HK1158738A - Design characteristics for heat exchanger distribution insert - Google Patents

Description

Design features for heat exchanger distribution insert

RELATED APPLICATIONS

This application claims priority to U.S. provisional patent application 61/079,521 filed on 10/7/2008.

Background

A microchannel or minichannel heat exchanger for a refrigeration or air conditioning system includes a plurality of parallel, flattened heat exchange tubes with refrigerant distributed therein. The inlet manifold is in fluid communication with heat exchange tubes, and the heat exchange tubes are substantially perpendicular to the direction of refrigerant flow through the inlet manifold. Heat exchangers can have multi-pass configurations to improve performance by balancing and optimizing heat transfer and pressure drop characteristics, which is typically accomplished by employing multiple parallel heat exchange tubes within each refrigerant pass (pass). Single pass configurations are generally more desirable in evaporator applications because the refrigerant pressure drop dominates the evaporator performance.

Uneven distribution of refrigerant into the heat exchange tubes may occur, which may result in reduced performance of the heat exchanger compared to that achievable if the refrigerant is distributed evenly in the heat exchange tubes. Maldistribution typically occurs when two-phase refrigerant enters the inlet manifold. The gas phase of the two-phase refrigerant has significantly different properties compared to the liquid phase refrigerant, moves at different speeds, and is subjected to different external and internal forces. The gas phase separates from the liquid phase and flows independently, causing uneven refrigerant distribution.

A distribution insert may be employed inside the inlet manifold of the heat exchanger to improve the distribution of the refrigerant. Refrigerant enters the heat exchanger through the distribution insert and flows into the inlet manifold through orifices in the distribution insert. Due to the nature of two-phase refrigerant flow, it is difficult to design a distribution insert.

Disclosure of Invention

A heat exchanger includes heat exchange tubes, a manifold, and a distribution insert including orifices that convey fluid into the manifold for distribution into the heat exchange tubes. A design characteristic of the distribution insert and another design characteristic of at least one of the distribution insert, the manifold and the heat exchange tubes are used to determine a fundamental design relationship. The basic design relationship defines design parameters that fall within a determined range of values.

In another exemplary embodiment, a method of designing a heat exchanger includes the steps of: a range of values is determined and at least one design characteristic of the dispense insert is selected. The distribution insert includes an orifice and is received in a manifold. Fluid is conveyed through the plurality of orifices and into the manifold for distribution into the heat exchange tubes. The method further comprises the steps of: determining a relationship between the at least one design characteristic of the distribution insert and another characteristic of at least one of the distribution insert, the manifold and the heat exchange tubes. The basic design relationship defines a design parameter that falls within the range of values.

These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.

Drawings

FIG. 1 illustrates an exemplary refrigeration system;

FIG. 2 shows a side view of an inlet portion of a manifold of a heat exchanger; and

FIG. 3 illustrates a perspective view of an inlet portion of a manifold of a heat exchanger, showing various dimensions.

Detailed Description

Fig. 1 shows a basic refrigeration or air conditioning system 20 including a compressor 22, which compressor 22 compresses and delivers refrigerant downstream to a condenser 24. In the condenser 24, the refrigerant rejects heat to a secondary fluid. From the condenser 24, the refrigerant passes through an expansion device 26 and is expanded to a low pressure. The expanded refrigerant flows into an inlet refrigerant line 28 leading to an evaporator 30. In the evaporator 30, the refrigerant receives heat from another secondary fluid. From the evaporator 30, the refrigerant returns to the compressor 22, completing the closed-loop refrigerant circuit.

The air conditioning system 20 may include a refrigerant flow control device, such as a four-way reversing valve shown schematically at 35, to reverse the direction of refrigerant flow through the refrigerant circuit to accommodate heat pump configurations and applications. When the refrigeration system 20 is operating in the cooling mode, the four-way reversing valve 35 directs refrigerant from the compressor 22 to the condenser 24. When the refrigeration system 20 is operating in the heating mode, the four-way valve 35 directs refrigerant from the compressor 22 to the evaporator 28 (which acts as a condenser in the heating mode).

Fig. 2 shows a portion of the evaporator 30. The evaporator 30 includes a manifold 34. In one example, the manifold 34 is an inlet manifold or intermediate manifold of the evaporator 30. In the following examples, the inlet manifold of the evaporator 30 is described. In one example, the evaporator 30 is a microchannel heat exchanger.

However, the features of the present invention can be extended to other types of heat exchangers, such as round tube and plate fin heat exchangers, and to other applications, such as condensers and reheat heat exchangers. Further, while the present invention will be disclosed with reference to the manifold 34 of the evaporator 30, the intermediate manifold of the condenser 24 is also within the scope of the present invention. The condenser 24 may also be a microchannel heat exchanger. Additionally, while the benefits of the present invention will be disclosed with reference to a two-phase refrigerant flow through the evaporator 30, single-phase refrigerant flows and mixtures of refrigerant and oil are also within this range and may benefit from the present invention.

The inlet refrigerant conduit 28 is in fluid communication with a distribution insert 32 received within a manifold 34, which provides a refrigerant flow path along the longitudinal axis X. Distribution insert 32 is in fluid communication with a plurality of heat exchange tubes 36 positioned generally perpendicular to manifold 34. The inlet refrigerant conduit 28 may be located at an end of the manifold 34, in the middle of the manifold 34, or at any intermediate location therebetween, and may have a single or multiple connections to the distribution insert 32. Each heat exchange tube 36 may be a flat tube and may have a plurality of ports for refrigerant to flow therethrough. In one example, each port has a hydraulic diameter of less than 1 mm.

A plurality of heat transfer fins 38 may be disposed between heat exchange tubes 36 and rigidly attached to heat exchange tubes 36 to enhance external heat transfer and provide structural rigidity to evaporator 30. In one example, a plurality of heat transfer fins 38 are attached to heat exchange tubes 36 by a furnace brazing process.

The distribution insert 32 includes a plurality of refrigerant distribution orifices 42 to provide a refrigerant path from the internal cavity 50 of the distribution insert 32 to the manifold 34. The dispensing orifice 42 may have any shape. For example, the dispensing orifice 42 may have a circular shape, a rectangular shape, an oval shape, or any other suitable shape.

The distribution insert 32 receives two-phase refrigerant from the inlet refrigerant tubes 28 and delivers the refrigerant uniformly through a plurality of distribution orifices 42 and into the manifold 34 for distribution into the heat exchange tubes 36. Generally, the relatively small size of the distribution insert 32 provides significant momentum for refrigerant flow, preventing phase separation of two-phase refrigerant or promoting annual (as opposed to stratified) refrigerant flow patterns.

Fig. 3 illustrates various design characteristics, such as the diameter, length, location, and other dimensions of the components of the evaporator 30. The evaporator 30 is designed for optimal refrigerant distribution. At least one design characteristic of the dispensing insert 32 is selected. The fundamental design relationship between at least one design characteristic of the distribution insert 32 and another design characteristic of at least one of the distribution insert 32, the manifold 34 and the heat exchange tubes 36 is determined and defines design parameters. If the design parameter falls within a predetermined range of values, this indicates that evaporator 30 is designed for optimal refrigerant distribution to heat exchange tubes 36 and prevents or significantly reduces uneven refrigerant distribution between heat exchange tubes 36.

In one example, the basic design relationship is a ratio of the first design characteristic to the second design characteristic, that is, the first design characteristic divided by the second design characteristic. The best effect of the distribution of refrigerant in the distribution insert 32 is achieved if the dimensionless design parameters defined by the basic design relationships fall within given predetermined ranges. At least one of the first design characteristic and the second design characteristic is associated with the dispensing insert 32.

The various characteristics of the evaporator 30 are defined as follows:

Dins	inner diameter of dispensing insert 32
		Dman	Inner diameter of manifold 34
Dorifice	Hydraulic diameter of the dispensing orifice 42 of the dispensing insert 32
		Dtube	Hydraulic diameter of heat exchange tube 36
Lins	Length of dispensing insert 32
		Lman	Length of manifold 34
Lorifice	Axial spacing between centers of dispensing orifices 42 of dispensing insert 32
		Ainsert,surf	Outer surface area of the dispensing insert 32
Ainsert,cross	The cross-sectional area of the distribution insert 32, which is in a plane perpendicular to the axis X and is based on the diameter Dins
		Aorifice	The total cross-sectional area of all of the dispensing orifices 42 of the dispensing insert 32
Aman,dia	The cross-sectional area of the manifold 34, in a plane perpendicular to the axis X and based on the diameter Dman
		Aman,long	Cross-sectional area of manifold 34, in the plane of longitudinal axis X
M	Number of heat exchange tubes 36
		N	Number of dispensing orifices 42

By employing these design characteristics within the relationships/ratios defined below, a plurality of dimensionless design parameters may be defined. A list of these design parameters and the desired predetermined ranges of their values is defined as follows:

relationship numbering	Relationships between	Lower limit of	Upper limit of
				1	(Dins/Dman)2	0.02	0.95
2	Aorifice/Ainsert,surf	50	5000
				3	Aorifice/Ainsert,cross	0.01	100
4	Dorifice/Lorifice	0.01	35
				5	(Dorifice 2/Ainsert,surf)/(Dtube 2/Aman,long)	0.01	25
6	[(N×Dorifice)2]/[(M×Dtube)2]	0.1	100
				7	(Dman/Dorifice 2)/(Lins/Dins 2)	0.01	20
8	Dman/Lins	1	1000

Using relationship 1, a characteristic of dispensing insert 32 is the inner diameter D of dispensing insert 32_ins. The relationship is defined as the inner diameter D of the dispensing insert 32_insAnd the inner diameter D of the manifold 34_manAnd then the ratio is squared to define a dimensionless design parameter. The dimensionless design parameter represents the momentum of flow within the distribution insert 32 versus the momentum of flow within the manifold 34 without the distribution insert 32. For optimum performance, the value of the design parameter should be in the range of 0.02 to 0.95.

Using relation 2, scoreThe characteristic of the dispensing insert 32 is the total cross-sectional area A of all of the dispensing orifices 42 of the dispensing insert 32_orificeAnd the outer surface area A of the dispensing insert 32_insert,surf. The relationship is defined as the total cross-sectional area A of all dispensing orifices 42 of the dispensing insert 32_orificeAnd the outer surface area a of the dispensing insert 32_insert,surfWhich defines a dimensionless design parameter. The dimensionless design parameter represents the density of the dispensing orifices 42 of the dispensing insert 32. For optimum performance, the value of the design parameter should be in the range of 50 to 5000.

Using relationship 3, a characteristic of the dispensing insert 32 is the total cross-sectional area A of all of the dispensing orifices 42 of the dispensing insert 32_orificeAnd cross-sectional area A of dispensing insert 32_insert,cross(which is in a plane perpendicular to the axis X and based on diameter). This relationship is defined as the total cross-sectional area A of all of the dispensing orifices 42 of the dispensing insert 32_orificeCross-sectional area a of dispensing insert 32_insert,cross(which is in a plane perpendicular to the axis X and is based on the diameter D_ins) The ratio of (a) to (b). The dimensionless design parameter represents the momentum of flow through the distribution orifice 42 of the distribution insert 32 versus the momentum of flow through the distribution insert 32. For optimum performance, the value of the design parameter should be in the range of 0.01 to 100.

Using relationship 4, the characteristic of the dispensing insert 32 is the hydraulic diameter D of the dispensing orifice 42 of the dispensing insert 32_orificeAnd the center of the dispensing orifice 42 of the dispensing insert 32_orifice. The relationship is defined as the hydraulic diameter D of the dispensing orifice 42 of the dispensing insert 32_orificeAn axial distance L from the center of the dispensing orifice 42 of the dispensing insert 32_orificeWhich defines a dimensionless design parameter. The dimensionless design parameter represents the density of the dispensing orifices 42 of the dispensing insert 32. For optimum performance, the value of the design parameter should be in the range of 0.01 to 35.

Using relationship 5, the dispensing insert 32 is characterized by a dispensing orifice of the dispensing insert 32Hydraulic diameter D of 42_orificeAnd the outer surface area A of the dispensing insert 32_insert,surf. The relationship is defined as a ratio of the first design characteristic to the second design characteristic. A first design characteristic is defined as the hydraulic diameter D of the dispensing orifice 42 of the dispensing insert 32_orificeDivided by the outer surface area a of the distribution insert 32_insert,surf. The second design characteristic is defined as the hydraulic diameter D of heat exchange tube 36_tubeDivided by the cross-sectional area a of the manifold 34_man,long(which is in the plane of the longitudinal axis X). The ratio of the first design characteristic to the second design characteristic determines a dimensionless design parameter. The dimensionless design parameter represents the momentum of flow through heat exchange tubes 36 versus the momentum of flow through distribution orifices 42. For optimum performance, the value of the design parameter should be in the range of 0.01 to 25.

Using relationship 6, the characteristic of the dispensing insert 32 is the hydraulic diameter D of the dispensing orifice 42 of the dispensing insert 32_orificeAnd the number N of dispensing orifices 42. The relationship is defined as a ratio of the first design characteristic to the second design characteristic. A first design characteristic is defined as the number N of distribution orifices 42 multiplied by the hydraulic diameter D of the distribution orifices 42 of the distribution insert 32_orificeAnd then squared. The second design characteristic is defined as the number M of heat exchange tubes 36 multiplied by the hydraulic diameter D of the heat exchange tubes 36_tubeAnd then squared. The ratio of the first design characteristic to the second design characteristic defines a dimensionless design parameter. The design parameter represents the momentum of flow through heat exchange tubes 36 versus the momentum of flow through distribution orifices 42. For optimum performance, the value of the design parameter should be in the range of 0.01 to 100.

Using relationship 7, the characteristic of the dispensing insert 32 is the hydraulic diameter D of the dispensing orifice 42 of the dispensing insert 32_orificeLength L of dispensing insert 32_insAnd inner diameter D of dispensing insert 32_ins. The relationship is defined as a ratio of the first design characteristic to the second design characteristic. A first design characteristic is defined as the inner diameter D of the manifold 34_manDivided by the hydraulic diameter D of the dispensing orifice 42 of the dispensing insert 32_orificeSquare of (d).The second design characteristic is defined by the length L of the dispensing insert 32_insDivided by the inner diameter D of the dispensing insert 32_insIs defined by the square of. The first design characteristic is divided by the second design characteristic to obtain the ratio. The ratio of the first design characteristic to the second design characteristic determines a dimensionless design parameter. The dimensionless design parameter represents the pressure differential across the manifold 34 versus the pressure differential along the manifold 34. For optimum performance, the value of the design parameter should be in the range of 0.01 to 20.

Using relationship 8, a characteristic of the dispensing insert 32 is the length L of the dispensing insert 32_ins. The relationship is defined as the inner diameter D of the manifold 34_manDivided by the length L of the dispensing insert 32_insWhich defines dimensionless design parameters. The dimensionless design parameter represents the distance of travel along the distribution insert 32 compared to the distance through the manifold 34. For optimum performance, the value of the design parameter should be in the range of 1 to 1000.

By calculating the relationship or ratio using at least one fundamental design characteristic of the distribution insert 32 and determining whether the calculated value of the defined dimensionless design parameter falls within a predetermined range of values, it can be determined whether the distribution effect of the distribution insert 32 and the evaporator 30 is optimized.

The foregoing description is only exemplary of the principles of the invention. Many modifications and variations of the present invention are possible in light of the above teachings. However, the preferred embodiments of this invention have been disclosed so that one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason, the following claims should be studied to determine the true scope and content of this invention.

Claims (25)

1. A heat exchanger, comprising:

a plurality of heat exchange tubes;

a manifold; and

a distribution insert at least partially received in the manifold, wherein the distribution insert comprises a plurality of orifices configured to distribute fluid into the manifold for distribution into the plurality of heat exchange tubes,

wherein at least one design characteristic of the distribution insert and another design characteristic of at least one of the distribution insert, the manifold and the plurality of heat exchange tubes are used to determine a basic design relationship, and the basic design relationship defines a design parameter having a value that falls within a determined range of values.

2. The heat exchanger of claim 1, wherein the heat exchanger is an evaporator and the manifold is at least one of an inlet manifold and an intermediate manifold of the evaporator.

3. A heat exchanger as claimed in claim 1 wherein the heat exchanger is a condenser or a reheat heat exchanger and the manifold is an intermediate manifold of the condenser or the reheat heat exchanger.

4. The heat exchange tube of claim 1, wherein the heat exchanger is a microchannel heat exchanger.

5. The heat exchanger of claim 1, wherein the fundamental design relationship is a dimensionless ratio.

6. The heat exchanger of claim 1, wherein the at least one design characteristic of the distribution insert is one of: a length of the distribution insert, a diameter of the distribution insert, a hydraulic diameter of the plurality of orifices of the distribution insert, a separation distance between centers of the plurality of orifices of the distribution insert, a surface area of the distribution insert, a cross-sectional area of the distribution insert, a total cross-sectional area of the plurality of orifices of the distribution insert, and a number of the distribution orifices.

7. The heat exchanger of claim 1, wherein the at least one design characteristic is an inner diameter of the distribution insert and the another design characteristic is an inner diameter of the manifold, and the basic design relationship is defined by a ratio of the inner diameter of the distribution insert to the inner diameter of the manifold, wherein the ratio is squared to define the design parameter.

8. The heat exchanger of claim 7, wherein the range of values for the design parameter is between 0.02 and 0.95.

9. The heat exchanger of claim 1, wherein the another design characteristic is a characteristic of the distribution insert and the at least one design characteristic is a total cross-sectional area of the plurality of distribution orifices of the distribution insert and an outer surface area of the distribution insert, and the basic design relationship is defined by a ratio of the total cross-sectional area of the plurality of distribution orifices of the distribution insert to the outer surface area of the distribution insert, wherein the ratio defines the design parameter.

10. The heat exchanger of claim 9, wherein the range of values for the design parameter is between 50 and 5000.

11. The heat exchanger of claim 1, wherein the another design characteristic is a characteristic of the distribution insert and the at least one design characteristic is a total cross-sectional area of the plurality of distribution orifices of the distribution insert and a cross-sectional area of the distribution insert, and the basic design relationship is defined by a ratio of the total cross-sectional area of the plurality of distribution orifices of the distribution insert to the cross-sectional area of the distribution insert, wherein the ratio defines the design parameter.

12. The heat exchanger of claim 11, wherein the range of values for the design parameter is between 0.01 and 100.

13. The heat exchanger of claim 1, wherein the another design characteristic is a characteristic of the distribution insert and the at least one design characteristic is a hydraulic diameter of the plurality of distribution orifices of the distribution insert and a spacing between centers of the plurality of distribution orifices of the distribution insert, and the basic design relationship is defined by a ratio of the hydraulic diameter of the plurality of distribution orifices of the distribution insert to the spacing between centers of the plurality of distribution orifices of the distribution insert, wherein the ratio defines the design parameter.

14. The heat exchanger of claim 13, wherein the range of values for the design parameter is between 0.01 and 35.

15. The heat exchanger as recited in claim 1 wherein the at least one design characteristic is a hydraulic diameter of the plurality of distribution orifices of the distribution insert and a surface area of the distribution insert, the another design characteristic is a hydraulic diameter of the plurality of heat exchange tubes and a cross-sectional area of the manifold, and the basic design relationship is defined as a first design characteristic divided by a second design characteristic,

wherein the first design characteristic is a ratio of a square of a hydraulic diameter of the plurality of distribution orifices of the distribution insert to an outer surface area of the distribution insert and the second design characteristic is a ratio of a square of a hydraulic diameter of the plurality of heat exchange tubes to a cross-sectional area of the manifold, and the ratio of the first design characteristic to the second design characteristic defines the design parameter.

16. The heat exchanger of claim 15, wherein the range of values for the design parameter is 0.01 to 25.

17. The heat exchanger as recited in claim 1 wherein the at least one design characteristic is a hydraulic diameter of the plurality of distribution orifices of the distribution insert and a number of the plurality of distribution orifices of the distribution insert, the another design characteristic is a number of the plurality of heat exchange tubes and a hydraulic diameter of the plurality of heat exchange tubes, and the fundamental design relationship is defined as a first design characteristic divided by a second design characteristic,

wherein the first design characteristic is defined by the number of the plurality of distribution orifices of the distribution insert multiplied by the hydraulic diameter of the plurality of distribution orifices of the distribution insert and then squared, and the second design characteristic is the number of the plurality of heat exchange tubes multiplied by the hydraulic diameter of the plurality of heat exchange tubes and then squared, and a ratio of the first design characteristic to the second design characteristic defines the design parameter.

18. The heat exchanger of claim 17, wherein the range of values for the design parameter is 0.01 to 100.

19. The heat exchanger of claim 1, wherein the at least one design characteristic is a hydraulic diameter of the plurality of distribution orifices of the distribution insert, a length of the distribution insert, and an inner diameter of the distribution insert, the other design characteristic is a diameter of the manifold, and the fundamental design relationship is defined as a first design characteristic divided by a second design characteristic,

wherein the first design characteristic is a diameter of the manifold divided by a square of a hydraulic diameter of the plurality of distribution orifices of the distribution insert divided by a square of a length of the distribution insert divided by a diameter of the distribution insert, and a ratio of the first design characteristic to the second design characteristic defines the design parameter.

20. The heat exchanger of claim 19, wherein the range of values for the design parameter is 0.01 to 20.

21. The heat exchanger of claim 1, wherein the at least one design characteristic is a length of the distribution insert, the another design characteristic is an inner diameter of the manifold, and the fundamental design relationship is defined as a ratio of the inner diameter of the manifold to the length of the distribution insert, wherein the ratio defines the design parameter.

22. The heat exchanger of claim 21, wherein the range of values for the design parameter is 1 to 1000.

23. A method of designing a heat exchanger, the method comprising the steps of:

determining a range of values;

selecting at least one design characteristic of a distribution insert, wherein the distribution insert comprises a plurality of orifices, at least a portion of the distribution insert is received in a manifold, and fluid can be conveyed through the plurality of orifices and into the manifold for distribution into a plurality of heat exchange tubes; and

determining a fundamental design relationship between the at least one design characteristic of the distribution insert and another design characteristic of at least one of the distribution insert, the manifold, and the plurality of heat exchange tubes, wherein the fundamental design relationship defines a design parameter having a value within a range of the values.

24. The method of claim 23, wherein the basic design relationship is a dimensionless ratio.

25. The method of claim 23, wherein the at least one design characteristic of the dispensing insert is one of: a length of the distribution insert, a diameter of the distribution insert, a hydraulic diameter of the plurality of orifices of the distribution insert, a separation distance between centers of the plurality of orifices of the distribution insert, a surface area of the distribution insert, a cross-sectional area of the distribution insert, a total cross-sectional area of the plurality of orifices of the distribution insert, and a number of the distribution orifices.