BACKGROUND OF THE INVENTION
The subject matter disclosed herein relates to heat exchangers. More specifically, the subject disclosure relates to tube and fin configuration for heat exchangers.
Micro-channel heat exchangers have represented the typical construction of heat exchangers for, for example, automotive and heating, ventilation and air conditioning (HVAC) applications, for several years. These heat exchangers are finding wider application in residential and even aerospace HVAC products due to their compactness, relatively low cost, and reduced refrigerant charge when compared to other heat exchanger configurations.
In micro-channel heat exchangers, liquid or two-phase refrigerant flows through small ports internal to extruded tubes. Air flows through folded fins arranged between the tubes. Due to the high surface density of this construction, and a flat shape of the typical tube, these heat exchangers are prone to moisture and condensate retention and subsequent frost accumulation issues. This is especially problematic when the tubes are arranged horizontally. Water collects on the horizontal surfaces of the tubes, resulting in higher flow and thermal resistance as well as corrosion and pitting of the tube surfaces.
BRIEF DESCRIPTION OF THE INVENTION
According to one aspect of the invention, a heat exchanger includes a plurality of tubes positioned substantially transverse to a direction of airflow through the heat exchanger and arranged in a plurality of tube rows extending substantially along the direction of airflow. The heat exchanger further includes a plurality of webs substantially integral to two or more tubes of the plurality of tubes, each web extending between and connected to adjacent tubes of the plurality of tubes. At least one web has an enhanced surface such as a louver, tab, or vortex generator. (the main claim should be the combination of the tube, web, and surface enhancements. We may have a configuration with round tubes with some form of web surface enhancement. I don't believe this is covered in the claims)
According to another aspect of the invention, a heat exchanger includes a plurality of tubes positioned substantially transverse to a direction of airflow through the heat exchanger and arranged in a plurality of tube rows extending substantially along the direction of airflow. At least one tube of the plurality of tubes includes two or more fluid-conveying pathways. A plurality of webs are substantially integral to two or more tubes of the plurality of tubes. Each web extends between and is connected to adjacent tubes of the plurality of tubes.
According to yet another aspect of the invention, a heat exchanger includes a plurality of tubes positioned substantially transverse to a direction of airflow through the heat exchanger and arranged in a plurality of tube rows extending substantially along the direction of airflow. A plurality of webs are substantially integral to at least two tubes of the plurality of tubes. Each web extends between and is connected to adjacent tubes of the plurality of tubes. A plurality of tabs are located at the plurality of webs substantially transverse to the airflow to generate vortices in the airflow.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
FIG. 1 is a perspective view of an embodiment of an integral tube and fin heat exchanger;
FIG. 2 is an embodiment of an integral tube and fin heat exchanger having elliptical tubes;
FIG. 3 is an embodiment of an integral tube and fin heat exchanger having airfoil-shaped tubes;
FIG. 4 is an embodiment of an integral tube and fin heat exchanger having web louvers;
FIG. 5 is an embodiment of an integral tube and fin heat exchanger having multiple web louvers;
FIG. 6 is an embodiment of an integral tube and fin heat exchanger having multiple fluid pathways per tube;
FIG. 7 is another embodiment of an integral tube and fin heat exchanger having multiple fluid pathways per tube;
FIG. 8 is yet another embodiment of an integral tube and fin heat exchanger having multiple fluid pathways per tube;
FIG. 9 is still another embodiment of an integral tube and fin heat exchanger having multiple fluid pathways per tube;
FIG. 10 is an embodiment of an integral tube and fin heat exchanger including web tabs;
FIG. 11 is a schematic of vortex flow through an embodiment of an integral tube and fin heat exchanger;
FIG. 12 is another embodiment of an integral tube and fin heat exchanger including web tabs;
FIG. 13 is another schematic of vortex flow through an embodiment of an integral tube and fin heat exchanger; and
FIG. 14 is another embodiment of a heat exchanger 10.
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
DETAILED DESCRIPTION OF THE INVENTION
Shown in the FIG. 1 is a heat exchanger 10 structure. In some embodiments, the heat exchanger 10 is a micro-channel heat exchanger (MCHX). The heat exchanger 10 has an integrated tube-fin structure where a plurality of tubes 12 are arranged with a plurality of webs 14 extending between adjacent tubes 12 of the plurality of tubes 12, and acting as fins in this structure. The webs 14 in some embodiments are substantially integral to the tubes 12. A refrigerant flow 16, for example, a liquid or two phase refrigerant, is flowed through the plurality of tubes 12. While the term “refrigerant flow” is utilized throughout the present application, it is to be appreciated that any selected liquid, gas, or two-phase fluid may be flowed through the plurality of tubes 12 for the purposes of heat transfer. In some embodiments, the plurality of tubes 12 are arranged in rows 18. An airflow 20 flows across the plurality of tubes 12 and the plurality of webs 14 such that thermal energy is transferred between the airflow 20 and the refrigerant flow 16 via the tube 12 and web 14 structure. In some embodiments, a direction of the airflow 20 is substantially perpendicular to the refrigerant flow 16.
Referring now to FIG. 2, the tubes 12 have a cross-section that improves air flow 20 and thus heat transfer between the airflow 20 and the heat exchanger 10. In some embodiments, as shown in FIG. 2, the cross-section of the tubes 12 are elliptical or may be airfoil shaped as shown in FIG. 3. Elliptic or airfoil shapes reduce the wake size behind the tubes 12, which decreases pressure drop and improves heat transfer. Referring to FIG. 4, the webs 14 include a plurality of louvers 22 formed in the webs 14 which extend into the airflow 20. The louvers 22 may be formed by, for example, a punching operation which cuts the web 14 on three sides of the louver 22 and folds the louver 22 into position, resulting in a web opening 24 in the web 14. In some embodiments, the louvers 22 each have a louver face 42 which is aligned substantially parallel to the airflow 20. In some embodiments, as shown in FIG. 5, the webs 14 may be configured with multiple rows of multiple louvers 22 between adjacent tubes 12. Utilizing louvers 22 and web openings 24 allows for reduction in material and refrigerant volume compared to a conventional micro-channel heat exchanger and allows for drainage of condensate through the web openings 24 to reduce condensate/ice buildup and/or corrosion.
In some embodiments, the webs 14 between adjacent tubes 12 are substantially equal in web length 26. It is to be appreciated, however, that the web length 26 may vary as desired. In some embodiments, as also shown in FIG. 2, the tubes 12 in a first row 18a of tubes 12 can be offset or staggered relative to an adjacent second row 18b of tubes 12 along a length 30 of the heat exchanger 10 to allow for a more compact structure and to increase heat transfer between the airflow 20 and the refrigerant flow 16.
Referring now to FIG. 6, some embodiments it is desired to increase a distance between the tubes 12 or reduce the number of tubes 12 because heat transfer via the webs 14 is highly effective. Further, reducing a number of tubes 12 reduces necessary connections of tubes 12 to a header (not shown) which distributes refrigerant flow 16 to the tubes 12. A reduction of the number of tubes 12 alone, however, increases a refrigerant flow pressure drop for the same capacity and flow rates. Further, a reduction of the number of tubes 12 combined with an increase in the cross-sectional area of the tubes 12 to increase flow capacity, results in a reduction in heat transfer due to an increase in a hydraulic diameter of the tubes 12 and a reduction in a total refrigerant side heat transfer area.
The embodiments of FIGS. 6-8 address this problem by providing multiple smaller refrigerant pathways 32 in each tube 12 of the plurality of tubes 12. As shown in FIGS. 6, 7, and 8, respectively, two, three, or four pathways 32 may be arranged in each tube 12 to decrease the pressure drop compared to a similar-sized tube 12 with a single pathway while increasing the heat transfer capability of the tube 12 and reducing connections to the header. While it is possible to include more than four pathways 32 in the tube 12, the heat transfer effectiveness of the additional pathways will be decreased since heat conduction from innermost pathways will be limited compared to the outermost pathways. As shown in FIG. 9, louvers 22 may be utilized with these multi-pathway 32 configurations to increase heat transfer and to provide condensate drainage through the web openings 24.
Referring now to FIG. 10, the heat exchanger 10 may include vortex generators, for example, tabs 34 disposed along the web 14. The tabs 34 are oriented across the airflow 20, as shown schematically in FIG. 11, in order to generate streamwise votices 36 in the airflow 20 as the airflow passes along the web 14. The presence of vortices 36 can increase heat transfer between the web 14 and the airflow 20. Referring again to FIG. 10, the tabs 34 are triangular in shape, or may be other shapes, for example, trapezoidal, or asymmetrically polygonal, or the like, to generate the desired vortices 36. The tabs 34 may be disposed in rows 40 extending along a tube length 38, with multiple rows, for example, two or three rows of tabs 34 between adjacent tubes 12. The positions of tabs 34 in a first row 40a may be staggered relative to the positions of tabs 34 in a second row 40b, or may be aligned, depending on the vortex 36 desired.
Comparing FIGS. 10 and 12, it can be seen that in some embodiments the tabs 34 are aligned such that a tab tip 42 of the tabs 34 faces the same direction, while in other embodiments, as shown in FIG. 12, tab tips 42 of tabs 34 or rows of tabs 34 may face opposing directions. Further, as shown in FIG. 13, tabs 34 may be located and oriented to boost a strength of the vortices 36 along the web 14.
Referring to FIG. 14, in some embodiments, the webs 14 may not be substantially planar, but may be a wave or ruffle shape to further have a desired effect on the airflow 20, such as increased vortex generation. The wavy web 14 may be utilized in conjunction with the louvers 22, and/or tabs 34.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
Patent Application
20140027098
