PLATE HEAT EXCHANGER
A plate heat exchanger includes a plurality of main plates having ridges and troughs to direct first and second flows of fluids across the main plates to exchange heat between the fluids while maintaining the first and second flows of fluids separate from each other. The heat exchanger also includes a first end plate including first and second inlets and first and second outlets. The first end plate includes a substantially flat inside surface configured to contact the ridges of a first main plate among the plurality of main plates and at least one slot formed in the substantially flat surface to provide a fluid communication of the first fluid flow between the inlet and a cavity formed by the first end plate and the first main plate.
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Embodiments of the invention relate to a plate heat exchanger, and in particular to end plates of plate heat exchanger.
Plate heat exchangers are widely used in the commercial industry as a means of exchanging energy between two liquids. The construction consists of a series of main plates having ribbed patterns on their surfaces and stacked one on top of the other. This arrangement forms channels between the plates through which the two liquids pass. As the two liquids enter their respective inlet ports they are independently directed to flow into alternating fin channels which permits heat to transfer from one liquid to the other. In order to maintain separation of the two liquids within the ports, the main plates incorporate local depressions in the port areas which alternately block off the flow passage from the port to the fin channels. In this way each port is hydraulically connected to every other fin channel. Each plate is coated with a braze filler metal. The entire heat exchanger assembly is placed in a furnace where the filler metal is melted creating a metallurgical bonds between the plates and forming a fluid seal.
Plate heat exchangers include top and bottom seal plates and top and bottom outer plates on outward-facing surfaces of the top and bottom seal plates, respectively. The top seal plate has a smooth surface and the bottom seal plate has a ribbed inward-facing surface (toward a center of the plate heat exchanger) and a smooth outward-facing surface (away from the center of the plate heat exchanger). The top and bottom seal plates form the outer pressure vessel of the heat exchanger. Typically, individual seals or seal slugs must be installed to block off the flow passage from an inlet port to a flow channel in the plate heat exchanger. The seal slugs are positioned around the inlets between the top seal plate and an adjacent main plate. However, the position of the individual seal slugs can shift during assembly and therefore are prone to cause fluid leakage of the heat exchanger.
In addition, ambient air can migrate into the space between the top seal plate and top outer plate. While the fluids passing through the heat exchanger may exhibit low freezing points that allow their temperatures to fall below 0° F. (−17.78° C.) without affecting the liquid states of the fluids, moisture within the ambient air freezes at 32° F.(0° C.). Consequently, the moisture in trapped between the top seal plate and the top outer plate may expand and crack the heat exchanger plates resulting in fluid leakage.
In addition, the draft angle of flanges of the main plates are chosen to ensure a proper braze seal between each main plate. The raised ribbed areas (herringbones) control the distance of separation between adjacent plates. A top seal plate having a flange with a same draft angle as an adjacent main plate may result in a poor fit, since the top seal plate does not include ridges. The poor fit may result in poor braze adhesion and fluid leakage.
The heat exchanger is subjected to stresses from the internal fluid pressures. The top plate and bottom plate provided support and stiffness to resist the internal pressure. The load emanating from the fluid pressure in the vicinity of the ports is commonly called a plug load. The area immediately surrounding the port areas is inherently subjected to high stresses due to the reduction of material (port holes) which must exist to allow fluid flow. Insufficient material around the port holes results in the inability of the heat exchanger to withstand low cycle fatigue resulting from pressure cycles of the liquids, ultimately leading to cracks and fluid leakage. However, the addition of excess material to compensate for the local high stresses would result in large weight penalties which cannot be tolerated in some applications, such as aerospace applications.
In addition, a position tolerance of the ports is subject to the ability to maintain a repeatable and consistent stack height of the main plates. Small variations in material thickness of the main plates (in the order of thousandths of an inch) will multiply by the number of main plates. An eighty-plate heat exchanger, for example can differ in stack height from unit to unit by 20 millimeters (mm) if each main plate had a variation of just 0.25 mm. When considering the additional position tolerances associated with other components of the heat exchanger, the resultant position tolerance of the ports can be 2.5 mm for example. This large variation from unit to unit is unacceptable for installations where precision is critical.
Mounting studs are conventionally welded to the thin top plate and bottom plate prior to furnace braze of the heat exchanger assembly. This requires time consuming welding and flush grinding of the underlying surfaces of the top and bottom plates adjacent to the studs to ensure a smooth uninterrupted surface against the adjacent main plates. The resultant strength of the stud retention is dramatically reduced. Also, the relatively thin top and bottom plates prevent sufficient thread engagement yielding a large variation in position tolerance of the studs. Additionally, the fluid fittings are historically welded to the weld stubs after furnace brazing. This requires time consuming welding and greater position tolerance of the final location of the fittings. The large variation from unit to unit is unacceptable for installations where precision is critical.
BRIEF DESCRIPTION OF THE INVENTIONEmbodiments of the present invention include a plate heat exchanger that includes a plurality of main plates having ridges and troughs to direct first and second flows of fluids across the main plates to exchange heat between the fluids while maintaining the first and second flows of fluids separate from each other. The heat exchanger also includes a first end plate including first and second inlets to provide the first and second flows to the plurality of main plates and first and second outlets to output the first and second flows from the plurality of main plates. The first end plate includes a substantially flat inside surface configured to contact the ridges of a first main plate among the plurality of main plates and at least one slot formed in the substantially flat surface to provide a fluid communication of the first fluid flow between the inlet and a cavity formed by the first end plate and the first main plate.
Embodiments of the invention further include a plate heat exchanger including a plurality of main plates having a ridged region including ridges and troughs to direct first and second flows of fluids across the main plates to exchange heat between the fluids while maintaining the first and second flows of fluids separate from each other. Each of the plurality of main plates further includes a flange extending from the ridged region at an oblique angle. The plate heat exchanger further includes a first end plate including first and second inlets to provide the first and second flows to the plurality of main plates and first and second outlets to output the first and second flows from the plurality of main plates. The first end plate includes a substantially flat main surface configured to contact the ridged region of a first main plate among the plurality of main plates and a flange surrounding the main surface and extending at an oblique angle with respect to the main surface. The flange of the first end plate has a draft angle less than a draft angle of the flange of the first main plate.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
Conventional plate heat exchangers have structures that result in cracking in leaking due to misalignments of parts of the plate heat exchangers. Embodiments of the invention relate to a plate heat exchanger having end plates configured to improve the structural integrity of the plate heat exchanger, reducing cracking and leaks.
The plate heat exchanger 100 includes a first end plate 120, also referred to herein as a top end plate 120 for purposes of description. The plate heat exchanger 100 also includes a second end plate 130, also referred to herein as a bottom end plate 130 for purposes of description. The top end plate 120 and bottom end plate 130 are positioned at opposite sides of the plurality of main plates 110. It is understood that although the terms “top” and “bottom” may be used for purposes of description, embodiments of the invention encompass a plate heat exchanger 110 having the first and second end plates 120 and 130 arranged with any spatial alignment relative to an earth plane.
The illustrated top end plate 120 includes openings 122 to receive fluid fittings 151, 152, 153 and 154. A first fluid may be input to the plate heat exchanger 100 via a fluid fitting 150 and output from the heat exchanger via a fluid fitting 152. Another fluid may be input to the plate heat exchanger 100 via the fluid fitting 153 and output from the plate heat exchanger 100 via the fluid fitting 154. Weld stubs 155, 156, 157 and 158 may also be provided between a wide portion of the fluid fittings 151, 152, 153 and 154 and the top end plate 120.
While particular shapes are used in
While the raised portions 233 of the bottom end plate 230 are illustrated in
The top end plate 320 includes openings 322a, 322b, 322c and 322d corresponding to fluid inlets and outlets. For purposes of description, opening 322c will be described as a fluid inlet 322c and opening 322d will be described as a fluid outlet 322d. Depressions or slots 323, 324, 325 and 326 are formed in the inward-facing surface 330 of the top end plate 320. Slots 323 and 325 connect to, and extend radially from the inlet 322c and the outlet 322d, respectively. Slots 324 and 326 may be connected to the slots 323 and 325, and may partially surround the inlet 322c and the outlet 322d, respectively, along an outer edge of the inward-facing surface 330 of the top end plate 320.
A slot 327 may extend lengthwise along a center of the top end plate 320. In another embodiment, the slot 327 may be off-center. In
Referring to
To ensure that the faying surfaces 335 have been properly brazed, the space between the plates, which may also be referred to as a dead zone 371, is pressurized with one of the fluids F entering the heat exchanger. Any voids in the braze will be immediately detected as an external leak during final test of the heat exchanger. A hermetically sealed joint may be detected by detecting no evidence of leakage. To achieve the pressurized dead zone 371, the port area, or the openings 322c and 322d and the dead zone may be hydraulically connected. The slots 323, 324, 325, 326 and 327 are strategically located to allow fluid pressure to enter each and every herringbone space between the top end plate 320 and the adjacent main plate 370. While only the top end plate 320 is illustrated in
A raised portion 328 or protrusion 328 surrounds the opening 322a to prevent fluid from the opening 322a from entering the dead zone 371 between the top end plate 320 and an adjacent main plate 370. The raised portion 328 is illustrated with dashed lines in
While
In one embodiment, the draft angle A is different than the draft angle B. In particular, the draft angle A may be less than the draft angle B, and the angle A1 may be less than the angle B1. As illustrated in
A similar feature is provided for the bottom end plate 430, as illustrated in
Referring to
Referring to
The top end plate 820 includes a port defined by an inner diameter surface made up of a lower portion 821, also referred to as a pilot region 821 and an upper portion 822, also referred to as a braze region 822. The top end plate 820 may be configured to be attached to the main plate 810, and the main plate 810 may be configured to be attached to the main plate 811. The inner diameter surface of the top end plate 820 may be configured to receive the fluid fitting 854 having an outer diameter surface 857. A recess 856 is formed in the outer diameter surface 857 of the fluid fitting 854, the recess 856 defined by recess walls 855. The fluid fitting 854 may also include a fluid channel 858.
In embodiments of the invention, the recess 856 is formed to have a pre-defined size such that a predetermined amount of braze material may be provided in the recess 856. The pilot region 821 has a diameter smaller than the braze region 822, such that the pilot region 821 tightly or closely contacts the outer diameter surface 857 while the braze region 822 defines a gap between a surface of the braze region 822 and the outer diameter surface 857. The thickness of the braze material between the outer diameter surface 857 and the braze region 822 may be pre-determined and controlled based on controlling the diameter of the braze region 822, thereby maintaining the strength of a braze joint.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
Claims
1. A plate heat exchanger, comprising:
- a plurality of main plates having ridges and troughs to direct first and second flows of fluids across the main plates to exchange heat between the fluids while maintaining the first and second flows of fluids separate from each other; and
- a first end plate including first and second inlets to provide the first and second flows to the plurality of main plates and first and second outlets to output the first and second flows from the plurality of main plates, the first end plate including a substantially flat inside surface configured to contact the ridges of a first main plate among the plurality of main plates and at least one slot formed in the substantially flat surface to provide a fluid communication of the first fluid flow between the inlet and a cavity formed by the first end plate and the first main plate.
2. The plate heat exchanger of claim 1, wherein the at least one slot includes a first slot extending radially from the first inlet, a second slot having a substantially circumferential shape around a portion of the first inlet and connected to the first slot, and a third slot extending lengthwise along a center of the first end plate.
3. The plate heat exchanger of claim 1, wherein the at least one slot includes a first slot extending circumferentially around an entire circumference of the first inlet, and a second slot extending lengthwise along a center of the first end plate.
4. The plate heat exchanger of claim 1, wherein the first fluid is pressurized in the cavity formed by the first end plate and the first main plate.
5. The plate heat exchanger of claim 1, wherein the first main plate includes a plurality of ridges separated by a plurality of troughs, the plurality of troughs and ridges forming a chevron pattern,
- the at least one slot includes a first slot adjacent to the first inlet and a second slot extending lengthwise along a center of the first end plate at an apex of the chevron pattern, and
- the first slot is in fluid communication with at least one trough between adjacent ridges of the first main plate, the at least one trough is in fluid communication with the second slot, and the second slot is in fluid communication with each other trough of the plurality of troughs.
6. The plate heat exchanger of claim 1, further comprising a protrusion surrounding the first inlet on an inside surface of the first end plate, the protrusion configured to contact the first main plate to form a fluid-tight seal with the first main plate.
7. The plate heat exchanger of claim 1, wherein the first main plain includes a ridged portion and a flange surrounding the ridged portion and extending outward from the ridged portion to have a draft angle that is an acute angle, and
- the first end plate comprises a body having an inside surface configured to contact the ridges of the ridged portion of the first main plate and a flange surrounding the main body, an inside surface of the flange of the first end plate configured to contact an outer surface of the flange of the first main plate, and a draft angle of the first end plate being less than the draft angle of the first main plate
8. The plate heat exchanger of claim 7, further comprising:
- a second main plate among the plurality of plates, the second main plate including a ridged portion and a flange surrounding the ridged portion and extending outward from the ridged portion to have a draft angle that is an acute angle; and
- a second end plate having a first outer side configured to contact the ridged portion of the second main plate and a second outer side surrounding the first outer side and having a draft angle that is an acute angle, the second outer side configured to contact an inner side of the flange of the second main plate, the draft angle of the second outer side being greater than the draft angle of the second main plate.
9. The plate heat exchanger of claim 1, wherein the first end plate includes at least one thin region and at least one thick region, the at least one thick region located in a region identified as being subject to a greater stress than the at least one thin region when the plate heat exchanger is in operation.
10. The plate heat exchanger of claim 9, wherein the at least one thick region includes regions surrounding the first and second inlets and first and second outlets at ends of the first end plate, and ribs extending width-wise across the first end plate.
11. The plate heat exchanger of claim 1, wherein the first end plate includes at least one receptacle on an outward-facing surface opposite the inside surface, the at least one receptacle comprising a base and a protrusion having a shape configured to receive and surround a mounting stud, such that sides of the mounting stud contact sides of the protrusion while an end of the mounting stud contacts the base of the receptacle.
12. The plate heat exchanger of claim 1, further comprising a fluid fitting configured to fit into at least one of the first inlet and the first outlet to provide a flow of fluid through the fluid fitting into or out from the plurality of main plates, the fluid fitting including a recess in a surface adjacent to an inner diameter surface of the at least one of the first inlet and the first outlet.
13. The plate heat exchanger of claim 12, wherein the recess surrounds the fitting.
14. The plate heat exchanger of claim 12, wherein the inside diameter surface of the first inlet or the second inlet includes a pilot located linearly between the recess and an end of the inside diameter surface corresponding to the inside surface of the first end plate and a braze region located between the recess and an end of the inside diameter surface corresponding to an outer surface of the first end plate, the braze region having a diameter greater than the pilot.
15. The plate heat exchanger of claim 1, further comprising:
- a second end plate on an opposite side of the plurality of main plates from the first end plate.
16. The plate heat exchanger of claim 15, wherein the second end plate includes a substantially flat inside surface configured to contact the ridges of a second main plate among the plurality of main plates and at least one slot formed in the substantially flat surface to fill with fluid from one of the first fluid flow and the second fluid flow a cavity formed by the second end plate and the second main plate.
17. The plate heat exchanger of claim 15, wherein each of the first end plate and the plurality of main plates includes a flange surrounding a ridged portion, the flanges of the first end plate and the plurality of main plates extending toward the second end plate and being in contact with a flange of an adjacent main plate to inhibit movement of the first end plate and the plurality of main plates, and
- the second end plate includes an upper surface and an outer side surface surrounding the upper surface and having a draft angle that is an acute angle, the second side surface configured to contact a flange of a second main plate among the plurality of main plates and the draft angle of the second side surface being greater than a draft angle of the flange of the second main plate.
18. The plate heat exchanger of claim 17, wherein the outer side surface of the second end plate has a draft angle greater than a draft angle of the flange of the first end plate.
19. A plate heat exchanger, comprising:
- a plurality of main plates having a ridged region including ridges and troughs to direct first and second flows of fluids across the main plates to exchange heat between the fluids while maintaining the first and second flows of fluids separate from each other, each of the plurality of main plates further including a flange extending from the ridged region at an oblique angle; and
- a first end plate including first and second inlets to provide the first and second flows to the plurality of main plates and first and second outlets to output the first and second flows from the plurality of main plates, the first end plate including a substantially flat main surface configured to contact the ridged region of a first main plate among the plurality of main plates and a flange surrounding the main surface and extending at an oblique angle with respect to the main surface, the flange of the first end plate having a draft angle less than a draft angle of the flange of the first main plate.
Type: Application
Filed: Jan 17, 2013
Publication Date: Jul 17, 2014
Applicant: HAMILTON SUNDSTRAND CORPORATION (Windsor Locks, CT)
Inventors: Richard Rusich (Ellington, CT), Michael R. Barone (Amston, CT), Matthew William Miller (Enfield, CT)
Application Number: 13/743,986
International Classification: F28F 3/00 (20060101);