HK1145870A1 - Parallel flow heat exchanger with connectors - Google Patents

Abstract

A parallel flow heat exchanger includes a plurality of connector tubes which fluidly interconnect the individual flat heat exchange tubes to a refrigerant delivery member such that the refrigerant flows along the lengths of the connector tubes and then flows in a direction orthogonal thereto to enter the flat heat exchange tubes to thereby provide improved refrigerant distribution thereto. The refrigerant distribution member may be an inlet manifold or an entrance port or a refrigerant distributor. The connector tubes may be connected so as to conduct the flow in parallel or in series, and an orifice may be placed at the entrance end thereof to improve refrigerant distribution.

Description

Parallel flow heat exchanger with connector

Technical Field

The present invention relates generally to air conditioning and refrigeration systems, and more particularly to parallel flow evaporators thereof.

Background

The definition of so-called parallel flow heat exchangers, sometimes also referred to as flat tube heat exchangers, is now widely used in the air conditioning and refrigeration industry and refers to heat exchangers having a plurality of parallel passages between which refrigerant is distributed to flow in an orientation that is substantially perpendicular to the refrigerant flow direction in an inlet manifold and an outlet manifold.

Maldistribution of refrigerant in a refrigerant system evaporator is a well known phenomenon. This phenomenon results in significant evaporator and overall system performance degradation under many operating conditions. Causes of refrigerant maldistribution may include: there are poor flow resistance in the evaporator channels, uneven distribution of air flow over the external heat transfer surfaces, improper orientation of the heat exchanger, or poor design of the manifold and distribution system. Maldistribution is particularly prominent in parallel flow evaporators because of the unique design of such parallel flow evaporators in routing refrigerant to each evaporator circuit. To eliminate or mitigate the effect of this phenomenon on the performance of parallel flow evaporators, many efforts have been made by the skilled artisan, but these efforts have met with little success or have failed at all. The main reasons for this failure are that the proposed technology is either complicated and inefficient or the cost of the solution is prohibitively high.

In recent years, parallel flow heat exchangers, and brazed aluminum heat exchangers in particular, have received much attention and attention, not only in the automotive field, but also in the heating, ventilation, air conditioning and refrigeration (HVAC & R) industry. The main reasons for using the parallel flow technology are the superior performance, high compactness, good structural rigidity and improved corrosion resistance of the parallel flow device. Parallel flow heat exchangers are now being used in both condenser applications and evaporator applications for a variety of product and system designs and configurations. While the use of these evaporators can provide greater advantages and benefits, they are also more challenging and problematic. Refrigerant maldistribution is one of the major concerns and obstacles for implementing this technology in evaporator applications.

As is known, causes of refrigerant maldistribution in parallel flow heat exchangers include: the pressure drop inside the channels and in the inlet and outlet manifolds is different, the design of the manifolds and the distribution system is poor. In the manifold, refrigerant path length differences, phase separation, and gravity are the primary factors contributing to this maldistribution. Inside the heat exchanger channels, variations in heat transfer rate, air flow distribution, manufacturing tolerances and gravity are the main factors. Furthermore, recent performance trends in heat exchangers promote miniaturization of their channels (so-called mini-channels and micro-channels), which further negatively affects the distribution of refrigerant. Because it is extremely difficult to control all of these factors, previous attempts to manage refrigerant distribution, particularly in parallel flow evaporators, have failed.

If the two-phase flow enters the inlet manifold at a relatively high velocity, the liquid phase (droplets) is carried by the momentum of the flow further away from the manifold inlet toward the remote portion of the header. Thus, the channels closest to the manifold inlet receive predominantly the vapor phase and the channels remote from the manifold inlet receive predominantly the liquid phase. On the other hand, if the velocity of the two-phase flow entering the manifold is low, there is not enough momentum to carry the liquid phase along the header. As a result, the liquid phase enters the channels closest to the inlet and the vapor phase proceeds toward the farthest channel. In addition, the liquid and vapor phases in the inlet manifold can separate under the influence of gravity, resulting in similar maldistribution. In either case, maldistribution can quickly develop and manifest itself in the evaporator and cause degradation of overall system performance.

While conventional round tube heat exchangers may be fed individually for each tube or line, flat tube heat exchangers do not have this capability, and efforts to improve refrigerant distribution in such heat exchangers, such as the use of inserts and multiple inlet headers, all make the design more complex and increase manufacturing costs. In addition, since the large diameter manifold is replaced with the small diameter manifold and the connector, the operating pressure may be greatly increased.

Disclosure of Invention

Briefly, in accordance with one aspect of the invention, each flat heat exchange tube of an evaporator is interconnected to a refrigerant conveying member by a connector tube such that two-phase refrigerant flows first from the refrigerant conveying member into the connector tube and then into the each flat heat exchange tube, thereby improving refrigerant flow distribution.

According to another aspect of the invention, the connector tubes are connected to and extend substantially orthogonally from a common inlet manifold.

According to another aspect of the present invention, the connector tube is cylindrical in shape, and the flat heat exchange tube is inserted into a longitudinal groove formed in the connector tube so as to form a T-joint.

According to yet another aspect of the invention, the connector tube has an orifice at one end thereof, such that refrigerant entering the connector tube expands in the process, thereby improving the uniform distribution of refrigerant.

According to another aspect of the invention, each of the connector tubes is fluidly connected to a conventional refrigerant distributor by an inlet tube and directed toward the distributor.

Preferred and other alternative embodiments are shown in the following figures; however, various other modifications may be made to these embodiments and alternative constructions may be devised without departing from the spirit and scope of the present invention.

Drawings

FIG. 1 schematically illustrates the present invention included within a parallel flow evaporator;

FIG. 2 is a side view of the present invention;

FIG. 3 is an end view of the present invention;

FIG. 4 is an enlarged view of a portion of the present invention;

FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. 4;

figures 6A and 6B are front and top views, respectively, of a T-shaped connector;

FIGS. 7A and 7B schematically illustrate another alternative embodiment of the present invention;

FIGS. 8 and 9 schematically illustrate yet another alternative embodiment of the present invention;

FIG. 10 schematically illustrates yet another alternative embodiment of the present invention;

FIG. 11 schematically illustrates yet another alternative embodiment of the present invention;

FIG. 12 schematically illustrates yet another alternative embodiment of the present invention;

FIGS. 13A and 13B schematically illustrate yet another alternative embodiment of the present invention;

FIGS. 14 and 15 schematically illustrate yet another alternative embodiment of the present invention; and

fig. 16 schematically shows a further embodiment of the invention.

Detailed Description

Referring to fig. 1-3, the present invention is shown generally at 10 and is included within a parallel flow heat exchanger 11 including an inlet manifold 12, a plurality of flat heat exchange tubes 13 and an outlet manifold 14.

Each of the plurality of flat heat exchange tubes 13 is fluidly connected to a respective connecting tube, shown respectively as 16, 17, 18 and 19, which is further fluidly connected to the inlet manifold 12.

During operation, two-phase refrigerant flow enters the inlet port 21 of the inlet manifold 12 and flows to both ends of the inlet manifold 12. The refrigerant flow then flows to each connector tube 16, 17, 18 and 19 and then to the corresponding flat heat exchange tube 13, and then the refrigerant flow passes to the outlet manifold 14 and is discharged from the outlet port 22.

This design configuration allows the inlet manifold 12 and the connecting tubes 16-19 to have a sufficiently small diameter, which is advantageous for distributing refrigerant between the flat heat exchange tubes 13.

As shown in fig. 4 and 5, the connector tubes 16, 17 and 18 have a cylindrical cross section, and linear grooves 23, 24 and 26 are formed in the connector tubes, respectively, to receive the corresponding flat heat exchange tubes 13 therein. The extent to which the flat heat exchange tubes 13 penetrate into the respective connector tubes 16, 17 and 18 is a matter of design choice and may be selected so as to have a greater degree of penetration as shown, or these flat heat exchange tubes may also penetrate little or not at all into the connector tubes, so that the ends of the heat exchange tubes 13 are substantially flush with the inner walls of the connector tubes. Alternatively, the flat heat exchange tubes 13 may have different skin depths (penetration depths) that may be selected depending on the location of the inlet port 21 to provide substantially equal inlet refrigerant flow resistance between the heat exchange tubes 13. The flat heat exchange tubes 13 are then secured in place by a process such as welding, furnace brazing, or the like.

As shown in fig. 5, the flat heat exchange tubes 13 may include a plurality of spaced apart ports 27 having any suitable cross-section and having an overall height H and an overall width W. One end 28 of each connector tube, such as connector tube 17, is open and connected to the inlet manifold 12 described above. The other end 29 may be sealed as shown in fig. 5, or it may be interconnected with another connector conduit, as will be described below.

It should be understood that: the relative dimensions of the flat heat exchange tubes 13 and their corresponding connector tubes 16-19 are such that the diameter of the connector tubes is sufficient that the height of the slots 24 will accommodate the height H of the flat heat exchange tubes. Similarly, the length of the connector tubes, i.e., the distance between ends 28 and 29, should be sufficient to accommodate the width W of the heat exchange tubes 13.

Fig. 4 and 5 show the connectors 16, 17 and 18 as pipes having a cylindrical cross-section. It should be understood that: the connector may have an oval, square, rectangular, triangular or any other possible shape. Further, the shape and area of the cross-section may be different along the centerline of the connector.

Fig. 4 and 5 imply that each flat heat exchange tube has one connector. It should be understood that: a plurality of adjacent flat heat exchange tubes may be connected to one connector. In this case, a plurality of grooves must be formed in the connector in order to accommodate a plurality of flat heat exchange tubes.

Further, it may be advantageous to have different sizes of the flat heat exchange tubes. For example, the height or width of the flat heat exchange tubes may vary. So that the corresponding connector has a corresponding slot size that needs to be adjusted to receive different sized flat heat exchange tubes. As one example, a parallel flow heat exchanger may include sections in which the flat heat exchange tubes have different widths to generally accommodate different air flow rates across the sections.

Fig. 4 and 5 show the connectors 16, 17 and 18 as straight pipes. Such connectors are called two-terminal connectors. It should be understood that: the connector may be manufactured as a three-terminal connector, in particular as a T-connector as shown in fig. 6A and 6B. The T-shaped connector has a first side end 101, a second side end 102 and a central end 103. It should also be understood that: each end may have multiple ends. Such connectors are called multi-terminal connectors. Obviously, at least one end of the connector must be in an active state. All remaining ends, if any, are inactive and sealed.

Fig. 6A and 6B show the ends 101, 102 and 103, the centre lines of which lie in one plane and have the shape of the letter T. It should be understood that: the centerlines of the two, three and each end of the multi-end connector can have any possible shape.

Although the outlet header 14 is shown in the drawings as being directly connected to the flat tube channels 13, it should be understood that: connector tubes similar to connector tubes 16-19 may be used to interconnect the flat heat exchange tubes 13 with the outlet manifold 14.

The above embodiments show the various connector tubes 16-19 (which are two-ended connectors) arranged in a parallel relationship and extending orthogonally from the inlet manifold 12. The figure also shows: the connector tubes are connected together so that the refrigerant flows therein are in parallel. It should be understood that: the connector tubes 16-19 may be interconnected in serial flow relationship and may further be connected directly to the inlet port without the need for the inlet manifold 12. Fig. 7A and 7B illustrate such an embodiment, as shown, where elbow 28 interconnects the ends of connector tubes 16 and 17, elbow 32 interconnects the ends of connector tubes 17 and 18, and elbow 33 interconnects the ends of connector tubes 18 and 19.

The flow of refrigerant then enters the inlet port 34 through the connector tube 16, one of the flat heat exchange tubes 13, the elbow 31, the connector tube 17, the other of the flat heat exchange tubes 13, the elbow 32, the connector tube 18, the elbow 33, and the connector tube 19. Finally, the refrigerant flows out of the outlet port 36.

Fig. 7A and 7B show a heat exchanger having T-connectors 16, 17, 18 and 19 on one end of the heat transfer pipe 13 and T-connectors 116, 117, 118 and 119 on the other end of the heat transfer pipe. The connectors each have one active end and two inactive ends. To the end, any of the connector types described may be used.

Fig. 8 and 9 show a heat exchanger with one line and four channels, it being understood that: each line may have any number of channels as appropriate for the particular application. Further, it is also appropriate to have a plurality of lines.

Figure 10 shows a heat exchanger with three identical parallel circuits. Each line has its own inlet port 34a, 34b and 34c and its own outlet port 36a, 36b and 36c, respectively. In the embodiment shown in fig. 10, the refrigerant flow is generally downward as it enters at the top and flows downward toward the bottom. However, it is also possible to have the opposite generally upward arrangement (refrigerant entering at the bottom and flowing upward to the top) or a mixed flow arrangement. The heat exchanger design shown in fig. 10 provides two end connectors, 116, 16, 17, 117, 118, 18, 19 and 119 for the top line, and each connector has one active end (active end) and one inactive end (inactive end).

The heat exchanger design shown in fig. 11 illustrates a three-circuit, four-pass heat exchanger having T-connectors 116, 16, 17, 117, 118, 18, 19, and 119, each having one active end and two inactive ends.

In the embodiments shown in fig. 10 and 11, the number of lanes in each line is the same. It should be understood that: the number of lanes in each lane may also be different.

The heat exchanger described above can operate as a condenser and as an evaporator. Typically, the condenser has vapor at the inlet and liquid at the outlet. Because of the density difference between the liquid and vapor phases, condensers are generally more efficient if they have more inlets and fewer outlets. FIG. 12 shows a three-circuit heat exchanger having three inlets 34a, 34b and 34 c; an outlet 36; t-connectors 116, 16, 17, 117, 118, 18, 119; and a four-port connector 19 having two sealed side ends. Fig. 13A and 13B show a similar heat exchanger in which the four-port connector 19 has one sealed side end.

The heat exchanger shown in fig. 12, 13A and 13B may be used as a component of a heat pump system and operate as a condenser and an evaporator. The evaporator has a two-phase refrigerant at its inlet and typically has a vapor at its outlet. Because of the density difference between the liquid and vapor phases, the evaporator is more efficient if it has fewer inlets and more outlets. Since the operation as a condenser and the operation as an evaporator are opposite in terms of the refrigerant flow direction, the embodiment shown in fig. 12, 13A and 13B should have an appropriate number of inlets and outlets in order to implement the two operation modes.

A heat exchanger operating as an evaporator should have means for distributing two-phase refrigerant. Fig. 14 and 15 show another embodiment applicable to evaporators in which an inlet manifold is not used, wherein a conventional distributor 40 is fluidly connected to each of the connector pipes 16-19 by small diameter distributor pipes 38, 39, 41 and 42, respectively. In this case, an expansion device (not shown) is disposed upstream of the distributor 40, such that a two-phase refrigerant flow flows from the distributor 40 to each of the small diameter distributor tubes 38, 39, 41 and 42. The two-phase refrigerant flow then flows to each of the connector tubes 16-19 and is further distributed in the manner described above.

Fig. 14 and 15 show that: the number of distributor pipes corresponds to the number of flat heat exchange pipes. It should be understood that: typically, each line may have a number of channels, and the number of distributors corresponds to the number of channels. Furthermore, as with the previous connector tubes, a distributor may optionally be used for multiple lines.

Fig. 16 shows a variation of the embodiment shown in fig. 1-5, in which, unlike the arrangement of an open-ended connection between the connector tubing 17 and the inlet manifold 12 shown in fig. 5, both ends 28 and 29 of the connector tubing 19 are closed, and the orifice 42 is provided in the end 28 as shown. Thus, as refrigerant passes from the inlet manifold 12 through the orifice 42, expansion occurs to supply refrigerant of lower pressure and temperature in two phases to the connector tubes 19. The refrigerant flow from this point is the same as that described above. It should be understood that: the orifice 42 may have a plurality of orifices arranged in parallel and/or in series.

As shown in fig. 16, the number of orifices 42 (or a plurality thereof) corresponds to the number of flat heat exchange tubes. It should be understood that: typically, each line may have a plurality of channels, and the number of orifices 42 (or a plurality thereof) corresponds to the number of lines. Further, one orifice 42 (or multiple orifices) may optionally be used for multiple lines.

There are two possible designs. In one configuration, the manifold 12 operates as a receiver and the orifice 42 along the manifold 12 operates as an expansion device, thereby allowing isenthalpic expansion from the condenser pressure to the evaporator pressure. Another arrangement includes an expansion device attached to the manifold 12. The expansion device allows isenthalpic expansion from the condenser pressure to a pressure higher than the evaporator pressure and lower than the condenser pressure. The orifice 42 acts as a refrigerant distributor for the two-phase refrigerant, thereby allowing one, two or more expansions from the pressure downstream of the expansion device to the evaporator pressure.

In addition to the advantages described above, the design features of the present invention allow for the use of substantially wider heat exchange tubes, reduced fin density and/or increased fin height without compromising the performance characteristics and cost of the heat exchanger.

It should be understood that: the present invention is intended for use with heat exchangers that may have a horizontal, vertical, or inclined orientation. That is, while the flattened heat exchange tubes as shown have a horizontal orientation, the present invention may also be used with flattened heat exchange tubes having a vertical orientation and an inclined orientation.

Although certain preferred embodiments of the present invention have been disclosed in detail herein, it should be understood that: various modifications may be made in the construction without departing from the spirit of the invention or the scope of the following claims.

Claims (24)

1. A parallel flow heat exchanger of the type having a plurality of flat heat exchange tubes arranged in a generally parallel relationship, said parallel flow heat exchanger comprising:

a plurality of connector tubes, each connector tube being connected in fluid communication to at least one tube of the plurality of flat heat exchange tubes for conducting a flow of refrigerant therein; and

a refrigerant transport member for transporting refrigerant to each of the plurality of connector tubes,

wherein each tube of the plurality of connector tubes includes a linear slot into which a flat heat exchange tube is inserted, and further wherein the flat heat exchange tube extends inside the connector tube.

2. A parallel flow heat exchanger as set forth in claim 1 wherein said flat heat exchange tubes project into respective connector tubes to a depth that is not uniform.

3. A parallel flow heat exchanger as set forth in claim 1 wherein said connector tubes have a cylindrical shape and a diameter greater than the height of said flat heat exchange tubes.

4. A parallel flow heat exchanger as set forth in claim 1 wherein said connector tubes have a length greater than a width of said flat heat exchange tubes.

5. A parallel flow heat exchanger as set forth in claim 1 wherein said refrigerant conveying member comprises an inlet manifold.

6. A parallel flow heat exchanger as set forth in claim 5 wherein said inlet manifold is connected at one end of said connector tube.

7. A parallel flow heat exchanger as set forth in claim 1 wherein adjacent connector tubes are interconnected at their ends in fluid communication such that said refrigerant flows in series through said plurality of connector tubes.

8. A parallel flow heat exchanger as set forth in claim 1 wherein said refrigerant conveying members comprise refrigerant distributors fluidly connected to respective connector tubes.

9. A parallel flow heat exchanger as set forth in claim 1 further comprising a closed end disposed in each of said plurality of connector tubes, said closed end having an orifice disposed therein such that refrigerant from said refrigerant conveying member flows first through said orifice as it expands into the respective connector tube.

10. A parallel flow heat exchanger as set forth in claim 1 further comprising an outlet manifold fluidly connected at an end of each of said flat heat exchange tubes.

11. A parallel flow heat exchanger as set forth in claim 1 wherein at least one dimension of said flat heat exchange tubes is different for said plurality of said flat heat exchange tubes.

12. A parallel flow heat exchanger as set forth in claim 11 wherein said dimension of said flat heat exchange tubes is at least one of a tube width and a tube height.

13. A method of promoting uniform refrigerant flow into a plurality of parallel flat heat exchange tubes, said method comprising the steps of:

providing a plurality of connector tubes, each connector tube being connected in fluid communication to at least one of the parallel flat heat exchange tubes for conducting a flow of refrigerant therein; and

providing a refrigerant flow delivery apparatus for delivering refrigerant to each of the plurality of parallel flat heat exchange tubes, and the method includes the step of providing a linear slot in each of the plurality of connector tubes into which a flat heat exchange tube is inserted, and further wherein each of the flat heat exchange tubes extends inside a respective connector tube of the plurality of connector tubes.

14. The method as set forth in claim 13, wherein said parallel flat heat exchange tubes project into respective connector tubes to a depth that is not uniform.

15. The method of claim 13, wherein the connector tubes have a cylindrical shape and have a diameter greater than a height of the parallel flat heat exchange tubes.

16. The method as set forth in claim 13, wherein said connector tubes have a length greater than the width of said parallel flat heat exchange tubes.

17. The method of claim 13, wherein the refrigerant flow delivery device comprises an inlet manifold.

18. The method of claim 17, wherein the method further comprises the step of connecting the inlet manifold to an end of the connector tube.

19. The method of claim 13, wherein the method further comprises the step of interconnecting adjacent connector tubes in fluid communication at ends thereof such that the refrigerant flows serially through the plurality of connector tubes.

20. The method of claim 13, wherein the refrigerant flow delivery device comprises a refrigerant distributor fluidly connected to a respective connector tube.

21. The method of claim 13, wherein the method further comprises the step of providing a closed end in each of the plurality of connector tubes, the closed end having an orifice disposed therein such that refrigerant from the refrigerant flow delivery device flows through the orifice as it expands into the respective connector tube.

22. The method as set forth in claim 13 further including the step of connecting an outlet manifold in fluid communication to an end of each of said parallel flat heat exchange tubes.

23. The method as set forth in claim 13 wherein at least one dimension of said parallel flat heat exchange tubes is different for said plurality of said parallel flat heat exchange tubes.

24. The method as set forth in claim 23 wherein said dimension of said parallel flat heat exchange tubes is at least one of a tube width and a tube height.