A tube and fin heat exchanger includes a plurality of heat exchange tubes configured for flowing a refrigerant therethrough, a plurality of fins positioned such that the plurality of heat exchange tubes pass through a plurality of tube openings in the plurality of fins, and a plurality of vortex generators extending from a fin surface of the plurality of fins. The plurality of vortex generators are arranged to define nozzle like passages at the heat exchange tubes.

BACKGROUND

Exemplary embodiments pertain to the art of heating, ventilation, air conditioning and refrigeration (HVAC&R) systems. More particularly, the present disclosure relates to configurations of tube and fin heat exchangers for HVAC&R systems.

Currently, many HVAC&R systems utilize round-tube plate-fin (RTPF) heat exchangers in their evaporator sections. Due to frosting and other design considerations, these heat exchangers typically utilize rudimentary fin designs without enhancements to improve thermal energy exchange performance and efficiency, and thus need large fin surface areas to meet the performance requirements.

In general, such evaporators need large flow depths to manage exit air temperature and are overtly large, are excessively heavy and higher cost. Most common fin enhancement strategies requiring surface interruptions such as lances and louver geometries are rendered ineffective under frosting conditions due to blockage.

BRIEF DESCRIPTION

In one embodiment, a tube and fin heat exchanger includes a plurality of heat exchange tubes configured for flowing a refrigerant therethrough, a plurality of fins positioned such that the plurality of heat exchange tubes pass through a plurality of tube openings in the plurality of fins, and a plurality of vortex generators extending from a fin surface of the plurality of fins. The plurality of vortex generators are arranged to define nozzle like passages at the heat exchange tubes.

Additionally or alternatively, in this or other embodiments one or more vortex generators of the plurality of vortex generators are one of triangular or rectangular in shape.

Additionally or alternatively, in this or other embodiments the plurality of vortex generators are positioned at a nonzero angle of attack relative to a general direction of an airflow across the heat exchanger.

Additionally or alternatively, in this or other embodiments the angle of attack is between 5 degrees and 70 degrees.

Additionally or alternatively, in this or other embodiments a ratio of a vortex generator height from the fin surface to a span between adjacent fins of the plurality of fins is between 0.01 and 1.

Additionally or alternatively, in this or other embodiments the vortex generator has an aspect ratio of streamwise length to height from the fin surface greater than 1.

Additionally or alternatively, in this or other embodiments an upstream most end of the vortex generator is upstream from an associated tube of the plurality of heat exchange tubes.

Additionally or alternatively, in this or other embodiments the plurality of heat exchange tubes are arranged in a plurality of streamwise-extending rows.

Additionally or alternatively, in this or other embodiments the vortex generators are positioned at alternating heat exchange tubes of each streamwise-extending row.

Additionally or alternatively, in this or other embodiments the vortex generators are positioned at only an upstreammost heat exchange tube of a streamwise-extending row of the plurality of streamwise-extending rows.

Additionally or alternatively, in this or other embodiments the heat exchanger is an evaporator.

In another embodiment, a heating, ventilation, air conditioning and refrigeration (HVAC&R) system includes a compressor, a condenser fluidly connected to the compressor, and an evaporator fluidly connected to the compressor and the condenser. One or more of the evaporator or the condenser are configured as a tube and fin heat exchanger and include a plurality of heat exchange tubes configured for flowing a refrigerant therethrough, a plurality of fins located such that the plurality of heat exchange tubes pass through a plurality of tube openings in the plurality of fins, and a plurality of vortex generators extending from a fin surface of the plurality of fins. The plurality of vortex generators are arranged to define nozzle like passages at the heat exchange tubes.

Additionally or alternatively, in this or other embodiments one or more vortex generators of the plurality of vortex generators are one of triangular or rectangular in shape.

Additionally or alternatively, in this or other embodiments the plurality of vortex generators are positioned at a nonzero angle of attack relative to a general direction of an airflow across the tube and fin heat exchanger.

Additionally or alternatively, in this or other embodiments the angle of attack is between 5 degrees and 70 degrees.

Additionally or alternatively, in this or other embodiments a ratio of a vortex generator height from the fin surface to a span between adjacent fins of the plurality of fins is between 0.01 and 1.

Additionally or alternatively, in this or other embodiments the vortex generator has an aspect ratio of streamwise length to height from the fin surface greater than 1.

Additionally or alternatively, in this or other embodiments an upstream most end of the vortex generator is upstream from an associated tube of the plurality of heat exchange tubes.

Additionally or alternatively, in this or other embodiments the plurality of heat exchange tubes are arranged in a plurality of streamwise-extending rows.

Additionally or alternatively, in this or other embodiments vortex generators are located at alternating heat exchange tubes of each streamwise-extending row.

DETAILED DESCRIPTION

Referring now toFIG.1, a vapor compression refrigerant cycle20of a heating, ventilation, air conditioning, and refrigeration (HVAC&R) system is schematically illustrated. Exemplary HVAC&R systems include, but are not limited to, split, packaged, chiller, rooftop, supermarket, and transport HVAC&R systems, for example. A refrigerant R is configured to circulate through the vapor compression cycle20such that the refrigerant R 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 refrigerant cycle20, the refrigerant flows in a counterclockwise direction as indicated by the arrow. The compressor22receives refrigerant vapor from the evaporator24and compresses it to a higher temperature and pressure, with the relatively hot vapor then passing to the condenser26where it is cooled and condensed to a liquid state by a heat exchange relationship with a cooling medium (not shown) such as air. The liquid refrigerant R then passes from the condenser26to an expansion device28, wherein the refrigerant R is expanded to a low temperature two-phase liquid/vapor state as it passes to the evaporator24. At the evaporator24a flow or relatively warm return air30is urged across the evaporator24by, for example, an evaporator fan32. The return air30is cooled via thermal energy exchange with the refrigerant R flowing through the evaporator24, and is flowed to a conditioned space34, such as a room or refrigerated case, as supply air36. The low pressure refrigerant vapor then returns to the compressor22where the cycle is repeated.

Referring now toFIG.2, an example of an evaporator24configured for use in the vapor compression cycle20is illustrated in more detail. While the present disclosure utilizes evaporator24as the basis of the description herein, one skilled in the art will appreciate that the present disclosure may also be applied to condenser26or other heat exchangers in other systems. The exemplary evaporator24is a round tube plate fin heat exchanger and includes a plurality of heat exchange tubes42. The plurality of heat exchange tubes42extend through tube openings44(shown best inFIG.3) in a plurality of fins46located between the first manifold38and the second manifold40. In some embodiments, each fin of the plurality of fins46is positioned orthogonal to the plurality of heat exchange tubes42. Further, in some embodiments such as shown inFIG.2, the plurality of heat exchange tubes42are arranged in a multi-pass configuration, passing through the plurality of fins46more than once. It is to be appreciated that the embodiment ofFIG.2is merely exemplary and that other heat exchanger configurations are within the scope of the present disclosure.

Referring now toFIG.3, shown is an example of a fin46configuration. The plurality of heat exchange tubes42, arranged in a plurality of streamwise rows, pass through the fin openings44. One or more vortex generators48extend from a fin surface50and are oriented to form a nozzle-like passage52between the vortex generator48and the heat exchange tube42. In some embodiments, the vortex generators48extend orthogonally from the fin surface50. The position of the vortex generator48relative to the heat exchange tube42causes the return air30directed across the evaporator24to accelerate along the passage52, resulting in a delayed flow separation in a tube wake region54downstream of the heat exchange tube42relative to the direction of airflow30. The accelerated flow along the passage52also cause to impinge on the downstream heat exchange tube42tube with greater velocity resulting in enhanced convective heat transfer on the heat exchange tube42surface. The vortex generators48create streamwise longitudinal vortices that modify the boundary layer at the heat exchange tube42such that an air-side heat transfer coefficient is increased. Furthermore, the vortices cause enhanced mixing of the return airflow30and promote more uniform distribution of frost over the evaporator24surfaces.

Referring toFIGS.4A-4D, example shapes of vortex generators48are illustrated. InFIG.4A, a delta wing shaped vortex generator48is shown, while inFIG.4Ba rectangular wing shaped vortex generator48is illustrated. In the configurations ofFIGS.4A and4B, the vortex generator48protrudes from the fin46at an upstream end56of the vortex generator48, while a downstream end58of the vortex generator48is fixed to the fin46. Illustrated inFIGS.4C and4Dare a delta winglet vortex generator48and a rectangular winglet vortex generator48, respectively. In the configurations ofFIGS.4C and4Da first lateral side60of the vortex generator48is fixed to the fin46, while a second lateral side62of the vortex generator48protrudes from the fin surface50. The vortex generators48may be formed by, for example, a punching operation of the fin46, or alternatively may be secured to the fin46by brazing or adhesive application or the like.

Shown inFIG.5is a plan view of an exemplary vortex generator48arrangement at a heat exchange tube42. The vortex generators48are arranged with a non-zero angle of attack64, which is an angle of the vortex generator48relative to the flow direction of return airflow30. In some embodiments, the angle of attack64is between 5 degrees and 70 degrees. The angle of attack64creates the nozzle-like passage52between the vortex generator48and the heat exchange tube42. While in some embodiments, the angle of attack64may be equal for all of the vortex generators48of the evaporator24, in other embodiments the angle of attack64may vary depending on characteristics of the evaporator24.

Referring now to the side view ofFIG.6, adjacent fins46are spaced by a fin span66, which in some embodiments is between 1 millimeter and 12.7 millimeters. Further, the vortex generator48has a vortex generator height68and in some embodiments a ratio of the vortex generator height68to the fin span66is between 0.01 and 1. The vortex generator48further has a streamwise length70, such that an aspect ratio of streamwise length70to vortex generator height68is greater than 1.

Referring again toFIG.3, in some embodiments the upstream end56of the vortex generator48is located upstream of the heat exchange tube42. In other embodiments, other arrangements may be utilized. For example, in the embodiment ofFIG.7, the upstream end56is located downstream of the heat exchange tube42. IT is to be appreciated, however, that these arrangements are merely exemplary.

The embodiments ofFIGS.3and7illustrate configurations having two vortex generators48at each heat exchange tube42so that a nozzle like passage52is defined at each heat exchange tube42. In other embodiments, as illustrated inFIGS.8-10, other such arrangements are utilized. For example, in the embodiment ofFIG.8, the vortex generators48are located at only an upstream-most heat exchange tube42of a streamwise row of heat exchange tubes42. As shown inFIG.9, in another embodiment pairs vortex generators48are located such that heat exchange tubes42having vortex generators48alternate along a streamwise row with heat exchange tubes42not accompanied by vortex generators48. Another configuration is illustrated inFIG.10, where each heat exchange tube48is accompanied by a single vortex generator48, with the location of the vortex generators48alternating lateral sides of the heat exchange tubes42along the streamwise row.

The configurations of the present disclosure improve thermal energy performance of the evaporator24, especially in frosting configurations. The performance improvement includes a low pressure drop penalty, in a configuration that is easily and cost-efficiently manufactured. Additionally, the overall size of the heat exchanger may be reduced for the same performance as a heat exchanger without vortex generators48.