A double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system and an operation regulation method

Abstract

The present invention discloses a double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system and an operation regulation method, which solves the problem that it is difficult for the existing evaporative cooling air conditioning system to adjust the refrigerating capacity under the condition of constant air supply volume. The double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system comprises a fan, a vacuum membrane dehumidifier, a dew point evaporative cooler, an air duct and a valve; the fan, the vacuum membrane dehumidifier and the dew point evaporative cooler are connected in series in sequence; the vacuum membrane dehumidifier comprises a feed side, a permeate side, a water vapor selective permeable membrane and a porous support layer; the dew point evaporative cooler comprises a dry channel and a wet channel; the air at the outlet of the dew point evaporative cooler is divided into four streams, the first stream is a supply air stream, the second stream is a wet channel air stream, the third stream is a cooling return air stream, and the fourth stream is a dehumidification return air stream. The present invention can provide a technical reference for the development of low-carbon energy-saving air conditioning systems.

Description

Technical Field

[0001] The present invention belongs to the technical field of air temperature and humidity control, and particularly relates to a double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system. Background Art

[0002] Nowadays, with the rapid development of the precision manufacturing industry, the requirements for indoor air temperature and humidity control technology are getting higher and higher, and the energy consumption of air conditioning systems is also increasing. Using independent dehumidification technology to decouple the two links of cooling and dehumidification in the air conditioning process can effectively improve the energy efficiency ratio of the air conditioning system and achieve the purpose of energy conservation and emission reduction.

[0003] Recently, the invention patent with the patent number CN115164282B discloses a vacuum membrane dehumidification heating, ventilation and air conditioning system and its operation control method, which integrates a vacuum membrane dehumidifier and a dew point evaporative cooler. After the air is dehumidified by the vacuum membrane dehumidifier, the system directly uses dew point evaporation cooling for cooling, hoping to solve the problems of high energy consumption and inaccurate temperature and humidity control in comfort air conditioning systems. However, since the regulation of the cooling capacity of the evaporative cooler mainly relies on air volume regulation at present, for an evaporative cooling air conditioning system that arranges the water film by capillary force, it is difficult to regulate the cooling capacity by water volume. For an evaporative cooling air conditioning system with water flow, the regulation of water volume on the cooling capacity is also very limited. Therefore, there are few evaporative cooling technologies that can achieve precise temperature and humidity control under a constant air volume at present. However, many precision manufacturing industrial sites have strict requirements for the indoor air flow organization and air supply volume. Adjusting the cooling capacity of the evaporative cooler on the premise of maintaining the air supply volume unchanged is of great significance for realizing low-carbon air conditioning technology in industrial environments.

[0004] Therefore, it is necessary to provide an evaporative cooling air conditioning system that can achieve precise temperature and humidity control on the premise of maintaining the air supply volume unchanged. Summary of the Invention

[0005] Aiming at the problem that the existing evaporative cooling technology is greatly affected by the environmental temperature and humidity and it is difficult to achieve precise regulation of the supply air temperature and humidity, the present invention proposes a double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system and its operation regulation method, which can adjust the dehumidification and cooling effects by adjusting the return air ratio.

[0006] The present invention provides a double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system, which is characterized in that it includes a fan, a vacuum membrane dehumidifier, a dew point evaporative cooler, an air duct, a valve, and an air duct connector.

[0007] The fan, vacuum membrane dehumidifier, and dew point evaporative cooler are connected in sequence using the air duct. The function of the fan is to provide power for air flow; the function of the vacuum membrane dehumidifier is to reduce the humidity of the air; the function of the dew point evaporative cooler is to lower the temperature of the air while keeping the air humidity unchanged.

[0008] The air flow at the dry channel air outlet of the dew point evaporative cooler is divided into four streams:

[0009] The first stream is the supply air flow, which is a low-temperature and dry product air flow used to provide low-temperature and dry air for production and daily life.

[0010] The second stream is the wet channel air flow, which is introduced into the wet channel of the dew point evaporative cooler through the air duct and can be used to adjust the cooling effect of the dew point evaporative cooler, but this will affect the flow rate of the supply air flow.

[0011] The third stream is the cooling return air flow, which is introduced into the dry channel inlet of the dew point evaporative cooler through the air duct and is used to adjust the cooling effect of the dew point evaporative cooler without affecting the flow rate of the supply air flow.

[0012] The fourth stream is the dehumidification return air flow, which is sent into the feed side of the vacuum membrane dehumidifier through the air duct and is used to adjust the dehumidification effect of the vacuum membrane dehumidifier without affecting the flow rate of the supply air flow.

[0013] The supply air flow is the low-temperature and dry product air flow provided by the dual-return air type vacuum membrane dehumidification evaporative cooling air conditioning system for adjusting the temperature and humidity of the indoor environment; the wet channel air flow is the air flow flowing into the wet channel of the dew point evaporative cooler, and its function is to promote the evaporation of the water film in the wet channel and cool the air in the dry channel of the dew point evaporative cooler; the function of the cooling return air flow is to introduce a part of the air flow back into the inlet of the dew point evaporative cooler to achieve secondary cooling; the function of the dehumidification return air flow is to introduce a part of the air flow back into the inlet of the vacuum membrane dehumidifier to achieve secondary dehumidification.

[0014] The function of the water film is to provide a water source for evaporation for the dew point evaporative cooler to ensure the water source for the cooling and evaporation process of the dew point evaporative cooler. The water film can be evenly distributed on the inner surface of the wet channel through a hydrophilic non-woven fabric.

[0015] The air ducts are connected to each other through air duct connectors, mainly including pipe tees or pipe crosses.

[0016] Each air duct through which the four airflows pass is provided with a valve, and the flow rates of the four airflows are adjusted by adjusting the opening degrees of the four valves. The dual-return vacuum membrane dehumidification evaporative cooling air-conditioning system can adjust the cooling capacity by adjusting the opening degrees of the four valves, the power of the vacuum pump, and the water film flow rate in the wet channel of the dew-point evaporative cooler, while ensuring that the flow rate of the supply air stream remains unchanged. However, adjusting the power of the vacuum pump may affect the efficiency of the vacuum pump, resulting in inefficient operation of the dual-return vacuum membrane dehumidification evaporative cooling air-conditioning system. In addition, for some of the dew-point evaporative coolers, the water film flow rate inside cannot be adjusted.

[0017] The dual-return vacuum membrane dehumidification evaporative cooling air-conditioning system is characterized in that: the vacuum membrane dehumidifier includes a feed side, a permeate side, a water vapor selectively permeable membrane, a support layer, a vacuum pump, and a pneumatic pipeline; the feed side is a flow channel for air, and the air has a higher humidity before entering the feed side and a lower humidity after flowing out of the feed side; the water vapor selectively permeable membrane covers the support layer and divides the vacuum membrane dehumidifier into two relatively independent spaces, namely the feed side and the permeate side; the support layer has a certain rigidity and can resist the deformation of the membrane caused by the pressure difference between the feed side and the permeate side. The inlet of the vacuum pump is connected to the permeate side through the pneumatic pipeline, which is used to maintain a negative pressure environment on the permeate side and timely desorb the water molecules in the membrane; a condensation device can be set at the outlet of the vacuum pump to condense and recover the discharged water vapor, or directly discharge this part of the water vapor into the atmospheric environment.

[0018] The dual-return vacuum membrane dehumidification evaporative cooling air-conditioning system is characterized in that: the dew-point evaporative cooler includes two channels, a dry channel and a wet channel; the dry channel and the wet channel are separated by a material with good thermal conductivity but impermeable to air, such as aluminum plates, copper plates, aluminum tubes, and copper tubes; there is a water film on the inner wall of the wet channel, and the function of the water film is to reduce the temperature of the air in the dry channel by evaporation and provide a water source for the evaporation process; the air flow in the wet channel comes from the outlet of the dry channel.

[0019] The dual-return vacuum membrane dehumidification evaporative cooling air-conditioning system is characterized in that: the performance indicators of the dual-return vacuum membrane dehumidification evaporative cooling air-conditioning system mainly include the cooling capacity and the energy efficiency ratio, and the energy efficiency ratio is the cooling capacity obtained per unit power consumption.

[0020] The operation control method of the dual-return wind vacuum membrane dehumidification evaporative cooling air-conditioning system is characterized in that: the method includes the following steps:

[0021] Step 1: Establish a numerical model of the vacuum membrane dehumidification and evaporative cooling air conditioning system using the heat and mass transfer differential equations. The modeling method for this part of the model is based on physical rule modeling, mainly including the heat and mass transfer differential equation sets for the vacuum membrane dehumidification process and the heat and mass transfer differential equation sets for the dew point evaporative cooling process.

[0022] Heat and mass transfer differential equation sets for vacuum membrane dehumidification:

[0023]

[0024]

[0025]

[0026] Heat and mass transfer differential equation sets for dew point evaporative cooling:

[0027]

[0028]

[0029]

[0030] By combining the above heat and mass transfer differential equation sets for vacuum membrane dehumidification and the heat and mass transfer differential equation sets for dew point evaporative cooling, and matching with the boundary conditions of the actual process, a mathematical model of the vacuum membrane dehumidification and evaporative cooling air conditioning system can be obtained. Among them, ρ represents density, kg m -3 ; represents the flow velocity, m s -1 ; t represents time, s; P represents pressure, Pa; μ represents viscosity, Pa s; represents the body force, N m -3 ; ω represents the concentration of water vapor in the air, mol m -3 ; D represents the diffusion coefficient, m 2 s -1 ; T represents temperature, K; S1 represents the mass source of the vacuum membrane dehumidification process, kg s -1 , which is related to the vacuum degree on the permeation side, the water vapor selective permeable membrane material, and the air flow velocity on the feed side; S2 represents the concentration source, mol kg m -6 s -1 , which is related to the vacuum degree on the permeation side, the water vapor selective permeable membrane material, and the air flow velocity on the feed side; S 3,j represents the mass source of the dew point evaporative cooling process, kg s -1, related to the air velocity in the dry channel, the air velocity in the wet channel, and the water film velocity; S4 represents the heat source, W, related to the air flow velocity in the dry channel, the air flow velocity in the wet channel, and the water film velocity; the subscript j represents the fluid region of the dew point evaporative cooler, j = 1 represents the dry channel, j = 2 represents the wet channel, and j = 3 represents the water film;

[0031] Step 2: Conduct experimental tests on the double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system, and use the experimental data to verify the numerical model established in Step 1; the main function of this part of work is to use the experimental data to verify the numerical model established in Step 1 and clarify the reliability of the numerical model.

[0032] Step 3: Use the numerical model verified in Step 2, solve it using computational fluid dynamics software (such as fluent, OpenFOAM), and conduct parameter sensitivity analysis using the Morris method to identify significant parameters that have an obvious impact on the performance of the double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system; the main significance of this part of work is to clarify which parameters have a more significant impact on the cooling capacity and energy efficiency ratio of the double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system. The parameters involved include: the vacuum degree on the permeation side, the flow rates of the first, second, third, and fourth airflows, and the water film flow rate.

[0033] Step 4: Use the numerical model verified in Step 2 to design an orthogonal experiment table or a response surface experiment table for the significant parameters in Step 2, conduct regression analysis through numerical experiment solving calculations, and obtain the regression mathematical relationship between the performance indicators of the vacuum membrane dehumidification evaporative cooling air conditioning system and the significant parameters described in Step 3; the main significance of this part of work is to establish the regression relationship. Since the regression relationship has a fast operation efficiency, it is suitable for optimization solving.

[0034] Step 5: Use the regression relationship described in Step 4 to perform optimization solving. When ensuring the optimal performance indicators of the double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system, obtain the accurate values of the significant parameters to guide the operation regulation of the vacuum membrane dehumidification evaporative cooling air conditioning system. The main significance of this part of work is to find the operation regulation parameters that can make the performance indicators of the double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system optimal and guide the system operation and maintenance.

[0035] (3) Beneficial effects

[0036] Compared with the prior art, the beneficial effects of the invention are as follows: The invention can apply the evaporative cooling technology to an environment with high humidity, and can flexibly adjust the refrigerating capacity and dehumidifying capacity while ensuring the constant air supply volume; The invention can also give the numerical values of the operating parameters under the condition of keeping the refrigerating capacity and the coefficient of performance of the double-return air vacuum membrane dehumidifying evaporative cooling air-conditioning system optimal, so as to guide the operation and maintenance regulation of the double-return air type vacuum membrane dehumidifying evaporative cooling air-conditioning system. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a schematic diagram of the double-return air type vacuum membrane dehumidifying evaporative cooling air-conditioning system of the present invention;

[0038] Figure 2 is a schematic diagram of the principle of the double-return air type vacuum membrane dehumidifying evaporative cooling air-conditioning system of the present invention;

[0039] The reference numerals in the drawings are: 1, a fan; 2-1, the feeding side housing of the vacuum membrane dehumidifier; 2-2, the water vapor selectively permeable membrane; 2-3, the support layer; 2-4, the permeation side housing of the vacuum membrane dehumidifier; 2-5, a vacuum pump; 3-1, the dry channel housing; 3-2, the heat-conducting air-blocking layer; 3-3, the water film; 3-4, the wet channel housing; 4-1, valve one; 4-2, valve two; 4-3, valve three; 4-4, valve four; 5, an exhaust duct. DETAILED DESCRIPTION OF THE INVENTION

[0040] The present invention will be further described below with reference to the specific drawings.

[0041] A double-return air type vacuum membrane dehumidifying evaporative cooling air-conditioning system, characterized in that: it includes a fan 1, a vacuum membrane dehumidifier 2, a dew-point evaporative cooler 3, an air duct, a valve one 4-1, a valve two 4-2, a valve three 4-3, a valve four 4-4, and an air duct connector;

[0042] The fan 1, the vacuum membrane dehumidifier 2, and the dew-point evaporative cooler 3 are sequentially connected in turn by using the air duct;

[0043] The air flow at the dry channel outlet of the dew-point evaporative cooler is divided into four streams: The first stream is the supply air flow, which is a low-temperature and dry product air flow and flows through the pipeline where the valve one 4-1 is located; The second stream is the wet channel air flow, which is introduced into the wet channel of the dew-point evaporative cooler through the air duct, flows through the pipeline where the valve two 4-2 is located, and is discharged into the atmospheric environment by the exhaust duct 5 after heat exchange in the wet channel; The third stream is the cooling return air flow, which is introduced into the air duct connecting the vacuum membrane dehumidifier and the dew-point evaporative cooler through the air duct and flows through the pipeline where the valve three 4-3 is located; The fourth stream is the dehumidifying return air flow, which is sent into the pipeline between the fan and the vacuum membrane dehumidifier through the air duct and flows through the pipeline where the valve four 4-4 is located;

[0044] The air ducts are connected to each other through air duct connection components;

[0045] A valve is provided in each of the air ducts through which the four airflows pass, and the air flow rate is adjusted by adjusting the opening degrees of the four valves.

[0046] The double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system is characterized in that: the vacuum membrane dehumidifier includes a feed side, a permeate side, a water vapor selective permeable membrane 2-2, a support layer 2-3, a vacuum pump 2-5, and a pneumatic pipeline; between the feed side housing 2-1 and the permeate side housing 2-4 are the water vapor selective permeable membrane 2-2 and the support layer 2-3, the water vapor selective permeable membrane 2-2 covers the support layer 2-3, separating the vacuum membrane dehumidifier into two spaces, namely the feed side and the permeate side; the suction port of the vacuum pump 2-5 is connected to the permeate side through the pneumatic pipeline.

[0047] The double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system is characterized in that: the dew point evaporative cooler includes two channels, a dry channel and a wet channel; the dry channel and the wet channel are separated by a heat-conducting and airtight heat-conducting and air-blocking layer 3-2; there is a water film 3-3 on the inner wall of the wet channel; between the dry channel housing 3-1 and the humidity channel housing 3-4 are the heat-conducting and air-blocking layer 3-2 and the water film 3-3.

[0048] The operation control method of the double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system is characterized in that: the method includes the following steps:

[0049] Step 1: Establish a numerical model of the vacuum membrane dehumidification evaporative cooling air conditioning system by using the heat and mass transfer differential equations. The modeling method of this part of the model is based on physical rules modeling, mainly including the heat and mass transfer differential equation groups for the vacuum membrane dehumidification process and the heat and mass transfer differential equation groups for the dew point evaporative cooling process.

[0050] Heat and mass transfer differential equation groups for vacuum membrane dehumidification:

[0051]

[0052]

[0053]

[0054] Heat and mass transfer differential equation groups for dew point evaporative cooling:

[0055]

[0056]

[0057]

[0058] By combining the above differential equations of heat and mass transfer for vacuum membrane dehumidification and the differential equations of heat and mass transfer for dew point evaporation cooling, and coordinating with the boundary conditions of the actual process, a mathematical model of the vacuum membrane dehumidification evaporation cooling air conditioning system can be obtained. Among them, ρ represents density, kg m -3 ; represents the flow velocity, m s -1 ; t represents time, s; P represents pressure, Pa; μ represents viscosity, Pa s; represents the body force, N m -3 ; ω represents the concentration of water vapor in the air, mol m -3 ; D represents the diffusion coefficient, m 2 s -1 ; T represents temperature, K; S1 represents the mass source in the vacuum membrane dehumidification process, kg s -1 , which is related to the vacuum degree on the permeation side, the water vapor selective permeable membrane material, and the air flow velocity; S2 represents the concentration source, mol kg m -6 s -1 , which is related to the vacuum degree on the permeation side, the water vapor selective permeable membrane material, and the air flow velocity; S 3,j represents the mass source in the dew point evaporation cooling process, kg s -1 , which is related to the air flow velocity in the dry channel, the air flow velocity in the wet channel, and the water film flow velocity; S4 represents the heat source, W, which is related to the air flow velocity in the dry channel, the air flow velocity in the wet channel, and the water film flow velocity; the subscript j represents the fluid region of the dew point evaporator, j = 1 represents the dry channel, j = 2 represents the wet channel, and j = 3 represents the water film;

[0059] Step 2: Conduct experimental tests on the double-return air type vacuum membrane dehumidification evaporation cooling air conditioning system, and verify the numerical model established in Step 1 using the experimental data; the main role of this part of work is to verify the numerical model established in Step 1 using the experimental data and clarify the reliability of the numerical model.

[0060] Step 3: Use the numerical model verified in Step 2, solve it using computational fluid dynamics software (such as fluent, OpenFOAM), and conduct parameter sensitivity analysis using the Morris method to identify the significant parameters that have an obvious impact on the performance of the double-return air type vacuum membrane dehumidification evaporation cooling air conditioning system; the main significance of this part of work is to clarify which parameters have a more significant impact on the cooling capacity and energy efficiency ratio of the double-return air type vacuum membrane dehumidification evaporation cooling air conditioning system. The parameters involved include: the vacuum degree on the permeation side, the flow rates of the first, second, third, and fourth airflows, and the water film flow rate.

[0061] Step 4: Using the numerical model verified in Step 2, design an orthogonal experiment table or a response surface experiment table for the significant parameters in Step 2. Through numerical experiments and calculations, conduct regression analysis to obtain the regression mathematical relationship between the performance indicators of the vacuum membrane dehumidification evaporative cooling air conditioning system and the significant parameters described in Step 3. The main significance of this part of the work is to establish the regression relationship. Since the regression relationship has a relatively high operation efficiency, it is suitable for optimization and solution.

[0062] Step 5: Use the regression relationship described in Step 4 for optimization and solution. When ensuring the optimal performance indicators of the double-return-air vacuum membrane dehumidification evaporative cooling air conditioning system, obtain the accurate values of the significant parameters, which are used to guide the operation regulation of the vacuum membrane dehumidification evaporative cooling air conditioning system. The main significance of this part of the work is to find out the operation regulation parameters that can optimize the performance indicators of the double-return-air vacuum membrane dehumidification evaporative cooling air conditioning system and guide the system operation and maintenance.

[0063] Example 1:

[0064] As Figure 1 and Figure 2 shown, the air that needs to be cooled and dehumidified enters the vacuum membrane dehumidifier 2 under the action of the fan 1. The air realizes isothermal dehumidification in the vacuum membrane dehumidifier 2, and the water vapor in the air is first absorbed by the water vapor selectively permeable membrane 2-2. Then, the water molecules in the membrane are desorbed under the suction of the vacuum pump and discharged from the outlet of the vacuum pump, achieving the effect of dehumidifying the air. The air dehumidified by the vacuum membrane dehumidifier enters the dry channel of the dew-point evaporative cooler 3, and the air flow cools down in the dry channel. The cooled air is divided into four streams:

[0065] The first stream is the supply air flow, which is a low-temperature and dry product air flow and flows through the pipeline where the valve one 4-1 is located;

[0066] The second stream is the wet-channel air flow, which is introduced into the wet channel of the dew-point evaporative cooler through the air duct, flows through the pipeline where the valve two 4-2 is located, and is discharged into the atmospheric environment through the exhaust air duct 5 after heat exchange in the wet channel;

[0067] The third stream is the cooling return air flow, which is introduced into the air duct connecting the vacuum membrane dehumidifier and the dew-point evaporative cooler through the air duct and flows through the pipeline where the valve three 4-3 is located;

[0068] The fourth stream is the dehumidified return air flow, which is sent into the pipeline between the fan and the vacuum membrane dehumidifier through the air duct and flows through the pipeline where the valve four 4-4 is located.

[0069] The air flow required in actual engineering is the first supply air flow. By adjusting the opening degrees of valve 1 4-1, valve 2 4-2, valve 3 4-3, and valve 4 4-4, the refrigerating capacity and energy efficiency coefficient of the double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system can be adjusted on the premise of keeping the air volume of the supply air flow unchanged. The specific operation is as follows:

[0070] Change the opening degree of the valve 3 4-3. At the same time, in order to ensure that the air flow through other valves remains unchanged, it is also necessary to finely adjust the opening degrees of valve 1 4-1, valve 2 4-2, and valve 4 4-4. It can achieve changing the sensible heat refrigerating capacity of the double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system while ensuring that the air volume of the supply air flow and the latent heat refrigerating capacity remain basically unchanged.

[0071] Change the opening degree of the valve 4 4-4 and change the opening degree of the valve 3 4-3 at the same time. In order to ensure that the air flow through valve 1 4-1 and valve 2 4-2 remains unchanged, it is also necessary to finely adjust the opening degrees of valve 1 4-1 and valve 2 4-2. It can change the latent heat refrigerating capacity of the double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system while ensuring that the air volume of the supply air flow and the sensible heat refrigerating capacity remain basically unchanged.

[0072] Example 2:

[0073] As Figure 1 and Figure 2 shown, the air that needs to be cooled and dehumidified enters the vacuum membrane dehumidifier 2 under the action of the fan 1. The air realizes isothermal dehumidification in the vacuum membrane dehumidifier 2. The water vapor in the air is first absorbed by the water vapor selective permeable membrane 2-2. Then, the water molecules in the membrane are desorbed under the suction of the vacuum pump and discharged from the outlet of the vacuum pump, achieving the effect of dehumidifying the air. The air dehumidified by the vacuum membrane dehumidifier enters the dry channel of the dew point evaporative cooler 3, and the air flow cools down in the dry channel. The cooled air is divided into four streams. The first stream is the supply air flow, which is a low-temperature and dry product air flow and flows through the pipeline where the valve 1 4-1 is located; the second stream is the wet channel air flow, which is introduced into the wet channel of the dew point evaporative cooler through the air duct and flows through the pipeline where the valve 2 4-2 is located; the third stream is the cooling return air flow, which is introduced into the air duct connecting the vacuum membrane dehumidifier and the dew point evaporative cooler through the air duct and flows through the pipeline where the valve 3 4-3 is located; the fourth stream is the dehumidified return air flow, which is sent into the pipeline between the fan and the vacuum membrane dehumidifier through the air duct and flows through the pipeline where the valve 4 4-4 is located;

[0074] The air flow required in actual engineering is the first supply air flow. By adjusting the opening degrees of valve 1 4-1, valve 2 4-2, valve 3 4-3, and valve 4 4-4, the refrigerating capacity and energy efficiency coefficient of the double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system can be adjusted on the premise of keeping the air volume of the supply air flow unchanged.

[0075] The operation regulation method of the double-return air type vacuum membrane dehumidification evaporation cooling air conditioning system can achieve more effective regulation of the system, which specifically includes the following steps:

[0076] Step 1: Establish a numerical model of the vacuum membrane dehumidification evaporation cooling air conditioning system by using the heat and mass transfer differential equations. The modeling method of this part of the model is based on physical rules, mainly including the heat and mass transfer differential equations of the vacuum membrane dehumidification process and the heat and mass transfer differential equations of the dew point evaporation cooling process.

[0077] Heat and mass transfer differential equations of vacuum membrane dehumidification:

[0078]

[0079]

[0080]

[0081] Heat and mass transfer differential equations of dew point evaporation cooling:

[0082]

[0083]

[0084]

[0085] By combining the above heat and mass transfer differential equations of vacuum membrane dehumidification and heat and mass transfer differential equations of dew point evaporation cooling, and matching the boundary conditions of the actual process, the mathematical model of the vacuum membrane dehumidification evaporation cooling air conditioning system can be obtained. Among them, ρ represents density, kg m -3 ; represents the flow velocity, m s -1 ; t represents time, s; P represents pressure, Pa; μ represents viscosity, Pa s; represents the body force, N m -3 ; ω represents the concentration of water vapor in the air, mol m -3 ; D represents the diffusion coefficient, m 2 s -1 ; T represents temperature, K; S1 represents the mass source of the vacuum membrane dehumidification process, kg s -1 ; S2 represents the concentration source, mol kg m -6 s -1 ; S 3,j represents the mass source of the dew point evaporation cooling process, kg s -1 ; S4 represents the heat source, W; the subscript j represents the fluid region of the dew point evaporator, j = 1 represents the dry channel, j = 2 represents the wet channel, j = 3 represents the water film;

[0086] Step 2: Conduct experimental tests on the double-return-air type vacuum membrane dehumidification evaporative cooling air conditioning system, and use the experimental data to verify the numerical model established in Step 1; the main function of this part of work is to verify the numerical model established in Step 1 using experimental data and clarify the reliability of the numerical model.

[0087] Step 3: Use the numerical model verified in Step 2, solve it using computational fluid dynamics software (such as fluent, OpenFOAM), and conduct parameter sensitivity analysis using the Morris method to identify significant parameters that have an obvious impact on the performance of the double-return-air type vacuum membrane dehumidification evaporative cooling air conditioning system; the main significance of this part of work is to clarify which parameters have a more significant impact on the cooling capacity and energy efficiency ratio of the double-return-air type vacuum membrane dehumidification evaporative cooling air conditioning system. The parameters involved include: the vacuum degree on the permeation side, the flow rates of the first, second, third, and fourth airflows, and the water film flow rate.

[0088] Step 4: Use the numerical model verified in Step 2 to design an orthogonal experiment table or a response surface experiment table for the significant parameters in Step 2, and conduct regression analysis through numerical experiment solutions to obtain the regression mathematical relationship between the performance indicators of the vacuum membrane dehumidification evaporative cooling air conditioning system and the significant parameters described in Step 3; the main significance of this part of work is to establish the regression relationship. Since the regression relationship has a relatively fast operation efficiency, it is suitable for optimization solutions.

[0089] Step 5: Use the regression relationship described in Step 4 for optimization solution. When ensuring the optimal performance indicators of the double-return-air type vacuum membrane dehumidification evaporative cooling air conditioning system, obtain the accurate numerical values of the significant parameters for guiding the operation regulation of the vacuum membrane dehumidification evaporative cooling air conditioning system. The main significance of this part of work is to find out the operation regulation parameters that can make the performance indicators of the double-return-air type vacuum membrane dehumidification evaporative cooling air conditioning system optimal and guide the system operation and maintenance.

[0090] The above is only the preferred implementation manner of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system, characterized in that: It includes a fan, a vacuum membrane dehumidifier, a dew point evaporative cooler, air ducts, valves, and air duct connectors; The fan, the vacuum membrane dehumidifier, and the dew point evaporative cooler are sequentially connected in turn by using the air ducts; The air flow at the dry channel air outlet of the dew point evaporative cooler is divided into four streams: the first stream is the supply air flow, which is a low-temperature and dry product air flow; the second stream is the wet channel air flow, which is introduced into the wet channel of the dew point evaporative cooler through the air duct; the third stream is the cooling return air flow, which is introduced into the dry channel inlet of the dew point evaporative cooler through the air duct; the fourth stream is the dehumidification return air flow, which is introduced into the feed side inlet of the vacuum membrane dehumidifier through the air duct; The air ducts are connected to each other through the air duct connectors; A valve is provided on each of the air ducts through which the four air flows pass, and the flow rates of the four air flows are adjusted by adjusting the opening degrees of the four valves.

2. The double-return-air type vacuum membrane dehumidification evaporative cooling air conditioning system according to claim 1, wherein: The vacuum membrane dehumidifier includes a feed side, a permeation side, a water vapor selective permeable membrane, a support layer, a vacuum pump, and a pneumatic pipeline; the water vapor selective permeable membrane covers the support layer, separating the vacuum membrane dehumidifier into two relatively independent spaces, namely the feed side and the permeation side; the vacuum pump is connected to the permeation side through the pneumatic pipeline.

3. The double-return-air type vacuum membrane dehumidification evaporative cooling air conditioning system according to claim 1, characterized in that: The dew point evaporative cooler includes two channels, namely a dry channel and a wet channel; the dry channel and the wet channel are separated by a material with good thermal conductivity but impermeable to air; there is a water film on the inner wall of the wet channel.

4. The double-return-air type vacuum membrane dehumidification evaporation cooling air conditioning system according to claim 1, characterized in that: The material with good thermal conductivity but impermeable to air between the dry channel and the wet channel of the dew point evaporative cooler is an aluminum plate, a copper plate, an aluminum pipe or a copper pipe; the water film on the inner wall of the wet channel is evenly distributed by relying on a hydrophilic thin textile cloth or non-woven fabric.

5. The operation regulation method of the double-return-air type vacuum membrane dehumidification evaporative cooling air conditioning system according to any one of claims 1-4, characterized in that: This method includes the following steps: Step 1: Establish a numerical model of the double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system by using the heat and mass transfer differential equations; Step 2: Conduct experimental tests on the double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system, and verify the numerical model established in Step 1 by using the experimental data; Step 3: Use the numerical model verified in Step 2 to conduct a parameter sensitivity analysis to identify the significant parameters that have an obvious impact on the performance of the double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system; Step 4: Use the numerical model verified in Step 2 to conduct a regression analysis through numerical experiments to obtain the regression mathematical relationship between the performance indexes of the double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system and the significant parameters described in Step 3; Step 5: Use the regression mathematical relationship described in Step 4 to conduct an optimization solution. When ensuring the optimal performance indexes of the double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system, obtain the accurate values of the significant parameters for regulating the operation of the double-return air type vacuum membrane dehumidification evaporative cooling air conditioning system.

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