Patent Application
20100300651
The present invention relates to double-walled plate heat exchangers.
Plate heat exchangers are used in many process fields where a fluid in a liquid or gas form is heated or cooled to a suitable temperature during continuous flow through the plate heat exchanger. When a fluid is to be heated, it is caused to flow through a small passage in the plate heat exchanger, the passage having a large thermal contact face exposed to a heat-emitting fluid which preferably passes through the plate heat exchanger in counterflow to the fluid for heating. When a fluid is to be cooled, the other fluid in the heat exchanger is heat-absorbing.
When the plates are pressed together, a series of flow cavities are formed in between each pair of plates, e.g., plates 10a, 10b. Thus, the first fluid will usually flow through alternating cavities formed between the plates 10, while a second fluid will flow through the other cavities. The other fluid is added through a third distribution channel 17 and leaves the plate heat exchanger 1 through a fourth distribution channel 18 after flowing through the cavities formed between the plates 10. The two fluids can flow through the cavities in a counterflow manner, thereby encouraging heat transfer. There will thus be a thermal exchange between the two liquids via the plates 10, without physical contact between the two fluids. This thermal exchange may take place such that one of the fluids may be cooled or heated by releasing energy to or receiving energy from the other fluid.
The gasket part 22 also prevents fluid passage from the other port holes 12 to the cavity between the two plates. For example, the first fluid passing through port holes 12a and 12c has no contact with the second fluid passing through port holes 12b and 12d. As shown, the gasket 20 additionally has two ring-shaped gasket parts 24 surrounding and sealing off the other port holes 12b, 12d which do not communicate with the cavity between the plates. The ring-shaped gasket parts 24, as depicted, are an integral part of the gasket 20, since they are connected to the gasket part 22 through connectors 26.
It will be seen from
One problem that may arise with respect to one of the above-described designs, is one of these inner plates, 10b-10d can develop an unintended perforation, e.g., a hole or a crack, in the zone transferring heat from the hot medium to the cold medium. The aforementioned perforation may allow the higher-pressure medium to pass through the perforation into the lower-pressure medium, which is not desirable. For example, the higher pressure medium may be glycol and the lower pressure medium may be potable water, resulting in the contamination of the potable water with the toxic glycol.
A proposed solution to the above-described drawback uses double-walled plates replacing single-walled plates as described above. It is known to replace each of the inner plates 10b-d with double-walled elements. Such elements are made from two metal skins which have undergone stretch forming together. The two metal skins are typically tightly and permanently joined in the corner port holes 12.
If there is an unintended perforation in the heat transfer area, the medium in that area penetrates the perforation and enters the space between the two skins and leaks out to the atmosphere. A process operator is thus alerted to a problem which he must attend to.
The drawback with the above is that the two skins have been joined permanently, so that the space between the skins cannot be inspected. This drawback is significant for most applications and rather serious for fluid foods.
A proposed solution to this drawback uses port holes 12 that are not permanently joined, but by making different-sized holes in the two skins, and providing a suitable sealing member, such as peripheral sealing gasket-carrying grooves, at these port holes 12, the permanent joining is avoided altogether. Thus, the space between the plates 10 is able to be inspected.
However, because the two skins are in close contact, any leakage into the space between the skins does not easily reach the external edge of the plate heat exchanger 1 for easy observation by the process operator, which means the process operator may not be properly alerted to a problem.
Essentially, where peripheral sealing gasket-carrying grooves exist, the gasket compression through the plate stack hinders leakage to the external edge. One known solution to this is placing metal tapes between the skins in line with the gasket sealing members or by creating a small channel. In either case, the net result is one or more leak paths in the space between the plates 10 in line with the gasket sealing members on each side. Typically, the sealing portion extends around the heat exchange portion as well as the flow openings, (e.g., port holes 12).
This has significant drawbacks, as one sealing potion envelopes the other. In such a scenario, a gasket leak across the port hole gasket 24 can cause cross contamination. Secondly, because of the compressive loads exercised by port hole gaskets 24, the location of the peripheral sealing gasket-carrying grooves is inappropriate, as it is not possible to properly inspect the plate heat exchanger 1 for leaks, or to know which plate 10 has a leak.
For external leakage, virtually all conventional plate heat exchangers 1 have a leakage groove in a so-called vent space. This vent space is in free communication with the atmosphere around the plate heat exchanger 1. This communication is achieved by locally removing the sealing portion of the surrounding gasket 20. Often, the plate 10 is weakened at the same time to ensure that there is no impediment to leakage. The purpose of this design is to make sure that, in a conventional plate heat exchanger 1, there is a double-gasket barrier between hot and cold media, the space between the barriers being open to atmosphere. The problem is that this space is not in between the two skins of the double-walled plate 10 but on the front face of a front plate, e.g., plate 10a-10d, where the gasket 20 is on only one side of the plate 10a-10d.
Accordingly, there is a need and desire to provide a plate heat exchanger with multi-layered plates which provides drainage of fluid that accumulates between plates, prevents cross-contamination of fluids, and allows inspection of the heat exchanger for leaks.
Embodiments of the present invention advantageously provide a plate heat exchanger with multi-layered plates which provides drainage of fluid that accumulates between plates, prevents cross-contamination of fluids, and allows inspection of the heat exchanger for leaks.
An embodiment of the invention includes a double-walled plate heat exchanger and method of managing the same includes a first plate including a first skin, a second skin, at least two port holes, and a leakage escape path between the first and second skins for allowing leaked fluid to exit the double-walled plate heat exchanger, the leakage escape path being in contact with a leakage orifice in one of the skins, and an outer edge of the double-walled plate heat exchanger, the first plate further including a second plate in contact with the second skin.
Another embodiment of the invention includes a method of managing a leak in a double-walled plate heat exchanger, the method including allowing fluid leaked between first and second skins of a first plate in a double-walled plate heat exchanger to exit the double-walled plate heat exchanger via a leakage escape path, the leakage escape path including a leakage orifice, the first plate further including first and second port holes.
Another embodiment of the invention includes a double-walled plate heat exchanger includes leakage escape means for allowing fluid leaked between first and second skins of a first plate in a double-walled plate heat exchanger to exit the double-walled plate heat exchanger, the leakage escape means including at least one leakage orifice means for allowing the leaked fluid to exit via first skin.
Another embodiment of the invention includes a double-walled plate heat exchanger which includes leakage escape means for allowing fluid leaked between first and second skins of a first plate in a double-walled plate heat exchanger to exit the double-walled plate heat exchanger, the leakage escape means including leakage orifice means for allowing the leaked fluid to exit from between the first and second skins, the first plate having at least two port holes.
There have thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.
In the following detailed description, reference is made to the accompanying drawings, which form a part hereof and show by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice them, and it is to be understood that other embodiments may be utilized, and that structural, logical, processing, and electrical changes may be made. The progression of processing steps described is an example; however, the sequence of steps is not limited to that set forth herein and may be changed as is known in the art, with the exception of steps necessarily occurring in a certain order.
The invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout.
Turning now to the figures,
As illustrated, plate 110, e.g., first plate 110a, comprises two skins 301, 302. The gasket 120 has a gasket part 122 which substantially follows the periphery of the individual plate 110 and thus seals the heat transfer area 114 formed between two plates 110 upon assembly of the plate heat exchanger 100. The gasket part 122 permits fluid flow over the plate 110 from an inlet, e.g., port hole 112 as depicted in
As shown, the gasket 120 has a ring-shaped gasket part 124 surrounding and sealing off the port holes 112 which does not communicate with the heat transfer area 114 between the plates. The ring-shaped gasket part 124 is an integral part of the gasket 120, since it is connected to the gasket part 122 through connector 126. It will be seen from
In order to allow escape of fluid trapped between skins of the double-walled plate heat exchanger 100, a leakage escape path 311 is provided between the first and second skins 301, 302 for allowing leaked fluid to exit the double-walled plate heat exchanger 100, the leakage escape path 311 is in contact with at least one leakage orifice 315 and an outer edge 306 of the double-walled plate heat exchanger 100. The leakage orifice 315 is provided in a vent area 350 of the front plate 300. The first skin 301 is provided with the gasket 120. The second skin 302 may be viewed through the leakage orifice 315. A leakage groove 305 is provided across the gasket connector 126, so fluid may escape to the atmosphere at the outer edge 306 of the double-walled plate heat exchanger 100. In gasket area 310, the gasket may be recessed, or even completely removed or eliminated, to allow passage of fluid across the leakage groove 305. Depending on the positioning of the leakage orifice 315 with respect to the leakage groove 305, an optional groove extension 316 may be provided to further guide fluid from the leakage orifice 315 to the leakage groove 305.
It should be appreciated that, in the absence of leaking of the fluids, the two fluids are kept completely separate by the gasket 120. Accordingly, if a leak occurs between the skins of the plate 110, for example, via a defect in, crack in, or corrosion of one of the skins 301, 302, internal pressure will tend to push the fluid toward the leak guide 421 or directly to the indentation 420, and leakage orifice 315, depending on the location of the defect causing the leak. The fluid will them flow through the leakage orifice 315 to the leakage groove 305, and out to the atmosphere where it will either dissipate or be collected for analysis and/or disposal. The location of the expected leak will thus be known in advance, so an operator will know where to look, in general, for leaks.
Another embodiment of the present invention involves providing one or more leakage orifices 315 in the front plate 300 in the vent area 350, 450, such that the space between the double-walled plates 110a and 110b is in communication with this vent area 350, 450. The vent area 350, 450 is open to the atmosphere via the break in the sealing at the periphery, e.g., gasket area 310. In this way, any fluid which has reached the space between the skins 301, 302 of the plate 110, e.g., via a perforation, is able to leak out into the vent space 350, 450 and then out of the vent space 350, 450 to the edge 306 of the double-walled plate heat exchanger 100.
It should be noted that the leakage orifice 315 is positioned on a surface which is in a relatively close contact with the second skin 302. To further ensure that this close contact does not become a resistance to leakage flow, the second skin 302 is modified by a depression or depressions, i.e., indentation 420, which align with the leakage orifice 315 in the front skin 301 to reduce flow resistance.
The leak guide 421 may be provided at an edge of the heat exchange portion of the second skin 302 which is not in contact with a sealing member. This positioning is preferred to reduce the hydraulic resistance to the leakage path out of the heat exchange zone. Substantial design changes can be made in this area since these surfaces do not have to seal against a gasket 120. Various shapes and inclinations, longitudinal or transverse or intermediate, or attachments of various thicknesses and numbers can be made to allow leakage to reach the leakage orifices and depressions (e.g., leakage orifice 315, indentation 420) made in the first and second skins 301, 302 in the vent space 350, 450 as described above.
Located within the heat transfer area 114, proximate to the leak guide 421, distribution areas are positioned. These distribution areas may have large flat portions. When the skins 301, 302 touch flat-on-flat, oftentimes it is more difficult for leakage to overcome the flow resistance. Accordingly, a rib or ribs, e.g., ribs 425, 430, 435, may be formed in one or both skins which create a local separation to carry leakage from the heat transfer area 114 to the vent space 350, 450. Alternatively, small width and small thickness attachments can be made to provide the same effect. The attachments may be permanently attached or removable. The shape and length of ribs or attachments can vary depending on the application. For example, the size of such ribs and attachments must be determined to avoid impeding heat transfer and creating undue flow resistance in the intended flow path of flow media. Such separator ribs and attachments, e.g., ribs 425, 430, 435, may be formed at any point where there is large flat-to-flat contact.
Turning now to
In one embodiment encompassed by the present invention, the method 500 further includes forming at least one depression, e.g., indentation 420, in the second skin 302 of the first plate 110a. Said indentation 420 at least partially surrounds the at least one leakage orifice 315 in the first plate 110a such that the first and second skins 301, 302 are separated near the at least one depression (e.g., indentation 420) and the leakage orifice 315 (step 550). Forming the second plate 110b may further include forming a first skin, e.g., first skin 301 and forming a second skin, e.g., second skin 302. Forming the second plate 110b may also include forming at least one separator, e.g., ribs 425, 430, 435, configured to provide separation between the first and second plates 110a, 110b near the at least one separator (step 560). Step 560 may further include providing the at least one separator as part of the escape path for leakage between the first and second skins 301, 302 of the first plate 110a.
Referring now to
It should be noted that, although the methods 500, 600, 700 are illustrated as having steps in a particular order, the specific order is immaterial to the invention and is shown as an example of steps of forming a double-walled plate heat exchanger in accordance with the invention. Embodiments of the invention may include methods of forming or assembling any of the heat exchangers discussed herein or within the scope of the invention.
Another embodiment shown in
The back skin 815 may have supporting separators 840 ridges pressed into it. In one embodiment, the separators 840 may be ridges pressed upwards toward where the bridge gasket groove 826 of the front skin 810 will be when the double-walled plate heat exchanger 800 is assembled. The separators 840 may also be formed by attaching another object to the front skin 810. These separators 840 maintain a gap between the two skins 810, 815 when the skins 810, 815 are pressed together upon assembly. If any puncture occurs through either the first skin 810 or the second skin 815, fluid passes between the skins 810, 815. It can flow upwards, through a small inherent internal space between the skins 810, 815, until it reaches the bridge gasket groove 826.
The gap forms a channel between the skins 810, 815, and collects fluid from a backside 870 of the front skin 810 behind the center section 839 over the entire distance of a flow width of the front plate 805, and conducts that fluid all the way through to a depression 845 in the second skin 815. The depression 845 may be located directly underneath the hole 820 in the first skin 810. The backside 870 of the front skin 810 and front center 871 of the back skin 815 will be in contact upon assembly. Unless there is a leak, there will be no fluid in the space between the backside 870 of the front skin 810 and front center 871 of the back skin 815
The fluid can rise up through the hole 820 of the first skin 805, and then pass out through a leakage cutaway groove 848 of the gasket 850 and exit externally at an outer edge 855 of the front plate 805. The front plate 805 may also have a groove depression 860 an outer side wall of the groove 848, so there is a clear leakage slot allowing fluid to pass through to the outside.
Each item applied to the area near the first port 835, e.g., the hole 820, and the separators 840, is also applied to the third port 837. Fluid can emerge from the front plate 805, either from the first leakage groove 845 near the first port 835 or a second hole 846 and second leakage groove 847 from the third port 837. Each item described as being on the front plate 805 may be included in a back plate 880 having four ports 885-888, except each is applied to the diagonally opposite ports, e.g., instead of to the first and third ports, they are applied to the second and fourth ports, e.g., ports 886, 888.
In another embodiment of a double-walled plate heat exchanger 900, shown in
In this case, the front skin 910 may have at least one separator 920 formed on the flow port side of the plate in a flow bridge 925. The separators 920 may be made by pressing into the front skin 910 or by attaching another object to the front skin 910 to maintain separation of the flow bridge 925 from its mating back skin bridge gasket 930. Fluid may collect from a backside 970 of the front skin 910 behind a center section 939 over the entire distance of a flow width of the front plate 905, and be conducted all the way through to a hole 935 in the second skin 915. The backside 970 of the front skin 910 and front center 971 of the back skin 915 will be in contact upon assembly. Unless there is a leak, there will be no fluid in the space between the backside 970 of the front skin 910 and front center 971 of the back skin 915
The back skin 915 has a leakage hole 935. This permits liquid to flow out from between the skins 910, 915. Liquid may emerge and instead flow back from the back skin 915, and leak toward the next plate 950. The next plate 950 may have a leakage groove 955 in a gasket 960. So again, the liquid leaks out externally. Fluid from the front plate 905 would emerge from a gasket leakage grove 955 in the next plate 950. There may be an indentation 965 in the next plate 950 located where the back skin 915 would be upon assembly of the double-walled plate heat exchanger 900. The back skin may have its own separators 980, similarly to the front skin separators 920.
The processes and devices in the above description and drawings illustrate examples of some methods and devices of many that could be used and produced to achieve the objects, features, and advantages of embodiments described herein. Thus, they are not to be seen as limited by the foregoing description of the embodiments, but only limited by the appended claims. Any claim or feature may be combined with any other claim or feature within the scope of the invention. The many features and advantages of the invention are apparent from the detailed specification, and, thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and, accordingly, all suitable modifications and equivalents may be resorted to that fall within the scope of the invention.
