Patent Application
20070284086
This invention relates to heat exchangers, and more specifically, to improved transition assemblies for heat exchangers; as well as methods of making a heat exchanger and transition assembly.
Many heat exchangers in use today, as, for example, evaporators and condensers for stationary refrigeration systems, are based on a construction that includes fluid connections to external flow paths for at least one of the fluids passing through the heat exchanger, such as, for example, refrigerant. Generally, a fluid to be heated and/or cooled travels from an external source through an external flow path to the heat exchanger. Once the fluid travels through the heat exchanger, the fluid exits the heat exchanger to another external flow path. Connecting the external flow paths to the heat exchanger can be done by brazing if the flow path and heat exchanger are of materials that are easily brazed to each other, however if not, fluid connections in the form of transition assemblies are utilized to connect the external sources to the inlet and outlet of the heat exchanger.
Heat exchangers are oftentimes manufactured from specially selected materials to increase the rate of heat transfer in the heat exchanger. However, the materials selected for the heat exchanger may not be the same material as the external flow paths and/or transition assemblies. If different materials are selected for the components, the components may expand and contract at different rates. This effect becomes especially important during the assembly of the heat exchanger and transition assemblies.
Specifically, the transition assemblies are generally brazed to the heat exchanger through aprocess of subjecting the components to sufficient thermodynamic conditions to melt the braze material and connect the components. If the heat exchanger and transition assemblies are manufactured from materials such as aluminum and stainless steel, the aluminum components will expand more than the stainless steel components. Therefore, if the components are not properly oriented or do not have fixtures retaining the components together, they may fall apart during the brazing process. Specifically, gravity may cause one of the components to fall out of the other component if the components do not have a correct orientation. This method also has a similar drawback in that the brazing material may not stay in a desired location during the brazing process if the components do not have a correct orientation.
In accordance with one form, a transition assembly for connecting a heat exchanger to an external flow path is provided. The transition assembly includes a fluid connection tube extending from the heat exchanger. The fluid connection tube includes a body extending from the heat exchanger having a first internal cross-sectional area and an extended end having a second internal cross-sectional area which is larger than the first internal cross-sectional area. The transition assembly also includes a transition tube having a transition end, a coupling end and a body portion extending between the transition end and the coupling end. The body portion has a first external cross-sectional area and the transition end has a second external cross-sectional area which is larger than the first external cross-sectional area The transition end fits substantially within the extended end and an edge portion of the extended end is deformed to retain the transition end within the extended end.
In one form, a heat exchanger is provided. The heat exchanger includes a pair of spaced, generally parallel headers, a plurality of spaced, generally parallel tubes extending between and in fluid communication with the interior of the headers, and a transition assembly. The transition assembly includes a fluid connection tube and a transition tube where the transition tube extends from an end or side of one of the headers. The fluid connection tube includes a body extending from the heat exchanger having a first internal cross-sectional area and an extended end having a second internal cross-sectional area which is larger than the first internal cross-sectional area. The transition tube has a transition end, a coupling end and a body portion extending between the transition end and the coupling end. The body portion has a first external cross-sectional area and the transition end having a second external cross-sectional area which is larger than the first external cross-sectional area. The transition end fits substantially within the extended end. An edge portion of the extended end is deformed to retain the transition end within the extended end.
In one form, the fluid connection tube and the transition tube are brazed together with brazing material.
According to one form, the brazing material is located on the interior of the fluid connection tube.
In accordance with one form, the fluid connection tube is made from aluminum and the transition tube is made from stainless steel.
In one form, the edge portion is deformed in only one location to retain the transition end within the extended end.
According to one form, the entire edge portion is deformed to retain the transition end within the extended end.
In accordance with one form, the body portion has a third internal cross-sectional area and the coupling end has a fourth internal cross-sectional area which is larger than the third internal cross-sectional area.
According to one form, the cross-sectional areas are circular.
In one form, a method manufacturing a transition assembly for connecting a heat exchanger to an external flow path is provided. The assembly includes a fluid connection tube and a transition tube. The fluid connection tube includes a body and an extended end. The transition tube has a transition end, a coupling end and a body portion extending between the transition end and the coupling end. The method including the steps of:
inserting the transition end within the extended end of the fluid connection tube such that the transition end is substantially enclosed within the extended end;
deforming an edge of the extended end to retain the transition end within the extended end; and
brazing the assembly to create a substantially fluid tight connection between the fluid connection tube and the transition tube.
In one form, the method further includes the step of inserting a brazing material within the extended end of the fluid connection tube prior to inserting the transition end.
According to one form, the step of inserting a brazing material includes inserting a brazing ring sized to fit within the extended end.
In accordance with one form, the step of brazing the assembly is carried out via controlled atmosphere brazing.
In one form, the transition tube is oriented in a downward direction relative to a gravitational force during the step of brazing the assembly.
According to one form, the method further includes the steps of providing the fluid connection tube with the body having a first internal cross-sectional area and the extended end having a second internal cross-sectional area and providing the transition tube with the body portion having a first external cross-sectional area and the transition end having a second external cross-sectional area which is larger than the first external cross-sectional area.
In one form, the cross-sectional areas are circular.
In one form, the method further includes the step of inserting an end of an external flow path within the coupling end of the transition tube to create a substantially fluid tight connection between the transition tube and the external flow path.
Other objects, advantages, and features will become apparent from a complete review of the entire specification, including the appended claims and drawings.
The present invention will be described hereinafter as a condenser or an evaporator for a stationary refrigeration system. However, it should be understood that the invention is applicable to condensers used in other contexts, for example, a condenser for a vehicle. The invention is also useful in any of the many other types of heat exchangers that utilize transition joints or assemblies to connect the heat exchanger to external fluid flow paths, such as stainless steel or copper conduits. Accordingly, no limitation to any particular use is intended except insofar as expressed in the appended claims.
Referring to
Between the spaced tubes 14, and between the endmost tube 14 and an adjacent one of the side plates 18,20 are conventional serpentine fins 22, but could be any other suitable fin, including plate-type fins. As is well known, the fins 22 may be formed of a variety of materials. Typical examples are aluminum, copper and brass. However, other materials can be used as well depending upon the desired strength and heat exchange efficiency requirements of a particular application.
In a highly preferred embodiment of the invention, all of the just described components, with the possible exception of the tanks 16 which may be formed of plastic, are formed of aluminum or aluminum alloy and are braze clad at appropriate locations so that an entire assembly is illustrated in
The heat exchanger also includes two transition assemblies 30 and 32. The components and operation of the transition assemblies 30 and 32 can be seen in more detail in the embodiments illustrated in
Specifically, referring to
The transition assembly 30 also includes a transition tube 50. The transition tube 50 includes a transition end 52, a coupling end 54 and a body portion 56 extending between the transition end 52 and the coupling end 54. The body portion 56 has a first external cross-sectional area, which as illustrated in
While the above description makes reference to inner and outer diameters regarding the respective cross-sectional areas, which will often be preferred, it should be understood that other shapes are also contemplated. Therefore, the cross-sectional areas are not limited to the diameters of the respective ends. For example, the ends may take the form of ovals or other shapes and thus, the ends will not have constant diameters, but will still have a measurable cross-sectional area for the respective pieces.
Furthermore, in one preferred embodiment, the outer diameter OD2 of the transition end 52 is substantially the same as the internal diameter ID2 such that the transition end 52 fits snugly within the extended end 44.
Regardless of the shape, the transition end 52 and the extended end 44 will be sized and shaped such that the transition end 52 fits substantially within the extended end 44. In this position, and edge portion 60 of the extended can be deformed to retain the transition end 52 within the extended end 44. The edge portion 60 is shown in
Specifically, referring to
The transition assembly 30 preferably includes brazing material to provide a fluid tight connection between the fluid connection tube 40 and the transition tube 50. The brazing material may be located on the outside of both of these tubes 40 and 50 or in a preferred embodiment, located on the interior of the fluid connection tube 40. In a highly preferred embodiment, as illustrated in
It should be understood by those skilled in the art that the extended end 44 and the transition end 52 maybe manufactured using conventional techniques. For example, one technique known in the art is called swaging whereby the ends are bent and/or shaped using known tools and procedures. Other suitable methods of forming the ends are also contemplated such as by brazing or welding different sized pieces of tubing to the respective heat exchanger and transition tubes. It should also be understood that the coupling end 54 of the transition tube 50 may also be shaped similarly to the other ends, such as illustrated in
The coupling end 54 is utilized to connect the transition assembly to an external flow path 70, as illustrated in
The fluid connection tube 40, transition tube 50 and the external flow path 70 may all be made of conventional materials known by those skilled in the art. In one highly preferred embodiment, the fluid connection tube 40 is aluminum, the transition tube 50 is stainless steel and the external flow path 70 is copper.
During the assembly, the transition end 52 is inserted within the extended end 44 of the fluid connection tube 40 such that the transition end is substantially enclosed within the extended end 44, as illustrated in
In one form, the tubes 40,50 are brazed together. This can be accomplished through the use of brazing material inserted within the fluid connection tube 40 or located outside of the fluid connection tube 40. In one preferred embodiment, the braze ring 64 is inserted into the fluid connection tube 40 and the transition assembly 30 is subjected to sufficient thermodynamic conditions to melt the braze ring and create a substantially fluid tight connection between the fluid connection tube 40 and the transition tube 50. In one highly preferred embodiment, the brazing is accomplished utilizing controlled atmosphere brazing.
In one embodiment, the ends 44 and 52 may be sized and shaped such that the transition end 52 sandwiches the braze ring 64 between the transition end 52 and the interior of the extended end 44 prior to entering the body 42 of the fluid connection tube 40. Therefore, once the extended end 44 is deformed, the braze ring 64 and the transition end will not substantially move regardless of the orientation of the transition assembly 30 and the materials used therein.
Typically, during the brazing process, if different materials are used for each tube, the tubes will expand and contract at different rates and in different amounts. Therefore, it may be possible for the heat exchanger end to expand more than the transition end. If the present transition assembly were not used, the fluid connection tube 40 and transition tube 50 may separate. The separation may be likely in a conventional assembly wherein gravity causes the transition tube to fall out of the fluid connection tube. However, the present assembly permits the tube to be oriented in any manner while minimizing the likelihood the tubes will separate. Additionally, the transition assembly may be preassembled prior to connection to the fluid connection tube.
For example, referring to
