The present invention relates to heat exchangers and, more particularly, to heat exchangers such as engine cooling radiators, charge air coolers, condensers, and the like, in which high stresses in the area of the tube-to-header joint due to temperature fluctuations lead to failure at or below the tube-to-header joint.
Heat exchangers such as engine cooling radiators, charge air coolers, oil coolers, and the like, typically consist of an inlet tank (or manifold) and an outlet tank (or manifold); a core section between the tanks with inlet and outlet headers connected to the tanks and with multiple fluid tubes running from the inlet header to the outlet header, with cooling fins attached between the tubes; and structural side pieces, one on each side, connected to the inlet and outlet tanks. These side pieces often provide attachments for mounting the heat exchanger.
Each of the fluid tubes is inserted into an opening in the wall of the inlet and outlet headers, respectively, and sealed to form a tube-to-header joint. During operation of the heat exchanger, the fluid-carrying tubes are subject to repeated expansion and contraction as the tubes are alternately heated and cooled, resulting in great stress in the area of the tube-to-header joints as the expanding and contracting tubes try to move the inlet and outlet headers, which are connected to the inlet and outlet tanks, which are restrained from movement by the structural side pieces.
As a result of the expanding and contracting tubes trying to move the immovable headers and tanks, the number one cause of failure of heat exchangers in service is failure of the outer tube-to-header joints or of the tubes adjacent to these joints. Much design effort has been expended in attempts to solve this problem, with examples including heat exchangers with resilient tube-to-header joints which provide sealing between the tubes and headers but allow for relative motion between the two without the build-up of high stresses. Some heat exchanger designs use special grommets in the tube-to-header joint, while others have included headers with molded silicone rubber connecting the header plate to metal inserts which become soldered to the tubes. Another approach to the problem has been to seal the tubes to the headers with molded-in-place room temperature vulcanization (RTV) silicone rubber, which provides both sealing and resiliency. All of these approaches add considerable cost to the heat exchanger over the cost of standard rigid tube-to-header joints.
Therefore, a need exists for a means to prevent end tube-to-header failures with a minimum expenditure of cost, material and labor, while preserving heat exchanger thermal performance.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide an improved system and method for sealing tube-to-header joints in heat exchangers which allows for relative motion between the tube and header without the build-up of high stresses.
It is another object of the present invention to provide a system for resilient sealing of heat exchanger tube-to-header joints by means of an O-ring seal.
It is another object of the present invention to provide a system for sealing tube-to-header joints in heat exchangers which provides for easy installation of O-rings at the tube-to-header joints.
A further object of the invention is to provide a system for sealing tube-to-header joints in heat exchangers which does not require close-tolerance machined O-ring grooves.
It is yet another object of the present invention to provide an improved system for sealing tube-to-header joints in heat exchangers which does not require brazing at the tube-to-header joint.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The above and other objects, which will be apparent to those skilled in the art, are achieved in the present invention which is directed to a tube-to-header sealing system for a heat exchanger, comprising a first header plate having a wall with a plurality of openings therein, the first header plate including a continuous depression along the circumference of each of the first header plate openings, each depression forming one-half of an O-ring groove; a plurality of O-rings, each of the plurality of O-rings positioned in an O-ring groove; and a second header plate having a wall with a plurality of openings therein, the second header plate including a continuous depression along the circumference of each of the second header plate openings, each depression forming the other half of the O-ring groove. The second header plate is secured to the first header plate such that the first header plate plurality of openings are aligned with the second header plate plurality of openings, thereby trapping each of the plurality of O-rings in O-ring grooves, and the first and second header plates form a header. A plurality of spaced-apart tubes, each having a tube end secured in an opening in the wall of the header to form a tube-to-header joint, are expanded outwardly to provide sufficient O-ring deformation to obtain a seal.
The second header plate may be secured to the first header plate by spot-welding. The plurality of O-rings may be assembled to the first header plate in one or more sheets, and the sheet or sheets may include at least one hole located where the first and second header plates are spot-welded together. Each of the first and second header plates may include shallow dimples correspondingly positioned with the O-ring sheet at least one hole to increase contact between the first and second header plates during spot-welding.
In another aspect, the present invention is directed to a heat exchanger, comprising a first header plate having a wall with a plurality of openings therein, the first header plate including a continuous depression along the circumference of each of the first header plate openings, each depression forming one-half of an O-ring groove; a plurality of O-rings, each of the plurality of O-rings positioned in an O-ring groove; and a second header plate having a wall with a plurality of openings therein, the second header plate including a continuous depression along the circumference of each of the second header plate openings, each depression forming the other half of the O-ring groove. The second header plate is secured to the first header plate such that the first header plate plurality of openings are aligned with the second header plate plurality of openings, thereby trapping each of the plurality of O-rings in O-ring grooves, and the first and second header plates form a header. A plurality of spaced-apart tubes, each having a length with a midpoint in the length of the tube and having a tube end secured in an opening in the wall of the header to form a tube-to-header joint, are expanded outwardly to provide sufficient O-ring deformation to obtain a seal. A plurality of outer fins are attached between the plurality of tubes and centered about the midpoint in the length of the tubes, the outer fins having ends spaced from the tube-to-header joint to form a free-of-fin area extending therebetween. The plurality of outer fins are capable of transferring heat between a fluid passing through the plurality of tubes and the exterior of the outer fins.
The second header plate may be secured to the first header plate by spot-welding. The plurality of O-rings may be assembled to the first header plate in one or more sheets, and the sheet or sheets may include at least one hole located where the first and second header plates are spot-welded together. Each of the first and second header plates may include shallow dimples correspondingly positioned with the O-ring sheet at least one hole to increase contact between the first and second header plates during spot-welding.
In yet another aspect, the present invention is directed to a method of sealing a tube-to-header joint for a heat exchanger, comprising the steps of: providing a first header plate having a wall with a plurality of openings therein, the first header plate including a continuous depression along the circumference of each of the first header plate openings, each depression forming one-half of an O-ring groove; providing a plurality of O-rings, each of the plurality of O-rings positioned in an O-ring groove; and providing a second header plate having a wall with a plurality of openings therein, the second header plate including a continuous depression along the circumference of each of the second header plate openings, each depression forming the other half of the O-ring groove. The method includes securing the second header plate to the first header plate such that the first header plate plurality of openings are aligned with the second header plate plurality of openings trapping each of the plurality of O-rings in O-ring grooves, the first and second header plates forming a header; providing a plurality of spaced-apart tubes having a tube end capable of being secured in an opening in the wall of the header to form a tube-to-header joint; inserting the plurality of tube ends into the openings in the wall of the header to form a tube-to-header joint; and expanding each of the tubes outwardly to provide the necessary O-ring deformation required to obtain a seal.
The step of securing the second header plate to the first header plate may comprise spot-welding. The plurality of O-rings may be assembled to the first header plate in one or more sheets, and the sheet or sheets may include at least one hole located where the first and second header plates are spot-welded together. Each of the first and second header plates may include shallow dimples correspondingly positioned with the O-ring sheet at least one hole to increase contact between the first and second header plates during spot-welding.
In still another aspect, the present invention is directed to a method of securing a first fixture to a second fixture, comprising the steps of: providing a first fixture having a plurality of spaced openings therein; providing a sheet of O-rings including a plurality of O-rings spaced by tabs to correspond to a distance between each spaced opening; assembling the sheet of O-rings to the first fixture without severing the tabs such that each of the plurality of O-rings is positioned around one of the spaced openings in the first fixture; and securing the first fixture to the second fixture such that the first fixture plurality of openings are aligned with the second fixture plurality of openings trapping each of the plurality of O-rings in O-ring grooves and forming a seal.
The first fixture may be a first header plate for a heat exchanger core, the first header plate including a continuous depression along the circumference of each of the first header plate openings, each depression forming one-half of the O-ring groove, and the second fixture may be a mating header plate for the heat exchanger core, the mating header plate including a continuous depression along the circumference of each of the mating header plate openings, each depression forming the other half of the O-ring groove. The first header plate and mating header plate may be secured to form a header for the heat exchanger core.
The method may further include the steps of: providing a plurality of spaced-apart tubes having a tube end capable of being secured in an opening in the header to form a tube-to-header joint; inserting the plurality of tube ends into the openings in the header to form tube-to-header joints; and expanding each of the tubes outwardly to provide the necessary O-ring deformation required to obtain a seal.
The features of the invention believed to be novel and the elements characteristic of the invention are set forth with particularity in the appended claims. The figures are for illustration purposes only and are not drawn to scale. The invention itself, however, both as to organization and method of operation, may best be understood by reference to the detailed description which follows taken in conjunction with the accompanying drawings in which:
In describing the embodiments of the present invention, reference will be made herein to
Air-cooled heat exchangers such as engine cooling radiators, charge air coolers, oil coolers, and the like, typically consist of an inlet tank (or manifold) and an outlet tank (or manifold); a core section between the tanks with inlet and outlet headers connected to the tanks and with multiple fluid tubes running from the inlet header to the outlet header, with cooling fins attached between the tubes; and structural side pieces, one on each side, connected to the inlet and outlet tanks to provide structural strength to the assembly. These side pieces often provide attachments for mounting the heat exchanger to a vehicle or other structure and further act to prevent the inlet and outlet tanks from moving during operation. The cooling fins are attached between the structural side pieces and the outermost tubes, as well as between adjacent tubes, and are positioned such that the fins are centered around a midpoint in the length of the fluid-carrying tubes, with a fin-free area adjacent the header portion of the inlet and outlet tanks. The region between the end of the cooling fins and the header is known as the “free-of-fin” area. The free-of-fin area begins where the cooling fins end.
During operation of the heat exchanger, heated fluid enters the inlet tank, flows through the core tubes to the outlet tank, and is cooled while passing through the tubes by ambient cooling air passing over the fins. The heated fluid increases the temperature of the tubes, causing them to expand in length. When the system is shut down, the tubes cool and contract. This expansion and contraction of the tubes tries to increase and decrease the distance between the top and bottom headers, which are attached to the top and bottom tanks. However, the structural side pieces often restrain the tanks from moving, resulting in great stress at the tube-to-header joints as the expanding and contracting tubes try to move the immovable tanks. The result is high stresses in the area of the tube-to-header joint. As a result of the expanding and contracting tubes trying to move the immovable tanks, the number one cause of failure of heat exchangers in service is failure of the outer tube-to-header joints or the tubes adjacent to these joints. In units in which the tube-to-header joint is soldered, this usually results, in time, in failure of the tube-to-header joint. In units in which the tube-to-header joint is made by brazing or welding, and is therefore much stronger than a soldered joint, the eventual failure is a break in the tubing just below the tube-to-header joint in the free-of-fin area.
The present invention is directed to a system and method for sealing the tube-to-header joints in heat exchangers with O-rings which does not require close-tolerance machined O-ring grooves. The system consists of producing by stamping two mating header plates for each header. Each header plate includes a plurality of clearance holes for heat exchanger core tubes to pass through, and around each clearance hole is a depression forming one half of an O-ring groove. O-rings are assembled into these depressions, and the mating header plate is placed on top of the lower plate and secured, thereby trapping the O-rings in their O-ring grooves. The assembled header is then slid over the tube ends of the heat exchanger core to its required location, either manually or through automation. After the header is fitted over the tube ends, the tubes are then expanded internally by mandrels to provide the necessary O-ring deformation required to obtain a seal. In service, the resiliency of the O-ring seal allows for expansion and contraction of the tubes without the build-up of high stresses at the tube-to-header joint.
The present invention is applicable to many types of heat exchangers, however because the tubes of a charge air cooler (or intercooler) tend to be much larger in cross-section than those of radiators or condensers, the description used herein will primarily refer to application in a charge air cooler.
Certain terminology is used herein for convenience only and is not to be taken as a limitation of the invention. For example, words such as “upper,” “lower,” “left,” “right,” “horizontal,” “vertical,” “upward,” and “downward” merely describe the configuration shown in the drawings. For purposes of clarity, the same reference numbers may be used in the drawings to identify similar elements.
Referring now to
As shown in
In operation, heated fluid enters the inlet tank 100, flows through the core tubes 110 to the outlet tank 200, and is cooled while passing through the tubes 110 by ambient cooling air passing over the outer fins 120. The heated fluid increases the temperature of the tubes 110, causing them to expand in length. When the system is shut down, the tubes 110 cool and contract. The thermal expansion and contraction of the tubes 110 is represented in
The outermost tube-to-header joint 104 is subject to repeated stress during operation of the heat exchanger, and therefore is at the greatest risk of failure. In heat exchanger units wherein the tube-to-header joint is brazed or welded, and therefore stronger than a soldered joint, the eventual failure is typically a break in the tubing just below the tube-to-header joint in the free-of-fin area. The present invention provides an improved heat exchanger assembly and is directed to a tube-to-header sealing method and system which provides for sealing of the tubes to the headers while allowing for expansion and contraction of the tubes in service by means of a resilient O-ring seal, without the build-up of high stresses in the critical portion of the tube including the free-of-fin area along the tube between the point where the outer fins end and where the tube passes through, and is joined to, the header 102.
As shown in
Referring to
In an embodiment, the O-rings may be assembled either individually or in one or more sheets. To minimize assembly labor, the O-rings 310 may be assembled in a thin sheet 320, as shown in
In an assembled header, each O-ring is positioned in its respective O-ring groove 318 and trapped therein by the mating header plates, whether the O-rings have been assembled individually (
As shown in
Thus the present invention achieves one or more of the following advantages. The present invention provides an improved system and method for sealing tube-to-header joints in heat exchangers which allows for relative motion between the tube and header without the build-up of high stresses. The sealing system provides resilient sealing of heat exchanger tube-to-header joints by means of an inexpensive O-ring seal, as compared to expensive custom grommets or special molded silicone headers. The sealing system requires no close-tolerance machined O-ring grooves, and provides for easy installation of the O-rings, either individually or in sheets. The thickness of the mating header halves can be selected to provide the required total header strength to meet application requirements, and the space between the mating header halves does not require brazing to be sealed from the heat exchanger fluids, as this is accomplished by the O-ring tube-to-header seals. In service, the resiliency of the O-ring seal allows for expansion and contraction of the tubes without the build-up of high stresses at the tube-to-header joint, and prolongs the life of the heat exchanger unit while maintaining heat exchanger thermal performance.
While the present invention has been particularly described, in conjunction with specific embodiments, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. It is therefore contemplated that the appended claims will embrace any such alternatives, modifications and variations as falling within the true scope and spirit of the present invention.
This application claims priority to U.S. Application No. 62/053,974, filed on Sep. 23, 2014.
Number | Date | Country | |
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62053974 | Sep 2014 | US |
Number | Date | Country | |
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Parent | 14844553 | Sep 2015 | US |
Child | 15886528 | US |