Heat exchange cloth, heat exchange plate and air-water heat exchanger using the same

Abstract

The present invention belongs to the technical field of heat exchangers, and particularly relates to a heat exchange fabric, a heat exchange plate using the same, and an air-water heat exchanger. The heat exchange fabric comprises a PTFE membrane, a PTFE fiberglass fabric, and a hydrophilic fabric, wherein the PTFE membrane is disposed on the outside of the PTFE fiberglass fabric, and the hydrophilic fabric is bonded to the inside of the PTFE fiberglass fabric. The PTFE fiberglass fabric is formed by infiltrating a PTFE emulsion into the fiberglass membrane and then curing it. The heat exchange plate comprises a water distributor, a water collector, and a heat exchange bag made of the heat exchange fabric. The water distributor and water collector are respectively disposed at the openings at both ends of the heat exchange bag. The water distributor is provided with a water inlet pipe and an exhaust port, and the water collector is provided with a water outlet pipe. The air-water heat exchanger comprises a heat exchanger housing and a heat exchange plate disposed within the housing. The present invention is used for waste heat recovery from high-temperature exhaust gas, significantly reducing cost and volume, simplifying processing, convenient installation, and achieving high heat exchange efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat exchangers, and in particular relates to a heat exchange cloth and a heat exchange plate and an air-water heat exchanger using the same. Background Art

[0002] Waste gas heat recovery has always been a focus of attention. Flue gas, for example, contains SO₃, SO₂, water (in gaseous form), and other components. Flue gas typically emits at around 150°C, containing a significant amount of heat. However, once the flue gas cools to its dew point, condensation forms, transforming the SO₃ and SO₂ into liquid sulfuric acid and sulfurous acid. While these liquids are not highly acidic upon condensation, in unstable wind conditions, the hot flue gas dries and condenses them into concentrated acid, making them highly corrosive. Currently, only one material, PTFE (the king of plastics), can withstand this corrosion, but it has poor thermal conductivity and a high price. Existing PTFE heat exchangers primarily utilize plate and tube heat exchangers, which have poor thermal conductivity and are expensive. Due to their low cost-performance ratio, they are only used in specialized applications. Summary of the Invention

[0003] In view of the above problems, the purpose of the present invention is to provide a heat exchange cloth and a heat exchange plate and an air-water heat exchanger using the same, so as to solve the problem that the existing PTFE heat exchanger has a low cost performance due to poor thermal conductivity and high price.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] An embodiment of the present invention provides a heat exchange cloth, comprising a PTFE membrane, a PTFE glass fiber cloth, and a hydrophilic cloth, wherein the PTFE membrane is disposed on the outside of the PTFE glass fiber cloth, and the hydrophilic cloth is bonded to the inside of the PTFE glass fiber cloth.

[0006] The PTFE glass fiber cloth is formed by infiltrating PTFE emulsion into the glass fiber cloth and then curing it.

[0007] The glass fiber cloth is formed by blending glass fiber and metal wire.

[0008] PTFE emulsion is evenly applied on the outer side of the TFE glass fiber membrane to form the PTFE membrane; the thickness of the PTFE membrane is 10 μm to 50 μm.

[0009] The surface of the hydrophilic cloth is provided with an elastic thread support structure, and the elastic thread support structure is embedded in the grid-like structure on the surface of the hydrophilic cloth.

[0010] The hydrophilic cloth is woven with a composite thread, which is made by adding a thread made of modified nylon with a hydrophilic factor and then adding elastic yarn.

[0011] Another embodiment of the present invention provides a heat exchange plate, including a water distributor, a water collector and a heat exchange bag made of the above-mentioned heat exchange cloth, wherein the two ends of the heat exchange bag are open structures, the water distributor and the water collector are respectively arranged at the two end openings of the heat exchange bag, the water distributor is provided with a water inlet pipe and an exhaust port, and the water collector is provided with a water outlet pipe.

[0012] The heat exchange bag is formed by stacking two pieces of heat exchange cloth with their hydrophilic surfaces facing each other, and sewing the two sides of the two pieces of heat exchange cloth.

[0013] Both sides of the heat exchange bag are sewn with folded edges along the height direction, and the folded edges protrude outwards.

[0014] Another embodiment of the present invention provides an air-water heat exchanger, comprising a heat exchanger shell and the heat exchanger plates as described above; wherein the top and bottom of the heat exchanger shell are respectively provided with a smoke outlet and a smoke inlet; a plurality of groups of heat exchanger plates arranged in parallel are provided in the heat exchanger shell, the water inlet pipes of the water distributors of the plurality of groups of heat exchanger plates are connected through a water inlet main pipe, the water outlet pipes of the water collectors of the plurality of groups of heat exchanger plates are connected through a water outlet main pipe, and the water inlet main pipe and the water outlet main pipe are led out from the heat exchanger shell.

[0015] The advantages and beneficial effects of the present invention are as follows: the heat exchange cloth provided by the present invention utilizes the corrosion resistance of tetrafluoroethylene (PTFE) and makes it very thin to increase its heat transfer performance, and is compounded with glass fiber with excellent thermal conductivity and functional cloth made of nylon with hydrophilic groups to form a heat exchange cloth with both corrosion resistance and heat exchange functions.

[0016] The heat exchanger in this invention utilizes a hydrophilic inner surface. Water trapped within the elastic support structure of the hydrophilic fabric forms a downward-flowing water film, separated from the external heat medium by only a thin PTFE film, resulting in countercurrent heat transfer. This water film minimizes heat transfer during operation, resulting in high heat transfer efficiency and a heat transfer coefficient comparable to that of conventional steel heat exchangers, all while being lightweight.

[0017] The gas-water heat exchanger of the present invention is used for waste heat recovery of high-temperature exhaust gas. Compared with the existing PTFE heat exchanger, the cost and volume are greatly reduced, the processing is simple, the installation is convenient, the heat exchange efficiency is high, and the heat transfer coefficient is basically similar to that of ordinary steel heat exchangers. In addition, the weight is light, which is only one-fifth to one-tenth of that of the steel heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic structural diagram of a heat exchange cloth in one embodiment of the present invention;

[0019] Figure 2 This is a schematic structural diagram of a heat exchange plate in another embodiment of the present invention;

[0020] Figure 3 for Figure 2 Rear view;

[0021] Figure 4 for Figure 2 AA section view;

[0022] Figure 5 This is a schematic diagram of the working principle of a heat exchange plate in another embodiment of the present invention;

[0023] Figure 6 This is a structural schematic diagram of an air-water heat exchanger in another embodiment of the present invention;

[0024] In the figure: 1 is PTFE membrane, 2 is PTFE glass fiber cloth, 3 is hydrophilic cloth, 10 is heat exchange bag, 11 is water distributor, 12 is water inlet pipe, 13 is exhaust port, 14 is water outlet pipe, 15 is water collector, 16 is suture, 17 is folded edge, 18 is closed cavity, 20 is heat exchange plate, 21 is heat exchanger shell, 22 is water inlet main pipe, 23 is water outlet main pipe, M is hot flue gas, N is flue gas after cooling, Q is cold water, and E is hot water. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] like Figure 1 As shown, one embodiment of the present invention provides a heat exchange cloth, including a PTFE membrane 1, a PTFE glass fiber cloth 2 and a hydrophilic cloth 3, wherein the PTFE membrane 1 is arranged on the outside of the PTFE glass fiber cloth 2, and the hydrophilic cloth 3 is bonded to the inside of the PTFE glass fiber cloth 2.

[0027] In the embodiment of the present invention, the PTFE glass fiber cloth 2 is formed by infiltrating PTFE emulsion into the glass fiber cloth and then curing it. Preferably, the glass fiber cloth is blended with glass fiber and metal wire to improve thermal conductivity.

[0028] Furthermore, PTFE emulsion is evenly applied on the outer side of the PTFE glass fiber cloth 2 to form a PTFE membrane 1. The PTFE membrane 1 has corrosion resistance. The thickness of the PTFE membrane 1 is 10 μm to 50 μm, which increases its heat conductivity.

[0029] In the embodiment of the present invention, the surface of the hydrophilic cloth 3 is provided with an elastic thread support structure, and the elastic thread support structure is embedded in the grid structure on the surface of the hydrophilic cloth 3 .

[0030] Specifically, the hydrophilic fabric 3 is woven from a composite yarn. The composite yarn is made from modified nylon with a hydrophilic factor and then incorporating elastic yarn. Once the composite yarn is woven, it is woven according to specific process specifications into a flexible hydrophilic fabric 3. The elastic yarn forms an elastic yarn support structure on one side of the hydrophilic fabric 3. The other side of the hydrophilic fabric 3 is a planar structure, through which it is bonded to the PTFE fiberglass fabric 2. The elastic yarn support structure is embedded in the surface of the hydrophilic fabric 3, stretching the hydrophilic fibers and maintaining a permanently loose structure. The thickness after compression is approximately 0.2-0.3 mm, and after expansion is approximately 1.5 mm. The water layer can reach a constant operating temperature of 150°C. The loose structure facilitates water absorption and allows it to flow slowly under gravity. The slowly descending water absorbs more heat, generating a higher temperature. The hydrophilic fabric 3 is woven into a grid pattern, with grooves in the grid forming internal airflow channels to ensure stable internal air pressure during operation. Preferably, the elastic yarn in this embodiment is made of polyurethane fiber. Its elasticity is derived from the inherent properties of the polymer, not from structural elasticity achieved by physically crimping the fibers. Its resilience is 95% to 99%. The elastic yarn exhibits excellent durability, dimensional stability, tensile and compressive elasticity, exhibits exceptional elasticity in both dry, wet, and hot conditions, and is unaffected by humidity.

[0031] An embodiment of the present invention provides a heat exchange cloth, the preparation process of which is as follows:

[0032] (1) The process of customizing PTFE glass fiber cloth 2 is as follows: ①, high-quality glass fiber is used to weave glass fiber cloth, and the fineness and length of the glass fiber meet the requirements; in order to improve thermal conductivity, metal wire can be added for blending; ②, Teflon emulsion (PTFE emulsion) is applied to the glass fiber cloth, and the Teflon dispersion penetrates into the blended glass fiber cloth, and is rolled to make it dense, thereby forming PTFE glass fiber cloth 2; a layer of Teflon emulsion is evenly sprayed on the surface of one side of the PTFE glass fiber cloth 2, and after the Teflon emulsion reaches a certain condition, a PTFE film 1 with uniform thickness and relatively thin is formed; Teflon emulsion is not sprayed on the surface of the other side of the PTFE glass fiber cloth 2, and the emulsion on the surface of the glass fiber cloth on this side is removed so as to bond the hydrophilic cloth 3.

[0033] (2) The process of making the hydrophilic cloth 3 is as follows: according to the weaving process, modified nylon material with hydrophilic groups is used to make thread at the raw material end, elastic yarn is added to make composite thread after the thread is made, and after the composite thread is made, it is made into hydrophilic heat-absorbing cloth according to certain process rules.

[0034] (3) The hydrophilic cloth 3 is compounded with the PTFE glass fiber cloth 2 by using a dispensing method with heat-resistant glue. After compounding, the heat exchange cloth is formed and cut into a fixed width for later use. The heat exchange cloth is made of hydrophilic material, and under gravity conditions, a water film is formed to flow as a heat exchange medium, reducing water consumption and increasing water temperature.

[0035] The heat exchange cloth provided by the present invention utilizes the corrosion resistance of tetrafluoroethylene (PTFE) and makes it very thin to increase its heat transfer performance. It is then compounded with glass fiber with excellent thermal conductivity and functional cloth made of nylon with hydrophilic groups to form a heat exchange cloth with both corrosion resistance and heat exchange functions.

[0036] like Figure 2-4 As shown, another embodiment of the present invention provides a heat exchange plate, including a water distributor 11, a water collector 15 and a heat exchange bag 10 made of the heat exchange cloth in the above embodiment, wherein both ends of the heat exchange bag 10 are open structures, the water distributor 11 and the water collector 15 are respectively arranged at the openings at both ends of the heat exchange bag 10, the water distributor 11 is provided with a water inlet pipe 12 and an exhaust port 13, and the water collector 15 is provided with a water outlet pipe 14.

[0037] Specifically, the heat exchange bag 10 is composed of two pieces of heat exchange cloth stacked with the hydrophilic surfaces facing each other. The two pieces of heat exchange cloth are sewn together on both sides with stitches 16 to form a closed cavity 18 between the two pieces of heat exchange cloth. An exhaust port 13 is left at the upper end of the closed cavity 18.

[0038] Furthermore, both side surfaces of the heat exchange bag 10 are sewn along the height direction to form fold edges 17, and the fold edges 17 protrude outward.

[0039] like Figure 5 As shown, in the embodiment of the present invention, the function of the water distributor 11 is to evenly distribute the water introduced by the water inlet pipe 12 to the hydrophilic cloth 3 on both sides. The hydrophilic cloth 3 absorbs the water, forming a water film that flows evenly downward under the action of gravity. The downward water absorbs heat on the side of the PTFE membrane, is collected by the water collector 15, and then flows out of the water outlet pipe 14. The gas in the closed chamber 18 flows upward and is then discharged through the exhaust port 13.

[0040] The folds 17 on both sides of the heat exchange bag 10 have a certain height, which is the gap between the two heat exchange fins. Since the heat exchange fins are made of soft materials, condensation water is easily formed on the PTFE membrane side, and the surface tension of water can ensure that the gap between the heat exchange fins is fixed.

[0041] During heat exchange operation, cold water enters the water distributor 11 from the water inlet main 22. The water distributor 11 evenly distributes water above the heat exchange bag 10, and the water flows downward under gravity. Since the inner wall of the heat exchange bag 10 is made of hydrophilic material, water is contained in the elastic thread support structure of the hydrophilic cloth 3 to form a water film that flows downward. The water film is separated from the external heat medium by only a very thin polytetrafluoroethylene film, thus generating countercurrent heat transfer. An exhaust port 13 is left at the center of the upper part of the water distributor 11. When the heat exchange plate is in operation, the wind speed between the plates is greater than the internal wind speed of the heat exchange bag 10, and the exhaust port 13 forms a negative pressure. The air inside the exhaust port can only go out but not in. Since the heat exchange medium is a water film, the amount of heat exchange medium used during operation is small, the heat exchange efficiency is high, and the heat transfer coefficient is basically similar to that of an ordinary steel heat exchanger. It is also light in weight, weighing only one-fifth to one-tenth of the weight of a steel heat exchanger.

[0042] like Figure 6 As shown, another embodiment of the present invention provides an air-water heat exchanger, comprising a heat exchanger shell 21 and the heat exchanger plates 20 in the above embodiment; wherein the top and bottom of the heat exchanger shell 21 are respectively provided with a smoke outlet and a smoke inlet; a plurality of groups of heat exchanger plates 20 arranged in parallel are provided in the heat exchanger shell 21, the water inlet pipes 12 of the water distributors 11 of the plurality of groups of heat exchanger plates 20 are connected through a water inlet main pipe 22, the water outlet pipes 14 of the water collectors 15 of the plurality of groups of heat exchanger plates 20 are connected through a water outlet main pipe 23, and the water inlet main pipe 22 and the water outlet main pipe 23 are led out from the heat exchanger shell 21.

[0043] During heat exchange operation, hot flue gas M enters the heat exchanger shell 21 through the flue gas inlet at the bottom of the heat exchanger shell 21 and flows upward. Cold water Q enters the water distributor 11 of the multiple sets of heat exchanger fins 20 through the water inlet main 22. The water distributor 11 evenly distributes water above the heat exchanger bag 10, and the water flows downward under gravity. Because the inner wall of the heat exchanger bag 10 is made of a hydrophilic material, water contained in the elastic support structure of the hydrophilic cloth 3 forms a water film that flows downward. The water film is separated from the hot flue gas M by only a very thin polytetrafluoroethylene film, thus generating countercurrent heat transfer. An exhaust port 13 is located at the top center of the water distributor 11. When the heat exchanger fins 20 are in operation, the wind speed between the fins is greater than the wind speed inside the heat exchanger bag 10, forming a negative pressure at the exhaust port 13, and the air inside the exhaust port can only exit but not enter. Because the heat exchange medium is a water film, the heat exchange medium usage during operation is small.

[0044] Specifically, multiple heat exchange fins 20 are hung in the heat exchanger shell 21, and a certain pulling force is applied to the upper water distributor and the lower water collector to straighten the heat exchange fins 20. Then all the heat exchange fins 20 are sealed to form an air-water heat exchanger.

[0045] The hot flue gas M flows upward under the power of the fan, while water flows downward from a height, creating a countercurrent heat exchange. The water and gas are separated by a partition wall, forming a partition wall heat exchanger. This partition wall is a soft PTFE composite membrane composed of two layers: the first layer is PTFE membrane, and the second layer is glass fiber or steel-glass fiber composite. The first layer of PTFE membrane has poor thermal conductivity, but its thickness is extremely thin, only 10μm to 50μm, with a thermal conductivity coefficient of 0.3W / m*K. Similarly, the thermal conductivity of stainless steel at 100°C is 16.3W / m*K. Although the thermal conductivity of PTFE is significantly different, the thermal conductivity of a 1mm thick stainless steel plate is 16.3kW / 1mm*K, while the thermal conductivity of a 20μm thick PTFE plate is 15kW / 20μ*K. In other words, the heat transfer effect of a 20μm thick PTFE plate is essentially the same as that of a 1mm thick stainless steel plate. The second layer of glass fiber (the structural strength layer) conducts heat better and, due to its thinness, is closer to that of metal. The main reason is that the heat transfer coefficient of gas is too poor, such as 0.026W / (m·K) for air at room temperature. Therefore, gas-to-water heat exchange requires sufficient heat exchange area. The gas-to-water heat exchanger of the present invention is as effective as a metal plate heat exchanger, while solving the dew point corrosion problem that metal plate and tube heat exchangers cannot solve. The cost of the same area is even lower than that of metal plate and tube heat exchangers.

[0046] Similarly, compared with the rigid heat exchanger, the water film under the suction of the hydrophilic factor of the heat absorbing cloth and gravity has a normal flow rate of 5-50mm / s, and can flow evenly. In contrast, the flow rate of water inside the rigid partition heat exchanger is in m / s, such as the normal flow rate of a tap water pipe is 1m / s. Since the heat content of the same volume of gas on the gas side is very low relative to the water on the water side, at room temperature 1m 3 When the gas drops 1℃, the heat released / absorbed is about 1.29KJ, while the same volume of 1m 3 The water also releases and absorbs about 4200KJ of heat when the temperature drops by 1℃. Therefore, only a thin water layer and low flow rate can ensure that the heat absorption on the water side of the heat exchanger and the heat rejection on the gas side can reach a balance. Only in this way can the desired high-temperature hot water be obtained after convective heat transfer. This is also difficult to achieve in heat exchangers with hard heat exchangers.

[0047] In this embodiment, the heat exchanger fins (bags) can be very long; a single fin can be 10 to 20 meters long or even longer. This allows for a long countercurrent heat transfer path, which is not possible with rigid fins. The suspended fins (bags) are extremely easy to assemble, and the heat exchanger can be constructed into a tower, transforming it into a heat exchange tower.

[0048] Another embodiment of the present invention provides an air-water heat exchanger for recovering waste heat from high-temperature exhaust gas. Compared to existing PTFE heat exchangers, this device significantly reduces cost and size, is simple to manufacture and install, and offers high heat exchange efficiency, achieving a heat transfer coefficient similar to that of conventional steel heat exchangers. Furthermore, it is lightweight, weighing only one-fifth to one-tenth the weight of steel heat exchangers. Because the heat exchange medium is a water film, minimal heat exchange medium usage is achieved during operation.

[0049] The above description is only an embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modification, equivalent replacement, improvement, expansion, etc. made within the spirit and principle of the present invention are included in the scope of protection of the present invention.

Claims

1. An air-water heat exchanger, characterized in that: It comprises a heat exchanger shell (21) and heat exchange fins (20); wherein the top and bottom of the heat exchanger shell (21) are respectively provided with a smoke outlet and a smoke inlet; The heat exchange plate (20) includes a water distributor (11), a water collector (15), and a heat exchange bag (10) made of heat exchange cloth, wherein both ends of the heat exchange bag (10) are open structures, the water distributor (11) and the water collector (15) are respectively arranged at the openings at both ends of the heat exchange bag (10), the water distributor (11) is provided with a water inlet pipe (12) and an exhaust port (13), and the water collector (15) is provided with a water outlet pipe (14); The heat exchange bag (10) is formed by stacking two pieces of heat exchange cloth with their hydrophilic surfaces facing each other, sewing the two pieces of heat exchange cloth on both sides, and forming a closed cavity (18) between the two pieces of heat exchange cloth; both sides of the heat exchange bag (10) are sewn with folded edges (17) along the height direction, and the folded edges (17) protrude outwards; The heat exchange cloth comprises a PTFE membrane (1), a PTFE glass fiber cloth (2) and a hydrophilic cloth (3), wherein the PTFE membrane (1) is arranged on the outside of the PTFE glass fiber cloth (2), and the hydrophilic cloth (3) is bonded to the inside of the PTFE glass fiber cloth (2); The PTFE glass fiber cloth (2) is formed by infiltrating PTFE emulsion into the glass fiber cloth and then solidifying it; the glass fiber cloth is formed by blending glass fiber and metal wire; PTFE emulsion is evenly applied on the outer side of the PTFE glass fiber cloth (2) to form the PTFE membrane (1); the thickness of the PTFE membrane (1) is 10 μm to 50 μm; The surface of the hydrophilic cloth (3) is provided with an elastic thread support structure, and the elastic thread support structure is embedded in the surface grid structure of the hydrophilic cloth (3); the hydrophilic cloth (3) is woven with a composite thread, and the composite thread is made of a thread made of modified nylon with a hydrophilic factor and then added with elastic thread; The function of the water distributor (11) is to distribute the incoming water introduced by the water inlet pipe (12) evenly to the hydrophilic cloths (3) on both sides. After the hydrophilic cloths (3) absorb water, they form a water film and flow down evenly under the action of gravity. The water flowing down absorbs heat on the side of the PTFE membrane (1) and is collected by the water collector (15). The water then flows out through the water outlet pipe (14). The gas in the closed cavity (18) flows upward and is discharged through the exhaust port (13). The heat exchanger housing (21) is provided with a plurality of sets of heat exchange fins (20) arranged in parallel. The water inlet pipes (12) of the water distributors (11) of the plurality of sets of heat exchange fins (20) are connected via a water inlet main pipe (22). The water outlet pipes (14) of the water collectors (15) of the plurality of sets of heat exchange fins (20) are connected via a water outlet main pipe (23). The water inlet main pipe (22) and the water outlet main pipe (23) are led out of the heat exchanger housing (21).

Images