A membrane microchannel absorption thermal management system

Abstract

This invention belongs to the field of thermal energy management technology and relates to a membrane microchannel absorption thermal management system, suitable for high heat flux density heat dissipation scenarios such as data centers. The system consists of a copper microchannel base plate, a liquid-blocking and venting membrane, a metal membrane support layer, a condenser plate, and a solution circulation system. The base plate and the support layer form a spatial gradient electric field generator. The solution circulation system uses a 40-55% lithium bromide or lithium chloride aqueous solution for circulation, and a cooling water tank is also provided to regulate the solution concentration. This system actively enhances the phase change of water molecule evaporation with a spatial gradient electric field, and increases the heat exchange area by combining the microchannel structure, upgrading single-phase heat exchange to phase change heat exchange. Experiments show that when a 6KV electric field is applied, the steady-state temperature of the heat source is as low as 41.5℃, the heat dissipation efficiency is significantly improved, the dependence on mechanical pumps is reduced, energy consumption is lower, and the modular design has good compatibility, making it suitable for upgrading and transforming existing data centers.

Description

Technical Field

[0001] This invention belongs to the field of thermal energy management technology, specifically relating to a membrane microchannel absorption thermal management system. Background Technology

[0002] With the rapid development of industries such as cloud computing and artificial intelligence, the computing density and power density of data center servers continue to rise, and the heat flux density generated by chips is increasing day by day, placing higher demands on the heat dissipation efficiency of thermal management systems. At present, cold plate liquid cooling technology is the mainstream solution for data center thermal management. Its core is to drive coolant through cold plate channels by mechanical pumps, and use forced convection heat exchange to remove heat from the chips.

[0003] However, existing cold plate liquid cooling systems have significant drawbacks: on the one hand, coolant circulation is highly dependent on mechanical pumps. As the power density of server racks increases, the pump head and flow rate requirements increase, leading to a continuous rise in the proportion of pump power consumption in the total power consumption of data centers, thus weakening the energy efficiency advantage of liquid cooling technology; on the other hand, existing technologies mostly rely on passive regulation using single physical fields such as concentration difference and temperature difference, improving heat transfer efficiency only by optimizing channel geometry or improving surface characteristics. This results in slow response speed, insufficient phase change heat transfer, and difficulty in fundamentally solving the heat dissipation bottleneck in high heat flux density scenarios.

[0004] Therefore, developing a thermal management system that can actively enhance phase change heat transfer and reduce energy consumption has become an urgent need in the field of thermal energy management. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a membrane microchannel absorption thermal management system. This system utilizes a spatial gradient electric field to actively regulate the movement of water molecules to enhance evaporation phase change, thereby improving heat dissipation efficiency and reducing system energy consumption.

[0006] To achieve the objectives of this invention, the following technical solutions are adopted.

[0007] A membrane-type microchannel absorption thermal management system includes, from bottom to top, a copper microchannel base plate, a liquid-blocking and venting membrane, a metal membrane support layer, and a condenser plate, as well as a matching solution circulation system; wherein:

[0008] A copper microchannel base plate has a lower surface that is a heat-conducting surface in contact with the surface of the object to be cooled, and an upper surface that has a microchannel area formed by at least two parallel microchannels and is grounded.

[0009] The liquid-blocking and ventilating membrane is a microfiltration membrane that covers the upper surface of a copper microchannel substrate and has its outer edge sealed to the outer edge of the microchannel area.

[0010] The metal film support layer has a copper mesh structure composed of triangular cross-section grid units with twice the number of microchannels. The apex of each triangular cross-section grid unit faces the liquid-blocking and ventilating membrane, covers the upper surface of the liquid-blocking and ventilating membrane, and its outer edge is sealed to the outer edge of the liquid-blocking and ventilating membrane. It is connected to a high-voltage DC power supply and forms a spatial gradient electric field generator with the copper microchannel base plate. The electric field intensity is gradient distributed along the direction perpendicular to the liquid surface.

[0011] The condenser plate has its lower outer edge sealed to the outer edge of the metal film support layer, forming a vapor chamber inside.

[0012] The solution circulation system includes a low-concentration storage tank, a high-concentration storage tank, and a solution. The solution is a lithium bromide aqueous solution or a lithium chloride aqueous solution with a mass concentration of 40-55% and is stored in the low-concentration storage tank. The outlet of the low-concentration storage tank is connected to the inlet of the microchannel via a delivery pump. The outlet of the microchannel is connected to the inlet of the high-concentration storage tank. The outlet of the vapor chamber is also connected to the inlet of the high-concentration storage tank. The outlet of the high-concentration storage tank is connected to the inlet of the low-concentration storage tank, thus forming a solution circulation loop.

[0013] Furthermore, the solution circulation system also includes a cooling water tank, the outlet of which is connected to the water supply port of the high-concentration storage tank via a cooling water pump. When the concentration in the high-concentration storage tank exceeds 60%, the cooling water pump starts automatically and stops automatically when the concentration drops to 50%.

[0014] Furthermore, the depth of the microchannel is 0.1-1.0 mm, the width is 0.1-1.0 mm, the length of the microchannel is 2-5 cm shorter than the object to be cooled, and the number of microchannels is determined by the size of the heat dissipation object.

[0015] Furthermore, the microfiltration membrane has a pore size of 1.0 μm and a porosity of 80%.

[0016] Furthermore, the triangle is an equilateral triangle with a side length of 0.05-0.5 mm.

[0017] Furthermore, the output voltage of the high-voltage DC power supply is 2-6KV.

[0018] Furthermore, the gradient distribution varies in the range of 0.01-0.08 V / Å.

[0019] Furthermore, the triangular cross-section grid cells of the metal film support layer are uniformly distributed, and the spacing between adjacent triangular cross-section grid cells matches the width of the corresponding microchannel, so as to achieve uniform distribution of the spatial gradient electric field in the microchannel region.

[0020] Furthermore, the sealing connection is achieved through a combination of sealant or gasket and locking bolts.

[0021] Furthermore, the inner wall of the microchannel is polished to reduce the flow resistance of the low-concentration lithium bromide aqueous solution and improve the heat exchange efficiency.

[0022] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0023] (1) Significantly improved heat dissipation efficiency: By actively breaking the hydrogen bonds of water molecules through the spatial gradient electric field, the single-phase heat exchange of traditional cold plate liquid cooling is upgraded to a high-efficiency phase change heat exchange, making full use of the latent heat of vaporization of water and greatly improving the heat dissipation rate, which can be adapted to high heat flux density scenarios.

[0024] (2) Reduced energy consumption: Electric field enhanced evaporation reduces the dependence on mechanical pumps and reduces cycle energy consumption. At the same time, the absorption cycle design enables the reuse of working fluid, reducing resource consumption and carbon emissions.

[0025] (3) High stability: Modular design makes the core components easy to assemble, and conventional materials and mature manufacturing processes ensure system reliability; the concentration and liquid level monitoring mechanism of the solution circulation subsystem is adapted to dynamic heat load changes;

[0026] (4) Good compatibility: It can be flexibly installed in existing data center server racks, is highly compatible with traditional cold plate liquid cooling architecture, and supports the upgrading and transformation of existing data centers. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the membrane microchannel absorption thermal management system.

[0028] Figure 2 A comparison diagram of a membrane microchannel absorption thermal management system and a traditional cold plate heat dissipation system;

[0029] Figure 3 A comparison diagram of heat dissipation for membrane microchannel absorption thermal management systems with different gradient electric fields;

[0030] Explanation of reference numerals in the attached diagram: 1 is a cooling water tank; 2 is a cooling water pump; 3 is a high-concentration storage tank; 4 is a low-concentration storage tank; 5 is a delivery pump; 6 is a liquid-blocking and venting membrane; 7 is a copper microchannel base plate; 8 is a metal membrane support layer; 9 is a condenser plate. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0032] As an embodiment 1 of the present invention, such as Figure 1As shown, a membrane microchannel absorption thermal management system includes, from bottom to top, a copper microchannel base plate 7, a liquid-blocking and venting membrane 6, a metal membrane support layer 8, and a condenser plate 9, as well as a matching solution circulation system; wherein:

[0033] A copper microchannel base plate 7 has a lower surface that is a heat-conducting surface in contact with the surface of the object to be cooled, and an upper surface with a microchannel region formed by 50 parallel microchannels, which is grounded; wherein the depth of each microchannel is 1.0 mm and the width is 1.0 mm.

[0034] The liquid-blocking and gas-permeable membrane 6 is a microfiltration membrane with a pore size of 1.0 μm and a porosity of 80%. It covers the upper surface of the copper microchannel base plate 7 and its outer edge is connected to the outer edge of the microchannel area by sealant.

[0035] The metal film support layer 8 has a copper mesh structure composed of 100 equilateral triangular cross-section grid units with a side length of 0.5 mm. The apex of each triangular cross-section grid unit faces the liquid-blocking and ventilating membrane 6, covers the upper surface of the liquid-blocking and ventilating membrane 6, and its outer edge is connected to the outer edge of the liquid-blocking and ventilating membrane 6 by sealant. It is connected to a high-voltage DC power supply with an output voltage of 6KV, and together with the copper microchannel base plate 7, it forms a spatial gradient electric field generator with the electric field intensity gradient distributed along the direction perpendicular to the liquid surface. The electric field intensity varies from 0.01 to 0.08 V / Å. The triangular cross-section grid units of the metal film support layer 8 are uniformly distributed, and the spacing between adjacent triangular cross-section grid units matches the width of the corresponding microchannel to achieve a uniform distribution of the spatial gradient electric field in the microchannel region.

[0036] The lower edge of the condenser plate 9 is connected to the outer edge of the metal film support layer 8 by sealant, forming a vapor chamber inside;

[0037] The solution circulation system includes a low-concentration storage tank 4, a high-concentration storage tank 3, and a solution; wherein: the solution is a 40% lithium bromide aqueous solution and is stored in the low-concentration storage tank 4. The outlet of the low-concentration storage tank 4 is connected to the inlet of the microchannel through a delivery pump, the outlet of the microchannel is connected to the inlet of the high-concentration storage tank 3, the outlet of the vapor chamber is also connected to the inlet of the high-concentration storage tank 3, and the outlet of the high-concentration storage tank 3 is connected to the inlet of the low-concentration storage tank 4, so as to form a solution circulation loop.

[0038] As an embodiment 2 of the present invention, such as Figure 1 As shown, a membrane microchannel absorption thermal management system includes, from bottom to top, a copper microchannel base plate 7, a liquid-blocking and venting membrane 6, a metal membrane support layer 8, and a condenser plate 9, as well as a matching solution circulation system; wherein:

[0039] A copper microchannel base plate 7 has a lower surface that is a heat-conducting surface in contact with the surface of the object to be cooled, and an upper surface with a microchannel region formed by 100 parallel microchannels, which is grounded; wherein the depth of the microchannels is 0.1 mm and the width is 0.5 mm.

[0040] The liquid-blocking and gas-permeable membrane 6 is a microfiltration membrane with a pore size of 1.0 μm and a porosity of 80%. It covers the upper surface of the copper microchannel base plate 7 and its outer edge is connected to the outer edge of the microchannel area by sealant.

[0041] The metal film support layer 8 has a copper mesh structure composed of 200 equilateral triangular cross-section grid units with a side length of 0.1 mm. The apex of each triangular cross-section grid unit faces the liquid-blocking and ventilating membrane 6, covers the upper surface of the liquid-blocking and ventilating membrane 6, and its outer edge is connected to the outer edge of the liquid-blocking and ventilating membrane 6 by sealant. It is connected to a high-voltage DC power supply with an output voltage of 2KV, and together with the copper microchannel base plate 7, it forms a spatial gradient electric field generator with the electric field intensity gradient distributed along the direction perpendicular to the liquid surface. The electric field intensity varies from 0.01 to 0.08 V / Å. The triangular cross-section grid units of the metal film support layer 8 are uniformly distributed, and the spacing between adjacent triangular cross-section grid units matches the width of the corresponding microchannel to achieve a uniform distribution of the spatial gradient electric field in the microchannel region.

[0042] The lower edge of the condenser plate 9 is connected to the outer edge of the metal film support layer 8 by sealant, forming a vapor chamber inside;

[0043] The solution circulation system includes a low-concentration storage tank 4, a high-concentration storage tank 3, and a solution; wherein: the solution is a 40% lithium bromide aqueous solution and is stored in the low-concentration storage tank 4. The outlet of the low-concentration storage tank 4 is connected to the inlet of the microchannel through a delivery pump, the outlet of the microchannel is connected to the inlet of the high-concentration storage tank 3, the outlet of the vapor chamber is also connected to the inlet of the high-concentration storage tank 3, and the outlet of the high-concentration storage tank 3 is connected to the inlet of the low-concentration storage tank 4, so as to form a solution circulation loop.

[0044] As an embodiment 3 of the present invention, such as Figure 1 As shown, a membrane microchannel absorption thermal management system includes, from bottom to top, a copper microchannel base plate 7, a liquid-blocking and venting membrane 6, a metal membrane support layer 8, and a condenser plate 9, as well as a matching solution circulation system; wherein:

[0045] A copper microchannel base plate 7 has a lower surface that is a heat-conducting surface in contact with the surface of the object to be cooled, and an upper surface with a microchannel region formed by 50 parallel microchannels, which is grounded; wherein the depth of the microchannels is 0.5 mm and the width is 0.1 mm.

[0046] The liquid-blocking and gas-permeable membrane 6 is a microfiltration membrane with a pore size of 1.0 μm and a porosity of 80%. It covers the upper surface of the copper microchannel base plate 7 and its outer edge is connected to the outer edge of the microchannel area by sealant.

[0047] The metal film support layer 8 has a copper mesh structure composed of 100 equilateral triangular cross-section grid units with a side length of 0.25 mm. The apex of each triangular cross-section grid unit faces the liquid-blocking and ventilating membrane 6, covers the upper surface of the liquid-blocking and ventilating membrane 6, and its outer edge is connected to the outer edge of the liquid-blocking and ventilating membrane 6 by sealant. It is connected to a high-voltage DC power supply with an output voltage of 4KV, and together with the copper microchannel base plate 7, it forms a spatial gradient electric field generator with the electric field intensity distributed in a gradient along the direction perpendicular to the liquid surface. The electric field intensity varies from 0.01 to 0.08 V / Å. The triangular cross-section grid units of the metal film support layer 8 are uniformly distributed, and the spacing between adjacent triangular cross-section grid units matches the width of the corresponding microchannel to achieve a uniform distribution of the spatial gradient electric field in the microchannel region.

[0048] The lower edge of the condenser plate 9 is connected to the outer edge of the metal film support layer 8 by sealant, forming a vapor chamber inside;

[0049] The solution circulation system includes a low-concentration storage tank 4, a high-concentration storage tank 3, and a solution; wherein: the solution is a 40% lithium bromide aqueous solution and is stored in the low-concentration storage tank 4. The outlet of the low-concentration storage tank 4 is connected to the inlet of the microchannel through a delivery pump, the outlet of the microchannel is connected to the inlet of the high-concentration storage tank 3, the outlet of the vapor chamber is also connected to the inlet of the high-concentration storage tank 3, and the outlet of the high-concentration storage tank 3 is connected to the inlet of the low-concentration storage tank 4, so as to form a solution circulation loop.

[0050] As an embodiment 4 of the present invention, such as Figure 1 As shown, the solution circulation system also includes a cooling water tank 1, whose outlet is connected to the water supply port of a high-concentration storage tank 3 via a cooling water pump 2. When the concentration in the high-concentration storage tank exceeds 60%, the cooling water pump starts automatically and stops automatically when the concentration drops to 50%.

[0051] As an embodiment 5 of the present invention, the inner wall of each of the microchannels is polished to reduce the flow resistance of the low-concentration lithium bromide aqueous solution and improve the heat exchange efficiency.

[0052] In a membrane-type microchannel absorption thermal management system, a low-concentration lithium bromide aqueous solution is transported from a low-concentration storage tank 4 to the microchannels of a copper microchannel base plate 7 via a pump. During flow within the microchannels, the solution is heated by heat from the object to be cooled at the bottom. Simultaneously, under the influence of the spatial gradient electric field formed between the grounded copper microchannel base plate 7 and the high-voltage mesh metal membrane support layer 8, water molecules experience asymmetric electric field forces at the gas-liquid interface, accelerating hydrogen bond breakage and increasing the evaporation rate. Water vapor permeates through the liquid-blocking and venting membrane 6 and encounters the condenser plate 9, condensing into liquid water. This liquid water enters a high-concentration storage tank 3 and mixes with the lithium bromide solution, which has increased in concentration after flowing through the microchannels, to dilute it. The diluted low-concentration solution then flows back to the low-concentration storage tank 4, completing the solution regeneration cycle. Furthermore, cooling water from a cooling water tank 1 located adjacent to the high-concentration storage tank 3 is added to the high-concentration storage tank 3 when the condensation rate of the condenser plate 9 is low, ensuring that the solution concentration meets the requirements. Overall, the evaporation phase change is enhanced by a spatial gradient electric field, and the latent heat of water vaporization is used to remove heat from the object to be cooled, thus achieving efficient cooling.

[0053] As a verification example of the present invention, such as Figures 2 to 3 As shown, based on the current actual operation of the data center, we selected a heat flux density of 2.41 kW / m². 2 Experiments were conducted on a constant power heat source simulation server. By recording the temperature changes of the constant power heat source in real time, the heat dissipation performance and temperature control capability of the present invention under different operating conditions were characterized.

[0054] As can be seen from the temperature change curves, both the conventional cold plate (Baseline) and the membrane microchannel device of this invention (without an applied electric field) completed heating within 120 minutes and then entered a thermal steady state with no significant fluctuations in the heat source temperature, meeting the requirements of data center scenarios requiring 24 / 7 uninterrupted operation. After entering the thermal steady state, the heat source equilibrium temperature of the conventional cold plate stabilized at 64.4℃, while the heat source equilibrium temperature of the membrane microchannel device, without an applied gradient electric field, dropped to 59.8℃, a decrease of 4.6℃ compared to the conventional cold plate. This indicates that the membrane microchannel device of this invention, through its micron-scale flow channel structure, significantly increases the heat transfer area per unit volume. Simultaneously, the extremely thin fluid boundary layer within the microchannel, continuously broken and rebuilt, results in a convective heat transfer coefficient far exceeding that of a conventional cold plate with a conventional scale channel. Figure 2 As shown, even without electric field enhancement, its heat dissipation and temperature control capabilities are superior to the current mainstream traditional cold plate liquid cooling solutions, providing an excellent performance foundation for subsequent enhancement and control of gradient electric fields.

[0055] To verify the enhancing effect of the spatial gradient electric field on heat dissipation performance, comparative tests were conducted on a membrane microchannel device with potentials of 0 kV, 2 kV, 4 kV, and 6 kV. The test results showed that all four electric field conditions reached thermal steady state within 300 minutes, and the steady-state temperature of the heat source decreased significantly with increasing applied electric field strength, directly demonstrating the positive enhancing effect of the spatial gradient electric field on heat dissipation performance. Specifically, under the condition without an electric field, the steady-state temperature of the heat source in the membrane microchannel device was 59.8℃, consistent with the baseline condition of a traditional cold plate. After applying a 2 kV potential to the positive electrode, the steady-state temperature of the heat source decreased to 55.4℃, a reduction of 4.4℃ compared to the condition without an electric field, indicating that a lower electric field gradient has a preliminary enhancing effect on evaporative heat transfer. When the potential was increased to 4 kV, the steady-state temperature of the heat source further decreased to 47.5℃, a reduction of 12.3℃ compared to the 0 kV condition. When a 6 kV potential is applied, the device achieves optimal temperature control, with a steady-state temperature of only 41.5℃, a significant reduction of 18.3℃ compared to the condition without an electric field. This represents a breakthrough in heat dissipation performance. Figure 3 As shown.

[0056] From a mechanistic perspective, the gradient electric field proposed in this invention disrupts the force balance of water molecules at the gas-liquid interface at the microscopic level, accelerating hydrogen bond breakage and water molecule escape, significantly increasing the evaporation rate of the working fluid, directly leading to a substantial leap in phase change heat transfer capacity, and thus achieving a significant reduction in the heat source temperature. Simultaneously, under all electric field conditions, the temperature fluctuation amplitude after the device enters thermal steady state is less than 1℃, proving that the introduction of the gradient electric field does not affect the system's operational stability. This invention can achieve long-term, stable, and efficient cooling effects under different electric field strengths, meeting the temperature control requirements of high-power-density computing equipment in data centers, and providing technical support for the iterative upgrade of data center cooling systems.

[0057] The preferred embodiments of the present application have been described above with reference to the accompanying drawings, but this does not limit the scope of the claims of the present application. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and substance of the embodiments of the present application shall be within the scope of the claims of the present application.

Claims

1. A membrane-type microchannel absorption thermal management system, characterized in that: The system comprises, from bottom to top, a copper microchannel base plate, a liquid-blocking and gas-permeable membrane, a metal membrane support layer, and a condenser plate, as well as a matching solution circulation system; wherein: A copper microchannel base plate has a lower surface that is a heat-conducting surface in contact with the surface of the object to be cooled, and an upper surface that has a microchannel area formed by at least two parallel microchannels and is grounded. The liquid-blocking and ventilating membrane is a microfiltration membrane that covers the upper surface of a copper microchannel substrate and has its outer edge sealed to the outer edge of the microchannel area. The metal film support layer has a copper mesh structure composed of triangular cross-section grid units with twice the number of microchannels. The apex of each triangular cross-section grid unit faces the liquid-blocking and ventilating membrane, covers the upper surface of the liquid-blocking and ventilating membrane, and its outer edge is sealed to the outer edge of the liquid-blocking and ventilating membrane. It is connected to a high-voltage DC power supply and forms a spatial gradient electric field generator with the copper microchannel base plate. The electric field intensity is gradient distributed along the direction perpendicular to the liquid surface. The condenser plate has its lower outer edge sealed to the outer edge of the metal film support layer, forming a vapor chamber inside. The solution circulation system includes a low-concentration storage tank, a high-concentration storage tank, and a solution. The solution is a lithium bromide aqueous solution or a lithium chloride aqueous solution with a mass concentration of 40-55% and is stored in the low-concentration storage tank. The outlet of the low-concentration storage tank is connected to the inlet of the microchannel via a delivery pump. The outlet of the microchannel is connected to the inlet of the high-concentration storage tank. The outlet of the vapor chamber is also connected to the inlet of the high-concentration storage tank. The outlet of the high-concentration storage tank is connected to the inlet of the low-concentration storage tank, thus forming a solution circulation loop.

2. The membrane microchannel absorption thermal management system according to claim 1, characterized in that: The solution circulation system also includes a cooling water tank, whose outlet is connected to the water supply port of the high-concentration storage tank via a cooling water pump. When the concentration in the high-concentration storage tank exceeds 60%, the cooling water pump starts automatically and stops automatically when the concentration drops to 50%.

3. The membrane microchannel absorption thermal management system according to claim 2, characterized in that: The depth and width of the microchannels are 0.1-1.0 mm, the length of the microchannels is 2-5 cm shorter than the object to be cooled, and the number of microchannels is determined by the size of the heat dissipation object.

4. The membrane microchannel absorption thermal management system according to claim 3, characterized in that: The microfiltration membrane has a pore size of 1.0 μm and a porosity of 80%.

5. A membrane microchannel absorption thermal management system according to claim 4, characterized in that: The triangle is an equilateral triangle with a side length of 0.05-0.5 mm.

6. The membrane microchannel absorption thermal management system according to claim 5, characterized in that: The output voltage of the high-voltage DC power supply is 2-6KV.

7. A membrane microchannel absorption thermal management system according to claim 6, characterized in that: The gradient distribution varies from 0.01 to 0.08 V / Å.

8. A membrane microchannel absorption thermal management system according to claim 7, characterized in that: The triangular cross-section grid cells of the metal film support layer are uniformly distributed, and the spacing between adjacent triangular cross-section grid cells matches the width of the corresponding microchannel, so as to achieve uniform distribution of the spatial gradient electric field in the microchannel region.

9. A membrane microchannel absorption thermal management system according to claim 8, characterized in that, The sealing connection is achieved by a combination of sealant or gasket and locking bolts.

10. A membrane microchannel absorption thermal management system according to claim 9, characterized in that, The inner wall of the microchannel is polished to reduce the flow resistance of the low-concentration lithium bromide aqueous solution and improve the heat exchange efficiency.

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