Water-water heat exchange device for waste heat recovery of low-grade hot wastewater

Abstract

The water-water heat exchange device comprises a shell and a water-water heat exchanger installed in the shell, a cold water inlet is formed in the position, located above the water-water heat exchanger, of the shell, and a cold water outlet is formed in the bottom of the shell; the water-water heat exchanger comprises at least one heat exchange module, and each heat exchange module comprises a water guide pipe, a heat exchange plate and a liquid guide rib; a first water channel for baffling back and forth is arranged in the heat exchange plate and is used for circulating low-grade hot wastewater; the liquid guide ribs are installed between the gaps of the two heat exchange plates to form a second water channel for baffling back and forth and used for circulating cold water, the low-grade hot wastewater flows from bottom to top in the first water channel, the cold water flows from top to bottom in the second water channel, and indirect heat exchange is conducted between the low-grade hot wastewater and the cold water through the wall faces of the heat exchange plates.

Description

Technical Field

[0001] The utility model relates to a heat exchanger, in particular to a water-water heat exchange device for recovering waste heat of low-grade hot wastewater. Background Art

[0002] Heat exchangers can be categorized as steam-water and water-water, depending on the type of heat exchange medium. A water-water heat exchanger involves indirect heat exchange between water, hot wastewater, and cold water. Existing steam-water heat exchangers are primarily used for waste heat recovery from high-temperature, high-pressure wastewater. These heat exchangers are primarily made of metal, requiring a large temperature difference between the hot and cold fluids during the heat exchange process. The heat medium within the heat exchanger operates at high pressure, and there are no cost-effective methods or measures for recovering waste heat from low-grade wastewater.

[0003] Low-grade thermal wastewater usually refers to industrial wastewater with a temperature below 60°C. For this type of wastewater, due to the low temperature of the wastewater and the small temperature difference between it and the low-temperature medium, there are generally problems such as low heat exchange efficiency and high recovery costs. Utility Model Content

[0004] The present application provides a water-water heat exchange device for recovering waste heat from low-grade hot wastewater, which has high heat exchange efficiency for low-grade hot wastewater with a temperature below 60°C and is easy to assemble.

[0005] A water-water heat exchange device for recovering waste heat from low-grade hot wastewater, comprising a housing and a water-water heat exchanger installed in the housing, a cold water inlet being provided on the housing and above the water-water heat exchanger, and a cold water outlet being provided at the bottom of the housing;

[0006] The water-water heat exchanger includes at least one heat exchange module, which includes two water pipes, a plurality of heat exchange plates, and liquid-conducting ribs. The heat exchange plates have a first water channel for back-and-forth water flow, and one of the corners of the heat exchange plates has a water inlet and a water outlet that pass through the heat exchange plates and communicate with the first water channel. The liquid-conducting ribs are arranged between adjacent heat exchange plates and are tightened and compressed by the heat exchange plates to form a second water channel for back-and-forth water flow between each two adjacent heat exchange plates. The two water pipes respectively penetrate the water inlet and outlet holes of the plurality of heat exchange plates and are then tightened to form the heat exchange module.

[0007] The water inlet of the second water channel is connected to the cold water inlet, and the water outlet is connected to the cold water outlet; the first water channel is used to circulate low-grade hot wastewater below 60°C, and the low-grade hot wastewater flows from bottom to top in the first water channel; the second water channel is used to circulate cold water, and the cold water flows from top to bottom in the second water channel.

[0008] In the heat exchanger of this application, low-grade hot wastewater flows through the heat exchange plates, while cold water flows through the gaps between the plates. The low-grade hot wastewater zigzags back and forth from bottom to top within the heat exchange plates, while the cold water zigzags back and forth from top to bottom within the gaps between the plates, creating countercurrent and crosscurrent flows. The heat exchanger of this application incorporates cold water flow channels within the gaps between the plates, enhancing the flow pattern of the cold water and improving heat exchange efficiency. This heat exchange device can recover waste heat from low-grade hot wastewater at temperatures between 30 and 60°C, saving energy and reducing consumption.

[0009] Several optional methods are also provided below, but they are not intended to be additional limitations on the above-mentioned overall solution. They are merely further supplements or optimizations. Under the premise that there are no technical or logical contradictions, each optional method can be combined separately for the above-mentioned overall solution, or multiple optional methods can be combined.

[0010] Optionally, the heat exchange plate includes:

[0011] A heat exchange diaphragm having a plurality of first flow channels arranged in parallel therein, wherein the water inlet and the water outlet are respectively located at a pair of corners of the heat exchange diaphragm, the first flow channels penetrate the heat exchange diaphragm in a direction parallel to the heat exchange diaphragm, and the water inlet and the water outlet penetrate the heat exchange diaphragm in a direction perpendicular to the heat exchange diaphragm;

[0012] The two water guide boxes are respectively located on both sides of the heat exchange diaphragm in the vertical direction and are sealed and connected to the heat exchange diaphragm as a whole. The water guide boxes are vertically divided into a number of independent second flow channels. The second flow channels are correspondingly connected to the first flow channels to form the first water channels in the heat exchange plate.

[0013] Optionally, each second flow channel corresponds to two adjacent first flow channels and the second flow channels in the two water guide boxes are staggered, the parts of the second flow channels on both sides that are staggered in height share one first flow channel, and the two adjacent first flow channels are connected in sequence through the corresponding second flow channels.

[0014] Optionally, the heat exchange diaphragm is a plastic diaphragm.

[0015] Optionally, the thickness of the heat exchange membrane is 5-7 mm; the thickness of the liquid-conducting ribs is 3-6 mm.

[0016] As a preferred plastic diaphragm, the heat exchange diaphragm is formed by melt-extruding polyester or polypropylene plastic and graphite, with the weight percentage of graphite in the heat exchange diaphragm being between 0.3% and 5%. The liquid-conducting ribs are made of rigid polyvinyl chloride. The addition of graphite increases the thermal conductivity of the diaphragm and improves the steam-water heat exchange efficiency.

[0017] Optionally, the extension direction of the liquid-conducting ribs is parallel to the extension direction of the first flow channel in the heat exchange plate.

[0018] Optionally, the liquid-conducting ribs include transverse ribs and longitudinal ribs. The longitudinal ribs are located adjacent to the two water guide boxes and extend in the same direction as the water guide boxes. The transverse ribs extend horizontally and are staggered vertically. One end of each transverse rib abuts the longitudinal rib on that side at intervals, and the other end is spaced apart from the longitudinal rib on the opposite side, leaving a water-passing opening. After adjacent heat exchange plates are butted and pressed together, the longitudinal ribs seal the vertical sides of the gaps between the heat exchange plates, and the transverse ribs divide the space enclosed by the longitudinal ribs into a second water channel that flows upward and downward, diverting water.

[0019] Optionally, the water pipe is a metal hollow circular tube with one end open and the other end closed, and the water outlet holes are evenly distributed on the wall of the water pipe.

[0020] Optionally, the heat exchange module further includes a plurality of seals, which are correspondingly sleeved on the water pipes between adjacent heat exchange plates and pressed by the heat exchange plates.

[0021] Optionally, the sealing member may be a sealing gasket.

[0022] Optionally, the sealing member may also adopt a sealing member having the following structure, including:

[0023] An annular sealing gasket is sleeved on the water pipe, and both end surfaces of the sealing gasket along the axial direction are provided with annular grooves;

[0024] The two sealing gaskets are made of soft annular polyester material and are respectively embedded in the corresponding grooves of the sealing gasket. They are used to seal the heat exchange diaphragm and the sealing gasket section during the fastening process of the heat exchange module.

[0025] The water-water heat exchange method for recovering waste heat from low-grade hot wastewater using the water-water heat exchange device includes:

[0026] Low-grade hot wastewater is fed into the first water channel inside each heat exchange plate of the water-water heat exchanger through the bottom water guide pipe of the water-water heat exchanger, and flows back and forth from bottom to top under the guidance of the flow channel of the first water channel; cold water is fed into the shell of the heat exchange device through the pipeline and enters the second water channel between adjacent diaphragms in the water-water heat exchanger under the action of gravity, and flows back and forth from top to bottom under the guidance of the liquid guide ribs; the low-grade hot wastewater and cold water form countercurrent and crosscurrent flows through the wall of the heat exchange plate, and carry out indirect water-water heat exchange; the heated cold water falls from the bottom of the water-water heat exchanger and is discharged from the bottom of the shell; the inlet temperature of the low-grade hot wastewater in the first water channel is less than 60℃.

[0027] Optionally, the flow ratio of the cold water to the low-grade hot wastewater is 0.7 to 1.1:1

[0028] Optionally, the cold water flow rate in the second water channel is 80 to 260 L / h.

[0029] Optionally, the operating pressure of the first circulation waterway is less than 0.08 MPa.

[0030] The present application also provides a water-water heat exchanger, comprising at least one heat exchange module, the heat exchange module comprising two water pipes, a plurality of heat exchange plates, and liquid-conducting ribs; a first water channel for back-and-forth water flow is provided within the heat exchange plate, and a pair of corners of the heat exchange plate are provided with a water inlet and a water outlet that pass through the heat exchange plate and communicate with the first water channel; the liquid-conducting ribs are arranged between adjacent heat exchange plates and are tightened and compressed by the heat exchange plates to form a second water channel for back-and-forth water flow between each two adjacent heat exchange plates; two water pipes respectively penetrate the water inlet and water outlet holes of the plurality of heat exchange plates and are tightened to form the heat exchange module;

[0031] The first water channel is used for circulating low-grade hot wastewater, and the low-grade hot wastewater flows in a zigzag manner from bottom to top in the first water channel; the second water channel is used for circulating cold water, and the cold water flows in a zigzag manner from top to bottom in the second water channel.

[0032] Other further limitations on the heat exchanger are the same as those on the heat exchange device and will not be repeated here.

[0033] The heat exchanger of the present application improves the flow channel structure, diaphragm material and diaphragm thickness of the heat exchanger for low-grade hot water. The improved heat exchanger significantly improves the heat exchange efficiency of hot and cold water and realizes efficient recovery of waste heat from low-temperature wastewater.

[0034] Compared with the prior art, this application has at least one of the following beneficial effects:

[0035] (1) The utility model provides a waste heat recovery system for low-grade hot industrial wastewater, which uses a plastic diaphragm as a heat-conducting carrier. The low-grade hot wastewater discharged by the industry flows through the heat exchange plate, and cold water flows through the gap between the heat exchange plates. By controlling the flow rate and gap between the hot and cold water, the heat exchange efficiency of the hot and cold water is improved, and the waste heat of the low-temperature wastewater is efficiently recovered;

[0036] (2) The utility model provides a heat exchanger for improving the efficient heat transfer of waste heat from low-grade wastewater. By modifying the heat conductivity of the heat exchange plate material and adding liquid-conducting ribs in the gap between the diaphragms to optimize the flow channel, the water-water thermal conductivity efficiency of the diaphragm is greatly increased, thereby improving the heat transfer performance of the heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic structural diagram of the water-water heat exchange device of this application;

[0038] Figure 2 This is a schematic diagram of the flow of cold water in the water-water heat exchange device of this application;

[0039] Figure 3 Schematic diagram of the top view of a heat exchange module of a water-water heat exchanger;

[0040] Figure 4 for Figure 3 An enlarged view of part A in the middle (for clarity, the fluid-conducting rib 24 is only shown in the partial enlarged view);

[0041] Figure 5 Schematic diagram of the split structure of a single heat exchange plate;

[0042] Figure 6 Schematic diagram of the fluid-conducting rib;

[0043] Figure 7 Schematic diagram of the flow direction of the first water channel inside a single heat exchange plate;

[0044] Figure 8 Schematic diagram of the coordination between the heat exchange plate and the liquid guiding ribs.

[0045] The reference numerals shown in the figures are as follows:

[0046] 1. Shell, 2. Water-water heat exchanger, 3. Water pump, 4. Control valve;

[0047] 2. Water-water heat exchanger: 21. heat exchange plate, 22. water guide pipe, 23. seal, 24. liquid guide ribs (24a. transverse ribs, 24b. longitudinal ribs, 24c. water opening);

[0048] 21. Heat exchange plate: 211. Heat exchange diaphragm, 212. Water guide box, 213. Water inlet, 214. Water outlet, 215. First flow channel, 216. Second flow channel. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0050] In order to better describe and illustrate the embodiments of the present application, reference may be made to one or more drawings, but the additional details or examples used to describe the drawings should not be considered as limiting the scope of the utility model invention of the present application, any of the currently described embodiments or preferred methods.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0052] See also Figure 1 and Figure 2 A water-water heat exchange device for recovering waste heat from low-grade wastewater comprises a housing 1 and a water-water heat exchanger 2 mounted within the housing. The housing has a cold water inlet located above the water-water heat exchanger, and a cold water outlet at the bottom of the housing. The wastewater outlet is connected to a water pump 4 via a pipeline, and a regulating valve 3 is provided on the connecting pipeline. The water-water heat exchanger is mounted in the middle of the housing and comprises at least one heat exchange module. The structure of the heat exchange module is described in detail in the following sections. Figures 3 to 8 , including several heat exchange plates 21, two water pipes 22, several sealing members 23 and several liquid-conducting ribs 24.

[0053] The heat exchange plate 21 has a first water channel with back-and-forth flow. A water inlet 213 and a water outlet 214 are provided at one of the corners of the heat exchange plate. The water inlet 213 and the water outlet 214 are both connected to the first water channel in the heat exchange plate. One water pipe passes through the water inlet holes of several heat exchange plates in sequence, and the other water pipe passes through the water outlet holes of several heat exchange plates in sequence. The liquid guiding ribs 24 are arranged between adjacent heat exchange plates 21 and are tightened and compressed by the heat exchange plates to form a second water channel with back-and-forth flow between each two adjacent heat exchange plates. The water inlet of the second water channel is connected to the space above the water-water heat exchanger 2, and the space above the water-water heat exchanger 2 is connected to the cold water inlet. The water outlet of the second water channel is connected to the space below the water-water heat exchanger 2, and the space below the water-water heat exchanger 2 is connected to the cold water outlet of the shell. The parts of the two water pipes located between adjacent heat exchange plates are correspondingly covered with seals 23. The seals 23 and the liquid guiding ribs 24 are all pressed by the heat exchange plates. After tightening, a heat exchange module is formed.

[0054] Low-grade hot wastewater is fed into the first water channel of the heat exchanger with low input and high output; cold water is fed into the second water channel of the heat exchanger with high input and low output; the low-grade hot wastewater forms a back-and-forth flow from bottom to top in the heat exchanger, and the cold water forms a back-and-forth flow from top to bottom in the heat exchanger; the low-grade hot wastewater and cold water form countercurrent and crosscurrent flows to carry out water-water indirect heat exchange.

[0055] One way to assemble the heat exchange module is to Figure 3 and Figure 4 , install a heat exchange plate on two water pipes, one water pipe through the water inlet hole 213, and the other water pipe through the water outlet hole 214, then put the seal 23 on the water pipe, and put the liquid guide rib 24 close to the heat exchange plate, then install another heat exchange plate on the water pipe, stack them up in sequence, and press the heat exchange plates tightly. Figure 3In the illustrated assembly, after the heat exchange plates are compressed, the water guide boxes of adjacent heat exchange plates are abutted and connected, the seals are pressed tightly between adjacent heat exchange membranes, and the liquid-conducting ribs are pressed tightly between adjacent heat exchange plates to form a second water channel. The water guide pipe can be a hollow metal circular tube with one end open and the other closed, with water outlets evenly distributed on the wall of the water guide pipe. The seal 23 can be a sealing gasket, and the thickness of the seal is preferably such that it just abuts between adjacent heat exchange membranes.

[0056] As an embodiment of a single heat exchange plate, see Figures 5 to 8 The heat exchange plate 21 includes a heat exchange diaphragm 211 and two water guide boxes 212. The heat exchange diaphragm has a plurality of first flow channels 215 arranged in parallel. The water inlet hole 213 and the water outlet hole 214 are respectively opened at one of the corners of the heat exchange diaphragm. The first flow channel passes through the heat exchange diaphragm in a direction parallel to the diaphragm, and the water inlet hole and the water outlet hole pass through the heat exchange diaphragm in a direction perpendicular to the diaphragm. The axis of the water guide hole is perpendicular to the axis of the first flow channel.

[0057] The two water guide boxes are respectively located on both sides of the heat exchange diaphragm in the vertical direction. The two water guide boxes are respectively sealed with the two ends of the first flow channel. For example, the two water guide boxes can be connected to the heat exchange diaphragm as a whole by welding. The inside of the water guide box is divided into a number of independent second flow channels 216 in the vertical direction. The second flow channels are correspondingly connected to the first flow channels, so that the inside of the heat exchange plate is shaped like the first water channel described above.

[0058] As a correspondence between the second flow channel and the first flow channel, see Figure 7 Each second flow channel 215 corresponds to two adjacent first flow channels 216. The second flow channels 216 in the two water guide boxes are staggered in the height direction. The overlapping parts of the second flow channels 216 on both sides share one first flow channel 215. The adjacent two first flow channels 215 are connected in sequence through the corresponding second flow channels 216. Figure 7 Taking the orientation shown in as an example, from bottom to top, the first flow channels of the first row and the second row are connected by the second flow channel on the right, the first flow channels of the second row and the third row are connected by the second flow channel on the left, and the overlapping parts of the second flow channel on the left and the second flow channel on the right share the first flow channel of the second row. Similarly, a first water channel with back-and-forth flow as shown in 7 is formed in the heat exchange plate.

[0059] The liquid-conducting ribs 24 are located in the gaps between adjacent heat exchange plates and are used to form a second water channel for back-and-forth flow in the gaps between the heat exchange plates. As a distribution method of the liquid-conducting ribs 24, see Figure 6 and Figure 7, including transverse ribs 24a and longitudinal ribs 24b, the longitudinal ribs are arranged close to the water guide boxes on both sides, the direction of the longitudinal ribs is consistent with the water guide boxes, all transverse ribs extend horizontally and are staggered up and down; one end of the transverse rib is spaced against the longitudinal rib on the side, and the other end is spaced with the longitudinal rib on the opposite side to reserve a water opening 24c, for example, Figure 6 and Figure 7 For example, from bottom to top, the left ends of all even-numbered rows of transverse ribs abut against the left longitudinal rib, and a water-through opening is reserved between the right end and the right longitudinal rib; the right ends of all odd-numbered rows of transverse ribs abut against the right longitudinal rib, and a water-through opening is reserved between the left end and the left longitudinal rib; the connection between the transverse ribs and the longitudinal ribs is sealed, for example, the transverse ribs and the longitudinal ribs abutted therewith can be an integrally formed structure.

[0060] After the adjacent heat exchange plates are stacked and pressed, a second water channel is formed in the gap between the heat exchange plates by the liquid-conducting ribs. The longitudinal ribs seal the vertical sides of the gap between the heat exchange plates, and the transverse ribs divide the space enclosed by the longitudinal ribs into a second water channel that folds back and forth from top to bottom. The second water channel has a water inlet and a water outlet. The water inlet is located at the top of the diaphragm and communicates with the space above the heat exchanger. The water outlet is located at the bottom of the diaphragm and communicates with the space below the heat exchanger. Cold water enters the shell from the cold water inlet and flows into the second water channel by gravity, forming a back-and-forth folding flow from top to bottom in the second water channel, and is finally discharged from the shell through the cold water outlet.

[0061] Based on the improvements to the flow channel, this application further selects the diaphragm material. The heat exchange diaphragm uses a plastic diaphragm to minimize the thickness of the heat exchange plate and improve heat exchange efficiency. As a specific choice of plastic diaphragm, the heat exchange diaphragm can be formed by melt-extruding polyester plastic or polypropylene plastic and graphite. The diaphragm is extruded to form a parallel porous structure. The through-holes within the diaphragm serve as the first flow channel. The weight percentage of graphite is 0.3%-5%.

[0062] The heat exchange membrane of the present application has a thickness of 5-7 mm; the thickness of the liquid-conducting ribs is 3-6 mm; and the flow ratio between the second water channel and the first water channel is controlled at 0.7 to 1.1:1.

[0063] A method for using the above heat exchange device to recover waste heat from low-grade hot wastewater includes:

[0064] Low-grade hot wastewater with an inlet temperature of less than 60°C is fed into the first water channel in each heat exchange plate of the water-water heat exchanger through the bottom water pipe of the water-water heat exchanger, and flows back and forth from bottom to top under the guidance of the flow channel of the first water channel; cold water is fed into the shell of the heat exchange device through the pipeline and enters the second water channel between adjacent diaphragms in the water-water heat exchanger under the action of gravity, and flows back and forth from top to bottom under the guidance of the liquid-guiding ribs; the low-grade hot wastewater and cold water form countercurrent and crosscurrent flows through the wall of the heat exchange plate, and carry out indirect water-water heat exchange; the heated cold water falls from the bottom of the water-water heat exchanger and is discharged from the bottom of the shell; the low-grade hot wastewater in the first water channel.

[0065] The flow ratio of cold water to low-grade hot wastewater is controlled to be 0.7-1.1:1; the cold water flow in the second water channel is 80-260 L / h; the operating pressure of the first circulation water channel is less than 0.08 MPa.

[0066] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0067] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A water-water heat exchange device for recovering waste heat from low-grade hot wastewater, characterized in that: The invention comprises a shell and a water-water heat exchanger installed in the shell, wherein a cold water inlet is provided on the shell and above the water-water heat exchanger, and a cold water outlet is provided at the bottom of the shell; The water-water heat exchanger includes at least one heat exchange module, which includes two water pipes, a plurality of heat exchange plates, and liquid-conducting ribs. The heat exchange plates have a first water channel for back-and-forth water flow, and one of the corners of the heat exchange plates has a water inlet and a water outlet that pass through the heat exchange plates and communicate with the first water channel. The liquid-conducting ribs are arranged between adjacent heat exchange plates and are tightened and compressed by the heat exchange plates to form a second water channel for back-and-forth water flow between each two adjacent heat exchange plates. The two water pipes respectively penetrate the water inlet and outlet holes of the plurality of heat exchange plates and are then tightened to form the heat exchange module. The water inlet of the second water channel is connected to the cold water inlet, and the water outlet is connected to the cold water outlet; the first water channel is used to circulate low-grade hot wastewater below 60°C, and the low-grade hot wastewater flows from bottom to top in the first water channel; the second water channel is used to circulate cold water, and the cold water flows from top to bottom in the second water channel.

2. The water-water heat exchange device according to claim 1, characterized in that: The heat exchange plate comprises: A heat exchange diaphragm having a plurality of first flow channels arranged in parallel therein, wherein the water inlet and the water outlet are respectively located at a pair of corners of the heat exchange diaphragm, the first flow channels penetrate the heat exchange diaphragm in a direction parallel to the heat exchange diaphragm, and the water inlet and the water outlet penetrate the heat exchange diaphragm in a direction perpendicular to the heat exchange diaphragm; The two water guide boxes are respectively located on both sides of the heat exchange diaphragm in the vertical direction and are sealed and connected to the heat exchange diaphragm as a whole. The water guide boxes are vertically divided into a number of independent second flow channels. The second flow channels are correspondingly connected to the first flow channels to form the first water channels in the heat exchange plate.

3. The water-water heat exchange device according to claim 2, characterized in that: Each second flow channel corresponds to two adjacent first flow channels and the second flow channels in the two water guide boxes are staggered. The parts of the second flow channels on both sides that are staggered in height share one first flow channel, and the two adjacent first flow channels are connected in sequence through the corresponding second flow channels.

4. The water-water heat exchange device according to claim 2, characterized in that: The heat exchange diaphragm is a plastic diaphragm.

5. The water-water heat exchange device according to claim 2, characterized in that: The thickness of the heat exchange membrane is 5-7 mm; the thickness of the liquid-conducting ribs is 3-6 mm.

6. The water-water heat exchange device according to claim 2, characterized in that: The extension direction of the liquid-conducting ribs is parallel to the extension direction of the first flow channel in the heat exchange plate.

7. The water-water heat exchange device according to claim 2, characterized in that: The liquid-conducting ribs include transverse ribs and longitudinal ribs. The longitudinal ribs are respectively close to the two water guide boxes and are consistent with the extension direction of the water guide boxes. The transverse ribs extend horizontally and are staggered up and down. One end of the transverse rib is spaced apart from the longitudinal rib on that side, and the other end is spaced apart from the longitudinal rib on the opposite side to reserve a water opening.

8. The water-water heat exchange device according to claim 2, characterized in that: The heat exchange module further comprises a plurality of sealing members, which are correspondingly sleeved on the water pipes between adjacent heat exchange plates and pressed by the heat exchange plates.

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