Heat exchanger with integrated double-acting flow reversing valve

Abstract

A heat exchanger (20 ') with an integrated double-acting backwash valve is provided. A valve arrangement (50 ') is located in the heat exchanger body (22') or in at least one of a second port (32 ') and a third port (33') on the heat exchanger body and is configured to passively switch between a first operating mode and a second operating mode. The valve arrangement comprises a closed first valve (51 ') located at or near a third port in the heat exchanger body to close the third port in the first mode of operation during normal use such that fluid flows in a positive direction through the main fluid circulation path. The valve arrangement further comprises a second valve (61 ') which opens in the first operating mode. A functional connection is provided between the valves that extends through a portion of the heat exchanger such that closing the first valve opens the second valve, and vice versa. In a second mode of operation, the force of the supplemental fluid acting on the first valve from the third port opens the first valve while closing the second valve such that the supplemental fluid is adapted to circulate through the first flow passage of the primary fluid circulation path in a negative flow direction from the third port to the first port. This backflushes the first flow channel of the main fluid circulation path.

Description

Technical Field

[0001] The present invention relates to heat exchangers. More particularly, the present invention relates to heat exchangers having improved fouling resistance. Background Art

[0002] Plate heat exchangers are widely used in industry to efficiently transfer heat from one fluid stream to another without the two fluid streams mixing. Various designs of plate heat exchangers are known, including so-called "gasketed" plates or "brazed" plates. Plate heat exchangers are available from many manufacturers in a variety of sizes and capacities and can be designed for use with liquids, gases, or vapors. Plate heat exchangers are commonly used in agricultural / food processing, biochemical and pharmaceutical industries, commercial and industrial process industries, heating, ventilation, and air conditioning (HVAC) applications, manufacturing, and for institutional and residential equipment such as domestic water heaters, heat pumps, etc.

[0003] Virtually all plate heat exchangers 10 are formed by a series of metal plates 12, 13 which are assembled in such a way that adjacent, preferably alternately connected, flow channels 14, 15 are formed for each series, each flow channel allowing a fluid to circulate. The flow channels 14, 15 and the flow distribution passages are arranged such that adjacent flow channels 14, 15 circulate one of the two fluids (see FIG. 1), thus allowing heat to be transferred from one stream to the other through the separating metal plates 12, 13, while the two separate fluid streams do not mix with each other. These two fluid streams can be considered as "primary" and "secondary" fluid circulation paths. To increase the "effectiveness" of the plate heat exchanger, it is standard practice to pattern the metal separating plates 12, 13, as shown in FIG. 2, to increase the heat transfer surface area and the local flow velocity and to ensure uniform fluid distribution. To further increase the capacity and efficiency, the size and number of plates 12, 13 and the associated flow channels 14, 15 can be increased to accommodate a larger load or to achieve certain performance characteristics such as size or pressure drop (i.e., flow resistance). Most commonly, heat exchange occurs between two fluid streams originating from two different flow circulation systems. Although it is possible that both the primary and secondary fluids can be the same, this is not typical nor necessary. For example, the primary fluid can be a refrigerant vapor and the secondary fluid can be a liquid (e.g., water), or vice versa.

[0004] Heat exchangers are typically equipped with at least two inlet ports 16, 17 and two outlet ports 18, 19 to allow the entry and exit of fluid streams, as shown, for example, in FIGS. 1 and 2. These ports 16 - 19 are typically equipped with various types of "pipe" fittings (e.g., threaded or brazed pipe joints, etc.) to allow the connection of the flow circulation loop to the heat exchanger.

[0005] Because plate heat exchangers are typically designed to be compact and efficient, the spacing between adjacent plates is small, resulting in small flow passages. In some cases, due to the accumulation of particulate, chemical, biological, or corrosion deposits, the heat exchanger is prone to fouling and / or scaling in the flow passages. These deposits can have a very adverse effect on performance due to the reduction in the flow area of the channels, the increase in pressure drop, and the increase in the thermal resistance between adjacent fluid flows. In extreme cases, the fluid flowing through one or two flow circuits may be significantly reduced, leading to failure of the component and potentially any associated equipment and process.

[0006] In many cases, fouling may be accelerated in heat exchangers that circulate a fluid containing dissolved minerals or salts that deposit on the heat transfer surface. In such cases, manufacturers recommend routine cleaning or flushing of the heat exchanger with a cleaning solution to redissolve the mineral deposits, or recommend "backwashing" the heat exchanger to flush out accumulated particulate or biological matter.

[0007] Fouling of heat exchangers that circulate water obtained from municipal, groundwater, wells, lakes, and reservoirs is a particular problem if the water is considered "hard" (i.e., contains dissolved minerals), which over time deposits on the heat transfer surfaces in the heat exchanger.

[0008] The inventors have previously developed backwash valve assemblies that can be used in combination with various thermal fluid handling components, including heat exchangers, as shown, for example, in U.S. 7,823,628, U.S. 7,171,972, and U.S. 6,827,091. These have proven successful in passively backwashing heat exchangers to remove and / or reduce fouling.

[0009] However, improvements are needed in both function and application. SUMMARY OF THE INVENTION

[0010] In one aspect, the present disclosure is directed to a heat exchanger including a heat exchanger body having a series of adjacent first flow channels and second flow channels. The first flow channels are isolated from the second flow channels, and the first flow channels define a main fluid circulation path having an inlet side and an outlet side. A first port, a second port, and a third port are provided on the heat exchanger body and are in fluid communication with the main fluid circulation path. The first port is located on the inlet side of the main fluid circulation path and is adapted to serve as an inlet for the fluid to be heated during normal use, and the second and third ports are located on the outlet side of the main fluid circulation path. The second port is adapted to serve as an outlet for the heated fluid from the main fluid circulation path of the heat exchanger, and the third port is adapted to receive a supplementary fluid, which may be the same or different from the fluid in the main fluid circulation path. In a preferred arrangement, the first port is preferably located below the second and third ports in the use position, especially for convective water heater applications. However, this is not required for all applications. Valve means are located in at least one of the heat exchanger body or the second and third ports, and the valve means are configured to passively switch (i.e., without an external actuator) between a first and a second operating mode. The valve means includes a first valve body biased by an elastic element to a closed position against a first valve seat, the first valve seat being located at or near the third port in the heat exchanger body so as to close the third port in the first operating mode during normal use. The valve means further includes a second valve body acting against a second valve seat, the second valve seat being located at or near the second port in the heat exchanger body, and in the first operating mode, the second valve body is in an open position spaced apart from the second valve seat such that the fluid heated in the heat exchanger body is adapted to circulate through the main fluid circulation path (i.e., the second side of the heat exchanger) in the positive flow direction from the first port to the second port. A functional connection is provided between the second valve body and the first valve body, the functional connection extending through a part of the heat exchanger body such that movement of the first valve body to the closed position moves the second valve body to the open position, and movement of the first valve body to the open position moves the second valve body to the closed position. In the second operating mode, when the force of the supplementary fluid acting on the first valve body from the third port overcomes the closing force of the elastic element and any pressure of the fluid in the main fluid circulation path, the first valve body is movable to the open position while moving the second valve body to the closed position against the second valve seat, such that the supplementary fluid (e.g., tap water) is adapted to circulate through the first flow channel of the main fluid circulation path in the negative flow direction from the third port to the first port. This backwashes the first flow channel of the main fluid circulation path to remove scale and redissolves some mineral deposits with a reverse cold water flow from the tap water.

[0011] Preferably, when the elastic force and any pressure in the main fluid path overcome the pressure of the supplementary fluid at the third port, the valve device is configured to return to the first operating mode, thereby re - establishing a flow path for the main fluid in the positive flow direction. This allows for fully passive operation of the valve device for back - flushing or flow reversal based on the demand for the heated fluid pumped from the main fluid path, resulting in a pressure drop that allows the valve device to move to the second operating position.

[0012] In a preferred arrangement, the elastic element is a spring, preferably a metal helical spring. However, it can also be an elastic element based on pneumatic or magnetic forces.

[0013] In a preferred arrangement, the functional connection is a mechanical linkage. However, it can also be a magnetic coupling, a hydraulic or pneumatic connection, or any other suitable arrangement.

[0014] In a preferred embodiment, the second port and the third port are axially aligned, and the functional connection is an axially extending shaft. This allows for easier manufacturing with only minimal changes from an existing heat exchanger assembly in order to incorporate the valve device for passive back - flushing.

[0015] In one embodiment, the first valve seat is integrally formed in the third port.

[0016] In one embodiment, the second valve seat is integrally formed in the second port.

[0017] In one embodiment, one of the first or second valve seats is integrally formed in the corresponding one of the third or second ports, and the other of the first or second valve seats is formed as a separate component inserted into the corresponding other of the third or second ports.

[0018] In one embodiment, the first and second valve seats are respectively inserted into the third and second ports.

[0019] In one embodiment, the first valve seat is located in the first valve housing, the first valve housing is inserted into the third port, and the elastic element is located in the first valve housing. However, the elastic element can be located anywhere as long as it is functionally capable of biasing the first valve body towards the first valve seat.

[0020] Preferably, the first seal is located between the first valve housing and the inner wall of the third port or the heat exchanger body. In one embodiment, the second valve seat is located in the second valve housing, and the second valve housing is inserted into the second port.

[0021] Preferably, the second seal is located between the inner wall of the heat exchanger body or the second port.

[0022] In one embodiment, the elastic element support is located in the heat exchanger body, and the elastic element is arranged between the elastic element support and the first valve body.

[0023] In a preferred configuration, the heat exchanger body includes a series of metal plates that are assembled to form the series of adjacent first flow channels and second flow channels.

[0024] In another aspect, a method of passively backwashing a heat exchanger is provided, which includes the following steps:

[0025] Providing a heat exchanger having: a heat exchanger body having a series of adjacent first flow channels and second flow channels, the first flow channels being isolated from the second flow channels, the first flow channels defining a main fluid circulation path having an inlet side and an outlet side; a first port, a second port, and a third port, the first port, the second port, and the third port being provided on the heat exchanger body and in fluid communication with the main fluid circulation path, the first port being located on the inlet side of the main fluid circulation path, and the second port and the third port being located on the outlet side of the main fluid circulation path, in a typical use position, the first port being upstream of (and preferably below) the second port and the third port; valve means located in at least one of the heat exchanger body or the second and third ports, the valve means being configured to passively switch between a first and a second operating mode, the valve means including: a first valve having a first valve body biased by an elastic element to a closed position against a first valve seat, the first valve seat being located at or near the third port in the heat exchanger body so as to close the third port in the first operating mode during normal use; a second valve having a valve body acting against a second valve seat, the second valve seat being located at or near the second port in the heat exchanger body, and in the first operating mode, the second valve body being in an open position spaced apart from the second valve seat; and a functional connection between the second valve body and the first valve body extending through a portion of the heat exchanger body such that movement of the first valve body to the closed position moves the second valve body to the open position, and movement of the first valve body to the open position moves the second valve body to the closed position;

[0026] Connecting the third port to a pressurized fluid water supply, which can be tap water in a water heater application;

[0027] Connecting the first port to the bottom connection of a hot fluid storage container;

[0028] Connecting the second port to the top connection of a hot fluid storage tank;

[0029] In a first operating mode, the second valve body is held in an open position spaced apart from the second valve seat, and when the fluid entering the first port is heated, a positive flow direction is provided for the fluid from the first port through the main fluid path of the heat exchanger body to the second port by convection and / or forced pump circulation; and

[0030] In a second operating mode, when the pressure of the make-up fluid (e.g., tap water in a water heater application) at the third port overcomes the closing force of the elastic element and any pressure of the water in the main fluid path, the first valve body is moved to the open position while the second valve body is moved to the closed position against the second valve seat, so that the first valve opens and provides a flow of make-up fluid from the make-up fluid supply source in the negative flow direction through the main fluid circulation path from the third port to the first port, thereby backwashing the heat exchanger.

[0031] The method may optionally further include integrally forming at least one of the first or second valve seats in a corresponding third or second port or a part of the heat exchanger body.

[0032] The method may optionally further include providing the second port and the third port axially aligned with each other.

[0033] The method may optionally further include forming the functional connection as a mechanical linkage.

[0034] Preferably, the method includes providing the heat exchanger assembly as a pre-assembled unit.

[0035] The features mentioned above can be used alone or in various combinations. Description of the Drawings

[0036] Further advantages and features of the present invention will become apparent from the following description of embodiments with reference to the drawings, in which:

[0037] Figure 1 is a perspective view of a known plate heat exchanger.

[0038] Figure 2 is an exploded view of the plate heat exchanger of Figure 1.

[0039] Figure 3 is a schematic view of a heat exchanger with an integrated dual-action backwash valve device according to an embodiment of the present invention, shown connected to a tank in a water heating device in a first operating mode, wherein the main fluid flows through the heat exchanger in a positive flow direction.

[0040] Figure 4 is shown in a second operating mode Figure 3 A schematic view of the heat exchanger with an integrated dual-action backwash valve shown, wherein the main fluid flows through the heat exchanger in a negative flow direction.

[0041] Figure 5 is a cross-sectional view of a plate heat exchanger with an integrated dual-action backwash valve device according to an embodiment of the present invention shown in a first operating mode, wherein the main fluid flows through the heat exchanger in the positive flow direction.

[0042] Figure 6 is shown in a second operating mode Figure 5 a cross-sectional view of the plate heat exchanger with an integrated dual-action backwash valve shown, wherein the main fluid flows through the heat exchanger in the negative flow direction.

[0043] Figure 7 is shown in a first operating mode Figure 5 an exploded perspective view of the plate heat exchanger with an integrated dual-action backwash valve device therein, wherein the main fluid flows through the heat exchanger in the positive flow direction.

[0044] Figure 8 is shown in a second operating mode Figure 7 an exploded perspective view of the plate heat exchanger with an integrated dual-action backwash valve shown, wherein the main fluid flows through the heat exchanger in the negative flow direction.

[0045] Figure 9 is a cross-sectional view of an embodiment of a dual-action backwash valve that can be integrated into a plate heat exchanger.

[0046] Figure 10 is along Figure 9 a cross-sectional view taken along line A-A in DETAILED DESCRIPTION

[0047] In the following description, certain terms are used for convenience only and are not restrictive. The words "right", "left", "top" and "bottom" denote directions in the accompanying drawings being referred to. Unless otherwise specifically stated, the words "a" and "an" as used in the corresponding parts of the claims and the specification are defined to include one or more of the recited items. The term includes the specifically mentioned words above, their derivatives and words of similar meaning. The phrase "at least one" followed by a list of two or more items, such as "A, B or C", means any single one of A, B or C and any combination thereof. Unless otherwise stated, the term about or approximately means within + / - 10% of the specified value and within + / - 25° of the specified angle or direction.

[0048] Reference Figure 3-8, shows heat exchangers 20, 20' including integrated flow valve devices 50, 50', which automatically convey a similar or different fluid (i.e., "make-up" fluid) in a flow direction opposite to the normal or "positive" flow direction to the main fluid circulation path on the second side of the heat exchangers 20, 20'.

[0049] In Figure 3 and Figure 4 the heat exchanger 20 is schematically shown, and in Figure 3 it is shown as part of a water heating device, where the main fluid circulation path 30 with an optional circulation pump 37 shown in Figure 3 is connected to a hot water storage tank 38, and the secondary fluid circulation path 36 is connected to a heat source (not shown).

[0050] The heat exchanger 20 includes a heat exchanger body 22 having a series of adjacent first flow channels 26 and second flow channels 27. The first flow channels 26 are isolated from the second flow channels 27, and the first flow channels 26 define a main fluid circulation path 30 having an inlet side 30a and an outlet side 30b. A first port 31, a second port 32, and a third port 33 are provided on the heat exchanger body 22 and are in fluid communication with the main fluid circulation path 26. The first port 31 is located on the inlet side 30a of the main fluid circulation path 30 and is adapted to be the inlet of the fluid to be heated during normal use, which in this exemplary embodiment is drawn from the bottom of the hot water storage tank 38. The second port 32 and the third port 33 are located at the outlet side 30b of the main fluid circulation path 30. The second port 32 is adapted to be the outlet of the heated fluid of the main fluid circulation path 30 from the heat exchanger body 22 after it has been heated by heat transfer from the fluid in the secondary fluid circulation path 36. The third port 33 is adapted to receive a make-up fluid, such as tap water, when a hot water user draws hot water from the top of the hot water storage tank 38 through an outlet 39. A fourth port 34 and a fifth port 35 are provided for circulating the secondary fluid through the second flow channels 27.

[0051] The valve device 50 is located in the heat exchanger body 22 and / or in the second port 32 and the third port 33, and is configured to passively switch between a first and a second operating mode. The valve device 50 includes a first valve 51 that closes the third port 33 in the first operating mode during normal use. The valve device 50 further includes a second valve 61 located at or near the second port 32 in the heat exchanger body 22, and in the first operating mode, the second valve is open so that the fluid heated in the heat exchanger body 22 is adapted to circulate from the first port 31 through the main fluid circulation path 30 in the positive flow direction D1 to the second port 32. A functional connection 70 is provided between the second valve 61 and the first valve 51, which extends through a part of the heat exchanger body 22 such that movement of the first valve 51 to the closed position moves the second valve 61 to the open position, and movement of the first valve 51 to the open position moves the second valve 61 to the closed position.

[0052] In the second operating mode, when the force F1 of the supplementary fluid acting on the first valve 51 from the third port 33 (see for example Figure 5 and 6 ) overcomes the closing force F of the elastic element (such as shown as 54’ in Figure 5 and 6 , but not specifically combined with the embodiments in Figure 3 and 4 ) and any pressure F2 of the fluid in the main fluid circulation path 30 (see s and Figure 5 and 6 ), for example when hot water is drawn from the hot water storage tank 38 via the outlet 39, the first valve 51 can move to the open position while moving the second valve 61 to the closed position so that the supplementary fluid is adapted to circulate from the third port 33 through the first flow channel 26 of the main fluid circulation path 30 in the negative flow direction D2 to the first port 31, as Figure 4 shown. This backwashes the first flow channel 26 of the main fluid circulation path 30 to remove scale and redissolves some mineral deposits with a reverse cold water flow from the pressurized fluid source for the supplementary fluid. When the closing force Fs + pressure F2 of the fluid in the main fluid circulation path 30 exceeds the force F1 of the supplementary fluid, for example when the hot water drawn from the tank 38 stops, the first valve 51 closes again while opening the second valve 61 via the functional connection 70.

[0053] Therefore, when a positive pressure difference is applied to the first valve 51, due to the consumption of the fluid in the secondary circuit or the increase in the pressure of the supplementary supply liquid, the integrated flow valve device 50 is automatically actuated.

[0054] In a preferred arrangement, the first port 31 is preferably located below the second port 32 and the third port 33 in the use position, particularly for convective water heater applications, such that no separate pump is required to cause a fluid flow in the main fluid circulation path 30 in the positive flow direction D1. However, this is not required for all applications.

[0055] Reference is now made to Figure 5-8 , which shows a particularly preferred arrangement of the heat exchanger 20'. The heat exchanger 20' is similar to the heat exchanger 20 and operates in the same manner. Here, the heat exchanger body 22' is formed by alternating first plates 24' and second plates 25', as most clearly shown in Figure 7 and 8 , which define a series of adjacent first flow channels 26' and second flow channels 27'. The first flow channels 26' define a main fluid circulation path 30' having an inlet side 30a' and an outlet side 30b'. A first port 31', a second port 32' and a third port 33' are provided on the heat exchanger body 22' and are in fluid communication with the main fluid circulation path 26'. The first port 31' is located on the inlet side 30a' of the main fluid circulation path 30' and is adapted to be the inlet of the fluid to be heated during normal use. The second port 32' and the third port 33' are located at the outlet side 30b' of the main fluid circulation path 30'. The second port 32' is adapted to be the outlet of the heated fluid of the main fluid circulation path 30' from the heat exchanger body 22' after it has been heated by heat transfer from the fluid in the secondary fluid circulation path 36'. The third port 33' is adapted to receive a make-up fluid, for example, if the heat exchanger is used as part of a water heating device, the make-up fluid is tap water, but other applications are possible. As shown in Figure 7 and 8 , a fourth port 34' and a fifth port 35' are provided for circulating a second fluid through the second flow channels 27'.

[0056] The valve device 50' is located in at least one of the heat exchanger body 22' or the second port 32' and the third port 33', and is configured to passively switch between a first and a second operating mode. The valve device 50' herein includes a first valve 51', which preferably has a first valve body 52' biased by an elastic element 54' to a closed position against a first valve seat 56', which is located at or near the third port 33' in the heat exchanger body 22' so as to close the third port 33' in the first operating mode during normal use. The valve device 50' further includes a second valve 61', which preferably has a second valve body 62' acting against a second valve seat 66', which is located at or near the second port 32' in the heat exchanger body 22'. In the first operating mode, the second valve body 62' is in an open position spaced apart from the second valve seat 66' such that the fluid heated in the heat exchanger body 22' is adapted to circulate from the first port 31' through the main fluid circulation path 30' in the positive flow direction D1 to the second port 32'. A functional connection 70', preferably in the form of a mechanical linkage 72', a magnetic coupling, or a hydraulic or pneumatic connection, is provided between the second valve body 62' and the first valve body 52' and extends through a part of the heat exchanger body 22' such that movement of the first valve body 52' to the closed position moves the second valve body 62' to the open position, and movement of the first valve body 52' to the open position moves the second valve body 62' to the closed position. In Figure 9 and 10 details of an exemplary embodiment of the valve device 50' are shown.

[0057] In the second operating mode, as Figure 6 shown, when the force F1 of the supplementary fluid acting on the first valve body 52' from the third port 33' overcomes the closing force Fs of the elastic element 54' (shown herein in the form of a helical spring) and any pressure F2 of the fluid in the main fluid circulation path 30', the first valve body 52' can move to the open position while moving the second valve body 62' to the closed position against the second valve seat 66' such that the supplementary fluid is adapted to circulate from the third port 33' through the first flow channel 26' of the main fluid circulation path 30' in the negative flow direction D2 to the first port 31'. This backwashes the first flow channel 26' of the main fluid circulation path 30' to remove scale and redissolves some mineral deposits with the reverse cold water flow from the tap water.

[0058] When the elastic force Fs and any pressure F2 in the main fluid path overcome the force F1 of the supplementary fluid acting on the first valve body 52 at the third port, the valve device 50' is configured to return to the first operating mode, thereby closing the first valve body 52' against the first valve seat 56' while opening the second valve 61'. This allows the valve device 50' to operate completely passively for backwashing based on the demand for the heated fluid pumped from a downstream position on the hot side connected to the main fluid path 30', resulting in a pressure drop that allows the valve device 50' to move to the second operating mode.

[0059] In a preferred arrangement, the elastic element is a spring 54', and preferably a metal helical spring. However, it can also be an elastic element based on pneumatic or magnetic forces.

[0060] In a preferred arrangement, the functional connection 70' is a mechanical link or shaft. However, it can also be a magnetic coupling, a hydraulic or pneumatic connection, or any other suitable arrangement.

[0061] In a particularly preferred arrangement, the second port 32' and the third port 33' are axially aligned, and the functional connection 70' is an axially extending link or shaft 72'. This allows for easier manufacturing with minimal changes to an existing heat exchanger assembly, such as the one described above at 10, in order to incorporate the valve device 50' for passive backwashing.

[0062] The first valve seat 52' can be integrally formed in the third port 33'. Alternatively, the first valve seat 52' can be located in the first valve housing 53', such as Figure 9 and 10 shown, where the first valve housing is inserted into the third port 33', and the elastic element 54' is preferably also located in the first valve housing 53'. In this case, preferably, the first seal 58' is located between the first valve housing 53' and the inner wall 33a' of the third port 33' or the heat exchanger body 22' (shown in Figure 5 . The spring support 57' for the spring is preferably then also formed in the first valve housing 53'. In addition, the support 59' for the link or shaft 72' can be formed as part of the housing 53'.

[0063] The second valve seat 62' can also be integrally formed in the second port 32'. Alternatively, the second valve seat 62' can be located in the second valve housing 63', such as Figure 9 and 10 shown, where the second valve housing is inserted into the second port 32'. In this case, preferably, the second seal 68' is located between the second valve housing 63' and the inner wall 32a' of the second port 32' or the heat exchanger body 22' (shown in Figure 5between the ones shown in [the figure]. Additionally, the support 99' for the connecting rod or shaft 72' can be formed as part of the housing 63'.

[0064] In one embodiment, one of the first valve seat 56' or the second valve seat 66' is integrally formed in the corresponding one of the third port 33' or the second port 32', and the other of the first valve seat 56' or the second valve seat 66' is formed as a separate component, such as the first valve housing 53' or the second valve housing 63', which is inserted into the corresponding other one of the third port 33' or the second port 32'.

[0065] In one embodiment, both the first valve seat 56' and the second valve seat 66' are respectively inserted into the third port 33' and the second port 32', preferably by inserting the first valve housing 53' and the second valve housing 63'.

[0066] In one embodiment, the elastic element support 57' is located in the heat exchanger body 22', and the elastic element 54' is arranged between the elastic element support 57' and the first valve body 52'. Here, the elastic element support 57' can be formed in the first valve housing 53' or a part thereof. Alternatively, it can be formed separately in the heat exchanger body 22'.

[0067] Although the heat exchanger body 22' in this embodiment includes a series of metal plates 24, 25 which are assembled to form a series of adjacent first flow channels 26' and second flow channels 27', the heat exchanger body 22' can be formed in other ways, for example, as a series of parallel tubes, or a tube-in-tube heat exchanger arrangement.

[0068] On the other hand, a method for passively backwashing the heat exchangers 20, 20' is provided, which includes the following steps:

[0069] Provide the heat exchangers 20, 20' as described above;

[0070] Connect the third port 33, 33' to a tap water supply source;

[0071] Connect the first port 31, 31' to the bottom connection of the hot water storage container 38;

[0072] Connect the second port 32 to the top connection of the hot water storage tank 38;

[0073] In a first operating mode, the second valves 61, 61' are held in the open position (while the first valves 51, 51' are closed), where preferably the second valve body 62' is spaced apart from the second valve seat 66'. When the water entering the first ports 31, 31' is heated, a positive flow direction D1 of the water from the first ports 31, 31' through the main fluid paths 30, 30' of the heat exchanger bodies 22, 22' to the second ports 32, 32' is provided by convection; and

[0074] In a second operating mode, when the pressure F1 of the water from the tap water supply source at the third ports 33, 33' overcomes the closing force Fs of the elastic element and any pressure F2 of the water in the main fluid paths 26, 26', the first valves 51, 51' are opened. Preferably, the first valve body 52' is moved to the open position while the second valves 61, 61' are closed. Preferably, the second valve body 62' is moved to the closed position against the second valve seat 66', so that the first valves 51, 51' are opened, and a water flow from the tap water supply source in the negative flow direction D2 through the main fluid circulation paths 26, 26' from the third ports 33, 33' to the first ports 31, 31' is provided to backwash the heat exchangers 20, 20'.

[0075] The method may optionally further include integrally forming at least one of the first valve seat 56' or the second valve seat 66' in a corresponding one of the third ports 33' or the second ports 32' or a part of the heat exchanger body 22'.

[0076] The method may optionally further include providing second ports and third ports 32, 33, 32', 33' that are axially aligned with each other.

[0077] The method may optionally further include forming the functional connection portions 70, 70' as a mechanical link 72'. Alternatively, the functional connection portions 70, 70' may be formed by other types of connection portions as described above.

[0078] Preferably, the method includes providing the heat exchangers 20, 20' as pre-assembled units, where the valve devices 50, 50' are integrally formed in the pre-assembled units.

[0079] In accordance with the present disclosure, a compact design is achieved that does not require additional external piping or conduits to connect an external valve assembly to the heat exchangers 20, 20'. The integrated dual-acting backwash valve devices 50, 50' can be configured for different heat exchanger sizes and capacities or applications (e.g., high-temperature or corrosive environments, etc.), including cases where the size or number of plates is increased or decreased for a particular application. Additionally, the configuration and installation of the dual-acting backwash valve devices 50, 50' can be carried out during the manufacture of the heat exchangers to ensure proper operation and fit. Factory installation also allows the valve devices 50, 50' to be integrated into the heat exchanger bodies 22, 22' at a lower cost.

[0080] A further benefit of this arrangement is that the integrated valve devices 50, 50' will operate in any orientation that may be required for the proper placement of the heat exchangers 20, 20' for a particular application and do not rely on weak gravity to return to a "normal" operating mode.

[0081] Finally, by specifying different holding force levels and characteristics (e.g., spring force, length, displacement, and "spring constant"), the rate and magnitude of opening or closing of the valve devices 50, 50' can be specified by varying the hydraulic and holding force characteristics to facilitate the desired operation.

[0082] It should be understood that the foregoing is presented by way of illustration only and not in any limiting sense. It is contemplated that various alternatives and modifications can be made to the described embodiments without departing from the spirit and scope of the invention. Having thus described the invention in such detail, it should be understood and will be apparent to those skilled in the art that numerous physical changes can be made without altering the inventive concepts and principles embodied therein, only a few of which are illustrated in the detailed description of the invention. It should also be understood that many embodiments that include only a portion of the preferred embodiments are possible, and these embodiments do not change the inventive concepts and principles embodied therein for those portions. Accordingly, the present embodiments and alternative configurations are considered to be exemplary and / or illustrative in all respects and not restrictive, and the scope of the invention is indicated by the pending claims rather than the foregoing description, and accordingly all alternative embodiments and changes to this embodiment within the meaning and scope of the equivalents of the said claims are included therein.

Claims

1. A heat exchanger, comprising: a heat exchanger body having a series of adjacent first and second flow channels, the first flow channels being isolated from the second flow channels, the first flow channels defining a main fluid circulation path having an inlet side and an outlet side; first, second and third ports provided on the heat exchanger body and in fluid communication with the main fluid circulation path, the first port being located at the inlet side of the main fluid circulation path and adapted to serve as an inlet for the fluid to be heated during normal use, and the second and third ports being located at the outlet side of the main fluid circulation path, the second port being adapted to serve as an outlet for the heated fluid from the main fluid circulation path of the heat exchanger body, and the third port being adapted to receive a supplementary fluid; valve means located in at least one of the heat exchanger body or the second and third ports, the valve means being configured to switch passively between a first and a second operating mode, the valve means comprising: a first valve body biased by an elastic element to a closed position against a first valve seat, the first valve seat being located at or near the third port in the heat exchanger body so as to close the third port in the first operating mode during normal use; a second valve body acting against a second valve seat, the second valve seat being located at or near the second port in the heat exchanger body, and in the first operating mode, the second valve body being in an open position spaced from the second valve seat such that the fluid heated in the heat exchanger body is adapted to circulate through the main fluid circulation path in a positive flow direction from the first port to the second port; a functional connection between the second valve body and the first valve body extending through a portion of the heat exchanger body such that movement of the first valve body to the closed position moves the second valve body to the open position, and movement of the first valve body to the open position moves the second valve body to the closed position; and in the second operating mode, when the force of the supplementary fluid acting on the first valve body from the third port overcomes the closing force of the elastic element and any pressure of the fluid in the main fluid circulation path, the first valve body is capable of moving to the open position while moving the second valve body to the closed position against the second valve seat such that the supplementary fluid is adapted to circulate through the first flow channel of the main fluid circulation path in a negative flow direction from the third port to the first port.

2. The heat exchanger according to claim 1, wherein the valve means is configured to return to the first operating mode when the elastic force and any pressure in the main fluid path overcome the force of the supplementary fluid at the third port.

3. The heat exchanger according to claim 1, wherein the elastic element is a spring.

4. The heat exchanger according to claim 1, wherein The functional connection part is a mechanical connection part, a magnetic coupling part, or a hydraulic or pneumatic connection part.

5. The heat exchanger according to claim 1, wherein, the second port and the third port are axially aligned, and the functional connection part is an axially extending shaft.

6. The heat exchanger according to claim 1, wherein, the first valve seat is integrally formed in the third port.

7. The heat exchanger according to claim 1, wherein, the second valve seat is integrally formed in the second port.

8. The heat exchanger according to claim 1, wherein, one of the first or second valve seats is integrally formed in the corresponding one of the third or second ports, and the other of the first or second valve seats is formed as a separate component inserted into the corresponding other one of the third or second ports.

9. The heat exchanger according to claim 1, wherein, the first and second valve seats are respectively inserted into the third and second ports.

10. The heat exchanger according to claim 1, wherein, the first valve seat is located in a first valve housing inserted into the third port, and the elastic element is located in at least one of the first valve housing or the second valve housing.

11. The heat exchanger according to claim 10, further comprising a first seal between the first valve housing and the inner wall of the third port or the heat exchanger body.

12. The heat exchanger according to claim 1, wherein, the second valve seat is located in a second valve housing, and the second valve housing is inserted into the second port.

13. The heat exchanger according to claim 12, further comprising a second seal between the inner wall of the second port or the heat exchanger body.

14. The heat exchanger according to claim 1, further comprising an elastic element support in the heat exchanger body, and the elastic element is arranged between the elastic element support and the first valve body.

15. The heat exchanger according to claim 1, wherein, the heat exchanger body includes a series of metal plates, and the series of metal plates are assembled to form the series of adjacent first flow channels and second flow channels.

16. The heat exchanger according to claim 1, wherein, in the use position, the first port is located below the second port and the third port.

17. The heat exchanger according to claim 1, further comprising a circulation pump in the main fluid circulation path.

18. A method for passively backwashing a heat exchanger, the method comprising: providing a heat exchanger having: a heat exchanger body having a series of adjacent first flow channels and second flow channels, the first flow channels being isolated from the second flow channels, the first flow channels defining a main fluid circulation path having an inlet side and an outlet side; First, second, and third ports, the first, second, and third ports being provided on the heat exchanger body and in fluid communication with the main fluid circulation path, the first port being located on the inlet side of the main fluid circulation path, and the second and third ports being located on the outlet side of the main fluid circulation path, and in the use position, the first port being upstream of the second port and the third port; Valve means located in at least one of the heat exchanger body or the second and third ports, the valve means being configured to passively switch between a first and a second operating mode, the valve means comprising: a first valve having a first valve body biased by an elastic element to a closed position against a first valve seat, the first valve seat being located at or near the third port in the heat exchanger body so as to close the third port in the first operating mode during normal use; a second valve having a valve body acting against a second valve seat, the second valve seat being located at or near the second port in the heat exchanger body, and in the first operating mode, the second valve body being in an open position spaced from the second valve seat; and a functional connection between the second valve body and the first valve body, the functional connection extending through a portion of the heat exchanger body such that movement of the first valve body to the closed position moves the second valve body to the open position, and movement of the first valve body to the open position moves the second valve body to the closed position; Connecting the third port to a source of make-up fluid; Connecting the first port to the bottom connection of the hot fluid storage container; Connecting the second port to the top connection of the hot fluid storage tank; In the first operating mode, when the fluid entering the first port is heated, maintaining the second valve body in an open position spaced from the second valve seat to provide a positive flow direction for the fluid from the first port through the main fluid path of the heat exchanger body to the second port; and In the second operating mode, when the pressure of the make-up fluid at the third port overcomes the closing force of the elastic element and any pressure of the fluid in the main fluid path, moving the first valve body to the open position while moving the second valve body to the closed position against the second valve seat, such that the first valve opens and provides a flow of make-up fluid in a negative flow direction through the main fluid circulation path from the third port to the first port to thereby backwash the heat exchanger.

19. The method according to claim 18, further comprising integrally forming at least one of the first or second valve seats in the respective third or second port or a portion of the heat exchanger body.

20. The method according to claim 18, further comprising providing the second and third ports axially aligned with each other.

21. The method according to claim 18, further comprising forming the functional connection as a mechanical linkage.

22. The method according to claim 18, wherein the heat exchanger assembly is provided as a pre-assembled unit.

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