Microchannel heat exchanger

A heat exchange tube for use in a heat exchanger including a first nose and a second nose aligned on an axis along a width of the heat exchange tube; an end port immediately adjacent to the first nose; wherein the end port has a non-circular, polygonal shape.

BACKGROUND

The present disclosure relates to the field of heat exchangers. More particularly, the present disclosure relates to microchannel heat exchangers.

Microchannel heat exchangers have emerged in the market as an effective heat transfer apparatus for HVAC applications. The weight of the heat exchange tubes in a microchannel heat exchanger has a large influence on the overall cost. Reducing the amount of material used in the heat exchange tubes, however, can have a negative effect on the burst pressure of the heat exchanger.

BRIEF DESCRIPTION

According to an embodiment, a heat exchange tube for use in a heat exchanger includes a first nose and a second nose aligned on an axis along a width of the heat exchange tube; an end port immediately adjacent to the first nose; wherein the end port has a non-circular, polygonal shape.

In addition to one or more of the features described herein, or as an alternative, further embodiments may include wherein the end port is rectangular.

In addition to one or more of the features described herein, or as an alternative, further embodiments may include wherein an interior side of the end port immediately adjacent to the first nose has a curvature of zero.

In addition to one or more of the features described herein, or as an alternative, further embodiments may include wherein the end port has an aspect ratio of width to height ranging from 0.1 to 10.

According to another embodiment, a heat exchange tube for use in a heat exchanger includes a first nose and a second nose aligned on a Y axis along a width of the heat exchange tube; an end port immediately adjacent to the first nose; a first interior port positioned between the first nose and the second nose; a second interior port positioned between the first nose and the second nose; the first interior port having a wall having a first thickness, B2, along a Z axis perpendicular to the Y axis; the second interior port having a wall having a second thickness, B1, along the Z axis; wherein the first thickness is greater than the second thickness.

In addition to one or more of the features described herein, or as an alternative, further embodiments may include wherein the first interior port is immediately adjacent to the end port.

In addition to one or more of the features described herein, or as an alternative, further embodiments may include a further first interior port, the further first interior port having a wall having the first thickness, B2, along the Z axis.

In addition to one or more of the features described herein, or as an alternative, further embodiments may include wherein the first interior port and the further first interior port are positioned on opposite sides of the second interior port along the Y axis.

In addition to one or more of the features described herein, or as an alternative, further embodiments may include a further second interior port, the further second interior port having a wall having the second thickness, B1, along the Z axis.

In addition to one or more of the features described herein, or as an alternative, further embodiments may include wherein the first interior port, the second interior port, the further second interior port and the further first interior port are arranged in sequence along the Y axis.

In addition to one or more of the features described herein, or as an alternative, further embodiments may include wherein a ratio of B2/B1ranges from 1.01 to E/(2B1), where E is a height of the heat exchange tube along the Z axis.

In addition to one or more of the features described herein, or as an alternative, further embodiments may include wherein a ratio of B2/B1ranges from 1.1 to 1.5.

According to another embodiment, a heat exchange tube for use in a heat exchanger includes a first nose and a second nose aligned on a Y axis along a width of the heat exchange tube; a port positioned between the first nose and the second nose; the port having an interior port height along a Z axis perpendicular to the Y axis; wherein the interior port height varies along the Y axis to define a throat in the port.

In addition to one or more of the features described herein, or as an alternative, further embodiments may include wherein the interior port height increases and decreases along the Y axis.

In addition to one or more of the features described herein, or as an alternative, further embodiments may include wherein an interior surface of the port is V-shaped.

In addition to one or more of the features described herein, or as an alternative, further embodiments may include wherein an interior surface of the port is curved.

In addition to one or more of the features described herein, or as an alternative, further embodiments may include wherein the interior port height has a minimum at a center of the port as measured along the Y axis.

In addition to one or more of the features described herein, or as an alternative, further embodiments may include wherein the interior port height has a minimum offset from a center of the port as measured along the Y axis.

In addition to one or more of the features described herein, or as an alternative, further embodiments may include wherein the port has a width, C, measured along the Y axis and the interior port height has a minimum at a distance K from a from a side wall of the port, where K ranges from 0.1×C to 0.9×C.

In addition to one or more of the features described herein, or as an alternative, further embodiments may include wherein K ranges from 0.4×C to 0.6×C.

In addition to one or more of the features described herein, or as an alternative, further embodiments may include wherein interior port height has a maximum of D1and a minimum of D2, wherein D2ranges from 0.1×D1to 0.98×D1.

In addition to one or more of the features described herein, or as an alternative, further embodiments may include wherein D2ranges from 0.65×D1to 0.85×D1.

Technical effects of embodiments of the present disclosure include a heat exchanger including heat exchange tubes using reduced material and satisfying burst strength requirements.

DETAILED DESCRIPTION

Referring now toFIG.1, a vapor compression refrigeration cycle20of a heating, ventilation, air conditioning, and refrigeration (HVAC&R) system is schematically illustrated. Exemplary HVAC&R systems include, but are not limited to, residential, split, packaged, chiller, rooftop, supermarket, and transport HVAC&R systems, for example. A refrigerant is configured to circulate through the vapor compression cycle20such that the refrigerant absorbs heat when evaporated at a low temperature and pressure and releases heat when condensed at a higher temperature and pressure.

Within this vapor compression refrigeration cycle20, the refrigerant flows in a clockwise direction as indicated by the arrows. The compressor22receives refrigerant vapor from the heat exchanger24(e.g., a heat absorption heat exchanger or evaporator) and compresses the refrigerant to a higher temperature and pressure, with the relatively hot vapor then passing to heat exchanger26(e.g., a heat rejection heat exchanger or gas cooler/condenser) where the refrigerant is cooled by a heat exchange relationship with a cooling medium (not shown) such as air. The refrigerant then passes from the heat exchanger26to an expansion device28, wherein the refrigerant experiences a pressure drop and phase change prior to passage to the heat exchanger24. The refrigerant then passes to the heat exchanger24where the refrigerant increases enthalpy through heat exchange relationship with a heating medium (not shown) such as air. The refrigerant then returns to the compressor22where the cycle is repeated.

Referring now toFIG.2, an example heat exchanger30is shown. Heat exchanger30may serve as heat exchanger24and/or heat exchanger26ofFIG.1. The heat exchanger30includes at least a first manifold or header32, a second manifold or header34spaced apart from the first manifold32, and a plurality of heat exchange tubes36extending in a spaced, parallel relationship between and connecting the first manifold32and the second manifold34. In the illustrated, non-limiting embodiments, the first header32and the second header34are oriented generally along a first direction and the heat exchange tubes36extend generally along a second direction between the two headers32,34. The heat exchange tubes36extend between the first and second manifolds32,34, having a length along a first, longitudinal axis, X. A width of the heat exchange tubes36is measured along a second, lateral axis, Y. A height of the heat exchange tube tubes36is measured along a third axis, Z. Axes X, Y and Z are perpendicular to each other.

Referring now toFIG.3, a cross-sectional view of an embodiment of heat exchange tubes36is illustrated. The heat exchange tubes36include a flattened, microchannel heat exchange tube having a first nose40, a second nose42, a first outer surface44and a second outer surface46. The first nose40and the second nose42are aligned on the Y axis. In the example ofFIG.3, the first nose40of the heat exchange tube36is upstream of its respective second nose42with respect to airflow, A, passing through the heat exchanger30and flowing across the heat exchange tubes36. An interior of the heat exchange tube36includes a plurality of discrete ports48that extend over a length of the heat exchange tube36from an inlet end to an outlet end and establish fluid communication between the first and second manifolds32,34. The heat exchange tube36including discrete ports48may be formed using known techniques and materials, including but not limited to, extruding or folding.

A plurality of fins50are located between the heat exchange tubes36and form a metallurgical bond with tube40surface. In some embodiments, the fins50are formed from a continuous strip of fin material folded in a ribbon-like serpentine fashion thereby providing a plurality of closely spaced fins50that extend generally orthogonally to the heat exchange tubes36. Thermal energy exchange between one or more fluids within the heat exchange tubes36and an air flow, A, occurs through the outside of outer surfaces44,46of the heat exchange tubes36collectively forming a primary heat exchange surface, and also through thermal energy exchange with the fins50, which defines a secondary heat exchange surface.

FIG.4is a cross-sectional view of a heat exchange tube60in an example embodiment. The cross-sectional view ofFIG.4depicts the heat exchange tube60in the Y-Z plane. The heat exchange tube60includes the first nose40, the second nose42, the first outer surface44and the second outer surface46, as shown inFIG.3. The ports internal to the heat exchange tube60include end ports62that are immediately adjacent to the first nose40and the second nose42, respectively. Ports located between the end ports62are referenced as interior ports64. The interior ports64are separated along the Y axis by webs66.FIG.4identifies various dimensional references used herein.

The first nose40and/or the second nose42may be any shape, such as semicircular or flat. The nose thickness, F, of one or both of the first nose40and the second nose42may be lower, higher or equal to web thickness, G, of webs66. One or both of the end ports62have a generally non-circular, polygonal shape (e.g., rectangular, square). An interior wall of the end port62immediately adjacent to the adjacent nose40/42has a curvature of zero. The non-circular shape of one or both of the end ports62helps reduce peak stresses on the heat exchange tube60when subjected to an internal pressure during operation.

In an example embodiment, one or both of the end ports62comprises a four-sided polygon with or without rounded corners. Each side of the end port62is a straight line with zero curvature. A radius, R2, at one or more interior corners of the end port62may be less than 20% of the port minor dimension (e.g., the end port width along the Y axis shown inFIG.4).

All the ports, both end ports62and interior ports64, have an aspect ratio defined as width (along the Y axis) divided by height (along the Z axis). The aspect ratio of one or both of the end ports62may be smaller, equal or greater than an aspect ratio of one or more interior ports64. In an example embodiment, the aspect ratio of the one or both of the end ports62ranges from 0.1 and 10.

FIG.5is a cross-sectional view of a heat exchange tube70in an example embodiment. The cross-sectional view ofFIG.5depicts the heat exchange tube70in the Y-Z plane. The heat exchange tube70includes the first nose40, the second nose42, the first outer surface44and the second outer surface46. The ports internal to the heat exchange tube70include end ports72that are immediately adjacent to the first nose40and the second nose42, respectively. Ports located between the end ports72include as first interior ports74and second interior ports76. The end ports72, first interior ports74and second interior ports76are separated along the Y axis by webs66. The first interior ports74may be immediately adjacent to the end ports72.FIG.5identifies various dimensional references used herein.

In heat exchange tube70, one or both of the end ports72have a rounded interior wall facing the first nose40and the second nose42, respectively. The first interior ports74have differing wall thickness (measured along the Z axis) than the second interior ports76. As shown inFIG.5, two first interior ports74have different wall thickness, B2, as compared to the end ports72and the second interior ports76. In one embodiment, the wall thickness (B2) of the first interior ports74is greater than a wall thickness (B1) of the end ports72and the second interior ports76. InFIG.5, both the wall thicknesses (B2) from the inside surface of the first interior port74to the first outer surface44and the inside surface of first interior port74to the second outer surface46is greater than the wall thickness (B1) of the end ports72and the second interior ports76. It is understood that only one of the wall thicknesses (B2) from the inside surface of the first interior port74to the first outer surface44and the inside surface of the first interior port74to the second outer surface46may be greater than the wall thickness (B1) of the end ports72and the second interior ports76.

Referring toFIG.5, D2=E−2*B2and D1=E−2*B1, where D2is a height of a first interior port74measured along the Z axis, D1is a height of a second interior port76measured along the Z axis, E is a height of the heat exchange tube70along the Z axis, B2is a wall thickness of the first interior port74and B1is a wall thickness of the second interior port76. In example embodiments, D2is less than D1, which reduces the maximum principal stress on the heat exchange tube70when subjected to an internal working pressure.

A ratio of B2/B1may range from 1.01 to an upper limit of E/(2B1). In one example embodiment, the ratio of B2/B1ranges from 1.1 to 1.5.

An aspect ratio (AR) of the first interior ports74may be different than an aspect ratio of the second interior ports76. In one embodiment, the aspect ratio of one or both of the first interior ports74is greater than the aspect ratio of the end ports72and the aspect ratio of the second interior ports76. Also, the aspect ratio of one or both of the end ports72is less than that of the second interior ports76. The aspect ratio of the first interior ports74is higher than that of the second interior ports76. This may be summarized as ARend-port 72<ARint-port 76<ARint-port 74.

FIG.6is a cross-sectional view of a heat exchange tube80in an example embodiment. The cross-sectional view ofFIG.6depicts the heat exchange tube80in the Y-Z plane. Heat exchange tube80is similar to heat exchange tube70ofFIG.5, with the difference being that more of the interior ports are first interior ports74. As shown inFIG.6, the first interior ports74, having a greater wall thickness along the Z axis, are located not only adjacent to the end ports72, but also in the interior of the heat exchange tube80. InFIG.6, a first interior port74is positioned after every two second interior ports76. It is understood that the placement of the first interior ports74relative to the second interior ports76may be varied. This pattern of a first interior port74followed by two second interior ports76further reduces peak stresses on the heat exchange tube80.

FIG.7is a cross-sectional view of a heat exchange tube90in an example embodiment. The cross-sectional view ofFIG.7depicts the heat exchange tube90in the Y-Z plane.FIG.7combines elements ofFIG.4andFIG.6. The end ports62have a generally non-circular, polygonal shape (e.g., rectangular, square) as described with reference toFIG.4. The heat exchange tube90includes first interior ports74interspersed with the second interior ports76as described with reference toFIG.6.

The dimensions of the embodiments ofFIGS.4-7may follow certain relationships with respect to each other, are presented in Table 1 below. The dimensions are normalized with respect to dimension E, the height of the heat exchange tube along the Z axis.

FIG.8is a cross-sectional view of a heat exchange tube100in an example embodiment. The cross-sectional view ofFIG.8depicts the heat exchange tube100in the Y-Z plane. In heat exchange tube100, one or both of the end ports72have a rounded interior wall facing the first nose40and the second nose42, respectively, as described above with reference toFIG.5. The interior ports84have a different construction than the ports inFIGS.4-7. The interior ports84are positioned along the Y-axis between the end ports72. The interior ports84include at least one wall having a wall thickness that varies over a width of the interior port84. The varying wall thickness, B, creates a narrowed passage or throat at a distance, K, from an interior wall of the interior port84measured along the Y axis. An interior port height (variable D) ranges from a minimum D2to a maximum D1. The interior port84height varies from the maximum D1, to the minimum D2and back to the maximum D1, along the widthwise direction of the interior port84(i.e., along the Y axis). In the embodiment shown inFIG.8, the interior surface of the interior port84is V-shaped or chevroned, such that the interior port84height decreases linearly to a minimum, D2, and then increases linearly to a maximum, D1, as measured along the widthwise direction of the interior port84(i.e., along the Y axis). The interior surface of the interior port84may follow other contours, such as an arc.

The interior ports84may have a symmetric or asymmetric throat. In other words, the minimum height, D2, in the interior of interior port84does not need to be in the center of the interior port84(e.g., dimension D2is not at middle of dimension “C” i.e., K≠C/2). The dimensions ofFIG.8may follow the following relationships.

K=0.1×C to 0.9×C (example range is 0.4×C to 0.6×C)

The dimensions of the embodiments ofFIG.8may follow certain relationships with respect to each other, are presented in Table 2 below. The majority of the dimensions are normalized with respect to dimension E, the height of the heat exchange tube along the Z axis. Dimension D2is represented as a fraction of D1, and not normalized by dimension E. Dimension K is represented as a fraction of C, and not normalized by dimension E.

FIG.9depicts pressure forces on walls of the interior port84in an example embodiment. Due to the V-shaped interior surface of the interior port84, horizontal components of the resolved pressure forces (i.e., forces along the Y axis) on either side of the V-shaped walls cancel each other. As a result, only the vertical components of the internal pressure forces are relevant for generating hoop stresses in the port walls. The vertical component being lower than the original pressure forces, it results in lower stresses in the tube.

FIG.10is a cross-sectional view of a heat exchange tube110in an example embodiment. The cross-sectional view ofFIG.10depicts the heat exchange tube110in the Y-Z plane. In heat exchange tube110, one or both of the end ports62have a generally non-circular, polygonal shape (e.g., rectangular, square) as described above with reference toFIG.4. The interior ports84have the same construction as described with reference toFIG.8. The dimensions of the embodiments ofFIG.10may follow certain relationships with respect to each other, are presented in Table 2 above.

Embodiments disclosed herein provide heat exchange tubes using less material than existing designs while will still meeting burst strength requirements.

Dimensions used in this application are intended to include the recited dimension and normal variances due to manufacturing tolerances, measurement tolerances, etc.