A gas gap type membrane distillation module

Abstract

This invention discloses a novel air-gap membrane distillation assembly. The assembly includes two hot-side cover plates, two membrane distillation units, and a heat dissipation component. Its key feature is that both membrane distillation units can perform a complete membrane distillation process, with the cold side of each unit cooled by a semiconductor cooling chip. Simultaneously, the hot-side flow channel is designed onto a hot-side gasket, which is fixed to the hot-side cover plate with countersunk screws, forming a replaceable flow channel structure. Furthermore, the thickness of the cold-side air gap can be changed by replacing silicone gaskets of different thicknesses. This reduces energy consumption and saves time and material costs.

Description

Technical Field

[0001] This invention belongs to the field of membrane distillation technology, and specifically relates to a thermoelectric cooling air gap membrane distillation assembly with two hot sides and replaceable flow channels. Background Technology

[0002] With the establishment of the goals of "carbon peaking and carbon neutrality," environmental protection has risen to a new level of national strategic objectives. Achieving efficient conversion and clean utilization of waste is a crucial link in realizing these dual-carbon goals. As industrial production technologies continue to evolve, the resulting liquid and solid wastes also exhibit new characteristics, including an increase in the types and properties of pollutants, making treatment more difficult. In particular, the organic matter in liquid waste is often biotoxic and difficult to degrade, leading to increased harm and persistence after being released into the environment. Furthermore, these liquid wastes face problems such as low removal rates or high economic costs in practical engineering applications. Therefore, a new type of treatment device is urgently needed.

[0003] Membrane distillation technology, as a novel separation technology combining excellent separation performance and energy-saving potential, is gradually gaining attention. Membrane distillation is a novel separation technology that combines a thermodynamic process (distillation) with a membrane separation process, and it is widely used in the desalination, desalination, and concentration processes of seawater, brackish water, and industrial wastewater. Membrane distillation technology utilizes a microporous hydrophobic membrane to separate two solutions. The volatile components in the two solutions at different temperatures will generate a vapor pressure difference across the membrane. This vapor pressure difference acts as the driving force for the membrane distillation process, allowing the volatile components in the feed solution on the higher temperature side to pass through the hydrophobic membrane as gas molecules; simultaneously, liquids, insoluble substances, and ions are completely retained on the feed solution side, thereby achieving the purpose of concentrating the feed solution and separating the volatile components.

[0004] There are four main types of membrane distillation: direct contact, air-gap, vacuum, and gas-swept. Direct contact membrane distillation is the most studied type, due to its simple structure, ease of operation, and high membrane flux; however, it also suffers from significant transmembrane heat transfer losses. Research on air-gap membrane distillation is relatively limited, but it boasts the highest thermal efficiency among the four basic types.

[0005] The cold side of existing membrane distillation modules is cooled by chilled water. This requires first using a refrigeration unit to draw cooling water below 10°C, and then piped into the cold-side chamber of the membrane module to circulate the cooling water and achieve cooling. This process is inefficient, results in significant energy loss during cooling water circulation, and leads to high energy consumption of the refrigeration unit.

[0006] Meanwhile, the structure of the flow channel and the thickness of the air gap are also important factors affecting the distillation efficiency of air-gap membrane modules. In existing membrane modules, the flow channel and air gap are achieved by slotting the cover plate, and once fabricated, they cannot be changed. However, research on membrane distillation often requires modifying the structure of the flow channel and the thickness of the air gap to study how to improve the efficiency of membrane distillation. This necessitates the fabrication of a large number of membrane modules, resulting in significant material waste and high costs. Summary of the Invention

[0007] This invention addresses the shortcomings of existing membrane distillation technologies mentioned above by providing a novel air-gap membrane distillation module. This further improves the efficiency of membrane distillation, achieving the goal of efficient conversion and clean utilization of waste liquid.

[0008] This invention provides a novel air-gap membrane distillation assembly. The assembly includes two hot-side cover plates, two membrane distillation devices, and a heat dissipation assembly, wherein both membrane distillation devices can perform a complete membrane distillation process. The heat dissipation assembly is located in the middle, with the two membrane distillation devices located on the front and rear sides of the heat dissipation assembly, respectively, and the hot-side cover plates located on the outer sides of the membrane distillation devices. For greater accuracy and clarity, the membrane distillation devices are divided into a front distillation device and a rear distillation device based on their location, and the hot-side cover plates are referred to as the upper hot-side cover and the lower hot-side cover.

[0009] For membrane distillation to proceed smoothly, a hot-side cavity for the flow of heated feed liquid, a hydrophobic membrane, and a cold-side cavity are required. In the aforementioned front-side distillation apparatus, the hot-side cavity is formed by combining a hot-side cover and a silicone gasket. One side of the hot-side cover has a groove, while the silicone gasket has an opening; the size of the groove matches the size of the opening. One side of the silicone gasket is tightly fitted to the hot-side cover, while the other side is fitted to the hydrophobic membrane. This creates a cavity between the hydrophobic membrane and the hot-side cover, forming the hot-side cavity. The cold-side cavity is formed by combining a silicone gasket and a cold-side copper plate. The silicone gasket also has an opening; one side of the silicone gasket is fitted to the hydrophobic membrane, while the other side is tightly fitted to the cold-side copper plate. This creates a cavity between the hydrophobic membrane and the cold-side copper plate, forming the cold-side cavity.

[0010] On the one hand, the flow channels in existing membrane modules are engraved on the inner wall of the hot-side cover and cannot be replaced. This invention, however, designs the flow channels separately on a 3D-printed gasket, which is fixed to a groove in the hot-side cover using countersunk screws, creating a replaceable flow channel structure. On the other hand, the hydrophobic membrane and cold-side copper plate in the cold-side cavity are both complete planes, with openings only in the silicone gasket. Therefore, the thickness of the silicone gasket is the thickness of the cold-side cavity. This invention, however, is an air-gap membrane distillation module, where the thickness of the cold-side cavity is the thickness of the air gap. This allows the thickness of the air gap to be changed by replacing silicone gaskets of different thicknesses.

[0011] The structure of the rear distillation apparatus is the same as that of the front distillation apparatus, and will not be described in detail here.

[0012] In particular, since the hot-side flow channel is a replaceable structure, different hot-side gaskets can be placed on the hot-side upper cover and the hot-side lower cover to give the two hot sides different flow channel structures; at the same time, the thickness of the silicone gasket in the cold-side cavity can also be different, that is, different air gap thicknesses.

[0013] Membrane distillation requires a temperature difference. The hot-side chamber contains the heated working fluid, which has a high temperature. In contrast, the low temperature on the cold side of a gas-gap membrane distillation device is reflected in the cold-side copper plate. This invention utilizes a semiconductor cooling chip to cool the cold-side copper plate, thereby maintaining a certain temperature difference between the hot and cold sides of the device and achieving the purpose of membrane distillation.

[0014] During normal operation, the two ends of the thermoelectric cooler exhibit different characteristics. One end has a lower temperature, known as the cold end, while the other end has a higher temperature, known as the hot end. This invention involves bonding the cold end of the thermoelectric cooler to a cold-side copper plate to cool the copper plate. Simultaneously, to enable the thermoelectric cooler to operate for extended periods, a heat dissipation assembly is required to dissipate heat from the thermoelectric cooler.

[0015] The heat dissipation assembly consists of heat dissipation pads and a heat dissipation frame. Heat dissipation copper plates are attached to the left and right sides of the heat dissipation frame, which has openings, thus forming a cavity between the two copper plates. This invention utilizes the flow of cold water within the cavity to cool the heat dissipation copper plates. The heat dissipation copper plates on the left and right sides are respectively in contact with the hot sides of the thermoelectric coolers in the front and rear distillation devices, thereby dissipating heat from the thermoelectric coolers. Simultaneously, to improve the cooling effect, heat dissipation pads are installed within the slots of the heat sink frame. These pads have protrusions on both sides, which alter the flow direction of the cold water within the cavity, causing it to continuously swirl and achieve better heat dissipation.

[0016] On the one hand, compared with the traditional structure that uses cooling water to directly cool the cold side, the present invention has a higher cooling efficiency and a wider cooling range, while consuming less energy. Traditional devices, on the other hand, have a longer cooling time and a limited cooling range, and when the hot side temperature is high, the cold side is affected and it is difficult to lower the temperature to the ideal level. On the other hand, traditional devices have high requirements for the cooling water, requiring a refrigeration mechanism to obtain very low-temperature water for practical use, which consumes a lot of energy. In the present invention, the role of the cooling water is to cool the semiconductor refrigeration chip and it does not directly participate in the membrane distillation process; therefore, the requirements for it are lower, and it is not necessary to use a refrigeration mechanism for pre-cooling. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure;

[0018] Figure 2 This is a schematic diagram of the structure of the heat-side upper cover;

[0019] Figure 3 A schematic diagram showing the arrangement of components in the front distillation unit;

[0020] Figure 4 This is a schematic diagram of the heat dissipation component structure;

[0021] Figure 5 This is a schematic diagram of the cold-side copper plate structure;

[0022] Figure 6 This is a schematic diagram of a semiconductor cooling chip clamping plate structure;

[0023] Figure 7 This is a schematic diagram of the arrangement of semiconductor cooling chips;

[0024] Figure 8 This is a schematic diagram of the heat dissipation copper plate structure;

[0025] Figure 9 This is a schematic diagram of the silicone pad structure;

[0026] Figure 10 This is a schematic diagram showing the arrangement of components in the rear distillation unit.

[0027] As shown in the figure:

[0028] 1. Hot-side top cover, 1-1. Top cover housing, 1-2. Hot-side gasket, 1-3. Countersunk screw, 1-1-1. Hot-side gasket groove, 1-1-2. Water outlet pipe, 1-1-3. Water outlet slot, 1-1-4. Water inlet pipe, 1-1-5. Water inlet slot, 1-1-6. Threaded hole, 1-2-1. Water outlet opening, 1-2-2. Water inlet opening, 1-2-3. Flow channel protrusion, 2. Bolt, 3. Front distillation device, 3-1. Silicone gasket, 3-2. Superhydrophobic film, 3-3. Silicone gasket, 3-4. Cold-side copper plate, 3-4-1. Condensate outlet, 3-5. Semiconductor refrigeration chip clamp, 3-5-1. Semiconductor refrigeration 3-5-2. Water baffle strip, 3-5-3. Condensate outlet, 3-5-4. Condensate collection port, 3-6. Semiconductor cooling chip, 3-7. Heat dissipation copper plate, 4. Heat dissipation component, 4-1. Silicone pad, 4-2. Heat dissipation frame, 4-2-1. Heat dissipation pad groove, 4-2-2. Heat dissipation water outlet, 4-2-3. Heat dissipation water inlet, 4-3. Heat dissipation pad, 4-3-1. Water inlet, 4-3-2. Water inlet groove, 4-3-3. Water outlet, 4-3-4. Water outlet groove, 4-3-5. Front flow channel protrusion, 4-3-6. Rear flow channel protrusion, 5. Rear distillation device component, 6. Hot side lower cover. Detailed Implementation

[0029] To make the advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Since the present invention adopts a symmetrical structure, the front distillation apparatus and the rear distillation apparatus are completely identical in terms of components and component arrangement. Therefore, the front distillation apparatus will be specifically described in the embodiments with reference to the accompanying drawings.

[0030] Example:

[0031] This invention provides a novel air-gap membrane distillation assembly. Its characteristic is that the assembly has two heated sides, front and rear. For example... Figure 1 As shown, the hot-side upper cover 1, when combined with the front distillation device 3, enables a complete membrane distillation process; similarly, the hot-side lower cover 6, when combined with the rear membrane distillation device 5, also enables a complete membrane distillation process. Furthermore, the cold sides of the front and rear distillation devices in this assembly utilize semiconductor cooling, and a heat dissipation component 4 for cooling the semiconductor cooling chip is located between the front and rear distillation devices.

[0032] Semiconductor refrigeration, also known as electronic refrigeration or thermoelectric refrigeration, utilizes a PN junction formed by special semiconductor materials to create thermocouple pairs, thereby generating the Peltier effect and achieving heat transfer. It is a novel refrigeration method that directly cools using direct current. It features no mechanical movement and high refrigeration efficiency. In membrane distillation, the cold side requires a low temperature. This invention utilizes a semiconductor refrigeration chip to cool the cold side, replacing the traditional membrane distillation assembly that relies on a refrigeration mechanism to draw cold water, which continuously circulates within the cold-side cavity to lower the cold-side temperature.

[0033] In principle, a thermoelectric cooler is a heat transfer device. When current flows through it, heat transfer occurs between the two ends of the thermoelectric cooler, creating a temperature difference and forming hot and cold ends. The cold end, which loses heat, contacts the cold-side copper plate 3-4, cooling the cold side during the membrane distillation process. To ensure the thermoelectric cooler can operate efficiently for extended periods, the hot end also needs heat dissipation. In this invention, the hot end of the thermoelectric cooler is in contact with the heat dissipation copper plate 3-7, and the heat dissipation component 4 cools the copper plate, thereby cooling the hot end of the thermoelectric cooler.

[0034] The semiconductor cooling chip used in this invention has a size of 40×40mm and a thickness of 3.7mm. In practical applications, four cooling chips need to be arranged... Figure 7The arrangement shown achieves the best cooling effect. Both the cold-side copper plate and the heat-dissipating copper plate are 0.5mm thick. The membrane distillation assembly of this invention requires bolt fastening. To prevent damage to the thermoelectric cooler or deformation of the copper plate during use, a stainless steel thermoelectric cooler clamping plate 3-5 is provided between the cold-side copper plate and the heat-dissipating copper plate.

[0035] like Figure 7 As shown, a rectangular opening of 100×140mm is provided in the middle of the thermoelectric cooler clamping plate, and four thermoelectric coolers are placed in the opening. The thermoelectric coolers are attached to the cold-side copper plate and the heat-dissipating copper plate by thermal grease. The thermal grease has a certain thickness, so the thickness of the thermoelectric cooler clamping plate is slightly greater than the thickness of the thermoelectric coolers, which is 5mm. At the same time, the operation of the thermoelectric coolers requires current, so a groove 3-5-1 is provided on the thermoelectric cooler clamping plate for the thermoelectric cooler wires to pass through, the groove being 10mm wide and 3mm deep.

[0036] like Figure 4 As shown, the heat dissipation assembly 4 consists of a heat dissipation frame 4-2 and heat dissipation pads 4-3. The heat dissipation frame has a groove 4-2-1 for placing the heat dissipation pads, and through holes for water inflow and outflow on the side of the frame, namely a water inlet 4-2-3 and a water outlet 4-2-2. The heat dissipation pads are directly placed within the grooves of the heat dissipation frame. The heat dissipation pads 4-3 also have through holes for water flow, namely a water inlet 4-3-1 and a water outlet 4-3-3.

[0037] The heat dissipation pad 4-3 has slots on its upper and lower sides for diverting water flow. When external water flows into the inlet 4-3-2 through the heat dissipation water inlet 4-2-3 and inlet 4-3-1, it is divided into two parts: one part flows to the front of the heat dissipation pad, and the other part flows to the rear of the heat dissipation pad, cooling the copper heat dissipation plates on the front and rear sides respectively. Simultaneously, protrusions are provided on both the front and rear sides of the heat dissipation pad to change the direction of water flow, enhance heat exchange, and improve heat dissipation efficiency.

[0038] As mentioned in the previous embodiments, the function of the heat dissipation component is to cool the copper heat sink. Therefore, the copper heat sink is located on both the front and rear sides of the heat dissipation component. To ensure the sealing of the membrane module, a silicone gasket is placed between the copper heat sink and the middle frame of the heat dissipation component. Figure 3 As shown, the front side of the heat dissipation copper plate 3-7 is a semiconductor cooling chip 3-6, while the rear side of the heat dissipation copper plate is a silicone pad 4-1. One side of the silicone pad is attached to the heat dissipation copper plate, and the other side is attached to one side of the heat dissipation assembly frame.

[0039] like Figure 9As shown, the silicone pad has an opening in the center, the size and position of which are the same as the slots on the heat sink frame, both being 100×140mm. Thus, when the heat sink copper plate, silicone pad, and heat sink frame are tightly fitted together, a cavity is formed between the heat sink copper plate and the heat sink pad installed on the heat sink frame, allowing water to flow through. External water flows in through the inlet channel 4-3-2, turbulently within the cavity due to the protrusions on the heat sink pad, and then flows out through the outlet channel 4-3-4, thereby achieving the function of cooling the heat sink copper plate.

[0040] Similarly, on the other side of the heat dissipation frame, there are also silicone pads and a copper heat dissipation plate, which will not be described again here.

[0041] like Figure 2 As shown, the upper cover housing 1-1 has a heat-side gasket groove 1-1-1, with dimensions of 100×140mm and a depth of 4mm. The groove also contains four threaded holes 1-1-6. The heat-side gasket 1-2 is fixed to the groove in the upper cover housing by countersunk screws 1-3. Simultaneously, the upper cover housing also has a water inlet slot 1-1-3 and a water outlet slot 1-1-5; the heat-side gasket has a water inlet opening 1-2-1 and a water outlet opening 1-2-2, both measuring 100×5mm. The openings on the heat-side gasket match the slots on the upper cover housing and are connected to the water inlet pipe 1-1-2 and the water outlet pipe 1-1-4, respectively. The diameter of both the inlet and outlet pipes is 13mm.

[0042] like Figure 5 As shown, water vapor passing through the hydrophobic membrane from the hot side condenses into water droplets on one side of the cold-side copper plate 3-4. To ensure timely drainage of condensate, a 100×5mm opening 3-4-1 is provided on the lower side of the cold-side copper plate. Since a thermoelectric cooler plate 3-5 is mounted on the other side of the cold-side copper plate, an opening 3-5-4 is also provided at the same location on the thermoelectric cooler plate. Additionally, a water-blocking strip 3-5-2 and a groove 3-5-3 for condensate drainage are also provided.

[0043] Water condensed on the cold-side copper plate slides down under gravity and enters the condensate collection port 3-5-4 on the semiconductor cooling chip clamp plate through the condensate outlet 3-4-1 on the cold-side copper plate. Since cold-side copper plates are installed on both the front and rear sides of the semiconductor cooling chip clamp plate, and a water baffle 3-5-2 is provided above the condensate collection port, the condensate in the front and rear distillation devices can only flow out of the component through the condensate outlet 3-5-3 after it is collected here.

[0044] To more clearly illustrate the structure of the membrane distillation assembly of the present invention, the following description is provided in conjunction with... Figure 3 The working process of this membrane distillation apparatus is explained.

[0045] A silicone gasket 3-1 is mounted on the right side of the hot-side top cover 1. A hydrophobic film 3-2 is mounted on the right side of the silicone gasket, and a silicone gasket 3-3 is mounted on the right side of the hydrophobic film. A cold-side copper plate 3-4, a thermoelectric cooler clamping plate 3-5, and a heat dissipation copper plate 3-7 are mounted sequentially on the right side of the silicone gasket 3-3. A thermoelectric cooler 3-6 is placed in the opening of the thermoelectric cooler clamping plate, and its two ends are respectively bonded to the cold-side copper plate and the heat dissipation copper plate with silicone grease. A heat dissipation frame 4-2 is located on the right side of the heat dissipation copper plate, and a heat dissipation gasket 4-3 is directly placed in the groove of the heat dissipation frame. A rear distillation device component 5 is mounted on the right side of the heat dissipation frame, and its arrangement is the same as that of the front distillation device, so it will not be described further. A hot-side bottom cover is located on the right side of component 5 of the rear distillation device, and the threaded hole of the hot-side bottom cover has internal threads. All components except the hot-side bottom cover have through holes, and the components are assembled together by bolts 2.

[0046] The heated working fluid enters the inlet pipe 1-1-4, and then sequentially passes through the inlet slot 1-1-5 on the shell and the inlet opening 1-2-2 on the hot-side gasket into the hot-side cavity. Flocculation occurs due to the flow channel protrusion 1-2-3 on the hot-side gasket. Meanwhile, the semiconductor cooling chip continuously cools the cold-side copper plate 3-4 when energized. When a certain temperature difference is reached between the hot and cold sides, some of the moisture in the hot-side cavity permeates through the hydrophobic membrane 3-2 as water vapor, condenses on the cold-side copper plate 3-4, and then flows out of the membrane distillation assembly, thus realizing the membrane distillation process. Meanwhile, as the membrane distillation process continues, the temperature of the hot end face of the semiconductor cooling chip also rises continuously. External cold water flows into the water inlet 4-2-3 and the water inlet 4-3-1 into the water inlet tank 4-3-2, where it is divided into two parts. One part flows to the front of the heat dissipation pad 4-3, and the other part flows to the back of the heat dissipation pad. Under the influence of the protrusions on the pad, it is turbulent and then discharged through the water outlet, thus playing the role of heat dissipation for the semiconductor cooling chip.

Claims

1. A gas-gap membrane distillation unit, characterized in that: The membrane distillation assembly includes two hot-side cover plates, two membrane distillation devices, and a heat dissipation assembly. The heat dissipation assembly is located in the middle, the two membrane distillation devices are located on the front and rear sides of the heat dissipation assembly, and the hot-side cover plates are located on the outside of the distillation devices. The membrane distillation device consists of a silicone gasket, a hydrophobic membrane, a cold-side copper plate, a semiconductor refrigeration chip, a semiconductor refrigeration chip clamping plate, and a heat dissipation copper plate. The semiconductor refrigeration chip is located at the opening of the semiconductor refrigeration chip clamping plate, and its cold end face and hot end face are respectively attached to the cold-side copper plate and the heat dissipation copper plate with silicone grease. The hydrophobic membrane is located between the hot-side cover plate and the cold-side copper plate, and silicone gaskets are installed between the hydrophobic membrane and the hot-side cover plate, and between the hydrophobic membrane and the cold-side copper plate. The heat dissipation assembly consists of a heat dissipation frame and heat dissipation pads; the heat dissipation frame has a groove for placing the heat dissipation pads, and the heat dissipation pads are placed directly in the grooves of the heat dissipation frame; the two sides of the heat dissipation frame are heat dissipation copper plates, and a silicone gasket is provided between the heat dissipation copper plates and the heat dissipation frame to ensure the sealing of the assembly; flow channel protrusions are provided on the front and rear sides of the heat dissipation pads. The silicone pad has openings, the cavity between the hydrophobic film and the hot side cover plate is the hot side cavity, the cavity between the hydrophobic film and the cold side copper plate is the cold side cavity, the side of the heat dissipation frame has through holes for water to flow in and out, and the heat dissipation pad has a water inlet groove and a water outlet groove.

2. The membrane distillation assembly according to claim 1, characterized in that: The hot-side cover plate consists of a housing, countersunk screws, and a hot-side gasket. The housing is provided with a heat-side gasket groove, a water inlet pipe, a water inlet slot, a water outlet pipe, and a water outlet slot; the heat-side gasket groove is also provided with four threaded holes, and the heat-side gasket is fixed in the groove by countersunk screws; the heat-side gasket is provided with a water inlet hole, and the water outlet hole and the flow channel protrude; the size and position of the water inlet and water outlet holes on the heat-side gasket are the same as the size and position of the water inlet and water outlet slots on the housing.

3. The membrane distillation assembly according to claim 1, characterized in that: The silicone pad has an opening, the size and position of which are the same as the openings on the heat-side pad groove on the housing and the openings on the semiconductor cooling chip clamp.

4. The membrane distillation assembly according to claim 1, characterized in that: The lower side of the cold-side copper plate is provided with an opening for condensate to flow out.

5. The membrane distillation assembly according to claim 1, characterized in that: The semiconductor cooling chip clamp is provided with a semiconductor cooling chip wire outlet slot, a water baffle, a condensate collection port, and a condensate outlet.

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