Variable-pressure micro-channel condensation dehumidification device and regulation and control method thereof

Abstract

The invention provides a variable-pressure micro-channel condensation and dehumidification device and a regulation and control method thereof.The variable-pressure micro-channel condensation and dehumidification device comprises a compressor, a micro-channel dehumidifier, a first gas-liquid separator and an expansion machine, an air inlet pipe is connected with an air inlet of the compressor, and an air outlet of the compressor is connected with an air inlet of the micro-channel dehumidifier; a gas outlet of the micro-channel dehumidifier is connected with an inlet of the first gas-liquid separator, a gas outlet of the first gas-liquid separator is connected with a gas inlet of the expansion machine, and a gas outlet of the expansion machine is connected with the gas outlet pipe. According to the variable-pressure micro-channel condensation dehumidification device and the regulation and control method thereof, additional refrigeration equipment is not needed, and energy consumption is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of air dehumidification, and in particular, relates to a variable pressure microchannel condensation dehumidification device and a control method thereof. Background Art

[0002] Air humidity control plays an important role in civil buildings and industrial processes, and is one of the important factors in achieving indoor comfort conditions. Traditional dehumidification systems, such as air conditioners and dehumidifiers, usually use compressors and evaporators to condense and dehumidify the air during the dehumidification process. However, these traditional devices have problems such as inaccurate temperature and humidity regulation and low energy efficiency. Especially in high humidity and high flow environments, the dehumidification effect and system energy efficiency will be significantly reduced.

[0003] Therefore, improving the energy efficiency of the dehumidification system and making the dehumidification system more flexible and adjustable is currently in urgent need of research. Condensation dehumidification is one of the traditional dehumidification methods. However, at present, atmospheric pressure condensation dehumidification is mainly used, which requires a low-temperature cooling source from a chiller, and also requires reheating to make the air reach the comfortable temperature required by the human body. Therefore, the condensation dehumidification process of wet air at normal pressure will cause energy waste, resulting in increased energy consumption of the dehumidification system. When the environment requires deep dehumidification, the dew point temperature is extremely low, even below 0°C, which may cause frosting of the equipment and low energy efficiency. Summary of the invention

[0004] The present invention provides a variable pressure microchannel condensation dehumidification device and a control method thereof, which does not require additional refrigeration equipment and reduces energy consumption.

[0005] To solve the above technical problems, the embodiments of the present invention adopt the following technical solutions:

[0006] In the first aspect, an embodiment of the present invention provides a variable-pressure microchannel condensation and dehumidification device, including a compressor, a microchannel dehumidifier, a first gas-liquid separator and an expander, wherein an air inlet pipe is connected to the air inlet of the compressor, an air outlet of the compressor is connected to the air inlet of the microchannel dehumidifier, an air outlet of the microchannel dehumidifier is connected to the inlet of the first gas-liquid separator, an air outlet of the first gas-liquid separator is connected to the air inlet of the expander, and an air outlet of the expander is connected to the air outlet pipe.

[0007] As a further improvement of an embodiment of the present invention, it also includes an air-to-air heat exchanger and a second gas-liquid separator. The gas outlet of the first gas-liquid separator is connected to the gas inlet of the expander in the following ways: the gas outlet of the first gas-liquid separator is connected to the first gas inlet of the air-to-air heat exchanger, the first gas outlet of the air-to-air heat exchanger is connected to the inlet of the second gas-liquid separator, and the gas outlet of the second gas-liquid separator is connected to the gas inlet of the expander; the gas outlet of the expander is connected to the gas outlet pipe in the following ways: the gas outlet of the expander is connected to the second gas inlet of the air-to-air heat exchanger, and the second gas outlet of the air-to-air heat exchanger is connected to the gas outlet pipe.

[0008] As a further improvement of an embodiment of the present invention, the microchannel dehumidifier includes a first channel layer and a second channel layer arranged in a stacked manner, and the first channel layer and the second channel layer are both provided with a plurality of microchannels; the inlet of the first channel layer is connected to the air outlet of the compressor as the air inlet of the microchannel dehumidifier, and the outlet of the first channel layer is connected to the inlet of the first gas-liquid separator as the air outlet of the microchannel dehumidifier; the diameter of the microchannel of the first channel layer gradually expands along the air flow direction.

[0009] As a further improvement of the embodiment of the present invention, the cooling medium of the microchannel dehumidifier adopts a natural cold source or is provided by an evaporative cooling tower.

[0010] As a further improvement of the embodiment of the present invention, it also includes an electric motor, the input end of the electric motor is connected to the expander, and the output end of the electric motor is connected to the compressor.

[0011] In a second aspect, an embodiment of the present invention further provides a control method for the variable pressure microchannel condensation dehumidification device provided in the first aspect, comprising the following steps:

[0012] Step 10, establishing a heat and mass transfer model for humid air positive pressure condensation dehumidification;

[0013] Step 20, according to the structural parameters of the microchannel dehumidifier and the physical parameters of the humid air including the pressure of the humid air entering the microchannel dehumidifier, the humid air positive pressure condensation dehumidification heat and mass transfer model is used to calculate the air humidity output by the microchannel dehumidifier under different humid air pressures, and obtain the corresponding relationship between the humid air pressure entering the microchannel dehumidifier and the air humidity output by the microchannel dehumidifier;

[0014] Step 30, based on the correspondence between the humid air pressure entering the microchannel dehumidifier and the air humidity output by the microchannel dehumidifier, obtain a preset humid air pressure range corresponding to the target air humidity, and regulate the compressor so that the humid air pressure entering the microchannel dehumidifier is within the preset humid air pressure range.

[0015] As a further improvement of the embodiment of the present invention, the wet air positive pressure condensation dehumidification heat and mass transfer model includes a single droplet model, a droplet growth model and a channel condensation model;

[0016] The single droplet model is expressed as formula (1) to formula (4):

[0017]

[0018]

[0019] Q ds =4πr d λ w (t ds -t z ) Formula (3)

[0020]

[0021] Where M i represents the mass flux through the Knudsen layer, r i represents the Knudsen layer radius, ρ i represents the Knudsen layer vapor density, R represents the gas constant, t i represents the surface temperature of the Knudsen layer, ρ d represents the droplet density, r d represents the droplet radius, t ds represents the droplet surface temperature; M c represents the mass flux from the continuous region to the Knudsen layer, D v represents the water vapor diffusion coefficient, ρ m represents the density of moist air, ρ v Indicates the vapor density of moist air; Q ds represents the growth of a single droplet to r d The heat transfer flux under w represents the thermal conductivity of water, t z represents the cold wall temperature; M ds represents the growth of a single droplet to r d The mass flux under , L represents the latent heat of condensation per unit time;

[0022] The droplet growth model is expressed as equation (5) to equation (12):

[0023]

[0024] S β =S” β +S"' β Formula (6)

[0025]

[0026]

[0027]

[0028] Y β =Y" β +Y"' β Formula (10)

[0029]

[0030]

[0031] In the formula, q β represents the total heat transfer rate during the droplet growth process, A represents the sum of the cylindrical surface areas of all microchannels in the first channel layer of the microchannel dehumidifier, and q ds represents the heat transfer rate at a certain time corresponding to the droplet radius, τ” β represents the droplet coalescence process time, τ"' β represents the time of droplet sliding down, m represents the total number of droplets; m β represents the total mass transfer rate during the droplet growth process, m ds It represents the mass transfer rate corresponding to the droplet radius at a certain time;

[0032] The channel condensation model is expressed as equation (13) to equation (17):

[0033]

[0034]

[0035]

[0036] q x =K(t m -t w ) Formula (16)

[0037] q i =q x,i +q β,i , i=1,2,…,n Formula (17)

[0038] m i =m β,i Formula (18)

[0039] dQ i =q i dA i Formula (19)

[0040] dM i =m i dA i Formula (20)

[0041]

[0042] t m,i =f(p,h m,i ) Formula (23)

[0043] In the formula, k w represents the convective heat transfer coefficient of the second channel layer, Nu w represents the Nusselt number of cooling water, r a represents the diameter of the microchannel of the second channel layer; k m represents the convection heat transfer coefficient of the first channel layer, Nu m is the Nusselt number of air, λ m represents the thermal conductivity of air, r c represents the average diameter of the microchannels in the first channel layer, r c =(r a +r b ) / 2, r b represents the inlet diameter of the microchannel of the first channel layer; K represents the convective heat transfer coefficient between the wet air and the partition, r g Indicates the thickness of the partition, λ cu Represents the thermal conductivity of copper; q x represents the convective heat transfer rate between the moist air and the partition, t m represents the temperature of moist air, t w Indicates the temperature of cooling water; q i represents the heat transfer rate of the i-th microchannel section, q x,i represents the convective heat transfer rate between the wet air and the partition in the i-th microchannel section, q β,i represents the total heat transfer rate of the droplet growth process in the i-th microchannel segment, m i represents the mass transfer rate of the i-th microchannel segment, m β,i represents the total mass transfer rate of the droplet growth process in the i-th microchannel segment; dQ i represents the heat transfer flux of the i-th microchannel section, dA i represents the cylindrical surface area of ​​the i-th microchannel segment of the first channel layer of the microchannel dehumidifier, dM i represents the mass flux of the i-th microchannel segment; h m,i represents the enthalpy of the wet air at the outlet of the i-th microchannel section, h m,i-1 represents the enthalpy of the wet air at the outlet of the i-1th microchannel section, q m represents the wet air mass flow rate, q a represents the dry air mass flow rate, d m,i represents the moisture content of the wet air at the outlet of the i-th microchannel section, d m,i-1 represents the moisture content of the wet air at the outlet of the i-1th microchannel section, t m,i Represents the temperature of the wet air at the outlet of the i-th microchannel section.

[0044] As a further improvement of the embodiment of the present invention, the step 20 specifically includes:

[0045] Step 201, initializing droplet state parameters;

[0046] Step 202, using an iterative method, the goal is to obtain the same calculation results of equations (1), (2) and (4), and calculate the droplet state parameters; compare the droplet state parameters with the initialized droplet state parameters. If the error condition is not met, the droplet state parameters are reinitialized using a binary search method and step 202 is executed; if the error condition is met, step 203 is executed;

[0047] Step 203, using equations (3) and (4) to calculate the heat transfer flux and mass flux generated by a single droplet; based on the heat transfer flux and mass flux generated by a single droplet, using a droplet growth model to calculate the total heat transfer flux and mass flux of the droplet growth process;

[0048] Step 204, based on the total heat transfer flux and mass flux of the droplet growth process, and the physical property parameters of the wet air, the channel condensation model is used to calculate the air humidity at the outlet of the microchannel dehumidifier under different wet air pressures using a microelement method; the physical property parameters of the wet air include the wet air pressure, wet air temperature, and wet air humidity entering the microchannel dehumidifier;

[0049] Step 205, obtaining the corresponding relationship between the humid air pressure and the air humidity.

[0050] As a further improvement of the embodiment of the present invention, step 203 specifically includes:

[0051] The microchannel of the microchannel dehumidifier is differentiated, and the total heat transfer flux and mass flux of the droplet growth process obtained in step 203 are used as the heat transfer flux and mass flux of the air passing through the first microchannel section in the initial state. Given the humid air pressure, humid air temperature and humid air humidity entering the microchannel dehumidifier, the enthalpy, moisture content and temperature of the air at the outlet of the first microchannel section are calculated using equations (21) to (23); the heat transfer flux and mass flux of the second microchannel section are calculated using equations (13) to (20), and the heat transfer flux and mass flux of the second microchannel section are calculated using equations ( 21) to (23) to calculate the enthalpy, moisture content and temperature of the outlet air of the second microchannel section, and then calculate the heat transfer flux and mass flux of each microchannel section, as well as the enthalpy, moisture content and temperature of the outlet air; the humidity and temperature of the humid air remain unchanged, and the humid air pressure entering the microchannel dehumidifier is re-given, and then calculate the heat transfer flux and mass flux of each microchannel section, as well as the enthalpy, moisture content and temperature of the outlet air; thereby, the air humidity at the outlet of the microchannel dehumidifier under different humid air pressures is obtained.

[0052] As a further improvement of the embodiment of the present invention, the corresponding relationship between the humid air pressure and the air humidity at the air outlet of the microchannel dehumidifier is: when the humid air pressure is 160-300 kPa, the air humidity at the air outlet of the microchannel dehumidifier is 15.6-10.9 g / kg.

[0053] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0054] The present invention provides a variable pressure microchannel condensation and dehumidification device and a control method thereof, which pressurizes the air to increase the dew point temperature, thereby making it easier for water vapor in the air to be condensed into water and separated; reduces the air humidity by physical means, without the need for additional refrigeration equipment, and reduces energy consumption; uses a microchannel dehumidifier to dehumidify air under positive pressure conditions, which can effectively overcome the resistance generated by the flow of humid air, reduce pressure loss, and improve air condensation and dehumidification performance; establishes a humid air positive pressure condensation and dehumidification heat and mass transfer model, monitors the state parameters of the inlet and outlet of the microchannel dehumidifier during the condensation and dehumidification process, obtains the corresponding relationship between the humid air pressure entering the microchannel dehumidifier and the air humidity output by the microchannel dehumidifier, adjusts the pressure according to the humidity demand, and realizes the control of the condensation and dehumidification performance by adjusting the pressure, optimizes the heat and mass transfer process, and further improves the air dehumidification energy efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0056] Figure 1 is a schematic structural diagram of a variable pressure microchannel condensation and dehumidification device according to an embodiment of the present invention;

[0057] Figure 2 yes Figure 1 The structure of the microchannel dehumidifier;

[0058] Figure 3 yes Figure 2 Cross-sectional view of the first channel layer in FIG.

[0059] The figure includes: a compressor 1, a microchannel dehumidifier 2, a first channel layer 21, a second channel layer 22, a first gas-liquid separator 3, an air-to-air heat exchanger 4, a second gas-liquid separator 5, an expander 6, an electric motor 7, an air inlet pipe 8, and an air outlet pipe 9. DETAILED DESCRIPTION

[0060] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings.

[0061] The embodiment of the present invention provides a variable pressure microchannel condensation dehumidification device, such as Figure 1 As shown, it includes a compressor 1, a microchannel dehumidifier 2, a first gas-liquid separator 3 and an expander 6, the air inlet pipe 8 is connected to the air inlet of the compressor 1, the air outlet of the compressor 1 is connected to the air inlet of the microchannel dehumidifier 2, the air outlet of the microchannel dehumidifier 2 is connected to the inlet of the first gas-liquid separator 3, the air outlet of the first gas-liquid separator 3 is connected to the air inlet of the expander 6, and the air outlet of the expander 6 is connected to the air outlet pipe 9.

[0062] When the above-mentioned variable pressure microchannel condensation and dehumidification device is working, the humid air in the environment enters the compressor 1 through the air inlet pipe 8 for compression and pressure boosting. The pressurized humid air enters the microchannel dehumidifier 2 for condensation heat exchange to reduce the temperature of the air. When the air temperature drops below the dew point temperature, the water vapor in the air condenses into water, and then enters the first gas-liquid separator 3 for gas-liquid separation to achieve condensation and dehumidification. The dehumidified air enters the expander 6 for pressure reduction treatment, and then is output to the environment through the air outlet pipe 9.

[0063] The variable pressure microchannel condensation and dehumidification device of this embodiment pressurizes the air to increase the dew point temperature, thereby making it easier for water vapor in the air to be condensed into water and separated; it reduces the air humidity by physical means, without the need for additional refrigeration equipment, thereby reducing energy consumption; and uses a microchannel dehumidifier to dehumidify the air under positive pressure conditions, which can effectively overcome the resistance caused by the flow of humid air, reduce pressure loss, and improve air condensation and dehumidification performance.

[0064] As a preferred example, Figure 1 As shown, the variable pressure microchannel condensation dehumidification device of this embodiment also includes an air-to-air heat exchanger 4 and a second gas-liquid separator 5. The gas outlet of the first gas-liquid separator 3 is connected to the gas inlet of the expander 6 in the following manner: the gas outlet of the first gas-liquid separator 3 is connected to the first gas inlet of the air-to-air heat exchanger 4, the first gas outlet of the air-to-air heat exchanger 4 is connected to the inlet of the second gas-liquid separator 5, and the gas outlet of the second gas-liquid separator 5 is connected to the gas inlet of the expander 6. The gas outlet of the expander 6 is connected to the gas outlet pipe in the following manner: the gas outlet of the expander 6 is connected to the second gas inlet of the air-to-air heat exchanger 4, and the second gas outlet of the air-to-air heat exchanger 4 is connected to the gas outlet pipe.

[0065] During operation, the humid air in the environment enters the compressor 1 through the air inlet pipe 8 for compression and pressure boosting. The pressurized humid air enters the microchannel dehumidifier 2 for condensation heat exchange to reduce the temperature of the air. When the air temperature drops below the dew point temperature, the water vapor in the air condenses into water and then enters the first gas-liquid separator 3 for gas-liquid separation. The air after removing part of the water vapor enters the air-to-air heat exchanger 4 for condensation heat exchange to further reduce the temperature of the air. The water vapor in the air condenses into water and then enters the second gas-liquid separator 5 for gas-liquid separation to achieve condensation and dehumidification. The dehumidified air enters the expander 6 for pressure reduction treatment, and then enters the air-to-air heat exchanger 4 as a cold source, and finally output to the environment through the air outlet pipe 9.

[0066] This embodiment utilizes an air-to-air heat exchanger to re-condense and dehumidify the air, further improving the dehumidification effect to meet the moisture content requirement, and on the other hand, reheat the dehumidified and depressurized air and output it to the environment.

[0067] As a preferred example, Figure 2 As shown, the microchannel dehumidifier 2 includes a first channel layer 21 and a second channel layer 22 which are stacked, and the first channel layer 21 and the second channel layer 22 are both provided with a plurality of microchannels. The inlet of the first channel layer 21 is connected to the outlet of the compressor 1 as the air inlet of the microchannel dehumidifier 2, and the outlet of the first channel layer 21 is connected to the inlet of the first gas-liquid separator 3 as the air outlet of the microchannel dehumidifier 2. The first channel layer is used to pass pressurized humid air, and the second channel layer is used to pass cooling medium. The humid air and the cooling medium perform countercurrent heat exchange through the partition between the first channel layer and the second channel layer. Preferably, the cross-sections of all microchannels are circular. In microchannels with circular cross-sections, the air flows more evenly and smoothly in the microchannels, reducing energy loss; the wall surface of the microchannels with circular cross-sections is arc-shaped, and the convective heat exchange contact area is relatively more uniform, which can more effectively promote heat exchange, thereby improving the overall condensation and dehumidification efficiency. As shown Figure 3 As shown, the diameter of the microchannels of the first channel layer 21 gradually increases along the air flow direction, and the diameter of the microchannels of the second channel layer 22 remains unchanged along the cooling medium flow direction. Preferably, the outlet diameter of the microchannels of the first channel layer 21 is equal to the outlet diameter of the microchannels of the second channel layer 22. That is, the inlet diameter of the microchannels of the first channel layer 21 is r b , the outlet diameter of the microchannel of the first channel layer 21 is r a , the diameter of the microchannel of the second channel layer 22 is r a The diameter of the microchannels of the second channel layer is the same as the maximum diameter of the microchannels of the first channel layer, so that the heat exchange area of ​​the cooling medium entering the microchannel is increased, the flow rate of the cooling medium is increased, and the condensation and dehumidification effect is enhanced. Preferably, the microchannel dehumidifier is made of copper.

[0068] In the above embodiment, the diameter of the microchannel of the first channel layer 21 gradually increases along the air flow direction, that is, the gradual expansion channel is adopted, which can slow down the rapid change of air flow rate, make the air flow more uniform and stable, reduce flow resistance, and reduce pressure loss. At the same time, the contact time between air and the partition is increased, and the condensation and dehumidification performance of the microchannel dehumidifier is improved.

[0069] Preferably, the cooling medium of the microchannel dehumidifier 2 is provided by a natural cold source or an evaporative cooling tower. No traditional mechanical refrigeration system is required, which reduces energy consumption and ensures high cooling efficiency. The cooling medium is preferably cooling water.

[0070] As a preferred example, the variable pressure microchannel condensation dehumidification device of this embodiment further includes a motor 7, the input end of the motor 7 is connected to the expander 6, and the output end of the motor 7 is connected to the compressor 1. In this embodiment, the expander reduces the pressure of the dehumidified air and provides part of the energy for the operation of the compressor through the motor.

[0071] The embodiment of the present invention also provides a control method of a variable pressure microchannel condensation dehumidification device, comprising the following steps:

[0072] Step 10, establishing a heat and mass transfer model for humid air positive pressure condensation dehumidification.

[0073] Step 20, based on the structural parameters of the microchannel dehumidifier and the physical properties of the humid air including the pressure of the humid air entering the microchannel dehumidifier, a humid air positive pressure condensation dehumidification heat and mass transfer model is used to calculate the air humidity output by the microchannel dehumidifier under different humid air pressures, and obtain the corresponding relationship between the humid air pressure entering the microchannel dehumidifier and the air humidity output by the microchannel dehumidifier.

[0074] Step 30, based on the correspondence between the humid air pressure entering the microchannel dehumidifier and the air humidity output by the microchannel dehumidifier, obtain a preset humid air pressure range corresponding to the target air humidity, and regulate the compressor so that the humid air pressure entering the microchannel dehumidifier is within the preset humid air pressure range.

[0075] The control method of the variable pressure microchannel condensation dehumidification device of the present embodiment establishes a humid air positive pressure condensation dehumidification heat and mass transfer model, calculates the air humidity output by the microchannel dehumidifier during the condensation and dehumidification process according to the structural parameters of the microchannel dehumidifier and the physical properties of the humid air entering the microchannel dehumidifier, obtains the corresponding relationship between the pressure of the humid air entering the microchannel dehumidifier and the air humidity output by the microchannel dehumidifier, adjusts the pressure according to the humidity demand, and realizes the control of the condensation and dehumidification performance by adjusting the pressure, optimizes the heat and mass transfer process, and further improves the air dehumidification energy efficiency.

[0076] As a preferred example, the heat and mass transfer model of humid air positive pressure condensation dehumidification includes a single droplet model, a droplet growth model and a channel condensation model.

[0077] In the single droplet model, there are three regions, namely the Knudsen layer and the continuous region inside the droplet and the vapor space around the droplet.

[0078] For the Knudsen layer, the free molecular dynamics theory is applied to calculate the mass flux through the Knudsen layer, that is, formula (1):

[0079]

[0080] Where M i represents the mass flux through the Knudsen layer, r i represents the Knudsen layer radius, ρ i represents the vapor density of the Knudsen layer, R represents the gas constant, and t i represents the surface temperature of the Knudsen layer, ρ d represents the droplet density, r d represents the droplet radius, t ds Represents the droplet surface temperature.

[0081] For the continuous region, the mass flux from the continuous region to the Knudsen layer is calculated using continuum fluid mechanics, that is, formula (2):

[0082]

[0083] Where M c represents the mass flux from the continuous region to the Knudsen layer, D v represents the water vapor diffusion coefficient, ρ m represents the density of moist air, ρ v Indicates the vapor density of moist air.

[0084] For the inside of the droplet, the heat conduction law is used to calculate the heat transfer flux when the droplet grows to a certain transient radius when the wet air condenses in a droplet shape, that is, formula (3):

[0085] Q ds =4πr d λ w (t ds -t z ) Formula (3)

[0086] In the formula, Q ds represents the growth of a single droplet to r d The heat transfer flux under w represents the thermal conductivity of water, t z represents the cold wall temperature.

[0087] Formula (4) is used to calculate the mass flux of the droplets growing to a certain transient radius when the wet air undergoes droplet condensation:

[0088]

[0089] Where M ds represents the growth of a single droplet to r d The mass flux under the condition of condensation is L, and L represents the latent heat of condensation per unit time.

[0090] According to the law of conservation of mass, the mass fluxes in the three regions are equal.

[0091] In the droplet growth model, the droplet growth process includes the droplet nucleation to coalescence, the droplet coalescence process, and the droplet sliding process. Since the wet air condensation has not reached a dynamic stable state from the droplet nucleation to coalescence, the heat transfer flux of this process is not included in the total heat transfer flux, and the mass flux is not included in the total mass flux.

[0092] Therefore, the total heat transfer rate of the droplet growth process is calculated using formula (5):

[0093]

[0094] S β =S” β +S"' β Formula (6)

[0095]

[0096]

[0097] In the formula, q β represents the total heat transfer rate during the droplet growth process, A represents the sum of the cylindrical surface areas of all microchannels in the first channel layer of the microchannel dehumidifier; q ds The heat transfer rate corresponding to the droplet radius at a certain time is expressed by formula (3): d The heat transfer under the condition is divided by the droplet condensation area 4πr d 2 Get the heat transfer rate corresponding to the droplet radius at a certain time; τ" β represents the droplet coalescence process time, τ"' β It represents the time of droplet sliding down, and m represents the total number of droplets.

[0098] The total mass transfer rate of the droplet growth process is calculated using formula (8):

[0099]

[0100] Y β =Y" β+Y"' β Formula (10)

[0101]

[0102] In the formula, m β represents the total mass transfer rate during the droplet growth process; m ds represents the mass transfer rate at a certain time corresponding to the droplet radius. The mass flux at a certain time corresponding to the droplet radius is calculated by formula (4) and then divided by the droplet condensation area 4πr d 2 The mass transfer rate corresponding to the droplet radius at a certain time is obtained.

[0103] For example Figure 2 The microchannel dehumidifier shown establishes a channel condensation model, uses the infinitesimal method to divide each microchannel into n microchannel segments, and calculates the heat transfer flux and mass flux of each microchannel segment. Preferably, n is in the range of 100 to 20000. More preferably, n is 1000.

[0104] It is necessary to consider the convective sensible heat, that is, the convective heat transfer between the moist air and the partition.

[0105] Specifically, the convective heat transfer coefficient on the cooling water side is calculated using formula (13):

[0106]

[0107] In the formula, k w represents the convective heat transfer coefficient of the second channel layer, Nu w represents the Nusselt number of cooling water, λ w represents the thermal conductivity of water, r a represents the diameter of the microchannel of the second channel layer.

[0108] The air side convection heat transfer coefficient is calculated using formula (14):

[0109]

[0110] In the formula, k m represents the convection heat transfer coefficient of the first channel layer, Nu m is the Nusselt number of air, λ m represents the thermal conductivity of air, r c represents the average diameter of the microchannels in the first channel layer, r c =(r a +r b ) / 2, r b represents the inlet diameter of the microchannel of the first channel layer.

[0111] The convection coefficient between the moist air and the partition is calculated using formula (15):

[0112]

[0113] In the formula, K represents the convective heat transfer coefficient between the moist air and the partition, r g Indicates the thickness of the partition, λ cu Represents the thermal conductivity of copper.

[0114] The convective heat transfer rate between air and the partition is calculated using formula (16):

[0115] q x =K(t m -t w ) Formula (16)

[0116] In the formula, q x represents the convective heat transfer rate between the moist air and the partition, t m represents the temperature of moist air, t w Indicates the temperature of cooling water.

[0117] The heat transfer rate of the i-th microchannel section is calculated using formula (17):

[0118] q i =q x,i +q β,i , i=1,2,…,n Formula (17)

[0119] In the formula, q i represents the heat transfer rate of the i-th microchannel section, q x,i represents the convective heat transfer rate between the wet air and the partition in the i-th microchannel section, q β,i Represents the total heat transfer rate during the droplet growth process in the i-th microchannel section.

[0120] The mass transfer rate of the i-th microchannel section is calculated using formula (18):

[0121] m i =m β,i Formula (18)

[0122] In the formula, m i represents the mass transfer rate of the i-th microchannel segment, m β,i Represents the total mass transfer rate during the droplet growth process in the i-th microchannel segment.

[0123] The heat transfer flux of the i-th microchannel section is calculated using formula (19):

[0124] dQ i =q i dA i Formula (19)

[0125] Where, dQ irepresents the heat transfer flux of the i-th microchannel section, dA i Represents the cylindrical surface area of ​​the i-th microchannel segment of the first channel layer of the microchannel dehumidifier.

[0126] The mass flux of the i-th microchannel section is calculated using formula (20):

[0127] dM i =m i dA i Formula (20)

[0128] Where, dM i represents the mass flux of the i-th microchannel segment.

[0129] The air state change process is calculated using equations (21) to (23):

[0130]

[0131]

[0132] t m,i =f(p,h m,i ) Formula (23)

[0133] In the formula, h m,i represents the enthalpy of the wet air at the outlet of the i-th microchannel section, h m,i-1 represents the enthalpy of the wet air at the outlet of the i-1th microchannel section, q m represents the wet air mass flow rate, q a represents the dry air mass flow rate, d m,i represents the moisture content of the wet air at the outlet of the i-th microchannel section, d m,i-1 represents the moisture content of the wet air at the outlet of the i-1th microchannel section, t m,i It represents the temperature of the wet air at the outlet of the i-th microchannel section, which has a functional relationship with the pressure and enthalpy of the wet air. The temperature of the wet air at the outlet can be obtained according to the pressure and enthalpy of the wet air.

[0134] As a preferred example, step 20 specifically includes:

[0135] Step 201, initializing droplet state parameters.

[0136] Step 202, an iterative method is used to obtain the droplet state parameters by making the mass fluxes of the three regions in the single droplet model equal, i.e., the calculation results of equations (1), (2) and (4) are the same. The droplet state parameters include the droplet surface temperature t ds , Knudsen layer surface temperature t i and the Knudsen layer surface pressure P i .

[0137] The droplet state parameters are compared with the initialized droplet state parameters. If the error condition is not satisfied, the droplet state parameters are reinitialized using a binary method, and step 202 is performed until the error condition is satisfied. If the error condition is satisfied, step 203 is performed.

[0138] Step 203, using equations (3) and (4) to calculate the heat transfer flux and mass flux generated by a single droplet. Based on the heat transfer flux and mass flux generated by a single droplet, the total heat transfer flux and mass flux of the droplet growth process are calculated using the droplet growth model, i.e., equations (5) to (12).

[0139] Step 204, based on the total heat transfer flux and mass flux of the droplet growth process and the physical parameters of the wet air, the channel condensation model is used to calculate the air humidity at the outlet of the microchannel dehumidifier under different wet air pressures using a microelement method. The physical parameters of the wet air include the wet air pressure, wet air humidity and wet air temperature entering the microchannel dehumidifier.

[0140] Step 205, obtaining the corresponding relationship between the humid air pressure and the air humidity.

[0141] Wherein, step 204 specifically includes:

[0142] The microchannel of the microchannel dehumidifier is differentiated, and the total heat transfer flux and mass flux of the droplet growth process obtained in step 203 are used as the heat transfer flux and mass flux of the air passing through the first microchannel section in the initial state. The humid air pressure, humid air humidity and humid air temperature entering the microchannel dehumidifier are given, and the enthalpy, moisture content and temperature of the air at the outlet of the first microchannel section are calculated using equations (21) to (23). The heat transfer flux and mass flux of the second microchannel section are calculated using equations (13) to (20), and the enthalpy, moisture content and temperature of the air at the outlet of the second microchannel section are calculated using equations (21) to (23). The heat transfer flux and mass flux of each microchannel section, as well as the enthalpy, moisture content and temperature of the outlet air are calculated in turn. The humidity and temperature of the humid air remain unchanged, and the humid air pressure entering the microchannel dehumidifier is reset. The heat transfer flux and mass flux of each microchannel section, as well as the enthalpy, moisture content and temperature of the outlet air are calculated in turn. Thus, the air humidity at the outlet of the microchannel dehumidifier under different humid air pressures is obtained.

[0143] Preferably, the humidity of the wet air is set to 100%, the temperature of the wet air is 27°C, the temperature of the cooling water is 26°C, the range of the wet air pressure is 160-300kPa, and the corresponding relationship between the wet air pressure and the air humidity at the outlet of the microchannel dehumidifier is obtained as follows: when the wet air pressure is 160-300kPa, the air humidity at the outlet of the microchannel dehumidifier is 15.6-10.9g / kg. This embodiment obtains the above-mentioned preferred corresponding relationship, and under positive pressure conditions, when the air pressure increases, the moisture content of the outlet air decreases and the dehumidification efficiency is improved. In step 30, for example, if the target air humidity is 11g / kg, the compressor is adjusted so that the wet air pressure output by the compressor is 160-300kPa, and after passing through the microchannel dehumidifier, the air humidity will be close to the target air humidity.

[0144] The humid air positive pressure condensation dehumidification heat and mass transfer model established in the embodiment of the present invention includes a single droplet model, a droplet growth model and a channel condensation model. It is analyzed from the perspective of bead condensation of humid air, and the influence of non-condensable gases in the air on droplet condensation is considered. It is established according to the structure of the microchannel dehumidifier. The corresponding relationship between the humid air pressure entering the microchannel dehumidifier and the air humidity output by the microchannel dehumidifier can be calculated according to different air conditions (humid air temperature and humid air humidity) and the structural dimensions of the microchannel dehumidifier, so that the pressure can be adjusted according to the target air humidity, making the dehumidification process more accurate and flexible.

[0145] The basic principles, main features and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above specific embodiments, and the descriptions in the above specific embodiments and the specification are only for further illustrating the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed for protection.

Claims

1. A variable pressure microchannel condensation dehumidification device, characterized in that: The invention comprises a compressor (1), a microchannel dehumidifier (2), a first gas-liquid separator (3) and an expander (6); an air inlet pipe is connected to the air inlet of the compressor (1); an air outlet of the compressor (1) is connected to the air inlet of the microchannel dehumidifier (2); an air outlet of the microchannel dehumidifier (2) is connected to the inlet of the first gas-liquid separator (3); an air outlet of the first gas-liquid separator (3) is connected to the air inlet of the expander (6); and an air outlet of the expander (6) is connected to the air outlet pipe.

2. The variable pressure microchannel condensation dehumidification device according to claim 1, characterized in that: It also includes an air-to-air heat exchanger (4) and a second gas-liquid separator (5); the gas outlet of the first gas-liquid separator (3) is connected to the gas inlet of the expander (6) in the following manner: the gas outlet of the first gas-liquid separator (3) is connected to the first gas inlet of the air-to-air heat exchanger (4), the first gas outlet of the air-to-air heat exchanger (4) is connected to the inlet of the second gas-liquid separator (5), and the gas outlet of the second gas-liquid separator (5) is connected to the gas inlet of the expander (6); the gas outlet of the expander (6) is connected to the gas outlet pipe in the following manner: the gas outlet of the expander (6) is connected to the second gas inlet of the air-to-air heat exchanger (4), and the second gas outlet of the air-to-air heat exchanger (4) is connected to the gas outlet pipe.

3. The variable pressure microchannel condensation dehumidification device according to claim 1, characterized in that: The microchannel dehumidifier (2) comprises a first channel layer (21) and a second channel layer (22) which are stacked, and the first channel layer (21) and the second channel layer (22) are both provided with a plurality of microchannels; the inlet of the first channel layer (21) is connected to the air outlet of the compressor (1) as the air inlet of the microchannel dehumidifier (2), and the outlet of the first channel layer (21) is connected to the inlet of the first gas-liquid separator (3) as the air outlet of the microchannel dehumidifier (2); and the diameter of the microchannel of the first channel layer (21) gradually increases along the air flow direction.

4. The variable pressure microchannel condensation dehumidification device according to claim 1, characterized in that: The cooling medium of the microchannel dehumidifier (2) is provided by a natural cooling source or an evaporative cooling tower.

5. The variable pressure microchannel condensation dehumidification device according to claim 1, characterized in that: It also comprises an electric motor (7), the input end of the electric motor (7) is connected to the expander (6), and the output end of the electric motor (7) is connected to the compressor (1).

6. A control method for a variable pressure microchannel condensation dehumidification device according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 10, establishing a heat and mass transfer model for humid air positive pressure condensation dehumidification; Step 20, based on the structural parameters of the microchannel dehumidifier (2) and the physical parameters of the humid air including the pressure of the humid air entering the microchannel dehumidifier (2), the humid air positive pressure condensation dehumidification heat and mass transfer model is used to calculate the air humidity output by the microchannel dehumidifier (2) under different humid air pressures, and obtain the corresponding relationship between the pressure of the humid air entering the microchannel dehumidifier (2) and the air humidity output by the microchannel dehumidifier (2); Step 30, based on the correspondence between the pressure of the humid air entering the microchannel dehumidifier (2) and the air humidity output by the microchannel dehumidifier (2), a preset humid air pressure range corresponding to the target air humidity is obtained, and the compressor is regulated so that the pressure of the humid air entering the microchannel dehumidifier (2) is within the preset humid air pressure range.

7. The control method according to claim 1, characterized in that: The wet air positive pressure condensation dehumidification heat and mass transfer model includes a single droplet model, a droplet growth model and a channel condensation model; The single droplet model is expressed as formula (1) to formula (4): Q ds = 4πr d λ w (t ds - t z ) Equation (3) Where M i represents the mass flux through the Knudsen layer, r i represents the Knudsen layer radius, ρ i represents the vapor density of the Knudsen layer, R represents the gas constant, and t i represents the surface temperature of the Knudsen layer, ρ d represents the droplet density, r d represents the droplet radius, t ds represents the droplet surface temperature; M c represents the mass flux from the continuous region to the Knudsen layer, D v represents the water vapor diffusion coefficient, ρ m represents the density of moist air, ρ v Indicates the vapor density of moist air; Q ds represents the growth of a single droplet to r d The heat transfer flux under w represents the thermal conductivity of water, t z represents the cold wall temperature; M ds represents the growth of a single droplet to r d The mass flux under , L represents the latent heat of condensation per unit time; The droplet growth model is expressed as equation (5) to equation (12): S β =S” β +S"' β Formula (6) Y β = Y” β + Y”' β Equation (10) In the formula, q β represents the total heat transfer rate during the droplet growth process, A represents the sum of the cylindrical surface areas of all microchannels in the first channel layer of the microchannel dehumidifier, and q ds represents the heat transfer rate at a certain time corresponding to the droplet radius, τ” β represents the droplet coalescence process time, τ"' β represents the time of droplet sliding down, m represents the total number of droplets; m β represents the total mass transfer rate during the droplet growth process, m ds It represents the mass transfer rate corresponding to the droplet radius at a certain time; The channel condensation model is expressed as equation (13) to equation (17): q x =K(t m -t w ) Formula (16) q i =q x,i +q β,i , i = 1, 2, ..., n Equation (17) m i =m β,i Formula (18) dQ i =q i Yes i formula(19) dM i =m i Yes i formula(20) t m,i =f(p,h m,i ) Formula (23) In the formula, k w represents the convective heat transfer coefficient of the second channel layer, Nu w represents the Nusselt number of cooling water, r a represents the diameter of the microchannel of the second channel layer; k m represents the convection heat transfer coefficient of the first channel layer, Nu m is the Nusselt number of air, λ m represents the thermal conductivity of air, r c represents the average diameter of the microchannels in the first channel layer, r c =(r a +r b ) / 2, r b represents the inlet diameter of the microchannel of the first channel layer; K represents the convective heat transfer coefficient between the wet air and the partition, r g Indicates the thickness of the partition, λ cu Represents the thermal conductivity of copper; q x represents the convective heat transfer rate between the moist air and the partition, t m represents the temperature of moist air, t w Indicates the temperature of cooling water; q i represents the heat transfer rate of the i-th microchannel section, q x,i represents the convective heat transfer rate between the wet air and the partition in the i-th microchannel section, q β,i represents the total heat transfer rate of the droplet growth process in the i-th microchannel segment, m i represents the mass transfer rate of the i-th microchannel segment, m β,i represents the total mass transfer rate of the droplet growth process in the i-th microchannel segment; dQ i represents the heat transfer flux of the i-th microchannel section, dA i represents the cylindrical surface area of ​​the i-th microchannel segment of the first channel layer of the microchannel dehumidifier, dM i represents the mass flux of the i-th microchannel segment; h m,i represents the enthalpy of the wet air at the outlet of the i-th microchannel section, h m,i-1 represents the enthalpy of the wet air at the outlet of the i-1th microchannel section, q m represents the wet air mass flow rate, q a represents the dry air mass flow rate, d m,i represents the moisture content of the wet air at the outlet of the i-th microchannel section, d m,i-1 represents the moisture content of the wet air at the outlet of the i-1th microchannel section, t m,i Represents the temperature of the wet air at the outlet of the i-th microchannel section.

8. The control method according to claim 7, characterized in that: The step 20 specifically includes: Step 201, initializing droplet state parameters; Step 202, using an iterative method, the goal is to obtain the same calculation results of equations (1), (2) and (4), and calculate the droplet state parameters; compare the droplet state parameters with the initialized droplet state parameters. If the error condition is not met, the droplet state parameters are reinitialized using a binary search method and step 202 is executed; if the error condition is met, step 203 is executed; Step 203, using equations (3) and (4) to calculate the heat transfer flux and mass flux generated by a single droplet; based on the heat transfer flux and mass flux generated by a single droplet, using a droplet growth model to calculate the total heat transfer flux and mass flux of the droplet growth process; Step 204, based on the total heat transfer flux and mass flux of the droplet growth process, and the physical property parameters of the wet air, the channel condensation model is used to calculate the air humidity at the outlet of the microchannel dehumidifier under different wet air pressures using a microelement method; the physical property parameters of the wet air include the pressure of the wet air entering the microchannel dehumidifier (2), the wet air temperature, and the wet air humidity; Step 205, obtaining the corresponding relationship between the humid air pressure and the air humidity.

9. The control method according to claim 8, characterized in that: The step 203 specifically includes: The microchannel of the microchannel dehumidifier is differentiated, and the total heat transfer flux and mass flux of the droplet growth process obtained in step 203 are used as the heat transfer flux and mass flux of the air passing through the first microchannel section in the initial state. Given the humid air pressure, humid air temperature and humid air humidity entering the microchannel dehumidifier (2), the enthalpy, moisture content and temperature of the air at the outlet of the first microchannel section are calculated using equations (21) to (23); the heat transfer flux and mass flux of the second microchannel section are calculated using equations (13) to (20), and the heat transfer flux and mass flux of the second microchannel section are calculated using equations ( 21) to (23) to calculate the enthalpy, moisture content and temperature of the outlet air of the second microchannel section, and then calculate the heat transfer flux and mass flux of each microchannel section, as well as the enthalpy, moisture content and temperature of the outlet air; the humidity and temperature of the humid air remain unchanged, and the humid air pressure entering the microchannel dehumidifier (2) is re-given, and the heat transfer flux and mass flux of each microchannel section, as well as the enthalpy, moisture content and temperature of the outlet air are calculated in turn; thereby, the air humidity at the outlet of the microchannel dehumidifier under different humid air pressures is obtained.

10. The control method according to claim 8, characterized in that: The corresponding relationship between the humid air pressure and the air humidity at the air outlet of the microchannel dehumidifier is: when the humid air pressure is 160-300 kPa, the air humidity at the air outlet of the microchannel dehumidifier is 15.6-10.9 g / kg.

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