EP4643073A1

EP4643073A1 - Heat exchanger with welded internal exchange plates

Info

Publication number: EP4643073A1
Application number: EP23855878.7A
Authority: EP
Inventors: Tomislav MARKOVIC; Dragoslav PETKOVIC
Original assignee: Euro Heat Doo
Current assignee: Euro Heat Doo
Priority date: 2022-12-26
Filing date: 2023-12-11
Publication date: 2025-11-05
Also published as: WO2024144411A1; RS67070B1; RS20221182A1

Abstract

The heat exchanger with welded internal exchange plates belongs to the field of devices for efficient heat exchange intended for application in refrigeration technology and it solves the problem that occurs in brazed exchangers with frequent braze damage and sensitivity to the harmful reaction between ammonia and copper. This is achieved by having the heat exchanger (1) comprising a casing (2) detachably closed with a cover (17), which casing (2) accommodates the register (3) made of welded internal plates (4) preferably of 0.5 mm thick acid-resistant stainless steel, which have circular openings (9), interconnected by a set of inlet ports (6) and outlet ports (7) forming a network of herringbone conduits, with fins made at an angle of 30°, and with ring seals (31) inserted between the internal plates (4) to direct the flow of fluids (10, 11) through the tubes (5).

Description

HEAT EXCHANGER WITH WELDED INTERNAL EXCHANGE PLATES

Technical field

The technical field covering the invention generally belongs to the field of thermodynamics, or heat exchange mechanisms, and in particular refers a plate counterflow heat exchanger with a welded internal plates register design.

According to the International Patent Classification (IPC, 2022), the object of the invention is classified and marked with the primary classification symbol F27D 17/00, which refers to arrangement for using waste heat, and the secondary classification symbol F28D 7/08, which refers to heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the conduits being otherwise bent.

Technical problem

The technical problem that is solved by the present invention comprises the following: how to solve, structure-wise, a plate heat exchanger intended for use in refrigeration technology, especially in chillers and heat pumps, which enables efficient heat exchange with a high degree of utilization, is characterized by good sealing, constancy of the distance between and strength of internal plates, with internal plates joined to each other by the TIG welding process without using a filler material, so that the risk of corrosion is eliminated at the welding points, the resistance to aggressive fluids is achieved and the damage that often occurs in classic brazed exchangers is minimized, while at the same time mechanical cleaning, repair, replacement, reparation is greatly facilitated, resistance to high temperatures and pressure differences is increased with channels on the internal plates profiled in herringbone shape and of such dimensions that they allow an efficient turbulent fluid flow, and therefore maximum exchange efficiency.

Background art

Knowledge of heat exchange mechanisms has recently been particularly used in heat exchangers, i.e. heating or cooling devices in which heat is exchanged between two or more fluids in order to heat one and cool the other. Heat exchangers are widely used today for heating (water heaters, radiators, calorifiers, recuperators in chillers and heat pumps), and in refrigeration technology (condensers, crystallizers, dryers, extractors, distillers, etc.). Their application has been extended to the field of thermal energy and nuclear plants.

Heat exchangers are most commonly divided into recuperative and regenerative. In recuperative exchangers (recuperators), the gas streams are separated by a solid wall which also serves as the exchange surface, while in regenerative exchangers the role of the exchange surface is played by the accumulation honeycomb structure that can be fixed or rotating.

It is also well known that recuperators differ by the direction of fluid flow over the exchange surface, so there are direct, counterflow and crossflow types of recuperators.

With the increase in the price of energy sources and their deficit in a large number of countries, recuperators are gaining in importance as devices that achieve significant energy savings, so plate heat exchangers are now widely used for energy saving in industry, crafts, hotels, hospitals, sports halls, office buildings, drying devices, etc.

By review of available patent documentation and professional literature in the subject field, as well as promotional materials of numerous companies engaged in the production of heating and cooling equipment, the following was found:

European patent application EP3088830A1 published on 2016-11-02 discloses a plate heat exchanger applicable to heat pumps with heat exchange device consisting of plate exchangers having herringbone fluid flow conduits, with plate ends having symmetrical opposite circular openings through which exchange fluids enter and exit the exchanger. The exchanger is designed so that the internal plates are arranged horizontally and vertically in relation to the fluid inlet ports on the exchanger, separated from each other, so that they form two bundles of conduits through which the fluids flow in opposite directions, as a result of which heat exchange occurs. From the application draft, it can be observed that the inlet ports to the register are narrow, which prevents flow turbulence, while the exchanger plates are connected by brazing, which has a number of unfavorable effects (ammonia and copper reaction, braze cracking, difficult repair, etc.).

European patent application EP2650633A2 published on 2013-10-16 entitled "Plate-type heat exchanger, method of manufacturing the same, and heat pump device" discloses a device that contains a stack of a plurality of heat-transfer plates, with an inlet port and an outlet port for refrigerant, and an inlet port and an outlet port for water, as well as an oil-recovery port with an exchange body composed of rectangular plates on which there is a set of conduits that form recesses and protrusions where flow turbulence occurs, with exchange plates made to form tubes for the passage of separate exchange fluid flows. Each of the exchange plates also serves to supply and discharge both fluids, which are separated and whose inlet and outlet ports are separated by seals, but it is visible that a large part of the exchange plate surfaces is not used, so the efficiency of this type of exchanger is reduced. The exchange plates are connected by brazing, implying the usual problems this process causes.

European patent application EP3415854A1 published on 2018-12-19 entitled "Heating and hot water supply system with a plate heat exchanger" discloses a plate heat exchanger consisting of a series of interconnected exchange plates with herringbone conduits of rectangular cross-section that allow exchange fluids to flow between the parallel circular openings at the ends of the exchange plates connected to the inlet and outlet ports for the refrigerant and heat transfer fluid. Fluid flow conduits have a rectangular cross-section, which is not the most favorable for the fluid flow itself, as this cross-section does not allow the most favorable flow rate to pressure ratio in the conduits. In addition, this device is made by brazing.

European patent application EP2503277A1 published on 2012-09-26 entitled "Plate heat exchanger for heat pump applications" discloses a simple design plate heat exchanger with reduced fluid pressure loss and increased heat transfer efficiency. The plate register is designed with exchange plates made of a herringbone conduit network, stacked so that they intersect each other by connecting conduit lines, and forming at the points of intersection, virtual edges that represent the deflectors of the turbulent fluid movement, resulting in heat exchange on the exchanger, after which the heat transfer fluid goes to the heat pump. This heat exchanger design is quite complex to control, maintain and repair, and at the same time has a lower degree of exchanged heat utilization.

American patent application US2009008073A1 published on 2009-01-08 entitled "Method of manufacturing a plate heat exchanger" discloses a technical solution for the exchanger formed by brazing the exchanger plates which are symmetrically divided into two equal halves rotated by 180° and designed so that the conduits and protrusions of one half of the plate are connected each to two parallel circular outlet ports on one end of the plate, while the network of conduits and protrusions of the other half of the plate is connected to circular openings on the other end of the plate. When connecting the exchange plates to the register, fluid flow passages are formed that are independently separated so as to ensure a flow without fluid mixing, during which heat is exchanged which is then used on the distribution devices. In the description of the invention, the inventor stated that exchange plates are connected by brazing with the option to be connected by welding, gluing, etc. This device is also complex to maintain, especially to replace exchange plates in case of failure, i.e. when doing mechanical cleaning.

Dissatisfied with the existing technical solutions, primarily their insufficient cost-effectiveness and efficiency, as well as to eliminate the shortcomings related to insufficient resistance to aggressive fluids, ease of maintenance, and longevity of the devices themselves, the inventor has decided to design a new constructive solution, which is shown in the drawing with this description and explained in detail in the text that follows.

Disclosure of invention

The proposed constructive solution of the heat exchanger with welded internal plates solves the previously defined technical problem.

When working on the construction of the exchange plate register, which is the most important part of the exchanger, the inventor used the knowledge that copper brazes are prone to cracking after a certain period of operation, due to variations in temperature and pressure, noting that due to the lack of resistance to aggressive fluids at the brazing points, harmful reactions between ammonia and copper develop, which is why their application is partially limited to objects with special health criteria, which is completely avoided by applying the solution of the subject invention. A special problem is that, in case of brazing caused damage, repair requires the use of a vacuum chamber, which significantly complicates the production process, and it is often impossible to carry out a quick repair. Accordingly, the internal plate brazing process has been replaced by a much simpler TIG welding process, with a number of advantages reflected in the simplification and increase in the heat exchanger production speed, increase in functionality, the simplification of repairs and easier maintenance in cases of breakdowns, clogging, problems in operation, replacement of defective parts, etc.

The novelty of the invention also lies in the fact that the fluid connections on the subject exchanger have different diameters and are easily replaceable, so exchangers are not batch installed, but are adjusted to customer requirements and in accordance with the designed optimal power, which increases the efficiency of energy savings increases by up to 5%.

The essence of the invention is also the shape of the inlet and outlet ports on the exchange plates, which form in the register a network of conduits for fluid flow and are designed to have a herringbone pattern with fins at a certain angle, precisely sized depth and mutual distance, which achieved a favorable turbulent fluid flow profile with maximum heat exchange, regardless of pressure drop and impurity deposition.

The novelty of the invention is also reflected in the fact that, according to the invention, the layout of inlet and outlet ports on the internal plate is designed so that the exchange fluid flow through the exchanger connections takes place without a direct contract. Apart from achieving a higher degree of heat transfer, such profiling ensures greater rigidity and strength of the exchanger register.

The newly constructed plate heat exchanger, according to this invention, has several advantages compared to previously known technical solutions, the most important of which are: low degree of utilization dependence on the fluid flow rate;

- greater resistance to aggressive substances passing through the exchanger; greater service life of internal exchange plates; higher degree of exchanger efficiency; faster and easier repair in case of certain downtimes and malfunctions.

Brief description of drawings

In order to make the invention easier to understand, as well as to show how it can be concretized, only for the sake of illustration the inventor refers to the attached drawings that relate to the subject application, wherein:

- Figure 1 shows the axonometric projection of the heat exchanger with welded internal plates in front view;

- Figure 2 shows the appearance of the subject heat exchanger with a partially cut cover;

- Figure 3 shows K-K vertical section of the heat exchanger;

- Figure 4 shows the front view of the cover;

- Figure 5 shows A-A vertical section of the cover;

- Figure 6 shows B-B section of the fixing screws openings;

- Figure 7 shows the rear view of the rear casing panel;

- Figure 8 shows D-D section of the rear casing panel;

- Figure 9 shows the enlarged detail E on the rear casing panel;

- Figure 10 shows the axonometric projection of the casing in front view;

- Figure 11 shows the front view of the casing;

Figure 12 shows C-C section of the casing;

- Figure 13 shows the front view of the front end plate;

- Figure 14 shows I-I section of the front end plate;

- Figure 15 shows the rear view of the rear end plate;

- Figure 16 shows the side view of the rear end plate; Figure 17 shows the inlet side view of the register connection when it comes to the condenser, or the outlet side view when it comes to the evaporator;

- Figure 18 shows F-F section of the inlet side view of the register connection when it comes to the condenser, or the outlet side view when it comes to the evaporator

- Figure 19 shows the inlet side view of the inlet connection on the casing;

- Figure 20 shows G-G section of the inlet side view of the inlet connection on the casing;

- Figure 21 shows the outlet side of the outlet connection on the casing;

- Figure 22 shows X-X section of the outlet side of the outlet connection on the casing;

- Figure 23 shows the front view of the deflector;

- Figure 24 shows the side view of the deflector;

- Figure 25 shows the front view of the exchanger plate with herringbone fluid flow conduits;

- Figure 26 shows cross-section of a part the register with tube rows and fluid flow representation;

- Figure 27 shows the ring seal.

Description of embodiments

By viewing the figures in the attached drawings, it is easy to notice that the inventor designed a simple Heat Exchanger 1, intended primarily for use in refrigeration technology, especially in chillers and heat pumps, the main parts of which include the metal Casing 2 and the Register 3 located in the metal casing, which register is made of welded end plates and Internal Plates 4 which are connected to form physically separate Tubes 5 for the flow of Fluids 10, 11 for heat exchange purposes. According to the embodiment of the present invention, the Internal Plates 4 for heat exchange, which can be manufactured of different materials that are good heat conductors, solid and resistant to aggressive fluids and changes in pressure and temperature, are made of acid-resistant stainless steel preferably 0.5 mm thick, noting that the thickness and type of material is calculated for each exchanger individually, depending on the size, aggressiveness of the refrigerant, that is, heat transfer fluid, operating temperature, pressure, etc. The Internal Plates 4, shown in Figure 25, are shaped by cold pressing so that, viewed from the front, they have a rectangular appearance with semicircular, convex shorter sides on which there are symmetrical, opposite Circular Openings 9, interconnected by a set of Inlet Ports 6 and Outlet Ports 7, to form a network of herringbone conduits. The sizes of the Internal Plates 4 are changed in line with the parameters defining the sizes and purpose of the exchanger, and according to the embodiment of the present invention, they are: 0.5 mm thickness, 546.5 mm length, 119 mm width, while the distance between adjacent Outlet Ports 7, or Inlet Ports 6 is 7 mm, the width of Openings 9 is 54 mm, and the angle they form with the horizontal axis line of the exchanger is 30°. Outlet Ports 7 and Inlet Ports 6, which in cross-section have the appearance of isosceles trapezoids with rounded vertices, are 1.85 mm deep, arranged in parallel, symmetrically spaced Rows 8, and connecting their opposite analogs form cassettes making up the Register 3, through which Refrigerant 10 or Heat Transfer Fluid 11 flows in every other Row 8. It should be noted that such a design of the Register 3, composed of Internal Plates 4 that form a set of Rows 8 composed of Tubes 5, achieves complete separation of Fluids 10, 11, as well as that its design is fully compliant with the US 3 A standard, making the subject exchanger suitable for use on various sanitary facilities. According to the embodiment of the present invention, the Register 3, described and shown in the drawing, Figures 15 and 16, is fixed by welding to the Cover 17 and comprises two end plates and seventy Internal Plates 4 separated from each other and sealed with Ring Seals 31, while on the front, the Register 3 has a Front Internal Plate 12, and on the opposite side it is closed by the Rear Internal Plate 13. The Front Internal Plate 12, as can be seen from Figures 13 and 14, has the same sizes and shape as the other Internal Plates 4, and also has equal Circular Openings 9, and it differs in that it has no Inlet Ports 6 and Outlet Ports 7 and has a beveled edge 26, while the Rear Internal Plate 13 differs in that it is flat on both sides and has no Circular Openings 9.

The Register 3, as seen in Figure 1, is inserted into the Casing 2, preferably made of carbon steel for low and high temperature applications used for pressure vessels ("boiler steel"), in the form of a modified hollow four-sided prism with shorter sides being semicircularly convex and, as seen in Figure 7, it is open on one side, while on the other it is closed by the Bottom 14, with the Beveled Edge 28 for easier fixing by welding to the side of the Casing 2. The upper edge of the opening of the Casing 2 is edged by integral Edge Reinforcement 15 in the form of an elliptical ring with regularly arranged, equally spaced Circular Openings 16. On the front, the Casing 2 is closed by the Cover 17, which, in terms of sizes and shape, is equal to the Edge Reinforcement 15, on the perimeter of which there are regularly arranged Circular Openings 18 corresponding to the Circular Openings 16 on the Edge Reinforcement 15, through which, by means of Screws 19 with nuts, the Cover 17 is detachably fixed to the Casing 2, noting that this detachable fixing of the Cover 17 and the Casing 2 allows a simple replacement of the Register 3 and greatly facilitates maintenance and control of the Heat Exchanger 1. Full tightness of the Casing 2 is achieved by means of the Seal 29 inserted between the Cover 17 and the Edge Reinforcement 15, which completely eliminates any mixing of Fluids 10, 11 and transfer of impurities, moisture, bacteria, etc. On the Cover 17, there are symmetrically designed vertical tubular Connections 20, 21 for the supply and drain of the Refrigerant 10. Note that the connection of the Heat Exchanger 1 to the distribution network of the exchange fluids is achieved by tubes and must be done so that their stress (thermal expansion) does not affect the Heat Exchanger 1, which is why the Connections 20, 21 are connected via a Flange Joint 22 that allows a flexible, easy-to-detach connection, which at the same time facilitates unhindered access to the Heat Exchanger 1. In the centers of the shorter rounded sides of the Casing 2, there are Circular Openings 30 with extending vertical tubular Connections 23, 24 for the supply and drain of the Fluid 11 for heat transfer from the Heat Exchanger 1 to the cooling system, that is, to the chiller or heat pump.

The plate heat exchanger method of operation is well known in the state of the art, which is why it is not explained in detail in the description of the invention, and only cases when the subject heat exchanger works as a condenser and/or evaporator are mentioned. So, for example, in the case when the subject Heat Exchanger 1 is used as a condenser, Connection 20 serves as inlet for heated freon refrigerant, while Connection 21 serves as outlet for cooled freon refrigerant, while at the same time Connection 23 supplies cold water that is heated in the exchanger and exits through Connection 24 as hot water. In the case when Heat Exchanger 1 is used as an evaporator, liquid freon refrigerant enters through Connection 21 and exits through Connection 20, while Connection 24 serves as a hot water inlet, and cold water exits through Connection 23.

As seen in Figure 1, the flow of Fluids 10, 11 is directed by means of two axially positioned Deflectors 25 designed in the form of strips, one side of which is flat, while the other has thirty- five Teeth 26, with Slots 27 in between, with Deflectors 25 placed axially along both upper edges of Register 3. Such a construction makes it possible for both fluids to move turbulently, while at the same time increasing resistance to higher temperatures and pressure differences. It is important to note that the TIG welding process without using a filler material replaced copper brazing and eliminated all the negative effects normally created by the reaction between ammonia and copper. In addition, it should be borne in mind that Register 3 is made by welding on an automatic welding machine, which in case of failure or damage allows a much easier repair or replacement, which in the case of brazed exchangers required the use of vacuum chambers.

The principle of operation of such a plate Heat Exchanger 1 based on counter-flow of physically separated fluids is well known, and its performance is simply calculated using the formula Q=k*AxAt.

In addition to the basic method shown above, a variant solution is possible, according to which the presented detachable construction is replaced by a fully welded one, which has the advantage of being more cost-effective to manufacture, as the cost of production is significantly lower, but can only be used when it comes to completely clean fluids, noting that the basic solution has a number of advantages that are reflected in easier cleaning and repair in the event of breakdowns.

Industrial and other applicability of the invention

The subject invention can absolutely be applied in companies for the production of thermal energy equipment, and even in well-equipped machine shops, and is recommended for cooling systems with chillers and heat pumps, that is, all facilities where energy can be saved using recuperators.

Heat exchangers with welded internal plates are particularly suitable for facilities with high environmental requirements.

The subject invention is suitable for batch production based on the workshop documentation that can be prepared by experts in the subject field using the description and drawings from the subject invention patent application.

Note that device's operation testing on prototypes showed excellent results regardless of whether the exchanger was used as a condenser or as an evaporator.

Claims

PATENT CLAIMS

1. Heat exchanger with welded internal exchange plates comprising a casing (2) accommodating a register (3) made of welded end plates and Internal plates (4) forming physically separated tubes (5), characterized in that, having the casing (2) of the heat exchanger (1) made preferably of carbon steel, in the form of a modified hollow foursided prism with shorter sides being semicircularly convex and, open on one side, and closed on the other by the bottom (14), with the beveled edge (28), with the upper edge of the opening of the casing (2) being edged by integral edge reinforcement (15) in the form of an elliptical ring with regularly arranged, equally spaced circular openings (16), while on the front, it is closed by the cover (17), which, in terms of sizes and shape, is equal to the edge reinforcement (15), on the perimeter of which there are regularly arranged circular openings (18) corresponding to the circular openings (16) on the edge reinforcement (15), through which screws (19) with nuts are passed by means of which the cover (17) is detachably fixed to the casing (2), the full tightness of which is achieved by means of the seal (29) inserted between the cover (17) and the edge reinforcement (15), and by having on the cover (17) symmetrically designed vertical tubular connections (20, 21), flexibly connected via the flange joint (22) to the heating or cooling system, and by having in the centers of the shorter rounded sides of the casing (2) circular openings (30) with extending vertical tubular connections (23, 24), and by having in the casing (2) on each side of the register (3) horizontally axially inserted deflectors (25) in the form of strips, one side of which is flat, while the other has thirty-five teeth (26), with slots (27) in between.

2. Heat exchanger with welded internal exchange plates, according to claim 1, characterized in that, having the register (3) secured by welding to the cover (17) and made of welded Internal plates (4) forming a set of rows (8) composed of interconnected tubes (5) made of acid-resistant stainless steel preferably 0.5 mm thick, shaped by cold pressing so that, viewed from the front, they have the appearance of a modified rectangle with semicircular, convex ends of the shorter sides, at the ends of which there are symmetrical circular openings (9), interconnected by a set of inlet ports (6) and outlet ports (7) forming a network of herringbone conduits, preferably 546.5 mm long, 119 mm wide, with a 7 mm distance between adjacent outlet ports (7) and inlet ports (6), 54 mm wide opening (9), and a 30° angle they form with the horizontal axis line of the heat exchanger (1), with the outlet ports (7) and the inlet ports (6) having a cross-section appearance of isosceles trapezoids with rounded vertices, 1.85 mm deep.

3. Heat exchanger with welded internal exchange plates, according to claim 1, characterized in that, having the internal plates (4) forming tubes (5) by connecting opposite analogs, which tubes (5) are connected to form rows (8), and by having the internal plates (4) separated from each other and sealed with ring seals (31).

4. Heat exchanger with welded internal exchange plates, according to claim 1 and 2, characterized in that, having on the front of the register (3) a front internal plate (12), while on the opposite side it is closed by a rear internal plate (13), with the front internal plate (12) being equal in terms of sizes and shape to the other internal plates (4) with a beveled edge (26) and circular openings (9), but without inlet ports (6) and outlet ports (7), while the rear internal plate (13) is flat on both sides and has no circular openings (9).

5. Heat exchanger with welded internal exchange plates, according to claim 1, characterized in that, having the register (3) made by TIG welding process without using a filler material on an automatic welding machine.