DE102009038836A1 - Plate heat exchangers - Google Patents

Abstract

The invention relates to a plate heat exchanger for the transfer of heat between two phase-changing streams or between a phase-changing stream and a liquid stream, usually in conjunction with water or low-boiling liquids, e.g. Seawater. The heat exchanger consists of a plurality of identical, successively arranged heat exchanger plates 4, between which evaporator seals and condenser seals are introduced in alternation, by tensioned by tie rods end plates 1; 11 are pressed together. The evaporator and the condenser seals are as novel frame profiles 12; 13 executed; with them, the evaporator and condenser chambers are sealed and at the same time the heat exchanger plates spaced. Preferably, the frame profiles discs made of an elastic material. The heat exchanger is corrosion resistant, inexpensive to produce; it can be disassembled and cleaned without much effort.

Description

The invention relates to a plate heat exchanger for the transfer of heat between two phase-changing streams or between a phase-changing stream and a liquid stream, usually in conjunction with water or low-boiling liquids. It is particularly suitable for use in water stills, seawater desalination plants, water purification plants as well as in refrigeration systems or heat pumps where water is used as a refrigerant. The heat exchanger is corrosion resistant, inexpensive to produce and easy to clean. Incidentally, it is characterized by low spray losses.

Plate heat exchangers are often used for process engineering applications in which both a condensation and an evaporation take place in an apparatus, wherein the heat energy of the condensing material flow is used for the evaporation of the liquid material flow. For better utilization of the heat of condensation such plate heat exchangers are usually designed in multiple stages, d. H. they have several separate evaporator and condenser chambers, which are each thermally coupled by means of heat transfer surfaces and arranged alternately one behind the other.

Mainly such heat exchangers are used for applications in which the evaporation and the condensation of water is used to either a purification of water by distillation, such as. As in seawater desalination, or thickening of liquids such. As in the sugar production to achieve.

The production of plate heat exchangers comprising a plurality of evaporator and condenser chambers, is so far material-intensive and technologically complex. In heat exchangers for low-boiling materials such as water (high specific volume in the range of ambient temperature), a relatively large plate spacing is necessary to minimize the pressure losses of the steam inlet; In addition, in each evaporator chamber, the liquid to be evaporated must be uniformly distributed in a thin layer over the entire heat exchanger surface. In addition, when necessary spraying or sprinkling of the liquid, liquid drops pass directly into the vapor collection channel, whereby a droplet deposition is required, which causes additional costs.

It is known that the individual heat transfer plates are either welded together, soldered or screwed.

For plate heat exchangers, which must be suitable for operation with corrosive liquids, such. B. plate heat exchangers for seawater desalination plants, soldering or welding joints can be used only partially due to increased risk of corrosion, so that increasingly screwed heat exchanger find application.

In heat exchangers, the plates are screwed, support structures are usually formed in the heat transfer plates, are inserted into the elastic sealing elements.

So will in WO 00/04968 Described a plate heat exchanger for desalination plants, which is composed of several serially connected, seawater resistant evaporator and condenser cells.

The plate heat exchanger allows desalination with low temperature differences between evaporation and condensation, allowing for high efficiency desalination. However, by design comparatively large plate distances are required. The production of the heat exchanger is therefore material and cost intensive.

DE 42 23 699 A1 shows a plate-shaped heat exchanger made of plastic, which is indeed corrosion resistant, the heat transfer coefficient, however, is much worse than that of a comparable metallic heat exchanger.

In DE 10 2007 028 130 discloses a heat exchanger for the distillation of liquids, which consists of a number of parallel, rectangular heat transfer plates made of seawater-resistant aluminum. Along each of two tangential end faces of the plates is arranged in each case a strip-shaped and folded at a defined angle folding surface, wherein the respective plates are spaced apart and sealed along their seaming surfaces by adhesive and rivets. As a result, the number of successively arranged, standing in thermal contact with each other evaporator and condenser chambers is formed. The supply and removal of the media takes place with distribution devices arranged above and to the side of the metal sheets.

By using the folding and gluing technique in conjunction with plates made of seawater-resistant aluminum, corrosion of the heat exchanger is reliably avoided. Also, the production of the stack of evaporator and condenser chambers is relatively inexpensive. Due to the bonding, however, a desirable disassembly is too Cleaning and service purposes are not readily possible.

Out DE 83 10 039 U1 a plate heat exchanger is known, which is composed of a plurality of successively arranged, having four openings heat exchanger plates, between which seals are made of a rubber-elastic material to form a flow channel. The metal heat exchanger plates consist of a core layer of aluminum, on which cover layers of titanium, tantalum or a chromium-nickel steel are applied.

However, the heat exchanger shown is not suitable for applications in which one or more liquid media to be evaporated.

The object of the invention is to eliminate the disadvantages of the prior art. It should be created a plate heat exchanger with good heat transfer rates, which is suitable for the transfer of heat between two phase-changing streams or between a phase-changing material flow and a liquid flow, while ensuring that the coming into contact with the streams in contact are corrosion resistant, the evaporator and capacitor cells are permanently sealed and he is a total of simple design and inexpensive to produce.

This object is achieved by the features of claim 1; Advantageous embodiments and uses of the invention will become apparent from the claims 2 to 14.

The starting point is a heat exchanger, which consists of a number of identical heat exchanger plates arranged one behind the other, between which condenser and evaporator gaskets are alternately inserted. By two heat exchanger plates and the enclosed therein evaporator seal an evaporator chamber or by two adjacent heat exchanger plates and the condenser seal a condenser chamber is formed.

The smallest functioning heat exchanger consists of three heat exchanger plates, wherein in each of the two interspaces a condenser and an evaporator seal are introduced. For optimum operational management, it is intended to construct the heat exchanger from ten or more heat exchanger plates.

The stack formed from heat exchanger plates and seals is compressed by two end plates, which are arranged on both sides of the stack and clamped with tie rods.

The heat exchanger plates have at least three openings in the edge region with a comparatively small cross-sectional area and at least two openings with a comparatively large cross-sectional area. The apertures with a smaller cross-sectional area are for the implementation of the liquid media and possibly the inert gases and those with a larger cross-sectional area for the implementation of the gaseous media, such as. As water vapor provided.

In heat exchangers used for the distillation of seawater, the heat exchanger plates are provided in the outer region with four apertures with a small cross-section, with three breakthroughs serve the implementation of the raw water, the distillate and the brine. The fourth breakthrough is used for the removal of the inert gas. Two apertures with a larger cross-section are provided for the guidance of the water vapor streams.

According to the invention, disk-like frame profiles made of an elastic material are used both as evaporator and condenser seals, which at the same time space the heat exchanger plates.

The executed as a frame profile seals thus do not serve, as usual, only the sealing of the evaporator and the condenser chambers, but are also structural elements at the same time. The frame profiles have the same outer contour as the heat exchanger plates. In this way, a compact stack of heat exchanger plates and seals is formed, which makes an additional housing superfluous.

The frame profiles of the evaporator and the condenser chambers are broken in the middle over a large area, together with the heat exchanger plates form the evaporator and condenser chambers. At the edge of the frame profiles further breakthroughs are introduced, which form in connection with the capacitor plates channels for the supply and discharge and for the distribution of the liquid and gaseous media to the evaporator and condenser chambers.

Studs between the heat transfer plates, in addition to the frame profiles, increase the mechanical stability and limit the pressure on the frame profiles.

It is envisaged that all frame profiles of the evaporator chambers have the same contour and are the same thickness. The situation is similar with the frame profiles of the condenser chambers.

If the heat exchanger is used for processes in which changing flow cross sections are required within the heat exchanger, the frame profiles are of different thickness and have different sized, the size of the Verdamfper- or condenser chambers determining, central recesses. These frame profiles are made of elastic materials that have different degrees of Shore hardness. So it is z. B. advantageous to make thicker frame profiles of a material with a larger and thinner frame profiles made of a material with a lower Shore hardness, so that all frame profiles get similar large spring constants.

For the construction of heat exchangers, in which, as hitherto customary, all heat exchanger plates are arranged parallel to each other, disc-shaped frame profiles are used, whose cross section (shape of the disc without recesses) is rectangular.

In an alternative embodiment, frame profiles are used in which the cross section is trapezoidal, wherein (again due to the disc shape), the height of the trapezoid is substantially greater than the two parallel sides of the trapezoid. Thus, heat exchangers can be produced in which the evaporator chamber expand upwards, while the condenser chambers taper upwards.

In a further variant, the frame profiles of the evaporator chambers and / or the frame profiles of the condenser chambers are provided with a plurality of elongated, parallel recesses. In connection with the heat exchanger plates, channels connected in series are thereby formed, by means of which the medium (for example water) is guided past the heat exchanger plates on a meandering path. Through this Mehrflutige flow through the evaporator and / or condenser chambers can be achieved by a suitable choice of the number and width of the channels for almost any media optimum heat transfer behavior.

The heat exchanger according to the invention can also be used as an evaporator, in which the liquid to be evaporated is trickled over the heat exchanger plates of the evaporator chambers and the condenser chambers are flowed through with heating water (water-heated evaporator), or as a condenser, in which the condenser chambers with the vapor to be condensed and evaporator chambers with cooling water be flowed through (water-cooled condenser), used. In those cells, which are traversed by heating or cooling water, there are built-in elements or the cells are multi-flow, so that high flow velocities and heat transfer coefficients are guaranteed. The frame profiles of the evaporator / condenser chambers are then about two to three times thicker than the frame profiles of the cells through which heating / cooling water flows.

The invention will be explained in more detail with reference to two embodiments; show:

1 a sectional view of the plate heat exchanger in a side view;

2 a schematic representation of the plate heat exchanger in a side view (frame profiles with rectangular cross-section);

3 : a schematic representation of the plate heat exchanger in a side view (frame profiles with trapezoidal cross section).

Between each of the front and the rear cover plate 1 ; 11 are the five parallel heat exchanger plates 4 , Between these plates are alternately evaporator frame profiles 12 and condenser frame profiles 13 arranged (s. 1 ). The evaporator frame profiles 12 form with the two adjacent heat transfer plates 4 the evaporator chambers 2 , the condenser frame profiles 13 according to the condenser chambers 3 , The chambers 2 ; 3 be through the frame profiles 12 ; 13 hermetic to the environment and adjacent chambers 2 ; 3 sealed. In addition, the heat transfer plates 4 through the frame profiles 12 ; 13 spaced apart. The frame profiles 12 ; 13 thus simultaneously fulfill the function of a sealing and structural element. In the frame profiles 12 ; 13 There are recesses, through which, with the heat exchanger plates 4 , the channels for the supply and discharge of the liquid and gaseous media in the evaporator 2 and condenser chambers are formed.

When introducing steam into the condenser chambers 3 condenses this and gives the resulting heat of condensation to the two heat exchanger plates 4 from. The heat released flows to the evaporator-side, liquid-sprinkled sides of the heat exchanger plates 4 , whereby a part of this liquid evaporates. The resulting steam rises, becomes in the steam channel 5 collected and over the steam pipe 6 removed from the heat exchanger.

The introduction of the vapor to be condensed in the individual condenser chambers 3 takes place via the neck 7 , The steam enters the room below the condenser chambers 3 and is due to a partial pressure gradient occurring there against the cool heat exchanger plates 4 driven, where it precipitates. In the process, drops form under the influence of gravity in the direction of the bottom of the condenser chambers 3 flow. Through the completion holes 8th the condensate finally reaches the manifold 9 and gets through the neck 10 removed from the heat exchangers.

The liquid to be sprinkled is over the nozzle 14 fed and through the in the condenser frame profile 13 incorporated channel 15 to the liquid chamber 17 directed. The liquid passes through finely distributed, in the heat exchanger plates 4 introduced holes 16 in the two adjacent evaporator chambers 2 , whereby the heat transfer plates 4 in the ventricular chambers 2 be sprinkled evenly.

3 shows a heat exchanger with the same principle in principle, but here instead disc-shaped frame profiles 12 ; 13 , whose outer contour has a rectangular cross section, frame profiles 12.1 ; 13.1 ; 12.2 ; 13.2 used with a trapezoidal cross-section. The cross sections of the condenser frame profile 13.1 , which is located at the beginning of the heat exchanger, and the evaporator frame profile 13.2 , which is arranged at the end of the heat exchanger, each have the shape of a rectangular trapezoid, whereas the cross sections of the other condenser 13.2 and evaporator frame profiles 12.2 each having the shape of isosceles trapezoids. The acute angles (and thus also all obtuse angles of the isosceles trapezoids) of all trapezoids are the same size. The frame profiles 12.1 ; 13.1 ; 12.2 ; 13.2 are mutually rotated by 180 ° to each other, so that in the heat exchanger alternately one long and one short parallel side of the trapezoids is next to each other.

In this way, a cuboid plate heat exchanger is formed, the evaporator chambers 2 widening towards the top and its condenser chambers 3 to rejuvenate to the top.

Through the upwardly widening evaporator chambers 2 become high flow velocities of the steam at the upper outlet in the steam channel 5 , which otherwise occur due to the volume increase in the evaporation of the medium used, largely avoided. On the one hand, the heat exchange is improved, on the other hand it is prevented that liquid droplets are entrained by the steam. The use of such evaporator chambers 2 is particularly advantageous when operating with water, since the volume of water in the transition from the liquid to the gaseous state increases to about 1000 times. For the otherwise used refrigerants, the volume ratio of liquid to steam is only 1:10 to 1: 100.

Due to the upwardly tapering shape of the condenser chamber 3 it is achieved that the condensate from the obliquely arranged heat exchanger plates 4 drain quickly. As a result, the formation of thick condensate layers on the surfaces of the heat exchanger plates 4 avoided and thus ensured a good heat transfer.

LIST OF REFERENCE NUMBERS

1

front cover plate

2

evaporator chamber

3

condenser chamber

4

heat exchanger plate

5

vapor channel

6

Steam pipe (outlet)

7

Steam pipe (entrance)

8th

drain hole

9

manifold

10

Nozzle (condensate)

11

rear cover plate

12

Evaporator frame profile

12.1

Evaporator frame profile with rectangular trapezoidal cross-section

12.2

Evaporator frame profile with isosceles trapezoidal cross-section

13

Condenser frame profile

13.1

Condenser frame profile with rectangular trapezoidal cross-section

13.2

Condenser frame profile with isosceles trapezoidal cross-section

14

Nozzle (for the liquid to be sprinkled)

15

channel

16

drilling

17

liquid chamber

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 00/04968 [0008]
• DE 4223699 A1 [0010]
• DE 102007028130 [0011]
• DE 8310039 U1 [0013]

Claims (14)

Plate heat exchanger consisting of three or more identical, successively arranged heat exchanger plates ( 4 ), between which evaporator seals and condenser seals are introduced alternately, wherein in each case by two heat exchanger plates ( 4 ) the evaporator chambers ( 2 ) and the condenser chambers ( 3 ) formed of the heat exchanger, the thus formed stacks of tensioned with tie rods or similar means end plates ( 1 ; 11 ) is pressed together, wherein the heat transfer plates ( 4 ) in the outer region have at least three openings with a comparatively smaller cross-sectional area for the liquid media and at least two openings with a comparatively larger cross-sectional area for the gaseous media, characterized in that the evaporator and the condenser seals the heat exchanger plates spaced frame profiles ( 12 ; 13 ) are formed as discs of an elastic material and the same outer contour as the heat transfer plates ( 4 ), wherein the frame profiles of the evaporator ( 12 ) and the condenser chambers ( 13 ) large, central openings, which in combination with the heat transfer plates ( 4 ) the evaporator ( 2 ) and the condenser chambers ( 3 ), and have smaller peripheral breakthroughs through which in conjunction with the heat transfer plates ( 4 ) Channels for the supply and discharge as well as for the distribution of liquid and gaseous media to the evaporator ( 2 ) and the condenser chambers ( 3 ) are formed. Plate heat exchanger according to claim 1, characterized in that between the heat exchanger plates ( 4 ) Stud bolts are introduced, the defined spacing of the heat exchanger plates ( 4 ) serve. Plate heat exchanger according to claim 1 and 2, characterized in that different frame profiles ( 12 ; 13 ) consist of elastic materials with different Shore hardness. Plate heat exchanger according to claim 1 to 3, characterized in that the frame profiles of the evaporator ( 12 ) and the condenser chambers ( 13 ) each have different thicknesses. Plate heat exchanger claim 1 to 4, characterized in that the thicknesses of the frame profiles of the evaporator ( 12 ) and the condenser chambers ( 13 ) increase or decrease depending on their position in the heat exchanger. Plate heat exchanger according to claim 1 to 3, characterized in that all frame profiles of the evaporator ( 12 ) and condenser chambers ( 13 ) have the same thickness. Plate heat exchanger according to claim 1 to 6, characterized in that in each case all frame profiles of the evaporator ( 12 ) and in each case all frame profiles of the condenser chambers ( 13 ) have the same geometry. Plate heat exchanger according to claim 1 to 7, characterized in that the frame profiles ( 12 . 13 ) have trapezoidal cross-sections, wherein the height of the trapezoid is greater than the length of the two parallel sides of the trapezoid. Plate heat exchanger according to claim 8, characterized in that the cross sections of the frame profiles ( 12.1 . 13.1 ) at the beginning and at the end of the plate heat exchanger the shape of rectangular and the cross sections of the basic shapes of the remaining frame profiles ( 12.2 . 13.2 ) have the shape of isosceles trapezoids, and correspond respectively to the acute angles of the right-angled and isosceles trapezoids, the frame profiles ( 12.1 . 13.1 . 12.2 . 13.2 ) are arranged such that in each case the long and the short parallel sides of the trapezoids lie alternately next to each other, whereby a cuboid plate heat exchanger is formed, the evaporator chambers ( 2 ) expand upwards and their condenser chambers ( 3 ) to taper upwards. Plate heat exchanger according to claim 1 to 9, characterized in that the frame profiles ( 12 ) of the evaporator chambers and / or the frame profiles ( 13 ) of the condenser chambers are provided with a plurality of elongate, parallel recesses through which, together with the heat transfer plates ( 4 ), one behind the other connected channels are formed, which serve for multi-flow through the evaporator and / or condenser chambers. Plate heat exchanger according to claim 1 to 9, characterized in that the frame profile of the evaporator chamber ( 12 ) has one of the feed line of the liquid to be evaporated serving breakthrough, which is connected to a horizontally disposed, narrow rectangular opening, which is above the evaporator chamber ( 2 ) is separated by a ridge-shaped portion, wherein the web-shaped portion on its front and its back side by side running close, the rectangular opening with the evaporator chamber ( 2 ) connecting, groove-shaped recesses, the uniform irrigation of both adjacent heat transfer plates ( 4 ) serve. Plate heat exchanger according to claim 1 to 9, characterized in that the frame profile of the condenser chamber ( 12 ) has one of the inlet of the liquid to be evaporated serving breakthrough, which is connected to a horizontally disposed, narrow rectangular opening, which is above the the condenser chamber ( 3 ) and is separated therefrom by a web-shaped section, wherein in the two adjacent heat exchanger plates ( 4 ) at the level of the rectangular opening and over its length extending, close to each other, small holes ( 16 ) are introduced, the passage of the liquid to be evaporated through the heat transfer plates ( 4 ) and a fine sprinkling of in evaporator chambers ( 2 ) located back sides of the heat exchanger plates ( 4 ) serve. Use of the plate heat exchanger according to claim 1 as a water-cooled condenser. Use of the plate heat exchanger according to claim 1 as a water-heated evaporator.

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