FILTER ASSEMBLY FOR PLATE HEAT EXCHANGERS AND METHOD OF CLEANING A WORKING MEDIUM IN A PLATE HEAT EXCHANGER

Abstract

A filter assembly for a plate heat exchanger comprising inlet and outlet ports for passage of a working medium and a cooling or heating fluid, respectively, wherein the filter assembly is dimensioned to fit into the inlet or outlet ports, wherein the filter assembly comprises a proximal flange and a distal flange and at least one filter tube attached at respective ends to the proximal flange and the distal flange, respectively, wherein the at least one filter tube is adapted to receive an elongated filter element and further comprises a plurality of inlet holes arranged on a circumferential surface thereof, and wherein the distal flange comprises at least one through-going outlet aperture in fluid communication with the interior of the at least one filter tube.

Claims

1. A filter assembly for a plate heat exchanger comprising inlet and outlet ports for passage of a working medium and a cooling or heating fluid, respectively, the filter assembly being dimensioned to fit into the inlet or outlet ports, the filter assembly comprising: a proximal flange; a distal flange; and at least one filter tube attached at respective ends to the proximal flange and the distal flange, respectively, wherein the at least one filter tube is adapted to receive an elongated filter element wherein the at least one filter tube comprises a plurality of inlet holes arranged on a circumferential surface thereof, and wherein the distal flange comprises at least one through-going outlet aperture in fluid communication with the interior of the at least one filter tube.

2. The filter assembly according to claim 1, wherein the plurality of inlet holes is arranged substantially in a longitudinal direction of the at least one filter tube and is located substantially in the same angular position with respect to a longitudinal axis of the at least one filter tube.

3. The filter assembly according to claim 1, wherein the filter assembly further comprises a plurality of filter tubes, and wherein the distal flange comprises a plurality of through-going outlet apertures, each outlet aperture of the plurality of through-going outlet apertures being in fluid communication with the interior of a respective one of the plurality of filter tubes.

4. The filter assembly of claim 3, wherein the plurality of inlet holes on each of the plurality of filter tubes is located substantially in the same angular position with respect to the longitudinal axis of their respective filter tube.

5. The filter assembly according to claim 1, wherein the distal flange comprises a beveled surface, which tapers inwardly in a distal direction of the filter assembly.

6. The filter assembly according to claim 1, further comprising a biasing element arranged inside the at least one filter tube to bias the elongated filter element towards the distal flange.

7. The filter assembly according to claim 1, wherein the proximal flange comprises: at least one through-going access hole aligned with the at least one filter tube; and a removable lid to cover the at least one through-going access hole.

8. The filter assembly according to claim 7, wherein the filter assembly further comprises a plurality of filter tubes, wherein the distal flange comprises a plurality of through-going outlet apertures, each outlet aperture of the plurality of through-going outlet apertures being in fluid communication with the interior of a respective one of the plurality of filter tubes, and wherein the proximal flange comprises a plurality of through-going access holes, each aligned with a respective one of the plurality of filter tubes.

9. The filter assembly according to claim 7, wherein the removable lid comprises at least one drainage pipe in fluid communication with a lower end of the at least one filter tube, opposite the plurality of inlet holes.

10. The filter assembly according to claim 1, wherein the at least one outlet aperture further comprises a pipe extending into the filter tube.

11. A method of cleaning a working medium in a closed-loop cycle comprising a plate heat exchanger including a plurality of heat exchanger plates arranged adjacent each other in a frame and having through-going holes for passage of the working medium and a cooling or heating fluid, respectively, the method comprising: providing a filter assembly including a proximal flange, a distal flange, at least one filter tube attached at respective ends to the proximal flange and the distal flange, respectively, at least one elongated filter element arranged in the at least one filter tube, a plurality of inlet holes arranged on a circumferential surface of the at least one filter tube, and at least one through-going outlet aperture arranged in the distal flange and in fluid communication with the interior of the at least one filter tube; inserting the filter assembly into an inlet or outlet port for the working medium in the plate heat exchanger; fastening the filter assembly on a frame of the plate heat exchanger, such that a fluid-tight seal is provided between the proximal flange and the inlet or outlet port; and pumping the working medium in the closed-loop cycle, such that it passes into the filter assembly through the inlet holes on the surface of the at least one filter tube and out of the filter assembly through the at least one through-going aperture in the distal flange.

12. The method according to claim 11, further comprising: adjusting the orientation of the filter assembly along a longitudinal axis of the inlet or outlet port by letting the filter assembly run on one or more inwardly tapered surfaces or projections arranged on the distal flange.

13. The method according to claim 11, wherein the filter assembly is inserted into an upper inlet or outlet port of the plate heat exchanger, and wherein the upper inlet or outlet port is arranged above the fluid level of the working medium.

14. The method according to claim 11, wherein the plurality of inlet holes is arranged substantially in a longitudinal direction of the at least one filter tube and is located substantially in the same angular position with respect to a longitudinal axis of the at least one filter tube, and wherein the filter assembly is inserted such that the plurality of inlet holes is oriented in a substantially upward direction, opposite the direction of gravity.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0026] The invention is now described, by way of example, with reference to the accompanying drawings, in which:

[0027] FIG. 1a shows a perspective view from a proximal end of a filter assembly according to one embodiment of the present invention;

[0028] FIG. 1b shows a perspective view from a distal end of a filter assembly according to one embodiment of the present invention;

[0029] FIG. 1c shows a perspective, cross-sectional view of a proximal end of the filter assembly of FIG. 1a;

[0030] FIG. 1d shows a close-up side view of a distal end of the filter assembly of FIG. 1a;

[0031] FIG. 1e shows a perspective view from a distal end of a filter assembly according to yet another embodiment of the present invention;

[0032] FIG. 2a shows a front view of a lid seal;

[0033] FIG. 2b shows a perspective view of the lid seal of FIG. 2a mounted on a proximal end of the filter assembly of FIG. 1a;

[0034] FIGS. 3a-c show a perspective view of a plate heat exchanger during different stages of mounting the filter assembly of FIG. 1a in a port of the plate heat exchanger;

[0035] FIG. 3d shows a perspective cross-sectional view of a plate heat exchanger having the filter assembly of FIG. 1a mounted in a port thereof.

DESCRIPTION OF EMBODIMENTS

[0036] In the following, a detailed description of methods and devices for filtering a fluid, such as a working medium, in a plate heat exchanger according to the present invention is provided. In the drawing figures, like reference numerals designate identical or corresponding elements throughout the several figures. It will be appreciated that these figures are for illustration only and are not in any way restricting the scope of the invention.

[0037] In the context of the present invention, the terms proximal and distal used to describe features of the filter assembly shall be understood as referring to features that are located closest to and furthest away from the operator, respectively, as seen in an insertion direction of the filter assembly into an inlet or outlet port of a plate heat exchanger.

[0038] In the context of the present invention, the terms upper and lower used to describe features of the plate heat exchanger

[0039] In FIG. 1a, a filter assembly 1 according to one embodiment of the present invention is illustrated. The filter assembly 1 has a first, proximal end 1a and a second, distal end 1b, and is dimensioned to be arranged in an inlet or outlet port 11 of a plate heat exchanger 10. The filter assembly 1 comprises a first, proximal flange 3a, a second, distal flange 3b, and at least one filter tube 4 arranged to receive an elongated filter element 2. The filter assembly 1 shown in FIG. 1a comprises seven filter tubes 4, each having a cylindrical elongated filter element 2 arranged therein. As may be understood, the filter assembly 1 may comprise any suitable number of filter tubes 4, depending on the chosen dimensions and/or application of the filter assembly 1 and filter elements 2. The filter tubes 4 are attached at respective ends to the distal flange 3b and the proximal flange 3a, respectively. The filter tubes 4 are preferably welded to the proximal flange 3a and the distal flange 3b. However, any suitable means of attachment may be used.

[0040] The filter tubes 4 each comprises a plurality of inlet holes 4a arranged linearly along the circumferential surface of the filter tubes 4 to provide fluid communication with the interior of the filter tube 4. If we consider the filter tube 4 in terms of a cylindrical coordinate system with the longitudinal axis of the filter tube 4 as the reference axis, the inlet holes 4a all have substantially the same angular position thus forming a linear row of inlet holes 4a. As may be seen in FIGS. 1a-c, the angular position of the inlet holes 4a on the plurality of filter tubes 4 is substantially the same with respect to the longitudinal axis of the respective filter tubes 4. However, the inlet holes 4a may also be arranged slightly offset with respect to each other in the angular direction, i.e. not forming a straight row. Preferably, the inlet holes 4a are all arranged on the upper side of their respective filter tube 4, i.e. oriented upwardly opposite the direction of gravity, when the filter assembly 1 is inserted into the plate heat exchanger 10, as will be explained further below.

[0041] Furthermore, as shown in FIG. 1b, the distal flange 3b comprises a plurality of through-going outlet apertures 4b, each in fluid communication with the interior of the respective filter tubes 4. The inlet holes 4a and outlet apertures 4b together provide a flow path for a fluid through the interior of the filter tubes 4. Hence, when a fluid is passed through the filter tube 4, particles and contaminations will be caught and removed from the fluid by the elongated filter element 2 arranged in the filter tube 4. The flow direction of the working medium is from the outside to the inside of the filter element 2. Each outlet aperture 4b has a diameter smaller than the diameter of the filter elements 2 such that the filter element 2 are retained inside the respective filter tube 4.

[0042] Turning now to FIG. 1c, each filter element 2 is arranged in a filter tube 4 to prevent that particles and contaminations are returned to the plate heat exchanger 10. Each outlet aperture 4b may further comprise a pipe 4c extending into the filter tube 4 to act as a guide during filter insertion. A hole on the distal end of the filter element 2 is guided onto the pipe 4c to ensure that the filter element 2 is and remains centrally aligned in the filter tube 4. Further, each filter element 2 may be pre-tensioned between the proximal flange 3a and the distal flange 3b by a biasing member, such as a compressible spring 7 acting between one of the flanges 3a, 3b and the respective end of the filter element 2.

[0043] The distal end 1b of the filter assembly 1 is shown in a close-up view in FIG. 1d. The second distal flange 3b may comprise a gasket or O-ring 18 to provide a seal against the inner lining of the inlet or outlet port 11 in the plate heat exchanger 10. Additionally, the distal flange 3b may have a beveled radial surface 3r which tapers inwardly in a distal direction to facilitate insertion of the filter assembly 1 into the plate heat exchanger 10, specifically the lining in the distal portion of the inlet or outlet port 11. As an alternative, or in addition, the distal flange 3b may comprise one or more projections (not shown) which are inwardly tapered in a distal direction of the filter assembly 1.

[0044] The filter elements 2 arranged in the filter tubes 4 may for instance be of a candle filter type including a central bore and several layers of a folded wire mesh material to create a large surface area. For filtration, flow to the candle filter is from the outside to the inside, so that mechanical filtration of the surface can be carried out. Particles and contaminations which are too big to pass through the wire mesh are retained in the space between the filter element 2 and the filter tube 4 and thus prevented from returning to the working medium in the plate heat exchanger 10.

[0045] In FIG. 1e, a filter assembly 1 according to yet another embodiment of the present invention is illustrated. The filter assembly 1 has a first, proximal end 1a and a second, distal end 1b and is dimensioned to be arranged in an inlet or outlet port 11 of a plate heat exchanger 10. The filter assembly 1 comprises a first, proximal flange 3a, a second, distal flange 3b. The filter assembly 1 shown in FIG. 1e comprises one filter tube 4 adapted to receive one elongated filter element 2 arranged therein. As may be understood, the filter assembly 1 may comprise any suitable number of filter tubes 4, depending on the chosen dimensions and/or application of the filter assembly 1 and filter elements 2. The filter tube 4 is attached at respective ends to the distal flange 3b and the proximal flange 3a, respectively. The filter tube 4 is preferably welded to the proximal flange 3a and the distal flange 3b. However, any suitable means of attachment may be used.

[0046] The filter elements 2 are preferably washable and reusable. To that end, the proximal flange 3a comprises access holes 3h (shown in FIG. 1b) through which the filter elements 2 may be inserted and removed for cleaning. A removable lid 5 is fastened to the proximal flange 3a by means of bolts to cover the access holes 3h. The lid 5 is sealed against the proximal flange 3a by a seal 8 as illustrated in FIGS. 2a and 2b. For instance, the seal 8 may be a 5 mm EPDM seal. In the lid 5 there are also provided drainage pipes 6. Each drainage pipe 6 is connected to the lower side of a respective filter tube 4, i.e. the side opposite the inlet holes 4a. The drainage pipes 6 are normally plugged but can be used to empty remaining fluid (working medium) from the filter assembly 1 before demounting of the filter assembly 1 from the inlet or outlet port 11 of the plate heat exchanger 10. The lid seal 8 has a circular opening 8a for each pipe 4 with cut-outs 8b such that the working medium is guided into each drainage pipe 6. Each circular opening 8a is dimensioned larger than the diameter of the springs 7, so that each pre-tensioning spring 7 presses directly on the lid 5.

[0047] Turning now to FIGS. 3a-3d, a method of cleaning a working medium in a plate heat exchanger 10 in accordance with a second aspect of the present invention will be described. FIG. 3a illustrates a plate heat exchanger 10 having four ports 11 (labeled T1, T2, T3, T4) providing an inlet and outlet for the working medium and a cooling or heating fluid, respectively. The ports 11 are formed by the through-going holes in the heat exchanger plates making up the plate heat exchanger 10, as shown more clearly in FIG. 3d. As may be seen in FIG. 3a, each of the ports 11 have a pipe connection on one side of the plate heat exchanger 10 (cf. T1 and T2) and a cover plate 12 on the other side (cf. T3 and T4). The filter assembly 1 according to the present invention may be used to clean the working medium flowing through the plate heat exchanger 10 but could conceivably also be used to filter particles and contaminations in the cooling or heating fluid as well. However, since the filter assembly 1 reduces the flow rate of the fluid through the plate heat exchanger 10, it is not intended to be permanently mounted, but rather mounted during a determined period of time. Also, since the working medium is circulated in a closed-loop cycle and passes multiple times through the plate heat exchanger, as opposed to the cooling or heating fluid which may pass only once through the plate heat exchanger 10, the filter assembly 1 is intended to be used to clean the working medium rather than the cooling or heating fluid.

[0048] In FIG. 3b, the cover plate 12 on the upper port 11 (labeled T4) has been removed and the filter assembly 1 is shown partially inserted. A gasket 9 is shown between the proximal flange 3a and the end frame 13 of the plate heat exchanger 10. The proximal flange 3a comprises through-going holes corresponding to the holes on the cover plate 12 to allow fastening of the filter assembly 1 in the plate heat exchanger 10, more specifically, fastening of the proximal flange 3a to the end frame. The gasket provides a fluid-tight seal therebetween. Additionally, it may be seen that the filter assembly 1 is inserted such that the plurality of inlet holes 4a in the filter tubes 4 is oriented in a substantially upward direction towards the upper portion of the plate heat exchanger, i.e. in a direction opposite the direction of gravity. Hence, as explained above, the particles and contaminations which are too big to pass through the filter elements 2 are retained in the space between the filter element 2 and the filter tube 4. Under the effect of gravity, filtered particles and contaminations move towards and remain at the lower end of the filter tubes 4. With the inlet holes 4a being oriented substantially upwardly, the filtered particles and contaminations are thus prevented from returning to the working medium in the plate heat exchanger 10.

[0049] Further, FIG. 3c shows the filter assembly 1 completely inserted in the plate heat exchanger 10 and with the proximal flange 3a fastened on the end frame 13 by means of bolts.

[0050] Preferably, the filter assembly 1 is mounted in an upper port 11 of the plate heat exchanger 10. Normally, the fluid level of the working medium in the plate heat exchanger 10 is below the upper port 11 when the closed-loop cycle in the power generation module is not running. Hence, mounting the filter assembly 1 in the upper port 11 obviates the need to empty the plate heat exchanger 10 of working medium before inserting the filter assembly 1. However, the filter assembly 1 is not restricted to being mounted in the upper port 11 but may be inserted into any of the ports 11 of the plate heat exchanger 10 having a diameter and length commensurate with the dimensions of the filter assembly 1.

[0051] FIG. 3d shows the completely inserted filter assembly 1 and the upper part of the plate heat exchanger 10 in cross section. The other upper port 11 (labeled T1) is here shown more visibly. The distal end 1b is aligned with the distal opening of the port 11. The distal flange 3b is accommodated in the distal opening and the O-ring 18 on the distal flange 3b provides a fluid-tight seal against the lining of the port 11 in the opening on the opposite end frame.

[0052] In one exemplary embodiment, the entire filter assembly 1 weighs approximately 45 kg and the filter elements 2 are preferably 5 m-filters having a length of approximately 520 mm. The filter tubes 4 can have different lengths depending on the construction (thickness and number of plates) of the plate heat exchanger 10. However, preferably the same type of filter elements 2 is used for all applications. Thus, additional springs 7 and washers are added to compensate for the different dimensions. At a pressure drop of 0.5 bar the filters will provide a flow rate of approximately 4.5 l/s. I.e. with a volume of 600 litres of working medium in the power generation module, the complete cleaning procedure can be performed in a couple of minutes. However, it is preferred that the working medium is circulated through the filter assembly 1 for at least 15 minutes.

[0053] The foregoing description of the preferred embodiments of the present invention is provided for illustrative and descriptive purposes. It is not intended to be exhaustive or to restrict the invention to the variants described. Many modifications and variations will obviously be apparent to one skilled in the art.