Patent Description:
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.

The following background art has been identified as being useful to understand the invention disclosed herein:.

D1 discloses a heat exchange tube according to the preamble of claim <NUM> and provides a heating, ventilation, air conditioning, and ventilation system comprising multichannel tubes wherein the multichannel tubes are configured to promote flow of refrigerant near to the edge of the tube first contacted by an external fluid.

D2 provides an extruded aluminium flat multi-hole tube comprising a plurality of refrigerant passages. The passages comprise a ridge formed on the upper wall surface.

The present invention provides 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; and wherein the interior port height (D) increases and decreases along the Y axis; characterised in that: an interior surface of the port (<NUM>) is V-shaped or curved and the interior port height has a minimum offset from a center of the port as measured along the Y axis.

Optionally, 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 <NUM>. 1xC to <NUM>.

Optionally, K ranges from <NUM>. 4xC to <NUM>.

Optionally, interior port height has a maximum of D1 and a minimum of D2, wherein D2 ranges from <NUM>. 1xD1 to <NUM>.

Optionally, D2 ranges from <NUM>. 65xD1 to <NUM>.

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

A detailed description of one or more embodiments of the disclosed apparatus are presented herein by way of exemplification and not limitation with reference to the Figures.

Referring now to <FIG>, a vapor compression refrigeration cycle <NUM> of 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 cycle <NUM> such 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 cycle <NUM>, the refrigerant flows in a clockwise direction as indicated by the arrows. The compressor <NUM> receives refrigerant vapor from the heat exchanger <NUM> (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 exchanger <NUM> (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 exchanger <NUM> to an expansion device <NUM>, wherein the refrigerant experiences a pressure drop and phase change prior to passage to the heat exchanger <NUM>. The refrigerant then passes to the heat exchanger <NUM> where the refrigerant increases enthalpy through heat exchange relationship with a heating medium (not shown) such as air. The refrigerant then returns to the compressor <NUM> where the cycle is repeated.

Referring now to <FIG>, an example heat exchanger <NUM> is shown. Heat exchanger <NUM> may serve as heat exchanger <NUM> and/or heat exchanger <NUM> of <FIG>. The heat exchanger <NUM> includes at least a first manifold or header <NUM>, a second manifold or header <NUM> spaced apart from the first manifold <NUM>, and a plurality of heat exchange tubes <NUM> extending in a spaced, parallel relationship between and connecting the first manifold <NUM> and the second manifold <NUM>. In the illustrated, non-limiting embodiments, the first header <NUM> and the second header <NUM> are oriented generally along a first direction and the heat exchange tubes <NUM> extend generally along a second direction between the two headers <NUM>, <NUM>. The heat exchange tubes <NUM> extend between the first and second manifolds <NUM>, <NUM>, having a length along a first, longitudinal axis, X. A width of the heat exchange tubes <NUM> is measured along a second, lateral axis, Y. A height of the heat exchange tube tubes <NUM> is measured along a third axis, Z. Axes X, Y and Z are perpendicular to each other.

Referring now to <FIG>, a cross-sectional view of an embodiment of heat exchange tubes <NUM> is illustrated. The heat exchange tubes <NUM> include a flattened, microchannel heat exchange tube having a first nose <NUM>, a second nose <NUM>, a first outer surface <NUM> and a second outer surface <NUM>. The first nose <NUM> and the second nose <NUM> are aligned on the Y axis. In the example of <FIG>, the first nose <NUM> of the heat exchange tube <NUM> is upstream of its respective second nose <NUM> with respect to airflow, A, passing through the heat exchanger <NUM> and flowing across the heat exchange tubes <NUM>. An interior of the heat exchange tube <NUM> includes a plurality of discrete ports <NUM> that extend over a length of the heat exchange tube <NUM> from an inlet end to an outlet end and establish fluid communication between the first and second manifolds <NUM>, <NUM>. The heat exchange tube <NUM> including discrete ports <NUM> may be formed using known techniques and materials, including but not limited to, extruding or folding.

A plurality of fins <NUM> are located between the heat exchange tubes <NUM> and form a metallurgical bond with tube <NUM> surface. In some embodiments, the fins <NUM> are formed from a continuous strip of fin material folded in a ribbon-like serpentine fashion thereby providing a plurality of closely spaced fins <NUM> that extend generally orthogonally to the heat exchange tubes <NUM>. Thermal energy exchange between one or more fluids within the heat exchange tubes <NUM> and an air flow, A, occurs through the outside of outer surfaces <NUM>, <NUM> of the heat exchange tubes <NUM> collectively forming a primary heat exchange surface, and also through thermal energy exchange with the fins <NUM>, which defines a secondary heat exchange surface.

<FIG> is a cross-sectional view of a heat exchange tube <NUM> in an example embodiment. The cross-sectional view of <FIG> depicts the heat exchange tube <NUM> in the Y-Z plane. The heat exchange tube <NUM> includes the first nose <NUM>, the second nose <NUM>, the first outer surface <NUM> and the second outer surface <NUM>, as shown in <FIG>. The ports internal to the heat exchange tube <NUM> include end ports <NUM> that are immediately adjacent to the first nose <NUM> and the second nose <NUM>, respectively. Ports located between the end ports <NUM> are referenced as interior ports <NUM>. The interior ports <NUM> are separated along the Y axis by webs <NUM>. <FIG> identifies various dimensional references used herein.

The first nose <NUM> and/or the second nose <NUM> may be any shape, such as semicircular or flat. The nose thickness, F, of one or both of the first nose <NUM> and the second nose <NUM> may be lower, higher or equal to web thickness, G, of webs <NUM>. One or both of the end ports <NUM> have a generally non-circular, polygonal shape (e.g., rectangular, square). An interior wall of the end port <NUM> immediately adjacent to the adjacent nose <NUM>/<NUM> has a curvature of zero. The non-circular shape of one or both of the end ports <NUM> helps reduce peak stresses on the heat exchange tube <NUM> when subjected to an internal pressure during operation.

In an example embodiment, one or both of the end ports <NUM> comprises a foursided polygon with or without rounded corners. Each side of the end port <NUM> is a straight line with zero curvature. A radius, R2, at one or more interior corners of the end port <NUM> may be less than <NUM>% of the port minor dimension (e.g., the end port width along the Y axis shown in <FIG>).

All the ports, both end ports <NUM> and interior ports <NUM>, 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 ports <NUM> may be smaller, equal or greater than an aspect ratio of one or more interior ports <NUM>. In an example embodiment, the aspect ratio of the one or both of the end ports <NUM> ranges from <NUM> and <NUM>.

<FIG> is a cross-sectional view of a heat exchange tube <NUM> in an example embodiment. The cross-sectional view of <FIG> depicts the heat exchange tube <NUM> in the Y-Z plane. The heat exchange tube <NUM> includes the first nose <NUM>, the second nose <NUM>, the first outer surface <NUM> and the second outer surface <NUM>. The ports internal to the heat exchange tube <NUM> include end ports <NUM> that are immediately adjacent to the first nose <NUM> and the second nose <NUM>, respectively. Ports located between the end ports <NUM> include as first interior ports <NUM> and second interior ports <NUM>. The end ports <NUM>, first interior ports <NUM> and second interior ports <NUM> are separated along the Y axis by webs <NUM>. The first interior ports <NUM> may be immediately adjacent to the end ports <NUM>. <FIG> identifies various dimensional references used herein.

In heat exchange tube <NUM>, one or both of the end ports <NUM> have a rounded interior wall facing the first nose <NUM> and the second nose <NUM>, respectively. The first interior ports <NUM> have differing wall thickness (measured along the Z axis) than the second interior ports <NUM>. As shown in <FIG>, two first interior ports <NUM> have different wall thickness, B2, as compared to the end ports <NUM> and the second interior ports <NUM>. In one embodiment, the wall thickness (B2) of the first interior ports <NUM> is greater than a wall thickness (B1) of the end ports <NUM> and the second interior ports <NUM>. In <FIG>, both the wall thicknesses (B2) from the inside surface of the first interior port <NUM> to the first outer surface <NUM> and the inside surface of first interior port <NUM> to the second outer surface <NUM> is greater than the wall thickness (B1) of the end ports <NUM> and the second interior ports <NUM>. It is understood that only one of the wall thicknesses (B2) from the inside surface of the first interior port <NUM> to the first outer surface <NUM> and the inside surface of the first interior port <NUM> to the second outer surface <NUM> may be greater than the wall thickness (B1) of the end ports <NUM> and the second interior ports <NUM>.

Referring to <FIG>, D2=E-<NUM>*B2 and D1=E-<NUM>*B1, where D2 is a height of a first interior port <NUM> measured along the Z axis, D1 is a height of a second interior port <NUM> measured along the Z axis, E is a height of the heat exchange tube <NUM> along the Z axis, B2 is a wall thickness of the first interior port <NUM> and B1 is a wall thickness of the second interior port <NUM>. In example embodiments, D2 is less than D1, which reduces the maximum principal stress on the heat exchange tube <NUM> when subjected to an internal working pressure.

A ratio of B2/B1 may range from <NUM> to an upper limit of E/(2B1). In one example embodiment, the ratio of B2/B1ranges from <NUM> to <NUM>.

An aspect ratio (AR) of the first interior ports <NUM> may be different than an aspect ratio of the second interior ports <NUM>. In one embodiment, the aspect ratio of one or both of the first interior ports <NUM> is greater than the aspect ratio of the end ports <NUM> and the aspect ratio of the second interior ports <NUM>. Also, the aspect ratio of one or both of the end ports <NUM> is less than that of the second interior ports <NUM>. The aspect ratio of the first interior ports <NUM> is higher than that of the second interior ports <NUM>. This may be summarized as ARend-port <NUM> < ARint-port <NUM> < ARint-port <NUM>.

<FIG> is a cross-sectional view of a heat exchange tube <NUM> in an example embodiment. The cross-sectional view of <FIG> depicts the heat exchange tube <NUM> in the Y-Z plane. Heat exchange tube <NUM> is similar to heat exchange tube <NUM> of <FIG>, with the difference being that more of the interior ports are first interior ports <NUM>. As shown in <FIG>, the first interior ports <NUM>, having a greater wall thickness along the Z axis, are located not only adjacent to the end ports <NUM>, but also in the interior of the heat exchange tube <NUM>. In <FIG>, a first interior port <NUM> is positioned after every two second interior ports <NUM>. It is understood that the placement of the first interior ports <NUM> relative to the second interior ports <NUM> may be varied. This pattern of a first interior port <NUM> followed by two second interior ports <NUM> further reduces peak stresses on the heat exchange tube <NUM>.

<FIG> is a cross-sectional view of a heat exchange tube <NUM> in an example embodiment. The cross-sectional view of <FIG> depicts the heat exchange tube <NUM> in the Y-Z plane. <FIG> combines elements of <FIG> and <FIG>. The end ports <NUM> have a generally non-circular, polygonal shape (e.g., rectangular, square) as described with reference to <FIG>. The heat exchange tube <NUM> includes first interior ports <NUM> interspersed with the second interior ports <NUM> as described with reference to <FIG>.

The dimensions of the embodiments of <FIG> may follow certain relationships with respect to each other, are presented in Table <NUM> below. The dimensions are normalized with respect to dimension E, the height of the heat exchange tube along the Z axis.

<FIG> is a cross-sectional view of a heat exchange tube <NUM> in an example according to the invention. The cross-sectional view of <FIG> depicts the heat exchange tube <NUM> in the Y-Z plane. In heat exchange tube <NUM>, one or both of the end ports <NUM> have a rounded interior wall facing the first nose <NUM> and the second nose <NUM>, respectively, as described above with reference to <FIG>. The interior ports <NUM> have a different construction than the ports in <FIG>. The interior ports <NUM> are positioned along the Y-axis between the end ports <NUM>. The interior ports <NUM> include at least one wall having a wall thickness that varies over a width of the interior port <NUM>. The varying wall thickness, B, creates a narrowed passage or throat at a distance, K, from an interior wall of the interior port <NUM> measured along the Y axis. An interior port height (variable D) ranges from a minimum D2 to a maximum D1. The interior port <NUM> height varies from the maximum D1, to the minimum D2 and back to the maximum D1, along the widthwise direction of the interior port <NUM> (i.e., along the Y axis). In the embodiment shown in <FIG>, the interior surface of the interior port <NUM> is V-shaped or chevroned, such that the interior port <NUM> height decreases linearly to a minimum, D2, and then increases linearly to a maximum, D1, as measured along the widthwise direction of the interior port <NUM> (i.e., along the Y axis). The interior surface of the interior port <NUM> may follow other contours, such as an arc.

The interior ports <NUM> may have a symmetric or asymmetric throat. In other words, the minimum height, D2, in the interior of interior port <NUM> does not need to be in the center of the interior port <NUM> (e.g., dimension D2 is not at middle of dimension "C" i.e., K≠C/<NUM>). The dimensions of <FIG> may follow the following relationships.

The dimensions of the embodiments of <FIG> may follow certain relationships with respect to each other, are presented in Table <NUM> 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 D2 is 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> depicts pressure forces on walls of the interior port <NUM> in an example embodiment. Due to the V-shaped interior surface of the interior port <NUM>, 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> is a cross-sectional view of a heat exchange tube <NUM> in an example embodiment. The cross-sectional view of <FIG> depicts the heat exchange tube <NUM> in the Y-Z plane. In heat exchange tube <NUM>, one or both of the end ports <NUM> have a generally non-circular, polygonal shape (e.g., rectangular, square) as described above with reference to <FIG>. The interior ports <NUM> have the same construction as described with reference to <FIG>. The dimensions of the embodiments of <FIG> may follow certain relationships with respect to each other, are presented in Table <NUM> 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..

Claim 1:
A heat exchange tube (<NUM>, <NUM>) for use in a heat exchanger, the heat exchange tube (<NUM>, <NUM>) comprising:
a first nose (<NUM>) and a second nose (<NUM>) aligned on a Y axis along a width of the heat exchange tube (<NUM>, <NUM>); and
a port (<NUM>) positioned between the first nose (<NUM>) and the second nose (<NUM>), the port (<NUM>) 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; and
wherein the interior port height (D) increases and decreases along the Y axis;
characterised in that:
an interior surface of the port (<NUM>) is V-shaped or curved and the interior port height has a minimum offset from a center of the port as measured along the Y axis.