BRIEF DESCRIPTION OF DRAWINGS
The accompanying drawings illustrate a prior art combination heat exchanger and preferred embodiments of the present invention that will be further described with reference to the following figures.
FIG. 1 is a cross-sectional view of a prior art combination heat exchanger.
FIG. 2 is a cross-section view of the present invention combination heat exchanger having an end tank assembly that includes an integrated end tank, a header plate, and a gasket therebetween.
FIG. 3 is a perspective view of an integrated plastic end tank having two bulk heads, reinforcement rib, and means for leak detection with gasket applied on perimeter edge.
FIG. 4 is a partial perspective view of an alternative embodiment of an integrated plastic end tank having a foot step with gasket applied on perimeter edge in relationship to a metal header prior to assembly.
FIG. 5 is a partial cross sectional view taken along the longitudinal axis of an integrated plastic end tank with gasket applied on perimeter edge in relationship to a metal header prior to assembly.
FIG. 6 is a partial cross sectional view taken along the longitudinal axis of an integrated plastic end tank with gasket in relationship to a metal header after assembly.
FIG. 7 is a cross sectional view of an integrated plastic end tank along latitudinal axis between bulkheads in relationship to a metal header after assembly.
FIG. 8 is a top view of an integrated plastic tank with gasket applied showing difference in gasket compression ratio along perimeter edge.
DETAILED DESCRIPTION OF INVENTION
In reference to FIGS. 2 through 8, end tank 150 is shown substantially rectangular in appearance. The present invention does not intend the substantially rectangular shape to be limiting, but can also encompass other elongated shapes with an open face along the longitudinal axis.
FIG. 2 is a cross-sectional view of the present invention combination heat exchanger. The heat exchanger includes a core 110 having a bundle of tubes 120 that are substantially parallel. The tubes 120 are jointed longitudinally by conventional means such as welding, brazing or soldering to a supporting structure such as fins between the tubes. The core 110 has two core ends 140a, 140b corresponding with tube openings 145.
Each core end is attached to end tank assembly 105 that comprises of end tank 150, a gasket 280, and a header plate 270. The tube openings 145 are affixed to perforations 620 located on the header plate 270 by conventional means such as welding, brazing or soldering. Header plate 270 is mechanically attached to end tank 150 with gasket 280 between the contact surfaces of header plate 270 and end tank 150.
In reference to FIG. 3, end tank 150 has two side walls 160a, 160b that are integral with a bottom wall 170 along a longitudinal axis 180 and two end walls 190a, 190b along a latitudinal axis 200 defining an elongated cavity 210. The tank opening is defined by a perimeter tank foot 215 that protrudes laterally outward from the exterior edges of the two side walls 300a, 300b and exterior edges of the two end walls 310a, 310b.
Within the elongated cavity 210 are two bulkheads 220a, 220b situated along a latitudinal axis 200 dividing the elongated cavity 210 into a first chamber 230, a second chamber 240, and a third chamber 250. The heights of the bulkheads are less that heights of the side and end walls. Height of bulkhead is show as distance A and heights of walls are show as distance B in FIG. 5.
The volume distribution for each chamber, which is dictated by the number tubes 120 required to be in communication with each of the three chambers for the desired heat transfer requirements, can be adjusted by varying the placement of the bulkheads 220a, 220b along the longitudinal axis 180. The greater the temperature variation between first chamber 240 and third chamber 250, the greater the distance required between bulkheads for thermal isolation.
In reference to FIG. 3 through 8, the first chamber 230 and third chamber 250 are utilized for accumulation of heat transfer fluid and distribution of flow across the tubes 120. The second chamber 240 situated between the first chamber 230 and third chamber 250 is empty and acts as a thermal barrier to isolate the temperature and pressure variations between the first chamber 230 and third chamber 250. Tubes 120 in communication with the second chamber are dead, voided of fluid flow, thereby providing a thermal barrier between tubes in communication with first chamber 230 and tubes in communication with third chamber 250.
Reinforcing the two bulkheads is rib 410 integrally connecting bulkheads 220a, 220b with bottom wall 170. Rib 410 is located along the longitudinal axis 180 in the second chamber 240.
Also located within second chamber 240 is a mean to detect leaks from first chamber 230 and third chamber 250 into the second chamber 240. The means can include a mechanical or electrical sensing device; however, the preferred mean is an outlet 420 on a side walls between the bulkheads. A breach in integrity of either one of the bulkheads will result in heat transfer fluid filling second chamber 240 and then discharging through outlet 420. The direct discharge of the heat transfer fluid from either one of the bulkheads prevents intermingling of heat exchanger fluids and allows for economical leak detection since no additional hardware is required.
End tank 150 having bulkheads 220a, 220b, rib 410, and outlet 420 is formed of plastic, preferably nylon, and it is a seamless integrated one piece unit. End tank 150 can be manufactured by conventional means such plastic injection molding.
In reference to FIGS. 3, 4, and 8, the exterior edges of the two side walls 300a, 300b, and exterior edges of the two end walls 210a, 210b, together with the protruding perimeter foot 500 forms a perimeter edge. A uniform bead of elastomer gasket 280 is applied on perimeter edge 260 and exterior edges of the two bulkheads 320a, 320b. The gasket is then cured-in-place prior to assembling end tank 150 to header plate 270.
In reference to FIG. 3, a bead of elastomer gasket is applied on the perimeter edge portion that outlines the first chamber 230 with the gasket knit line 500 overlapping on exterior edge of bulk head 320b defining first chamber 230. Another uniform bead of gasket is applied on the perimeter edge portion that outlines the third chamber with the gasket knit line 500 overlapping on exterior edge of bulk head 320a defining the third chamber 250.
It is desirable for the knit lines 500 of the gaskets to overlap on the exterior edges of the bulkheads 320a, 320b. The overlapping of the knit lines 500 provides additional gasket material to allow for greater compression ratio of the gasket on the edges of the bulk heads 320a, 320b. The higher compression ratio of the gasket provides greater seal integrity between the bulkheads with the header plate 270. It is optional to provide gasket on the portion of the perimeter edge that is part of the side wall of the second chamber located between the bulk heads.
The Compression Ratio of the gasket is defined as the ratio between the Compression Squeeze and the original cross-section of the gasket. The compression ratio is typically expressed as a percentage.
Compression Squeeze=original cross section−compressed cross section
Compression Ration (%)=(compression squeeze/original cross section)×100
Reference to FIG. 4 through 7, the physical feature of the header plate 270 includes a stage portion 600 that is elevated toward elongated cavity 210 of end tank 150. Stage portion 600 includes latitudinal pockets 610 to cooperate with the exterior edges of the bulkheads 320a, 320b to define a first spatial distance X shown in FIG. 6. The header plate also has an annular planar surface that circumscribes stage portion 600, to cooperate with the perimeter edge of the end tank to define a second spatial distance Y shown in FIG. 6. The original cross section or diameter of the gasket is shown as distance Z in FIG. 5 which is greater than distance Y and distance X.
The first spatial distance X is less than the second spatial distance Y, thereby resulting in a greater compression ratio of the gasket located within the first spatial distance relative to the compression ratio of the gasket located within the second spatial distance. More specifically, the compression ratio of the gasket on the exterior edges of the bulkhead is greater than the compression ratio of the gasket on the perimeter edge of the end tank as shown in FIG. 7.
The greater compression ratio of the gasket between the exterior edges of the bulkheads and lateral pockets of the header plate allows for a more robust seal between chambers. Robust seals are required along bulkheads to withstand expansion differential stresses associated with combination heat exchanger that houses heat transfer fluids with different temperature and pressure cycle requirements.
Referring to FIG. 4 through 6, periodically protruding outward of header plate 270 are crimp tabs 640. As header plate 270 is mated to the end tank 150, crimp taps 640 are plastically deformed to embrace the perimeter tank foot 215 of end tank 150. The latitudinal pockets 610 and annular planar surface 630 acts as the contact surface to the cure-in-place gasket which is applied on the perimeter edge of the end tank and exterior edge of bulkheads 220a, 220b.
Shown in FIG. 4 is another embodiment of the invention wherein a tank foot step 400 is located on the edges of the two side wall located between the bulkheads 220a, 220b in surrogate of a segment of gasket. The tank foot step 400 provides a secure seal against the contact surface of the header plate 290 while maintaining proper compression ratio of the gasket located along the exterior edges of the bulkheads 320a, 320b.
Referring to FIGS. 6 through 7. It is desirable for the compression of the gasket to be greater along the exterior edges of bulkheads 320a, 320b, shown as distance X, than that of the compression of the gasket along the remaining perimeter edge of the end tank 260, shown as distance Y.
Referring to FIG. 8, the compression ratio of the gasket along said exterior edges of said two side wall and along said exterior edges of said two end walls is represented as M %, where as the compression ratio of the gasket along exterior edges of said bulkheads is represented as M %+N %. The compression ratio of the gasket along said exterior edges of said two side wall and along said exterior edges of said two end walls is between 40 to 60 percent, preferably 50 percent, and the compression ratio of the gasket along exterior edges of said bulkheads is between 50 and 70 percent, preferably 60 percent.
The compression ratio of the gasket along the exterior edges of the bulkheads is determined by the spatial distance between the bulkheads and the latitudinal pockets of the header plate, shown as distance X in FIG. 6 and FIG. 7. The compression ratio of the gasket along the exterior edges of the perimeter edge is determined by the spatial distance between the perimeter edge and annular planar surface of the header plate, shown as distance Y in FIG. 6 and FIG. 7.
While this invention has been described in terms of the preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.
Patent Application
20080047687
