HK1166519A - Air treatment module - Google Patents

Description

Air treatment module

Cross Reference to Related Applications

This application claims priority to U.S. provisional patent application 61/154,974 entitled "air treatment module" filed on 24.2.2009. The entire contents of this application are incorporated herein by reference.

Technical Field

The present invention relates generally to air treatment modules, such as heating units, ventilation units including heat exchangers, or air conditioning (HVAC) units, and more particularly to improvements in heat exchanger performance in such air treatment modules. Air handling units, including air heating modules, are commonly used in residential and commercial buildings to heat air for supply to climate controlled spaces. Such air handling units include, for example, products designed to have both heating and cooling capabilities, as well as seasonal heating products.

Background

Commercial HVAC units, which include a heating function in addition to a cooling or cooling/dehumidifying function, housed in a common cabinet, are often used for heating, ventilation and air conditioning on commercial buildings. Typically, such packaged HVAC units are mounted on the roof of a building and connected to an air duct system associated with the building for conveying air from the building to be temperature conditioned to the HVAC unit and distributing the temperature conditioned air throughout the building. In some applications, the packaged HVAC unit is floor mounted outside the building, rather than on the roof of the building.

Such year-to-year packaged HVAC units include an indoor portion and an outdoor portion housed in a common chassis, but separated into separate compartments by partitions and walls. The outdoor portion includes one or more condensing units each having a condenser heat exchanger coil and an associated fan, and also includes other components, such as a refrigerant compressor. The indoor portion includes an air conditioning module having an evaporator heat exchanger coil and associated one or more evaporator fans, and an air heating module.

Typically, the air heating module includes a furnace heat exchanger and an associated combustion system. In one type of air heating module, the furnace heat exchanger includes a plurality of elongated hairpin-configured tubes that define an internal flow passage through which hot flue gas produced by the associated combustion system passes. The furnace heat exchanger is disposed in an air heating plenum (plenum) through which indoor air passes over the outer surface of the heat exchanger tubes in heat exchange relationship with hot flue gas passing through the furnace heat exchanger tubes.

The air-heating plenum is typically disposed downstream, with respect to air flow, of the air discharge of one or more indoor air fans. The heat exchanger tubes extend horizontally through the air heating plenum. The flue gas passing through each heat exchange tube is hottest at the inlet of each hairpin structured tube and coldest at the outlet of each hairpin structured tube. In some designs, the air passes vertically downward over the heat exchange duct to exit downward through an opening in a door of the air plenum. In other designs, the air enters the air-heating plenum vertically downward, but turns 90 degrees in the plenum to exit horizontally through openings in the end sides of the air-heating plenum. Thus, the air flow passes both across and along the hairpin configured tubes of the furnace heat exchanger, thereby increasing the time the air flow passes in heat exchange relationship with the flue gas relative to applications in which the air flow passes directly vertically downward over the heat exchange tubes.

In areas where the air flow across or along the heat exchange tubes is relatively low, the effectiveness of the heat exchanger will be negatively affected, that is to say the heat exchange from the flue gas to the air will be reduced. The air flow across or along the heat exchange tubes may be reduced in certain areas due to the turning of the air flow as it passes through the air plenum. The reduced heat transfer may result in high temperature zones, i.e. hot spots, of the heat exchange tube surface, which may also negatively affect the reliability of the heat exchanger. Common measures taken in attempting to provide a more uniform airflow across the heat exchanger and/or in attempting to increase airflow in areas where the airflow is weaker (e.g., increasing fan exhaust and air discharge opening area, installing large fans, adding baffles in the heat exchanger, or adding fins on the heat exchanger tubes) add increased cost to the system and are not always effective in improving heat transfer to the airflow.

Disclosure of Invention

In one aspect of the invention, an air treatment module includes an air plenum, a heat exchanger duct, and a bypass duct. The air plenum defines an air flow path and has an air inlet for receiving an air stream to be treated and an air outlet through which the treated air stream is discharged from the air plenum. The heat exchanger tubes are disposed in the airflow path in the air plenum for conveying a heat transfer fluid in heat exchange relationship with the air stream to be treated. The bypass duct has an inlet opening in flow communication with the air plenum, juxtaposed with a selected region of the heat exchanger tube, downstream of the heat exchanger tube with respect to air flow, and an outlet opening in flow communication with a lower air pressure region. In one embodiment, the outlet of the bypass duct opens into flow communication with an air supply duct for conveying the air flow to be treated to the air plenum.

In one aspect of the invention, a packaged air conditioning unit is provided. The packaged air conditioner may be connected in flow communication with an indoor air return duct and with an indoor air supply duct, and an indoor air mover, an air cooling module, and an air heating module for drawing indoor air to be conditioned from a conditioned space through the indoor air supply duct. The air heating module includes: a housing defining an air plenum, the air handling plenum establishing an air flow path and having an air inlet opening in flow communication with the exhaust outlet of the indoor air mover and an air outlet opening in flow communication with the indoor air supply duct; a heat exchanger module disposed in the airflow path in the air plenum for conveying a heat transfer fluid in heat exchange relationship with an indoor airflow; and a bypass conduit having an inlet opening in flow communication with said air plenum juxtaposed with a selected area of said heat exchanger module downstream of said heat exchange module with respect to air flow and an outlet opening in flow communication with a lower air pressure zone. For example, the bypass duct may open in flow communication with a region of the air plenum that is upstream with respect to airflow from an outlet of the air plenum opening and downstream with respect to airflow from an inlet of the bypass duct, or the bypass duct may open in flow communication with the indoor air return duct upstream with respect to airflow from an inlet of the indoor air mover.

In one embodiment of the packaged air conditioning unit, the indoor air mover to the air plenum is disposed upstream with respect to the heat exchanger module, the inlet of the bypass duct opens into the air plenum housing, juxtaposed with a selected region of the heat exchanger module, and the air outlet from the air plenum is disposed in an end wall of the air plenum housing. The air cooling module may include an air cooling evaporator disposed upstream of the indoor air mover with respect to indoor air flow. The air mover may comprise a centrifugal fan.

In one embodiment, the heat exchanger module includes a plurality of heat exchange tubes through which the hot combustion flue gas passes in heat exchange relationship with the indoor air flow through the air plenum. The plurality of heat exchange tubes may comprise a plurality of independent hairpin heat exchange tubes. The packaged air conditioning unit may include a plurality of flue gas producing burners, a respective one of the plurality of flue gas producing burners being operatively associated with a respective one of the plurality of heat exchange tubes.

Drawings

For a further understanding of the disclosure herein, reference will be made to the following detailed description, which should be read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a plan view, partially in section, of a roof air conditioner;

FIG. 2 is a side elevational view, partially in section, taken along line 2-2 of FIG. 1;

FIG. 3 is a perspective view of a portion of the rooftop air conditioner of FIG. 1 showing an indoor air mover and air heating module thereof;

FIG. 4 is a perspective view of the air heating module shown in FIG. 3;

FIG. 5 is a perspective view of the bypass duct shown in FIG. 4;

FIG. 6 is a perspective view of the bypass duct shown in FIG. 5, viewed from the rear side of FIG. 5;

FIG. 7 is a schematic diagram illustrating one embodiment of an air treatment module having a bypass circuit; and is

FIG. 8 is a schematic diagram illustrating another embodiment of an air treatment module having a bypass circuit.

Detailed Description

An exemplary embodiment of the air treatment module of the present invention will be described herein for purposes of illustration with respect to a year-to-year packaged air conditioning unit, generally designated by reference numeral 2. It should be understood, however, that the air treatment modules disclosed herein may be used in other applications, including, for example, but not limited to, seasonal heating products such as residential or commercial heating stoves.

Referring initially to fig. 1-2 of the drawings, there is shown in particular an exemplary embodiment of a packaged air conditioning unit typically mounted on the roof of a building, such as a school, hospital, office building or other commercial location. In some arrangements, however, the packaged air-conditioning unit 2 may be mounted on a support mat at ground level. The enclosed air conditioning unit 2 includes a housing 4, the housing 4 being divided by a wall 5 into an outdoor portion 10 and an indoor portion 20. The outdoor section 10 includes one or more condenser units 12, each of which includes a condenser coil 14, a condenser fan/motor assembly including a fan 15 and an associated drive motor 16, and a grill or cover (not shown). A condenser fan 15, driven by a condenser fan motor 16, passes ambient outdoor air over the outer surface of the condenser coil 14 surrounding the condenser fan/motor assembly to cool the refrigerant circulating through the condenser coil 14 and discharge the air back into the ambient atmosphere. The outdoor section 10 may also include one or more compressors (not shown) for compressing refrigerant vapor and circulating the refrigerant through a refrigerant circuit (not shown) connecting the compressor(s), the condenser coil(s) 14, and the evaporator heat exchanger of the air cooling module 30 disposed in the indoor section 20.

The indoor section 20 includes an indoor air mover 22 and, generally, the indoor section 20 includes an air cooling module 30 and an air heating module 40. The air cooling module 30 includes an evaporative heat exchanger and is disposed upstream, with respect to indoor airflow, of the air intake 24 to the indoor air mover 22, while the heating module 40 is disposed downstream, with respect to indoor airflow, of the air exhaust 26 of the indoor air mover 22. Evaporative heat exchangers may include heat exchanger tube coils or bundles of tubes wherein a cooling medium, such as a refrigerant or chilled water, may be selectively passed through the tubes in heat exchange relationship with the air passing over the tubes of the tube coil when it is desired to cool the air.

When installed in a building for conditioning air within a temperature controlled space in the building, the packaged air conditioning unit 2 may be connected in flow communication with an indoor air return duct 6 and with an indoor air supply duct 8. Also, if desired, louvers or vents may be provided in the housing which are selectively openable to allow outdoor air to be drawn into the supply air plenum 45 to mix with the indoor air passing therethrough. The indoor section 20 includes a return air plenum space 35 and a supply air plenum space 45, the return air plenum space 35 having an inlet in flow communication with the return air duct 6 and the supply air plenum space 45 having an outlet in flow communication with the supply air duct 8. In the illustrated embodiment, the indoor air mover 22 may be a centrifugal fan having a pair of side intake openings 24. The air inlet 24 of the indoor air mover 22 is in flow communication with the return air plenum 35 and the air outlet 26 from the indoor air mover 22 is open to flow communication with the supply air plenum 45, the supply air plenum 45 being located in the heating module 40. In operation, the indoor air mover 22 draws an indoor air stream from the climate controlled space in the building through the return air duct 6 and the return air plenum 35 and passes the air stream back into the climate controlled space through the supply air plenum 45 and the supply air duct 8. While passing through the return air plenum 35, the air flows through the cooling module 30. It should be understood that the return air plenum 35 may have a plurality of return air inlets opening thereto and a plurality of associated air movers, while the supply air plenum 45 may have a plurality of supply air outlets.

Referring now also to fig. 3-6 of the drawings, the heating module 40 includes a supply air plenum 45, one or more heat exchanger modules 50, and a bypass conduit 60. The supply air plenum 45 defines an air flow path and has an air inlet for receiving an air flow from the air outlet of the indoor air mover 22 and an air outlet through which the air flow is discharged from the supply air plenum 45 into the supply air duct 8. Heat exchanger module(s) 50 are disposed in the air flow path in the supply air plenum 45 for conveying a heat transfer fluid in heat exchange relationship with the air flow to be heated. The bypass duct has an air inlet 62 or inlets 62, 62 opening into flow communication with the air plenum space 45, juxtaposed with selected regions of the heat exchanger module(s) 50, and an outlet opening into flow communication with the lower air pressure region downstream of the heat exchange duct module(s) with respect to air flow. In the embodiment shown in fig. 3-6, the outlet 64 of the bypass duct 60 is open in flow communication with the return air plenum 35 for conveying the air flow received into the bypass duct 60 back to the suction side of the indoor air mover 22.

In the illustrated embodiment, the air heating module 40 includes a pair of heat exchanger modules 50, with one module disposed above the other. Air passing from the air outlet 26 of the indoor air mover 22 flows generally downwardly and through both of the heat exchanger modules 50 and then exits the supply air plenum 45 into the supply air duct 8. It should be understood, however, that in some arrangements, the air heating module 40 may include a single heat exchanger module 50 or more than two heat exchanger conduit modules.

In the illustrated embodiment, each heat exchanger duct module 50 includes a plurality of individual heat exchanger ducts 52 through which hot combustion flue gas passes in heat exchange relationship with the indoor air flow passing through the air plenum. However, it should be understood that the heat exchanger module 50 may alternatively comprise a liquid-to-air tubular heat exchanger or a resistive heating element or other type of heat exchanger that heats air by passing the air over a heated surface. Each heat exchange tube 50 may comprise a hairpin heat exchange tube. The plurality of heat exchange tubes may comprise a plurality of independent hairpin heat exchange tubes. In the illustrated embodiment, a plurality of flue gas producing burners 54, a respective one of the plurality of flue gas producing burners 54 is operatively associated with a respective one of the plurality of heat exchange tubes 52. Each burner 54 combusts fossil fuel (typically, natural gas) in air to produce hot combustion products (referred to as flue gases) that enter the inlet end of a respective heat exchange tube 52 associated with the respective burner 54. The hot flue gases pass through the heat exchange tubes 52 and are discharged from the outlets of the heat exchange tubes into an exhaust chamber 57, the flue gases are discharged from the exhaust chamber 57 via a fan 56 into a flue duct 58 and through the flue duct 58, the flue duct 58 being open to the atmosphere. While passing through the heat exchange tubes 52, the hot flue gas is cooled by heat transfer to the indoor air passing through the supply air plenum 45.

The bypass conduit 60 is arranged in juxtaposition with the heat exchanger module 50 or a lower heat exchanger module of the plurality of heat exchanger modules, in juxtaposition with a specific region of the heat exchanger module 50 where it is desired to increase the indoor air flow over the heat exchanger tubes in that specific region. Since the outlet 64 of the bypass duct 60 opens into a lower air pressure region (such as the return air plenum 35 in the illustrated embodiment), a greater amount of indoor air flow through the supply air plenum 45 will be drawn through the inlet opening 62 of the supply air duct, thereby increasing the air flow over the heat exchange tubes 52 in that particular region of the heat exchanger module. For example, in the illustrated embodiment, as best shown in FIG. 4, a bypass duct 60 is disposed below the lower heat exchanger module 50 at an end thereof where hot flue gas produced by the combustor 54 enters the respective heat exchanger tubes 52. This is usually the hottest area of the pipe surface. Without the bypass duct 60, this area would also typically be a low airflow capacity area on the heat exchanger tubes.

The bypass air may be reintroduced into the primary air stream passing through the air treatment module at the lower air pressure zone. In one embodiment, the bypass duct may be open in flow communication with a lower air pressure region upstream of the air mover with respect to the air flow, as schematically illustrated in FIG. 7, whereby bypass air is reintroduced into the primary air flow upstream of the air mover. For example, in the illustrated embodiment of the packaged air conditioning unit 2, the outlet 64 of the bypass duct 60 opens directly into the air mover plenum on the suction side of the indoor air mover 22. It should be understood, however, that the bypass air may be introduced in other lower air pressure regions further upstream of the air mover 22, such as back into the return air plenum 35 slightly downstream of the inlet of the supply air duct 8, or even directly into the supply air duct 8.

In one embodiment, the bypass conduit may open in flow communication with a region of lower air pressure further downstream with respect to the air flow at the inlet of the bypass conduit, as schematically illustrated in fig. 8. For example, the bypass air may be directed to another lower air pressure region, for example back into the supply air plenum 45 at a location further downstream with respect to the flow of air through the supply air plenum 45 than the inlet 62 of the bypass duct 60, as shown in fig. 8, where the outlet of the bypass duct 60 opens into the supply air plenum 45 near the outlet of the supply air duct 8.

Applying the bypass airflow concepts disclosed herein in conjunction with one or more selected regions of the heat exchanger module results in an increased airflow over the heat exchanger tubes or heating elements in the one or more selected regions, thereby increasing heat transfer in the one or more selected regions, and the airflow through the heat exchanger module is typically more uniform. Thus, by eliminating high temperature zones (i.e., hot spots) on the surface of the heat exchanger tubes or other heating elements, heat exchanger module performance is enhanced and system reliability is enhanced. As the bypass airflow is reintroduced into the primary airflow through the air treatment module, the heat energy of the bypass airflow is recovered, thereby maintaining the thermal efficiency of the system. Moreover, the bypass air concept disclosed herein is less costly to implement than existing methods of increasing heat exchanger performance, such as increasing fan capacity.

The terminology used herein is for the purpose of description and not of limitation. Specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for teaching one skilled in the art to utilize the present invention. While the present invention has been particularly shown and described with reference to the exemplary embodiments shown in the drawings, those skilled in the art will recognize that various modifications may be made without departing from the spirit and scope of the invention. Those skilled in the art will also recognize certain equivalents which may be substituted for elements described with reference to the exemplary embodiments disclosed herein without departing from the scope of the invention.

Therefore, it is intended that the disclosure not be limited to the particular embodiment(s) disclosed, but that the disclosure will include all embodiments falling within the scope of the appended claims.

Claims (16)

1. An air treatment module comprising:

an air handling plenum defining an air flow path and having an air inlet for receiving an air flow to be treated and an air outlet through which a treated air flow is discharged from the air handling plenum;

a heat exchanger disposed in the airflow path in the air-handling plenum for conveying a heat transfer fluid in heat exchange relationship with the airflow to be handled; and

a bypass duct having an inlet opening in flow communication with said air handling plenum juxtaposed to a selected area of said heat exchanger and an outlet opening in flow communication with a lower air pressure zone.

2. The air treatment module as claimed in claim 1, wherein the outlet of the bypass duct opens in flow communication with an air supply duct for conveying the air flow to be treated to the air treatment plenum.

3. The air treatment module of claim 1, further comprising an air mover disposed upstream with respect to air flow of the air treatment plenum for supplying the air flow to be treated to the air treatment plenum.

4. The air treatment module of claim 3, wherein the outlet of the bypass duct opens in flow communication with a lower air pressure region upstream of the air mover with respect to air flow.

5. The air treatment module as recited in claim 1 wherein the outlet of the bypass duct opens in flow communication with a region of the air treatment module downstream of the inlet of the bypass duct with respect to air flow.

6. An air handling unit adapted to be connected in flow communication with an indoor air return duct and with an indoor air supply duct, the air handling module including an air mover for drawing indoor air to be conditioned from a conditioned space through the indoor air supply duct, an air cooling module, and an air heating module, the air heating module comprising:

a housing defining an air handling plenum establishing an air flow path and having an air inlet opening in flow communication with the exhaust outlet of the air mover and an air outlet opening in flow communication with the indoor air supply duct;

a heat exchanger module disposed in the airflow path in the air-handling plenum for conveying a heat transfer fluid in heat exchange relationship with an indoor airflow; and

a bypass conduit having an inlet opening in flow communication with said air handling plenum juxtaposed with a selected area of said heat exchanger module downstream of said heat exchange module with respect to air flow and an outlet opening in flow communication with a lower air pressure zone.

7. The air treatment module of claim 6, wherein the air mover is disposed upstream of the heat exchanger module with respect to air flow.

8. The air treatment module as recited in claim 7 wherein the air outlet from the air handling plenum opens from the air handling plenum housing under selected areas of the heat exchanger module.

9. The air treatment module of claim 8, wherein the air outlet from the air treatment plenum is disposed in an end wall of the air plenum housing.

10. The air treatment module as recited in claim 6 wherein the outlet of the bypass duct opens in flow communication with a region of the air treatment plenum downstream of the inlet of the bypass duct with respect to air flow.

11. The air treatment module of claim 6, wherein the outlet of the bypass duct opens in flow communication with the indoor air return duct upstream of an inlet of the indoor air mover with respect to air flow.

12. The air treatment module as recited in claim 6 wherein the heat exchanger module includes a plurality of heat exchange tubes through which the hot combustion flue gas passes in heat exchange relationship with the flow of indoor air through the air plenum.

13. The air treatment module as recited in claim 12 wherein the plurality of heat exchange tubes comprises a plurality of independent hairpin heat exchange tubes.

14. The air treatment module of claim 13, further comprising a plurality of flue gas producing burners, a respective one of the plurality of flue gas producing burners being operatively associated with a respective one of the plurality of heat exchange tubes.

15. The air treatment module of claim 6, wherein the air cooling module includes an air-cooled evaporator disposed upstream of the indoor air mover with respect to indoor air flow.

16. The air treatment module of claim 6, wherein the air mover comprises a centrifugal fan.