WO2008079121A1 - Échangeur de chaleur avec tamis de collecte et de purge de condensats - Google Patents

Échangeur de chaleur avec tamis de collecte et de purge de condensats Download PDF

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Publication number
WO2008079121A1
WO2008079121A1 PCT/US2006/049195 US2006049195W WO2008079121A1 WO 2008079121 A1 WO2008079121 A1 WO 2008079121A1 US 2006049195 W US2006049195 W US 2006049195W WO 2008079121 A1 WO2008079121 A1 WO 2008079121A1
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WO
WIPO (PCT)
Prior art keywords
heat exchanger
recited
condensate
condensate collecting
screen
Prior art date
Application number
PCT/US2006/049195
Other languages
English (en)
Inventor
Michael F. Taras
Alexander Lifson
Original Assignee
Carrier Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Carrier Corporation filed Critical Carrier Corporation
Priority to PCT/US2006/049195 priority Critical patent/WO2008079121A1/fr
Publication of WO2008079121A1 publication Critical patent/WO2008079121A1/fr

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
    • F25D21/00—Defrosting; Preventing frosting; Removing condensed or defrost water
    • F25D21/14—Collecting or removing condensed and defrost water; Drip trays

Definitions

  • This invention relates generally to heat exchangers for cooling air, and more particularly, to direct expansion evaporator heat exchangers of refrigerant vapor compression systems and cooling heat exchangers of air handling equipment.
  • Air conditioners and heat pumps employing refrigerant vapor compression cycles are commonly used for cooling or cooling/heating air supplied to a climate controlled comfort zone within a residence, office building, hospital, school, restaurant or other facility.
  • Refrigerant vapor compression systems are also commonly used for cooling air, or other secondary media such as water or glycol solution, to provide a refrigerated environment for food items and heverage products within display cases, bottle coolers or other similar equipment in supermarkets, convenience stores, groceries, cafeterias, restaurants and other food service establishments.
  • these refrigerant vapor compression systems include a compressor, a condenser, an expansion device, and an evaporator serially connected in refrigerant flow communication.
  • the aforementioned basic refrigerant vapor compression system components are interconnected by refrigerant lines in a closed refrigerant circuit and arranged in accord with the employed vapor compression cycle.
  • the expansion device commonly an expansion valve or a fixed- bore metering device, such as an orifice or a capillary tube, is disposed in the refrigerant line at a location in the refrigerant circuit upstream, with respect to refrigerant flow, of the evaporator and downstream of the condenser.
  • the expansion device operates to expand the liquid refrigerant passing through the refrigerant line, connecting the condenser to the evaporator, to a lower pressure and temperature.
  • the refrigerant vapor compression system may be charged with any of a variety of refrigerants, including, for example, R-12, R-22, R-134a, R-404A, R-410A, R-407C, R717, R744 or other compressible fluid.
  • the evaporator is a parallel tube heat exchanger having a plurality of round heat exchange tubes extending longitudinally in a horizontal direction in parallel, spaced relationship, the heat exchange tubes being interconnected at their respective ends by so-called hairpin return bends to form a serpentine coil within each evaporator circuit.
  • hairpin configurations are used, instead of straight tube arrangements, with the return bends required only on one side of the hairpin-configured heat exchange tubes to form an evaporator serpentine refrigerant circuit.
  • a plurality of serpentine evaporator circuits is employed to flow refrigerant downstream in a parallel manner.
  • each serpentine coil is connected to the refrigerant cycle so as to receive refrigerant flow from the refrigerant cycle and the other end of each serpentine coil (or circuit) is connected to the refrigerant cycle so as to return refrigerant flow to the refrigerant cycle.
  • the upstream receiving end of each serpentine coil is typically connected to a refrigerant cycle through a distributor or an inlet manifold, while the downstream returning end of each serpentine coil is connected to a refrigerant cycle through an outlet manifold.
  • the parallel tube evaporator is a parallel flow heat exchanger (also often called a microchannel or minichannel heat exchanger) having a plurality of flattened heat exchange tubes extending longitudinally in a horizontal direction in parallel, spaced relationship between a pair of spaced headers (or manifolds).
  • the return bends are substituted by intermediate manifolds or manifold chambers, while a number of parallel circuits is defined by a number of parallel heat transfer tubes within each pass.
  • heat transfer fins are commonly positioned between heat transfer tubes for heat transfer enhancement, structural rigidity and heat exchanger design compactness.
  • the heat transfer tubes and fins axe permanently attached to each other, typically, by a mechanical contact, for round tube and plate fin heat exchangers, and by furnace brazing operation, for parallel flow heat exchangers.
  • the heat transfer tubes may have internal heat transfer enhancement elements as well.
  • the collected condensate may be stripped off or blown off the external surfaces of the heat exchange tubes and associated fins and carried downstream the air passage by the momentum of the airflow, potentially creating leakage problems. In some cases, a portion of this entrained condensate may even be carried back into the conditioned space, which increases the humidity of that environment, potentiality adversely impacting the comfort of occupants within the conditioned space.
  • heat exchanger drainage characteristics depend on heat exchanger design and orientation, at certain airflow velocities, condensate blow-off phenomenon can be experienced in a vast majority of operating conditions.
  • evaporator heat exchangers are typically designed to keep the velocity of the airflow through the heat exchanger coil below the level at which condensate would be blown off the external surfaces of the heat exchange tubes and associated fins, even though operation at higher airflow velocities would be desirable to provide a higher recirculation rates of air from the condition space and sufficient penetration and mixing of the conditioned airflow in the conditioned space, as well as for refrigerant system capacity adjustment and supplied air temperature control.
  • cooling heat exchangers of air handling equipment utilizing cold water or glycol solutions to cool and dehumidify air supplied to the conditioned environment, face an identical problem of condensate blow-off, which causes similar undesired consequences.
  • a heat exchanger for cooling a flow of air passing therethrough includes a heat transfer surface including a plurality of refrigerant conveying heat exchange tubes and associated fins, and having a condensate collecting screen disposed downstream of the heat exchanger, with respect to airflow, to capture condensate entrained in the airflow.
  • the condensate collecting screen may comprise a wire mesh screen.
  • the condensate collecting screen may comprise a screen having a honeycomb mesh structure. Condensate flow channels may be formed in the surface of the condensate collecting screen facing upstream, with respect to the airflow.
  • FIG. 1 is a schematic diagram of a refrigerant vapor compression system having an evaporator heat exchanger with a condensate collecting screen;
  • FIG. 2 is a perspective view of a section of an exemplary embodiment of an evaporator heat exchanger including a condensate collecting screen;
  • FIG. 3 is an exploded front view of a section of the condensate collecting screen of the evaporator heat exchanger of FIG. 2;
  • FIG. 4 is a sectioned, elevation view taken along line 4-4 of FIG. 2;
  • FIG. 5 is a side elevation view, partly sectioned, of another exemplary embodiment of the evaporator heat exchanger of FIG. 2.
  • the heat exchanger of the invention will be described herein in use as an evaporator, in connection with a simplified air conditioning cycle refrigerant vapor compression system 100, as depicted schematically in FIG. 1.
  • a simplified air conditioning cycle refrigerant vapor compression system 100 as depicted schematically in FIG. 1.
  • the exemplary refrigerant vapor compression cycle illustrated in FIG. 1 is a simplified air conditioning cycle, it is to be understood that the heat exchanger of the invention may be employed in refrigerant vapor compression systems of various designs, including, without limitation, heat pump cycles, economized cycles, cycles with tandem components such as compressors and heat exchangers, chiller cycles, cycles with reheat and many other cycles including various options and features.
  • the refrigerant vapor compression system 100 includes a compressor
  • the compressor 105 compresses refrigerant from a lower suction pressure to a higher discharge pressure and circulates this hot, high pressure refrigerant vapor through discharge refrigerant line 102 into and through the heat exchange tubes of the condenser 110, wherein the hot refrigerant vapor is desuperheated, condensed to a liquid and typically subcooled, as it passes in heat exchange relationship with a cooling fluid, such as ambient air, which is blown over the heat exchange tubes of the condenser 110 by the condenser fan 115.
  • a cooling fluid such as ambient air
  • a drain pan 45 is provided beneath the evaporator heat exchanger 10 for collecting condensate that drains from the external surfaces of the heat transfer tubes 40 and associated fins 50.
  • the heat exchanger 10 will be described herein in general with reference to the illustrative exemplary embodiment of a section of the heat exchanger 10 depicted in FIGs. 2-4.
  • the heat exchanger 10 includes a heat exchange tube circuit arrangement 12 and a blow-off condensate collecting screen 60 disposed downstream of the heat exchanger 10, with respect to the airflow.
  • the heat exchange tube circuit arrangement 12 includes a plurality of round heat exchange tubes 40 arranged in a parallel array, each tube extending in a horizontal direction along its longitudinal axis and being interconnected to another tube by a hairpin return bend 41 to form a serpentine circuit. Although a single circuit is shown in Figure 2 for simplicity purposes, multi-circuit arrangements are utilized quite often in the art and are within the scope of the invention.
  • different circuits may not necessarily be of equal length, and, in evaporator applications, a number of parallel refrigerant circuits is either identical throughout an evaporator or diverges towards the downstream end.
  • hairpin configurations are used, instead of straight tube arrangements, with the return bends required only on one side of the hairpins to form each evaporator serpentine refrigerant circuit.
  • the round heat exchange tubes 40 have a diameter of 1/2 inch, 3/8 inch or 7 millimeters.
  • the serpentine tube circuit 12 of the heat exchanger 10 has an inlet end connected in refrigerant flow communication to refrigerant line 104, through a distributor or an inlet manifold (not shown), for receiving refrigerant flow from the refrigerant cycle and an outlet end connected in refrigerant flow communication to refrigerant line 106, through an outlet manifold (not shown), for returning refrigerant flow to the refrigerant cycle.
  • the heat exchanger 10 includes a plurality of external heat transfer fins 50 extending between each set of the parallel-arrayed tubes 40.
  • the fins 50 are brazed or otherwise securely (e.g., mechanically) attached to the external surfaces of the adjoining tubes 40 to establish heat transfer contact, by heat conduction, between the fins 50 and the external surfaces of the heat transfer tubes 40.
  • the external surfaces of the heat exchange tubes 40 and the surfaces of the associated fins 50 together form the external heat transfer surface that participates in heat transfer interaction with the air flowing through the heat exchanger 10.
  • the external heat transfer fins 50 also provide for structural rigidity of the heat exchanger 10 and quite often assist in airflow redirection and velocity increase to improve heat transfer characteristics. In the exemplary embodiment of the heat exchanger 10 depicted in Fig.
  • the heat transfer fins 50 constitute a plurality of plates disposed in parallel, spaced relationship and extending generally vertically between the heat exchange tubes 40 positioned horizontally.
  • other fin configurations such as, for example, wavy or louvered fins may be used instead in the evaporator heat exchanger of the invention.
  • condensate collecting on the external surfaces of the heat exchange tubes 40 and associated fins 50 may be stripped away from the tube surface and be re-entrained in the airflow passing over the heat exchange tubes 40 and associated fins 50, rather than draining from the external surfaces of the heat exchange tubes 40 and associated fins 50 to flow under the force of gravity to the drain pan 45. If condensate doesn't drain quickly under the force of gravity, at certain airflow velocities and operating conditions, some amount of the collected condensate can be blown off external evaporator surfaces and re-enter an air stream downstream of the evaporator heat exchanger.
  • a condensate collecting screen 60 is disposed downstream, with respect to the airflow, as shown in Figure 2. As the airflow leaving the heat exchanger 10 traverses the downstream condensate collecting screen 60, the airflow passes through the openings 65 formed by the lattice structure 62 of the condensate collecting screen 60. Therefore, the condensate still entrained in the airflow downstream of the heat exchanger 10 is captured upon the lattice structure 62 of the condensate collecting screen 60, thereby removing the condensate from the airflow.
  • the condensate collecting screen 60 may comprise a wire mesh screen made of aluminum, stainless steel, plastic or other rust-resistant material wire.
  • the condensate collecting screen 60 comprises a screen having a honeycomb mesh lattice structure 62 defining hexagonally-shaped openings 65 through which airflow passes.
  • the porosity of the screen 60 that is the open area through which the airflow passes, should be large enough that the screen 60 presents a relatively small air-side pressure drop.
  • the lattice structure 62 should have sufficiently large surface area as to present an effective barrier for capturing the condensate entrained in the airflow from passing through the condensate collecting screen 60.
  • the specific condensate collecting screen porosity desirable for any particular heat exchanger arrangement will depend upon the heat exchanger design and orientation as well as the particular operating conditions to which the heat exchanger is exposed.
  • the condensate collecting screen 60 will have porosity, defined as the overall open cross-section area provided by the openings 65 as a percentage of the total face area of the screen 60, in the range of from about 60 percent to about 85 percent.
  • the lattice structure 62 of the condensate collecting screen 60 may have pentagonal, square, triangular or any other cells, instead of than hexagonal cells shown in FIG. 3.
  • a network of interconnected condensate flow channels 64 is formed on the face 66 of the mesh screen lattice structure 62 facing upstream, with respect to airflow leaving the heat exchanger 10.
  • the condensate flow channels 64 facilitate drainage of condensate depositing on the face 66 of the screen 60 downwardly, under the influence of gravity, into the drain pan 45.
  • the depth of the condensate flow channels and particular shape of the channels are within the skill of the ordinary artisan to select and primarily depend on the particular heat exchanger design and specific operating conditions.
  • the depth of the condensate flow channels 64 may increase towards the bottom portion of the condensate collecting screen 60 to accommodate large condensate amounts drained under the force of gravity.
  • the heat exchanger 10 shown in the exemplary embodiment depicted in FIGs. 1 and 2 is illustrated as a round tube and plate fin heat exchanger, it is to be understood that the condensate collecting screen 60 may be used in connection with any type of evaporator heat exchangers used in refrigerant vapor compression systems. For example, as depicted in FIG.
  • the evaporator heat exchanger 10 could have multi-channel, flattened tubes 140, for example of rectangular or oval cross-section, extending longitudinally in parallel relationship between a pair of spaced headers or manifolds 150 and 160 for distributing refrigerant from the refrigerant cycle amongst the heat exchange tubes 140 and collecting refrigerant from the tubes 140 for return to the refrigerant cycle.
  • each flattened multi-channel heat exchange tube 140 might have a width of fifty millimeters or less, typically from ten to thirty millimeters, and a height of about two millimeters or less.
  • Each flattened heat exchange tube 140 defines a plurality of parallel flow-channels 142, that can be of round, rectangular, trapezoidal, triangular, or other cross-section, typically from about ten to about twenty in number, extending longitudinally the entire length of the tube.
  • Each channel provides a refrigerant flow path of relatively small cross- sectional area and having a hydraulic diameter, defined as four times the cross- sectional flow area divided by the "wetted" perimeter, in the range generally from about 200 microns to about 3 millimeters.
  • a heat exchanger with multichannel heat exchange tubes extending in parallel relationship between the inlet and outlet headers of the heat exchanger will have a relatively large number of small flow area refrigerant flow paths extending between the two headers.
  • multi-channel heat exchanger constructions are called microchannel or minichannel heat exchangers as well.
  • the return bends are substituted by intermediate manifolds or manifold chambers, while a number of parallel circuits is defined by a number of parallel heat transfer tubes within each pass.
  • heat transfer fins 150 may be of different serpentine design here, may have louvers or offset strips, and typically define rectangular, triangular, trapezoidal, etc. airflow passages within the evaporator heat exchanger.
  • the condensate collecting screen 60 has been particularly shown and described with reference to the exemplary embodiments of the heat exchangers as illustrated in the drawings, it is to be understood that the condensate collecting screen is not limited in application to heat exchangers having horizontally disposed heat exchange tubes, but may be used in connection with heat exchangers having heat exchange tubes disposed so as to extend longitudinally in a vertical direction or other non-horizontal (inclined) direction.
  • heat exchanger drainage characteristics depend on heat exchanger design and orientation, at certain airflow velocities, condensate blow-off phenomenon can be experienced for any heat exchanger configuration in a vast majority of operating conditions that the present invention would address.
  • blow- off phenomenon is described in connection to evaporators of refrigerant systems operating in a vapor compression cycle, cooling heat exchangers of air handling equipment, utilizing cold water or glycol solutions to cool and dehumidify air supplied to the conditioned environment, take advantage and equally benefit from the invention. Further, it is to be understood that one skilled in the art may make various changes in detail in the present invention without departing from the spirit and scope of the invention as defined by the claims.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)

Abstract

La présente invention se rapporte à un échangeur de chaleur qui comprend une surface de transfert de chaleur comprenant une pluralité de tubes d'échange de chaleur de transport de réfrigérant et d'ailettes associées. Un tamis de collecte de condensats est disposé en aval de l'échangeur de chaleur, par rapport à l'écoulement de l'air. Des condensats qui se sont accumulés sur les surfaces externes des tubes d'échange de chaleur et des ailettes associées, et qui ont été transportés de ce fait dans le flux d'air vers l'aval, sont collectés sur la surface dirigée vers l'amont du tamis de collecte de condensats. Des canaux d'écoulement de condensats formés dans une surface de la structure du tamis de collecte de condensats dirigée vers l'amont, par rapport à l'écoulement de l'air, fournissent des passages de vidange pour une purge plus efficace des condensats à partir du tamis. Le tamis de collecte de condensats peut avoir une structure en nid d'abeille ou une structure maillée.
PCT/US2006/049195 2006-12-26 2006-12-26 Échangeur de chaleur avec tamis de collecte et de purge de condensats WO2008079121A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/US2006/049195 WO2008079121A1 (fr) 2006-12-26 2006-12-26 Échangeur de chaleur avec tamis de collecte et de purge de condensats

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PCT/US2006/049195 WO2008079121A1 (fr) 2006-12-26 2006-12-26 Échangeur de chaleur avec tamis de collecte et de purge de condensats

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3128277A1 (fr) * 2015-08-03 2017-02-08 DongHwan Ind. Corp. Évaporateur doté d'agencement vertical de tuyau collecteur pour un climatiseur de véhicule
CN109164931A (zh) * 2018-07-26 2019-01-08 合肥金新允电子技术有限公司 一种elo工业触摸显示器的散热装置
WO2020121186A1 (fr) * 2018-12-11 2020-06-18 Denso Thermal Systems S.P.A. Système de climatisation muni d'un séparateur de gouttelettes, en particulier pour un véhicule automobile

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2952993A (en) * 1957-12-13 1960-09-20 Carrier Corp Air conditioner
US3217798A (en) * 1962-12-05 1965-11-16 American Radiator & Standard Heat exchanger
US3882690A (en) * 1973-09-28 1975-05-13 Carrier Corp Heat exchange assembly
US5261946A (en) * 1992-02-11 1993-11-16 La-Man Corporation Air line vapor trap with air-warming system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2952993A (en) * 1957-12-13 1960-09-20 Carrier Corp Air conditioner
US3217798A (en) * 1962-12-05 1965-11-16 American Radiator & Standard Heat exchanger
US3882690A (en) * 1973-09-28 1975-05-13 Carrier Corp Heat exchange assembly
US5261946A (en) * 1992-02-11 1993-11-16 La-Man Corporation Air line vapor trap with air-warming system

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3128277A1 (fr) * 2015-08-03 2017-02-08 DongHwan Ind. Corp. Évaporateur doté d'agencement vertical de tuyau collecteur pour un climatiseur de véhicule
CN106440533A (zh) * 2015-08-03 2017-02-22 东焕产业株式会社 具备集流管的垂直设置结构的车辆用空调蒸发器
CN109164931A (zh) * 2018-07-26 2019-01-08 合肥金新允电子技术有限公司 一种elo工业触摸显示器的散热装置
CN109164931B (zh) * 2018-07-26 2021-07-27 合肥金新允电子技术有限公司 一种elo工业触摸显示器的散热装置
WO2020121186A1 (fr) * 2018-12-11 2020-06-18 Denso Thermal Systems S.P.A. Système de climatisation muni d'un séparateur de gouttelettes, en particulier pour un véhicule automobile

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