CONDENSER

AREA OF INVENTION

The present invention relates to a condenser for condensing a gaseous medium into a liquid medium. Specifically, the invention relates to a condenser for condensing vapour or steam using the concept of a plate heat exchanger.

BACKGROUND OF INVENTION

A condenser is disclosed in DE 197 12 148 C1 , specifically a head condenser. The condenser comprises several heat exchanging plates arranged in a pack. The pack is mounted in a cylindrical column comprising vapour that should be condensed. The vapour enters the plate pack from the top and the condensate exits the plate pack from the bottom. A cooling medium is introduced between each second plate via ports.

Plate heat exchangers have been extensively used for heat exchange between two fluids, but a plate heat exchanger is normally not very well suited for use as a condenser. Attempts have been made for using the plate heat exchanger as a condenser, as shown in for example US 4182411 , which discloses a condenser having heat transmitting surfaces, which comprises two types of heat transmitting plates alternately arranged side by side to define alternate passages for cooling liquid and steam so that the steam is condensed on the heat transmitting surfaces on the steam passage side. The heat transmitting surfaces are formed with grooves and ridges which are recessed in and raised above the base surface, thereby providing a condensate discharging mechanism comprising vertical grooves and inclined grooves for each given region on the condensing and heat transmitting surfaces, and longitudinal grooves are formed between the inclined grooves of said condensate discharging mechanisms.

DISCLOSURE OF INVENTION

An object of the present invention is to provide a condenser of the plate heat exchanger type, which is adapted for being efficient for the condenser operation.

According to an aspect, there is provided a plate condenser for condensing a vapour, comprising: at least two rectangular heat exchanging plates and two end plates arranged at a distance from each other to form at least one vapour space and at least one cooling medium space; an inlet port and an outlet port arranged adjacent respective transversal edges of said heat exchanging plates for passing a cooling medium through the cooling medium space in a substantially longitudinal direction; wherein inlet openings for the vapour are arranged along at least the longitudinal edges of the heat exchanging plates for passing said vapour through the vapour space in a substantially transversal direction thereby forming a cross-flow with said cooling medium flow. According to an embodiment, each heat exchanging plate may be arranged vertically and may comprise: a transversal sealing member arranged at a bottom transversal side of the heat exchanging plate, and longitudinal sealing members arranged at a bottom portion of the longitudinal edges of the heat exchanging plate and extending a predetermined length upwards from said transversal sealing member, thereby limiting the inlet opening for the vapour to the heat exchanging plate edges located above said longitudinal sealing members. The pre-determined length may be at least 25% of the width of the plate, such as 50%, 75%, 100% or 125% of the width of the plate.

In another embodiment, the plate condenser may further comprise guide members forming condensation channels extending from adjacent the longitudinal edges of the plate towards the centre of the heat exchanging plate and being angled downward towards the centre. The heat exchanging plate may comprise a first pattern which is skewed forming a wall of a longitudinal flow channel on one side of the plate, and a wall of a flow channel parallel to the guide members on the other side. The heat exchanging plate may comprise a second pattern in the area between said longitudinal sealing members.

In a still further embodiment, the plate condenser may further comprise a channel arranged at the centre of the heat exchanging plate in a longitudinal direction for guiding a flow of condensed vapour along the channel towards a collecting tray. Longitudinal sealing members may be arranged in the centre of the channel for forming a partly closed flow path; and openings may be arranged in the sealing members for passing gases, such as uncondensed vapour and inert gases, into the interior of said flow path.

In a yet other embodiment, a first plurality of heat exchanging plates may be arranged adjacent each other to form alternating cooling medium spaces and vapour spaces, and a second plurality of heat exchanging plates may be arranged adjacent each other to form a gas cooling section, whereby said gases may be passed to said second plurality of heat exchanging plates for condensing uncondensed vapour and sub-cooling of inert gases.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects, features and advantages will appear from the following detailed description of several embodiments of the invention with reference to the drawings, in which: Fig. 1 is a front view of a plate showing the condensation side in a plate condenser according to a first embodiment;

Fig. 2 is a front view of a plate showing the condensation side in a plate condenser according to a second embodiment;

Fig. 3 is a front view of the plate according to the second embodiment, taken along the circle line Ill-Ill in Fig. 2;

Fig. 4 is a front view of the plate according to the second embodiment, taken along the circle line IV-IV in Fig. 2;

Fig. 5 is a cross-sectional view taken along line V-V in Fig. 4;

Fig. 6 is a front view similar to Fig. 4 of an alternative embodiment; Fig. 7 is a cross-sectional view similar to Fig. 5 of the alternative embodiment of Fig. 6;

Fig. 8 is a front view of a plate showing the condensation side in a plate condenser according to a third embodiment;

Fig. 9 is a perspective view of an assembled plate condenser according to a fourth embodiment;

Fig. 10 is cross-sectional view of an assembled plate condenser for a large plant;

Fig. 1 1 is a horizontal sectional view of the condenser according to Fig. 10 taken according to line Xl-Xl of Fig. 10; Fig. 12 is a transversal sectional view of the condenser according to Fig. 10, taken according to line XII-XII of Fig. 10.

DETAILED DESCRIPTION OF EMBODIMENTS

In a plate condenser, the cross sectional area of the vapour flow path should be large enough to give a more or less negligible pressure drop. The pressure drop is proportional to the flow velocity in power two, which means the sectional area has a very large influence on the pressure drop. Since no vapour has condensed when the vapour enters the flow channel, the area of the inlet is of importance. This is especially important for steam at very low pressure, below atmospheric pressure. Consequently, the inlet port arrangement used in a conventional plate heat exchanger is not suitable for a plate condenser. In a conventional plate heat exchanger, the inlet and outlet openings for the heat exchanging media are arranged adjacent the transversal edges in the form of ports, so that the two heat exchanging media pass in a parallel flow on respective sides of the plate, usually in a counter- current flow.

If the inlet area is small, the pressure drop along the path through the inlet ports will be high. If the temperature of the vapour is close to the condensing temperature before the inlet, a lowering of the pressure because of the pressure drop will lower the condensing temperature, which means that the cooling medium is required to have a lower temperature in order to promote condensation. Moreover, if there are non-condensable gases in the vapour and as the vapour condenses, the partial pressure of the vapour will decrease which also reduces the condensing temperature.

Moreover, at high speed of the steam, there will be a lowering of the pressure in the middle of the flow in accordance with Bernoulli's equation, which further reduces the efficiency.

In the embodiments described below, the inlet and outlet ports of a conventional plate heat exchanger are replaced by using the longitudinal edges of the heat exchanger as inlet passages. Moreover, one of the transversal edges may be used as well. The cooling medium is introduced and exits via ports arranged close to the transversal edges. Thus, the two media essentially flow in a cross-current flow. By removing the inlet ports for steam, a larger heat exchanging area is obtained. Moreover, a minimization of the condensing path length results in a larger efficiency.

Fig. 1 shows a plate for use in a plate condenser according to a first embodiment. Several plates 1 , at least two heat exchanging plates and two end plates, are arranged one behind the other to form two types of spaces. One of the types of spaces comprises the vapour to be condensed and the other type of spaces comprises a cooling medium, normally a liquid cooling medium, such as water. The vapour spaces and the cooling medium spaces are arranged alternatingly, so that a vapour space is followed by a cooling medium space which is followed by a vapour space, and so on.

The heat exchanging plates are rectangular and are arranged with one of the short edges as the bottom edge. The plates are provided with a surface pattern (not shown), such as corrugated, and the corrugations interact to separate and support the plates.

The plates may have other shapes, such as substantially oval, trapezoidal or triangular.

The cooling medium space is closed at the outer edges of the plate 1 by seal means, such as a rubber seal, or is permanently sealed by welding, brazing or gluing. The cooling medium enters the sealed space via an inlet port 2 at the bottom of the plate and exits the sealed space via an outlet port 3 at the top of the plate. The other direction is also possible, from the upper port 3 to the bottom port 2.

The vapour space is open along the longitudinal edges 11 , 12 so that vapour may enter from the two longitudinal edges as shown by arrows 13, 14. The vapour space is sealed along the transversal edges 15, 16 by sealing members 17, 18 so that steam cannot enter the vapour space from the transversal edges.

The bottom transversal sealing member 18 extends a predetermined distance up along the longitudinal edges by means of sealing members 19 and 20, which are formed integrally with the transversal sealing member 18.

A tray 21 is arranged below the bottom transversal edge 16 for collecting condensed steam, i.e. water, which exits through an opening in the bottom transversal sealing member 18.

The plate condenser according to the first embodiment operates as follows, in an example.

A cooling medium is introduced through port 2 and exits via port 3. The flow may alternatively be in the other direction. The cooling medium can be water, such as sea water, at a temperature of maximum 30 ⁰ C which is heated to a temperature of

about 35°C before it exits the port 3. Other cooling medium could be oil. Other temperatures can be used. When using sea water as cooling medium, the condenser can be designed for an inlet temperature of 27°C, because the sea water very seldom has a higher temperature. A sufficient temperature difference δT may be between 5°C and 10 ⁰ C, but during winter time it can be much larger. Steam at a pressure of about 55 mBar enters the plate condenser as shown by arrows 13 and 14. The steam at this pressure condenses at a temperature of about 35°C. Heat is transferred from the steam to the cooling medium via the plate and the steam successively condenses along the path indicated by arrows 13 and 14 towards the middle of the plate. Thus, the vapour and the cooling medium flow in crossing directions essentially perpendicular in relation to each other, so called cross-flow.

The condensed steam, i.e. water, flows downward towards the bottom transversal edge 16 and into the tray 21 , where it is collected and removed via an outlet 22. During the flow downwards, the condensed water is further cooled to a temperature below the condensing temperature at the prevailing pressure, in order to prevent reformation of steam if the pressure becomes lower.

Since the cooling water is cooler closer to the inlet 2, the arrows 13 and 14 closest to the inlet 2 are shown thicker in order to illustrate that more steam is condensed, because of the large temperature difference. The arrows closest to the outlet 3 is shown narrower in order to illustrate that less amount of steam is condensed because the cooling medium is warmer compared to the temperature at the inlet 2.

Although the arrows 13 and 14 have been shown to be straight lines, the steam may follow another path. For example, the steam at the top of each sealing member 19 and 20 would have a tendency to flow slightly downward towards the tray 21. Thus, the sealing members 19, 20 are dimensioned so that they extend at least a sufficient length so that any steam entering at the top edge of the sealing member will have a sufficient length to travel in order to condense. Thus, the sealing member may extend upwards at least a length corresponding to 25% of the width of the plate. The length may be longer than 25%, such as 50%, 75%, 100% or even 125% of the plate width. In this way it is ensured that the water after condensation will flow

along the cooling surface in order to be cooled to a still lower temperature than the condensing temperature, i.e. sub-cooled.

The upper sealing member 17 may be superfluous and can be removed. In this case, also most or all of the steam entering at the top side edge 15 will condense, which further improves the capacity. Since the flow of the cooling medium is radially towards the port 3 and since the vapour flow is essentially tangential to the port 3, also in this area a cross-flow is obtained.

By the arrangement of the plate condenser, a central area is obtained, the area between the arrows, in which condensed water flows downwards to the outlet. The central area increases in area from the top toward the bottom, and so does the amount of water that passes the area. Thus, it is ensured that correct flow conditions prevail. The operation is more or less self-adjusting.

When the steam is condensing on the plate surface, a water film is accumulated on the surface. Such a water film will reduce the efficiency of heat transfer between the steam and the cooling medium via the plate, because water has lower heat transfer coefficient than the plate. In addition, the steam inevitably contains some inert gases, such as noble gases, which cannot condense. Such inert gases will accumulate outside the water film and reduce the efficiency still further. The vapour is required to diffuse through the accumulated gases until the vapour can condense. Thus, it is important to remove the water film and inert gases as efficiently as possible.

Furthermore, water condensing at the upper part of the plate, close to the longitudinal edges 11 , 12 will flow downwards and partly block the entrance for steam intended to enter there below or build up a large water film.

In a second embodiment, the plates of the condenser are provided with guide members as shown in Fig. 2.

The plate condenser according to the embodiment of Fig. 2 comprises several plates 31 each having a longitudinal edge 32, 33 and transversal edges 34, 35. Each plate has an inlet port 36 and an outlet port 37 for a cooling medium. The ports are sealed by first and second rubber seals 38, 39 and 40, 41. The reason for having two seals is for increased sealing properties and increased safety. The area between the rubber seals is drained.

Each plate is provided with several guide members 42, 43, which are arranged from each longitudinal edge towards the middle of the plate and are angled

downward to the centre of the plate. The arrangement of the guide members appears more closely from Fig. 3 which is a front view taken along the circle line Ill-Ill in Fig. 2.

As shown in Fig. 3, the guide members 42 may be pressed ridges which form barriers extending across the width of the vapour space so that any vapour condensing at the heat exchanging plate sides flows down to the guide members 42 and further on towards the centre of the plate, due to the angle. The vapour or steam entering the space between two guide members is forced to follow the same path with an angle downwards.

The angle of the guide members in relation to the transversal axis may be between about 1 ° and 45°, such as between about 5° and 25°, for example about 15°.

The heat exchanging plate pack may be arranged essentially vertically. The plate pack may have a slight angle towards the vertical in the plane of the plates, as long as the guide members still have an angle downwards. Thus, the plate pack may have an angle in relation to the vertical, which is smaller than the guide member angle. In the other plane perpendicular to the plane of the plates, the plate pack may have any angle that still results in that the flow of the condensed water is towards the bottom transversal edge.

In the centre of the plate, there is arranged a channel between two ridges 44. The ridges comprise several small openings 45. The arrangement of the ridges 44 and openings 45 appears more closely from Fig. 5 which is a transversal sectional view taken along line V-V in Fig. 4.

The central area of the plate has corrugations with reduced pressing depth in order to form a channel with very low flow resistance. An alternative embodiment of the ridges is shown I Figs. 6 and 7, in which rubber seals are arranged in recesses 55 in the plate. The rubber sealings extend from one plate to the other as shown in Fig. 7 or may be in the form of a first rubber sealing extending halfway from one plate and a second rubber sealing extending the other halfway from the other plate. The opening 45 is formed in the rubber sealings as shown to the right in Fig. 7.

As shown in Fig. 2. the interior area of the ridge 44 is connected to a ring- shaped area formed between the second rubber seal 39 and a third rubber seal 46.

The ring-shaped area is at the bottom edge connected to a tray 53 as shown in Fig. 2.

As in the embodiment of Fig. 1 , sealing members 47, 48 are arranged along the bottom portion of the longitudinal edges, as explained in connection with Fig. 1. Between the third rubber seal 46 and the respective sealing members 47, 48, there are formed outlet channels 49, 50 for exit of condensed water.

The operation of the second embodiment is as follows. Steam enters the plate condenser from the longitudinal edges. The steam flows in parallel with the guides and is directed slightly downward. Because of heat transfer from the steam to the plates and to the cooling medium at the other side of the plate, the steam condenses on the plate surface. The condensed steam, i.e. water, flows downwards until it reaches the guide member 42, 43 where it is collected and flows along the guide member 42, 43 towards the centre of the plate, which means that water flowing downward will not form a thick film of condensate which will reduce the heat transfer. The thermal conductivity of water is much lower than the thermal conductivity of the plate.

Water reaching the middle ridge 44 will pass along the outside of the ridge 44 down to the third rubber seal 46 and along the outside of the rubber seal 46 to the outlets 49, 50.

Non-condensed gases, such as inert gases and uncondensed steam passing along the outside of the ridge 44 will be sucked in to the channel between the ridges 44 through the small openings 45 and down to the ring-shaped area between the second rubber seal 39 and the third rubber seal 46 and further to the tray 53. From there, the collected gases will be further cooled and possible non-condensed steam will be condensed and separated from the inert gases, which are emitted. Such inert gases may be noble gases, such as argon, or air components, such as oxygen or hydrogen.

Any water present along the longitudinal edges is conducted on the outside of sealing members 47, 48 to trays 51 and 52 and is collected therein. Such water may be sea water leaking out through the sealings in the water channel. The plate condenser is more or less self-regulating. However, if the condensation capacity is low, this is an indication that the cooling is un-sufficient. This is remedied by increasing the flow velocity of the cooling medium. Another

action, which might not be possible to influence upon, is to increase the pressure of the vapour in order to increase the temperature difference.

The plates are provided with corrugations or surface pattern in order to form multiple support points when the plates are arranged opposite each other, as is well- known in the art of plate heat exchangers. Fig. 8 shows one example of how to arrange such surface pattern for providing a plate suitable for a condensing purpose. The middle section of the plate comprises a first pattern 57 which is slightly skewed. The first pattern is shown in fig. 3 and can be arranged for transversal flow, slightly downward, at one side, the vapour side, and for longitudinal flow at the other side, so called cross-flow. The first pattern may be according to the US Patent No. 3,783,090, the contents of which are incorporated in the present specification by reference. The pattern comprises several recesses 81 arranged substantially vertically and several ridges 82 arranged substantially horizontally, or with an angle downward towards the centre. When a first plate is arranged towards a second plate which is turned 180°, the ridges abut against each other and forms flow paths crossing each other in each second space.

In the lower section between the sealing members 47 and 48, a second pattern 58 is used, which forms vertical flow paths, both in the condensation channel and the water channel. In the upper section around the outlet port, the second pattern 59 is also used to guide the steam towards the central area. The second pattern is suitable for parallel flow, but it also allows the media to flow in a diagonal flow. The second pattern may be according to the US Patent No. 7,168,483, the contents of which are incorporated in the present specification by reference.

The longitudinal centre area of the plate substantially lacks any pattern. Thus, flow channels for the condensed water and non-condensed gases are formed in the centre area.

The first pattern and the second pattern include the possibility to have different channel gap for the cooling medium space and for the vapour space. Thus, the flow resistance can be tailored to the conditions at each side of the plates independently from each other. Such conditions may include that the vapour space has a larger channel gap than the cooling medium space. In this way, the cross sectional area of the vapour channel is increased and the pressure drop along the vapour path is decreased.

One example of a plate to be used in a condenser is the following. The plate may have a length of 1900 mm and a width of 750 mm and a thickness of 0.8 mm. The ports have a diameter of about 300 mm. The plate material may be AISI 316 Stainless steel (AISI 316 L). The pressure at the cooling medium side may be 6 Bar (gauge) and the pressure at the vapour side can be close to full vacuum. The number of plates should be less than 300 plates.

The plate condenser according to the above embodiments can be used for many different purposes. One application is as a column mounted condenser for a distillation or stripping column. The condenser can be used for condensing a wide range of vapour, from pure steam to solvents and hydrocarbons. Fig. 9 shows a fourth embodiment of the plate condenser in perspective. The plate condenser 60 comprises a plurality of plates 61 of the type shown in the first and third embodiment. An inlet tube 62 provides cooling medium, such as water, to an inlet port of the plates and an outlet tube 63 conducts the heated cooling medium.

Condensed water is emitted through a water outlet tube 64 and may be re- circulated. Non-condensed gases, such as inert gases, are emitted via a gas outlet tube 65.

The plates are arranged as a plate pack compressed by several tightening bars or straps 66, three of them are shown in Fig. 9.

The condensed water is collected in a tray 67 arranged below the bottom edges of the plates. Condensed water is removed via outlet tube 64 so that there is always a water/gas interface which is below the lower edge of the plates. In this way a gas space is formed between the water level and the bottom edge of each plate.

A sealing member 68 extends upwards from the bottom edge of the plate at a predetermined distance, which in the embodiment shown is equal to 70% of the width of the plate. This sealing member seals off the bottom portion of the inlet openings for the vapour as described above. The predetermined length of 70% of the width of the plate ensures that a sub-cooling of the condensed water will take place, which means that no vapour will form during the removal via outlet tube 64.

Moreover, a second sealing member 69 seals of the entire longitudinal edge of the inlet opening for a number of the plates arranged to the left, for example eight plates. The sealing member extends to a chamber 70 arranged above the plates and from which the gas outlet tube 65 extends.

The operation of the left portion of the plates is the following. The lower edge of the plates is in communication with the upper space of the tray 67 which comprises non-condensed gases. By means of an underpressure in the tube 65, the gases are forced to enter into the vapour space between the plates and are conducted upwards longitudinally along the plates. The gases are cooled by the cooling medium at the other side of each plate. Condensable gases, such as non- condensed water vapour will condense and flow back to the tray 67. Non- condensable gases, such as inert gases, for example noble gases, will be cooled to a temperature below the condensing temperature of the water at the prevailing pressure. Thus, it is ensured that no water vapour will be included in the gases exiting via outlet tube 65.

The plate condenser is mounted in a column 71 in the form of a cylindrical pillar, comprising the vapour to be condensed. The vapour surrounds the plate condenser 60 and may enter the vapour space between the plates via the longitudinal edges and the top transversal edge. The edges of the plates are sealed for each second plate along the entire edge in order to form the cooling medium space. For the vapour space, the plates are only sealed around the ports. The sealing may take place by welding. Compared to a conventional plate heat exchanger, which is welded along all edges, the present plate condenser according to the embodiments requires only about half of the weldings, which means a reduction of costs. The sealing may alternatively take place by rubber seals.

The plates may be made in any material which can be pressed and welded, such as a metal for example stainless steel or other more exotic material, such as titanium. The plates may be mounted in a frame with two ridged pressure plates which retains the force due to the compression of the plates. The pressure plate can either be a solid plate thick enough to withstand the load or a thin plate with reinforcements on the outer surface. In the latter case, the material costs may be reduced, which is of importance for expensive materials, such as titanium. Fig. 10 shows a plate condenser plant 100 using the plates according to the above embodiments, such as according to the second embodiment. The plant includes a steam inlet opening 101 of a diameter of 3800 mm intended for a steam velocity of 130 m/s at a pressure of 0.08 Bar absolute pressure. The pressure may

be smaller, down to essentially vacuum. The plant includes a sea water inlet tube 102 and an outlet tube 103 each having a diameter of 1800 mm and a water velocity of 2.8 m/s at a pressure of 5 Bar. There are six stacks of plates 104, 105, three of which are arranged on each side of the inlet and outlet tubes 102, 103. The cooling water inlet ports 106 of each plate are connected to the inlet tube 102 and the cooling water outlet ports 107 of each plate are connected to the outlet tube 103. Thus, cooling water flows vertically in the cooling medium spaces of each plate pack.

As shown in the top view of Fig. 1 1 and the sectional view of Fig. 12, spaces 108 are formed between the plate packs 104 so that steam entering the steam inlet opening 101 can pass between the plate packs 104 and enter the vapour spaces between the plates from the edges and from the top as shown by arrows 1 12.

As shown in Fig. 12, the collection tray 109 of each bundle of plates extends by an extension 1 10 down into a common collection tray 1 1 1 . Water is removed from the collection tray 1 1 1 so that the water level is substantially constant in the tray. The plate condenser according to the above described embodiment has several advantages over previously known condensers, such as being cheaper and thermally better, which is due to the good thermal and mechanical properties of a patterned corrugated plate.

The system in which the plate condenser according to the invention operates can be described as follows: A system for exchanging heat between two fluids, one of which is a vapour or steam to be cooled to form a condensed vapour, and the other of which is a cooling media that is warmed by heat from the vapour, comprising sources for the vapour and the liquid that exchange heat in a plate heat exchanger, collectors for the condensed vapour and the warmed cooling media that leave the plate heat exchanger, and the plate heat exchanger comprising a number of heat exchanging plates. The plate condenser uses the sides formed by the longitudinal edges of the heat exchanger plates as inlet passages for the vapour. Also one of the transversal sides (edges) may be used as inlet passages. The cooling medium is introduced and exits via ports arranged close to the transversal edges. Thus, the two media essentially flow in a cross-flow. The heat exchanging plates are arranged one behind the other to form two types of spaces. In the first types of spaces the vapour to be condensed are comprised and in the other type of spaces the cooling medium are comprised. The vapour spaces and the cooling medium spaces are arranged alternatingly, so that a

vapour space is followed by a cooling medium space which is followed by a vapour space, and so on.

The cooling medium space is closed at the outer edges of the heat exchanger plates by a sealing. The cooling medium enters the sealed space via an inlet port at the bottom of the plate and exits the sealed space via an outlet port at the top of the plate. The other direction is also possible, from the upper port to the bottom port.

The vapour space is open along the longitudinal edges so that vapour may enter from the two longitudinal edges. The vapour space may be sealed along the transversal edges by sealing members so that steam cannot enter the vapour space from the transversal edges.

A collector tray is arranged below the bottom transversal edge for collecting condensed steam, which exits through an opening in the bottom transversal sealing member.

The cooling medium can be water, such as sea water. Other cooling medium could be oil.

The method of using the invention can be described as follows: vapour or steam at a certain pressure enters the plate condenser along the longitudinal edges. Heat is transferred from the vapour or steam to the cooling medium via the heat exchanger plate and the vapour or steam successively condenses as it is transported or moved towards the middle of the heat exchanger plate. Thus, the vapour and the cooling medium flow in crossing directions essentially perpendicular in relation to each other, so called cross-flow. The condensed vapour or steam flows downward towards the bottom transversal edge and into the collector tray, where it is collected and removed via an outlet. The heat exchanger plate can alternatively be provided with guides extending from each longitudinal edge towards the middle of the plate and are angled downward to the centre of the plate, whereby the vapour or steam flows parallel with the guides and is directed slightly downward. The condensed vapour or steam flows downwards until it reaches the guide where it is collected and flows along the guide towards the centre of the plate. In the centre of the heat exchanger plate, there is arranged a channel between two ridges, and the condensed vapour or steam flows downward along the outside of the ridge towards the bottom transversal edge and into the collector tray, where it is collected and removed via an outlet.

During the flow downwards through the heat exchanger channel, the condensed water is further cooled to a temperature below the condensing temperature at the prevailing pressure, in order to prevent reformation of vapour or steam if the pressure becomes lower.

Above, several embodiments of a plate condenser have been described in great detail. However, the invention is not limited to the described embodiments, but may be altered in many respects, for example by combining the different features in other manners than described. The invention is only limited by the appended patent claims.