EP3857158B1

EP3857158B1 - A heat exchanger

Info

Publication number: EP3857158B1
Application number: EP19769831.9A
Authority: EP
Inventors: Rene Hansen
Original assignee: Athco Engineering AS
Current assignee: Athco Engineering AS
Priority date: 2018-09-27
Filing date: 2019-09-23
Publication date: 2023-06-07
Anticipated expiration: 2039-09-23
Also published as: US20220034603A1; CN113167552A; WO2020064634A1; EP3857158A1; EP3857158C0

Description

The present invention relates to a heat exchanger of the welded plate type for heat transfer between air and liquid, said heat exchanger comprising a plurality of plates with each with an internal volume inside a peripheral flange having a flange thickness, and which are in parallel fluid communication with an inlet and an outlet, said plates being mounted in a frame with a mutual predetermined distance, such that air can flow between the plates, and wherein the plates are mounted between at least two plate holding frame members on opposite sides of said plates, wherein said plate holding frame members are provided with an exterior edge and with a plurality of slits in a comb-like shape extending from said exterior edge.
A heat exchanger of such kind is known from US2006/0201660A1 or WO2016/053100A1 .
Heat exchangers of the welded plate type are also known, inter alia from US 5,494,100 , US2012/000633A1 and US2012/255709A1 .
Heat exchangers of the welded plate type are widely used in the process industry for heat transfer from one medium, such as heated air to water. The heat exchanger is made of a number of welded plates arranged in parallel in a frame between an air inlet and an oppositely situated air outlet, such that air or gas can flow through the heat exchanger from an air inlet to an air outlet. The plates are mounted in mounting frame members so that the plates are held with a mutual distance which allows air or gas to pass through the plates. Each of the plates are connected to an inlet manifold and an outlet manifold so that a fluid, e.g. process water thereby can flow inside the plates, whereby heat is transferred from the air to the liquid (or vice versa).
In the process industries, such as food and dairy industry, textile industry, chemical industry, etc., such type of heat exchanger of the welded plate type has proven effective in providing heat transfer and thereby providing substantial energy savings. The heat exchangers are typically customised in size and design.
From US2006/0201660 a heat exchanger of the above-mentioned kind is known where the plates are firmly mounted between a series of plate holding frame members on opposite sides of said plates. However, due to the thermal conditions the welded plates are subjected to the plates undergo thermal expansion. The liquid flow communication between the plates and the inlet and outlet must be sealed to prevent leaks occurring due to the thermal expansion. To address this issue there are known examples of heat exchangers from GB 1 592 069 and US 2,814,469 . However, another issue in relation to the thermal conditions the plates are subjected to is to ensure that the plates remain fixedly mounted in the frame. As the plates expand and retract it has been observed that there is a risk that the plates come lose in the mounting members, which may increase the risk of leakage as well as increased wear and tear on the heat exchanger whereby service is needed to ensure the satisfactory performance and efficiency of the heat exchanger.
In the heat exchanger disclosed in US2006/0201660 the plates are locked between the inner and the outer plate sections. Air flowing through the heat exchanger as well as thermal expansion and retractions causes vibrations and causes wear on the plates which over time causes the plates to move in their fixture.
Accordingly, it is therefore an object of the present invention to address the issues due to thermal expansion of the welded plates in a heat exchanger of the welded plate type.
This object is achieved by a heat exchanger of the initially mentioned type, wherein first type slits and second type of slits are provided in an alternating configuration, wherein the first type slits are formed with a narrow entry passage section having a width corresponding to the flange thickness and a widened opening section there behind, and wherein the first type slits are adapted to receiving the peripheral flanges of the plates in the narrow passage section; and wherein the second type slits are substantially straight and left vacant.
According to the invention it is found advantageous to arrange the plates in comb-like plate holding mounting members since this plate mounting arrangement allows for thermal expansion of the plates and holds the plates in position. The plates are held in their position in the heat exchanger without having to weld the plates to the frame. By holding the plates in a comb-like member in every first type slit, the second type slits allows for some flexibility whereby any thermal expansion in the direction of longitudinal plate holding member can also be absorbed.
The first type slits adapted to receiving the plates are formed with a narrow entry passage section extending from the exterior edge and a widened section there behind.
Furthermore, the narrow entry passage sections of the first type slits have a width substantially equal to the thickness of the peripheral flanges of the plates. Additionally, the narrow entry passage sections of the first type slits extend substantially perpendicular from the exterior edge with a length substantially corresponding to the width of the flanges of the plates. This means that the plates are held stationary so that wear is reduced or even eliminated during operation of the heat exchanger. The plate flanges are primarily held in the narrow passage section leaving the widened section in the first type slits substantially vacant, so that the plate flanges occupy the narrow passage sections only.
In a preferred embodiment, the second type slits between the plate receiving first type slits are formed with a substantially equal width.
According to the invention, the plates are preferably welded steel plates where two steel sheets are welded together at least along their peripheral flanges and are shaped such that there is an internal volume between said plates, and that the inner volume is provided with an inlet and an outlet preferably at opposite peripheral flanges. Moreover, the peripheral flange of each of the plates has a thickness substantially equal to the two steel sheets of the plate, and with a predetermined width of the peripheral flanges of the plates.
Preferably, both the first and second types of slits have an opening at the exterior edge of the frame member and extend substantially perpendicular to the exterior edge and all substantially with the same length. Hereby, any thermal expansion of the plates during operation of the heat exchanger is easily absorbed.
To ensure a firm grip on the plate flanges, it is advantageous that the narrow passage sections of the first type slits have a width substantially equal to the thickness of the peripheral flanges of the plates.
Advantageously the base of the first type slits and the base of the second type slits at the most distant point from the exterior edge are provided with a rounded finish, such as a semi-circular shaped bottom of the slits. Hereby, stresses and strains concentrations in the foot of the protrusions formed by the slits are avoided.
In order to ease the insertion of the plate flanges at least the first type of slits are provided with chamfered transitional edges or rounded edges as receiving portions defining the entry into the narrow passage sections.
In the preferred embodiment, the comb-like shaped plate holding frame members are made of steel, preferably stainless steel, and more preferably austenitic stainless steel. This makes the heat exchanger corrosion resistant and suitable for use in food production and the like.
The comb-like shaped plate holding frame members are preferably provided with a mounting portion, preferably in the form of a longitudinal inverted V-shaped, in the portion opposite the exterior edge. Hereby, the plate holding members are simple to firmly mount to the heat exchanger frame and simple to service, including replace during service. The V-shape also provides stiffness to the long comb-like shaped plate holding frame member.
In the preferred embodiment, the plates are rectangular with two side flanges and a top and a bottom flange, and wherein a plurality of plate holding frame members are arranged in the frame for receiving and retaining the plates at each of the side flanges and at the bottom and top flanges of said plates.
The plates, the manifolds and the frame and the plate mounting members are all made of stainless steel, and more preferably austenitic stainless steel. This is found advantageous since austenitic stainless steel is not hardenable by heat treatment and thereby ensures a long lifetime of the heat exchange structure.
In the following the invention is described with reference to the accompanying drawings, in which:

Fig. 1 is a perspective view of a heat exchanger according to an embodiment of the invention;
Fig. 2 is a front view of same;
Fig. 3 is a cross-sectional view of section C-C in fig. 2;
Fig. 4 is a cross-sectional view of section D-D in fig. 2;
Fig. 5 is a detailed view of detail E in fig. 4;
Fig. 6 is a top view of a comb-like shaped plate holding member according to the invention;
Fig. 7 is a detailed view of detail C in fig. 6;
Fig. 8 is an end view of the plate holding member of fig. 6;
Fig. 9 is a perspective view of the plate holding member of fig. 6, and
Fig. 10 is an enlarged detailed view of fig. 5 of the mounting of the flat flanges in the plate holding member.

In figures 1 and 2 there is shown a heat exchanger of the welded plate type. The heat exchanger comprises a series of plates 1 arranged in parallel in a frame 2. The frame 2 is generally cubical with an open front rectangular side and an opposite open rear rectangular side and four rectangular sides therebetween. The type of heat exchanger shown in the fig. 1 is an air-cooled heat exchanger where hot air passes through the frame in a flow path between the front and rear sides and is thereby cooled as the thermal energy is transferred to a liquid which is passed through the series of plates.
The plates 1 are mounted to the frame 2 via plate holding members 5, which transverses the openings on the front and rear side of the heat exchanger (only the front side being visible in fig. 1). Each of the plates 1 are provided with an inner volume inside a peripheral flange 1' (see figs. 3 and 5). Each plate 1 has an inlet (not shown) and an outlet (not shown) to provide for fluid flow into and out of the inner volume. The inner volumes of the plates 1 are in fluid communication with a fluid inlet manifold 3 and a fluid outlet manifold 4 such that fluid, e.g. a cold liquid, enters via the fluid inlet manifold 3 and passes through the inner volumes of each of the plates 1 before the fluid exits the heat exchanger via the fluid outlet manifold 4, at for instance an elevated temperature due to the air flow of hot air between the plates 1 as indicated by the arrows in fig. 1. The fluid inlet manifold 3 distributes the inflowing liquid to the plates 1 that are provided in parallel so that the liquid passing through the plates 1 is simultaneously and flows towards the outlet manifold 4.
Figure 3 is a cross-sectional view along the section C-C in fig. 2. This section C-C is parallel with the plates and in between two plates 1. As shown in figure 3 each plate 1 is held in position by a number of plate holding members 5 along their peripheral flanges 1' on at least two opposite sides of the generally rectangular plates 1. The mounting of the plates 1 in the plate holding members 5 is also shown in figures 4, which is a cross-sectional view along section D-D in fig. 2 and in further detail in figure 5, which is an enlarged view of the detail E marked in fig. 4.
With reference to in particular fig. 5 and also figures 6 to 9 that are views of the plate holding members 5 in isolation. It shown, the plate holding members 5 are elongated and they are provided with slits 6, 7 of two different types and as such the plate holding member 5 has a comb-like appearance. The plates 1 are arranged in the slits of the first type 6 in these comb-like plate holding members 5 and this mounting arrangement allows for thermal expansion of the plates 1 and holds the plates 1 in position in the frame 2. The plates 1 are held in their position in the heat exchanger without having to weld the plates 1 to the frame 2. By holding the plates 1 in a comb-like member 5 in every first type slit 6, the second type slits 7 allows for some flexibility whereby any thermal expansion in the direction of longitudinal plate holding member 5 can also be absorbed. As shown in the figures, the two types of slits 6, 7 are provided in an alternating configuration, so that a first type slit 6 is followed by a second type slit 7 which is then followed by a first type slit 6, etc.
As shown in detail in figure 7, the slits 6, 7 in the holding member 5 are alternating between a first type slit 6 and a second type slit 7 so that in between two first type slits 6 there are second type slits 7. The slits 6, 7 extend substantially perpendicular to the exterior edge 9 and all substantially with the same length from the exterior side edge 9 of the holding member 5, but the slits 6, 7 are provided with different shapes. The slits 6, 7 are formed in the holding member 5 e.g. by cutting so that protrusions 10 are formed that are essentially mirrored in shape on each side of a slit 6, 7.
The first type of slits 6 in the comb-like plate holding member 5 are adapted to receive the flanges 1' of the plates 1. The plate flanges 1' is inserted into the outermost narrow entry passage section 6' of the slits 6 (see figs. 5 and 10).
The second type slits 7 are provided between the plate receiving first type slits 6 are formed with a substantially equal width. The first type slits 6 adapted to receiving the flanges 1' of the plates 1 are formed with a narrow entry passage section 6' in the exterior edge portion and a widened slit section 6" there behind, i.e. the section of the slit most distant from the exterior edge 9 (see detail view in fig. 7).
The narrow entry passage sections 6' of the first type slits 6 have a width substantially equal to the thickness of the peripheral flat flanges 1' of the plates 1. Additionally, the narrow entry sections 6' of the first type slits 6 extend substantially perpendicular from the exterior edge with a length substantially corresponding to the width of the flanges 1' of the plates 1. The narrow passage section 6' have two parallel sides, whereby it is ensured that the flat flange 1' is both firmly gripped and retained in position due to the width of the narrow passage section 6' but can also slide in the passage 6' when thermally expanded. As shown in fig. 5 and as shown in more detail in fig. 10, the flat flanges 1' of the plates 1 are only inserted into the narrow entry passage sections 6' of the first type slits 6. Thus, the flat flanges 1' do not extend into the widened slit sections 6" or at least do not substantially extend into the widened slit sections 6". Thus further allows for a lateral thermal expansion of the plates 1 as the widened sections are left vacant or at least substantially vacant, i.e. unoccupied by plate flanges 1'.
This design of the holding member 5 with the altering two types of slits 6, 7 ensures that the plates 1 are held stationary so that wear is reduced or even eliminated during operation of the heat exchanger, whilst at the same time allowing for thermal expansion of the plates during operation.
To ease the insertion and in order to allow for thermal expansion and contraction the protrusions 10 defining the first type of slits 6 are provided with chamfered transitional edges or rounded edges as receiving portions 10' defining the entry into the narrow passage sections 6' (see fig. 7) at the exterior edge 9 and also the internal transition portions 10" between the narrow pages section 6' and the widened section 6".
The second type of slits 7 are straight, preferably with a base of the second type slits 7 at the most distant point from the exterior edge 9 being provided a rounded finish 7"', such as a semi-circular shaped bottom of the slits 7. By the term straight is meant that the second slits 7 may have two substantially parallel sides and essentially with a constant width of the slit 7. However, it is realised that other geometric shapes of the second type slits 7 may also be chosen. It is however preferred that the second type slits 7 are symmetric in shape so that the protrusions forming the slit 7 together with the two neighbouring first type slits 6 are equal in shape to ensure the same mounting support of the neighbouring plates 1.
The base of the first type slits 6 are provided with a rounded finish 6'" as the widened slit sections 6" at the most distant point from the exterior edge 9 are provided a rounded finish 6"', such as a semi-circular shaped bottom of the first slits 6. Hereby, a build-up beyond an acceptable level of internal mechanical strains is prevented in the holding member 5 such that it is prevented that the protrusions 10 break off and the plates 1 come lose.
The comb-like shaped plate holding frame member 5 is provided with a longitudinal frame mounting portion 8 formed with a longitudinal inverted V-shape in the longitudinal portion opposite the exterior edge 9. Hereby, the longitudinal plate holding member 5 is provided with bending stiffness and thereby provides for a firm mounting of the plates 1 in the heat exchanger.
The components of the heat exchanger are predominately made of steel, and in particular stainless steel so that the heat exchanger can withstand corrosion. Accordingly, the frame and the plates are preferably made of stainless steel. The plate holding members 5 are preferably also made of steel, such as stainless steel. However by the invention it is realised that other types of metal materials could be used.
Above the invention is described with reference to a currently preferred embodiment. However, it is realised that variants may be provided without departing from the invention as defined in the accompanying claims.

Claims

A heat exchanger of the welded plate type for heat transfer between air and liquid, said heat exchanger comprising
a plurality of plates (1) with each with an internal volume inside a peripheral flange (1') having a flange thickness, and which are in parallel fluid communication with an inlet and an outlet,

said plates (1) being mounted in a frame (2) with a mutual predetermined distance, such that air can flow between the plates (1), and wherein the plates (1) are mounted between at least two plate holding frame members (5) on opposite sides of said plates (1), wherein said plate holding frame members (5) are provided with an exterior edge (9) and with a plurality of slits (6, 7) in a comb-like shape extending from said exterior edge (9),

characterised in that

first type slits (6) and second type of slits (7) are provided in an alternating configuration, wherein the first type slits are formed with a narrow entry passage section (6') having a width corresponding to the flange thickness and a widened opening section there behind, and wherein the first type slits are adapted to receiving the peripheral flanges (1') of the plates (1) in the narrow passage section (6'); and wherein the second type slits (7) are substantially straight and left vacant.
A heat exchanger according to claim 1, wherein the plates (1) are welded steel plates where two steel sheets are welded together at least along their peripheral flanges (1') and are shaped such that there is an internal volume between said plates, and that the inner volume is provided with an inlet and an outlet preferably at opposite peripheral flanges.
A heat exchanger according to claim 1 or 2, wherein the peripheral flange (1') of each of the plates has a thickness substantially equal to the two steel sheets of the plate.
A heat exchanger according to any of the preceding claims, wherein both the first and second types of slits (6, 7) have an opening at the exterior edge (9) of the frame member and extend substantially perpendicular to the exterior edge (9) and all substantially with the same length.
A heat exchanger according to any of the preceding claims, wherein the second type slits (7) between the plate receiving first type slits (6) are formed with a substantially equal width.
A heat exchanger according to any of the preceding claims, wherein the first type slits (6) adapted to receiving the plate flanges in the narrow passage section (6') only.
A heat exchanger according to any of the preceding claims, wherein the narrow passage sections (6') of the first type slits (6) have a width substantially equal to the thickness of the peripheral flanges (1') of the plates (1).
A heat exchanger according to any of the preceding claims, wherein the narrow passage sections (6') of the first type slits (6) extend substantially perpendicular from the exterior edge (9) with a length substantially corresponding to the width of the flanges (1') of the plates (1).
A heat exchanger according to any of the preceding claims, wherein the base of the first type slits (6) and the base of the second type slits (7) at the most distant point from the exterior edge (9) are provided with a rounded finish, such as a semi-circular shaped bottom of the slits (6, 7).
A heat exchanger according to any of the preceding claims, wherein at least the first type of slits (6) are provided with chamfered transitional edges or rounded edges as receiving portions defining the entry into the narrow passage sections (6').
A heat exchanger according to any of the preceding claims, wherein the comb-like shaped plate holding frame members (5) are made of steel, preferably stainless steel, and more preferably austenitic stainless steel.
A heat exchanger according to any of the preceding claims, wherein the comb-like shaped plate holding frame members (5) are provided with a mounting portion, preferably in the form of a longitudinal inverted V-shaped, in the portion opposite the exterior edge.
A heat exchanger according to any of the preceding claims, wherein the plates (1) are rectangular with two side flanges and a top and a bottom flange, and wherein a plurality of plate holding frame members (5) are arranged in the frame for receiving and retaining the plates at each of the side flanges and at the bottom and top flanges of said plates.
A heat exchanger according to any of the preceding claims, wherein the plates (1), the manifolds and the frame (2) and the plate mounting are all made of stainless steel, and more preferably austenitic stainless steel.
A heat exchanger according to any of the preceding claims, wherein the frame (2) is generally cubical with an open front rectangular side and an opposite open rear rectangular side and four rectangular sides therebetween.