Embodiments of the present disclosure relate to the art of heat exchangers, and more particularly, to a microchannel heat exchanger having folded heat exchange tubes.
Heat exchange tubes typically used in existing microchannel heat exchangers are extruded. Because the weight and the cost of fabricated heat exchange tubes are reduced compared to extruded heat exchange tubes, fabricated heat exchange tubes are becoming more common in heating, ventilation, and air conditioning (HVAC) applications. However, when fabricated heat exchange tubes are used in place of extruded heat exchange tubes, in certain circumstances, the oil entrained within the refrigerant may accumulate within the heat exchange tubes, thereby reducing the efficiency of the system.
According to an embodiment, a heat exchange tube segment for use in a heat exchange includes a fabricated tube body having an upper surface, a lower surface, a leading edge, a trailing edge, and a plurality of fluidly distinct flow channels formed therein. The fabricated tube body has a length, width, height, and a total tube cross-sectional area measured between the upper surface, the lower surface, the leading edge, and the trailing edge. A ratio of the width to the height of the fabricated tube body is between about 10 and 20, and a ratio of the width to a number of the plurality of fluidly distinct flow channels is between 1 and 2.5. Each of the plurality of fluidly distinct flow channels forms an open area in a cross-section of the fabricated tube body, and a ratio of the open area to the total tube cross-sectional area is between 0.3 and 0.44.
In addition to one or more of the features described herein, or as an alternative, further embodiments the ratio of the width to the number of the plurality of fluidly distinct flow channels is between 1.3 and 2.5.
In addition to one or more of the features described herein, or as an alternative, further embodiments the ratio of the open area to the total tube cross-sectional area is between 0.36 and 0.40.
In addition to one or more of the features described herein, or as an alternative, further embodiments the plurality of fluidly distinct flow channels are configured to receive a refrigerant selected from methylene fluoride and difluoromethylene.
In addition to one or more of the features described herein, or as an alternative, further embodiments the fabricated tube body includes a single piece of material folded to form the upper surface, the lower surface, the leading edge, the trailing edge, and the plurality of fluidly distinct flow channels.
According to an embodiment, a heat exchanger includes a first manifold, aa second manifold, and a plurality of heat exchange tube segments extending between and fluidly coupling the first manifold and the second manifold. At least one the plurality of heat exchange tube segments further includes a fabricated tube body having an upper surface, a lower surface, a leading edge, a trailing edge, and a plurality of fluidly distinct flow channels formed therein. The fabricated tube body has a length measured parallel to the plurality of fluidly distinct flow channels, a width measured between the leading edge and the trailing edge, a height measured between the upper surface and the lower surface, and a total tube cross-sectional area measured between the upper surface, the lower surface, the leading edge, and the trailing edge. A ratio of the width to the height of the fabricated tube body is between about 10 and 20, a ratio of the width to a number of the plurality of fluidly distinct flow channels is between 1 and 2.5. Each of the plurality of fluidly distinct flow channels forms an open area in a cross-section of the fabricated tube body and a ratio of the open area to the total tube cross-sectional area is between 0.3 and 0.44.
In addition to one or more of the features described herein, or as an alternative, further embodiments the heat exchanger has a multi-pass configuration.
In addition to one or more of the features described herein, or as an alternative, further embodiments the heat exchanger has a first pass and a second pass, and a number of heat exchange tube segments associated with the first pass is greater than a number of heat exchange tube segments associated with the second pass.
In addition to one or more of the features described herein, or as an alternative, further embodiments a ratio of the number of heat exchange tube segments associated with the first pass to the number of heat exchange tube segments associated with the second pass is between 1 and 3.
In addition to one or more of the features described herein, or as an alternative, further embodiments a ratio of the number of heat exchange tube segments associated with the first pass to the number of heat exchange tube segments associated with the second pass is between 1.2 and 3.
In addition to one or more of the features described herein, or as an alternative, further embodiments the ratio of the width to the number of the plurality of fluidly distinct flow channels is between 1.3 and 2.5.
In addition to one or more of the features described herein, or as an alternative, further embodiments the ratio of the open area to the total tube cross-sectional area is between 0.36 and 0.40.
In addition to one or more of the features described herein, or as an alternative, further embodiments the plurality of fluidly distinct flow channels are configured to receive a refrigerant, the refrigerant being one of methylene fluoride and difluoromethylene.
In addition to one or more of the features described herein, or as an alternative, further embodiments the fabricated tube body comprises a single piece of material folded to form the upper surface, the lower surface, the leading edge, the trailing edge, and the plurality of fluidly distinct flow channels.
In addition to one or more of the features described herein, or as an alternative, further embodiments the heat exchanger is a condenser in a chiller.
The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:
A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.
Each coil unit 22 additionally includes a fan assembly 28 having at least one fan configured to move a flow of ambient air across the adjacent heat exchanger assembly 26. A plurality of compressors 30, such as positioned within the frame 24 of one or more of the coil units 22, are fluidly coupled to the heat exchanger assemblies 26 and are configured to pump refrigerant through a vapor compression cycle. The compressors 30 may be arranged in series, or alternatively, may be arranged in parallel relative to the flow of refrigerant. For example, in the illustrated, non-limiting embodiment, three compressors 30 are illustrated as being fluidly coupled to the heat exchanger assemblies 26 of two coil units 22. However, any number of compressors 30 may be in fluid communication with any number of heat exchanger assemblies 26. The chiller or outdoor unit 20 illustrated and described herein are intended as an example only, and it should be understood that other configurations of the chiller and of the coil units are contemplated herein.
Referring now to
In an embodiment, best shown in
With reference now to
The heat exchange tube segments 46 disclosed herein may further include a plurality of fins 62. In an embodiment, each fin 62 is formed of a single continuous strip of fin material tightly folded in a ribbon-like serpentine fashion thereby providing a plurality of closely spaced fins that extend generally orthogonal to the heat exchange tube segments 46. Typically, the fin density of the closely spaced fins of each continuous folded fin may be about 16 to 25 fins per inch, but higher or lower fin densities may also be used. Heat exchange between the refrigerant flow, R, and air flow, A, occurs through the outside surfaces 54, 56, respectively, of the heat exchange tube segments 46, collectively forming a primary heat exchange surface, and also through the heat exchange surface of the fins 62, which forms the secondary heat exchange surface.
With reference now to
In another embodiment, illustrated in
Alternatively, the heat exchange tube segment 46 may have a two piece design where the flow channels 60 are formed using a corrugation form 68 inserted into an outer shell or sleeve 70 as shown in
In embodiments where a vapor compression cycle includes a plurality of compressors arranged in series relative to the flow of refrigerant, the total number of compressors used to propel the flow through the cycle may vary based on one or more operating conditions, such as the ambient air temperature or the load on the system. Accordingly, a velocity of the refrigerant in instances where all of the compressors are being used to move the refrigerant through the cycle is greater than the velocity of the refrigerant in instances where only one of the plurality of compressors is operational. When the refrigerant at this lower velocity associated with operation of only a portion of the compressors flows through a heat exchanger 40 having fabricated heat exchange tube segments 46, excessive oil mixed with the refrigerant may accumulate within one or more of the flow channels 60 of a heat exchange tube segments 46. Accordingly, one or more parameters of the fabricated heat exchange tube segment may be controlled to minimize the accumulation of oil within the flow channels.
With reference now to
In an embodiment, the ratio of the width W of the heat exchange tube segment 46 to the height H of the heat exchange tube segment 46 is between 10 and 20, and in some embodiments is between 12 and 20, 14 and 20, or 16 and 20. Further, in an embodiment, a ratio of the width W of the heat exchange tube segment 46 to the total number of flow channels 60 formed in the heat exchange tube segment 46 is between 1.3 and 2.5. The ratio of the width W to the total number of flow channels 60 may further be between 1.5 and 2.5, between 1.7 and 2.5, or between 2.0 and 2.5.
Further, a fabricated heat exchange tube segment 46 typically requires less material than an extruded heat exchange tube segment. Because of this, the open area defined by the plurality of fluidly distinct flow channels 60 occupies a greater percentage of the area of the heat exchange tube segment 46. This percentage of the open area may be described as porosity. In an embodiment, a ratio of the cross-sectional area of the open areas of a heat exchange tube segment 46, such as formed by the flow channels 60 for example, to the total tube cross-sectional area of a heat exchange the tube segment 46 is between about 0.30 and 0.44. For example, the ratio of the cross-sectional area of the open areas of the heat exchange tube segment 46 to the total tube cross-sectional area of a heat exchange tube segment 46 may be between about 0.34 and 0.44, between about 0.30 and 0.40, between about 0.36 and 0.44, between about 0.36 and 0.40, such as 0.38 for example.
With continued reference to
By customizing the configuration of the fabricated heat exchange tube segments 46 and the heat exchanger 40, the velocity of the refrigerant R may be improved, thereby mitigating the oil accumulation within the flow channels 60 of the heat exchange tube segments 46. Further, the use of fabricated heat exchange tube segments as described herein provides a low-cost solution relative to an oil separator. It should be appreciated that the heating, ventilation, and air conditioning (HVAC) system described herein may be devoid of an oil separator, in certain instances.
The term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof.
While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.
This application claims the benefit of U.S. provisional patent application Ser. No. 63/274,719, filed Nov. 2, 2021, the entire contents of which are incorporated herein by reference.
Number | Date | Country | |
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63274719 | Nov 2021 | US |