogonally disposed relative to a heat exchanger plane.
16. The method of claim 15, including forming each of the plurality of microchannel tubes with curved sides.
17. The heat exchanger of claim 15, including forming each of the plurality of microchannel tubes in an airfoil shape.
18. The method of claim 15, including providing for improved thermal performance by means of the angled disposition resulting from the chord being less than orthogonally disposed relative to the heat exchanger plane resulting in a greater microchannel surface area as compared to an orthogonally disposed microchannel.
19. The method of claim 15, including extending a plurality of fins between adjacent microchannel tubes, the fins having heat transfer surfaces, and disposing the heat transfer surfaces less than orthogonally with respect to a side of a respective adjacent microchannel tube.
20. The method of claim 17, including disposing the heat transfer surfaces of the fins at an angle relative to the heat exchanger plane that is less than a right angle and greater than forty-five degrees.
Type: Application
Filed: May 7, 2007
Publication Date: Nov 13, 2008
Inventor: Kelvin Zhai (Plymouth, MN)
Application Number: 11/800,804
International Classification: F28F 1/00 (20060101);